The car had some major work done. On trip home all four door speakers quit playing. While driving, just turned off. Dash speakers play fine. Can hear the subs (really) sometimes.
Assumed a bad ground and cleaned the three behind radiator and then the four in the back of the trunk.ECU voltage is 13.8 with engine running.
Assume dash speakers are channels in the same amplifier as door speakers.
These are substitute speakers, been installed seven years. But were working fine.
Is a new amplifier in the near future?

 

Alpine audio system wiring is shown below. Front door mid speakers are on their own channels. The front door tweeter and dash speakers share the same (respective) channels. Rear door mids and tweeters are shared.

Very odd for all 4 to quit at once. You mentioned the speakers are replacements, the OE door speakers had issues with the wires detaching from the cone. Have you checked at the door with a test speaker to verify if they are the issue?

Grounds for the audio system are unrelated to underhood grounds. G25 (audio amp) is in the trunk next to CD changer.

 

Was going to say, common problem, then I saw that you said substitute speakers. By substitute, so you mean identical replacements, or something aftermarket? I also assume that substitute speakers means you don't have the door tweeters still in place? The classic failure of the factory door speakers leaves the tweeters playing, as well as the dash speakers and subs.

There is nothing in common with the wiring of the four door speakers except one connector, TL31, a 14-way connector located "below center console / RH side of transmission tunnel." Quoted, because that's how the electrical guide describes it. The dash speakers and subs do not go through that connector. There is no other point or connector common to all four speakers, as they all have their own connection to the amplifier, and since the dash and subs work, it's not a ground.

 

The speakers playing are dash, front door tweeters, and subs. The front door mids and rear door mid and tweeters are silent.
It may be electronic. Was adjusting volume when they quit playing. Volume indicator jumped around on screen, and then they went silent. The volume was sound 20, jumped to 30, back to 10, and then back to 20. Fast.
Sound is terrible with tweeters in door handle and dash only playing. Shrill.
Speakers are Audio Design. A good aftermarket brand. Tweeters in all four doors replaced with mids in 2015.

 

The volume display behavior you observed is very odd.
Almost seems like there was a communications issue cropped up between audio unit and amp that might have glitched.
I wonder if one or both of the units have managed to get into a partially confused locked state.

Might be worth trying pulling the respective fuses to the Amp and audio unit for a few minutes, as they like most things these days are just put into a standby state when the ignition is switched off.
Giving them a hard power off might allow the units to properly reinitialize themselves....worth a shot before you start down the changing hardware route.

 

There is no copper connection from the head unit to the amplifier, so all of that goes over the fiber, including the control commands like source selection, volume, etc. There might be a fiber issue.

The fuse-pulling is a good idea, but better yet, just disconnect the battery, both cables, touch the cables together, then reconnect. You'll have to re-train your auto-up windows (just hold each switch for 5 seconds or so after running them up closed,) but the battery disconnect is a good master reset for just about everything on the car.

 

Yes fibre is the comms linkage between radio and amp, so as such will likely either work or not. The fibre pathway shouldn't be selective as to which channels were working as it is a simple dumb piece of optical plastic passing encoded data back and forth.
Either there is an issue with the encoding coming from the radio unit omitting the door mid-range channels, the decoding within the amplifier not separating that channel information out, or the output stage of the amp unable to deliver the channels.
I assume there is no difference between input sources e.g. radio versus CDs playing.

Both doors at the same time and a user interface graphics anomaly doesn't sound like output stage to me....one channel yes but two at the same time ...unlikely.
Encoding or decoding issue is my suspicion and a system reboot is certainly the quickest, cheapest and best place to start......go for the low hanging fruit first!

 

For my own education: but how do you know that those 4 channels (door woofers in front and rear door speakers) died all at once?

A more like scenario is the aging amp has been losing 1 channel at a time for a while now, and only recently you have noticed that your doors are silent.

Finally, what is the impedance of the aftermarket speakers that you installed in 2015?

 

Ok, I have this same problem. I am going to try the hard reset with the battery first. I cannot say when they went out and there is a possibility that I disconnected something (as noted above) in the console RH. So, I will have to check that.

Any other suggestions because I already pulled the amplifier and was just going to replace it with one from eBay.

Thanks,
Brian