Earbuds, Equalization and Headphones.

by Michael Hoffman

Editor: This page is updated regularly. Please continue to correspond with Michael Hoffman or send new postings to the HeadWize Webmaster. For questions or comments, please visit the HeadWize Discussion Forums.

Contents

  • The Potential of Earbuds
    • My favorite earbud model
    • Headphone Sites
  • Sony Earbuds
    • Table of Sony Earbuds
    • Sony Low-End Earbuds versus 868
    • Sony Low-End Earbuds (807, 817, 827, 837)
    • Sony 238 Earbuds
    • Sony 868 Earbuds
    • Sony 888 Earbuds
    • Stock Earbuds for Sony R3 MiniDisc Recorder
    • Stock Earbuds for Sony E3 MiniDisc Player
    • Sony MDR-E464 earbuds
    • Sony NC10 Noise Cancelling Headphones
  • Other Brands of Earbuds
    • Etymotics – The Ultimate Earbuds
    • Stax earbud electrostatic in-ear headphones
    • Sennheiser Earbuds
    • Sharp Stock Earbud
    • Headphones for Sharp 311
    • Aiwa
    • Koss
    • Kenwood
    • Radio Shack
  • Headphone Tips and Ideas
    • Breaking-In Earbuds
    • Matching Megabass and Earbud Response
    • Equalizing Headphones, Built-In EQ Compensation
    • Defining Smoothness and Balance in Terms of Frequency Response
    • Cushions Increase Bass
    • Coupling with the Ear Canal
    • Packaging
    • Testing Headphones
    • Headphone Extension Cables
    • Equalized-crossfeed to simulate speakers
  • Non-Earbud Headphones
    • Vertical Headphones
    • JVC HA-D700, 990
    • Grado 60
    • Denon 950
    • Denon AH-D210 Headphones
    • Sennheiser 580
    • AKG 240
    • AKG 270
    • Radio Shack Pro-25
    • Koss KSC/35
    • Koss Porta Pro Jr.
    • Koss Porta Pro
    • Sony MDR-D65
    • Sony StreetSound Headphones
    • Sony R11/33/55/77 portable headphones

The Potential of Earbuds

There is great disagreement about:

  • Whether earbuds could potentially sound good, given their small size.
  • Whether any actual earbuds sound good, or whether the whole idea needs further development.
  • Which earbuds sound good and which sound bad.
  • Which of the expensive ($40-$80) earbuds sound so good that the extra cost is justified.

After testing many headphones and earbuds and applying my extensive experience tweaking equalizers, I think that earbuds actually have the potential to sound even *better* than standard headphones. In any case, all headphones and earbuds need a new approach: a calibrated equalization curve built into the player, to yield flat response. Megabass is a step toward such a compensation curve.

Like the Etymotics, earbuds have the potential to have smoother response than even the best popular standard headphones, such as the Sennheiser 580’s. I’ve dialed in some truly vibrant, open sound using equalization together with $10 earbuds. It is easy and straightforward to equalize earbuds; just do anti-rolloff to a greater or lesser degree, and leave the rest flat; there aren’t mysterious jags hidden along the entire spectrum that need unique shapes of compensation. I’d rather trust my ears than the common assumption that earbuds are inferior. If the conditions are right and the appropriate, ordinary EQ compensations are made, earbuds can be superior, rather than inferior, to good standard headphones. It’s simply a matter of starting with a decent earbud driver, and providing the inverse of the earbud driver’s frequency response.

If someone shows me a measured response curve of an earbud and it’s rough and jagged, I will change my view somewhat, but in any case, I think that eq-compensated earbuds at least *can sound* unusually smooth and natural. Players need more fancy curves to compensate for specific earbud models.

“Though I like the R3 stock earbuds even better than the 888’s, I can’t stop seeking for even better sound, as I believe it can be a lot better. If I press against an earbud I get very powerful bass, so it is possible. I will keep on looking, and if I find something interesting I will let you know. Please let me know your findings on this matter.” (from a private email to me)

Some people haven’t been lucky and haven’t heard the one or two models that are really good. No wonder they think earbuds are a poor packaging and sound poor. I was starting to suspect that *some* Sony stock earbuds (included with the player) sound great, and some sound lousy.

My favorite earbud model

Of the earbuds I’ve tested, I recommend the low-end Sony models such as the 821 (MDR-E821LP): very inexpensive, wide-response, no humps, good coupling, case included. Their only flaw: a little too much high-treble, so that cymbals tend to overshadow the rest of the treble. People have complained about certain earbuds having too much treble; they might be referring to this. If you want less high-treble, choose from the higher-end units (8n8 such as 848). Some people claim that the high-end such as 888 have a lot of “treble”, but I know that my 868 has extra mid-treble with less high-treble, compared to my 817 [821] or 807V, and the other high-end units I demo’d in a store had the same overall treble sound as the 868: that is, less high-treble than the 817 [821]. The high-end have too much sibilant mid-treble at first; several people reported that this “smoothes out” after break-in. After a reasonable time, my 868’s still sound like they have a lot of mid-treble with much less high-treble than the 817s [821’s].

I don’t listen to my 238L’s — not enough mid-treble, not enough high-treble. I tend to alternate between 817 (now redesigned as the MDR-E821LP) and 868.

Headphone manufacturers should stop shooting for the impossible goal of flat headphone response, and think instead in terms of *systems*, combining calibrated eq, good drivers, and cross-channel delay.

Headphone Sites

Headwize.com – Headphones resource site

Headphone.com – lots of info about headphones

Official Sony headphones product pages

  • Earbuds
  • Lightweight
  • Digital Reference
  • Noise cancelling
  • Sport
  • Street style
  • Vertical

Sony site map

Sony phone numbers

(800) 222-7669 – Sony parts and product info

Sony Earbuds

Table of Sony Earbuds

Detailed Table of Sony Earbuds (Word 2.0)

There are many Sony earbud models, but there are only 4 or 5 unique drivers/housings.

_____________________________________________________________

MDR-E811LP:

hoff1.gif

MDR-E821LP: [I have these]

hoff2.gif

MDR-E821V: [I have the predecessor, 817V]

hoff3.gif

_____________________________________________________________

MDR-E848LP:

hoff4.gif

[Where is the MDR-E868LP?] [I have these]

MDR-E888LP:

hoff5.gif

_____________________________________________________________

MDR-E228LP:

hoff6.gif

MDR-E238LP: [I have these]

hoff7.gif

MDR-E268LP:

hoff8.gif

_____________________________________________________________

Sony Low-End Earbuds versus the 8n8 models

These two sound different, but it’s pretty arbitrary which one you pick. Overall, they sound equally good or equally flawed, as far as frequency response; the humps and dips are merely in different places in the spectrum. Neither of them has a major hump or dip, aside from bass rolloff. They both have a fairly good coupling with the ear canal. Given that their flaws are equivalent, just shifted to different places, I’d have to recommend Sony’s low-end earbuds, based on price.

I did a demo of the ~$10 817 [821] (same driver and housing as the other 8n7’s) against the 868 ($40, almost the most expensive). The 868’s have been broken in for several days, 24 hours (in case it makes any difference). I wish I had a simple response curve for these instead of trying to hear the curve. But I’m sure of the following major differences, analyzed in terms of 9 divisions of the frequency response curve (I wish eq’s had 9 bands, not 10 — easier to label, such as “low-midrange”). (See Michael Schuster’s note in the Aiwa section below – he dislikes the low-end Sony’s.)

The low-end models overemphasize high-treble, and have a lot of mid-bass, and a fair amount of low-bass:
low-bass: less
mid-bass: more
mid-treble: less
upper-treble: more

The 8n8 models have more mid-treble, but less high-treble; and has a little less mid-bass with a little more low-bass:
low-bass: more
mid-bass: less
mid-treble: more
upper-treble: less

Neither curve is better; they are equally imperfect — at least they are both smooth; no really jagged response peaks or dips. I really need to draw the two curves on a sheet of paper and scan and upload it.

The dream earbuds I am looking for would be an average of the Sony low-end earbuds and the 868: these wouldn’t have so much high-treble as the 817 [821], and would have more mid-treble (thus sounding less cold than the 817 [821], while still having more upper presence than the 868). The ideal earbud would have the same amount of low-bass and mid-bass — it should have more mid-bass than the 868.

I compared the mid-bass and low-bass using _No Sleep til Hammersmith_, a live album by Motorhead, with prominent bass guitar as well as kick bass drum. With the 868, the bass leads sounded thin, like a guitar, rather than full and meaty — and the bass drum (low-bass) drew too much attention away from the central region of the bass spectrum, which is occupied by the bass guitar. On the other hand, with the 817 [821], the cymbals were overly present, and distracted from the lead guitar. Although wide frequency response is important, you don’t want extreme bass (low-bass) overshadowing the mid-bass. And you don’t want the extreme, high-treble so loud that it weakens the presence of the mid-treble. (I assume that you always have a good amount of upper-bass and lower-treble; these are easier to reproduce.)

Sony Low-End Earbuds (807, 817, 827, 837 in 1997/98) (in 1998/99: 811, 821, which are “reduced leakage”)

The low-end Sony earbuds are light, small, durable, fit well for most ears, are comfortable for most ears, and have a lot of bass (including low-bass) and treble (especially upper-treble), and are inexpensive ($9-$30).

My 807V and 817 [821] have the symmetrical wires; the left earbud does not have a much shorter wire than the right earbud.

A good thing about studying the Sony line is that you can find them most everywhere – particularly the 807, 807V, and 817 [821]. Some hi-fi stores don’t carry the 817’s [now 821’s], but they carry the [old] 837’s [now no low-end ones with gold plug?] with the same drivers but a gold plug, to make a secure connection.

Sony 238 Earbuds

>My MDR30 came with an ad for MDR-ED238L Fontopia Ear Buds. Any opinion on these?

>Paul Buckley

These sacrifice too much treble, in my opinion, to earn a little more mid-bass.

Some owners recommend these, but I think they have too little mid-treble and upper-treble, and too much upper-mids and lower-treble, resulting in a moderate “can-like” sound. They have the most bass, at least the most mid-bass. This model is not recommended by me, though most everyone is happy with the quantity of general bass. The chamber shape and mouth of the 238 seems to introduce resonance problems, similar to closed-back headphones. The bass sounds quite good on mine, *if* they are inserted into my ears. (The mid-bass dominates over the low-bass, unlike with the low-end earbuds, which have a balanced amount of low-bass and mid-bass. I think the low-end Sonys have the best balance of mid-bass versus low-bass.)

238 has the highest ratio of mid-bass to low-bass. Then the low-end buds, then finally the 868 has the least mid-bass, with the most low-bass — meaning that the bass isn’t quite full-bodied in the heart of the bass spectrum. (This all assumes a typical megabass compensation setting.) I own these 3 models and have focused on comparing these ratios — but most people just think in terms of “how much bass is there”. You might not want to be so detail-oriented, but I think you will hear the difference, even if you can’t specify it in terms of frequency response. Bass differences are important, but treble differences are greater than bass differences in Sony earbuds.

The coupling factor: you can rotate the shaped part. They have more mid-bass fullness than my 817’s [821’s]; the 817’s have the powerful low-bass but not so much mid-bass. The 238’s have a hill-shaped response, with the peak centered around the mid-bass. See also: Coupling.

The driver housing and stem is one-piece. Instead of a front grill and a cushion, there is a tapered horn with 7 holes that goes into the beginning of the ear canal. These collect ear wax and you have to clean your ears vigorously every few hours.

The plastic hurts (irritates) my ears badly. Another owner reported them feeling very comfortable later. I am used to cushions on earbuds; these don’t come with any.

Sony 868 Earbuds

At first, these have less low-bass than the low-end Sony earbuds (unless pressed against the ear) – but they might loosen up in 2 weeks. They also (at least initially) have less upper-treble than the low-end earbuds; instead, they have have sibilance-spasms: when the music hits an “s” or “t” sound, there is a sharp peak in the mid-treble, caused by the headphones. This is the well-known “roughness” that is supposed to go away and “smooth out” after the break-in period; supposedly this spasm turns into smooth high-treble. Something similar is supposed to happen with the low-bass too.

A little *big* and heavy, coupling not quite as good as the low-end models, thus bass is practically weaker. I’m continuing to test and live with these, comparing them to my 238 and 817’s. [now “821’s”]

>I’ve been using the 868 for quite a while, and I recently bought the MZ-R30. The earbuds that came with it were surprisingly good and I find myself constantly comparing between the two. When I first bought the 868’s, I hated them. I immediately noticed their lack of deep bass, and I found the design to be very uncomfortable. Since then I’ve really gotten use to them. The R30’s (i don’t know the actual model #, they’re silver on the sides with a remote and a gold plug) are the complete opposite. Very strong bass, but the overall sound quality isn’t as good. I’ve got this one song with a very deep bassline that the 868 just can’t handle (unless at a very low volume,) the left one, especially, starts cracking at every beat, but the R30 has no problem with it. With other tracks, however, the fuller sound of the 868 clearly outshines that of the R30’s. I find myself having to switch back and forth on a regular basis depending on the nature of the song that i’m listening to. Are the 888 the solution to my problem? Are they really worth the extra 40$ that they cost over the 868?

>I bought the 868’s and felt that the sound was good but that they were also very umcomfortable. About a month after I bought them they broke where the wire enters the device and then it happened with the other ear.

I own many sets of earbuds including Sony high-end. But I like the $10 Sony earbuds best of all. And they are comfortable except for *long* sessions. The bigger Sony’s irritate my ears almost immediately.

Let me put it this way: everyone who is looking for earbuds should own a cheap pair of Sony earbuds, for only $10. I haven’t heard their new “reduced sound leakage” design though.

Date: Fri, 20 Feb 1998 16:22:39 -0800
From: Ken Savage
Subject: Sony earbuds

>I have a pair of MDR-E565’s that I’ve owned for about a year and a half now. I don’t think they’re made any more, but prior to them, I had a pair of 868’s. The 868’s (bless their souls) were nice earbuds, but they started to buzz in one ear, so I put them out of their misery. The 565’s were more expensive, between the 868’s and the 888’s, and I’m quite impressed with the sound quality. Like most earbuds, they’re not as powerful in the bass end, but if you push down on them, bass goes up a *lot*. I use them in my MD player (E30) and I’m sure the day THEY die, a few tears (of frustration at finding and breaking in an expensive pair of buds) will be shed.

>Ken

Sony 888 Earbuds

Some owners say that the 888’s sound terrible, and some say they sound great; some claim they sound terrible for two weeks and then they sound great. If my $40 868’s sound much better after break-in period, then I might gamble $80 and buy (and break in) a pair of 888’s; I’ll update this page as my tests progress.

“At first the sound was terrible, no bass, harsh treble. Really dissappointing. I knew earplugs like these aren’t exactly high end, but this was bad! With bass boost on the MZ-E30, it was worse – more bass all right, but also more treble spasms. The more bass boost the more terrible sound, thin and ugly. Well, after a few weeks things started to change! They ‘loosened up’. Now the bass is there, deep and realistic, treble is right, I’m impressed! (it is important to push them into your ears). Extreme ‘s’ and ‘t’-sounds are only there when the material says so.”

From my in-store testing of a pair that might not have been broken in: these $80 earbuds had less midbass, less low-bass, and less upper-treble than the low-end earbuds. People give very conflicting reviews of these.

The shiny pearl-blue metal accent calls too much attention to itself; it looks like earrings.

>I have an MZ-E30, and had an MZ-R3. Upgrading the R3 stock headphones to a pair of Sony’s top of the line E888 headphones yielded excellent sound. However, when the E30 stock earbuds were replaced by 888’s, the sound was much poorer, treble was really rolled off, and the sound was sort of on the soft side. Some people might like it, but it is FAR from being representative of the music.

>The E30 and R3 both had the same factory headphones (E838), and I’ve also tried swapping them…. Same results.

>Either there is some sort of impedance mismatch, or it could be the megabass settings that are different on both. I’ve tried different settings too.

>Try Sony MDR-E888, with biocelluloid membrane. Do -not- try them in the store before you buy, if you are not sure they are allready well used – they sound terrible the first couple of weeks. Now I enjoy these so much that I even use them at home. I prefer them to Koss Porta Pro (which is ‘warmer’, but a bit muddy in bass and midrange, and not so huge and spacious), Sony MDR-D65 (has thin tinny treble and tiny bass because connection to the head (my head anyway) is not good). They even come really close to my AKG 270 (which is not intended for portable use at all (and cost twice as much)). I never believed tiny earbuds could sound so huge, dynamic and weighty. If I should pick on something, the treble is perhaps still a little bit sharp (on the MZ-E30) [sibilance spasms?], but this may just as well be because most studio recordings are a sonic mess anyway.

“Don’t buy Sony’s 888 top model, since they sound lousy. There is hardly any bass, even if you max your bass boost. They costed me $75 and are now in a drawer, with the rest of the earbuds I’ve tried. I currently still use the ones that came with my first Sony portable, the MZ-R3, rather than the 888’s. I find the earbuds included with this model (there’s no number on them, just the word MiniDisk) very good, rich bass and exellent mid and high. No other earbud has topped the R3’s stock earbuds so far. For now, I can only say: don’t buy the expensive Sony 888’s!”

I have spoken with sincere, experienced salespeople who consider the 888’s the world’s best earbuds, and the 888’s have gotten some favorable remarks in the mailing list. Some owners say buy them, some say don’t.

From: “Toby & Kan Lai” Subject: Earbuds for R50 Date: Fri, 13 Mar 1998 19:46:23 -0500

>I want to replace my Sony MZ-R50 stock E838 earbuds. Not that I don’t like them, in fact, I do, but the phones wire is damn to short (designed to use with the remote control). Now I want to find another pair that would sound close, if not the same, to the E838s. What’s your suggestions? I’m considering the E848s because 1) they are in the same 8×8 class, and 2) according to your Sony earbuds table, the sound characteristics “fair bass, fair treble” suits my needs.

>Any suggestions/pointers are greatly appreciated.

>Toby Lai

Stock Earbuds for Sony R3 MiniDisc Recorder

“I currently still use the earbuds that came with my first Sony MiniDisc portable, the MZ-R3, rather than the 888’s. I find the earbuds included with this model (there’s no number on them, just the word MiniDisk) very good, rich bass and exellent mid and high. No other earbud has topped the R3’s stock earbuds so far.”

Stock Earbuds for Sony E3 MiniDisc Player

“Last summer I bought a MZ-E3, with horrible earbuds included with it. I also bought the 888’s. I also bought the 238 (“Groove”) model, which should have enhanced bass sound because of the new cap design. Well, bass sucked [! I question this -mh], as did mid [too much??] and high [too little??][sucked in what way?] sound. After all these comparisons, I’m back to the MZ-R3 MiniDisc player’s stock earbuds, because they sound better than the 238 earbuds, the 888 earbuds, and the E3 MiniDisc player’s stock earbuds.”

Sony MDR-E464 earbuds

Date: Thu, 19 Feb 1998 13:03:38 -0500
From: Kevin Brower

>Are you familiar with Sony’s MDR-E464 earbuds? I purchased them about 8 years ago and they were high end at the time. I continue to use them today instead of the earphones that came with my R3 unit. They still sound great. Do you know what model Sony currently has that compair to the MDR-E464? What earplug do you beleive is the best?

>Kage

Sony NC10 Noise Cancelling Headphones

Date: Thu, 19 Feb 1998 03:16:52 EST
From: Ellissan at aol.com

>Have you ever compared Sony’s MDR-NC10 Noise Cancelling headphones? I use them when I travel with my MZ-R30 and MZ-E30. They are a little more expensive than the others Suggested retail is around $199. But I am convinced that I can’t find anything better in the size category.

>Anyone who travels alot by plane or who is consistently communting by rail will appreciate the amount of outside noise reductions these puppies provide. You don’t even have to have them connected to a source to appreciate the cancellation effect. I get a kick when the flight attendants come around asking people to turn off their portable electronic devices (because I’m still wearing the headphones at this point) and they’ll ask me to put my MD away….then I show them the miniplug which isn’t plugged into anything. Anyway, if you have the means…I highly recommend them.

