stereo strangeness

2010 Tacoma TRD with the JBL goodies as original equipment.

In 2018 I upgraded the speakers with the Rockford fosgate drop-in kit that was popular at the time, can't seem to find the thread now about it though.

Worked fine until late last year. Had one day where the sound was really quiet and muddled and then it worked for two weeks and went back to the quiet muddled permanently. I figured I probably killed it over the 14 years.

For Christmas I picked up and Alpine head unit from crutchfield with all the adapters for harnesses, dash kit and so on. So I'm using all the stock wiring. This may be important later.

Got around to installing that in April. Sound was still quiet and muddled but I could now understand voices. I figured that it wasn't just a blown head unit but it blew the speakers when it died. So I just got around replacing the speakers and it worked and then it went back to being muddled. Fiddled around with the wires to make sure nothing was stressed and it worked until I started closing doors and it went back to quiet and muddled.

So now I'm thinking I've got a wiring problem somewhere but I don't know where that would be or what to look for or if there's a known harness that likes to get crunched or known to fail over time?

Any suggestions to troubleshoot this? I really don't want to bypass all the stock wiring but I guess I can if I have to.

 

Shot in the dark here, not very familiar with the JBL setup but doesnt that use its own standalone amplifier? If so, could be a bad connection to that. Either speaker connections between amp and HU, or maybe a bad ground for the amp.

Or maybe the amp itself took a dump, either from getting cooked or there are failing/corroded connections. You can test all the wiring between the HU harness and amp harness with an ohmmeter and see if there any problems there; likewise the wiring between the amp and each speaker, make sure none are shorted to each other since you mentioned that shutting doors affects the problem. Also check the power and ground connections to the amp. If all the wiring looks good, and you know the HU and speakers are good, it's gotta be a bad amp

Is it possible you used speakers of the wrong impedance for the JBL amp when you upgraded?

 

The speakers I used both times were 4 ohms. As the system ran 5 years on the replacement speakers I don't think that was the problem. I'll see what I can find out about the separate amplifier. I think that's only for the subwoofer but I don't know for sure.

 

Found this thread on the wiring for the JBL amp, looks like the speakers are indeed fed by the amplifier.

https://www.tacomaworld.com/threads/the-elusive-jbl-amp-wiring-diagram.262892/

From what little research I did, it seems like the JBL amp and stock JBL HU are meant to work as a pair, and replacing either unit with aftermarket requires bypassing/replacing the entire system. The JBL amp apparently does a bunch of electronical equalizing wizardry to whatever black magic digital/analog signals it gets from the stock head unit. Maybe working briefly on the Alpine HU was a fluke based on volume levels or something? I'm not sure.

But either way the consensus seems to be it's easier to just bypass the JBL amp if you're going aftermarket. And a muddled sound from all speakers def sounds like a bad amp to me anyway.

 

Also just stumbled on another thread saying the OEM JBL setup uses 2ohm speakers. So I’d guess using the 4ohm speakers is what cooked the amp.

 

I think it depends on the year, from what I was able to find out when I was considering changing speakers: '05~'15 use 4ohm and they went down to 2 ohm after that.
https://www.crutchfield.com/S-kYAqCucKXBC/learn/2005-2015-toyota-tacoma-double-cab.html

THe whole thing was kind of confusing, the info is all over the place

 

A quick check would be to take a speaker and run a wire direct to the alpine unit. If it works, then the amp is likely the issue.

 

Ahh okay. Yeah the whole JBL setup seems like a bunch of secret-squirrel proprietary nonsense. I’d personally rather(and did) install my own speaker wiring, run RCA cables to an aftermarket amp, bypass the whole OEM system altogether and call it a win. It’s not terribly difficult, worst part is fishing the wires through the doorjambs. And I didn’t even bother wiring in the rear headliner “speakers” (access cab) since they’re garbage anyway.

 

Yep. I did the same with some 14ga speaker wire.