Making the distance between each speaker and your ears different will cause slight phase shift, particularly at higher frequencies, and unequal toe-in will also have an effect on phase. Changing the relative volume (using the balance control will not have a direct effect on phase relationships.
When adjusting speaker position, like you, I still try to make the speakers equidistant to my head. I have found that a cheap laser rangefinder I picked up at Home Depot to be really handy in this regard.
When adjusting speaker position, like you, I still try to make the speakers equidistant to my head. I have found that a cheap laser rangefinder I picked up at Home Depot to be really handy in this regard.