Hello!

my 2001 XJR (premium alpine sound) developed a bizarre issue: I have a high pitch noise coming from the subwoofer, even when the stereo is completely off. The subwoofer is working fine. Would appreciate any ideas on how to fix it or how to disconnect the subwoofer completely, as it’s quite annoying.

thank you!

 

I believe you are telling us you still have the stock sub working in your car? If so, you have a unicorn my friend. These notoriously deteriorate and the cone collapses. Its a bit of a fight, but you can get it out and you'll probably find its not in quality condition. Caution, it will be brittle coming out....mine disintegrated like a cheap dinner plate.

You may be able to find someone to rebuild it (if you can't yourself from say YouTube), if you feel so inclined. Most seem to go with a sub box. Keep in mind, your dealing with 21+ yr old tech, which back then was probably 20+ yrs old tech. The coil could be on its way out or the whole unit may have collapsed?

 

Does the pitch alternate with engine rpm ?

 

yes, i think so

 

Then it might be amplifier or headunit grounding issue or just broken amplifier. Alternator high pitch squeal from the speakers is classic grounding issue especially when installing aftermarket hu & amplifier and grounding is not done propely. Sometimes it squeals even with good grounds. There is just earth potential difference between ground points and amplifier picks it up.

 

thanks, no noise from other speakers. Any guidance how to approach the fix would be much appreciated 👍🙏🏼

 

I would first check the amplifier ground point for corrosion. If that is okay by througly unbolting and cleaning, then I would sent the amplifier to someone who fixes amplifiers who can test it. He may also confirm my guess by listening the noise in the car.