I listened to the front and rear bottom set of speakers. I also faded the sound from front to rear.
Update from dealership.
They removed the rear door panels and showed me the "dummy" speakers and said that all ML's were like this. The speaker map another forum member posted indicates otherwise.
I just came back from the dealership and they removed the rear door panels and showed me the "dummy" speakers in the bottom set of speakers in the rear doors. They claim that this is how it is supposed to be and said that another Lux+ with ML also had the same setup. The speaker map shows that...