i bought a used mach rcu and tweeters from a member here awhile back. everything seemed to be ok. recently, though, the sound is not as loud as it used to be. the lf is definately still going strong, but the rf , and 2 rears are not. i can move the sound to each individual speaker, and they all work, but only the lf is mach loud now! i don't think i blew the speakers, though that would be an easy fix. i would assume they wouldn't work at all if i did. any thoughts?