>Pete Date: Thu, 19 Feb 1998 05:34:15 PST
From: E Davantes

>I am a military resident of Japan. Your page is great and well-needed, considering the mass of awful sounding earphones out there. I’ve wasted lots of cash on crappy earphones and have gone through a countless number of earbuds and headphones. These earphones I’m about to explain are the best I have heard. I even almost purchased the Sony StreetSounds hours before seeing your page, they look too cool to sound so bad. [search this page for “street”]

>I almost died not reading anything about my favorite earbuds on your page. I bought them overseas, the Sony MDR-NC10. They are noise-canceling earbuds that are optionally powered by a single AAA battery. They have one large button on a “remote” that allows you to hear your surroundings as you press the button. The buds are the size of hearing aids but the sound on this model surpass even the best full-sized headphones. The sound can be compared to listening to a boomin’ car system and with few instances of distortion. I cannot begin to explain the bass on these things! Without power, the bass is deep and clear. When powered, they really *kick*. The treble is average-to-good without the AAA battery, but when powered, they have strong mid-treble and have the sweetest high’s. These are the best sounding earbuds I have heard-hands down. [are they earbuds, or headphones?] I use a Aiwa AM-F5 MD recorder that has about the same bass as a MZ-R50. I can send pictures in case you haven’t seen them before.

Other Brands of Earbuds

Etymotics – The Ultimate Earbuds

Etymotics page at Headphone.com

>Date: Sun, 21 Jun 1998 22:12:12 +0800
>From: “Mark Jones”
>To: hoff at cybtrans.com
>Subject: Earbuds and the Etymotics in-ear phones

>I am, what I consider to be a (“serious”) portable audio listener. Your comments on earbuds was fascinating to me. Until a week ago all I used was either the MDR-E827 or the MDR-E888. I picked the 888’s up in Hong Kong a few months ago, and was, and still am disappointed in their bass response. The 827’s I have had for over a year, and until a week ago there was nothing on the market which came close to their bass response.

>Now a week ago I made a significant investment and purchased the Etymotics Ear Canal Phones. I say significant investment, because a laid out $270.00 for these things! These phones fit in your ear canal, and provide 25db isolation. Everytime I pout them on, it takes me a few minutes to crawl back up from the floor! The sound is just amazing! The bass you don’t feel pounding at your chest, you actually hear it! These things are just amazing!

>The problem with them though is that you need a good amp to push them. In addition to this purchase I bought a headphone amp from HeadRoom (“Supreme”), and with my Sony MZ-R50 coupled to the Supreme Headphone Amp and the Etymotics, well I have true portable hi-fi audio! The investment was $850.00 total, but if you are serious about portable audio, then this is a good investment.

>I spend allot of time on the road, international travel, and not having quality audio for months on end is just not exceptable to me. My portable system includes the Sony MZ-R50 MD Recorder / Player, a Sony D-E805 Portable CD (“I love it!”), a pair of Bose Room Mate II Self Powered Speakers (“the bass is awesome”), the HeadRoom Traveler System, and the Etymotic Ear Canal Phones.

>Now, I still use the MDR-E827’s quite often. They are moisture proof, and have excellent bass, and fit my ears nicely. When I am riding my bike through southeast China, I have a problem using my Etymotics and having them fill with sweat! The MDR-827’s are just as amazing to me as the Etymotics. And the sound seems to just get better and better the more I listen to them. And with the 827’s coupled directly to my MZ-R50 MD, their is no need for an amp, you got all the volume you would need.

>The 888’s just don’t have any bass, even after a 2 week break in period they did not improve! I have even tried cushions over cushions, and this did not help. I would not recommend them to anyone, though no one individual hears the same, so you be the judge. I also got some Senn’s and Grado headphones, though don’t listen to them very often, especially since I got the Etymotics. Seriously, there is nothing on the market which can compete with the Etymotics! These things are simply amazing in every sense of the word!

Stax earbud electrostatic in-ear headphones

>Just saw your page linked from the minidisc page. I’ve got some 888’s bought in the hope they’d sound good – they seem OK, but so far I’ve only used them on the CD player output of my SGI 02 CD-ROM drive at work – not the best quality of sound! I must take them home some time. I had a pair of 575’s (?) which used to sound nice, but then they stopped working.

>There are a pair of Stax earbud electrostatic ‘phones. Actually they may be in the ear with headband (?) If you want to know more, let me know, I have some literature at home, and a scanner at work.

>Amardeep Bhattal

Sennheiser Earbuds

Magnolia Hi-Fi said Sennheiser earbuds sounded disappointing; they said Sony’s high-end earbuds sound much better (with cushions, after break-in, as usual).

Sharp Stock Earbud

Someone said the Sharp earbud was really good, that came with a particular model of Sharp player.

Headphones for Sharp 311

Date: Wed, 5 Aug 1998 17:47:53 +0100
From: Mark.Howard at wdr.com

>I had a look at your earphone page – very interesting and good news as I much prefer to stay with earbuds.

>I’m looking to order Sharp’s 311 from Japan but concerned that its headphone amp is only 5mW. I’m worried that the volume will be too low like Sony’s EP11.

>Are you aware of any earphones that I could get that would ensure volume is adequate? Nothing excessive – just up to the level of the Sony R30 for instance.

>Mark

Aiwa

I bought some cheap Aiwa earbuds. They have peaky low-treble or upper-midrange (fatiguing). The wire doesn’t enter each driver housing in a secure way; the resulting rubbing creates a terrible noise — poor design; avoid. However, note another opinion, below. We need to track model numbers. I’ve only heard one Aiwa model.

Date: Sun, 19 Jul 1998 18:01:51 -0400 (EDT)
From: Michael Schuster
Subject: Sony earbuds

>I differ with your opinions about the cheap Sony earbuds. I was surprised to see you recommend $9 Sony phones as your top choice. I went earbud shopping in Chinatown NYC after reading your article, and on the shelf the 817’s looked like the crappy stuff they package in with $49 tape players – things that sound so bad I don’t even bother unwrapping them as a matter of principle.

>Anyway I invested $10 and listened to them using a known pocket radio on the way home. Bleeeraaachhhhh!!!!!!

>These sound harsh, shrill, tinny, and have almost NO bass compared to what I’m used to (see below). Turning on the bass boost improved the situation somewhat, but only marginally. And yes, I was wearing the earpads which I always use – not so much to boost bass but to keep them from falling out of my ears!

>Anyway, I was surprised to see you dismiss my favorites – Aiwa – without a second thought. My favorites have always been the mid-priced Aiwa phones (about $25-$30) represented by the last ones I bought, the HP-56. I’m sure they’ve been replaced by a couple of generations of newer models with similar numbers. Actually my favorites have been the expensive HP-V88 (long discontinued) which sound the closest to my favorite over-ear standard phones, the Sony MDR-V6.

>I find the AIWAs to have smooth high end without sounding shrill, excellent high and mid-bass, and at least some response in the low bass. And I hear no artifacts related to movement of the wire attachment point as you note. Perhaps you might want to give this line a second look.

>Regards
>– Mike

From: DOX

>I have a pair of $15 Aiwa buds that I absolutely love! They don’t have the unsecure wire problem you listed. Their biggest advantage is the smooth rounded exterior design (with the bass-boost pipe design) that allows you to insert them in your ear “backwards” (pipe out above ear lobe rather than vertically down your sideburn). This seals the ear, boosting bass response, and places the driver at the outside facing into the ear flap dramatically smoothing treble response.

>Now the bad news… I blew one driver when I plugged it into an over-driven jack! Big bummer because when I went to the local Best Buy (where I bought the original) they only had the HP-V155 model which I assumed was the same… needless to say it is not. The mechanical design makes it very uncomfortable and I’m sure the driver won’t get any better after a “break-in”. Still looking for a comparable model to my old ones. If they still make that model I would highly recommend it! If all of there models are like the V155 I’d say AIWA truly sucks.

Koss

I’d like to try Koss earbuds. The cheap Koss ones have a secure entry-point for the wire to enter the driver housing of each earpiece, eliminating that loud rubbing noise.

Kenwood

I bought the $10 earbuds by Kenwood. They have the letters “Kenwood” and a little gold strip on the side. They come with a fairly large bag/case. These have a wide frequency response but a major, narrow hump around 250 Hz (upper bass). When I cut this band by 12 dB using a 10-band equalizer, then the boxy sound was eliminated and they sounded normal. Avoid – very boxy sound.

Date: Thu, 19 Feb 1998 02:58:00 -0800
From: Lithium
Subject: Earbuds

>You said that you wanted to try the Kenwood earbuds, well I recently bought the Kenwood DMC-J7R MD portable, and I really love the earbuds that came with it. They sound great, but you are right, you need to boost the bass a bit. I have stopped using my studio monitor headphones and have started using the earbuds. 🙂 Mostly because the headphones are big and hot… The Kenwood earbuds don’t come with cushions, but I went out and got some and it did help the bass.

>You complained that the Sony megabass was too much and they needed a new level 1 setting, well I have listening to the Sony and I think the Kenwood/Sharp (Kenwood just clones the Sharp MDs) bass boost is FAR better. It is clearer and the level 1 is much less than Sony’s, it has levels 1-3 and I usually prefer level 2. I have heard other people say the same thing about the Sony megaboost, that the Sharp’s is much better.

>Matt Staver

Date: Thu, 19 Feb 1998 05:34:15 PST
From: E Davantes

>The stock Kenwood earbuds that come with DMC-G7R (an MS200 clone) sound pretty darn good. Deep/mid bass is amazingly clear and treble is strong. They don’t hit (bass) very hard, but that makes the lows very clear and prevent distortion. However, on a new DMC-J7R (MS701 clone) the stock earbuds sounded awful. Same company, and the earbuds look the same, but the sound was very tinny and distorted easily.

Radio Shack

Their $30 high-end earbuds look interesting. Has anyone heard these? They are next on my list to demo, but I am done with research for now.

Headphone Tips and Ideas

Breaking-In Earbuds

Like a violin, or speakers, earbuds supposedly need to be broken in and loosened up, before they sound good. I’m burning in my $40 868’s by leaving them playing an FM station all day long, at a fairly high power level.

The standard driver has much more high-treble than the high-end models. Some people say the high-end models have more than the regular models, after a couple weeks.

My new 868’s currently have less low-bass than the low-end Sony earbuds (unless pressed against the ear) – but they might loosen up in 2 weeks. They also (at least initially) have less upper-treble than the low-end earbuds; instead, they have have sibilance-spasms: when the music hits an “s” or “t” sound, there is a sharp peak in the mid-treble, caused by the headphones. This is the well-known “roughness” that is supposed to go away and “smooth out” after the break-in period; supposedly this spasm turns into smooth high-treble. Something similar is supposed to happen with the low-bass too.

Due to break-in considerations, you can’t do a meaningful demo of the high-end earbuds in the store. You have to have faith, buy them, play them a lot, then listen to them. This complicates A/B testing efforts.

Matching Megabass and Earbud Response

Megabass parameters differ among players. You have to factor in megabass together with headphones, there’s no way around it for portables. Finding the right combination of settings and headphones is important. The Sony earbud packages say “designed for megabass” — but the opposite might be more historically accurate; the eq parameters for megabass were designed to produce the inverse response curve of earbuds, to complement earbuds. The E40 player has massive boost (*much* more than my Sony CD diskman player’s “megabass”) that fits like a glove with bass-challenged earbuds. The E40 has a good first-position boost, but the second position is far too much. It needs to move position 1 to position 2, and insert a new position 1 setting that’s half the level of the current position 1 curve.

Equalizing Headphones, Built-In EQ Compensation

I did some more critical eq’ing and listening to my $10 817’s on my home hi-fi. These sound amazingly smooth; they just need a lot of low-bass boost and a little upper-treble boost to sound unusually smooth and flat all across the spectrum. So I am familiar with the full voice and potential of these. They certainly do respond musically to the lowest bass and highest treble, without sounding jagged from one frequency to the next, though they do need some electronic boosting. Then when I listen to these without the help of tone controls, I have a better, ideal reference point. Really bad headphones or speakers are impossible to fix with a 10-band eq; their curve is just too jagged and rough from one frequency to the next.

Skillful use of a 10-band eq can fix any decent headphones, or even lousy headphones. For home listening, then, an issue is *how easy* is it to eq a particular headphone? I’ve found all the earbuds very easy to equalize: simply progressively alter the highest and lowest bands. Some full-sized headphones have weird jags (peaks and valleys at unpredictable frequencies) that make it tricky to iron out the curve with an eq. In other words, I find earbuds to be *smooth* and straightforward in their frequency response.

How I use the $10 817 earbuds as hi-fidelity home headphones:

On 10-band eq:
31.5 Hz at +12db
63 Hz at about +6 db
16 KHz at about +5 db
optional: cut 2 mid-bass bands on the eq by 2 db.

On receiver:
Bass set at 3 o’clock
Treble at 1 o’clock

With serious equalization, I can get very, very good sound through my $10 headphones — I suspect that they are actually as smooth as Sennheisers or Etymotics, but just bass-challenged. These earbuds do have smooth bass from one frequency to the next and they do have musical response in the 31.5 Hz band of a 10-band eq, it’s just that the overall level of the bass (20 Hz-120 Hz) needs a lot of amplification — which is what some of the more intense megabass controls are designed to do, with the mathematical smoothness and precision of R-C curves. The result is an exceptionally flat, smooth, and controllable response curve. Thus I now think that equalization is what needs attention these days, rather than particular models of earbuds or ATRAC versions.

The bass and mid and treble should be present and should be at the same levels. Mid is not evil, it’s just that there is usually too much of it relative to bass and treble. Mid’s can be warm and rich.

I haven’t found any headphones that sound flat without eq. All headphones need eq, to sound flat. I’m still in the market for full-sized headphones that are comfortable. Maybe the 580’s, though they do need bass boost.

Defining Smoothness and Balance in Terms of Frequency Response

hoff9.gif
hoff10.gif

(The earbud curves above assume using a standard bass-boost compensation curve.)

Smoothness is fine-level response from one frequency to the next (such as 16,000 Hz vs. 16,100 Hz). Balance is broad-level response of the entire bass region, mid region, and treble region. By “smoothness” I mean breaking the spectrum into many narrow bands and comparing volume levels of adjacent bands. By “balance” I mean breaking the spectrum into 3 or 9 bands, and comparing the volume levels in each of these broad bands, whether adjacent or distant.

The bass drum should be about as prominent as the cymbals, and all the frequencies in between should get their fair share of prominence too. Cymbals shouldn’t steal attention from the bass drum, and vice versa, and the guitar needs to sound warm too. Equal opportunity for all waves, long, short, and in-between.

From: Sergey Belonozhko
Subject: Equalization

>I have read your article about ear-buds and I like it. You have taken a really important question about equalization. You are right that all portable players have to have equalization (preset or manual). And now the best way is to buy portable amplifier from Headphone, but it’s “a little bit” expensive for most of the listeners. I found something very cheap (in comparison to Headphone amplifier), but may be helpful (I didn’t try it yet). It’s Koss portable equalizer (not amplifier!) which allows 3-band stereo equalization. Koss’s crummy headphone equalizer

This is the worst piece of equipment I have ever tried. I tried all combinations of volume pot settings, but the bottom line is, this has no headroom at all — there is no space between its noise level and the point at which it distorts. Do not buy the Koss! — hoff

>If it doesn’t work just try http://www.koss.com and find eq/30 equalizer there in Portable Accessories. Please, write what do you think about. Probably, I’m gonna use it with Koss ksc/35 sportclips or with Sony 817.

>Thanks,
>Sergey

Cushions Increase Bass

Use the cushions; they make the bass much louder. One earbud enthusiast has a collection of earbuds and uses cushions over the cushions, claiming significantly more bass than one layer of cushions — definitely worth an experiment, given that there is an amazing, total difference between no cushions and one layer of cushions.

The 238’s don’t have cushions… Adding (customized) cushions to the 238s *might* make them have even more bass, but I don’t know if they would have enough low-bass to match their mid-bass.

Use cushions (felt/foam) with earbuds. This gives much better bass! Bass also depends on your ear shape.

Earbuds have no bass when I take the cushions off, but relatively awesome bass when the cushions are used. Does anyone have a hypothesis for this? It’s striking – night and day. Now when I say “earbuds can sound excellent” I make sure to say *with the cushions on* as well as “with some bass boost”.

This is a *huge* bass boost effect, so take note and be sure to do a comparison test of with/without cushions! Note that the contoured Sony 238 earbuds have no cushions.

The Sony packages say “if the size is too small to fit right, then use the cushions”. But that’s bad advice. The cushions are mandatory, to get loud bass. The smaller 817’s are the right size, if the cushions are used. The 868’s are perhaps too big, if the cushions are used; they are heavy and big; I imagine they flop away from my ears, especially with the asymetrical cable, that pulls down on the left earbud. The Sony low-end earbuds are so light and small, they can be placed right up against the ear canal, and they stay there. I don’t know about other people’s ears, though; ear shape variation (and psychoacoustic variation) could explain why people give conflicting advice about earbuds. (See also Coupling.)

Coupling with the Ear Canal

Bigger drivers and better stated response do not necessarily mean louder resulting bass. Tight coupling with the ear is the dominant factor, and small size can couple better with some ears. The high-end Sony earbuds are big, which seems like it would be better, but at least initially, these seem to effectively have *less* bass than the low-end earbuds. With earbuds, the coupling with the ear canal is 90% of the bass problem. Making the driver bigger actually can make for poorer coupling with the ear, and thus, *less* bass. We Americans have trouble with the concept “small performs better than big”.

See also Sony 238 Earbuds.

Packaging

Sony low-end earbuds: each channel’s unit is one-piece, no joint or narrow spot to break – indestructible. The low-end models are *solid*, literally, with no joint to break, between the driver and stem; it’s one smooth curve of tough plastic with no narrowing.

Sony high-end earbuds have separate disk-and-stem, which can break — I saw a broken one in the store; can’t happen with low-end models.

For portable MD, good earbuds are the best way to go, I think. Walkmans etc. are a little out of style in the U.S., it seems to me, so I really want my portable system to be small and invisible, low-key. Over-the-head or behind-the-head are too visible. Near-invisible systems such as miniaturized MiniDisc players with earbuds are stylish, insofar as any system of equipment and wires can make you look stylish.

If earbuds don’t fit your ears, try different shapes of earbuds. Or hook-over ears, or vertical. (Unfortunately, “try” usually means “spend $100+ buying several”).

Testing Headphones

Your testing results may differ, depending on the unit, cushion, ear shape, eardrum, tastes, song mastering, and psychoacoustics. Many people are happy with each Sony earbud (low-end, 238, 888). Other people think earbuds are all sonic junk. All do need appropriate low-bass boosting, but megabass when properly designed, could perfectly compensate. E40’s first megabass position is great except for the terrible fact of bridging the bass to mono.

When listening for bass response, don’t be fooled by mid-bass. Listen to the *tone* of the bass, not just the quantity. Listen for the ratio of mid-bass to low-bass. Same for treble. Don’t be fooled by loud mid-treble. A tinny (tin-like) sound often means loud mid-treble with a sharp drop. At both ends of the spectrum, beware of the hump-then-dropoff effect, which gives the illusion of wide frequency response, but stops short.

Headphone Extension Cables

Radio Shack’s 1/8″ headphone extension cable is 20 feet long, and kind of thick. Sony has a nice extension: for $10, you get a 10-foot cable of nice, *thin* cable, and a 1/8″ to 1/4″ adapter — better for earbuds. In fact, I recommend plugging the thick, long Radio Shack cable into your home stereo, then connect the thin short Sony extension, then your earbuds – it’s most ergonomic as far as cable weight distribution. The extension’s jack and the earbud’s plug together are too heavy though; I’d love a lightweight microplug and microjack here, if they are secure and sturdy enough to walk on or yank.

Equalized-crossfeed to simulate speakers

Date: Fri, 20 Feb 1998 12:27:41 +0100
From: Peter Clijsters

>Hello from another MD freak,

>On your pages I read something about an eq’d crossfeed circuit, and information about it could be found at www.headspace.com. I din’t find anything about it, could you please give me the exact URL of this page. BTW great job on the earbud thing. I myself use them to (when I have to that is, like walking in the streets), but most of the time a use the Sony MDR-D77 headphones. Have you tried these, what do you think of them?

>Thank you,
>Peter

Delayed eq’d crossfeed circuit, psychoacoustics of speaker placement

Their cheapest speaker-simulating headphone processor/amp

This delayed, eq’d crossfeed circuit that should be added to walkmans and all stereos’ headphone jacks. It makes the ears think the speakers are placed away from the head, which should then sound a lot better.

I haven’t heard the D77’s.

Non-Earbud Headphones

Vertical Headphones

See also the Sony so-called “vertical headphones” (over-the-head headband, with earbuds turned sideways). Note: no cushions here. What if you put cushions around them – wouldn’t they have more bass, like earbuds? I saw another brand that had cushions on vertical micro-headphones.

JVC HA-D700, 990

I have had the $65-80 700’s for several years. They have the best combination of balance and smoothness of any headphones. They are my favorite headphone for flat-eq listening, such as the headphone jack of a home CD deck. They have the most balanced bass vs. mid vs. treble, and sound smooth from each frequency to the next. I don’t see them on the JVC web site; only the 990’s are there.

