bao - check out the Bossobass system thread in the Bass Systems part of the forum - there are several images in there showing 9 has content down to low single-digit Hz at quite high levels, but as noted above, it sounds like you prefer distinct, separate sweeps, rather than full-bandwidth content.
What system are you running?
It is upstairs in two story wood frame house.
28' x 23' x 8'
Carpet but room is somewhat "bright"
Subs: two sealed JL Audio f113 Fathom subs, -3 dB at 18 Hz, -10 dB at 16 Hz
Front L/R: B&W 802 Diamond, 34Hz - 28kHz ±3dB on reference axis
Center: B&W HTM2 Diamond, 41Hz - 28kHz ±3dB on reference axis
Surrounds: B&W 804 Diamonds, 38Hz - 28kHz ±3dB on reference axis
Back Surrounds: Old Paradigms
Amp: Parasound Halo A51
250 watts RMS x 5, 20 Hz - 20 kHz, 8 Ω, all channels driven
400 watts RMS x 5, 20 Hz - 20 kHz, 4 Ω, all channels driven
Pre/Pro: Integra DHC 80.3 with Audyssey XT32
Front channels and plasma TV are along the long 28' wall.
One sub is on front wall and other sub is behind MLP on rear wall but strangely neither is at middle of wall.
I used REW while moving them around (what a pain) to try get a good response at MLP.
I then run XT32 with a "close" mic pattern around the MLP. XT32 handles two subs "sort of". It measures each one.
Audyssey set all XO to 40 except center which got 45 Hz.
LPF of LFE: 120
Subwoofer Phase: 180 degrees
It sounds awesome (e.g. EoT, FotP) but i think i will buy some HF room treatments.
Also, nothing is on spikes or special "pads" but i think i may invest in SW pads since it is upstairs.
Also, I use it a lot (maybe 50%) for music.