Understanding Headphone Power Requirements.

By Dennis Bohn, Rane Corporation

Much confusion abounds regarding headphone power requirements. This RaneNote is intended to disperse some of the mist surrounding headphone specifications and hopefully give you a clearer understanding of how much power is really needed for your application.

HEADPHONE SENSITIVITY

Headphone manufacturers specify a sensitivity rating for their products that is very similar to loudspeaker sensitivity ratings. For loudspeakers, the standard is to apply 1 watt and then measure the sound pressure level (SPL) at a distance of 1 meter. For headphones, the standard is to apply 1 milliwatt (1 mW = 1/1000 of a watt) and then measure the sound pressure level at the earpiece (using a dummy head with built-in microphones). Sensitivity is then stated as the number of dB of actual sound level (SPL) produced by the headphones with 1 mW of input; headphone specifications commonly refer to this by the misleading term dB/mW. What they really mean is dB SPL for 1 mW input.

Think about these sensitivity definitions a moment: headphone sensitivity is rated using 1/1000 of a watt; loudspeaker sensitivity is rated using 1 watt. So a quick rule-of-thumb is that you are going to need about 1/1000 as much power to drive your headphones as to drive your loudspeakers since both of their sensitivity ratings are similar (around 90-110 dB-SPL). For example, if your hi-fi amp is rated at 65 watts, then you would need only 65 mW to drive comparable headphones. (Actually you need less than 65 mW since most people don’t listen to their loudspeakers at 1 meter.) And this is exactly what you find in hi-fi receivers. Their headphone jacks typically provide only 10-20 mW of output Power.

Take another moment and think about all those portable tape players. Ever hear one? They sound great, and loud. Why you can even hear the headphones ten feet away as the teenage skateboarder that ran over your foot escapes.

Power output? About 12 mW.

THE LIST

As an aid in finding out how much power is available from the MH 4 Headphone Console, we have compiled a listing of popular headphones. Included is a column giving the maximum SPL obtainable using the MH 4 and any particular headphone. Ultimately, it all gets down to actual SPL. The power rating really doesn’t matter at all. Either it’s loud enough or it isn’t (of course it has to be clean power, not clipped and distorted). The SPL numbers shown are for maximum continuous SPL; for momentary peak SPL add 3 dB.

Note that the maximum achievable SPL varies widely for different models and manufacturers, ranging from a low of 107 dB to a harmful 146 dB! The table also shows there is very little relationship between headphone impedance and sensitivity, and that power output alone means nothing, since in one case 80 mW produces a maximum SPL of 107 dB, yet in another case the same 80 mW yields an SPL of 124 dB!

Sensitivity dB is measured sound pressure level with 1mW of power. The Max Power mW columns are typical continuous average (RMS) power, 20 Hz-20 kHz, with THD less than .4%.

If headphones are not yet owned, or replacements are desired, use this listing as a guide for selecting headphones with sufficient sensitivity for the maximum desired SPL.

Table of Headphone Specifications

Disclaimer: The headphone specifications were supplied to us by the respective manufacturers, subject to change without notice. 

Manufacturer Model Impedance
(Ohms)
Sensitivity
(dB)
Max Power
(mW)
Max SPL
(dB)
AKG K141M 600 98 80 117
K240M, K240DF 600 88 80 107
K270S 75 92 380 118
K301 100 94 285 119
K401, K501 120 94 290 119
Audio-Technica ATH-COM1, COM2, ATH-908 40 90 440 116
ATH-910 40 92 440 118
ATH-P5 40 100 440 126
ATH-M40 60 100 400 126
ATH-D40 66 102 295 127
ATH-M2X, ATH-M3X 45 100 435 126
Beyerdynamic DT150 250 97 175 119
DT211, DT311 40 98 440 124
DT250 80 98 360 123
DT411 250 102 175 124
DT531 250 95 175 116
DT431, DT331 40 86 440 112
DT770PRO, DT990PRO 600 96 80 115
DT801, DT811,DT511 250 94 175 116
DT901, DT911 250 98 175 120
Fostex T-5 44 96 435 122
T-7 70 98 385 124
T-20 50 96 425 122
T-40 50 98 425 124
Hosa HDS-701 40 91 440 117
Koss Headphones A/250, A/200, A/130, TD/80 60 98 320 125
R/200 60 84 400 110
R/100, R/45 60 85 400 111
R/90, HD/2, SB/15 60 100 400 126
R/80, R/35S, R/20, Porta Pro models 60 101 400 127
R/70B, R/55B, SB/50, SB/35 60 101 400 127
R/40 60 90 400 116
R/30S 60 106 400 132
R/10 60 103 400 129
TD/75 60 95 400 121
TD/65 90 101 340 126
TD/61 38 93 440 119
Sennheiser HD433, HD435 32 94 450 121
HD25 70 120 380 146
HD445 52 97 390 123
HD25SP 85 100 350 125
HD265, HD525, HD535, HD545, HD565 150 94 190 117
HD455, HD475 60 94 400 120
HD465 100 94 285 119
HD580, HD600 300 97 80 116
Sony MDR-V100MK2 32 98 450 125
MDR-85 40 102 440 128
MDR-V600, MDR-D77 45 106 435 132
MDR-CD10 32 96 450 123
MDR-CD550, CD750 45 100 435 126
MDR-CD6 45 110 435 136
MDR-CD850, CD950 32 102 450 129
MDR-CD1000, CD3000 32 104 450 131
MDR-D33, MDR-D55, MDR-7504 45 104 435 130
MDR-7506 63 106 400 132
MDR-7502 45 102 435 128
Stanton ST PRO, DJ PRO 1000 32 100 450 127
Telex PH-6 600 105 80 124
Yamaha RH5M 32 98 450 125
RH1 32 90 450 116
RH2 32 95 450 122
RH3 60 95 400 121
RH10M 40 102 440 128
RH40M 32 103 450 130

c. 1983, Rane Corporation

Understanding Headphone Power Requirements PDF version.

c. 1983, Rane Corporation
From Rane Corporation Site. (Republished with permission.)

 

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.