I have a 2004 CL500 with (according to a VIN decode) "comand DVD APS with navigation", CD changer, and analogue TV (no longer of use in Australia). I've replaced the 4 door speakers (the flexible stuff between cardboard cone and frame had disintegrated) and now it works tolerably well. But... there's a large speaker in the rear shelf, in good condition so far as I can tell, which makes no sound. The speakers that I replaced were stamped "Mercedes" and sit in mounts badged Nokia. The comand does not come up with the Sound soft key.
So the questions are what have I got, and what is supposed to drive that rear speaker?

 

It seems that when the fader display shows everything centred it's barely sending anything to the back at all. However, shift the fader to near total rear bias and magically it sounds a lot better, while still producing sound from the front speakers, etc.