hey guys! a friend has been having some problems with his system. last week his sub would cut in/out and the speakers would play on normally. but now his speakers don't work anymore but his sub does. his speakers are powered by the headunit and the sub is obviously amped.

today he took the fuse out of the power cable to the amp and unplugged the rcas. his speakers still weren't working until he jiggled the front right speaker and then all of a sudden all four speakers played again.

any ideas? thanks in advance!