Maybe I've been watching Blues Clues with my 3-1/2 year old daughter too much, but once I finally got to see one of these new fangled DSP systems in person, a coupla (sic) things led to the fact that the system is a lot simpler than we all thought. Ya gotta just love German logic!
As it turns out, the DSP "radio" is exactly the same radio that is in the non DSP system! So, all the same functions and connections are present to do the same amp and speaker upgrades as the DSP cars. This is good news for those of you who are looking to upgrade. Here is how it works:
1. The present DSP system has the controls up front, which appears to be irrelevant to the discusson (at least in the car I saw with Nav.)
2. The front conrols operate a separate "radio" chassis, the Nav, the CD player etc. through the communication bus. The radio itself is a small box about 2 x 7 x 5 with the same connector that BMW uses for it's in dash radios in one corner. Present on this connector are the left and right audio signals from the radio. These are only two channels, containing only radio and cassette signals, and they are unaffected by any of the volume, balance, or tone controls. They happen to be in the same pin locations as the Left front and right front connections on the in-dash BMW radios from E36 and E34 models. (Clue #1) Below this connector are two smaller rectangular connectors which will soon play a part in the solution.
3.The CD changer has a power and digital bus connection. There is a digital connection from the CD changer to the box which contains the DSP plus amplifier. There is a rectangular connection which is unused, and matches the unused connector on the radio. (Clue #2)
4.Finally, investigation of the radio showed that the PCB was fully stuffed, (no missing parts) and the PCB around the large connector showed designations for LR and RR signals. (Clue #3)
As in Blue's Clues, we now know pretty much all the important facts.
It became apparent that the only difference between the DSP electronic hardware was the addition of the DSP "box" itself, and a different wiring harness! And, oh yeah, that laughable "subwoofer".
Then the final test: disconnect the DSP box, fire up the system and, Voila! The DSP selection dissappears from the menu, and Bass Treble Balance and Fader appear. The darn thing is Plug and Play! When you don't have the DSP on the bus, the radio output starts to work like the standard system, and its basic functions return to the analog outputs. The two things which remain are to get the signal from the CD changer to the radio, and to get to the rear channel connections of the radio output. The first involves buying the short wiring harness used for this purpose in the non-DSP systems. This is a standard BMW part. The second involves buying four of the connector sockets which mate with the radio connectors and inserting them into the open holes of the plastic plug which goes to the radio. They go into the same positions used for rear speakers on he conventional radio. Then just take the DSP box and post it on E-bay, or save it for the end of the lease.
Unfortunately, I do not know part numbers for the BMW cable and the connectors, but you sould be able to get them from your BMW parts dept. Since Rich was nice enough to let me share the broad knowledge, I respect his desire to keep the finer details of these findings from his immediate market area competition by not posting pin locations and part numbers. However, there should be enough information in this post so that those of you who are knowledgeable enough that you should be attempting to do this yourself in the first place will be able to take it from here. Or, if you're in New England, drop your car off at Rich's Car Tunes and have them do the job. If you're not in the Boston area, give Rich a call and ask him to put a kit together with the parts you need and instructions. Of course, your local installer should be able to figure it out from this post as well. If they can't, DONT LEAVE YOUR CAR WITH THEM!
Disclaimer: I have no connection to Rich's other than to acknowledge that since they were a key player in figuring this mystery out they deserve some gratitude, or is that "gratuity" ;-).