alright, im installing some jbl 6.5"s and eclipse 4"s in my 91 Rx7. i have a sony HU (4x50w)/cd changer. now the problem is when i went to hook up the speakers all but the back right speaker are really really quiet. and i mean quiet you have to turn it all the way up just to be able to hear a little. now the back right works fine. its run through the stock wiring. i tried hooking the back left, which is also stock wiring but its really quiet also. now i thought it was the stock amps interfering but i spliced the wire right after the harness and hooked it up to see if itd work and it was still really quiet. if anyone has the answer to this one let me know cause id love to fix this

 

The sensitivity on the speakers could be mismatched.... this would make one set of speakers louder than the other. Check the specs on both sets of speakers. If you want to check it out the hard way hook up on of the front speakers in the back and see if you can hear a difference.

 

If in doubt always rewire.....run wire to each speaker and bypass factory ones. If you still have a problem after that, then its your radio...