Couple of weeks ago out of nowhere my sound became really low and crappy. Checked around and find that only my rear speakers are on, no subwoofer or front speakers at all are working. Since I've bought the car, whenever I set the parking brake the sound lowers to very low, poor quality volume. Don't know if that's standard on all models but that's what my radio/ CD sound like now all the time. First question is: is the parking brake supposed to lower the sound? Second: anyone out there ever have this problem & what's the solution?