I did, yes!
Took some measurements in REW and sure enough, there's a big deep null right around 70hz.
View attachment 63319
I then turned off the sub and re-measured and that null trough is still hovering around 70.
View attachment 63320
Before fudging with other settings, I decided to move the sub another couple feet from the wall.
View attachment 63321
Sure enough, the null got lessened a bit. So I'm
thinking that I have some very bad nulls in my room and that somehow my old sub was covering them up perfectly? I don't have old REW measures from back then, but it was definitely more balanced and less notchy. It was a much smaller 10" Polk too.
Am I right in thinking that only way to know if I don't have a lemon sub is to take it out in a field and sine sweep it there? Or is it more likely it's the room and not the sub.