Car: 2008 Mustang GT/California Special
Shaker 500 system (stock everything, originally)

Issue: Driving one day when my sound became extremely muffled. I powered down my head unit and when I powered it back on, my front right door speaker popped once. Additionally, it appeared to generate no audio.

Took door apart, discovered that the speaker coil was energizing and staying energized. Thought the crappy factory speakers had gone bad so I purchased some replacement Infinity Reference 6832 for the doors only.

Couple of days later, I realized a troubleshooting brain fart and tried turning on the stereo with the "bad" speaker uninstalled. I discovered that the audio was still extremely muffled, but would occasionally return to normal levels for up to 2 seconds. I drove it with 3 speakers only for a week, and the situation persisted.

I took apart the dash, removed the head unit, and checked for loose connections. I also checked the amp connections in the front left kick panel area, but all 3 remaining speakers were muffled, leading me to believe it's from their common source. At any rate, I found nothing obviously wrong with the wiring/connections.

When I finally put in the new speakers, the same issue remained. The front right speaker coil would remain energized upon power up of the head unit.

So, Thoughts? Is my head unit done? Anything else I can look for? Is it worthwhile to try and look for a loose connection or bad component (voltage regulator maybe? because of the popping on power up and all...) in the head unit itself?

I have a voltmeter and some other stuff for diag/repair purposes. What I don't have is ANY experience in audio systems.

Any help is greatly appreciated!

 

Based on what you've done thus far, it sounds as if you're HU is going south honestly. It's well known they're crap. The common source you're looking for is the HU, unless there's a stray short in the harness somewhere that could possibly be causing the muffled sound on all channels. You're stock Shaker setup shouldn't pop either, but yours is not the first time I've heard of that happening on a completely stock Shaker 500.

 

Stick a fork in it. You could tear the shaker apart if you want, but even the short while it would take someone with a service schematic to figure out the components to replace it just wouldn't be worth it.

Same year and make car, I just have the extra rear subs and amp. Plan on the POS "shaker amp" for the 2 door subs to croak down the road as well. I left the stock "shaker" amps/speakers in place for my 1000 setup, the door shaker speakers now fade in and out, get RFI from the alternator at random, etc... Just a slow, and very annoying death. Rear is still good, for now, but I don't expect that to last much longer either.