Planar loudspeakers. Inefficient. Power hungry. Big. Hard to place. Low WAF (wife acceptance factor).

 

Whatever the drawbacks of electrostatic and ribbon loudspeakers may be, there is no denying that with the right material they can absolutely dissolve into thin air. The first time I ever heard a pair of Magnepans I heard some deficiencies, but I also heard the performance in the room with me in a way that I had never, ever heard with conventional loudspeakers. This is precisely why, despite the requirements of planar loudspeakers, their siren song exerts such a strong pull over those of us who have heard their magic.

 

One of the enduring planar loudspeaker companies is Bruce Thigpen's Eminent Technology. Not only is Bruce a key figure in planar loudspeaker design, he's one of the guys you need to include in the discussion when you talk about influential figures in modern loudspeaker design. I'm sure that there are more than a few loudspeaker designers that I would love to interview who would include Bruce on their list of influences, and with that I am very pleased to present this month's AV Enthusiast Interview: Bruce Thigpen of Eminent Technology.

 

AV Enthusiast:  How long have you been working in the audio industry, and did you work for anyone else prior to establishing Eminent?

Bruce Thigpen:   I was lucky enough to get a job with a local engineering company, Wayne H. Coloney company, in the mid 1970's. The company had a mix of civil engineering and mechanical engineering projects along with military contracts. I have to give them credit for giving me real world education in engineering.

Lew Eckhart was an employee of Wayne Coloney and I had met Lew while attending physics classes at the local university. Lew had developed a complete air bearing turntable and tonearm system. Audio was a hobby of mine and Lew was kind enough to provide me with parts so I could build my own turntable.

Coloney decided to manufacture the air bearing turntable which was designed by Lew Eckhart, called the Coloney AB-1 which made the cover of Stereophile in 1982. I became the project engineer for the turntable  which lead to work with air bearings. Coloney had financial difficulty in 1982 and the turntable project was sold and became Mapleknoll.

AVE:  When was Eminent established?

BT:  Coloney closed its doors for a period of time and needing a job I started  Eminent technology in 1982. Our first product was an air bearing tonearm.

BT:  My college degree is in business, there was  no engineering school where I attended college, so I took physics, math and audiology classes.

AVE:  Everyone has influences. I would qualify myself as a fan of several loudspeaker designers' work. Starting out in this field, were you particularly influenced by anyone else's work? Which loudspeaker or loudspeakers cast their spell on you prior to your getting involved in loudspeaker design?

BT:  The loudspeaker designers that influenced me most are Henry Kloss, Peter Walker, Arthur Janszen, Jim Winey and Paul Klipsch. Influence in transducer research comes from Frederick Hunt and Harry Olsen. I try to incorporate the philosophies of these designers in our products.

AVE:  Eminent is known for planar loudspeakers. Aside from being hybrids, people are going to compare Eminent loudspeakers to your competitor Magnepan. I understand that your ribbon designs differ from the approach that they have taken with their designs. Break it down for the reader who hasn't read the white papers: how does a ribbon driver produce sound, and how does your ribbon driver differ from the competition?

BT:  Mageplanar is one of a handful of what I consider to be the best American audio companies. It is only when you design and manufacture planar transducers that you appreciate how well engineered Magneplanar  products are.

We are only competitors for a part of that business.

 

Magneplanar popularized the term 'planar magnetic' as a type of loudspeaker that uses magnets adjacent to a stretched film with conductors aligned on the film such that when current flows through the conductor the diaphragm moves back and forth displacing air and making sound.

 

A ribbon loudspeaker is made with just a foil conductor without turns and no film substrate, placed in a magnetic field. The true ribbon transducer can be either a microphone or a tweeter. Marketing departments have  blurred the definition of these two transducer types such that there is very little distinction between the ribbon and planar magnetic terms as it applies to a family of loudspeakers. The damage is done.

 

Like Magneplanar we build planar magnetic loudspeakers. We are building hybrids and Magneplanar is building full range products. Our tweeters are a cross between a planar and ribbon loudspeaker. All of our planar magnetic transucers are push pull.

AVE:   The LFT-VIII has been around for a while, and seen some improvements along the way. Congratulations for designing an enduring loudspeaker. For whatever reason, this is a loudspeaker that doesn't seem to get a lot of attention from the mainstream audio press. I can't seem to find anyone who has anything but praise for it among the few editorial reviews I've seen and the many owner reviews on audioreview.com.

BT:  My goal in running Eminent has been to put as much of the return on the sale of products back into R and D instead of marketing. So yes, part of our different business model results in lower visibility than a company that runs full page ads. We hope that a few customers will appreciate our approach.

 

Although low profile we developed cone loudspeakers for the largest Indonesian television-audio company and licensed transducer technology for the Monsoon computer multimedia and home speakers. We are designing different sound sources for Boeing, the Univeristy of Hawaii infrasound research laboratory, and projects we cannot discuss. We recently installed rotary woofers in Niagaras Fury and the Evergreen Aviation museum.  In many respects we are not a traditional high end audio company.

AVE:  What year did the first LFT-VIII come out?

