I mix several worship services, but recently had a chance to enjoy a couple of productions from the audience’s perspective (a rare experience!).
As an audience member, I was soon reminded of the fact that audio techs sometimes forget (or just don’t know) about audio gain staging for wireless microphones. The clipped (overloaded, distorted) sound on the wireless head-worn microphones during loud vocal passages was certainly distracting—no one wants to hear that!
Audio people soon learn that every sound system is a signal chain and that the gain structure for each device in that chain (source, mixer, processor, amplifier, etc.) must be optimally set. If the audio gain structure of just one device is slightly off, a clipped or noisy audio signal can result.
Wireless microphone systems are similar in that they also have a signal chain in which each gain setting must be properly set up. The difference is that part of the chain is on stage, and not physically connected (hey, its wireless!).
Whether it is a handheld, bodypack, or a plug-on style, the RF transmitter has an audio input. Headworn microphones, hand-held vocal microphones, electronic instruments, lavalier mics and other items might be plugged in. All of these, with their respective sound sources and varied applications, represent a wide range of signal levels.
The radio link is designed to have as much dynamic range as possible. Well over 100 dB is common by current standards. And to take advantage of that, the audio signal applied to the transmitter must be gained appropriately.
We want our audio signal to use as much as of the dynamic range as possible, but not quite so much as to clip the signal. (Sound familiar? It’s not unlike gain structure in other audio devices.)
Manufacturers can’t possibly preset a “one size fits all” sensitivity/gain setting here, as the range of applications is too broad. So, the audio frequency (AF) sensitivity control is provided to allow the user to correctly optimize the system for the application. It may be in the form of a switch in fixed steps, a potentiometer, or a software adjustment. It may be a very course adjustment or allow extremely fine control.
