The Air Bearing Origins of Bruce Thigpen’s Turntable Innovations

At an early age Bruce developed an interest in sound reproduction and electronics. In 1975 he saw an air bearing demonstration in a physics class at a local college. Bruce went to find out who made the air bearings so he could try to build a tonearm with the parts. He found Lew Eckhart in the machine shop and asked about how the parts were made. Lew, an engineer, turned out to enjoy audio as well and had already made a sophisticated air bearing turntable and tonearm. After numerous visits to the lab Bruce convinced Lew to provide him with parts so he could make his own turntable. Lew was very generous, provided parts and taught Bruce tonearm and turntable geometry, machining skills, as well as how to manufacture air bearings. After the turntable was completed Bruce convinced Lew that the turntable Lew had was commercially viable. Lew contacted a number of companies and entered into an agreement to license the turntable design to Infinity and the Infinity Air Bearing turntable was born. The Infinity turntable was manufactured in Japan, a very small number were produced until Infinity was acquired and the project was canceled.

In the Late 1970's, Lew Eckhart introduced the turntable concept to a Tallahassee engineering firm, Wayne H. Coloney Company. Wayne Coloney decided to manufacture the turntable and Bruce Thigpen became the project engineer.

While working at Coloney Bruce received his first patent on the record vacuum hold down, never used by Coloney, but used later by SOTA in its Star series turntables. When Coloney Filed for chapter 11 bankruptcy in 1982 the turntable Inventory was sold and re branded Mapleknoll. Bruce made a decision to start his own company that same year.

Model One and Air Bearing Design

Eminent Technology's first product was an air bearing phonograph tonearm dubbed the Model One. Although utilizing different geometry it was similar to the tonearm used on the Infinity and Coloney AB-1 turntables. In that same year the compact disk player had been introduced and the compact cassette player had already over taken the LP as the best selling prerecorded media. A high end tonearm for playing phonograph records was not something a company could count on for long term success. At the onset, it was apparent that other products would have to be developed.

In order to design a practical air bearing tonearm the air bearing had to be very efficient only requiring a small amount of air to operate. An air bearing is not simply a series of holes which direct air to the surface of a spindle tube. In the case of the Model One or the ET-2 Tonearm air pressure causes a hard coat anodized aluminum spindle to float on a thin layer of air. The air bearing includes a manifold where a pressure cavity provides the air pressure for a series of very small air holes, capillaries, which restrict the flow of air to the surface of the bearing. The spindle floats with a surface pressure less than that on the manifold side of the bearing. If the spindle is canted in the manifold bore the higher pressure in the manifold acts as a centering or restoring force because air cannot rush out of any one capillary with more exposure to the atmosphere.

Planar Magnetic Innovation

By 1985 The compact disk was gaining traction and the end of the LP phonograph record was thought to be in sight. Bruce had developed both electrostatic and planar magnetic/ribbon loudspeakers so it was decided to concentrate on planar planar magnetic loudspeakers. Magneplanar had been successfully manufacturing single ended planar magnetic loudspeakers for many years. Bruce developed a push pull version of a planar ribbon loudspeaker which made efficient use of magnetic material. His fourth patent, granted in 1987 was for an efficient motor structure used in planar magnetic loudspeakers.

In order to manufacture the loudspeaker the company moved from a 2000sq ft to a 6000 square foot building. Although rare today for a U.S. based audio company, Eminent Technology created a facility to manufacture most of what it produces in house. Painting, welding, metal fabrication, woodworking, woofer cabinets and planar transducers are built in house. Even the connectors on the back of the speakers, designed by Edison Price and called Edison Price Music Post, are manufactured at Eminent. This capability aided in the development of later products.

The LFT-8

Between 1989 and 1990 the LFT-8 three-way hybrid loudspeaker was introduced. The LFT-8 features a very low crossover frequency between the woofer and planar ribbon midrange panel. Electrically the crossover is 30Hz, acoustically it is about 180Hz. Unlike many hybrids this large overlap between the woofer and the midrange panel minimizes audibility of the crossover and allows a low coloration transition between the woofer and the mid range panel. The LFT-8's high consumer ratings, longevity and upgrade program have made it one of Eminent Technologies most successful products.

