oh yeah, and loud subs wont harm your hearing, low tones dont make you deaf, the high tones do. as long as he doesnt take his 6x9's or whatever he has not too loud he wont have to worry. all the electric guitarists are now near deaf, but the bassists and the drummers are fine and dandy. That, plus the fact that bose engineers did a study of it in combination with the science department at one of those ivy league colleges makes it pretty safe to assume he shoudl be ok.