It's not taking long to find that out! My pressure traps aren't making a dent that low, at least not in the front corners where convention says to place them. I'm anxious to track down the problem(s) and fix it(them) to get better bass.20-35 you're not going to do much with treatment. Above that it's got to be THICK like our Soffit Traps at 17" and even then it has to be where the problem is happening.
Okay then, the next REW session will find me raising the sub level and experimenting with that null. It's my understanding that if it reacts to EQ, then it's not a room mode, correct?To me sub level still looks about 5 dB low and I'd be worrying about the peak between 45 and 70ish.
Do you have the ability to EQ the sub? Don't do a ton, just hit the middle of that broad null and see if you can change it with EQ. Don't do more than maybe 3 dB.
EDIT: In reviewing my measurements I found that the dip succumbed to the sub's phase adjustment as shown below. So along with EQ experiments, I'll be sure to check phase settings when remeasuring the Center+Sub response.