Right Speaker Bank Barely Functioning

[xpiramental]

I recently installed a subwoofer onto my premium audio system in my 2006 Titan. I used a line-out converter on the right and left rear speakers. Everything works great with the sub, but the right speakers are very quiet. I tried adjusting the balance through the head unit, with no alleviation of the problem. Then I removed the line-out converter from the right rear side, again no success. Anyone have an ideas as to what is making this problem?

[nvs008]

I'm not sure but i think those LOC's have little adjustments controls on one side of them.