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Technology Showcase: Wireless In-ear Monitoring Systems

Jul 1, 2008 12:00 PM, By Bennett Liles

Today's systems make performers masters of their own monitoring environments.

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In 1990, only the top names in musical entertainment could be seen using in-ear monitoring systems. But in the time since then, these devices have rapidly spread through the ranks — and now practically any pro or semi-pro vocalist or musician can afford them. The earlier version of personal monitoring took the recording studio design and simply moved it onstage with one or more headphone amplifiers snaking their outputs around the stage to each musician, but vocalists and other highly mobile performers had to stick to their floor wedges blasting the stage with acoustic power.

As the substantial advantages of in-ear monitoring systems won more converts, the wireless microphone companies took notice and developed lines of equipment built on their existing technology to reverse the wireless transmission process and send monitor mixes back to the performers. Improved sound quality and stereo imaging, elimination of feedback, and ultimate portability are just a few of the big steps up that were provided to performers — and it was clear by the mid-'90s that they weren't going back.

FOH and monitoring technicians reaped the advantages of less bleed-over into adjacent mics and less mind-numbing feedback. The more recent addition of personal monitor mixers and digital audio networks carrying 16, 32, or more channels of uncompressed PCM audio into those in-ear monitors has made each performer the master of his or her own monitoring environment while freeing the tech to concentrate on equipment performance and FOH mixing. Here, we take a plunge into the world of in-ear monitoring systems and have a look at the workings and features.


The AKG IVM 4 system consists of the SST 4 stereo transmitter, the SPR 4 body-pack receiver, one pair of IP 2 ear buds with three pairs of ear molds, a rod antenna, a rackmounting kit, power supply, batteries, and a 12-piece color-coding kit. The SST 4 transmits stereo sound on one of 1,200 channels between 500MHz and 860MHz. The SST4 also features an integrated compressor, a limiter, a high-pass filter, and a dedicated binaural room simulator. The rotary headphone volume control knob is combined with a push-push function for power on and off. The LC display shows all the setup parameters — including compressor and limiter gain reduction; menus for frequency, transmitter name, input gain, and audio processing; along with submenus for frequency group assignment, sub-channel, and RF output. There is also an input level bar graph and a red peak LED indicator. The rear panel has loop jacks for left and right audio channels that are connected in parallel with the audio in connectors. A 1/4in. TRS jack carries the processed stereo output sound. The SPR 4 body-pack receiver unit has a mini TRS jack for ear-bud connection and a rotary on/off switch and volume control for the ear buds, and it includes a permanently mounted receiver antenna and status LED. The battery compartment can accept either a pair of AA batteries or the optional rechargeable BP 4000 battery pack to be used with the CU 4000 charger.

Audio-Technica M3

Audio-Technica M3

The M3 wireless in-ear monitor system from Audio-Technica offers a choice of 1321 UHF channels shown on the backlit front panel LED display. Up to 16 M3 systems may be used simultaneously in pre-coordinated frequency groups. The MT3 stereo transmitter has versatile combination 1/4in./XLR input connectors on the rear panel along with XLR loop output connectors and attenuation switches. The front panel has a 1/4in. headphone output with volume control, and a selectable auxiliary input offers a connection point for an ambient microphone, click track, or other mic- or line-level input. The multilevel limiter serves to protect hearing and the pilot tone muting system works just like those on wireless microphones to prevent unwanted transmissions from entering the system when the transmitter is turned off. The double-conversion superheterodyne M3R stereo receiver can be operated in any of three modes including personal mix — in which the user can adjust the monitored mix, stereo, and mono modes. In personal-mix mode, the balance control can be rotated to the right to hear more band level and to the left to hear more vocal or instrument of choice in both ears. An advanced stereo setup using multiple audience microphones and aux outputs from the mixer can also be configured. The headphone output is 65mW at 32V, and the aux input connector is a 3.5mm TRS stereo phone jack. The unit can operate for up to eight hours on one pair of alkaline AA batteries.

Galaxy Audio AS-1000 Any Spot

Galaxy Audio AS-1000 Any Spot

The IMS 900 in-ear monitoring system from Beyerdynamic includes the SE 900 stereo transmitter, the TE 900 stereo receiver, a transmitter antenna, and DT 60 Pro earphones. In each 24MHz bandwidth, there are 16 pre-coordinated channels in which the transmitter can operate. The rear panel contains two audio-input combination balanced/unbalanced connectors, two 1/4in. loop outputs, a 50V BNC antenna connector, and the 12VDC power connector. The front panel features the central green LC display, separate left and right audio-input level meters, menu-navigation buttons, and power switch — along with headphone jack and volume control. The top LED on each meter is red and indicates clipping and distortion. There is also a rackmount kit with connections for a remotely mounted transmitter antenna. A balanced or unbalanced line level audio input signal can be applied to the XLR connectors and an unbalanced line level signal can go into the 6.35mm jack socket. The menu-navigation buttons can be used for setting the transmitter frequency, mono or stereo operation, transmitter name labeling, input sensitivity and the panel-control lock function. The TE 900 receiver has indicators for RF level and a left/right balance control, channel selector button, limiter switch, and a combination power switch and volume control.

Longtime monitor manufacturer Galaxy Audio markets the AS-1000 Any Spot wireless personal monitor to replace floor wedges and operate from the monitor out jack on a mixing console. The system has 64 selectable UHF frequencies, and the AS-1000T transmitter is selectable for either mono or stereo operation. The AS-1000R body-pack receiver operates on a diversity reception system with two antennas and has an auto-mute feature that senses any dropout and prevents any static from being heard by the user. Also intended as an assistive-listening system, the transmitter can send its signal to multiple receivers. The transmitter unit's rear panel includes RCA, XLR, and 1/4in. input connections, and it offers simultaneous use of two sources with separate line- and mic-level controls on the front panel. The front also features a power button, a frequency display with group and channel selection knobs, a headphone jack with level-control knob, and an LED peak indicator. The system's 64 channels range from 682MHz to 698MHz, and it exhibits a signal-to-noise ratio greater than 94dB at 15kHz deviation and 60dBuV antenna input. Audio frequency response to the headphone output is 100Hz to 10kHz ±3dB, and the line audio response is 40Hz to 15kHz ±3dB. The unit's dynamic range is greater than 96dB, the headphone output level is 20mW, and the line stereo output level is -10dB. The receiver operates on two AA batteries or rechargeable batteries.

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