its usually the amp, not the speaker. since they are amplified speakers, you have to have the whole amp removed, not just the speaker. its a cheap fix, you just have to send it off to boses and they rebuild it for you(actually i think they send you one already rebuilt because the turn time is quick.
apparently it is a common problem, my passenger side and center have already gone out. you can tell its the amp if youre getting a really hissy whiny feedback from the speaker. you can use the search and find a lot of other owners whove had the same thing.
good luck and welcome to the forum