Research and Development at Eminent Technology

In keeping with Eminent Technology's tradition of creating innovative products in the audio field, we are constantly researching and developing new audio technology. We also perform loudspeaker design services to other companies. For more information contact us.

Updated information about this technology can be found here Rotary Woofer web site

Press Release 3/10/05

Eminent Technology’s founder, Bruce Thigpen has invented a new type of loudspeaker, The Thigpen rotary woofer (patent pending).

The transducers sound originates from rotating vanes or surfaces that change pitch in response to the audio input signal. The advantages are improved impedance match with the air, high potential conversion efficiency at low frequencies, low distortion, a very high theoretical limit for acoustic output with a small transducer, and infrasonic response to DC.

In a conventional cone type direct radiator loudspeaker, the acoustic impedance match with the air is poor at low frequencies requiring a large surface area to achieve high sound levels.

The invention transducer acts against a comparatively large volume of air by dispensing with the cone or vibrating surface of a conventional loudspeaker. Rather than area, in this loudspeaker the impedance match with the air is proportional to the velocity of a vane moving through the air. At diameters equivalent to conventional direct radiator loudspeaker, the invention transducer achieves a superior impedance match with the air, essentially continuosly variable. The impedance match is proportional to the ratio of the desired output frequency period, the blade rotational period, the number of blades and the size of the blades. This means much more bass output is available from a small sized loudspeaker.

As an application example Eminent Technology research and development applies the Thigpen Rotary Vane Transducer to automotive applications. A transducer which is the first in many years that represents a viable alternative to the ubiquitous cone woofer.

For very low frequency reproduction conventional woofers need relatively large box volume and radiating area. When a box designed for two twelve inch woofers is placed in the trunk of a compact car the trunk becomes almost unusable. The Thigpen rotary vane transducer has the ability to produce the same acoustic output at very low frequencies with a much smaller radiating area, here about 7 inches in diameter when coupled to an infinite baffle.

The photograph below is a box volume comparison between a conventional bandpass enclosure with two twelve inch woofers and the automotive prototype. The rotary vane transducer in its enclosure is on top.

We measured the frequency response of both the two twelve inch woofers (red trace) and a single RVT-15 prototype installed in the trunk (1 watt) of a Honda Accord. The microphone is placed in the drivers seat of the car and the windows were up.

It can be seen that the rotary vane automotive prototype transducer (orange trace) with a much smaller radiating area and box size has roughly comparable efficiency and performance below 75Hz and superior efficiency below 40Hz. The maximum sound pressure level achievable with the automotive prototype was 120dB at 20Hz or lower, practical for a typical car audio system and impressive for a 7 inch diameter woofer with a modest associated components.

A genuine new transducer is rare. The transducer has many limitations. Research is continuing to determine optimum configurations and where it can be applied in the market place. A patent application has been filed.

Bruce Thigpen holds nine audio patents, among the Eminent Technology accomplishments are: the first captured air bearing tonearm, the first full range push pull planar magnetic speaker, and the first flat panel computer multimedia speaker. Eastern Asia Technology Ltd., licenses Eminent Technology’s planar magnetic loudspeaker Technology and markets some of its planar products under the Philips brand name.

For more information contact:

Bruce Thigpen

Eminent Technology

225 East Palmer Ave.

Tallahassee, FL 32301


Phone (850) 575-5655

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