Eminent Technology's TRW-17 Rotary Woofer (pictured on the left) doesn't have a cone-type woofer or even cabinet; instead it looks like a fan or propeller, yet it reproduces frequencies down as low as 1Hz, and is powerful enough to be heard more than 3 miles away!!!!! High-end subs are lucky to make down to 18Hz, and the vast majority of subs won't even touch 30Hz on a good day.
How does it do it? The TRW-17 really is a constant speed fan, but its blades are modulated up and down and side to side in order to generate sound. It's a wonderfully-simple design that makes you want to hit your head and say, "Doh!" As a result, the transducer (you can't call it a loudspeaker) can push far more air than any speaker/cabinet combination, and that lets it easily reproduce the 11Hz sound of a helicopter's rotor blades, the real infrasonic shock of an earthquake, or the rumble of everyday wind. If this system takes off, just wait and see how realistic movie sound finally becomes, or theme park rides, or war simulators.
The downside? First of all, the TRW-17 Rotary Woofer retails for $12,900, but you have to build it into a room so it acts as an infinite baffle (a totally closed speaker system). Eminent Technology will take care of all that for you and add the amplifier and cross-over network, but it pushes up the price to $25,000.
That being said, numerous audiophiles with too much disposable income have already installed the unit, but so have museum installations like Evergreen Aviation's Titan Missile exhibit and the Niagra Falls Welcome Center (you can see why this unit makes sense for them). It doesn't seem like there are any theater or pro audio installs yet, but expect some as the word gets out.
You can read more on the technology behind the TRW-17 here.
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