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How to use roving mics at a conference without getting feedback. (Psst... there's MONEY involved!)

Conference sound operators often have to provide 'roving' microphones for questions from the audience. But if the mics are in front of the loudspeakers, won't there be feedback?

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If you want to make money from sound engineering, then the place to be is in corporate events. Part of your work will be setting up systems for corporate hospitality, where you might get a tray of canapés as a free bonus. Another part will be conferences.

This may seem a million miles from the music that you got into sound engineering for, but people working in music mostly make a pittance. Sound engineers working in the corporate arena get their just rewards. (Would Microsoft cut corners on the sound system for a conference? Absolutely not.)

Working sound for a conference is very much like sound for a concert. But there is one distinct difference - conferences often feature questions or comments from the audience.

The sound contractor therefore has to provide at least two roving microphones and operators for delegates to speak into.

Why two? So that while one is in use, the other can be positioned ready for the next person to speak. Operators need to be able to move quickly from one end of the auditorium to the other. A larger auditorium will need more roving mics and more operators.

But now, one of the golden rules of public address has been broken. The roving microphones are in the sound field of the loudspeakers. And if they pick up that sound, feedback is possible.

So how can this conundrum be solved?

It's the same answer as all feedback suppression. The very first step you should take is to position microphones out of the direct line of fire of the loudspeakers. The second is to place the microphones as close to the sound source as possible.

So it is this second step that is of paramount importance here. You can't just point a microphone at a delegate from a distance, not even a rifle microphone.

You have to give the microphone to the delegate to hand hold.

Having the microphone closer to the source of the sound means that the direct sound is very much louder than the return from the loudspeakers. So the gain can be lower and the risk of feedback less.

But what if the delegate holds the mic at a distance, or speaks softly?

Well, what could happen is that the mixing console operator raises the fader, thus also raising the 'loop gain' in the system.

This isn't the best thing to do. The operator should pause before doing this. Hopefully the delegate will realize that he isn't coming through clearly in the loudspeakers and move the mic or speak up.

If he or she doesn't, then the roving mic operator needs to make some convincing hand gestures to get the mic in the right place.

What's the worst thing that can happen, apart from feedback?

Answer - the conference chairperson asking the delegate to speak up. If this happens, it should be regarded as a failure in the sound department. Sound engineering should be as transparent as possible, and if a problem has to be pointed out by the chairperson, who is probably important enough to earn a squillion dollars a year, then it's a significant error.

I've done my share of time with roving microphones.

Does anyone else have any tips, or horror stories?

By David Mellor Monday August 7, 2006
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