One of my speakers sounds louder then the other.

I would clean all of your connections; speaker cables, IC's. Tighten the screws on all the drivers so that they're snug and evenly torqued.

Is your room symmetrical? Try swapping sides with the speakers.

Just swap speakers and see if the problem moves with the speaker, if it does then you will know that the speaker is the problem.

Begin reversing interconnects and speaker cables to isolate the problem.

It may not be the speaker.

Okay, the obvious.......did you check the balance control?

Also check the position of the speakers in the room as well as differences in reflective surfaces/distances between left and right.

Asymmetrical configurations can cause one speaker to appear louder than the other even if they are actually the same volume.