Thanks, Kyle. I'm thinking that I simply have something too hot in my mix when I open the gain on the Bose system (I usually use a mixer, and at the moment we have only one L1/B1 system). Then, as I tweak in all of the signals, I get the sound I'm looking for without feedback.
We're typically using Shure SM-58 mics (typically only 2 or 3). I begin with the master down on the Bose system, setting the trim just below peaking on the loudest inputs. Then, I do indeed leave the trim settings alone and control levels from the remote. But I think the feedback often comes from one of the acoustic instruments with on-board piezo pickups. At any one time, we might have a mandolin, a dobro, a dreadnaught guitar, a nylon-string guitar, a fiddle, an upright bass, a banjo, or a Portuguese guitar in the mix.
I'm using this system with three different acoustic-style bands at the moment, so repeatablity is a bit of an issue :-)
Thursday night one of the groups (http://www.eklectica-band.com
) played an outdoor concert from a gazebo stage in a park. Because the structure seemed to be trapping the sound, I opted to put the PAS out in front of us -- outside the gazebo, actually. Then, we introduced floor monitors to let us hear what was going on. There were no individual instrument amplifiers, but we had degenerated to a house-and-band-monitors setup. It worked okay, and the crowd really liked the sound, but from a player's perspective I don't think I'll take that approach again. If I had another tower in the same circumstances, I'd try having one on either side of us near the railing and, if feedback became a problem, put them outside the gazebo and just use the sound coming from the back of the tower as monitor.
Those floor monitors -- what can I say? -- they suck. And, since I'm mixing from the stage, it was disconcerting not to be hearing exactly what the audience heard. I guest this means I'm a firm convert to the Bose Way!