With an SB16 Ultra tucked tight in the corner like that, I'm not sure there is any roll-off!
I suspect, if he is using RoomEQ, it is dialing back both subs very heavily!
Don't forget that the SB16 Ultra is one of only 6
(of 48 tested as of 7/21/19) subs that AH has tested which passed the CEA 2010 test for output at 10Hz!
Funk Audio 18.0 ($3234)
Outlaw Audio X-13 Ultra ($1499)
Paradigm Signature SUB 2 ($10500)
SVS SB13 Ultra ($1599)
Velodyne DD18+ ($4999)
Interesting that the ported X-13 (in the sealed configuration, of course) manages this, but no other ported sub (including several that are 15" or larger) does! I wonder what aspect of the X-13 design affords this!
But back to my point, corner loading a sub like the SB16 adds significant dB to the bass such that roll-off is minimal.
Actually I am surprised that the PB16 Ultra in the corner does not overwhelm the room with bass!
, what setting do you use for the PB16 Ultra and what other EQ/setup might you apply to those monsters (the PB16 and SB16)?