Does anyone know if the OEM system (non-Bose) uses an external amp or are the speakers running directly from the power of the head unit?

I ask this question because the rear speakers are not producing any sound at all. If the system does not employ an external amp, I would be lead to believe the rear channel on the head unit is shot (the chance of both speakers blowing at the same time is unlikely), but I'll pull the speakers and test them to make sure they work. If the rear channel on the head unit is bad, then I can simply replace it with an aftermarket unit.

Also, would anyone also know what the impedence is on the OEM speakers?

Feedback would be greatly appreciated.

Thanks in advance!!!

 

http://lmgtfy.com/?q=audi+symphony+II+amp+location

The A4 & 6 would use the same setup.