In my room, there is 35-40Hz suckout deal to bass cancellation at midline of the room. This is not present at 4 ft from the rear wall or 11 ft from the rearwall. Have you moved the seat backward and forward and remeasure? Is this present when you move the mic one to two feet off midline? How many db is it?
Sub may work too but better off minimizing the problem before adding the subs.
Sub may work too but better off minimizing the problem before adding the subs.