High pitch noise doorspeakers (back) after retrofit subwoofer


Dutch Retrofitfanatic
Hi all,

I have a A3 with the Audi Chorus from factory, this ment that it only had 2 frontdoor speakers and tweeters in the A pillars.

I went to a car graveyard and bought myself a original Blaupunkt subwoofer and 2 reardoor speakers.
I connected them all and the sub in combination with the frontdoor speakers work fine.

The downside, when I connect the reardoor speakers to the subwoofer (the sub has a build in amp) the rearspeaker(s) give me a high pitch noise through it. Car is not running and even when I pull the keys out of it, it stops after a minute or 2/3.

I've layed the RCA cables on the right side of the car and the live feed and remote AMP on wire on the left side. There is a point in the trunk where the cables meet but that's a small part and couldn't cause that much interference I guess.

I've read about an earthloop? Could this be the case? I have grounded everything properly in my opinion on the car chassis. When I disconnect the rear speakers the subwoofer works very well..


Dutch Retrofitfanatic