i have a JBL GTO638 speaker in my front door and recently it started not working so i took it out and saw the negative had come off. I removed the annoyed factory clips that attach to the speaker terminal and put a different clip on. That one didnt work at all so i tried bare wire. This worked sometimes but only when i a certain position in the speaker harness. Now its not working at all and has a squeal that gets louder when i accelerate

 

Check how secure your amp ground is. Also check the power in trunk and near battery. You described alternator whine, but not sure why it's not working.

 

Pics if ya can...