Our barn dance band plays in a lot of different venues. We have 4 DIs and a wireless mic for the caller. Some places give us no sound problems at all, and they are often the older venues like town halls etc. However, some venues give us no end of feedback problems, usually if there are hard floors, shiny or glass walls and/or high pointed ceilings with beams. The newer village halls are usually the worst. It's the mic which is the problem, as the instruments are always ok. We have an EQ box, but I'm not sure we are using it correctly. Any technical advice would be very welcome.