Basically a
feedback eliminator is a combination of a
RTA real time analyser and a narrow band filtering program. The new ones work by converting your analog signal to digital, doing the analysis and the filtering, and then convert it back to analog. Behringer has one, and Sabine is probably the leader in this type of technology.
Problem with when sound companies set up stuff for schools is that they do the quick and dirty, one size fits all type of deal, with the idea that the operator will be totally a Noob.
Feedback comes more from placement of the mic with regard to the speakers, and also clothing, hands
etc by the mic
element. Sure some of the non linearities of the mic come into
play but they are minor.
The problem with the auto systems is that they are non intelligent and can have a tendancy to over correct or get confused with a frequency in the program vs a feed back frequency. So most pro setups use the FBE as a last resort, emergency protection AFTER they have properly run out the monitors. You will hear people talking about a systems
GBF Gain before
feedback, which really will determine how loud your
system will actually be able to operate at on live mic'ed inputs, vs pre recorded.
I suggest you ring out the
system first, using a Graphic eq, and make sure you resent and
clear all the pre set filter notches so that the FBE is going to work on exceptions on your
system.
When you ring out the
system make sure you work mic by mic first in all the positions it is going to be used, and then check by bringing up and adding the additional mics to make sure you are still ok.
A trick on some mics is if they are directional is to have the mic
face DOWN on the person especially if you are not using monitors
Sharyn