Saturday during sound check I was getting low end feedback from the kick drum. My board has 4 band variable mid eq on each channel,so I was able to find the offending frequency.But,cutting that frequency also killed the sound of the drum. The drummer insists that I'm doing something wrong,but the only variable was that he played a different drumkit than usual. I could touch the front head on the drum and the resonance went away. Finally got it where it was just usable and we got through the gig ok. He doesn't have a proper set of drum mics, so I'm going to start there. Any ideas on how to prevent this happening,or fix it if it does happen again?