Well I finally did this test. Dual SVS CS-Ultra in the same corner powered by EP2500. Calibrated 75 dB w/ RadioShack analog SPL meter @ 0mv. Bass xover 80Hz. Sub channel only. Room is ~7,000 cubic ft.
Sorry for not following the format but I took a lot of samples. SPL format is LP/1m.20 Hz tuning
+5mv: 108/11916 Hz tuning
I heard new things shake and rattle at +5. Got some of that "chest-pounding" that everybody raves about for +5 @ 1m. Wish I had a smaller room. Saw the clip light briefly flicker once at +5 so I stopped there.
I think in my next place the subs will be nearfield. Yeah, definitely nearfield