Hello all, my name is Garth and I am a new member and a sound beginner. I am a volunteer at 2 high schools in MD and do well with lighting, but on sound I know just enough to be dangerous. The school is doing My Fair Lady with a 14' thrust beyond the normal stage position. There is a pod of 3 center speakers and 8 small side speakers along the walls (4 per side). Whenever the students walk out onto the thrust with in 20' of the speakers on the audience side, we get a lot of feedback. We are using Shure lavalier mics. Any suggestions to make the feedback stop? Thank you.