40hz is just the two subs having cancellation due to placement. The delay settings work best for the rest of the frequencies though. The SVS subs I tried previously in the exact same position exhibited the same cancellation. I run a HPF set to about 15hz. The roll off is just how the EQ ended up being. I would have to cut more from 20hz and up as the natural frequency response of the drivers/box is heavily weighted towards 30hz and up (I’m cutting 10-15 dB in that range already just to get the curve you’re seeing without Dynamic EQ enabled). All of this is with a NX6000d.I would employ a steeper house curve, perhaps 10DB, and see how that goes. I don't use DEQ so I can't speak on it. It does seem that you begin to roll-off at 20Hz, are you running a hpf? Are you using a minidsp 2x4 HD? Seems like you have something funky going on around 40Hz.
I’m not sure how to get a steeper house curve as I’d have to do even more significant cuts to 30hz and above than what I’m already doing. These drivers are just so naturally weighted towards the midbass and don’t produce a flatter natural response like a UM-18 would.