Infrared Wireless Microphone Systems
May 6, 2010 12:00 PM, By Bennett Liles
The Panasonic infrared wireless microphone series consists of the WX-LT350 pendant microphone, the WX-LT150 handheld microphone, the WX-LZ150 battery charger for microphones, the WX-LS100 infrared ceiling sensor, the WS-EC10 ceiling loudspeaker, and a choice of three receiver models. The WX-LA50 is a 2-channel IR tuner with a built-in 50W amplifier and four line inputs along with eight loudspeaker connections. The WX-LA20 receiver has a 2-channel tuner, four loudspeaker connections, and two line inputs. Either of these models can be connected with the WX-LR100 receiver to add two more channels for 4-channel operation. In addition, as a portable all-in-one model, the WX-LP100 has a 2-channel tuner, two line inputs, and one built-in loudspeaker. Working in the 850-nanometer wavelength range, the microphones can transmit on 2.3MHz, 2.8MHz, 3.2MHz, or 3.8MHz PFL synthesizer-selected channels to the sensor up to 8 meters away. The microphones are unidirectional electret condenser types, and they can operate on one AA dry element or nickel metal hydride rechargeable battery for up to 6 hours or an alkaline AA battery for about 5 hours. When switched on, the battery indicator LED on the microphone will show green for normal battery condition, orange for a low-battery warning, and red for a battery-depleted or battery-change warning.
TeachLogic offers the Maxim II system as an all-around sound-control system for two IR wireless mics and three other audio sources. The IMA-420 receiver has separate level controls for each wireless mic channel and controls for computer, DVD/TV, and auxiliary sound sources. In addition, it has a rear-panel 5-band graphic equalizer and a paging input from 25V, 70V, or 100V systems that automatically mutes other sources when a paging signal is present, and there are two 16W power amp outputs. The front panel includes a line-level output with a level control. Microphones include the IRH-30N handheld mic/transmitter, the IRT-89 pendant mic, the IRB-30 body-pack transmitter with a volume control and external audio input, and the IRT-30 crescent neck-worn microphone/transmitter. There are drop-in chargers for the body-pack transmitter and handheld mics.
The latest infrared wireless microphone system from TOA Electronics includes the IR-200M handheld microphone, the IR-300M neck-worn mic/transmitter with an internal mic and connection for an external lapel mic, and the IR-702T 2-channel infrared wireless tuner operating on 3.1MHz and 3.5MHz. The tuner has two outputs, one of which has a channel-mix switch. For larger systems, the IR-700D infrared wireless distributor, used in conjunction with the YW-1022 or YW-1024 distributor, can allow up to 16 IR receivers to be used. These may be the IR-500 wall-mount, the IR-510R ceiling-mount, or the IR-520R wall- or stand-mount receivers. The microphones can use two AA alkaline batteries, or with the IR-200BC charger, rechargeable batteries may be used.
Wall- and ceiling-mounted IR sensors work best when shielded from bright sunlight coming in through windows, but they can use reflected infrared light from the transmitter so mounting sensors on a black, light absorbent surface is not recommended.
Incandescent lamps emit light that is near infrared and can sometimes interfere with IR sensors directly exposed at short distances, but mercury or fluorescent lighting should pose few if any problems.
Multiple sensors will most likely be needed in order to maintain line of sight no matter which way the presenter turns. One on the wall behind the presenter and one on the ceiling in front is a good starting scheme. Some experimentation in specific environments will be necessary.
These, like microphones, have specific IR pickup patterns that should be used to best advantage in dealing with specific lighting conditions.
Sensors are usually connected to IR tuners with coaxial cable such as RG-59. With multiple sensors, the cable length from each to the tuner should be equal. Total signal attenuation should not exceed 12dB. B.L.
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