i work at circuit city and i can tell you that you have either a short in your lines somewhere, or your speakers are blown. if they've never worked, perhaps they're disconnected. if you are knowledgeable, replace the wiring doing from the stereo to the back speakers, but i would recommend taking it to a pro cuz it requires taking a lot of the car apart on the inside. hope this helps! also, try changing the fade/balance. it may be screwed
bose speakers
If the receiver is just stereo, not surround sound, you will not be able to create a surround sound (front, centre, sub, surround) setup.
plug in your speakers
Ideally, the system should have the same brand and model in the surround as the three front speakers .
5.25" front and rear sound bar
5.1 channel refers to a type of digital sound distribution. This type usually includes 5 speakers and a subwoofer. These would include a center speaker, two side speakers, and two back speakers. There are also 6.1 7.1 and 8.1 sound distribution which just include more speakers in the mix.
It depends on the surround sound system used. The common surround system used is call 5.1 and consists of five speakers: Three in front and two on each sides.
as the sound comes out of the speakers its an output
If you have the Bose sound system crutchfield.com says the front speakers are 6 1/2" and rear doors are 5 1/4"
After spending a couple of hours on this, I found the answer 10 minutes after posting the question... The problem was that the "A" and "B" speaker selections control the front speakers only. The surround sound speakers are always on, regardless of which set of speakers is selected. The answer to the problem was to set the receiver in "direct stereo" mode so that the surrouund sound stuff was taken out of the loop.
From what I can tell the front door speakers are 6x9". The rear speakers are 5.25" (round). The dash speakers are 2". What's not clear is if the Infinity system is 2 ohm or 4 ohm. But installing 4 ohm speakers should not cause any damage, just less sound sue to higher impedance.
Take it to a Nissan Leader. They are the only ones that can fix or replace Bose sound systems and speakers. Or try ebay..