Hi TK,
You're correct on the combination of DSP processing, long-excursion drivers and very large amplifiers (500 -600 watts in the new Axiom EP500/EP600 subwoofers). But you still have to make the enclosure larger (the EP600) if you want to keep the lowest frequencies linear to 16 Hz or lower. There are some sub manufacturers who claim subwoofer response to 17 Hz or lower. They may say, "our sub goes down to 17 Hz"; what they don't tell you is that the driver may move at 17 Hz, but its output may be -15 dB at that frequency, so there is no useful output.
Thanks to JohnK for his post on Fletcher-Munson. As to "hearing" those low frequencies, we feel/sense them more than hear them. For instance, if you look at the harmonic content of certain instruments--a pipe organ, for example--the 2nd harmonic of a 16-Hz pedal tone at 32 Hz has a greater intensity than the 16-Hz fundamental. We hear the 2nd harmonic at 32 Hz easily, but when you add a subwoofer capable of reproducing the fundamental at 16 Hz, it does add a sense of weight and power, the sort of thing that moves the pew under your butt in a big church when you hear a pipe organ played live.
Regards,
