How to deal with shared negative speaker wire

[mc625569]

Hello, I just got 89 325i with a broken aftermarket head unit and what looks like replacement 2 ways in the back panels.

Im trying to install an inexpensive head unit and some inexpensive speakers in the back.

Head unit wiring is hacked up but based of current aftermarket harness, there are no wires attached to -‘s for both rear speakers. I also don’t see any factory negative wires for the rears so I assume I have shared negative wires.

Can I wire in new head unit without using the - for the two rear speakers , as it was done before me , or will this cause problems.

Not looking for anything fancy just want speakers to work and a head unit that works.

I’d love to rewire correctly but I don’t want to spend the time right now , if and when I have a little cash I'll get an amp I’ll do things correctly.




Sent from my iPhone using Tapatalk

[Cephas]

My understanding is that no, you cannot run it that way. It's likely to burn out the new head-unit, or worse...could cause a fire if you melt the internal amplifier.

Run new speaker wires at the very least. Did your car come with a stock amplifier? If it did, there's a great tutorial on how to use those wires (at least for the rear speakers as they were twisted pair from the stock amplifier to the speaker locations) to power the rear speakers. You may have to run new wire for the fronts, which will be cheap and take very little time.


Edit: Here's the thread:

https://www.r3vlimited.com/board/showthread.php?t=191119

[mc625569]

How to deal with shared negative speaker wire

I just got the car with an after market head unit , I see no evidence of an amplifier in this car. I’m having trouble making sense of any of the amp workaround threads.

The head unit it came with was wired to just omit negatives that were shared , which seemed odd to me - it worked but it was the first issue im addressing.

I traced the wires back into the dash and found the point where all he negatives converge so If I split the wires there I can give everything it’s appropriate negative.

I’m going to stick with that for now. If I end up changing seats I’ll rewire.

Thanks.



Sent from my iPhone using Tapatalk

[Cephas]

I just got the car with an after market head unit , I see no evidence of an amplifier in this car. I’m having trouble making sense of any of the amp workaround threads.

The head unit it came with was wired to just omit negatives that were shared , which seemed odd to me - it worked but it was the first issue im addressing.

I traced the wires back into the dash and found the point where all he negatives converge so If I split the wires there I can give everything it’s appropriate negative.

I’m going to stick with that for now. If I end up changing seats I’ll rewire.

Thanks.



Sent from my iPhone using Tapatalk

I see what you're saying. Yes, if those negatives are all split to each individual speaker, that should work. The only issue would be that if you have a factory amplifier, then you're going to be feeding 10 watts into the line level input and then effectively amplifying that signal through the factory amp. Probably going to sound pretty bad.

Do you have tweeters in the "sail panel" on the door?

[reelizmpro]

Do you have premium sound or base model? If you have a base stereo in your 325i then I would just run new wires. It's not hard. If you have premium sound, then bypass the amp in the trunk and reuse the stock wiring.