Hi Terry!
-> Speaking of
-> creative designs, have you ever had the chance to play with one of
-> those theater/auditorium reinforcement systems designed to prevent
-> regenerative feedback by using 100 plus drivers staggered around the
-> audience, and computer switching which drivers are active quickly
-> enough so that any given feedback path based on phasing and room
-> quirks never has time to develop after space delays are included?
 No I haven't Terry, and until now hadn't considered just what would be
needed to make such a system work correctly.. One thing that I would
love to play with sometimes is  phase adjustments on
individual speakers within an array for feedback supression, coverage
pattern shaping, etc..
I've played some with the early Sabine feedback suppression, but that is
trying to find the offending frequencies and stomping on them hard.. The
thing is though, as you keep increasing the sound system to feedback,
much sooner than you will want, the offending peaks are illimated, then
the system will almost feedback on any frequency. You either can't have
enough filters to remove all of the offending frequencies with narrow
notch filters, or you get a frequency response that is riddled with
narrow holes in it, kind of like a field after a artillery shelling.
This is also a compromise point with this system of EQing.
Another technique that can be used in a non musical situation is doing
pitch shifting the sound before hitting the amplifiers just a tad. That
confuses the feedback a little.
Perhaps to me, the most important consideration in getting system
feedback down is NOM, or Number of Open Mics, which directly effects
system feeedback "headroom". We are much too microphone happy now...
Sound consoles now have more inputs than most recording mixdown systems
need with an arsonel of microphones that often makes the studios
envious. Keep that NOM as low as you can at all times.
Bonnie *:>
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