We just had a nightmare gig where we couldn't turn our system up loud enough to compensate for the crowded bar noise. Yeah, we were background music but we didn't want to be so much in the background that people didn't even know we were there. Problem was, everytime we tried to crank up the volume, we'd get low frequency feedback. We even have Behringer Feedback Destroyers, one for the monitors and one for the mains. Each was set on Setting 3, to automatically find and destroy frequencies leading to feedback. We have good equipment that should have been plenty powerful enough. Our volume was so low that some of the crowd was standing directly (almost leaning against) in front of our mains. The problem did not seem to be affected by the crowd size or proximity of people to our speakers. Does anyone know if we were doing something terribly wrong or forgetting something? We set up the monitor sound first and had no feedback problems and plenty of volume. This leads us to think we were getting a bunch of reflective sound from the mains. The room is very live, wooden ceilings and floors with funny walls here and there for noise to bounce off of. We tried raising and lowering the speakers to compensate for possible ceiling backwash, to no avail. It wasn't that we just weren't loud enough, we couldn't crank the volume even up to the board's unity setting. There are so many factors involved and so many places to turn up volume that I am now confusing myself. Does turning the speaker volume knobs up affect sound differently than turning the board's main faders up? How about individual channel trim vs. overall sound with the main fader? As I am typing, I realize that I just have more and more questions. Bottom line is, I don't want to have to go through such a horrible night again. If you can offer advise, it will be most welcome. If you want more sound system details, I will gladly include them.