ECU interference on door speaker

Huw Powell audi at
Wed Dec 13 14:21:39 EST 2006

> I removed all the RCA cables from the amps and tried revving the
> engine, but the sound is still there, mostly on the right front door
> speaker.

So the sound is independent of the RCA wiring, is it RPM dependent?

> I know it's crazy, but I'm still suspecting that speaker
> wire near the ECU.

It won't be.  OK, unless that wire is actually *connected* to something 
other than the amplifier, like via some scraped insulation.

Try this... disconnect all the car speakers at the amp.  Run one speaker 
wire out of the car to another speaker, any speaker.  Turn on car, fire 
up and listen.

Just a quick thing that occurred to me but I dismissed since you are 
running your own amplifiers - those door speakers do not have built in 
amps, right?

Also make sure the speaker wire is not accidentally grounded anywhere 
along its path, especially in the door, at the speaker.

> It only comes over the tweeter which is probably
> more sensitive to interference. 

Nooooo, it's because the noise is mostly higher frequencies.

Also, the passenger door speaker is often the easiest one to hear when 
sitting in the driver seat.  I'll bet it's equally present on all four 

Keep trying the hints people have provided here to stop the noise from 
being picked up at the amp; also anything you can do to reduce the 
source will help.

If it is RPM dependent, it may be alternator noise, being broadcast 
through the alt to battery wire.  Brush condition?  Quality of all main 
power system grounds?  It may also be ignition noise - check quality of 
plug wires, cap/rotor/plugs, etc.

Huw Powell

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