Originally Posted by
naiku
In my experience, using those door speakers near the B pillar, located low in the door, is not that good for rear fill. They're too close to the front, in order to have them not interfere with the front stage they're (again, this was in my car) dialed back so much it's not worth it. Moving them back to the sides of the trunk, between C and D pillars made them much more effective.
In my new vehicle I'm hoping to figure out a way to mount rear speakers in the D pillar, otherwise I'll just skip running rear fill.