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Re: Open mics + Looper + Live=Feedback?

At 9:56 AM -0500 4/3/02, Christopher White wrote:
>recently i have been working on a project at home that involves 5 
>open mics... what possible problems should i look for?

Assuming the rest of your acoustic instrumental battery is comparable 
to the Waterphone with respect to dynamics, you probably don't have 
much to worry about as long as you observe some basic sound 
reinforcement practices:

Keep your mics out of the sound field of the speakers. If you're 
using directional mics and you're using stage monitor speakers, keep 
the the mics pointed away from the speakers.

Keep the mics as close as is practical to the sound sources.

If multiple directional mics are placed near to each other, be 
careful of phase cancellation effects. Pan them to opposite sides of 
a stereo mix. If you're mixing in mono and there's a problem, try 
flipping polarity on one mic, or try using mismatched mics.

If you're using dynamic mics, be aware of proximity effect (more bass 
sensitivity closer to the mic).

Watch out for resonances in the performance area. [True story - I was 
once called on to help get rid of a feedback problem for a Phil Glass 
piece for amplified tympani and amplified double bass. The 
instruments were set up in a tiny shoe box shaped stage area in a 
multifunction room. The sound reinforcement system provided consisted 
of a pair of vocal mics plugged into a pair of Peavey guitar amps. 
All I could do was to turn the amps so the speakers didn't point 
directly toward the mics and then use the woefully inadequate amp 
tone controls to roll off problem frequencies. I got rid of the 
feedback at the expense of most of the tone of the bass. After the 
performance Phil remarked that he'd never heard a bass sound like a 
Farfisa organ before.

If you have a set of noise gates you could try putting them into the 
inserts of the mixer input channels.

PS - I'll be doing a presentation for EAAA in Atlanta on May 20.

Richard Zvonar, PhD
(818) 788-2202