I couldn't find a quick answer by searching threads and reading the service manual, so here's my problem:

Had a CD playing (non bose system), bass set at +3, volume around 12, the bass in the rear two speakers cut out at the same time. Front speakers are fine, same sound as usual, but both the rear speakers only play treble and a small amount of bass, but nowhere near the "booming" bass (as booming as the stock system can be) that's typical. Problem occurs for both radio and cd.

With the fade set all the way to rear the speakers don't sound garbled or distorted like the cone is torn, they just lack the full bass the front speakers have.

 

I think its supposed to be like that. the rear speakers are just there to fill space etc.

 

It sounded good since I bought it, then suddenly changed while I was driving it, so I don't think it's supposed to be like that.