|
Mixers: Automatic Mixers
The function of an automatic mixer is to automatically turn microphones on and off. The automatic mixer's primary use is for speech microphones such as pulpit, lectern and wireless.
Turn Off Microphones? Turning off unused microphones improves sound quality. Three reasons sound quality improves are highlighted below. 1. The NOM [Number of Open (on) Microphones] principle states, "For every doubling of the Number of Open Microphones, the sound system will have 3 dB less gain before feedback."So if the microphones that aren't being used are turned off, the sound system can be turned up louder before the system begins to feedback.
2. Reducing the number of open microphones improves the clarity and naturalness of the reproduced sound. Regardless if the microphone is being used or not, too many open microphones often results in a hollow sound.
3. Turning off unused microphones reduces interference effects between microphones.
A Classic Scenario… An usher arrives early to turn on the sound system. He turns up each volume control to the appropriate level and then goes about his other duties. During the service, a lay person reads the scripture from a lectern microphone. Their voice sounds full and natural. Unfortunately, the lay reader forgets to turn the microphone off. Later in the service, the pastor stands in front and turns on his wireless lavalier. Suddenly, the congregation hears feedback. The obvious but wrong conclusion is that the pastor's wireless lavalier microphone has gone bad. The correct reason is the lectern, pulpit and wireless lavalier microphones are all on. The feedback is a result of the NOM being too high.
What's the Solution? As you have probably guessed, one solution is an automatic mixer. A well-designed automatic mixer will provide the following benefits to a church sound system:
1. When someone starts to use a microphone, the automatic mixer will open it. It turns on very fast so no words are missed or clipped.
2. If multiple microphones are needed, the automatic mixer reduces the over-all volume level so the potential for feedback reduces and clarity improves.
3. Many automatic mixers allow you to prioritize which microphone gets turned on first. 
There are many types of automatic mixers.
Are There Limitations? In most cases, a combination of both an automatic mixer for the speech microphones and a conventional mixer for everything else is the best solution. This allows an operator to do live mixing for music and productions.
Because automatic mixers do not adjust the balance between microphones, they are not a good choice for music applications.
Most automatic mixers do not have individual tone controls for each microphone input. Therefore, it may be necessary to use an individual 1/3 octave or parametric equalizer for microphones dedicated to an automatic mixer. Typically, the microphones assigned to an automatic mixer are the same microphones that need the most equalization for natural sound.
Other Benefits Audio and video recordings also benefit by an automatic mixer. An automatic mixer, along with an automatic leveler, eliminates the need for an operator to constantly monitor the recording. This allows their concentration to be where it should. And for those events that don't need an operator, a good quality recording could still be achieved.
Summary
Several types of automatic mixers are available. Once installed, the system is simple to operate. The selection of this type requires an experienced professional. by Travis Ludwig © 1996 Internet Sound Institute (www.soundinstitute.com). This article is for personal use only. Any commercial reproduction is not permitted without permission. To obtain permission, contact ISI at hopi@soundinstitute.com
< Back
|
