Ok, it's been a week since I replaced my '01 X5 4.4 with an '06. IMHO the '06 represents a significant improvement over the '01 except in one area... audio.

Both vehicles were equipped with NAV, premium sound (DSP) and CD changer, but the '01 sounded SO much better. Even my wife who doesn't usually care about these things commented on how "empty" the '06 sounded on the way back home from the dealership.

The '01 delivered MUCH better reproduction across the frequency range (esp. the highs and lows) than the '06 which sounds horrible when listening to the same CD's that I played for years in the '01 with the same DSP settings.

It sounds as if some frequencies are muted / missing. It also sounds as if the speakers in the rear doors have severe problems with lower frequencies at higher volumes or there's a bunch of loose stuff behind the door panel. The '01 had none of these problems - by comparison it sounded GREAT.

Has anybody else noticed the same?
Any ideas on how to improve this?

I'm taking it back tomorrow to have this looked at.
FWIW: the '01 had a 09/00 build date.

Thanks,
- Rob