Eminent Technology

Rotary Woofer Project Installations

Modern digital audio recording systems have no low frequency limitations. Almost 30% of Modern movie soundtracks, and even Television shows have content down to a few Hz. These sound effects are not being reproduced by conventional loudspeakers in a movie theater or a home.

Niagra's Fury at Niagra Falls (6 rotary units)

Although not well understood, at low frequencies conventional cone loudspeakers have an impedance mismatch with the air. For each halving of frequency, in theory, a cone woofer must move four times as far to maintain the same output. The impedance mismatch starts where the wavelength of sound matches the dimensions of the cone, actually a fairly high frequency. The upshot is that cones are very inefficient loudspeaker transducers only converting about 1% of the electrical energy into sound. A horn loaded loudspeaker, sometimes used in professional applications is much more efficient, however they are large and impractical at very low frequencies.

Evergreen Aviation's Titan Exhibit (Single Rotary Woofer)

Because the rotary woofer is so effective at producing very low frequencies, there is another aspect of this new product which involves our understanding of hearing. It can produce sounds well below 20Hz, in fact it can produce sounds below 1Hz. Getting consumers to believe that sound reproduction has value between 1-20Hz is challenging. This product generates controversy even among audio professionals because many believe that it produces sounds we cannot hear.

Rotary Woofer Evergreen Avation Exhibit — Rotary Woofer Evergreen Aviation's Titan Exhibit

The Middle Collegiate Church, East Village, New York Marschall & Ogletree virtual pipe organ (2 rotary woofer units)

We have been taught that we cannot hear sounds with a frequencies below 20Hz. This probably originated from hearing studies done by Fletcher and Munson back in 1933 which happened to stop at 20Hz. The results of this study were published in hundreds of textbooks. More recently a number of scientific studies have been completed which show that we can actually hear sounds down to a few Hertz. Eminent Technology has already conducted one double blind study demonstrating that more than 91% of the participants could hear 16Hz, 8Hz, and 4Hz tones. Conventional audio systems with cone sub woofers are usually limited to about 20Hz. Compared to our hearing, conventional loudspeakers represent a high pass filter to sound.