Almost no output on middle and rear speakers

[ree]

Ever since my last visit to the dealer for warantee work, I've been bugged by what seems like too much bias to the front speakers in my 2003 H2 (CD/Tape/Radio head unit). I've had to run the fade control more that 2/3toward the back to make it sound balanced to me (2/3 of way from middle on radio display to the left, i.e. way back).

I finally climbed in the rear seats and listened with fade set to zero today and it's clear that 90-95% of the sounds is coming out the front speakers. You can tell the other speakers are getting signal by leaning in close to them, but you've got to get really close to tell for sure. Clearly not normal.

What could cause this? They upgraded my radio firmware during the last visit in an attempt to fix the auto volume feature.

Could something have gotten hooked back up wrong? Or is there a calibration that needs to be done? Or could the software be buggy?

I'd just drop it at the dealer to have it looked at except I don't live near one and don't have a trek to the big city planned just yet.