I have a 1985 Camaro project car that I basically rebuilt from the ground up including interior & engine. I have a JVC head unit & Alpine speakers (plus an amp and two 12" subs). From the get-go, I had no issues related to the audio, everything sounded great.
Recently (about 2 months ago), I found that I had a problem with my ignition coil. I swapped it out for a different model and right around the same time, I notice that when you drive the car with the radio off you hear a very faint "humming" or static noise coming through the speakers. It's pretty quiet, you can barely hear it at idle and low RPM but not at all at high RPM or when the radio is on. It's hard to pinpoint, but I think it's only coming from the passenger side dash speaker, not the driver side or either of the rears. This is sort of a guess, though.
I can't be sure, but I think the noise may be related to swapping out the coil? In my application, the coil is mounted on the firewall on the passenger side, so basically really close to the speaker I think I hear noise through. I'm not 100% positive that it started at the same time as I've been doing a lot of work & modification to the car but it seems to fit. Is there an easy way to tell if this is causing my issue? Or an easy way to fix/prevent?
Disconnect that speaker and I am betting you will still be hearing the noise.
It is possible the coil is inducing the noise. Disconnect the speaker wires for that speaker from their source. Whatever is powering that speaker, amp or radio. Connect a new set of wires and test speaker. Move wires and speaker towards old speaker wire routing/location and see if noise comes in when moved towards original circuit. You may only have to reroute wires. Use twisted wires if you need to replace as they reduce noise induction.
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sparky