Just checked mine. That knob seems to only be for reading the menu and entering your preferences. Bass is adjusted by pushing info beside the other knob to Bass and then adjust with the same knob.
Thanks for the info, you're correct and I got my bass down! I do have issues with the volume knob not always working, where I'll turn it 2 full rotations to get the music to go from 15 to 10. I've just used the steering wheel controls for that, so perhaps it was just having a touchy moment when I initially tried to lower the bass..Just checked mine. That knob seems to only be for reading the menu and entering your preferences. Bass is adjusted by pushing info beside the other knob to Bass and then adjust with the same knob.