Updated 7/30/04

Eminent Technology’s founder, Bruce Thigpen has invented a new type of loudspeaker, The Thigpen rotary vane transducer.

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, especially at low frequencies requiring a large surface 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 creating a low radiation resistance by the motion of the blades. The high velocity vane by its motion sweeps a relative large area and volume of air. The transducer can grab air in close proximity to the blades. 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.

Shown below is a 3 inch prototype

The frequency response graph shows the performance of 3.5 inch rotary vane transducer compared with a 4 inch cone using the identical voice coil, magnet structure, and input power in an infinite baffle. The rotary vane transducer can produce roughly four times the acoustic output at 30Hz.

The acoustic output of the device is not limited to motion of air particles in front of a cone or the maximum displacement of the cone. It can move additional air particles pulled into the vane from either side. This method of moving air achieves a much improved impedance match with the air relative to a moving plate of the same area. Horn loading is not necessary with this method of acoustic transduction.

Eminent Technology is currently experimenting with a number of different mechanical configurations, also acoustical, electrical and mechanical methods of altering the pitch or shape of the vane assembly.

Below s a photograph of another prototype approximnately 20 inches in diameter along with its 1 watt 1 meter frequency response.

A genuine new transducer is rare. This acoustic transducer will not replace conventional speakers any time soon. The transducer has many limitations. The primary limitation is random noise but test data suggest that it may have a significant advantage in large venue professional speaker applications where high sound pressure level, low or infrasonic frequencies are required. 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 eight 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

Email: brucet@eminent-tech.com