AW: loop-based installations

["Rainer Thelonius Balthasar Straschill" <rs@moinlabs.de>]

> Since you work with microphones I can give one advice, 
> emanating from my own mistakes in the past ;-)  Watch out 
> with standing resonance peaks in the room! It won't be 
> dangerous if you stick with "feedback = 0" but if using a 
> little more feedback it might bring some unpleasant surprises 
> after a couple of hours installation time. 

Says Barkhausen: resonances require a gain >1 to build up. (second
Barkhausen condition)
Of course, it depends on the different layers of feedback - one feedback
chain is within your looper, the other one being through the room. And I
encountered resonances even with feedback (of the looper) =0 in a setup 
like
this:

Mic 1: Shotgun mic pointed at a restaurant at the other side of the street
Mic 2: Living Room
Mic 3: Kitchen (adjacent to corridor)
Mic 4: Bedroom

Speaker 1/2: Living Room
Speaker 3: Corridor
Speaker 4: Bedroom

4 Loopers (Ellotronix), 5 insert effect chains. Compressors and lowcut per
mic channel, brickwall per output channel.

A first simplified implementation looked like this:
Mic 2 -> Looper 1 -> Speaker 3
Mic 3 -> Looper 2 -> Speaker 4
Mic 4 -> Looper 3 -> Speaker 1

Now again: something which allows me to control these resonances, apart 
from
"hearing them out" and placing parametric EQs in the signal chain? The
often-wanted feedback destroyer as a VST? Would dynamically changing the
length of the looper (thus changing phi(f)=2*Pi*n around the loop, the 
first
Barkhausen condition) work around this problem? Would I need a looper which
"pitch changes" (like the old PDS/RDS ones) for this - if so, which VST is
good for that?

        Rainer