Oem amp replacement e36

[iceman2007]

Hello all,
I have a 92 325is and factory amp is Blaupunkt with two 12 pin plugs (white - in from the HU and black to the speakers). I’m assuming white plug would have standard power, remote and ground plus 4 channels from HU (I have Alpine 163bt). Looking at this from the logical side black 12 pin plug only has 12 wires but my car has a total of 8 speakers counting by positive and negative wire connections to the speakers (I know rears have mid range and tweeters on each side but there is only one set of wires in each side. Counting plus and minus speaker level wires comes to 16 so there are obviously some common ground wires somewhere. Would you know if there are additional ground wires in the loop from black 12 pin plug and where I could find them? I would like to do a clean amp replacement without common grounds and have my Soundstream (4 channel) work with clean connections? I can not find any info on early e36 but I’ve managed to find e34 post that talked about common grounds being buried about 18 inches from the black plug which can be accessed to create a full 16 wires loom coming out of replacement amp (oem amp to be completely eliminated)
Any help would be greatly appreciated!


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[MarcoZandrini]

You likely have external (to the amp) crossovers. So the amp sends a full range signal to the LF door and the crossover “splits” the signal into 2 or 3 signals.