I've never quite figured out why panning can cause issues with mixes translating, but it certainly has for me over the years. I'm talking about a center panned vocal being at an obviously different level on my studio monitors than in my car stereo. To complicate matters even worse, I've had the same problem with wide panned instruments. Sometimes it appears as if the guitars almost dissappear.

I guess this could be some sort of phase issue. Maybe I need to check my mixes in mono before they leave the door.

Brandon