The 700’s are snug and comfortable. The 990’s appear to be the 700’s, with packaging that’s supposed to be a little nicer. I don’t know if the drivers are different.

The 990’s, which I have not heard, are $120 (see Jvc.com). They need a slight boost around 13kHz. They are warm and very tube-like without being muddy; they seem to have a medium-width emphasis through the lower mids. The bass is extremely good, strong but not boomy; closed-back but not boxy sounding. I really lucked out when I found these. I still think the Sennheiser 580’s and the new high-end super-open Sony’s are interesting and I would like a pair, but those are open-back and *must* have treble cut and bass boost.

Grado 60

Very clunky packaging. Earpieces spin (takes effort to put the phones onto your head). Far too thick cables. Thick, sharp y-connector at your upper chest or back. Need bass boost and treble cut. Too much treble; in rock, cymbals are so loud, they block the rest of the spectrum. These don’t sit securely on the head. Very weak where wire enters driver; can break in the store.

I think, “I would enjoy this music if you would stop banging that great-sounding cymbal right in my ear, drowning out the rest of the band.” The treble in the Grado’s sounds great, open, and smooth (a hard achievement) – there’s just too much of it. Here I should clear up my statement about Sennheiser 580’s and Grado 60’s having “no bass” — I mean, when you plug into the CD player’s headphone jack, the treble is certainly too loud compared to the bass, though they both are smooth curves. The Grado’s sound more balanced with bass at 3 o’clock and treble at 10 o’clock.

Denon 950

Thin peaky high treble (a sharp single-frequency hiss, not smooth/uniform across frequencies).

Denon AH-D210 Headphones

Date: Fri, 20 Feb 1998 16:49:52 -0500
From: John Hoffman

>I use a pair of earbuds that came with RCA’s old MD player; they’re very good, though bass response is a little on the low side… I’ll have to try some cushions, they didn’t come with any…

>I *STRONGLY* recommend Denon AH-D210 headphones. They have an incredibly deep, clear bass response. The only thing I don’t like about them is they’re a bit larger than I’d like for portable use; otherwise they’re ideal.

>The Denon 950’s are cozy, tons of bass. But the treble is fizzy, thin, 1-dimensional, not smoothe. I had to make a jagged eq curve to smooth out the results. They seem to have a sharp peak around 16kHz – sandy sound. Good packaging, blows away the Grado’s. But I’m going to buy the $120 JVC 990’s – very comparable to the Denon 950’s in packaging. I haven’t heard the 990’s yet though. I will listen to the other Denon’s in the store. — hoff

>I haven’t tried the Denon 950, they’re somewhat out of my price range, but I haven’t noticed any problems with the treble.

Low bass response is to be expected with all earbuds. The part I’m critical of is, how smooth is the treble and mid’s? — hoff

>I’m afraid I’m not a musical gourmet, more of a gourmand; the sounds I listen to tend to wipe out any subtleties in the playback medium, aside from white noise, and increasing the range is the way to improve it.

>John Hoffman.

Sennheiser 580

I like these. Nice packaging, though not so snug and cozy as the Denon 950’s or JVC 990’s. Open-air. Inefficient; too quiet for walkmans. Breakable where wires enter drivers; often broken here in the stores. Sound similar to Grado’s: need bass boost and treble cut for balanced rock sound. Smooth, but not balanced; tilted toward treble like a flat up-ramp across the spectrum.

AKG 240

Steve wrote:

>The choice of many recording engineers are the AKG 240 or 240M’s. I know several very good freelance and staff engineers who alway carry a pair because they are not sure what the montitors will be like in any particular studio. I’ve seen them mainly used for referencing while tracking or checking mixes, but also watched a very good engineer use them as the basic monitors in a project studio that had a poor control room listening evvironment. He mixed the project on them then ‘referenced ‘ through the studio’s speakers, small aurotones, a boombox and a car cassette player.

>Since they are closed ear they can also be used for tracking if the there is no control room and the console is in the same room (or nearby) as the players.

>They are very comfortable to wear and extremely flat. I have a pair for my modest studio, but really enjoy them for other uses like plugging into a preamp or hifi VCR. The list for about $100 but can be had for $89 on sale. They are worth the extra money.

>Steve

AKG 270

“The 888 earbuds come really close to my AKG 270 (which is not intended for portable use at all (and cost twice as much)).”

Radio Shack Pro-25

Very good bass, fairly good treble. Recommended by many people. $40; on sale every other month for only $20. Not the same as Koss Porta Pro Jr; it’s a myth that these are the same. They are indeed made by Koss, says “Koss” on the plug casing. Cover ears mostly. Very nice fit, more secure than Grado’s; comfortable. Porta Pro users say the Pro 25s are less comfortable for extended listening.

These are bass monsters — perhaps too much bass, relative to the treble. I’d like to A/B them against the Porta Pro Jr, which supposedly are slanted toward the treble (too much?).

Koss KSC/35

Clip-over ears, no headband. Cover ears mostly. Same driver as Porta Pro Jr. Recommended by many.

Koss Porta Pro Jr.

Foldable. Recommended by many. Compare RS Pro-25. Headband. Supraaural. Above-ear temple pressure pads relieve ear pressure.

Koss Porta Pro

Recommended by many. Bigger version of P.P.Jr.

“Koss Porta Pro is ‘warmer’ than the 888 earbuds, but a bit muddy in bass and midrange, and not so huge and spacious.”

Sony MDR-D65

“The Sony MDR-D65 has thin tinny treble and tiny bass because the connection to my head is not good.”

Sony StreetSound Headphones

>Recently I tried Sony’s StreetSound (there are two models here, I bought the most expensive one, $30) model that covers the ear completely. This design could actually be excellent, but they were disappointing, yet the concept is very promising. If they would make a high end model of this concept, it could be a winner.

Sony R11/33/55/77 portable headphones

From: Peter Clijsters
Subject: Re: headspace.com

>I own the R77 and I think they are the best “portable” headphones on the market. I use them with my MZ-R30 and they make a very good combination. They come with a microplug connection cable and an ingenious folding headband that lets you fold them together (when folded, they are not much larger than my fist). There is a cheaper version (the R11) for about $50.

>Best regards,
>Peter

c. 1998, 1999, Michael Hoffman.
From Hoff’s Audio Site. Republished with permission.

 

Taking Audio in Another Direction.

police_star.gif
Binaural Barracade Against The Audio Police

by John Sunier

Being heavily into headphones, I couldn’t resist having my curiosity aroused by Tom Corbin’s first column [in a past issue] announcing that he will suggest circumstances under which one may want to wear two pairs of headphones simultaneously. Well, I can’t imagine what circumstances those may be and am waiting with bated breath to find out, but in the meantime I can tell you about some circumstances you probably had not thought about in which you might want at least to wear one pair of headphones.

Tom’s “Audio Police” business also caught my eye and I couldn’t agree more. I’ve railed against some of the Audio Police dogma for years, such as the “hair shirt” approach to component features, especially dispensing with headphone jacks (since I’m into headphones) in preamps, not to mention tone controls. I’m going to do a bit of creative, lateral thinking such as Tom was encouraging, and among other things I’ll also give you a rock-solid reason why you should buy a graphic equalizer.

ROOM TREATMENT & THE SWEET SPOT

Rumors are that one of the leading very high end speaker exhibitors at Hi-Fi ’97 bragged about how great his speakers sounded without any acoustical treatment in the small and sonically-deprived room of the San Francisco hotel where it took place. Yet a little snooping after the demo revealed Tube Traps in the front corners and a bunch at the rear wall.

While both the Audio Police and those of us who prefer to think and hear for ourselves stress the importance of the listening room in the high end equation, it is the former, not the latter, who have escalated the ritual of room treatment to new complexities and expense. Many audio buffs buy more room treatment materials than they need, or entirely the wrong ones, because they don’t sit and listen while trying simpler, less ugly and cheaper means such as rugs, drapes, furniture, or CD/LP storage shelves.

Another problem connected to the room treatment emphasis is the narrow sweet spot encountered with many of the larger and most expensive tower and panel speaker systems. Loss of 50% of the sonic achievement of a typical large high end speaker when standing up from a seated position is not at all an unexpected occurrence. Even moving from side to side a few inches destroys most of the superior imaging and soundstaging of many two-speaker setups. How many of us can sit next to a friend or spouse and be assured that the other person is hearing exactly what we are hearing in our carefully-aligned sweet spot? OK, so the majority of the audio unwashed out there has never heard of the idea of sitting equidistant from the two speakers in an equilateral triangle and thus has one speaker horizontal at floor level in one corner with the other vertical high up on another wall. The Audio Police have gone too far the other way – resulting in some of the listening room diagrams appearing in some audio pubs looking like a prison cell with a kitchen chair two-thirds of the way back, two speakers one-third of the way into the room, one little equipment cabinet to one side, and nothing else.

And in these ruminations on the sweet spot I’m not even addressing those approaches that REALLY have a narrow sweet spot – namely processes attempting to cancel some or all of the left speaker signal from reaching your right ear and the right speaker signal from reaching your left ear. (There used to be a specific name for this but it is now trademarked so I can’t use it). Among these are Carver Sonic Holography, Polk SRDS speakers, Lexicon Panorama circuit, and many new computer-related speaker-processing approaches that attempt to give a “3D” feeling to stereo sources heard through them.

In the computer area, I’ve never understood why all the research and effort are being expended to getting a 3D effect with dinky little speakers (and often a third little box laughably referred to as a “subwoofer”) when the computer user isn’t going anywhere and doesn’t require any freedom of movement. This is a perfect situation for headphones! Even inexpensive models can achieve better sound than the undersize speakers being sold for multimedia use; but better than that, headphones plus Binaural sound can precisely locate sounds anywhere in a full 360-degree sphere around the listener.

EVERYTHING YOU’RE LISTENING TO IS WRONG!

More than 200 million headphones were sold over the past decade, yet everything that nearly everyone is listening to on headphones was never designed nor intended for headphone playback – it was designed for loudspeaker playback! Stereo purposely mixes some of the left channel signal into the right and vice versa, and then when your pair of speakers are speaking in your listening room they do the same thing.

The result on headphones is what’s sometimes referred to as the “musical hat” effect – all the sounds happen inside your skull. Not only that, but half of the musicians seem to be clustered over just inside your left ear and the other half of them over just inside your right ear. Some people also hear another cluster in the middle of their cranium. The HeadRoom circuit offered by that headphone-oriented mail order service tries to connect these clusters via cross-feeding of the two signals to more closely emulate the effects of loudspeaker listening when wearing headphones. For many listeners and some types of music this subtle circuit enhances the listening to stereo material.

biphonic.gif
Biophonic Response Chart

[Vertical Scale = relative level in dB; Horizontal Scale= frequency.
Ron Cole feels this EQ can make listening to standard stereo sources on headphones
less bizarre-sounding to most persons, though not equalling true binaural.]

Here is a less subtle enhancement for listening to all these recordings and broadcasts that were never designed for headphones. Binaural recordist Ron Cole came up with this chart which corrects for ear canal resonance and other differences in the spectrum between speaker listening and headphone listening. It can be set up on a parametric equalizer or almost any multiband equalizer (those accessories which the Audio Police tell us should never have been invented). You don’t have to hit the various boost points right on the button — even getting close makes an amazingly more natural headphone listening experience when using stereo source material. While I have yet to try this in combination with the HeadRoom circuit, the two should be a synergistic duo. Remember though that neither of these band-air approaches locate the music outside of one’s head nor do they impart a “you-are-there” feeling in listening on headphones.

THE BINAURAL RAP

There’s only one way to do that. That’s using true binaural recordings and any headphones. [Editor: Auralization processors will also image outside the head.] Here again we are at odds with the Audio Police since absolutely no additional components are needed. Plus the ultimate in fidelity is not required to experience binaural recordings. The very first public experiments with it, in fact, took place at the Paris Opera in 1881, using primitive carbon transducers both on the stage and a pair of them hooked to two separate telephone lines at each subscriber’s home.

Even with a $25 walkman-type cassette portable and the ear-buds that came with it, one can have a jaw-dropping sonic experience with a good binaural cassette. One that I frequently suggest to binaural virgins is Stephen King’s “The Mist,” available at the Simon & Schuster audio book rack of most chain bookstores for about $9. It’s more hair-raising than any King movie. With a cast of about 30, original sound effects and music, you’re part of the horror drama. Monsters creep up on you from behind and drop down from the ceiling on you.

But it is with music that binaural can almost literally Take You Away. Isn’t the primary purpose of high end audio to Get Into the Music More? (The Audio Police may say that but their actions often contradict that.) Well, with binaural one is in the same venue where the musicians originally performed. One is aware of the room size and shape, and all the reflections that are such a major part of the musical experience are preserved instead of being turned into a general mish-mash of reverberation without any directional information, as with stereo.

The basics of binaural couldn’t be simpler, but recent improvements have brought it to such a level of viability and functionality that if recording engineers would only wake up to it they would be recording everything binaurally. It is now completely compatible for mono or stereo speakers as well as matrix surround sound playback.1 The heart of binaural is a dummy or artificial head which replicates the human head. The most vital features on it are the two outer ears or pinnae. They are usually formed out of soft rubber or plastic and often cast from actual human ears. Ridges and valleys in the pinnae reflect the sounds differently into the inner ears and therefore they are vital to recreating precise localization of sounds. The current interest in spherical mike systems for stereo preserves many elements that are part of binaural reproduction, but without the pinnae to reflect the incoming sounds to the omni mike capsules, the localization cannot be very specific.

The two channels from the dummy head must be kept absolutely separated all the way in the chain to the two drivers of the listener’s headphones. And the left mike on the dummy head must feed the left driver of the headphones and vice versa; the backs of our heads lack the features of the front and reversing the channels gives a confusing sonic image much as does reversing the left and right-eye images of a stereo photograph.

While even a $3.98 pair of ear buds will deliver good binaural, the better quality your headphones, the better will be your experience. We already know that it’s possible to get better sound with some of the high end phones2 than one could get with many of the most expensive speaker systems. Add binaural to that equation and you have a really amazing sonic experience. Add one of the many dedicated headphone amps now being produced3 and you’ll be hearing the ultimate. Add a longer cable and you’re no longer glued to that sweet spot! You can now take it with you, within reason.

TODAY’S BINAURAL

The Audio Police have decided that FM radio, audio cassettes and binaural are all not worth our consideration as far as high fidelity sources. I could expound at length on the idiocy of the first two, but that’s off the subject. Their beef with binaural is the claim that it sounds perfectly awful played back on loudspeakers. In the distant past that was somewhat correct; binaural recordings sounded a bit thin and distant. Part of this was the very poor bass end sensitivity of the consumer mikes, which were often built into headphones and had to have a low cutoff to avoid feedback! Even the recently-discontinued Sennheiser MKE 2002 binaural mikes lacked extended low end.

Today, however, the two commercial binaural mike systems used in 99% of existing binaural recordings are completely equalized for excellent speaker playback. After the first of the two gold binaural CDs from Newport Classics was released, a press event was held in the same auditorium in Pasadena where the recording was made. Speakers placed on the lip of the stage played back the binaural CD and all agreed it sounded as good or even better than the best standard stereo CD. 4 (Of course most of the “you-are-there” feeling is lost in speaker playback.)

The other binaural misconception is that there are no recordings available. Not true. They were extremely difficult to find, and when I began regular All Binaural Broadcasts on my local AUDIOPHILE AUDITION program about 17 years ago listeners reported that they asked in shops about binaural recordings but only got blank stares. So seven years ago I decided to start THE BINAURAL SOURCE, which is a web-based mail order business currently stocking over 125 different true binaural CDs and cassettes. Most of these are imported exclusively by us from Germany, France, Britain, Bulgaria, Japan, not to mention a growing number of small U.S. labels who lack distribution in the stores. The sounds cover classical, pipe organ, jazz, crossover, new age, pop, audio dramas (such as “The Mist”), nature sounds, and special sounds to enhance sleep and relaxation.

An extensive FAQ and more detailed information about binaural reproduction are found at THE BINAURAL SOURCE. Actual binaural demos for free downloading will be available there by the time you read this! A flyer describing 28 new binaural CDs and listing all 125+ recordings in the current catalog is available by calling 800-934-0442 (PST), emailing your street address to sunier@binaural.com or by writing to THE BINAURAL SOURCE, Box 1727, Ross, CA 94957.

EARNOTES:

1 = I realize most LISTENER readers are staunch two-channel/two-speakerists, but if you buck the Audio Police by owning any sort of matrix surround sound processor (no DSP reconstructions, please), you will find that binaural CDs provide a superior surround soundfield to any Dolby Surround-encoded music CD.

2 = Among my personal favorites for binaural are the AKG K 1000, the Jecklin, Sony CD-3000 and any of the Grados.

3 = Headphone amps have been available from HeadRoom, McCormack, Audio Alchemy, AKG, Melos, EarMax, Creek. New headphone amps have been introduced by Musical Fidelity, Parasound, VLS, Sennheiser, Holmes·Powell, Moth Audio, Celeste, Pure Audio, Mesa Engineering, Naim and Bowman.

4 = Fellow audiowriter Martin De Wulf said this about the second Newport gold binaural CD in a recent Bound for Sound issue: “…while this recording does do some amazing, almost unbelievable things when listened to on a set of headphones, it sounds every bit as good when listened to through a pair of speakers.”

c. 1997, John Sunier.
From The Binaural Source. (Republished with permission.)

A Dialetic of Audible Space.

by Ian Stevenson

What follows is a free ranging discussion of some aspects of the use of space in musical performance. Although my interest is primarily in the use of spatialisation or three dimensional physical space, I will touch on other aspects of space as it relates to musical experience. In order to establish some coherence in my presentation I have attempted to develop an argument around the potentialities of audible space.

SECTION 1 – SPACE AS A COMPOSITION TOOL

Space has been an element in Western musical performance from at least the middle ages. The antiphon in Gregorian chant with its characteristic call and response between voices became the prototype for antiphonal composition of various types in the Baroque and Classical periods and beyond. The often quoted cathedral of St. Mark’s in Venice, with its spatially opposed organs was the site much development in the late Renaissance / early Baroque, of the antiphonal devices especially associated with the Gabrielis, Andrea (c1533-1585) and his nephew Giovanni (c1555-1612). In this polyphonic style the various melodic lines are presented by spatially distinct choral and instrumental groupings. Other famous examples of the use of spatial effects include the antiphonal choral effects in J.S.Bach’s (1685-1750) St. Matthew Passion (1727/29) and W.A.Mozart’s (1756-1791) Serenade in D for 4 Orchestras (K286 1777) with its motivic interplay between spatially separated instrumental groups. The inevitable spatial effects of Mahler’s Symphony No.8 in E flat ‘Symphony of a Thousand’ are maybe more a result of the sheer expanse of performers than an effect by design. The spatial location of musical sources has often been a concern in the theatre. There are many examples of on or off stage bands in opera, here the concerns are clearly with the shaping of the dramatic action. However, musical space has clearly been an area of interest for a wide range of composers within the Western Canon.

The age of the machine brought new inspiration for defining space with sound. The ‘intonarumori’[1] or noise instruments of Luigi Russolo (1885-1947), inspired originally by the sounds of war, where designed to project noises into an auditorium. His futurist manifesto ‘The Art of Noises’ rejoiced in the acoustic and spatial character of the modern mechanised environment. The potentially liberating invention of the loudspeaker held a unique fascination for composers inclined toward modernism. It was not until after the second world war that the use of loudspeakers in musical composition became more common. The use of the tape recorder as an adjunct to acoustic instruments has become common, however electroacoustic composition with space as an integral musical component is a distinct form. Some of the more famous examples are as follows: Karlheinz Stockhausen (1928- ) Gesang der Jünglinge 1956 includes five loudspeaker locations, Kontakte 1960 includes a four track tape. The Philips pavilion for the 1958 Brussels world fair, designed by Iannis Xenakis (1922- ) and Le Corbusier (1887-1965) included an 11 channel 425 loudspeaker sound system for which Edgar Vàrese (1883-1965) composed Poème Electronique 1958 and Xenakis produced Concret PH 1958. Stockhausen produced various pieces for the German pavilion at the Osaka EXPO 70. The pavilion was a geodesic dome with loudspeakers at every vertex and integral sound control equipment. EXPO 70 also included the 800 speaker installation in the Japanese Steel pavilion. This system was used by Xenakis for his 12 channel composition Hibiki Hana Ma. The idea of introducing the spatial complexity of an orchestra into electroacoustic performance has been explored by the Groupe de Musique Expèrimentale de Bourges with their multi-loudspeaker Gmebaphone (1973-). A similar idea is seen in the Acousmonium (1974-) of the Groupe de Recherches Musicales. Pierre Boulez (1925- ) utilised a multi-speaker system suspended in the auditorium for his Rèpons.

