The Chesky test disk. Either using my DVD player with the digital optical output into the 950, against only the analog input into the 950. I detect no difference. In phase is in phase as described on the disk, and out of phase is out of phase as described on the disk. I never change the phase switch on the sub. db level on the RS meter are the same, etc.
I have also done more subjective comparisons with action disks (Tears of the Sun a most recent).
My HT room has a slab floor. So most all bass is conducted through the air.
I get lots of artillery shots falling in my lap, no problem. Digital or analog, they sound (feel) the same.
So either there is something wrong in my test setup or technique, or not all 950's are created equal.