E36 With New Head Unit Has Low Volume in Rear Speakers

[Hoogineer]

Bimmer Audio Enthusiasts,

I've been searching these forums for information for the last couple of weeks as I prepared to replace the factory head unit in my car. Now that I have performed the operation, I have a working radio and CD player, but the rear volume is *much* lower than the front volume. I have to fade -8 to the rear (on a scale of -10 to +10) to get equivalent volume, which prevents the volume from getting as loud as I'd like. Can anyone explain why this is happening and what I need to do to fix it? A friend (non-BMW owner) thought that I might be able to up the "volume" on the rear amp so that it is brought in line with the head unit's amp.

A few details are in order...

Car: 1996 328is (E36)
System: Factory (HK premium option)
Amp: Factory (whatever came with the HK upgrade)
Head Unit: Sony CDX-S2000 (4 x 52w)
Head Unit Webpage (w/ manual & install instructions): esupport.sony.com/perl/model-documents.pl?mdl=CDXS2000
Harness Adapter: Metra 70-8591
Antenna Adapter: Metra 40-vw10
Metra Site: metraonline.com

The Metra harness adapter connected very easily to the factory connector and so did the antenna adapter. The Metra connector provided me with the following connections:
- Red/Yellow/Black for 12V Acc, 12V Mem, Ground (Check)
- Blue for Power Antenna (Didn't Use)
- Blue/White for Amp Turn-On (Not sure I have this connected properly)
- 4 x RCA plugs (Gray/White/Violet/Green ) for Front/Back L/R Speakers

The Head Unit's connector provides a plethora of wires:
- Amp Rem (connected [possibly badly] to the Blue/White Amp Turn-On)
- Ant Rem (Unused)
- Red/Yellow/Black for same as above (connected)
- 4 pairs (+/-) of wires for Front/Back L/R Speakers (only front L/R connected to jerr-rigged Y-adapter)
- *PLUS* L/R rear-audio RCA jacks for amplified rear audio on the head unit (check)

I elected to preserve all 4 RCA plugs from the Metra harness (in case I were to ever upgrade to a head unit that takes all 4 RCA plugs). So I bought a Y adapter with 2 female mono jacks, cut off the plug on the end, and spliced those wires to the front-speaker wires going into the head unit. I then connected the 2 rear plugs to the amplified rear audio jacks on the back of the head unit. The front speakers sound great, the rear speakers sound nearly inaudible.

I think the Amp Rem might not be connected properly due to a poor crimping job, but it does look look like the wires should be connected properly. It's really the only thing I have to check. Alternatively, I can abandon using the factory amp in the trunk and instead jerry-rig wire the rear L/R channels to the Metra adapter's RCA jacks in the same way I did already.

I apologize for the long post, but I hope the details are helpful. Thanks in advance.

[wiseleo]

OK I might as well answer this.

Sounds like a wrong harness, to be honest. There should be no cutting or y-adapters, only splicing.

What you did is:

1. Correctly connect remote amp wire - you'd have no sound otherwise
2. Incorrectly connect rear audio to UNAMPLIFIED pre-out connections on the back of your headunit. Pre-out means output at line level to be amplified by an external amplifier.

Solution. Connect speaker level wires (gray/violet/green/white) to appropriate wires on the harness. Ignore the RCA outs on your headunit until you get an aftermarket amplifier. I am sure it can be made to work, but I see no reason to bother.

Here is what the correct METRA BMW harness looks like:

http://www.installer.com/item/displa...php?it=70-8590 - no RCAs

http://www.installer.com/item/displa...php?it=70-8591 - and this is what you bought. A better explanation - http://www.mobilevideoauthority.com/...72/4766724.htm

I have the 70-8590 harness in my car. When I go to my full aftermarket setup, I was going to ignore the factory wiring. It sounds like your harness may allow me to avoid running RCAs to the back... Hmmm... that sounds like potentially less work!

Short version - buy the 70-8590 harness instead of the 70-8591

[mcquarrie]

Hi, I am about to install an new HU into a similar car; E36 with HK premium sound. I have the same adapter (70-8951) because all my research said it was the right one. What was the final solution to your problem?

[Sherwin@activeautowerke]

Wiselo, basically summed it up. In the OP's case the rear speakers were connected to a low level line output. If you use the proper adapter you shouldn't have a problem with this.

[Artofkicking]

I'm surprised no one mentioned that the "factory amp" could be the problem here.

1: New Radio (most likely GOOD)
2: His plug does work the front speakers (as designed to) yet the rear set do not play as designed.

It could be a wiring issue, but do this. temporarily connect the front speaker wires to the rear. If still low volume...bad amp.