First of all, you are dealing with teenagers who know that they didnt
purchase the equipment, therefore they could care less if it breaks. So, telling them how much the gear costs will do you no good. Once you have told them that
feedback is taxing on a sound
system, you have done all that you need to do as far as warnings are concerned. When they do it again you simply remove their wedges, and they will be forced to perform old-school. No use getting upset over the
feedback...just do what you need to do to protect the gear. Purposefull
feedback is abuse.
I had a gig with a band whose lead singer would get so angry on
stage that throwing the
microphone on the floor was commonplace. They were my mics. I fixed the problem in the next tune by replacing my now-dented Beta 58 with an nasty old Realistic
switch mic whose grill smelled like 10 week old tuna. You CANNOT teach respect, but you can control the damage.
By the way, EVERY sound company should carry an old tuna-smelling
microphone in their arsenal for just these occassions.
Sean Loughry
Freelance Audio Engineer