that you must be directly in front of the mic to optimize input. What you're describing, if I understand correctly, is probably as Steve describes OR... and I've seen this but rarely, they had a sound man that could control the mic output... so when the singer turns to the side to face him he kills the output to the main speakers but he can still can hear thru his headphones. But again, I've seen that VERY rarely. - JamesJM
