By the way, autoboy, your tests of the bass drivers were fine; you'd only hear a scraping sound if the driver was killed when you pushed the driver in and out with equal pressure around the cone (the scraping sound results from a warped voice coil that's been fused or melted by the DC current from clipping and its travel is no longer linear).
The annoying thing about a bass null is that you can't use EQ to boost it or fix it -- to supply bass in the hole where there is none. If you had a bass peak, you could use EQ to reduce the peak in that listening seat. If everything else checks out--and it seems like it does--then moving the couch is the only solution.
Can you not move the couch back farther to an area where there's good bass?
Axiom Resident Expert