There are innumerable other examples of the exploitation of technology to achieve an integrated spatial dimension to musical composition. In the field of popular music, multitrack recording and stereo reproduction has made the inclusion of a spatial dimension common place in music production. From the earliest clumsy uses of the stereo sound stage in records such as The Beatles Sgt. Pepper’s Lonely Hearts Club Band[2] , where instruments are placed either to the right or left channels for effect, to carefully placed spatial deployment of instrumentation in records such as Donald Fagen’s The Nightfly[3] , a set of conventions for the use of space has been established. These conventions are often strictly adhered to, as are the conventions of instrumentation in popular music.

In writings on the Western musical tradition, space and motion are often used metaphorically. Motion is a device for musical expression and as such has become a musical paradigm. Musical space is often measured in the dimensions of pitch, harmony, texture and rhythm or time. Musical motion occurs within this space. In addition to this usage of space, much musical discussion is imbued with dynamic qualities of human emotion. These ideas have contributed to the multilayered, metaphoric connotations of space whose relations are wholly paradigmatic or associative.

Traditionally, musical aesthetics has dealt with the issues of meaning and aesthetic value. I would like to look at some contemporary perspectives on the use of space in electroacoustic music. Much in musical language is arbitrary and its function rests on convention. It is likely, however, that our auditory perception of space and its relation to meaning is grounded in every day experience of the physical world. Moreover, the expressive gap filled by the metaphor of motion in music may be closed when actual spatial motion becomes a part of compositional practice.

One of the characteristics of Modernism in music is the rejection of theories of expression which characterised Romantic music. Musical Expressionism turned inwards and from the extremes of subjectivism, total abstraction was born. Serialism and other devices were employed to rid music of the extrinsic burdens of music history. This tendency toward musical abstraction has been fuelled by the creation of totally synthetic instruments. Electronics and computers operate in a sonic continuum that spans reproduction of real acoustic events to unimagined artificial sounds. The interplay of levels of abstraction, both in a traditional melodic / rhythmic sense and in terms of sonic material has become a device used in electroacoustic composition. Spatialisation has been used to effectively articulate these levels of abstraction. This form of compositional device is particularly evident in the music of Natasha Barrett, Earth Haze 1996[4] for instance employs a sort of phrasing of spatial perspective that underlines the evolving abstraction of the material. Another use of space in musical performance is employed by Stockhausen in Gruppen 1955. Stockhausen uses three orchestras situated around the audience. In this piece he attempts, according to Worner[5] , to establish a polyphony in time and in space. Here we see space compared with the traditional compositional elements of pitch, harmony and time. Polyphony of space suggests the interplay of two or more sound spaces as well as space being one of the musical properties of a melodic line. Stockhausen adopts a seemingly formalist approach to space. For him the property of space is an entirely intrinsic property. He uses space in order to better articulate the temporal complexities of his composition.

Wittgenstein’s[6] discussions on musical understanding may help to shed some light on the contrast between the abstract and the referential in musical language. Wittgenstein suggests that understanding a musical theme is easier than understanding a sentence. This is because the music does not bear complex relations of linguistic referents that are found in the words of a sentence. Still we understand a sentence in much the same way we understand a musical theme. Space like other musical parameters does not bear semantic meaning and yet we can interpret audible space by applying our experience and an innate or learned set of governing rules. For Wittgenstein music is highly abstract and yet we understand it by understanding the system of rules within which it operates. Our ability to understand audible space is a product of our experience and understanding, in Wittgenstein’s terms, this implies a degree of expertise. This is true of both language and music. As I suggested earlier the relation of space to meaning is likely to be grounded in our experience of the physical world. Much thought has been applied to analysing aural experience. Work with specific relevance to audible space is presented by Denis Smalley[7] in a paper entitled ‘The Listening Imagination: Listening in the Electroacoustic Era’.

In this illuminating paper, detailing modes of listening applied to electroacoustic music, Dennis Smalley includes space as one of his ‘indicative fields’. He posits the argument that musical apprehension of sounds exists on a continuum between merely informational use of sound and a more aesthetically involving, interactive engagement with the subtle qualities of a sound. Space as an integral component of sound exists on this continuum, though he categorises it amongst those elements which are indicative of relationships external to the sound itself.

He argues that the listeners response to these extrinsic relationships cannot be guaranteed and are dependent on the experience or expertise of the listener. In this regard we can see similarities with Wittgenstein’s explanation of the relation of musical and semantic meaning discussed above. As outlined above, the paradigmatic relation between music and motion is central in the language used to discuss musical sound. Smalley explores this and includes ‘energy and motion’ as one of his nine indicative fields. In his discussion of space he sets aside the use of space as an aid to the articulation of structural and spectro-morphological (relating to the formal evolution of sonic spectrum) aspects of a composition. These aspects of space are those which lie within the interactive relationships between the listener and musical sounds. His discussion centres on the indicative character of space and its interpretation by the listener.

He begins his discussion by outlining the difficulties associated with the potential contrast in acoustic properties of the spatial environment described within the composition and those in the listening space. He describes the indeterminacy arising from what he calls the ‘superimposed space’ which is the combination of the properties of the composed space and the listening space. This may result in the alteration of the indicative interpretation of the piece.

Smalley describes three indicative properties of space. The principal property is ‘spatial texture’. This concerns the topology of the audible space. Size, he argues, is the most important indicative property. It may express a range of meanings which are fundamental to human experience: he outlines the contrasts between ‘intimacy and immensity’ and ‘confinement and vastness’. He suggests the psychological or emotional states that may result from either of these extremes. Other aspects of spatial texture include the density of distribution of sounds, the spatial contiguousness of sounds and the movement of sounds.

The second spatial property which may bear meaning is ‘spatial orientation’. He employs the metaphors of ‘sound confronting from ahead or stealing up from behind’ to describe the potential of spatial orientation. Interestingly, he follows Wishart[8] in suggesting that there is no differentiation between left and right. This position is countered by Truax[9] and Wallin[10] as I will outline later. He does, however, include the case of circumfrentially enclosing sound which Wishart conspicuously excludes from his seemingly exhaustive enumeration of spatial possibilities.

The final spatial property in Smalley’s exposition is ‘temporal space’. This describes the evolution of space over time resulting in impressions of stability, permanence or rapid change. Smalley coins the term ‘spatio-morphology’ to describe the evolution of the spatial components, described above, in electroacoustic composition.

In the chapter on spatial motion in his book ‘On Sonic Art'[11] , Trevor Wishart goes to great length to enumerate the various geometric possibilities of spatial motion. His stated objective is to analyse the vocabulary of spatial motion without attempting to define its language. He does, however, comment on the meaning-bearing aspects of each type of motion. He denies that beyond the subtle aspects of left and right handedness, there can be any significant differentiation between sources coming from or moving to either side of the listener. This position is refuted by N. C. Wallin in his book ‘Biomusicology – Neurophysiological, Neuropsychological and Evolutionary Perspectives on the Origins and Purposes of Music'[12] in which he details the functional asymmetry of the hemispheres of the brain and its influence on the perception and processing of musical sound. Barry Truax[13] takes up this point. He details the role of the two hemispheres in the different levels of hearing that may be involved in the perception of different sounds. The location of the speech function in the left hemisphere and this hemisphere’s popular association with analytical processes stands in contrast to the supposed synthetic and associative powers of the right hemisphere. These factors may be viewed in relation to the fact that unlike the other senses, hearing is processed by both hemispheres with the slight dominance of the opposite hemisphere. Truax cites research[14] that indicates that signals presented to each ear may be processed with access to the different faculties dependent on the hemisphere in question. Obviously, neurophysiology is a rapidly evolving field and these factors are the subject of current and controversial debate.

The points of view presented above indicate a strong belief on the behalf of contemporary composers that space can be effectively and meaningfully employed as a composition tool. This belief is born out in a great multiplicity of compositions in which space takes a predominant and sometimes central role.

SECTION 2 – THE MUSICAL MEANING OF SPATIALIZATION

Trevor Wishart’s descriptions of spatial motion and their potential meanings in musical language rely, as he says, on the apparent location of the sound object being unequivocal. This, however, is often not the case. The difficulties, as outlined by Denis Smalley above, of spatial superimposition due to the complexities of room acoustics and replay systems often work against spatial localisation. Added to these difficulties are the psychoacoustic limitations of spatial perception, for instance, limited spatial resolution of low frequencies and perceived front/rear reversal resolved only by head movement. These factors introduce a highly equivocal character to the physical aspects of spatialisation. In addition to these practical considerations must be the general difficulties of divergence between the composers intention and the audiences interpretation. The fact that understanding audible space is rooted so strongly in the every day experience of the individual, implies a ‘death of the composer’[15] leaving only what Barthes might have called active interpretation on the part of the listener. Without a fixed signified, audible space is reduced to an arbitrary sign with only a field of potential meanings for the listener to operate within.

The formalist approaches to musical meaning of space, as exemplified in my reference to Stockhausen above, imply that space is an intrinsic musical property. For those who deny that such ideocentric approaches are valid, the convergence of meaning in composers intention and listeners interpretation is very limited. From this deconstructionist point of view, the meaning in audible space would be almost entirely equivocal.

The argument represented by my references to Wittgenstein, imply that understanding a musical idea requires an understanding of the syntax and vocabulary of the musical system. It is not clear that any such fixed structure exists in the case of spatialisation. We may have extensive experience in the field acoustic spatial perception, but our analytical expertise may not necessarily be equal to that of the composer.

It is apparent that there is no guarantee that the composers intentions will be transmitted to the listener. There are a range of practical and theoretical difficulties associated with the use of audible space as a musical device.

SECTION 3 – CONCLUSION

Clearly, any meaning that may be associated with the spatial elements of a composition cannot be absolutely fixed. This will be case with most musical properties of a composition. This does not mean, however, that listeners cannot share a common experience or interpretation of audible space. Or, indeed, that the composers intentions will not, in some form, be perceived by the listener. Obviously, the fact that space has been employed successfully by so many composers in the past, and that it continues to be explored as a musical device, means that it has earned its place in musical language and will surely continue to grow in importance. Theoretical interest in the use of space in composition has occupied much space in the literature of contemporary music. Analysis of its use and exploration of its potential by theorists and composers presents great scope for research and development.

The technical difficulties outlined above are being continually addressed by research and advanced electroacoustic practice. Great progress is being made both in the predictable use of electroacoustic devices and in the treatment and control of acoustic spaces. New auditorium designs, sensitive to the needs of electroacoustic performance must surely help to narrow the gap between the composers spatial design and its performance realisation. New techniques for spatial encoding and advanced signal processing[16] for multi-channel playback are presenting a viable way forward for the development of spatial composition. These developments do not inhibit the performance of live sound diffusion, where this is seen as the aesthetically appropriate approach to the realisation of the inherent spatial properties of a piece. On the contrary, they will provide the performer with new and flexible tools and enhance the expressive possibilities of this form of live interpretation.

Being aware of the limitations and potential pitfalls of spatial expression can only improve our understanding of this exciting dimension in musical language. This understanding must help us to explore the wealth of musical material that exploits audible space and open the horizons to new and innovative work in the future.

Notes/Bibliography

1. Goldberg, R.1979 ‘Performance Art – From Futurism to the Present’ Thames and Hudson, London
2. EMI Parlophone 1967,EMI Records 1987 CDP 7 46442 2
3. Warner Brothers Records 1982 7599-23696-2
4. Nota Bene Records 1997 N.B. 970101M
5. Worner, K.H. 1963 ‘Stockhausen – Life and Work’ Faber and Faber, London
6. Worth,S.E 1997 ‘Wittgenstein’s Musical Understanding’ The British Journal of Aesthetics 37:2
7. Smalley,D. 1997 ‘The Listening Imagination: Listening in the Electroacoustic Era’ Contemporary Music Review 13:2
8. Wishart,T. 1985 ‘On Sonic Art’ Imagineering Press, York (See 1996 Ed. Simin Emmerson)
9. Truax, B. 1984 ‘Acoustic Communication’ Ablex Publishing Corp., New Jersey
10. Wallin,N.L 1991 ‘Biomusicology – Neurophysiological, Neuropsychological and Evolutionary Perspectives on the Origins and Purposes of Music’ Pendragon Press, Stuyvesant N.Y.
11. Wishart (1985)
12. Wallin (1991)
13. Truax (1984)
14. Truax (1984) pp. 53-54
15. I have borrowed from Barthes,R. 1977 ‘The Death of the Author’ in Heath,S. Ed.,‘Image Music Text’ Fontana Press London
16. for exciting developments see http://www.ircam.fr/produits-real/logicels/spat-e.htm, http://www.ircam.fr/activities/recherche/cou-salle.htm referred to in a thread of the 3-D Audio mailing list correspondents: Jean-Marc Jot – Room acoustics team, IRCAM and David Malham – Music Technology Group, University of York

c. 1997, Ian Stevenson.
From Audile Paradigmatics. (Republished with permission.)

Seven Darn Fine Reasons to Own a Headphone System Too!

by Doug Schneider (SoundStage!)

Note that in the title I said too. Although some people use headphones exclusively, I’m addressing this to those people who, like me, have a full home system. Why? Because a supplementary headphone system can add enjoyment to the music-listening experience and take you places your home system won’t allow.

Now first let me get something straight: My home headphone system is nothing grand. We’re simply talking about a Denon DCP- 70 portable CD player (can’t handle any bump and grinds whatsoever, but it is one of the rare players that sports a digital output) and some Grado SR-60 headphones. That’s it, that’s all, and for now that’s just what I need. But it’s now a valuable part of my life, and here are some of the reasons why.

 

  • First and foremost, we all don’t keep the same hours. I’m not talking about you and me. I’m talking about the person sleeping in the next room at this very moment. And no, this isn’t some sick fantasy about a neighbor-it’s her, the person sharing my rent, food, and life! Although I rise (and am expected to rise) when my unofficial spousal unit does, late-night hours reading and browsing the ‘net, as well as writing stuff such as this usually mean I’m awake much later than she is (or most other people are). My neighbors don’t care if I play my stereo after 10, but SHE certainly does. Without my ‘phones, I’d be screwed. I’d never get to listen to half the discs I have. Well, “up yours,” I say! With ‘phones you’ve got your own hours and can at least reclaim and live out a valuable part of your life.
  • Apartments, or other such small dwellings, usually equal a cramped life. My listening room also serves duty as a living room, TV room, computer room, beer room, hanging-out room, etc. I can certainly see the purpose of a 15-room mansion since single-room multi-tasking just isn’t all that practical. So when someone else calls room dibs and is watching the tube, reading, drinking, sleeping, or whatever, music is usually out for the Douger…until…now yer gettin’ the picture.
  • Movies sound better through your headphones than through crappy TV speakers. You guys with home theaters can ignore this, but for others like me-well, this discovery happened quite by accident when Doug’s Other pulled the usual “call it quits early” again. It looked as though I just wasn’t going to be able to watch Leaving Las Vegas with any appreciable volume. But I plugged the Grados into my VCR’s headphone jack and presto, wayyyy better full-stereo sound than the Sony box can crank out on its own.
  • Long-distance traveling becomes a breeze. Endless hours jiggling in a car or airplane seat and being forced to listen to someone else’s choice of tunes becomes a thing of the past. Just stock up on batteries and get ahold of Headroom so you can get yourself a full-fledged, full-function traveling pack to haul your portable music center around the world with the least frustration possible.
  • Sometimes you just need your own space. Nothing can piss off avid audiophiles more than someone talking to them while they’re trying to enjoy some music. Headphones give you an excuse to ignore such people. They don’t know whether you can hear them or not, and they can’t tell. If you can hear, who cares? Just pretend you don’t and smile whenever they talk. After a bit, they’ll get the subtlety of your hints and you’ll have all the time you need.
  • A headphone system doesn’t cost that much. I did it for less than $250 bucks. It could even be a lot cheaper, or certainly a lot more. I say start cheap but keep expansion in mind. I can’t think of better reasonably priced ‘phones than the Grado SR- 60s. Other people dig some of the low-price Shack models. Your expansion will come through your player-if you need one. Heck, if you have a headphone jack on some of the gear, you’re off to the races (although the portability factor is gone). But remember, in time you may want to add an external headphone amp like those from Headroom. If you don’t know why you would want one, just give one a listen to and you’ll understand. Almost all Headroom models absolutely kill a portable player’s headphone output, or even the jack on your CD player or preamp. And if you’re lucky to have a digital output, you can add an Audio Alchemy DAC-MAN or something similar to improve your player’s sound significantly. Ahhh, separates for headphone listening….
  • And finally, headphones can sound darn good. That’s right, sometimes music is better served through headphones. And you need something on hand just in case music like that comes along.

 

If you do go ahead and do something along the headphone route, don’t forget to drop me a line to tell me how you made out.

c. 1998, Doug Schneider.
From SoundStage!. (Republished with permission.)

Headsets help tune in to productivity.

cagle1
by Karl Leif Bates
The Detroit News (12/15/95)

Office workers should tune in and turn on, according to a University of Illinois researcher.
Employees who are allowed to wear personal stereo headsets show higher productivity, better attitudes and greater satisfaction with the workplace, says Greg Oldham, a professor of organizational behavior.
And they don’t have to fight over which radio station to play on the public address system.
Oldham gave 75 out of 256 workers at a large retail company the personal stereos to wear at work for four weeks and then measured the results.
Headphone-wearers exhibited a 10-percent jump in productivity and were “less nervous, less fatigued, more enthusiastic and more relaxed at work than the people in the control group,” Oldham said.
“They do seem to be more comfortable and relaxed,” said Paul Wilson, a safety specialist for the U.S. Postal Service in Detroit, where headsets are allowed for some workers.
Of course, not everyone can wear stereo headphones at work, Wilson cautions. “They can wear headsets as long as they’re not around moving equipment,” he said. “And we tell them not to turn them up too loud. We don’t want them to go deaf.”
Employees who talk on a phone frequently or work in teams also should ditch the diversion. “Most of our people have headsets on already, but they’re not listening to music,” noted Ameritech spokesman Jonathan James.
Workers in Oldham’s study reported listening to their tunes for an average of 20 hours in a 36-hour workweek and favored oldies and country.

Article c. 1995, from The Detroit News (republished with permission).
Cartoon c. 1998, Daryl Cagle, from Daryl Cagle’s Professional Cartoonists Index. (Republished with permission.)

A Bicyclist’s Sense Of Hearing: How Important?

by John S. Allen

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Other than warning about loose parts on the bicycle, what can the sense of hearing do for a bicyclist, and what can it not do?

There’s a lot of confusion on this subject. It’s often said that hearing is the bicyclist’s second most important sense, after sight. Well, not exactly. This statement neglects the sense of balance, the sense of touch and the kinesthetic, proprioceptive sense (sense of body positioning), which actually make it possible to ride a bicycle — even with your eyes closed. (See note 1 below). After these senses comes sight, which makes it practical to ride where there are things you might run into. But how far behind sight does hearing come?

In order to answer these questions, I’m temporarily going to trade my bicycle helmet for an engineer’s propeller beanie. (See my curriculum vitae if you wish to review my qualifications.)

Hearing: Sometimes Helpful, But Unreliable

In quiet (typically, rural) surroundings, the sense of hearing can sometimes alert a bicyclist to a motor vehicle, a charging dog or another potential hazard before the bicyclist can see it. Usually, the unseen hazard is either behind the bicyclist, or obscured by vegetation or another obstacle. A bicyclist may sometimes hear a car a mile away under ideal, quiet conditions, upwind and on level terrain or across a valley. But especially when riding into the wind, bicyclists are often surprised by motor vehicles overtaking them, and even more often by other bicyclists overtaking them. The refraction of sound waves by moving air works against the bicyclist in this situation, and so does wind noise.

The sense of hearing has a resolution of about +- 3 degrees for sound sources directly to the front or rear. At other angles, the resolution is poorer, since the timing difference between the two ears changes less rapidly with the angle of the sound source. At 50 feet (15 m), less than 2 seconds before the car reaches the bicyclist at a speed difference of 20 mph (30 km/h), +- 3 degrees amounts to a 6 foot (2 m) range of possible positions. This is in addition to the uncertainty as to whether the major noise source, the exhaust pipe, for example, is on the right or the left side of a vehicle.

Even under quiet conditions, then, the best that the sense of hearing can do is to provide an unreliable warning of a vehicle’s presence, and an inaccurate idea of its position. And while the sense of hearing can indicate that something is there, it can not indicate that nothing is there. Bicyclists learn very quickly not to trust their sense hearing to warn them before turning or changing lane position.

