My recent experience is on the club circuit in South Wales.

There is usually a single singer with backing tracks, surely the simplest possible setup. But STILL almost everybody (or often his wife at the controls) turns up the bass, treble and reverb to maximum, and ends up distorted as hell and singing in the bathroom.

Mrs Pavane won't let me advise (Quite rightly, I suppose, no-one likes a smart-ass, but how else will they ever find out how much better they could sound if no-one tells them?)

(However, I must say that a music shop tried to sell me a speaker which had an audible buzz, so maybe they also don't know any better.)