In-Ear Monitoring.

by Garwood Communications
(updated July 1998)



1. General concept
2. How the equipment works
3. Applications
music, on tour and in the studio
broadcast, installations
theatre and special events
4. FAQs (Frequently Asked Questions)
5. Health & Safety
6. Product Range & Accessories
wireless in-ear monitoring
hard-wired systems

1. The General Concept

In-ear monitoring technology made its first appearance in public in the late 1980s. It was originally conceived by a front-of-house engineer, Chrys Lindop, touring with Stevie Wonder at that time. He teamed up with another British engineer, Martin Noar, whose extensive RF expertise resulted in the first Garwood systems. Known as The Radio Station, the units were road-tested by popular performers such as Michael Bolton and The Outfield who used these early VHF devices on shed and arena tours all over the USA.

Garwood was the beneficiary of invaluable real-world user feedback in the development cycle of its products. All the bands who used the prototype systems were unanimous in their enthusiasm for the benefits of in-ear monitoring.

The idea is simplicity itself. Replace the cumbersome and feedback-prone floor monitor and sidefill loudspeakers with a small wireless device, worn by the performer, which would deliver the monitor mix directly to his ears at a volume that he could control himself. The system offers many benefits for the performer as well as the audience;

  • Complete freedom of movement for the artist
  • Control of volume, helping to safeguard hearing and reducing voice fatigue
  • A clear and uncluttered stage, improving audience sightlines
  • The reduction of on-stage volume, which improves front-of-house sound
  • Overall improvement in monitoring sound quality, more precise, more consistent.

From a technician’s point of view, set-up time is vastly reduced. The tiny size of an in-ear monitoring system compared to a loudspeaker monitor system offers dramatic savings in terms of transport and storage costs – and roadies love ‘em!

Garwood’s technology, and extensive experience, has been used to produce a system which not only offers simple setting-up of the equipment, but also minimises the potential for wireless-related problems.

2. How the Equipment works.

A Radio Station is a UHF stereo wireless system, with a 1U rack-mounted transmitter, antenna and a stereo receiver unit worn as a belt-pack. The receiver is designed to be used with Garwood’s Micro Monitors, which are custom-fitted to the performer’s ears. (A range of different earpieces are available – see the Accessories section).

Depending on the model, the stereo transmitter is switchable between a number of operating frequencies in the UHF band. A local monitor jack allows the monitor engineer to listen to the artist’s mix. The receiver beltpack is 9V battery powered, offering up to 6 hours of operation. The operating range of the system is up to 100m/300ft depending on local conditions.

The risk of feedback can be almost completely eliminated by the removal of the on-stage monitor speakers as there is no open speaker to feedback into the microphone. The mix is transmitted in stereo, but some users prefer to use just one earpiece. Sometimes a user would require an additional floor monitor speaker in addition to their IEMs (particularly drummers, who enjoy the physical sensations of low frequency!) It should be realised that, whilst this is fine, the risk of feedback does increase. The system has an on-board variable slope compressor/limiter which prevents sound levels exceeding a pre-set safety limit. This helps protect the wearer against sudden volume surges, whilst allowing natural transients to “breathe”.

An additional feature has been built in so that, should low RF at the receiver cause excessive noise (which may happen at the extreme edge of the range), the receiver audio output would perform a fast fade down, rather than the conventional method of switching off the audio. This prevents any disturbing clicks or pops in the ear-pieces and gives the added security of an immediate and silent shutdown, even in the event of complete transmitter failure.

The Radio Station is ‘seen’ by the console as just another amplifier. It will accept inputs from any console, and connection is made via XLR input connectors. The inputs are electronically balanced as standard, but optional isolating transformers may be easily fitted internally.

RF Issues

RF can present its set of problems; with an increasing number of wireless devices on stages (microphones, instrument transmission systems as well as in-ear monitoring), it is essential to plan in advance.

Two common interference-related problems are multipath reflection and intermodulation (see below). Poor reception can also be caused by signal masking that can sometimes occurs when a performer wears the receiver underneath clothing containing metallic fibres.

Multipath Reflection

When radio systems are used in a stage environment, there are occasionally dropouts around the performance area. In a perfect world, the transmitted signal would radiate from the aerial, across the stage to the receiver aerial. Of course, this does happen but because the antennas used are, on the whole, omnidirectional, the signal will radiate in all directions. At any given frequency, certain materials may absorb the energy whilst others will tend to reflect the signal. This now means that the receiver picks up not only the main signal, but also a multitude of reflected signals. Although radio frequencies travel near the speed of light, at UHF frequencies, the time differences between the direct and reflected signals can give rise to phase differences. If two signals arrive at the receiver 180° out of phase with each other, cancellation will occur, causing the signal to dropout. This is commonly referred to as multipath dropout. Other phase differences may cause reductions in signal strength at the receiver aerial which may cause other symptoms such as erratic increases in noise.