Under noisy urban conditions, the sense of hearing can not often provide an early warning, though often it does provide information about nearby vehicles. On a crowded street, only especially loud sounds such as car horns can provide an early warning.

It is not surprising, then, that the right-of-way rules in the traffic law are based on the sense of sight rather than hearing. A vehicle operator’s only hearing-related duty under the traffic law is to respond to special warning devices: horn, siren or bell. Despite this duty, no laws prohibit deaf persons from operating either a motor vehicle or a bicycle. Not only this, the only laws restricting sound systems on or in a vehicle are intended to reduce disturbance to people outside the vehicle. That is, except for except for laws which prohibit headphones. More about headphones later.

Contrast the facts I have just recited with the distorted, popular view of the role of the sense of hearing for bicyclists. This view is based on several assumptions, namely:

1) The incorrect assumption that bicycling is inherently very dangerous, and the related assumption that safety always outweighs all other considerations, for example bicyclists’ enjoyment of their sport or their need to communicate.

2) The assumption that a bicyclist can and should be held responsible for actively avoiding accidents for which the sense of hearing provides a warning;

3) The assumption that the sense of hearing is useful and reliable enough that it is essential to safe bicycle operation.

These assumptions most commonly are expressed as condemnations of headphone use while bicycling. Let’s turn to the headphone issue now.

Types of Headphones

There are three major types of headphones. They differ greatly in their effect on hearing of sound from outside:

1) Circumaural or “sealed” headphones. These form an airtight seal against the sides of the head, and greatly attenuate sound from outside. They are preferred in noisy environments such as an airplane cockpit. They once were popular for high-fidelity sound reproduction, but they are heavy, bulky, uncomfortable and sweaty, and with better options available, they are much less widely used now. They are very rarely used with portable sound equipment.

2) Supraaural or “open-air” headphones. These rest on the ear but form no seal. The conventional telephone earpiece is a common example, and so are most headphones used with portable sound equipment.

When supraaural headphones are used for high-fidelity sound reproduction, precise spacing of the headphone transducer from the ear is essential for predictable low-frequency response. The spacing is controlled by an open-cell foam pad which is transparent to sound from the headphone transducer and also to sound from outside. Sound from outside the headphone is attenuated slightly by the bulk of the transducer assembly and much less by the foam which surrounds it.

Small supraaural headphones 2 or 3 cm across, the most common type used with portable stereos, have very little effect on sound from outside — about as much as if you hold up two fingers next to each ear but not touching it. (Try this.) Such headphones produce essentially no hearing impairment, if silent, and increasing impairment the louder they are played –just as with a loudspeaker.

3) Intraaural or “in-the-ear” headphones. Hearing aids commonly use these. The effect of “in the ear” headphones on sound from outside to depends on their construction. Some intraaural headphones plug the ear canal, while others leave it partially open to the outside. Even a small opening will let most sound from outside pass.

A few headphone models electronically cancel out some of the outside noise, mostly in the low-frequency range. These headphones are expensive and uncommon, and they all have a switch to turn off the noise cancellation.

Headphone laws

Several states have laws prohibiting headphone use by motor vehicle operators and/or bicyclists.

Some of these laws permit headphones which cover one ear. The idea behind these laws is that the other ear will then be able to receive sounds from outside. To be consistent, these laws should in principle also allow the wearing of only one earmuff in cold weather, though somehow, nobody has thought of banning earmuffs. One-ear laws don’t make scientific sense, since a single headphone can actually have worse effects on hearing than binaural (two-ear) headphones. The desensitization of one ear by a single headphone played loud enough to cut through background noise changes the apparent location of sound sources. This problem is much less likely with binaural (two-ear) headphones.

Except when very unusual recording techniques are used, all sound sources reproduced through headphones appear inside the head or at the ear(s), where they are difficult to confuse with other sounds. This effect is even more pronounced with binaural (two-ear) headphones, and allows the programming they convey to be intelligible at a lower volume.

The wording “covers the ear(s)” usually found in headphone laws is supposed to distinguish between headphones and loudspeakers, but it does so poorly. To “cover the ear(s)” is a visual concept, but the ears do not see, they hear. Open-air headphones do not cover the ears, impairing hearing, any more than goggles cover the eyes impairing sight or a scarf covers the nose, impairing the sense of smell.

It is also fair to point out that headphones have practical advantages and legitimate uses for bicyclists, more so than for other vehicle operators. This is, after all, precisely why headphones are popular with bicyclists. Headphones are lightweight and require very little electrical power to operate, important advantages on a human-powered vehicle. Headphones deliver sound to the bicyclist without disturbing other people. Headphones may be used for entertainment or to gather information unrelated to bicycling — listening to a news broadcast, holding a conversation via ham radio, auditing a correspondence course — but they may also be used for bicyclist-to-bicyclist communication. In this context, headphones make it possible to teach safe riding, give route directions or relay vital safety messages over a far greater distance and more reliably than by mouth.

Did you ever wonder why television news correspondents always appear on camera with a little headphone plugged into one ear? It’s because this eliminates the problem of feedback from loudspeaker to microphone. For the same reason, headphones make it possible for a bicyclist using a two-way radio to conduct a normal conversation, rather than having to shut off the microphone when receiving.

Headphone laws are very rarely enforced. Many bicyclists ignore them. But enforcement is not the only way that the law affects people. One important reason not to wear headphones — even if they are not playing — is that they make it harder to collect on an insurance claim after a crash.

The first question a bicyclist’s attorney should raise when faced with this problem is whether the bicyclist had any duty to act differently if alerted by sound. Only if this is true is it important under the law whether the bicyclist actually heard the sound. For example, if an overtaking vehicle strikes a bicyclist riding in the normal position on the road, the overtaking driver had the duty under the law to avoid striking the bicyclist. The bicyclist had no duty to swerve out of the motorist’s way, and it is unlikely that hearing the car would have made it possible to determine whether swerving was necessary to avoid a collision. Therefore, the wearing of headphones should not be an issue in such a case. A judge ought to prohibit it from being discussed in the jury’s presence — but a judge may not do this. I have seen cases lost over this false issue.

Conclusions

As I hope that I have shown, laws banning headphone use by bicyclists are based on inaccurate ideas about headphone design. These laws outlaw the special advantages of headphones for bicyclists, particularly for two-way communication. Furthermore, the bicyclist is unusual among vehicle operators in having good use of the sense of hearing. If we held all drivers to the standard of being able to hear well, the only street-legal motor vehicles would be quiet, unenclosed ones such as golf carts. A bicyclist’s decision whether to wear headphones — particularly, open-air headphones — and of how loud to play them, ought to be of as little concern in the law as is the question of how loudly a motorist may play a radio inside a car.

I think that it is important for a bicyclist to think carefully about when to use or not to use headphones, and I certainly don’t encourage playing them loudly. Not only does loud playing of headphones shut out the outside world, it can damage hearing. I agree that headphones (or any other extraneous sound source) can sometimes affect the safety of bicycle operation. But the role of headphones in causing bicycle accidents is, in my opinion, deeply confused by faulty assumptions about the sense of hearing, and by ill-conceived laws which place headphones in a special category separate from other factors affecting hearing.

***

1) (Don’t try this at home unless you are Bill Gates. If you do try it, you will probably find that you can ride just as steadily with your eyes closed as with them open.)

c. 1997, John S. Allen
From John Allen’s Home Office Home Page. (Republished with permission.)

Spatial Sound – An Overview.

by Kimmo Vennonen

It is easily confirmed that we hear sound in three dimensions and the perception of the spatial aspects of sound has been essential to our survival. For instance, ascertaining the location of a charging elephant, or crossing a busy city street both rely on this ability, called localisation. The ear-body-brain combination correctly decodes a handful of simultaneous and possibly conflicting spatial cues, often to within a few degrees of precision and in a fraction of a second.

The perception of music has always been an experience rich in spatial detail, but very much taken for granted due to its everyday nature. It is now acknowledged that the acoustic spaces music was performed in had a profound influence on the particular style. For example it is hard to imagine Gregorian Chant in an outdoors setting, or Balinese gamelan music in a cathedral.

The Invention of Stereo

The invention of sound recording in the previous century was a cultural milestone, bringing certain music to places, times and people it had never touched. The most primitive apparatus was an instant curiosity piece, yet the superiority of the live musical performance was rarely questioned. What was lacking in recorded sound was a sensation of ambience, a separation of the instruments and a perception of the context of the performance. By the early twentieth century a simple theory of human sound localisation had been developed, that enabled others to propose ways to convey this missing spatial detail.

Thus stereo was born, but it has not always been applied conforming with any stereo theory. For example, many audio practitioners are unaware that loudspeaker stereo relies on the conversion of intensity differences to phase differences around the head. Many sound engineers have still not adapted to stereo, preferring “multiple-mono” recording strategies. To some extent this is because the equipment makers have not produced appropriate hardware.

The Field of Psychoacoustics

Psychoacoustics is a field broader in scope than spatial sound, but there are many applications of it to this topic. Most practical spatial systems (including stereo) rely on psychoacoustics, endeavouring to create a natural impression, or an illusion of enveloping sound. Over the preceding few decades to the present there has been a considerable refinement of the theoretical and empirical aspects of the psychoacoustics of spatial sound. However we are still in the situation where there is no agreement on the finer details of what is perceptible, measurable or relevant. A consequence has been a lack of a unified approach on how to implement spatial sound beyond stereo, and indeed a lack of agreement on what are desirable characteristics of a spatial reproduction system. This lack of consensus is not confined just to the hardware, but is deeply related to what is the best way of encoding the spatial experience into an inevitably limited information bandwidth.

This problem could be broadly termed spatial coding, with discrete, matrix and kernel solutions being proposed. The discrete and matrix approaches both use speaker feed signals in the transmission medium, with desired sound locations between the speakers being reproduced with a lessened spatial precision or “stereoism” (literally, “solidity”). Kernel methods are more sophisticated, encoding an infinite number of source directions into a given number of channels, but abandoning the concept of a discrete “point source” being reproduced at the limited number of source locations corresponding to speaker locations. Kernel methods do not specify speaker locations implicitly, leaving that choice to the listener who must use the appropriate decoding for his/her speaker configuration.

Quadraphonics was a discrete and/or matrix solution, but there was no real agreement on what was intended to be achieved or what theoretical basis it had beyond “double stereo”. Furthermore, its integration into broadcasting was found not to be straightforward. As a consequence, it failed. Ambisonics is an alternative solution from the same era that offers a very viable compromise using kernel coding, but missed the opportunity to be market tested.

The argument over desirable characteristics has also carried over into the areas of microphones and loudspeakers. In some ways one can consider this a related debate to that which often occurs in the art of stereo recording. Is the intention to record an acoustic event with great precision, or to generate a perhaps even more pleasant spread of sonic images with not much relation to reality? Should one use highly directional loudspeakers in the aid of better imaging, or use less directional radiators that (in stereo) use room reflections to create a more natural listening experience? These issues are far from solved although it appears that in the cinema there is a greater consensus, because the listening environment and coding methods are more highly standardised.

The question of what is really practical or appropriate has not been settled either, although some will say that the buying public knows best. Most homes cannot accommodate sixteen speaker sound systems, nor is it acceptable yet to hand out three dimensional virtual reality headphones to rock concert patrons. Different technologies evolve to suit different contexts.

In the last decade of the twentieth century there has been a growing interest in spatial sound arising from the development of new communications and media technologies. Virtual Reality and High Definition Television (HDTV) both require spatial sound reproduction in excess of what ordinary stereo can offer. Many rental videotapes and television shows are now Dolby encoded for cinema style surround sound. New equipment and software is beginning to proliferate, claiming to deliver spatial sound.

Modern Approaches To Simulating Spatial Sound

There is no commercially available system that successfully conveys the natural spatial hearing experience. Apart from Ambisonics, a close approach is made by binaural stereo and transaural stereo methods, both capable of delivering a quite natural sounding three dimensional effect when used with well recorded source material. However, the limitation is that one must wear headphones with binaural stereo , or in the case of transaural stereo, there is only one good listening position for hearing the full spatial effect through the loudspeakers.

In the laboratory much more is possible, at a much greater cost. If digital audio technology continues to become more affordable then some of these systems will become commercially feasible, but that is no guarantee of their universality or intrinsic merits. Indeed, the rise and fall of quadraphonics could easily be emulated in the next decade by some new candidate. As before, the two key concerns will probably be compatibility with existing stereo and standardisation of software format, including perceptual coding to reduce the digital data rate. Multispeaker stereo, using a small number of frontal speakers is proposed as a worthwhile improvement over stereo, while retaining backwards compatibility.

It remains to be seen whether the recording industry is willing to set aside the stereo paradigm and update all the equipment to a new format, when most consumers would still be using stereo (and even mono) for many more years. Once HDTV with multichannel sound becomes commonplace, there may be an irresistible pressure for the audio-only industry to settle on the same or an even better surround format. In the next few years, these transmission and distribution decisions must also be made for digital audio broadcasting (DAB). The use of simple matrixing and speaker-feed signals seems particularly short-sighted to this author, yet that is exactly what is being proposed for HDTV by some European and Japanese researchers.

Apart from what occurs in the mass marketplace, there will always be distinct applications for other multichannel systems intended for psychoacoustic and localisation research, for auralization (used to simulate building acoustics etc) and even for contemporary music concerts. Current systems are all very specific to their context with not many common features, apart from the use of many amplifiers and loudspeakers. Likewise there appears not to be any accepted spatial coding standard, apart from ad hoc discrete methods. Often the spatial effect is achieved by a “brute force” approach at high expense. However, these multichannel systems can achieve striking effects when combined with the appropriate spatial software or spatial processors.

Equipment based on digital signal processing (DSP) has become commonplace in both the domestic and professional arenas. Processors for recording studios or on-stage applications employ complex but easily useable algorithms, creating a variety of effects with many consequences in stereo space.

Much effort has gone into the digital synthesis of reverberation. Nowadays it is possible to buy for a very reasonable price a device that produces stereo reverberation indistinguishable from a stereo recording of the real event. This technology is commonplace in recording and production studios. Lately a variant has been seen in the domestic sphere in the form of ambience simulators, often requiring the addition of an extra pair of loudspeakers. The devices enable one to play recorded music via a choice of synthesised acoustics, for instance a jazz club or a concert hall. This technology cannot fool the experienced listener, as individual instruments cannot be separated from the stereo mix and given individual spatial characteristics, as would occur in reality. It is not often recognised that reverberation is just one aspect of a perceived depth/distance effect, an area in need of more psychoacoustic research.

Head-Related Transfer Functions

The biggest current research effort in spatial sound is being directed toward head related functions, based on the shadowing effects of the head and on pinna cues. Using these functions it is now possible to generate binaural signals that convey three dimensional sound over stereo headphones, as a synthetic parallel to conventional binaural recordings. The main problem is that to achieve acceptable accuracy, the equipment must be calibrated to the individual’s spatial location versus spectral response, caused by the pinna. If a generic head related transfer function could be discovered that suited all individual variations in ear shape and size, it could be the equivalent of the Rosetta Stone for virtual binaural audio.

These techniques are being proposed for applications where a large amount of aural information must be quickly processed, for example in an aircraft cockpit where the pilot is making an approach to a busy airport. At the moment the head related techniques are far from reliable and cause many “front/back confusions” at the best of times. In spite of this, an immediately practical application may be in teleconferencing, where it is difficult to resolve the voices of several simultaneous participants by conventional means.

The application of this constellation of technological approaches to music composition and production, as opposed to reproduction, is quite varied. In many respects the popular music industry leads the way in terms of using the latest processing technology, albeit only in the realm of stereo. Equipment like Roland Sound Space (RSS) using a hybrid of methods has achieved a limited acceptance, commensurate with its limitations in terms of listening positions.

For computer and contemporary music no one spatial approach has dominated over stereo, with the possible (and lingering) exception of quadraphonics. Ambisonics is used by some and offers considerable advantages when a true three dimensional effect is required, combined with computational elegance. Others have built unique multichannel systems specific to a given venue. In any case, most people accept the need to use loudspeakers for delivering the music to a live audience, ruling out binaural or head related methods.

In computer and contemporary music composition the use of space is very much an individual matter. To a large degree it depends on the technological and software resources available if one is working in a format beyond stereo. Among others, individuals like Chowning, Stockhausen and Wishart have been influential, providing a glimpse of what is possible. The greatest consensus is found in the world of cinema, where the spatial possibilities are limited by the coding standard and informal conventions delineate what is acceptable.

Conclusion

My personal conclusion is that spatial sound is at the point now of a having sufficient technological tools to solve most of the problems, but lacking a consensus on how to employ these tools for optimum results. This has a resulted in a highly fragmented field, not aided at all by a general ignorance about spatial psychoacoustics and the competing marketing departments of key corporate players. What is required is the cultivation of an informed and general outlook on spatial sound, combined with an appreciation of past mistakes and achievements.

c. 1996, Kimmo Vennonen. (Republished with permission.)

 

Binaural In-Depth.

by John Sunier

SO WHAT IS BINAURAL?

The binaural experience places the listener sonically where the sounds on the recording or broadcast originated, and requires no special equipment of any sort other than the binaural source and a pair of stereo headphones. The listener experiences sounds quite accurately localized in a complete 360-degree sphere- a true virtual audio environment. It does this via two tiny omnidirectional mikes placed at the entrance of the ear canals on a replica of a human head (“dummy head”). The two signals are kept entirely separate all the way from this artificial head mike system to the corresponding left and right drivers of the headphones worn by listeners.Though all modern binaural recordings are perfectly compatible for loudspeaker playback, in a normal stereo speaker setup you will lose the “you are there” binaural effect due to leakage of the sound cues intended for one ear into the other ear and vice versa.

Even sophisticated audiophiles are often confused about binaural due to the wrongful use of the term back in the l950’s by many who used Binaural and Stereo as synonyms for one another. Recording pioneer Emory Cook (if you were around then you’ll remember his twin-tracked early stereo LPs) was one of these. Yet in the notes provided with all RCA Victor two-track stereo open-reel tapes starting around 1956 was the following:

Stereophonic recording differs from Binaural (a term sometimes incorrectly applied to stereophonic records) in that the microphone placements are selected for loudspeaker reproduction. Binaural properly applies to a two-channel system designed for headphone reproduction. It thus requires the use of two channels fed by microphones spaced about seven inches apart (normal ear separation).

That definition just about tells the tale. All of us have noticed the tremendous difference between hearing a stereo recording on speakers and hearing it on headphones. Headphones seem to put a giant sonic magnifying glass on all aspects of the recording, including stereo separation. Many recordings sound like half the band or orchestra is in one studio with its signal feeding your left ear, and the other half in another studio with its signal feeding your right ear. The sounds seems to be localized at your two ears and totally inside your skull rather than happening outside your head. Some persons also image a central area of sounds in their skull, so that it feels like three little separated groups of musicians inside your head. The HeadRoom circuit was developed to minimize this effect when listening to standard stereo recordings.

The truth is that over 200 million stereo headphones having been sold in the past decade (way over 600 million if you include all the throw-away headphones bought by those airlines no longer giving passengers primitive plastic tubing). But the source material that nearly everyone is listening to on their headphones was never designed for listening on headphones, but for playing via loudspeakers! With speaker playback, the left channel sounds are meant to reach the right ear and visa versa. Producers of commercial recordings almost always monitor with speakers rather than headphones. Binaural keeps the left and right channels absolutely separated from the original dummy head (or your actual head) all the way to the listener’s headphones without mixing. This applies whether the medium is a recording, live, or a radio broadcast.

PROFESSIONAL MIKE SYSTEMS FOR BINAURAL

Commercial binaural recordings generally use one of two different expensive professional “dummy heads” (“Kunstkopf” in German). In fact, both come from Germany. The Neumann KU-81 or KU-100 head was probably used — often in conjunction with other mikes — on a CD or two in your collection. (Cost: about $6500.) The Aachen Head Acoustics system is more complex, with special equalization to achieve the most natural reproduction on both speakers and headphones. (Their current model is also used for precise acoustic measurement and runs about $29,000.) Some recording engineers feel either of these mikes is capable of making more natural and well-balanced ordinary stereo recordings for speaker playback than the best purist mike techniques. Of course, the full binaural effect is not present in speaker playback except with expensive specialized cross-cancellation electronics; which also force you to sit in a narrow “sweet spot” without the freedom of movement that headphones allow. However, any matrix surround processor using “ambience recovery” rather than “ambience synthesis” will give a better surround sound effect with binaural recordings than with most specially-encoded Dolby Surround CDs. Most Dolby Pro Logic decoders will suffice, though processes such as Circle Surround, Six Axes and EARS are even better. Just stay away from what colleague Dan Kumin calls “boingerizers” – those Hall/Stadium/Jazz Club processors that artificially generate reverberation (echo) to add to the original ambient signal on the recording.

