Yes,
I own two Hsu Research TN1220 HO subwoofers with their Model 500A amp with 24db per octave high and low pass x-overs at 51hz. I sit midway, [in the center of my listening room], between the subs, in which one is near the middle of my front wall between my speakers and the other is in the rear of my room near the middle of the rear wall.
My listening room, including the dining room and kitchen due to large open spaces is roughly 23 x 23 x 8.
Using a Rat Shack digital sound level meter, with corrections, and the Hsu Research CD-R with 1/3 octave warble tones and a 100 hz reference:
I have a broad peak of about + 7 db at 16hz! and 20hz,
a -4db dip at 25hz, a -3db dip at 31.5hz, same as the 100hz level at 40hz and 63hz, a -2 db dip at 80hz, and a big + 8 db peak at 50hz.
With both subs along the rear wall I have a broad +7 to +9 db peak at 16 to 25hz, a -3db dip at 31.5hz, same as 100hz at 40hz, a -2db dip at 63hz, a -4 db dip at 80 hz, and still have the +8db peak at 50 hz.
The 50 hz peak surprised me because running the speakers full range without the subs or high pass filter resulted in the same +8 db peak as when using the subs, mains, low pass, and high pass filters all together!
I expected the 50 hz peak to be reduced in level by about 6db by using the latter due to the natural -6db dip at the x-over point using 24 db per octave filters, but it was not reduced at all!
Very strange indeed.