BT:  We introduced the LFT-VIII in 1992 after manufactiuring three full range planar speakers, the LFT-III , LFT-IV and LFT-VI. The model numbers of our products are the engineering projects. The gaps in the numbers are either in house research, research projects for other companies, failures, or products we decided not to make.

AVE:  The design is fairly low efficiency. Do you feel that the LFT-VIII with the right amplifier is capable of reproducing the dynamics required for home theater use and playback of large scale orchestral pieces, or is this a loudspeaker that you feel is better suited to two channel usage with material that demands less bombast?

BT:  The LFT-VIII is low efficiency. In a loudspeaker there is an inverse relationship between bandwidth and efficiency. Flatness of response is also traded for efficiency. We decided to trade efficiency for those characteristics.
   

Today if you are a loudspeaker company you need to be in home theater to survive. Because a home theater has multiple channels the sum of the channels makes efficiency less critical. About 80 percent of current LFT-VIII sales are for home theater, so it must not be a problem. If you need a loudspeaker to fill a very large room at high sound pressure the LFT-VIII or other planar or electrostatic type loudspeakers are not the right choice. 

AVE:  One of the reasons that planar and electrostatic transducers have so many fans is the magical way that they just dissolve with the right recordings. I think it's a lot easier for these designs to sound like the performance is in the room with you than it is for loudspeakers using conventional drivers. What are your feelings regarding ribbon vs. electrostat, and the strengths and weaknesses of both technologies?

BT:  No loudspeaker is perfect, at least not yet. If they all sound different, odds are that none of them are right.

 

The electrostatic loudspeaker has a advantage in quickness, probably less so today with modern magnetic materials. It also has the lightest diaphragm. Planar magnetics and electrostatic loudspeakers are both equal in terms of low coloration and the way they couple to the air ( a really good impedance match). The planar magnetic has an advantage in terms of efficiency and bandwidth per unit area over an electrostatic. They are both excellent tranducers.

AVE:  There are some loudspeaker design approaches that attempt to capture the enviable qualities of planar loudspeakers using conventional drivers. Richard Vandersteen has made a career of designing loudspeakers that are relatively "baffleless" and pursue time coherency. Tannoy has established a dynasty based on a point source driver design that is on it's sixth decade in production. Open baffle designs are propagating. What are your opinions regarding these approaches?

BT:  I really like Vandersteen products. Anyone who buys them will be happy. They are low coloration and very neutral.  I have not listened to Tannoys in 30 years so I do not have a comment.

Cone drivers are relatively easy to make, the tooling, software and parts are readily available. The really difficult part is getting them to sound good. You have to spend a lot of time with them. It is easy to make a bad sounding cone speaker.

Planar transducers are also easy to manufacture, but you have to create your own tooling and modeling capability. By comparison they almost automatically sound good. It is hard to make a bad sounding planar speaker as long as you know how to work with the limitations of the transducer.    

AVE:  Eminent loudspeakers are sold through the traditional brick and mortar model. I think the right product can really fly with direct sales. There certainly are a lot of internet direct audio success stories. It could possibly lead to a price decrease for the consumer and a profit increase for the manufacturer, in addition to the potential for the product making it into more homes.

Obviously the drawback is that internet direct loudspeakers can't be auditioned, but you also can't audition a loudspeaker that there aren't any local dealers for either. In addition, the mainstream audio press doesn't seem to pay a whole lot of attention to internet direct products when conducting equipment reviews. Have you ever considered going internet direct? What do you think the upside and downside of both business models are in regards to Eminent?

BT:  You have summed the marketing dilemma up nicely. I believe your assessment of the tradeoffs in the two aproaches to marketing is correct. At one time we had about 100 dealers in the U.S., today we have less than 25. We will sell direct to anyone outside of a reasonable coverage area of our dealers. We pay shipping to offset the cost difference and offer a refund. This does not completely solve the pricing difference. Unlike many smaller speaker companies we manufacture most of the speaker in house. At this writing raw material prices are going up at a significnt rate so prices will go up in the near term.

 

Another aspect is overseas sales which become more difficult for a direct marketer. The audio business is still changing. We may make the jump to all direct sales at some point. I cannot say when.

AVE:  Your rotary subwoofer may be the first original idea in audio in quite some time. How did that idea come about? With a ceiling of 40 Hz, a lot of floorstanding loudspeakers could be paired with the rotor with no need for a supplemental subwoofer. Obviously this baby hits low, and from the looks of the chart on your site, hard as well. Strike that, according to that chart there is no subwoofer in production that is even close to inhabiting the same zip code as the TRW-17. How fast does the rotor respond in comparison to a conventional driver?

BT:  I was flying a model helicopter and while looking at its rotor and pitch mechanism on the ground, the epiphany hit that it was a loudspeaker.

 

This was on a weekend and we have a pretty good shop. Becuse I crashed the helicopter a lot (no reflection on my real fixed wing piloting skills!) I had plenty of spare parts. It took about twelve hours to make the first prototype. It worked well enough to ' bet the company' on it.

In the frequency range that the TRW-17 responds it is the same speed (as a conventional sub). I'm not interested in competing with conventional subwoofers, rather to offer a new frequency range for audio systems. Of course there are plenty of skeptics, but a double blind study shows that it is completely valid.