@rlawry Yes, it's a known effect that the frequency at which sounds can be localized for humans is around 100-120Hz. This is why the THX reference crossover frequency is around 80.
When I say Integration, I mean two things. Speaker integration means that the frequency response and amplitude from the subwoofer to the speaker is measurably seamless. The measured response should be like measuring one large speaker, not a speaker plus a sub.
The second, much more difficult part is to integrate into the room. While managing the radiating patterns of a speaker as it goes from omni to directional is important, at the low end almost all speakers are acting as omnidirectional radiators.
Subwoofers however are purely omni. At 80Hz the wavelength is approximately 15' or around 5m.
The bigger issue for subs, or any full-range speaker is the way rooms behave. As you go down in frequency you find room modes. Peaks and valleys that the room acts like a bell and rings. It's more than just about radiating direction. This is why parametric EQ's and bass traps become so important. I've measured over +-20dB variations in modest living rooms under 80 Hz. That's the equivalent of 20x more or less power output. A 200 watt sub may sound like it's a 4000 watt sub at certain frequencies.
Unfortunately most attribute these problems to any number of mythical goblins which aren't really to blame. My favorite is "Electrostatic speakers are too fast for a subwoofer." Bunk.
That ET subwoofer with the blades, didn't chop up the sound. It acts like a fan that could change direction very rapidly (for a fan).
Look at it this way. There's no difference between a desktop fan and a speaker in terms of producing positive air pressure. A woofer pushing towards you produces the same effect as a fan turning so that air moves towards you. At 0 Hz we don't call it sound, we call it "wind" . :) What your desktop fan cannot do very quickly is change directions. My ceiling fan takes about half a minute to do this, so for all practical purposes I am limited to a 0 Hz output.
The bladed subwoofer is a very cool idea, which is to use a fan with a DC coupled motor that can change direction nearly instantly (compared to my ceiling fan). To produce a positive going output, the blades turn one way. When it reaches the peak, the blades turn another.
One big advantage of this is that there is no maximum excursion limit. With a woofer, you have a maximum amount of movement, measured in millimeters and often spec'd as Xmax. Beyond this damage will occur, but even before this there is significant non-linearity in travel. A fan based subwoofer however can turn infinitely in one direction, allowing for a genuine 0Hz wind.
But I digress....again! :)
Best,
Erik