Wayne Parham Messages: 18796 Registered: January 2001
Illuminati (33rd Degree)
Feedback is usually caused by the amplified sound reaching the microphone, and that's always made much worse if the speakers are placed where they direct sound into the microphone. So my first thought is to try to solve the problem with placement.
If the speakers are placed away from the microphone - out in front, facing the audience - and the stage with the performers are behind those speakers, that will probably help.
It might also help to use a directional microphone rather than one that is omnidirectional. If your microphone is an omni mic, you might have better results switching to a cardioid.