This is a not-so-fun problem I'm having:

I was getting serious alternator whine, which I thought I'd traced back to the HU RCA grounds (which might still be a significant problem). However, today, while driving around and the HU being repaired (ie: not in the car), I noticed my tweeters were still making noise! And not just some random pink noise, but WHINE as well! I just about blew up. I checked and the amps were not on, so I have no clue where this is coming from.

I took it to Methodman and he couldn't believe it. I'm still at a loss. Here's what he recommended I try:

- switch the tweets and mids on the x-over to see if the problem follows the signal
- unhook the speaker wires from the amp and listen

For reference: I'm using 12 gauge Audison Connection speaker wire and none of the electronics going to the doors was getting a signal. Also, on the BMW, the mids are in the kicks and the tweets are in the doors.

Any ideas?

 

Found it! Turns out I placed the crossovers next to the main chassis grounds for the instruments and ECU (d'oh!). So much for good wiring. If I take the crossovers and move them out of the dash, the noise stops completely.

Now for the new problem.

I moved the crossovers all over under the dash (within my wire-slack distance) and there is interference EVERYWHERE, even more-so than right under the ground. I can't put them in the doors without adding another loom between the door and the interior. Anyone have any suggestions?

 

get some more speaker wire and put them in trunk

 

you got to get those crossovers outta there even if it means extra wire length.

 

Get them under the seat, in the trunk, or you could try wrapping them in aluminum foil that you then may have to ground.

 

I was actually about to ask about aluminum foil. I really don't want them so far from the speakers as to put them in the trunk, and, by the magic of BMW, it's amazingly hard to get the seats out without triggering the mechanical tensioner, so I'd rather not try

 

It's worth a try since it doesn't really cost anything but time.

 

After a little playing around, it looks like, on top of the crossovers, my RCA's are giving some of the whine. The list grows :P

 

OK
Try the aluminum foil trick as this appears to be radiated noise. Try the foil ungrounded and grounded.

Why does aftermarket equipment give you noise issues and not factory setup?

Shielded (coaxial) RCA’s.... OR braided RCA’s could help. Sometimes shielded RCA's perform poorer in EMI situations, braided should RCA's work well in most situations.

You need to identify if there is a root cause to your issue, was maintenance performed on your car recently (or could you have caused it working on your stereo) and could it have done SOMETHING weird. Remember this is weird so it doesn’t have to make sense yet, once you solve it then you will go “OK now it all makes sense”. BMW may have done things to cure this noise at the factory and you could have un-done it

 

Heh well I'm pretty sure I've undid about everything. The foil approach did not work, unfortunately, so the crossovers will either be moved under the padding in the passenger side footwell if there is room, or back to the trunk if need be. The RCA's are giving noise because I zip tied them to an existing wiring loom and through a grommett into the trunk, which just happens to have the fuel pump power wire in it. So it's grabbing the EMI from being strapped to that wire for a good 6 feet, which isn't so surprising. They're Audison Connection RCA's so they're good quality.

The re-wiring is delayed a bit until some parts come from the US (new brake light sensor switch, new cabin air filter) that need the dash to be taken apart to replace, so I'll do it all at once. Updates as I get them!