Planar loudspeakers utilize polyester diaphragms laminated with aluminum foil, about half the thickness of household aluminum foil. Eminent Technology's diaphragms are also manufactured in house. The conductor pattern is silk screened onto the foil with a ink resist. Then an etchant is used to remove the foil around the resist. After the ink is removed, a conductor pattern remains. The diaphragm is then tensioned in a frame and terminations are added. Once the conductors are in the presence of a magnetic field and current is supplied from an audio amplifier, the diaphragm moves following the audio signal. The disadvantage of this type of loudspeaker is efficiency and limited low frequency capability, the advantage is low distortion and transient capability.

LFT-10

The LFT-10 was intoduced in 1993 as a planar car transducer to capitilize on the popularity of automotive sound systems. It met with limited success.

LFT-11

By 1995 the personal computer was prevalent and sound cards were included. Digital recording, games, and sound effects were transitioning to the computer. A computer multimedia speaker, the LFT-11 was created based on a modified LFT-10 for the two desktop panels with two 6.5 inch woofers in a third cabinet. This product was widely recognized by a number of audio and computer magazines as the best sounding computer multimedia speaker.

Monsoon MM-700 Computer Speaker

Eminent Technology had developed a still smaller transducer for a lower cost computer speaker. The smaller transducer was licensed to Sonigistix Corporation in Vancouver Canada. Sonigistix and Eminent Technology co developed home and computer products based on flat panel loudspeakers manufactured in Canada. These products carried the Monsoon brand. A smaller planar ribbon tweeter was created at Sonigistix and is used in Philips Consumer Electronics home theater in a box and other loudspeaker products. The tweeters are manufactured in China. Both the planar ribbon panel and tweeter products have found there way into several other loudspeaker company offerings. Modified versions of the Sonigistix transducers can be found in AV123 loudspeakers as well as models from VMPS and others.

Sonigistix

In 2002 Sonigistix was sold to Eastern Asia Technology Company, (Eastech), and renamed Level 9 Sound Designs still in Vancouver. Shortly thereafter Level 9 was moved to China. Another spin off of Sonigistix is called Magnetic Audio Devices (MAD), designers and builders of planar magnetic transducers primarily used for professional audio applications.

Eminent Technology LFT-16

The LFT-16 is a three-way hybrid loudspeaker developed in 2025, built around a refined version of the LFT-10 and paired with an Eastech-designed planar ribbon tweeter.

Eminent Technology TRW-17

The TRW-17, In 2006 a new type of sound reproducer, the worlds first rotary woofer was introduced. It has specifications and performance capability like no other woofer on the market. It can reproduce sound from 0Hz to 20hz and is designed to fill in below the frequency range of existing subwoofers. Eminent Technology now faces the challenge of convincing the general public and engineers that we can hear below 20Hz and content exist that can be reproduced.

Each decade of sound recording and reproduction brings wider and wider bandwidth. Four years in development, the rotary woofer creates sound by rotating a set of blades. Sound represents very small changes in air pressure. As the blades rotate at a constant speed, the pitch follows the signal from the audio amplifier changing the pressure of the air just as a cone loudspeaker does. The blades have no pitch when there is no audio signal. The rotation of the blades grabs the air much more effectively than a cone and can enable high sound levels with a much more efficient conversion of energy as compared to a cone woofer. The rotary woofer has acoustic output equivalent of a very large number of conventional woofers many times its size at extremely low frequencies.

Rotary Woofer Project Installations

Model Twenty Guitar Speaker

The Model Twenty, in 2021 another new type of patented sound reproducer from Eminent Technology is applied to the Guitar/Musical instrument speaker industry. Moving away from the conventional direct radiator cone type loudspeaker, Eminent Tehcnology's transducer improves bandwidth, distortion, and dispersion while maintaining the same efficiency. A much thinner form factor and light weight further improve the user experience.

Rather than just projecting sound straight ahead, the model twenty offers wide dispersion. Drums, electric bass and PA systems have wide dispersion, now the audience can get the same experience with an electric or acoustic guitar. The Model Twenty has much lower distortion, less compression and wide bandwidth suitable for electric or acoustic sources, keyboards, and synthesizers. The thin form factor works at home and it's light weight allows far easier transport and set up for your next gig.