Stereo speakers stopped working, wiring diagram needed

Hello, I'm Harry. Unfortunately, they do all get their signal from the same source. The radio itself. I suspect it has kicked the bucket. But here's that wiring diagram.

This does sometimes happen to radios when they get old. Mine has gotten a bit moody. Usually the rear speakers don't work at all. Sometimes the rear driver's one does. Sometimes only the driver's side speakers work. I've got a replacement ready to go in. Just need the time to actually do it.

I screenshotted the diagrams for you, but they're a little blurry. Let me know if you can't make heads from tails on them and I'll figure something else out.

From the description I would also say it's the unit itself. The factory wiring only has a single fuse for the audio. That is fuse 11. The 4 speakers then connected to the stereo itself.
With the aftermarket unit it will depend on how it was connected and if it uses a separate amplifier. For that the OE diagram isn't going to help. What you could do is look up the make and model of the head unit and see if they have wiring and troubleshooting info, or see if these are common issues with that unit.

Click or tap it and it should open up much larger.

Okay, maybe these diagrams will work better. But there are several of them with slight variations that are for different radios. Also, with it being aftermarket, they may all be useless because we don't know what else might have been done. Maybe there's an amplifier that needs to be checked out. Maybe they cut and spliced the wire harness and didn't do a terribly good job, resulting in loose wiring. Also, most likely there's a fuse on the back of the radio that needs to be checked. The only way to check it is to pull the radio out.

Hope this info helps.