Pre 1993 4 channel amp wiring diagram

[dragon850]

Thinking about upgrading factory 4 channel amp to an aftermarket amp with built in crossovers, don't really want to cut into the OEM harness.
I remember someone tapped into the existing harness and connected a small powerful 4 channel amp, can't find that post...Looking to do the same, does anyone have the schematic for that?

[cartoonz]

yeah, *somebody* knows how to do that

[dragon850]

yeah, *somebody* knows how to do that

Hahaha, of course... I will call you today.

[m6bigdog]

E32 & E34 used the same 4-channel amp configuration; so searching other forums could yield results.
4-channel connector pin-out attached.

IMHO, there is no easy path forward upgrading a 4-channel amp audio system.

I thought about upgrading the 4-channel amp/crossover in my 1991, E34-M5.
The 4-channel amp/crossover chassis is easy to separate by removing the screws that hold the amp heat-sink which just plugs into the chassis/crossover PCB. The connectors/crossover/chassis are a unit ripe to attach a barrier strip for a new external amp.
Unfortunately, the Achilles heel of the factory 4-channel audio system is it uses a single ended amp design, the amp connector and wiring harness uses a common grounding scheme for the speakers on each channel and therefore you cannot use it as-is with a bridged-amp configuration, because grounds for each speaker must be isolated.

Fortunately, the speaker ground splices in the harness are close to the amp connector, so the wiring harness is usable for a bridged-amp but the factory 4-channel amp crossovers and connectors will need to be abandoned.
Since my M5 had a head-unit which was a generation prior to the 17-pin connector, I upgraded the head unit, complete audio system wiring harness w/Diversity antenna and installed the Harman Kardan Top-Hi Fi Audio system from E36-M3.

I deleted the connector Pin-Out image as it seemed to be different than the E31 ETM wiring harness

[Pneill316]

My issue when tackling that was they all had the same ground for each side

[e31gixxxer]

If you start from scratch you could remove about 10lb of redundant cable, although you may add a few with new amps and subs.