When putting together multi-channel wireless systems, it is very important to consider the effects of interaction between the systems. It may seem logical to assume that, because your four radio mic frequencies are different, they will work together. There is however the phenomenon of intermodulation.

An intermodulation product is basically a tone or frequency generated through the interaction of two other tones. For example, if you were to play a single note, say middle C on the piano, you would only hear middle C. Now play the C# key, and you only hear C#. But, if you were to play C and C# simultaneously, apart from hearing C and C#, you would also hear a third tone which is the intermodulation product. Exactly the same thing happens to RF frequencies and it is these unwanted ‘notes’ or frequencies that can cause receiver problems.

‘Line of sight’ is an important element in RF equipment operation, and refers clearly to signal having an uninterrupted transmission route from transmitter aerial to receiver aerial. Metal structures in the line of sight may cause interference through multipath reflection, so this puts great importance on the precise positioning of transmitters and antennas.

Recent developments in Radio Station technology have simplified channel selection. The new synthesised processor used in the Radio Station IDS and TS models automatically offers a selection of pre-set frequencies, allowing the user to choose:

1. available legal channels between 510-865MHz for the territory it is being used in

2. intermodulation-free frequencies; the pre-programmed frequency sets for each country in the processor are calculated to work together.

The Active Antenna removes many of the problems associated with positioning transmission equipment. By effectively removing the RF from the rack unit processor, many operational benefits follow. A multiplexed output signal connects the rack-mount processor unit to the Active Antenna. Broadcasting range from the Active Antenna can exceed 100 metres to the receiver.

One of the biggest problems with multiple systems occurs when antennas are incorrectly placed too close together causing multipath dropout or intermodulation. For example, on a recent Rod Stewart tour, 14 aerials on stands had to be carefully positioned to avoid the above problems. Due to the inherent losses within cables used to connect the transmitter to the aerial, there is a practical limit as to how long these cables can be. Even large diameter, low loss cables should not be used beyond 25 metres and so there is an obvious restriction as to where aerials can be rigged in relation to the transmitter unit which normally sits in a rack by the monitor position. The new Active Antenna can be sited up to a distance of 300 feet from the transmitter or processor unit without any loss in transmission power! It is also waterproof and conforms to the US Military Specifications MIL-STD-810E.

3. Applications

Since the first days of Radio Station, the majority of Garwood’s customers has been drawn from the ranks of top touring professional performers. From the Grateful Dead to Pink Floyd, Gloria Estefan to Bryan Adams, The Eagles to REM, it is an impressive line up.

The acceptance from the performing community is hardly surprising, since the product was originally designed for use by professional rock musicians. However, different markets have begun to emerge for the product as people embrace the new technology.

1. Semi-professional musicians
Largely as a result of product costs coming down, there is now increasing interest in in-ear monitoring technology from cabaret and small bands. This reflects the growing concern with hearing healthcare, as well as enthusiasm for the benefits of the technique. Music venues are also installing systems for use by touring acts; because the earpieces are custom-made for their owner, they simply plug into the house system when they arrive.

2. Classical Music
Classical and orchestral performers are now discovering the accuracy and precision of in-ear monitoring; it is also a group which places a very high priority on hearing healthcare.

3. Theatre
In many theatre, monitor levels that are too high can really affect the quality of house sound; also theatrical productions are highly likely to have performers moving around – theatre is anticipated to be a major growth area for in-ear monitoring, curbed only by the problem of actors having to wear multiple body packs (e.g. radio mics) about their costume.

4. Broadcast
Applications in this sector vary from live music programming to presenter talkback. Garwood is currently working with leading British broadcasters to develop specific in-ear monitoring products for this sector.

5. Control/cueing at events
With a Radio Station, this application is rather like taking a sledgehammer to crack a nut, but there have been several instances of Garwood devices being used in a comms role – e.g. at memorial celebrations in London, where the firework operations were all timed to music and cued via Radio Station links.

6. Studio monitoring
A development born out of the user-friendliness of custom-made earpieces, many users take them into recording studios and use them in preference to headphones. Audio performance is significantly better than live room playback and cans; in addition, the deep-insertion earpieces greatly reduce spill.

