One speaker is louder than the other

I have checked the other parts of my system, the problem is within 1 speaker. no buzzing. I am running them with a celestion sub with it own amp from 40 hz and below so the Speaker is ruuning essenitially full range.

just to clarify. I also have a pair of Celestion Sl600, which are essentially the same as a sl6si. when I run the SL600 with everything being the same, images are dead center, volume is 50/50. When I put the Sl6si in, the left side is louder than the right side.

I think I have found the problem. the surrounds on both speakers are cracking and is worse on the right side. Plan to get them repaired this week.