So without any further adieu, I hereby present, in one single location, all the basic information needed for the next fool that buys an E85 Z4 with a butchered audio system.
The BMW Business CD radio on the DSP system only provides Channel 1 (Front Left) and Channel 2 (Front Right) audio signals to the OEM amplifier where the signals are summed, and the processed audio signals are sent to each individual speaker, including the Carver subwoofers. The radio and DSP amp are connected by the K bus which is a digital signal specific to the vehicle's built-in systems.
What that means:
-You can’t use an aftermarket amp with the stock radio.
-You can’t use an aftermarket radio with the stock amp.
-You can’t use the Carver subwoofers without the stock amp.
-You can’t use the built-in bluetooth phone features without the stock radio.
-You’re gonna be so mad if you bought a Z4 with a non-functioning DSP system.
What you can do about it:
-You CAN install an aftermarket radio with an aftermarket amplifier using the stock wiring harness.
-You CAN replace the Carver subwoofers (that procedure is not covered here, but you can do it I believe in you. It may be worth it to just buy the standard woofers from the non-DSP system. They'll fit in the same place and they're just standard paper 2ohm woofers, like $50 on ebay)
-You CAN enjoy great sound from all ten speakers with most any aftermarket analog amp or DSP amp.
- Screenshot 2023-01-25 at 9.39.40 AM.png (1.88 KiB) Viewed 800 times
2 - Front Right Positive -- Blue w/Red
7 - Front Right Negative -- Brown w/Orange
3 - Front Left Positive -- Yellow w/Red
8 - Front Left Negative -- Brown w/Orange
12 - Ground wire -- Brown
13 - Amp Remote Power -- White
15 - 12v Power -- Red w/Yellow
16 - Radio Remote Power -- Violet w/White
(When wiring in power for the amp, the white #13 wire is your remote turn-on signal. You can find it in the factory amp wiring harness.)
You’ll be tempted to connect ALL the wires on your radio harness adapter but I assure you, you only need the 8 connections listed above. Since the OEM radio is connected to the K-Bus, signals from other wires won’t be interpreted by your aftermarket system and may cause numerous issues with system operation including but not limited to: Amp always on, dead battery now, panic because you thought you knew what you were doing, you idiot.
In my case, I had a 4 channel amp and if you paid attention up to this point, you understand that there are only 2 channels of audio coming from the OEM radio harness.
Because of that, I wanted to send full range frequencies to the tweeters and mid-range speakers and low range frequencies to the front woofers and rear subwoofers.
How I achieved this is by connecting the factory Ch1 and Ch2 wiring to the corresponding hi-level inputs on the amp and splicing channels 3 & 4 into Ch1 and Ch2. This way, the same signals are being fed to all four corresponding channels on the amp, but I used the low-pass filter just on Ch3 & Ch4. I wired speaker-out channels 1 & 2 to the six high and mid frequency speakers and I wired speaker-out channels 3 & 4 to the front and rear low frequency woofers.
This is where it can get a little overwhelming because of just how many wires there are on the amp harness. The guide above will tell you which wires to use for your amp inputs and the guide below will tell you which wires to use for your speaker outputs.
Speaker locations and wire colors:
LEFT SPEAKERS
- Tweeter Positive — Yellow w/Red
- Tweeter Negative — Yellow w/Brown
- Front Door Positive — Blue w/White
- Front Door Negative — Blue w/Brown
- Front Kick Woofer Positive — Red w/Yellow
- Front Kick Woofer Negative — Red w/Brown
- Rear Upper Positive — Yellow w/Black
- Rear Upper Negative — Yellow w/Brown
- Rear Lower (Subwoofer) Positive — Yellow
- Rear Lower (Subwoofer) Negative — Brown
RIGHT SPEAKERS
- Tweeter Positive — Blue w/Black
- Tweeter Negative — Blue w/Brown
- Front Door Positive — Blue w/Red
- Front Door Negative — Blue w/Brown
- Front Woofer Positive — Blue w/White
- Front Woofer Negative — Blue w/Brown
- Rear Upper Positive — White w/Black
- Rear Upper Negative — White w/Brown
- Rear Lower (Subwoofer) Positive — Blue
- Rear Lower (Subwoofer) Negative — Brown
This is all the info you need to have to successfully wire up an aftermarket radio with an aftermarket amp in your Top HiFi “Premium Audio” CarverTM BMW E85 Z4. Your mileage may vary, but everything you need should be listed above. Happy soldering!