A visible dropping of the jaw is the most frequent indication that someone who has put on headphones is hearing effective binaural for the very first time. Followed by exclamations of surprise, wonder and unbelievability. Binaural, rather than trying to bring the sounds into your listening room, takes you where the sounds originally occurred. You are aware of sounds 360 degrees around you ­ not just right & left but forward & back and up & down! Someone whispering in one ear can make you jump, and a good rainstorm in binaural will have you opening your eyes (if they’re shut – which helps the impression) to make certain you’re not actually getting soaked!

In Binaural, the pinna or outer ears of the dummy head or head of the original recordist set up subtle interference patterns that locate the sounds around the head quite specifically in space. These are known technically as HRTFs – Head Related Transfer Functions – and have become central to current audio research directed toward achieving virtual audio effects with two or more loudspeakers that approach the realism of binaural with headphones. Computer gaming and virtual reality software are fertile fields for this sort of enveloping sound. Sounds coming from directly in front of us bounce off the rear part of the outer ear; sounds from below bounce off the top part of the ear. When a sound is directly in line with the left or right ear there is a straight shot into the ear canal, and this provides different directional information from the other approaches. The ear/brain combination works together closely in binaural hearing. Take for example “the cocktail party effect” – in which we “steer” our binaural hearing around a noisy room and focus it on the one person we want to hear, while minimizing the distraction of other voices.

EARLY BINAURAL

The first experiment with binaural, way back in 1881, compared the effect to the popular stereoscopic views of the period. The inventor said of his binaural patent, “This double listening to sound produces the same effects on the ear that the stereoscope produces on the eye.” He set up a series of carbon telephone mikes in pairs (about 7 inches apart) along the edge of the stage of the Paris Opera. As the singers performed on stage, their voices were carried on twin pairs of telephone lines to a few subscribers homes who had two lines installed. They put the earpiece from one line to their left ear and the earpiece from the other to their right ear. Fortunately, a wide frequency response is not a requirement to convey the binaural effect, because the phone system of the time was surely quite primitive.

MORE RECENT BINAURAL ACTIVITY

There has been sporadic interest and activity in binaural since those early days late in the 19th century. In the middle 1920’s some radio stations in Connecticut and elsewhere broadcast experimentally on two different frequencies — feeding each transmitter separately from a left-ear and right-ear mike in a dummy head in the studio. Listeners were already listening on headsets for the most part, since primitive speakers were just coming into fashion. So this worked out well — they merely put one mono headset, tuned to the left-ear station, to one ear and put the other mono headset tuned to the second station, to their right ear. Some of the West German radio stations have devoted time to special binaural transmissions — often of radio dramas which they call “horspiel.” There has also been interest in Japan. “The Cabinet of Dr. Fritz” series of binaural radio dramas from ZBS Productions was carried for some years on public radio stations here in the U.S. Many of those same stations also carried my own weekly program, AUDIOPHILE AUDITION, on which I presented All Binaural Special broadcasts once per quarter for over 13 years.

In 1970 Stereo Review offered a binaural demonstration LP of music and sound effects which used a homemade dummy head known as the Blue Max. There have been many binaural recordings available in Germany, mainly of classical material and on LP. The disadvantage of employing either analog LP or cassette for binaural material is the noise problem. The surface noise or hiss that we have become accustomed to when listening via loudspeakers can become intolerable with headphones. The greater clarity via headphones makes extraneous noises in the source stand out and detracts from the total sonic experience of binaural. Add to that a peaky high end in some headphones that further points up surface noise and hiss compared to speaker reproduction.

As a result of this, the compact disc and other digital media such as MiniDisc and DAT have proven the perfect medium for binaural. The excellent signal-to-noise lets the listener concentrate on the sounds and begin to forget that he or she is actually listening to a recording – one just starts to take part in the original music or sound-making!

YOU CAN DO IT YOURSELF

Their introduction to binaural makes a great impact on some listeners. Then when they learn how basically simple the recording process can be they are energised to make their very own binaural recordings. Some years ago consumer-level binaural mike systems were offered by Sennheiser, Sony and JVC, but have been long discontinued. Today several suppliers provide a variety of in-ear mike systems at a $70-$300 price range. They are usually paired with a DAT or MiniDisc portable recorder, though a good quality cassette recorder may also be used. [Editor: See the Commercial Links page for binaural resources.]

For such recording efforts, sounds in motion are especially effective in binaural, as well as sounds that are spatially separated. I have some binaural tapes of a symphony orchestral rehearsal, and for demo purposes, it must be admitted that feeling like you are sitting right on stage with the orchestra during the rehearsal, with music stands clanking, chairs squeaking, the conductor walking around to help some of the players with small problems, can sometimes be more exciting than hearing the final performance of the music. Sound effects such as a motorcycle or train passing by, take on a quantum step in “you are there” realism with binaural vs. the old-fashioned stereo demos of trains passing between your loudspeakers. Keep some of these tricks in mind when doing your own recording with binaural mike systems. For example, if you have a quartet of instruments or singers, have them perform in a circle around you instead of in a line in front of you! (I’m a nut on sax quartets and do they ever sound great recorded in this way!) Instead of sitting out in the front row of the audience to tape an early music ensemble, one recordist set up his dummy head with mics in a chair right in the middle of the group onstage – creating an effect as though the listener is one of the musicians performing! – most exciting early music recording I’ve every heard. The surrounding spatiality adds great interest to the music. Another recordist taped his taking an elevator, walking into the concert hall and settling in his seat at the beginning of a concert and then the reverse at the end to make it a more complete binaural experience for listeners. (Unfortunately, the elevator was totally silent, so he edited out that part.)

HEADPHONES FOR BINAURAL

While binaural can be heard with any stereo headphones down to the simplest $5 “ear-buds,” the better the phones, the more amazing the experience. I have found some of the Sony phones around the $100 price point to be good. (The Grado SR-80 at the same price is excellent.) I can’t vouch for current Sony models, but do stay away from the MDR-V6 (once recommended by Consumer Reports) because it destroys much of the binaural effect. Among the best under-$600 phones I have heard for binaural are the Sennheiser HD 600, SONY MDR-CD3000, AKG K-501, Beyer 990 Pro, Etymotic ER-4S, and Grado RS-1. (No special order intended in that list.) The K-500 has many of the qualities of AKG’s flagship K-1000 ($895) which I find the best all-around binaural phone due especially to its ability to help image the sounds outside one’s head. The Jecklin and Ergo headphones from Switzerland, at about the same price point, also offer this advantage. The Etymotic are basically test probes inserted deeply into the ear canals – just the opposite of the off-ear-driver phones. However, their fans rave about them for binaural, and with the tight seal to the eardrum bass reproduction equals the most monster subwoofer you could fit in a room! Extra-cost custom ear molds make the Etymotic more comfortable for extended wear.

The Grado RS-1 Reference phones and the Sennheiser HD 600 are also excellent and of interest to those who find the AKGs too bizarre with their little earspeakers suspended on either side of your head. Both the Grado and Sennheiser provide more deep bass than any other on or off -ear headphones I have heard. The Stax electrostatic earspeakers have been the standard for binaural for years. Their top-of-line Omega has a dedicated tubed amp and goes for over $4000 but is probably the best-sounding headphone ever. Don’t worry about the suitability to binaural of feature differences such as circumaural vs. on-ear, free field vs. diffuse field or electrostatic vs. dynamic. Even extended frequency response is not a prerequisite for successfully transmitting the full binaural effect. Phase accuracy and flat response within the frequency spectrum are the most important parameters. A trend showing the increased interest in headphones and binaural is dedicated high end headphone amps — HeadRoom, Melos, Grado, Music Hall, Musical Fidelity and others have them. AKG will introduce a new model soon. Some of the high end phones practically demand a good dedicated amp, and even a modest amp can upgrade the sonics of a more modest headphone.

c. 1999, John Sunier.
From The Binaural Source. (Republished with permission.)

Depth Perception in Headphones.

(The value of headphones in relation to loudspeakers)

by Ron Soh

head

In a Stax Omega 1 versus Stax Omega 2 headphone discussion that I was involved in several weeks ago, responses from a number of headphone hobbyists revolved around the issue of the value of expensive high-end headphones. I made an appeal for the value of headphones to be judged not just against other headphones, but also against speakers that cost far more. In this essay, I want to share with you what I mean by headphones having a better value than speakers, and also to delve into the subject of how headphones, like loudspeakers, portray soundstage when playing conventional two-channel recordings.

The psychoacoustics of sound localisation need not be brought into this discussion. This essay is NOT about a magic trick of shifting the soundstage from inside the head to a plane between the speakers! Instead, it outlines a simple experiment to illustrate these main two points: (1) headphones sound better than speakers costing more, and (2) headphones do portray a soundstage. If depth clues are portrayed in speakers, then why not in headphones? After all, it is the same signal we are feeding to both of them. In the last section is a tutorial for training one’s ears to identify depth cues in headphones. The tutorial lists specific recordings and passages which have captured these cues clearly and are good training examples.

EXPERIMENT: play some music on your speakers, and make sure you sit (or stand) at the ‘sweet spot’. The ‘sweet spot’ is the position where you are equidistant from the left and right speaker, and not too far and not too near the speakers. Make sure that you have switched off any ‘loudness’ buttons and set all bass/treble control knobs to neutral (if your amplifier has these knobs). Listen to the music via the speakers for a few minutes. Then listen to the same piece of music via your headphones, but sit (or stand) at the same ‘sweet spot’, facing the speakers. Of course, turn off the speakers. Make sure you position yourself at the ‘sweet spot’, face and look at the speakers. Listen to your headphone, and be surprised.

(This experiment assumes that your speakers do not cost more than five times your headphone, as a guideline. For instance, don’t compare a $100 headphone with $2000 speakers! Also this experiment assumes that you are not using cheap $15 headphones. And finally, don’t expect the headstage of your headphone to suddenly shift towards the speakers just because you are looking at the speakers.)

The differences you will notice can be quite entertaining/ educational. Generally, what you will find is that:

  1. the headphone sounds clearer, and it is easier to distinguish between various instruments, as compared to the speaker.
  2. the loudspeaker will likely have a ‘veil’ covering the sound of voices/instruments, and this ‘veil’ is located somewhere around the upper bass/ lower midrange region. This upper bass / lower midrange ‘veil’ is typical of loudspeaker ‘box colorations’, which is the effect of resonances of the speaker cabinet. Your headphone is not perfect either, but it is more likely that your headphone has less ‘box colorations’ than your speakers.
  3. the purpose of facing the speakers while you listen to the headphone is to give you visual clues while you listen to the headphones, so that you can appreciate that headphones DO convey ‘depth clues’. (I will delve into this intricate matter in detail later.)

The purpose of the little experiment above is to demonstrate two key points, which are:

  1. Headphones can be better transducers than speakers
  2. Of course a headphone conveys depth clues

Headphones Can Be Better Transducers Than Speakers

Speakers face more difficulties in painting a sonic picture, because speakers need to move a lot more air compared to headphones. When a speaker has to move more air, its cone (or dome or diaphragm or whatever) has to move back and forth through greater distances, and these greater driver excursions create peculiar problems such as non-linear excursions, cone break-ups, ringing (which is the problem caused when the cone moves forward and then instead of moving back immediately its momentum carries it forward a little bit more), and other problems I might know only if I were a speaker designer.

A headphone has a far easier life. Most headphones do not have woofers, midranges and tweeters — they usually full-range transducers. Therefore a headphone needs no electronic crossover circuits to split up the frequency spectrum into low-frequency, mid-frequency and high-frequency signals that will be subsequently fed to woofers, midranges and tweeters. Crossover circuits present a longer signal path that tend to degrade signal quality. Also, sometimes the crossover is not handled properly and you have problems at the crossover frequency region where the two drivers try to overlap but not successfully.

A headphone also does not have big cabinets that tend to resonate. A speaker, in having to move more air, has to generate a lot of pistonic movement, and that results in huge backlash forces being transferred to the cabinet. A headphone does not need to generate huge pistonic movements, so less backlash energy is transferred to its chasis.

A headphone does not have to contend with room reflections. Of course, headphones have a cavity environment to deal with (a cavity environment is the space enclosed between the headset and your ears). In fact, most of the time, a headphone’s frequency response is not just due to the frequency response of its cone/diaphragm, but also due to this cavity environment. Headphone makers know how to ‘tune’ this cavity envoronment so as to compensate and counter-compensate for the frequency (im)balances of the cone/diaphragm. This cavity environment is far easier to predict, compared to the room environment where a pair of loudspeakers are found. Different rooms create different reflection characteristics, not to mention problems such as standing waves, and cause unpredictable colorations to the sound of speakers.

A headphone’s diaphragm is smaller and far lighter than a speaker’s. This single lone factor gives headphones a better start towards the goal of superior accuracy in the translation of electrical impulses to mechanical movement. Due to the lower inertia, a headphone’s diaphragm starts and stops more quickly than a speaker’s drivers can—therefore a well designed headphone can exhibit more transient attack speed.

A Headphone Can Convey Depth Clues

I hope that little experiment demonstrated for you that headphones give spatial clues, the same way loudspeakers do. In switching to and from your headphone and your speakers, you should be able to hear these depth clues. (If you cannot hear these depth clues, read on – especially the section and tutorial on how to perceive depth clues, then re-conduct the experiment.)

It is such a common misconception that headphones do not have a soundstage. Just because you wear the soundstage on your head does not mean that your headphone has no soundstage. To appreciate the differences between a headphone’s headstage and speakers’ soundstage, we first have to establish how speakers construct their soundstages.

When you position yourself in the ‘sweet spot’ in front of a pair of loudspeakers, a triangle is formed between you and the two speakers. The two speakers form a ‘picture plane’, which is the vertical plane that contains both speakers. This ‘picture plane’ faces you front-on, and depending on whether the speaker’s sonic character is forward or laid-back, images are formed in front of, or within, or behind this ‘picture plane’. Depending on the type of recording, some of the images appear to be positioned further behind this picture plane than other images, and this creates a sense of layering or depth of space. This combination of lateral (left-right) spread and front-to-back depth create what we call a 3-dimensional ‘soundstage’.

People say that although headphones portray lateral left-right spread, headphones do not have a soundstage because headphones do not portray depth — that missing third dimension. Which is the point you can disprove for yourself by conducting that little experiment. Listen to your speakers and notice which images appear to be positioned further back than others. Then listen to your headphones (and while still looking at your speakers). Do you hear the depth clues?

You may hear four ‘layers’ of depth:

  • 1st layer: very near (apparently only inches from the recording microphone)
  • 2nd layer: near (apparently 1 or 2 meters away from the recording microphone)
  • 3rd layer: not near, not far (apparently 5 to 10 meters away from the mike)
  • 4th layer: far (apparently 30 meters or more away from the mike).

Do not be too fixated on the actual numerical value of these distances – do not focus on an image and rack your brains out trying to figure out whether it is 2 meters or 5 meters from you. You are enjoying music, not taking a stressful high-school examination. Moreover, you are not a bat. It is difficult to actually assign a numerical value to the distance of an instrument from the microphone just by hearing it. The numerical figures I mention above are simply to help you picture what I am trying to say—don’t take the numerical digits too seriously.

Close-miked, heavily-mixed recordings tend to have almost all their images in the 1st layer, with the odd image sometimes suddenly appearing in the 4th layer — for example, the sound of a synthesizer that has been given an excessive reverberation treatment. Classical symphonic recordings portray images mainly in the 2nd, 3rd and 4th layers (the occasional solo instrument in the 2nd layer, massed strings in the 3rd, the occasional timpani/cymbals in the 4th, for example). However, please note that even if all the images appear to be in the 3rd layer only, that‘s depth perception already. Most recordings with a lot of depth clues contain images that reside mainly within a single layer, with occasional images making their guest-star appearances in a different layer.

(The reason why I don’t listen to pop CDs exclusively is because most pop recordings contain images that are exclusively positioned in the 1st layer. After listening to one pop CD I like to change to a different recording type which portray images in the 2nd or 3rd layer. It gets rather tiring to keep listening to CD after CD of exclusively 1st layer images.)

Now we come to the most important point I am making in this essay. How does a headphone give you depth clues? Imagine that a school band is performing a musical number and marching along a road steadily AWAY from you. If you were to close your eyes you could hear them receding slowly away from you. How is that so? When playing conventional stereo recordings, you perceive depth clues in three ways: (1) loudness, (2) texture clarity and (3) reverberation. Take these 3 clues one by one:

  1. LOUDNESS: When an instrument is near to you it tends to sound louder. Conversely, the softer an instrument sounds, the further away you infer it to be.
  2. TEXTURE CLARITY: But what happens when an instrument is very near to you, but is played softly? Would you perceive it as being very far away? No, you would not, because the second way you perceive distance is through texture. When your ears hear that the texture of an instrument is very well defined, you infer that it is near to you. The further an instrument is from you, the less specific its texture appears to be. When a guiter string is plucked near you, you can hear its steely nature, its lower and upper harmonics, even though the guitar is plucked softly. But when the guitar string is plucked far from you, you may no longer appreciate its steely nature nor its lower and upper harmonics—you may only hear the principal harmonic. When the texture of an instrument sounds less rich you infer it to be farther away from you. When a drum-sound image has a specific texture of a stretched dry skin being hit, along with a loud sound of a steely rattle, you perceive it to be near; however when its texture is more ‘washed-out’, i.e. less specific, you perceive it to be far away. When a saxophone-sound image has a raspy texture you infer that it is near; when it doesn’t have this strong raspy texture you infer that it is far away.
  3. REVERBERATION: Reverberation is sum total effect of sound reflecting off the wall, floor and ceiling surfaces of the recorded environment. The further an instrument is positioned from the microphone, the more reverberation is captured by the microphone. Consequently, the more an image is surrounded by a reverberative halo, the further away you perceive this image to be. Reverberation causes an image to sound more laid-back, enveloped in a softer, cushier halo. It is always pleasant to listen to recordings with reverberation when listening to headphones, because such images are robbed of any jarring directness, seemingly buffered from you by air cushion. (This is not to say that close-up images are always irritating—not at all. Close-up images in the 1st layer can be very enjoyable via headphones when they have a sense of ‘liquid-ness’ about them. The three states of matter—air, liquid and solid—are very apt metaphors to describe and appreciate the quality of sound.)

The above three ways of perceiving depth clues are the reasons why I say headphones portray soundstages. The reason for me asking you to look at your speakers whilst listening to your headphone is simply to give your some visual references to latch on to while you mentally assign the images to their respective layers (1st, 2nd, 3rd or 4th layer) through the perception of the above three depth clues (loudness, texture clarity and reverberation).

And the reason why I asked you to listen to your speakers FIRST before listening to your headphones is also to convince you that the way a speaker gives depth clues is exactly similar to the way a headphone gives depth clues. By listening to your speakers first you hear the three depth clues (loudness, texture and reverberation), and then when you switch to your headphones next you would be able hear that these very same depth clues are also present via your headphones. Speakers are not televisions, and if it seems that a speaker positions its images in 3-dimensional space it is only because your ears hear these depth clues, not because your eyes are seeing actual objects. If you can hear depth clues via speakers, then why can’t you hear depth clues via headphones? The purpose of looking at your speakers while listening to your headphones is to ‘compare apples to apples’, i.e., to create a level playing field, where the visual asistance normally given by speakers in image positioning is also extended to your headphones.

Having said that headphones have soundstages, it is quite appropriate for me to qualify here that the soundstage thrown by speakers is ‘easier to visualise’ than that portrayed by headphones. When listening to speakers there is something quite literal about the way an image that is perceived BY THE EARS to have more depth actually seems TO THE EYE to be positioned further behind the ‘picture plane’. This visual assistance in image positioning is why people say speakers create a soundstage whilst headphones don’t. But the truth is headphones do give ample depth clues, if not more so. (Note: listening to speakers with the lights off and in a completely dark room still lends this visual assistance to image positioning, because you have a visual memory of where the speakers are placed.)

I hope that if you initially did not perceive your headphone’s ‘depth clues’ when you first conducted the experiment, you will now re-conduct the experiment. You may need to try it out over a few CDs, before your ability to discern these ‘depth clues’ catches on 1.

The psychoacoustics of sound localisation are EXTRINSIC factors that are not the focus of my essay. These extrinsic factors of sound localisation are caused by the position of the transducers (be it speaker or headphone) in relation to our ears. If the transducers are placed in front of us, we perceive the images to be located in front of us. If the transducers are placed directly on our ears, we perceive the images to be located inside or around our heads.

