One of my rear car speakers sounds distorted past a certain volume & all other speakers sound fine. Why does only one sound like that?

I drive a 2006 Honda Accord Coupe & one of my rear speakers is distorted past a certain volume while the other speakers sound fine. It almost sounds like some of the music is "missing" from that one speaker. I already swapped speakers & it still is coming from that same side so I know it's not the speakers. I previously tried to install an amp to power my speakers in May 2018 & when I turned the radio up not even half way, I heard a loud pop. I don't have that amp anymore because it ended up getting blown itself that same day. Could it be the factory wiring? I'm really pissed at myself for buying that stupid amp & causing this.

Bad wiring

Wvrsturw

The speaker is fried. Replace it.

The one is blown and needs to be replaced.

It could be that speaker's wire is shorted or loose from the speaker's terminals. Check that. There also is the possibility that that one channel is damaged.

Here are the things I recommend.

1 - Use oxygen free copper (OFC) speaker wires.

2 - Get a high quality 20-20k Hz 4 channel amplifier. I'd recommend Rockford Fosgate.

3 - For this test, you need a DMM. I'd recommend an SMD AMM-1 but a DMM is fine. If the speakers are being powered by the head unit, check it with the DMM. Set the DMM to AC. Plug the DMM to the speaker terminals. Negative on negative and positive on positive. You're gonna need to play a stable 40hz for this test. Do NOT change the volume on the head unit. Now do the second test on a non-distorted speaker the same way. Whatever it reads on the DMM should read the same on the second test. If they read differently, that channel is defective on the distorted speaker.