May also be a bad computer and the subwoofer was just the first "symptom".
Three days after tacking delivery of mine I got all kinds of whack codes and the car wouldn't start. They had the car for over a week replacing misc pieces, finally replaced the ECU and car has run great since.
Who knows, the electronics with these cars makes me a bit nervous about the longevity of the car.
2011 Le Mans Blue M3// Black extended Novillo w/ Blue Grey Aluminum trim/DCT/ZTP/ZCW/ZPP/ZCP Premium Sound ///Akrapovic Evolution Exhaust
2015 Audi S4 Prestige, Brilliant Black S-tronic
2012 Le Mans Blue 135i M Pkg DCT