4. FAQs (Frequently Asked Questions)

Is it comfortable to wear?
The most commonly-asked question, with only one answer – try them!
There are several degrees of sophistication when it comes to earpieces. Garwood offers three different earpiece options, produced in a combination of generic and custom-fitted pieces.
Custom-moulding the earpieces increases comfort by ensuring an exact fit in the user’s ear. The safe and easy process of taking silicon impressions is conducted by an audiologist and takes less than 10 minutes.
* IEMII Generic earpieces – the transducers are incorporated within a moulded evoprene (plastic) earpiece to form a single fixed unit.
* Custom earpieces – a more tailored design of earpiece with headphones press-fitted into the soft acrylic shell. The earpiece itself is customized for the user.
* Standard or Custom micro monitors – a different design which encapsulates the same components within an integrated moulded unit, these earpieces feature tuneable ports enabling the amount of ambient sound and bass response to be adjusted. With a purpose-designed cable and Y-collar for extra comfort, this version is ideal for demanding performing schedules.

Can I hear ambient sounds in addition to my mix?
Yes – with generic/standard earpieces, the degree of ambient sound is directly proportionate to the volume setting at the beltpack, and this is controlled by the artist. Top-of-the-range earpieces can be tuned to the user’s preference.

Is the system stereo?
Yes. A switch on the rear panel may be used to select mono mode if required.

Will I still need conventional floor monitors?
No – but you can use them simultaneously if required, but it is important to consider that the risk of feedback may increase. Some users, notably drummers, prefer to support their IEM system with a bass speaker or Shaker to give the low-frequency sensation.

Can a Radio Station feedback like conventional systems?
The system cannot generate feedback because there is no open speaker to feedback into the microphone.

Is there a limiter?
Yes – all the Radio Station models incorporate a variable slope compressor/limiter system.

So what happens if the engineer makes a mistake and overloads the input?
The Radio Station’s compressor/limiter system prevents sound levels exceeding the pre-set safety limit. This helps protect the wearer against sudden volume surges.

With speakers in my ears, won’t the level be louder?
No. In fact the level will be lower. For a start, a lower listening level is possible because the audio mix can be more precise. Secondly, for every user of in-ear monitoring, there is a reduction in the overall sound level generated on stage. This means that your monitor mix doesn’t have to compete with the mixes of your fellow performers. Ironically, the result is a downward spiral of reducing volumes until you reach the absolute (as in the case of Rod Stewart) of no amplification whatsoever on stage.

How can I control the volume?
The discreet belt pack gives you complete control of the volume at all times.

How far away from the transmitter can the artist go?
All Radio Station models have an operating range of up to 100 metres and 330 feet. The Active Antenna system enables the aerial and the Radio Station processor rack unit to be optimally positioned without cable length restrictions and without any loss of transmitted power. This is particularly relevant for large venues where the Radio Station processor would be situated beside the monitor position which itself could be some distance from the performers.

What frequency does the unit operate at?
Any frequency from 510MHz to 865MHz. Actual operating frequencies are governed by the regulatory authorities in different territories, e.g. in the USA a 550MHz band, whereas most of Europe operates in the 855MHz band.

How do I sort out the changes of frequencies if I’m touring internationally?
For the touring act, the best option is the Garwood IDS or TS Radio Station, which incorporate synthesised processors and an on-board portfolio of between 16 and 50 international frequencies. The device will allow the user to select the setting which corresponds to the country in which the unit is to be used – e.g. USA, Holland, Australia. The system will then automatically pre-select a set of legal radio frequency options for that country, and from this list the user can choose his operating frequency.

The frequencies pre-selected by the unit are intermodulation-free so multiple systems can be used simultaneously. The receiver and transmitter will automatically lock to the last used frequency in its memory, giving instant recall for easy operation.

What interface do I need with my console?
The console sees the Radio Station as just another amplifier. Connection is made via XLR input connectors.

Does the unit have to be run in stereo?
No – if there is a shortage of outputs and you can’t generate a stereo mix, the Radio Station has a mono/stereo switch on the rear panel to cater for mono applications.

What happens if I get interference problems?
Radio Station offers multiple on-board operating frequencies; if interference problems do occur, the unit can be switched to an alternative frequency.

5. Health & Safety

Hearing impairment in performers arising from the high levels of foldback used at many concert performances has long been of concern to the medical profession.

Leading audiologists agree that temporary (and permanent) hearing damage is a potential hazard for all musicians. The decision to use in-ear monitoring is the ideal way to reduce this risk and to protect the most precious sense – hearing.

