i use a peavy EQ with feedback locator, lights up the freq that is feeding back. best i have found. i have behringer feedback destroyers and a peavy feedback ferrett they will slowly shut down each freq till you have to turn it off and back on again. (slowly shuting down your system) so i only use them on my floor monitors.
peavy EQ is the way to go. easy to use and very good at fighting feedback.
hope this helps. Bob
