I am considering the options for replacing the Comand 2.0 unit in my 2003 CLK55.

My understanding is that replacing the current setup is complicated by the following:
- The car runs an optical D2B network connecting CD changer, amplifier, telephone and head unit (possibly TV too)
- The head unit sends audio signals to the amplifier via the D2B bus (this is different from earlier Bose setups, which appear to have sent audio signal to the amplifier via a speaker level link)
- The amplifier requires a D2B head unit to turn on and operate
- The speakers are rated at a range of different impedance levels, with the most common being 2 ohms. These could work with a new amplifier in some cases (door speakers) but not in others (the sub)
- It is extremely unlikely that I will be able to find a head unit that will comfortably drive the 2 ohm speakers

All of the above means that the only option I really have is to replace everything. My preference is to fit a new Android head unit to power new, relatively low rated speakers in the door locations and remove everything else. I'm not an audiophile by any stretch of the imagination, but I do need decent navigation and Bluetooth.

A question or two:
- Am I correct on the detail of all of the above?
- Is there any reusable wiring in the car that could help? From pin outs, I can see that Comand 2.0 has pins for audio but it is not clear to me whether they are used for anything. When I pull the head unit, will I find an ISO connection for the speakers and if so, will it go anywhere? If I had speaker wiring running to the amp I could bypass the amp and it would make things much easier.
- Would a cheap 4 channel amp fed by RCAs and powering the factory speakers sound better or worse than a new head unit driving just new but low power speakers? Again, my preference is for a simple install.

 

Update: I went ahead and removed the Bose speakers and amplifier when I installed the new Android head unit. Everything in the first post was correct.

Lessons:
- The stock wiring from the trunk is not useful for an install as simple as mine. You would need to route audio to the trunk and that would be quite a lot of work. Good quality speaker wire from the head unit direct to the speakers is the way to go.
- In a Bose system, front door mids are 16.5cm and rear are 15.5cm. There is a lot of misinformation on that point with lots of people saying both are 6.5”.
- Obviously, a 6 speaker (mid, tweet, coax) system with no amplifier is not going to be as deep or as loud as an amplified 8 speaker system (+centre and sub). I am happy with that for the simplicity, cost and loss of weight.
- On weight, I was able to remove a lot. Old centre and sub, amplifier, cd changer, phone kit and adapter, tv tuner.
- Make sure you get high sensitivity, low RMS speakers that can be driven by the onboard amp.
- For the install I made sure that I had enough speaker wire to upgrade to a compact in-dash amplifier like the Pioneer GM-D1004 later if I wanted. I will skip this step but worth giving yourself the option if you are unsure, it would work fine with lower rated speakers .

Overall very happy with the result.

 

See above