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Stock Amplifier Wire Harness Diagram

6K views 5 replies 4 participants last post by  meinpanzer 
#1 ·
Does anyone know which wire is which on the amplifier harness in the trunk of a 1991 300D? All I need to do is find which wires are the speaker signal inputs (not amplified outputs), so that I can tap into them for a subwoofer installation. There are about 10 different wires on this harness, and I thought I would get some expert advice before I go hacking into a 12V power wire.
 
#4 ·
This is from a 1992 system, but I think the pin-out/color code from the factory subwoofer amplifier is the same for your 1991.

Note that the factory sub amp simply samples the speaker outputs from the head unit, runs them through a low pass filter and equalization circuit to drive a bridged amplifier for the door speakers. The down side to this is there is no high pass on the main audio amps so they go into clipping prematurely. However, with good quality speakers (e.g., something like Jehnerts I use) the OEM unit packs quite a nice little punch and can sound pretty good.

If I might make some connection suggestions (assuming you are using the OEM head unit):

If you have a self powered sub that needs power, run a separate fused +12v lead to the battery area. The MB power wiring to the OEM sub amp is seriously lame. You can use the black (pin 7) control lead on the OEM amp to turn the sub on/off.

If you have a self powered sub with a built-in EQ, just connect to the audio out from head unit (grey-grey/brown; brown-brown/red).

If you have a self power sub with no EQ, or a passive sub with dual voice coils, or a passive sub with two separate drivers, use the sub-outs from the OEM sub amp (pins 1,2;11,12).

I would not recommend using a single voice coil passive sub with the OEM amp.

Hope this helps,

- FD
 

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