things acting up....
 

my rear speakers stopped working, and now my tweeters are fading out (the vibrate like hell, sounds like they are trying to play all the bass). These are factory speakers with a aftermarket HU. any ideas? (one comes to mind that the HU is overpowering for the factory speakers...)

doubtful. our factory speakers aren't crap (just aren't good)

i'd check your wiring. The heat might also be playing with your headunit....

lastly, check the setting on your h.u (stupid suggestion, but can also just be messed)

I checked. the fade is spread evenly between front and back.
The speakers were working when I first installed the HU, which was back in April. The rear speakers stopped working around last week, and the tweeters started acting up yesterday.

ok, did you wrap the wiring w/ the new h.u or did you solder them? if you wrapped them, the tape might have come loose, or the twisting came apart some. (i'm also guilty here, i twisted instead of soldered. i gotta fix that eventually)

i'd throw a voltmeter across the connections on the back speakers (checking for AC currrent) to see if the leads have any. if they do, the speakers are shot. if they don't, then the h.u isn't working, or you have a short in your wiring somewhere.