I started out dreaming of 140 plus dB. And able to hit 15hz over 110 dB but starting to think with this null its not going to matter. I run my system hot. Like damn close to reference when I watch movies. Its not like I dont know what it takes to hit those levels. I have been building audio systems for over 20 years. But this null is so bad it just kills me.
Well, I have been designing and building audio systems for over 70 years and AV systems for 20 years.
You can not Eq those subs via audyssey.
What you have to do, and it not optional is: -
1). Accurately measure the subs, with a reliable measurement program and find the F3 point
2). Apply 12 db per octave boost below your measured F3.
3). Now you have to add a steep high pass filter at the point where driver reaches x-max. Needs to be 24 db. per octave.
I have the strongest of suspicions your problems are largely, if not entirely due to design and implementation of those subs you have.
If you can't do that, then get rid of those subs as they may well be doing more haram than good. Then you can DIY some good sealed subs, and instal them. I think this will give a high chance of success. I am certainly prepared to assist with the design of those ported subs
Your current approach will not get you where I think you want to be.