ECU interference on door speaker

[Ameer Antar]

-------------------- Original Message --------------------
From:Huw Powell [audi at humanspeakers.com]
To:Ameer Antar [antar at comcast.net]
Cc:Quattro List [quattro at audifans.com], Scott Phillips [Scottp at ippe.com]
Date:12/13/06 2:21:39 PM
Subject:Re: ECU interference on door speaker
>So the sound is independent of the RCA wiring, is it RPM dependent?
Yes, it is.
 
>It won't be. OK, unless that wire is actually *connected* to something
>other than the amplifier, like via some scraped insulation.
 
I checked the speaker wire for shorts, but it looks fine.. it's good quality wire with thick insulation, and I used grommets and zip-ties everywhere.
I tried to ground the headunit to the battery using 12ga wire, but it made no difference. So I scrapped that. Then I decided to pull the speaker wire from around the ECU, but it still kept buzzing. You're right, it does seem to be coming from all the speakers, you just have to listen very close.
 
>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?
nope, everything is in the trunk.

>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.
After all the troubleshooting I'm thinking the noise is coming into the system by the power leads. The alternator could be the issue. It's an Ultranator I bought a while back, but it only has < 5000 miles on it, so brushes should be good. Ignition components are all stock and pretty new. The wires are Prenco brand wiht the loom. I don't know if they're noise suppressing.
 
So I'm wondering if there are any beefy noise filters for the power cables. The ones I've seen in the store are too small... they look like they're designed for head units. I'd like to put a filter on it at the main line, before the distribution blocks so the noise isn't even carried into the trunk, where it might be picked up by the audio cables. With 3 amps in there, I think I'd need a filter to handle 60-80A, right? Going by the fuse ratings on the amp, the total is 120A. Is there a way to homebrew something like that?
 
Thanks for all the advice.
 
-Ameer