|
if you imagine your car bluetooth input as a bluetooth headset, it would not be desirable to make the volume 100% when using a bluetooth headset, with no way to adjust it. The phone treats the car connection in the same way.
I admit it would be better if it did it the other way, I have a radio at home that can stream BT audio from your phone and in that case, it takes over volume control completely and when you change the volume on the radio it adjusts the volume on the phone, but this is not the way BMW have implemented it.
Via USB, the audio is sent I presume at line level, and then it is amplified by the head unit, and in this case, when you change the car volume, it's adjusting the volume of the head unit itself, not the level of the phone that's feeding it.
|