Previously experienced monitoring levels are not necessary when the speaker diaphragm is worn within the ear. As you don’t need to boost the volume to compensate for external spill, a reduction in sound pressure level produces an improved and less distorted signal. The vast majority of users report a reduction or total lack of tinnitus (“ringing in the ears”) after using the system in rehearsal or following performance. However, sensible use of the equipment is recommended in all situations: if you experience an increase in tinnitus after prolonged use, you are probably turning up the gain too high.

Conventional monitors often produce high levels of distortion due to the excessive signal to noise ratio required to mask unwanted sounds. The noise levels experienced during performance using standard monitors often exceeds 110dBA and can reach peaks of 115dBA. Figures published by the UK Health & Safety Executive advise that the average safe period per day that you can be exposed to these peak levels is less than 100 seconds! And this assumes that, for the rest of the day, you are not exposed to any sound levels exceeding 85dBA.

Some people are more susceptible to hearing damage than others so that protection on the basis of an average time and sound level exposure will only protect the ‘average’ person. The decreased listening levels required with in-ear monitoring allow for longer periods of safe listening time.

6. Product range & Accessories

The Radio Station range, incorporating the Radio Station IDS, TS and Classic, is currently the only in-ear monitoring system in the world that is internationally operational.

The Garwood portfolio also includes:

System 3: a lower-cost and slightly less versatile system – principally distinguished from the Radio Station because it is single-channel. The unit is ideally suited to use within a single country rather than international touring because it is built to a single fixed frequency. It has a local monitoring section to allow an engineer to listen to the signal being sent to the artist.

System Plus 2: a dual frequency unit, offering a second frequency within 5Mhz for secure transmission, and built as a smaller package in a 1/2 rack width; this unit is eminently portable and will run off a 12V battery. Other differences include a fixed antenna on the transmitter, and no local monitoring; however, audio quality on the Plus 2 is equal to that of the Radio Stations – and it is at least half the price!

System 2: a single frequency unit, identical to the Plus 2 in all other respects except that it is even more cost-effective!

Hard-wire Systems: not everyone needs the advantages of wireless in-ear monitoring. Drummers, keyboard players and other performers who remain stationary on stage don’t place the same emphasis on freedom of movement as a vocalist or guitarist. However, they can still enjoy the benefits with a hard-wired belt-pack monitor system.

Instead of a wireless beltpack unit receiving a radio signal, the hard-wire systems are connected by cable to a line-level source. Garwood offers two versions, the Outstation (companion to the Radio Stations) and the M-Pack (companion to the System 2).

As with the wireless systems, the wearer has complete control of volume level.

Earpieces: IEMII earpieces, the standard fitting ear plugs supplied with System products, have been designed to fit 99% of ears; they are easy to fit and comfortable to wear. However, for the ultimate in sound quality, there is an upgrade path when it comes to ear-pieces.

First of all, the driver units supplied with IEMIIs can be changed. Popular choices are the Sony and Aiwa models; the rubber seals from IEMIIs fit onto these ear phones.

The next stage is to go to custom-moulded ear pieces, which offer the ultimate in comfort as they are anatomically moulded to the shape of the user’s ear. This version also improves the quality of the perceived sound due to a closer fit to the ear canal giving greater attenuation of unwanted sounds and an increase in the low frequency response. The improved rejection of ambient sounds will also increase the safe listening time because the user will require less volume for the same perceived “loudness”.

To obtain custom-made earpieces, the user will need first to get impressions of his own ears made by an audiologist – a painless and quick procedure which should only be carried out by a qualified professional. First, the ear is fully examined and, if clear of wax, a small cotton block is placed in the ear canal to act as a seal. An impression is then taken by injecting silicon putty into the ear with a special syringe. This is left to harden for a few minutes and then removed. This impression is forwarded to a special laboratory where the final earpiece and transducer will be assembled.

Using these impressions, there are still two options: custom-moulds may be fitted with standard Sony, Aiwa or Garwood drivers. Alternatively, the top-of-the-range ear-pieces are known as Micro Monitors. These units offer identical audio quality, but have the added advantages of being extremely durable and cosmetically more appealing. The system incorporates an internal ambient duct and external port which can be varied to change the level of ambience and bass response. They are available in a variety of skin tones.

c. 1998, Garwood Communications.
From Garwood Communications site. (Republished with permission.)


1 thought on “In-Ear Monitoring.”

  1. […] Wireless in-ear monitor systems can transmit on two carrier bands: VHF or UHF. VHF systems operate between 130Mhz and 250MHz, while UHF systems operate from 450MHz to over 900MHz. UHF systems are more reliable because they are less prone to interference and generally offer more channels (carrier frequencies) than VHF systems. For more information about in-ear monitors, see The Art of Monitoring and Mixing with Headphones and the In-Ear Monitoring White Paper. […]


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