More about monitors & feedback

Another thought on last week’s (see inSync 6/23/00) problem of feedback from one of our inSync readers. If you have speakers and/or microphones out of phase (polarity) you can actually make feedback worse. We suggested this as a possible trick to remedy feedback problems, but never really mentioned it as a possible cause. In any PA/monitor system you always want to be working from a known good reference point. This means everything in phase. Make sure of the polarity of all your mic and signal cables. Obviously make sure your speakers and speaker cables maintain correct polarity. Be aware of what your crossover is doing. Some crossovers invert the polarity of one or more of their outputs (this is usually only in older models, but you have to watch out for it). Once you get your entire system wired properly you can then try some polarity reversing tricks to minimize feedback. A common one (as mentioned last week) is to run some or all of the stage monitors backwards from the main PA. This can sometimes minimize how much they reinforce each other and trigger feedback. Likewise you can just wire the monitor woofers backwards (leaving the horns connected normally) for improved results. Usually these techniques work best in small setups. On large concert stages the benefits are negligible. There is no one answer for all situations. It is a trial and error process, and can even be different from room to room.