Excuse me, you are the one going off topic bringing mechanical motor driven sirens into the post in your little description of what you think a compression driver is. Now keep up Poncho because I am not going to explain this 100 times until you get it.
A compression driver works by using an apparatus to compress the air that is being excited from a vibrating diaphram, in this case a woofer cone.
Now, this usually only works well in the higher frequency range, but the navy has been using something like this in sonar systems for years.
But the normal long excursion of a common subwoofer does not work, you need the cone to remain stiff and basically just vibrate at a low frequency, 50-80hz in this case. So using a 5" coil and an incredibly stiff suspension, you control the movement of the cone. The suspension is so stiff that you can jump on it and it wouldnt move. Because as you said, 20K can equate to about 25 hp of force, so it would take 25 horses to push on the cone to make it move.
The vibration at this power level is just about what you need to create the proper air compression and correct the mismatch of air impedance from the cone to the outside air.
Now its burp only, because playing transients would create horrible electrical impedance drops and would blow an amplifier.