The focus of my essay is the perception of depth clues that are already INTRINSICALLY present in the recordings that we play. These 3 depth clues (comparative loudness, comparative textural specificity, and comparative reverberation) are already part of the signal that we feed to our speakers and headphone. If these depth clues are portrayed by one transducer, then why not the other? After all, it is the same signal we are feeding to both of them.

If you have one of those audiophile test CDs you can demonstrate for yourself the truth of what I say. Listen to the track where the demonstrater hits a percussive instrument, while he slowly walks further and further from the pick-up microphone. The image that you hear over your headphone will CONSTANTLY RESIDE INSIDE YOUR HEAD, but you can tell that the demonstrator is walking progressively away from the microphone. How so? Via the perception of the 3 depth clues I outlined, i.e., the percussive instrument progressively gets (i) softer in volume, (ii) less specific in texture, and (iii) more and more diffused by a reverberative halo.

The psychoacoustics of sound localisation need not be mixed-up with the perception of depth clues via headphones. How far or how near you perceive an image to be is related to extrinsic factors of where the transducers are located in relation to your ears. Whether that image is located in front of you (in the case of speakers) or inside your head (in the case of headphones) does not change the historical fact that instrument A was placed 5 meters from the pick-up mike and instrument B was placed 30 meters from the pick-up mike. These ‘historical facts’ are INTRINSIC to the recordings we play, and are perceivable via headphones.

The purpose of asking the reader to look at his speakers while listening to his headphone was to extend a visual assistance in perceiving these 3 depth clues. I am already accustomed to perceiving depth clues present in recordings, and therefore do not need visual assistance in perceiving that certain instruments are placed further from the recording microphone than others. But for a reader who is new to this perception, this visual assistance is a helpful, but temporary, crutch.

Ear-Training For Depth Perception in Headphones

An audiophile test CD can give a simple demonstration of depth perception in headphones. Listen to the track where the demonstrater hits a percussive instrument, while slowly walking further and further from the pick-up microphone. The image that you hear over your headphone will CONSTANTLY RESIDE INSIDE YOUR HEAD, but you can tell that the demonstrator is walking progressively away from the microphone. How so? Via the perception of the 3 depth clues I outlined, i.e., the percussive instrument progressively gets (i) softer in volume, (ii) less specific in texture, and (iii) more and more diffused by a reverberative halo.

Thus, there are three mechanics of perceiving distances of voices/instruments from the pick-up mikes: (i)comparative loudness, (ii)comparative textural specificity, and (iii)comparative reverberation. These three mechanics are perceivable over any CD, and below is just a sampling:

(1) The Three Tenors In Concert (Teldec 4509-96200-2)
Track 5 Granada- Placido Domingo’s voice is Layer 2. He is not a pop singer who needs to stand so close to the mike!!! So it is not a Layer 1 voice. The tambourine is Layer 3. When only a few people clap, it appears that these people are at Layer 4, but the moment all of them start clapping, it appears they are closer to the mike; they appear to be at Layer 3. This must be the comparative loudness mechanism at work: the louder a sound is, the closer it appears to be.

(2) Planet Drum by Mickey Hart (Rykodisc RCD 80206)
All the images in this CD seem to be layer 2 images. The instruments appear all to be close-miked. However, because my headphone has a laid-back presentation style, I suspect this causes the images to become layer 2 images. A more forward-sounding headphone might portray these them as layer 1 images. I do not know; I don’t have a forward-sounding headphone at hand to verify.

(3) The Emissary by Chico Freeman (Clarity Recordings CCD-1015)
Track 2 Mandela- The saxophone is Layer 1 image (even on my laid-back phones), but the drum kit is Layer 2 in the sense that it is definitely a little further away from the mike than the lead saxophone is. The rest of the accompanying instruments like tambourine, electric guitar and background voices are likewise Layer 2. This style of layering is obviously to highlight the lead saxophone, who is Chico Freeman, the rightful star of this CD.

It is also interesting to note that Clarity Recordings employs a minimally-miked approach here, but the musicians, especially the lead sax, are positioned so close to these mikes that the recording seems a little reverberatively dry, at least where minimally-miked recordings go. I would characterise this CD as a forward-sounding minimally-miked recording. I am used to the idea that minimally-miked recordings are not forward-sounding.

(4) Toolbox by Toolbox (Vaccum Tube Logic Of America VTL 008)
This entire jazz CD is unbelievably reverberatively lush. The lead flute is Layer 2, the piano is Layer 3. The drum kit, oh the drum kit, how do I describe this one? The drum kit itself is Layer 3, but the faint echo/reverberation of that drum kit is Layer 4!!! Heavenly! At the end of each cymbal hit or drum hit the hall is suddenly ‘lit up’ for a very brief moment, and the that Layer 4 designation of the drum kit’s echo is also a sonic description of the acoustic within which this recording was made. Recordings by VTL (which employ a complete line-up of Manley equipment) are so incredible for headphone listening because of the way the layering of apparent distances are achieved by means of reverberation.

The other two mechanisms, i.e., comparative loudness and comparative textural specificity, are not so important in VTL recordings. VTL recordings are must-haves for headphone-freakos! Unfortunately, they do not release new recordings anymore. The alternative to hear the effect of reveberation on the perception of distances is to listen to binaural CDs, which also capture a lot of hall reverb, as a secondary by-product of the recording method.

(5) Music For Strings, Percussion & Celesta by Bartok (Decca 430 352-2)
This classical recording definitely employs a lot of accent mikes placed close to the musicians. Most of the images here are Layer 2 images, with that wierd piano-like percussive instrument being placed somewhere between Layer 1 and Layer 2, in the sense that it is more forward than the rest of the orchestra, but not so forward like the way Madonna would like to eat a mike. Strangely, even the timpani is a Layer 2 image. Timpanis are usually placed way way back at the rear of the orchestra, but this particular timpani does not sound that far away. Must be those accent mikes making the timpani sound nearer than it actually is.

(6) Fireworks by Stravinsky (Delos D/CD 3504)
Delos definitely does not use many accent mikes. The sense of layering in Delos CDs is definitely top-notch. The marvellous bloom of the lush violin section is Layer 3. The brass instruments appear closer, at Layer 2. And that gong-like/drum-like sound (cannot think of the name of that instrument) is way, way at the back of the orchestra, a Layer 4 image. I think the impulse reverberation of the gong-like/drum-like sound contributes to ts sense of being a Layer 4 image. There’s a sense of immense majesty when a timpani/gong/drum becomes a Layer 4 image – like the sound of a distant thunder, growling with authority from afar. No Layer 1 images here.

(7) Stereophile Test CD3 (STPH 006-2) Track 10.

CAUTION! THIS RECORDING IS HEAVY-GOING!

Index 1: 2nos Omni-mikes – John Atkinson talks and hits a cowbell (a percussive thing) in a church interior, and walks from far-stage-left towards the mikes placed in the centre and then away from the mikes towards far-stage-right. His movement nearer and further from the mikes are obvious over headphones. Then he stands at the very back of the church, and walks along the centre aisle towards the mike. This last movement pattern (from back to front of church) is really obvious: his voice/cowbell is decreasingly diffused by church reveberation as he walks towards the front of the church where the mikes are. This is a smooth transition from Layer 4, through Layers 3 and 2, then finally Layer 1. There is no better proof than this track that the distance of a voice/instrument from the pick-up mike is perceivable via headphones!

Index 2: 3nos Omni-mikes – same pattern of movements, except with a different microphone array: a center mike was added. The sense of depth or movement to and from the mikes is likewise the same as Index 1, but due to the center mike, images far-left do not seem as far-left and the images far-right do not seem as far-right, compared to Index 1.

Index 3: ORTF cardiod mikes – same pattern of movements, except with a different microphone type. The sense of depth or movement to and from the mikes is likewise the same as Index 1 and 2, but due to the ORTFs picking up less hall reverb, the image of Mr. Atkinson’s voice/cowbell is less diffused by reverberation. Strangely, it is also very easy to tell when he is standing at the back of the church. This is due to (i)his voice being softer in volume, and (ii)the textural specificity of his voice being reduced, i.e., vocal pronounciations of vowels/consonants are less clear, and the cowbell is less sharp in transient attack when he stands at the back of the church. This experiment clearly shows that reverberation is not the sole mechanics of distance-perception.

Index 4: ORTF cardiod mikes with post-processing. Same as Index 3, but with Blumlein processing to add low-frequency bloom. Same observations as Index 3. I really cannot appreciate the so-called increased-LF-bloom. I do not hear it. But the LF bloom is not relevant to the issue at hand, which is distance perception.

Index 5: Schoeps sphere microphone (binaural) – same pattern of movements, but illusion of sound localisation is partially realised, unlike with the other 4 indexes above, due to the usage of a Schoeps microphone. Image size is smaller and more precisely located in relation to the headphone-wearer. The mechanics of perception of distance here is different from the above 4 indexes, because here the psychoacoustics of sound localisation is called into play. However, because my head is different from the plastic head used, the binaural illusion is only partially realised for me. Index 5 is not a good example to demonstrate the 3 mechanisms listed above, because a fourth mechanism, i.e., the mechanism of sound localisation, is involved here. This mechanism of sound localisation is the basis of binaural recordings.

Note: I am aware that recordings, even minimally-miked ones, are usually not just 2-mike affairs. In conjunction with the main microphones, there are accent microphones which pick up the clarity of the instruments’ musical lines, and there are also hall mikes that are placed further from the musicians to pick up hall reverberation. And the gain applied to each of these mikes is different, depending on the recording engineer’s sonic intentions.

But my contention is this: for every microphone array and mixing configuration, there is such a thing as the centre-of-gravity of that array. This centre-of-gravity is the location where our ears appear to be located, when we listen to a recording. This is an unavoidable fact, I guess due to the egocentric nature of perception: we will always perceive the world, the sonic world even, in relation to ourselves. One will always locate oneself as the centre of the perceived world. When one listens to a particular recording with a particular microphone array, there will always be that one spot where one thinks the musicians and the room/hall are located in relation to oneself. That spot is the centre-of-gravity of the microphone array.

Notes: 1: All these notes about depth clues should not mislead anyone into thinking that listening to a headphone is a very demanding effort. It sure is a cerebral effort for me to try to explain the construction of a headphone’s soundstage to you, but it should not be a cerebral affair for you to discern depth clues via headphones. Like I mentioned earlier, this isn’t a high-school examination — it is music you are enjoying. Remember: an appreciation of depth clues is only one-third of the appreciation of a headphone. There are three ways to enjoy your headphone: its sense of air (this is the category where depth clues fall into), its sense of liquid-ness, and its sense of solidity.

c. 2000, Ron Soh.

A Fender-Tone Tube Headphone Amplifier.

by Alex Cavalli

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This project grew from several conversations that I had with John Broskie of the TubeCAD Journal. I was looking for a good headphone amp and John and I discussed some of the advantages and disadvantages of several of his published circuits. I must say that for someone who creates so much good material, he is also very generous with his time. One particular discussion led me to a White cathode follower design that seemed elegantly simple, that could easily drive 300ohm headphones, and might do respectable duty driving 32ohm phones. The original circuit appeared in the April-May 2001 issue of TubeCAD Journal.

The more I looked at the circuit, the more I liked it. Naturally, because it was so simple, I decided to make it more complex. An issue for me at the start of the project was that I didn’t have any test and measurement equipment (except my ears), so I needed to find a design that I was pretty sure would work before I committed to building it. I spent many hours simulating various topologies with OrCAD PSpice using triode models from Norman Koren’s Vacuum Tube Audio Page that I modified for better accuracy. I also created a new 5687 model and added it to the library. The more designs I simulated the more I liked the simple White cathode output stage.

While Chu Moy and I were discussing the design for this article, he asked me how closely related Broskie’s amp was to the Morgan Jones amp featured in the HeadWize projects. Thus began a long conversation between us that resulted in the update to the MJ article with the new designs, the OrCAD PSpice circuit simulations and the tube libraries. For Bruce Bender’s 6N1P OTL amplifier, I suggested new values for some of the amplifier resistors and a higher voltage power supply, which Bruce generously agreed to try and was able to get much better results.

The Circuit

The Broskie Headphone Amplifier

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Figure 1

Figure 1 is Broskie’s original design for 300-ohm headphones. The plate resistor in this circuit is calculated so that the drive signals to the upper and lower tubes are balanced (see The White Cathode Follower for a discussion about optimizing this configuration). Balancing the drive signals is the biggest issue with this kind of push-pull design. Given the component values, the output impedance of this circuit will be about 53 ohms. It can easily push 20mA peak-to-peak into a 300-ohm load with 0.5V input.

The TubeCAD Journal article at the link above contains a description of this circuit. To summarize here, the output is an optimally designed White cathode follower. A White cathode follower is a push-pull output topology where the signal at the plate of the upper follower is fed back into the grid of the lower triode causing it to follow out of phase with the upper triode (hence the push-pull). To ensure that the tubes both see the same amplitude drive signal the plate resistor must be the reciprocal of the triode’s Gm. The feedback lowers the output impedance below that achievable with a simple cathode follower.

The input stage is a grounded cathode with an active load. Its voltage gain is mu/2, which for the 12AU7 is about 8.5. Broskie selected 5687s for the output tubes because, for miniature triodes, they have very high maximum ratings and good linearity. Maximum current is 30mA and maximum plate dissipation is 3.75W per section. The high maximum current allows the tubes to be biased at 20mA in class A mode. In the push-pull circuit, each triode can swing 10mA up or down with low distortion, giving a total current swing of 20mA. With a Zo of about 53 ohms, the output section has an open loop voltage gain of about 0.92. Furthermore, voltage gain and output impedance stay constant with dropping load impedance.

By comparison, a straight cathode follower using a single 5687 with the same plate voltage, same bias voltage, and open loop voltage gain of 0.76, has an output impedance of 94 ohms. With a 32ohm load the voltage gain drops to .2 and output impedance drops to 24 ohms. Even with a pair 5687s in parallel, the gain only increases to 0.32. Clearly the White cathode follower is a superior power buffer. But even so, Zo of 53 ohms is still not low enough for 32-ohm headphones. The total forward open loop voltage gain of the amplifier is about 7.8 (.92 x 8.5). There are other features of this design relating to power supply noise that are described in the TubeCAD article.

The New Design

As I was pondering this design, several things happened more or less at the same time:

  • Although I wanted a respectable tube headphone amp, I also wanted to experiment with some other ideas.
  • I realized that I frequently listened to music with some bass and treble boost. I knew that I would not be happy with a new amp if it didn’t have at least some bass/treble boost.
  • I realized that the output was out of phase with the input (this is not really as big a deal as some think, but there was an opportunity to correct it anyway).
  • I had some extra 5687s, so that if I paralleled output tubes I could lower the impedance by at least half.
  • John Broskie published another article in TubeCAD Journal discussing a variety of possible sonic controls that could be incorporated into a tube amplifier design (The Missing Sonic Controls).

This all led me to augment John’s design by doing the following:

  • Adding and additional set of output tubes.
  • Adding a Fender tone stack.
  • Adding an input stage to align the phase and compensate for the loss incurred by the tone stack.
  • Adding stereo blend and spatial controls that were now possible between the input stages of each channel.

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Figure 2

Figure 2 is the schematic of the final design including the tone stack but leaving out the volume, balance, and sonic controls. The right half of the circuit is John Broskie’s original White cathode amplifier with a pair of 5687s as output tubes. This lowers the output impedance to about 27 ohms (gain remains the same) and allows me to set the quiescent current at 17mA per section to preserve tube life while still achieving high current swings with lower distortion. I’ve increased the size of the output capacitor to get a better lower frequency response at lower load impedances and added good quality audio caps in parallel with the electrolytics. I also added a fuse after the output capacitors to protect the headphones just in case the electrolytic fails someday.

The 10M resistors (R5 and R13) on the grids of the 12AU7s are not strictly necessary. I included them, however, because I was going to build the amp in stages. I knew that at some point I would want to power it up to measure bias voltages before the volume and tone controls were wired. I needed these resistors to ground the grids and set the proper bias points. I could have just as easily used temporary clip leads to ground the grids when measuring voltages, but adding resistors was not that much extra trouble.

The Fender tone stack is a pure boost tone stack. Unlike the equally well-known Baxandall tone stack, the Fender stack cannot provide bass or treble cut. But, since I never listen with bass or treble cut, the Fender stack offered fewer components and complete capacitor coupling thereby avoiding the use of an additional coupling capacitor from the plate of V1. Like all tone stacks, the Fender tone stack has an insertion loss, in this case approximately 18dB. The “boost” actually comes relative to this loss. In the Fender stack, the mid control is only really active if there is bass and/or treble boost. When the bass/treble controls are off the mid control becomes another volume control.

The parts of the stack form several high-pass filters. The upper part is a high-pass filter through the 250pF capacitor into the treble control whose wiper feeds the next stage. The high-pass bass filter (through the 0.47uF capacitor) sits under the treble control. The high-pass mid filter sits under the bass control. Any signal at the top of the bass or mid controls is fed directly to the treble control’s wiper. If the bass control is all the way on, then the low frequencies are passed directly to the wiper. If the bass control is all the way off (zero resistance), then the low frequencies are shorted through the mid control to ground.

The mid control has a higher pass frequency than the bass control. It bleeds off some of the signal that otherwise would pass through the bass section to ground. Because the turnover point is higher than the bass turnover point, and because, when there is treble boost, high frequencies go through the treble section, the mid control has the effect of creating a mid-range notch that in this design is at about 400Hz-1KHz depending on bass/treble settings.

When bass and treble are off, the output sides of the lower two capacitors and the treble control wiper are shorted together and the response is basically flat. The mid control acts simply as a resistance load which, when set to zero, shorts the entire signal to ground. The 27K resistor prevents V1 from seeing a pure AC short to ground. An extremely useful tool for calculating the characteristics of various tone stacks is the Tone Stack Calculator from Duncan’s Amp Pages. I used this tool when designing this circuit.

Because the Fender stack introduces an 18dB loss, it was necessary to recover some of this loss with the additional input stage. This stage has a voltage gain of about 5.5 (with a bypass capacitor the gain would have been a little over 10). It does add some distortion to the original design (which has very low distortion), but I was willing to accept this to experiment with these additional controls. When bass/treble are off and mid is halfway the total open loop voltage gain is about 7. This is plenty of gain for CD players.

I had to compromise the design here because the spatial control (described below) requires unbypassed cathode resistors. To get enough gain from the first stage I used a fairly high plate resistor. Together these features give the input stage an output impedance of about 8K. The input impedance of the tone stack is about 27K at its worst (everything turned off). A higher ratio of impedances would be better, but I decided not to mess with the design any further than this.

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Figure 3

Figure 3 shows the input section with the balance, volume, and the spatial and blend sonic controls. The balance pot has an “M-N” taper, where at center position, there is zero resistance in each channel The output is shorted for half of the pot rotation and is linear taper for the other half, and each section operating in reverse compared to the other channel. Turning the control to the left attenuates the right channel without affecting the left channel and vice-versa. The blend control performs a standard stereo-mono blend between left and right channels by more or less shorting the plates of V1A and V1B together.

The spatial control is quite interesting. It introduces an in-phase signal from one cathode to the other. When an in-phase signal is applied to the cathode of a grounded cathode stage, this is negative feedback. Here’s an example that helps to explain its operation. In the “soundstage,” a source to the left of center will have a larger presence in the left signal than in the right, but will have a presence in both channels (under normal conditions). Feeding an in-phase left signal into cathode of the right channel will cancel some of source signal that is already in the right channel. And vice-versa. This will tend to make the channels sound more separated or “farther apart” because they no longer contain as many common sounds. [Editor: this type of spatial effect is also called ambience enhancement.] I am able to hear this effect, although it can be very subtle.

Power Supply

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Figure 4

The power supply, Figure 4, is a simple solid-state supply, although it is slightly overbuilt. During simulation I discovered that if the plate voltage for the input stage were drawn from the B+ (high voltage tap) of the output stage the circuit would oscillate, even with standard isolation techniques (R-C filtering). The prototype amp hummed slightly. I put the 5H choke in to track down the hum problem. In the original power supply, I tapped the first stage B+ from the very first filter section. When I installed the choke I had to take all four filter sections from the output of the choke. Both channels have the first two filter stages in common, but different final filter sections.

The heater supply uses a 12V, 5A low-dropout regulator (Linear Technology LT1084-CT-12). One problem with the amplifier design is the range of heater-to-cathode voltages present. If the heater supply were grounded the upper tubes would have heater-to-cathode voltages greater than 125VDC, exceeding 100V specification for the 5687. I solved this problem by borrowing a technique from Bruce Rozenblit (see the OTL design in his book, Audio Reality) where the heater circuit is allowed to DC float, but is AC grounded through a capacitor at the mid-point of V1’s heater. In my case, I attached the capacitor to the negative rail of the heater supply.

