I'm having a somewhat strange audio problem that I can't seem to track down. Before I start explaining the issue, I've tried the factory radio as we as my aftermarket Alpine and still have the same issue.
I had previously replaced the factory speakers with Polk speakers which seemed fine and never had a problem. Those speakers have seen better days and needed to be replaced so I bought some pioneer replacement speakers from crutch field, which came with the mounting brackets and wiring harness. They seemed fine until the other day. I'm having an issue with the audio randomly dropping off completely. No sound at all. I turn the radio off and then back on and get a muffled pop from one of the speakers...and no audio at all. I popped off the door panel, tested the impedence on the speaker with a multimeter, and then it works fine.
I'm not sure what's causing the audio to randomly drop...and it's driving me crazy because it won't come back on until I pop off the door panel and mess with the connection. Anyone have any ideas?

 

Sounds like a loose connection behind the speaker, I would pull the door speakers and redo the wire connection to each terminal with spade terminals and heat shrink.

 

Thats how they're connected now. That was my first thought... But even if it was a loose connection, would it cause the other speakers to also be silent?

 

I'd pull the speakers double check the leads that run from the terminals into the cone to the voice coil. If there is a problem there could be it, sounds very strange since you have tried different head units and gotten the same issue.

 

Good thought