I'm very happy with the quality of the Sennheiser system in my car, volume has to be up at Motorway speeds, but that's the same in most vehicles. Shame that change is manual, with the awkward positioning of the volume knob. It would be feasible to change volume from the connected phone / bluetooth controller, but MMC state that the phone input (volume) into the system should be high, and then (presumably) all sound is adjusted by the car volume controller.
On the one occasion the bluetooth module in the car failed to connect I was left with just the soundtrack of the engine and exhaust. I was not disappointed!