There are two power switches; one to turn on the heater supply and the other to turn on the B+ supply. The B+ switch is wired to the heater switch as a fail-safe. Studying the circuit I can’t see any places where adverse voltages would be applied if the B+ came on before the tubes were conducting. But, I turn the heaters on first anyway.

CONSTRUCTION

Component Sources:

Allied Electronics – chassis
Antique Electronics – knobs, audio caps, RCA jacks
Audio Electronic Supply – Noble balance control
Avel-Lindberg – toroidal power transformers
Digikey – wire, regulators
Mouser – resistors, capacitors
Radio Shack – switches, fuses, and assorted parts
TubeBuilder – terminal boards
TubeWorld – matched 12AU7s and 5687s

Stage 1

The front of the amplifier is shown at the beginning of this article. The input and output jacks are on the far left, the power switches on the right. The inputs include right and left RCA jacks and a single stereo mini-jack wired together appropriately. The outputs are both a 1/4″ phone jack and another stereo mini-jack also wired together appropriately. The controls are not labeled yet, but they are from left to right: balance, volume, bass, treble, mid, blend, spatial.

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First, I constructed both power supplies and the Tubebuilder boards (ordered from TubeBuilder.com). Laying out a TubeBuilder terminal board is much like laying out a PC board, except the runs are made with point-to-point wiring and the components are connected directly to the tube sockets or the binding posts. Each board has tube sockets, binding posts, and copper ground plane with standoff mounting spacers underneath. I really like the Tubebuilder terminal boards because they let me do a lot of the wiring outside of the confines of the chassis. It’s much easier to wire the boards first, install them, and complete the power and signal wiring.

Then I drilled, punched, and painted the chassis. Unfortunately, I experimented with the paint on this project. I used appliance-grade black paint whose durability is not what I had hoped for. If I were starting again, I would use standard spray paints and good quality primers that can be found at most hardware stores. Since the chassis is metal, I would bake the paint on carefully. The aluminum chassis and cover plate are made by Hammond. The chassis dimensions are 17″ x 3″ x 10″. Once I painted the chassis black, I decided to paint the screws blue. Since the transformers and caps were blue, it was an easy choice for the screw color.

In the first prototype, there was a small fan on the top of the chassis to provide ventilation. I’ve removed the fan completely because it was too noisy. Now that the regulator is heatsunk to the chassis, the ventilation is not really necessary. Since I had a big hole in the top of the chassis, I made a cover plate with holes in it to let some of the internal heat out anyway. It doesn’t really have much effect, but I had to cover the hole somehow.

The sockets on the Tubebuilder boards are connected to the copper ground plane, which I grounded to the circuit ground. Thus, it is good practice that the tube sockets not touch the chassis to avoid ground currents. Normally the Tubebuilder boards are mounted so far beneath the surface (see below), with only the tubes sticking out, that this is not a problem. But I wanted to be able to see all of the tubes, so I shortened the spacers making it possible for the sockets to electrically contact the chassis. To fix this I drilled an extra large hole for the input tube and cut rectangular openings for the power sections using a saber saw. I filed the hole and cutouts to clean them up. Then I drilled all of the rest of the mounting holes and painted.

The toroidal power transformers were from Avel-Lindberg. (A-L were extremely helpful in taking their time to help me with a very small order of just two transformers.) They are mounted on the top of the chassis, because I like the way they look and because the heater transformer gets very hot. Tube circuits are already hot. No sense subjecting the internal enclosed components to more heat than necessary. Wires for the transformers are fed through rubber grommets.

The heater rectifier and regulator are heat-sunk to the inside of the chassis. Between the two of them they dissipate a lot of power and after a while the entire chassis is pretty warm. It might be possible to use a 3A regulator in place of a 5A regulator, because the heater requirements are 2.7A. However, the “cold heater” current of the tubes may cause the initial surge current to exceed 3A. Current limiting regulators will shutdown and may prevent any heater current from flowing to warm up the tubes so that the current demand can then drop below 3A.

However, in either case, the regulator must be a low-dropout type regulator. Standard regulators must have an input voltage at least 2.5V above the output voltage. But, unless you’ve got a huge 12V transformer, the voltage input to the regulator is likely to drop to or below 14.5V. At this point a standard regulator will stop regulating. On the other hand, a low-dropout regulators need only about 1V difference input to output. In my case, under load, the input to the regulator is about 14.4V, on the edge for a normal regulator, but well within specs for a low-dropout type.

The tone stack capacitors are inserted into the perf board that is suspended in mid air near the controls on the front. The input stage Tubebuilder board is underneath the perf board. The output stage high voltage supply is on the right and the input stage and heater supplies are on the perf board on the left. The non-electrolytic output capacitors are in the center with the fuses.

cavalli7a

An aluminum shield installed between the high voltage supply/transformer and the rest of the circuit reduces radiation problems. After mounting the power supply and Tubebuilder boards to the chassis, I wired up the as much as can be wired without connecting the jacks and controls (this includes wiring the power switches). The power cord ground and the circuit chassis ground are connected to a single chassis ground point.

I tested the 12V supply first without tubes, including testing to make sure that it was floating. I installed all of the tubes and tested the heater supply again and powered up the high voltage and waited for smoke. When none appeared, I started measuring the bias voltages according to figures 2 and 4. In my case, the actual B+ voltages were little higher than designed, but well within tolerance. When these checked out, I pulled the tubes and started Stage 2.

Stage 2

At this point I mounted the jacks and controls, positioning their various connections for ease of wiring. All of the jacks’ grounds are insulated from the chassis using plastic and fiber washers, again to avoid ground loops. The Noble balance pot has a small circuit board that is mounted to its pins. Wiring is then done to the circuit board.

cavalli8a

Good design made the control wiring very simple. Once I got this far, I built the tone control board. This board contains the three tone capacitors and the 27K resistor for both channels. The board is mounted in mid-air above the input stage (or below depending on your orientation). Because it is so light, the board is held in place by the wires connecting it to the rest of the circuit. I used shielded wire for the signal wires to an from the tone stack and from the volume control to the input stage.

The last step was to mount and wire the output electrolytics. To do this, I had first drilled holes in chassis about 1/4″ smaller diameter than the capacitor itself. Then, as part of early construction, I mounted a perf board flush underneath the chassis covering these holes. I used the screws that fastened the perf board to also attach the fuse holders. The caps are snap-mount types with fairly short, stiff leads. I pushed the leads through the perf board from the top and bent them over, which essentially fastened the caps down to the chassis. Then I wired the parallel audio caps and connected these pairs to the output of each channel, through the fuses to the output jacks.

cavalli9a

Anything resembling a wire bundle is held together with plastic cable ties. Once the controls and tone board were wired, I attached the knobs. The knobs are available from Antique Electronics (see below). They are 1″ black anodized aluminum. I also bought the Solen caps and the gold-plated RCA jacks from these folks.

Except for the balance control, the pots are all inexpensive Alpha potentiometers that I bought from Mouser. The dual balance pot is Noble part number 220Y100K(W)X2-9920, purchased from Audio Electronic Supply. ALPS also makes this kind of pot, but I couldn’t find the ALPS pots on the web, so I bought the Noble. If you had to substitute, you could just use an ordinary dual 100K linear pot wired as a balance control. This will cut the signal strength in half immediately at the input, but there is plenty of gain to compensate for it. I just don’t like to do this because gain always adds distortion and noise.

The values for the “mid-point” resistance of the blend and spatial controls, calculated using the formulas in the TubeCAD Journal, are around 10K. After some experimentation I finaly chose a 50K linear pot for the blend control and a 25K linear pot for the spatial control. Both pots have rear-mounted switches so that the controls can be completely removed from the circuit.

cavalli9b

The small capacitors in the amp (figure 2) are metal film, except for C1. C1 is a ceramic capacitor, because I was not able to find a 250pF film capacitor. I have heard the various discussions about capacitors for audio equipment. But, I am not enough of an expert on this to know one way or the other. Plus, I don’t have any equipment and I am not able to try experimenting with various caps. I did later see some 250pF silver mica caps at Antique Electronic Supply and would have used them just to be safe. In truth, however, I don’t know how much difference it would make. The amp sounds OK to me and the highs (where these caps matter) don’t sound harsh or brittle or whatever.

Here are the component layout and wiring diagrams for the TubeBuilder boards:

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PERFORMANCE

As I mentioned above, I don’t have test and measurement equipment so my specs on this circuit are derived from simulations (which are generally better than reality). The performance of the amp, as determined from simulation, is shown in figures 5 through 8.

Note: the gain of the amplifier, described above, is not really that important. After all if the 0.5 volt output from a CD player line-out could drive 32-ohm headphones with enough current, it would be delivering 8mW (pretty loud). What any power amp really does is convert the voltage at the input into current into the load. As everyone knows power amps are just buffers that translate a high-impedance voltage source into a low impedance current source. In figures 5 to 8, therefore, I’ll be looking at current into the load.

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Figure 5

Figure 5 shows the current supplied to a 300ohm resistive load. The input is 0.5V. The bass and treble controls are set at midpoint (in terms of resistance, not rotation). The midrange control is all the way on. The power output into the load (using P = (I^2 * R)/ 2) is about 15mW. For most headphones this should be more than adequate power.

cavalli13a
Figure 6

Figure 6 shows a Fourier analysis of this same trace. I’m using the Fourier analysis to estimate the distortion. For those who don’t know what a Fourier analysis is, a Fourier transform translates a time-varying signal into the frequency domain showing all of the frequency components that comprise the signal with their respective amplitudes. In this case, the input signal is a pure sine wave at 1KHz. If any other frequency components show up in the current at the load, then the amp is adding harmonic distortion (harmonic because the frequencies occur at harmonics of the base signal).

Before reviewing the Fourier analysis, it is important to point out that this is simulation. Real circuits exhibit many characteristics that are not accounted for in some of the models, including the fact that simulated components are perfect unless specifically created to be otherwise. In this case, the resistor and capacitor models are perfect; the distortion is coming primarily from the non-linearities in the tube characteristics. We should use these estimates with caution, although they should give a basic picture of what the amp is doing.

The large peak at 1KHz is, obviously, the primary signal (it goes up off the screen). There is no significant signal at the fourth harmonic or above. The total current flowing at 2KHz and 3KHz (the small peaks) is about 3ua. An estimate of the THD is given by dividing this number by the total current flowing at 1KHz, about 10mA. Thus, 3uA/10mA = 0.0003 = 0.03%. This is a very low distortion figure. The real number will be higher than this. The only way to get this number is to measure it. However, the simulation indicates that the amp should have very good distortion figures. Even if the real distortion is ten times higher, it will be around 0.3%. Still a good number.

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Figure 7

Figure 7 shows the current supplied to a 32-ohm resistive load, 0.2V input at 1KHz. The bass and treble controls are set at midpoint. The midrange control is all the way on. At 22mA into 32 ohms, the amp is producing 8mW. This is still a lot of power for most headphones.

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Figure 8

Figure 8 is the Fourier analysis for this output trace. Adding up second and third harmonics we have about 85ua. Performing the same calculation as before, the THD is approximately 0.38%. The actual distortion may be higher than this. As you can see the amp does better with a 300-ohm load than a 32, but it still performs well at 32 ohms.

At 15mW and 8mW power delivery into the loads of Figures 5 to 8, the amp does not exhibit any clipping behavior. This is because the quiescent current in the output section is about 36mA, making it possible to swing ±32ma in class A operation with minimal distortion and without clipping. Beyond this, the grids in the real circuit will start to be driven positive. The simulation models do not show the effect of this very accurately.

Frequency Response

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Figure 9

Figure 7 shows the amp driving a 32-ohm load at 40mA peak-to-peak. At 20mA peak-to-peak, THD is about 0.15%. The THD in both cases seems fairly constant from 20Hz-20KHz. With the tone controls set at no boost, response is better than 3db flat from 10Hz to 300KHz, shown in Figure 9 (PSpice AC analysis result).

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Figure 10

Figure 10 is the frequency response with bass and treble at full boost and the mid control at half. The volume control for this simulation was set lower to keep figures 9 and 10 near the same scale. The center of the notch is about 400Hz.

RESULTS

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My current headphones are Sony MDR-V600 Studio Headphones (45 ohms) that can be found at most consumer electronics outlets. My music source is a Sony portable CD player line output. There is much to be desired in replacing this combination, but even with these components I can say that the sound from the amplifier is very clean and crisp. It is also very quiet. The tone controls give me enough flexibility to satisfy my listening habits. The stereo blend control works exactly as expected. At first, I couldn’t really hear the effect of the spatial control. But after listening carefully, I can hear the sound stage get wider and narrower as the control is brought through its “mid-point” value. The amount of effect, of course, depends on how the music was recorded to begin with.

The performance numbers from simulation are borne out to the extent that with 45-ohm headphones I can barely crack the volume control to achieve a comfortable listening level, even with the tone stack set flat. With the volume near halfway, the sound level is unbearable for me. This leads me to believe that this amp could adequately drive Grado 32-ohm headphones. I have tested the cheap 32-ohm headphones that come with portable CD players. The amp easily drives these.

If I were to build another amp like this one, I would add a crossfeed section based on the designs described in HeadWize, and I might experiment with some other tone controls and equalizer designs. Actually, I am very happy with the Fender tone stack. I have found a combination of bass/treble boost that I like (as I thought I would) with my Sony headphones: in terms of rotation – Bass 1/2, Treble 3/4, Mid 1/2. This is a very pleasing sound for me and I find myself leaving this combination for almost all recordings. The effect of the spatial control is to separate the soundstage. It is not that substantial. Furthermore, I generally don’t have problems with headphone ambience. I guess I’m not a true headphone connoisseur!

I would probably use the Fender stack again. I would eliminate the ambience control and design a crossfeed filter. I might also remove the regulator on the heaters and just put a giant electrolytic (10,000 – 22,000uF). This would be easier, although it would require a voltage dropping resistor that would still dissipate a lot of power.

The next step for me is to get some better headphones and music source! In fact, if someone wants to contribute an article on building a tube CD player, “I’m all ears!” In the meantime, this project has exceeded all of my expectations. My thanks again to John Broskie for his great work in the TubeCAD Journal and for taking time to give me his insightful comments.

Appendix: Simulating the Amplifier in OrCAD PSpice

Alex Cavalli has provided the project files for simulating this amplifier using OrCAD Lite circuit simulation software. OrCAD Lite is free and the CD can be ordered from Cadence Systems. At the time of this writing, OrCAD Lite 9.2 is the latest version. OrCAD Lite 9.1 can be downloaded from the Cadence website (a very large download at over 20M) and should work as well. There are 4 programs in OrCAD suite: Capture, Capture CIS, PSpice and Layout. The minimum installation to run the amplifier simulations is Capture (the schematic drawing program) and PSpice (the circuit simulation program).

Download Simulation Files for Cavalli Headphone Amplifier

Download OrCAD Triode Simulation Libraries

After downloading cavalli_sim.zip and orcad_triodes.zip, create a project directory and unzip the contents of the mj_sim.zip archive into that directory. Then extract the contents of the orcad_triodes.zip archive into the \OrcadLite\Capture\Library\PSpice directory. The files triode.olb and triode.lib libraries contain simulation models for several popular types of triode vacuum tubes including the ones used in this amplifier. They are based on tube SPICE models found at Norman Koren’s Vacuum Tube Audio Page and Duncan’s Amp Pages. Put the files triode.olb and triode.lib into the \OrcadLite\Capture\Library\PSpice directory. Note: heater connections are not required for any of the triode models.

The two basic types of simulation included are frequency response (AC sweep) and time domain. The time domain analysis shows the shape of the output waveform and can be used to determine the amplifier’s harmonic distortion. They both run from the same schematic, but the input sources are different. For the frequency response simulation, the audio input is a VAC (AC voltage source). The time domain simulation requires a VSIN (sine wave generator) input. Before running a simulation, make sure that the correct AC source is connected to the amp’s input on the schematic.

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The following instructions for using the simulation files are not a complete tutorial for OrCAD. The OrCAD HELP files and online manuals include tutorials for those who want to learn more about OrCAD.

Frequency Response (AC Sweep) Analysis

  1. Run OrCAD Capture and open the project file cavalli.opj.
  2. In the Project Manager window, expand the “PSPICE Resources|Simulation Profiles” folder. Right click on “Schematic1-Response” and select “Make Active.”
  3. In the Project Manager window, expand the “Design Resources|.\cavalli.dsn|SCHEMATIC1” folder and double click on “PAGE1”.
  4. On the schematic, make sure that the input of the amp is connected to the V4 AC voltage source. If it is connected to V3, drag the connection to V4.
  5. To add the triode library to the Capture: click the Place Part toolbar button (orcad1). The Place Part dialog appears. Click the Add Library button. Navigate to the triode.olb file and click Open. Make sure that the analog.olb and source.olb libraries are also listed in the dialog. Click the Cancel button to close the Place Part dialog.
  6. From the menu, select PSpice|Edit Simulation Profile. The Simulation Settings dialog appears. The settings should be as follows:
      Analysis Type: AC Sweep/Noise
      AC Sweep Type: Logarithmic (Decade), Start Freq = 10, End Freq = 300K, Points/Decade = 100
  7. To add the triode library to PSpice: Click the “Libraries” tab. Click the Browse button and navigate to the the triode.lib file. Click the Add To Design button. If the nom.lib file is not already listed in the dialog list, add it now. Then close the Simulation Settings dialog.
  8. To display the input and output frequency responses on a single graph, voltage probes must be placed on the input and output points of the schematic. Click the Voltage/Level Marker (orcad2) on the toolbar and place a marker at the junction of R6 and the grid of U7. Place another marker above RL at the amp’s output.
    orcad4
  9. The tone controls are set full on, so the frequency response is not flat. To get a flat response set R10A to 250K, R10B to 1, R11 to 1, and R12 to 5K. The treble pot has to be represented by two resistors because PSpice doens’t have a native variable resistor model.
  10. To run the frequency response simulation, click the Run PSpice button on the toolbar (orcad3). When the simulation finishes, the PSpice graphing window appears. The input and output curves should be in different colors with a key at the bottom of the graph.
  11. The PSpice simulation has computed the bias voltages and currents in the circuit. To see the bias voltages displayed on the schematic, press the Enable Bias Voltage Display toolbar button (orcad5). To see the bias currents displayed on the schematic, press the Enable Bias Current Display toolbar button (orcad6).

Time Domain (Transient) Analysis

  1. On the Capture schematic, make sure that the input of the amp is connected to the V4 sinewave source (VAMPL=0.25, Freq. = 1K, VOFF = 0). If it is connected to V3, drag the connection to V4.
  2. In the Project Manager window, expand the “PSPICE Resources|Simulation Profiles” folder. Right click on “Schematic1-Transient” and select “Make Active”
  3. From the menu, select PSpice|Edit Simulation Profile. The Simulation Settings dialog appears. The settings should be as follows:
      • Analysis Type: Time Domain(Transient)
      Transient Options: Run to time = 80ms, Start saving data after = 40ms, Max. step size = 0.001ms
  4. To display the input and output waveforms on a single graph, voltage probes must be placed on the input and output points of the schematic. Click the Voltage/Level Marker (orcad2) on the toolbar and place a marker at the junction of R6 and the grid of U7. Place another marker above RL at the amp’s output.
  5. To run the time domain simulation, click the Run PSpice button on the toolbar (orcad3). When the simulation finishes, the PSpice graphing window appears. The input and output curves should be in different colors with a key at the bottom of the graph.
  6. To determine the harmonic distortion at 1KHz (the sine wave frequency), harmonics in the output waveform must be separated out through a Fourier Transform. In the PSpice window, press the FFT toolbar button (orcad7). The PSpice graph changes to show the harmonics for the input and output waveforms. The input and output curves should be in different colors with a key at the bottom of the graph.
  7. The fundamental frequency at 1KHz will have the largest spike. The other harmonics are too small to be seen at the default magnification. In the PSpice window, press the Zoom Area toolbar button (orcad8) and drag a small rectangle in the lower left corner of the FFT graph. The graph now displays a magnified view of the selected area. Continue zooming in until the harmonic spikes at 2KHz, 3KHz, etc. are visible.
  8. Harmonic spikes should exist for the output waveform only. The input is an ideal sine wave generator and has no distortion. To calculate total harmonic distortion, add up the spike values (voltages) at frequencies above 1KHz and divide by the voltage at 1KHz (the fundamental).

Note: simulations only approximate the performance of a circuit. The actual performance may vary considerably from the simulation as determined by a number of factors, including the accuracy of the component models, and layout and construction techniques.

c. 2002 Alex Cavalli.