Paul McGowan gets asked about rotary subs.

Paul McGowan of PS Audio has for years posted frequent (daily?) videos on YouTube in which he answers questions sent in by people from the world over. I just watched one in which he answers a question sent by a guy in India, inquiring as to why rotary subs are not more popular. Paul gets around to completely answering that question, but before doing so says this:


"The Rotary Sub was invented by a guy named Bruce Thigpen, and Bruce is a VERY (Paul’s emphasis, not mine) creative inventor who used to have a company---maybe he still does---called Eminent Technologies (sic. It’s actually named Eminent Technology). And Eminent Technologies, they made some GREAT (again, Paul’s emphasis) loudspeakers. They were---if I remember right---they were planar, or electrostatic---I think they were planars, they weren’t electrostatics, but they were REALLY (Paul again) good. And I don’t know what ever happened to that, but I DO know that Bruce figured out a way to make a subwoofer that could go well below what normal subwoofers do."


But this post is not about the Eminent Technology TRW-17 Rotary Subwoofer (there aren’t rotary "subwoofers", there is only one Rotary Subwoofer, the product of ET alone), it is about Eminent Technology itself. I mean geez, if Paul McGowan doesn’t know if Eminent Technology is still making planar loudspeakers, just how low IS the visibility of the company?!

To set the record straight: though Paul differentiates between a "planar" and an "electrostatic", while not all planars are electrostatics, all electrostatics are planars. I routinely see Magnepans referred to as planars (by Steve Guttenberg, for instance), which they of course are. But so are electrostatics. When Paul and Steve say planar, they are speaking of planar-magnetic loudspeakers. Both Magnepan and Eminent Technology make them.


The Eminent Technolgy LFT-8 planar-magnetic loudspeaker was introduced in 1989/90, and remains in production today. It has gone though a few revisions over the past thirty-three years: in 2007 an improved woofer replaced the original, with a change to it’s nomenclature: the LFT-8a. In 2015 an improved tweeter replaced the original, the new model designation being LFT-8b.

The LFT-8b remains available, and there is also a new version of the LFT-8: the 8c. The 8c consists of the same planar-magnetic panel as the 8b (which contains the midrange---180Hz up to 10kHz---and tweeter---10kHz and above---drivers), but with the monopole woofer of the 8b (for frequencies 180Hz and below) replace with a "gradient" dipole woofer (still a sealed enclosure, but with a 6.5" rear woofer added to the 8" in the front), which simply bolts on in place of the monopole woofer enclosure. Also included with the 8c is a power amp for the woofers, and DSP for the low-pass x/o filters for the woofers, time-alignment of the panels with the woofers, and equalization.

The LFT-8b retails for $3200, the 8c $4500, shipping in the U.S.A. included.


Magnepans are commonly discussed and owned (I own a pair), but the Eminent Technology LFT-8 remains virtually unknown (I also own a pair of the LFT-8b). Why is that? It has received rave reviews (REG in TAS, cudos from VPI’s Harry Weisfeld---who characterized the midrange of the LFT-8b as "the best I have ever heard", a number of reviews in the UK hi-fi mags), yet remains virtually unknown to the vast majority of audiophiles. I know ET has few dealers and does no advertising, but still.....


@tomic601: Yeah Jim, Richard Vandersteen is not your typical high end audio designer and manufacturer. If I wasn’t a committed planar enthusiasts it would be Vandersteen’s I would probably own. I have listened to music through them for many hours at Brooks’ shop.

I had the pleasure of joining Brooks for dinner with Richard at the steak house in the venue Richard was showing at during one CES in the late-90’s, and found him to be very down-to-earth, a regular working-class kinda guy. No "snooty" pretenses at all, of which I saw a lot at various CES’ I attended.

Richard ordered the wine, he obviously knowing his stuff. I’m more of a whiskey drinker, and Brooks? Milk. I swear to God! ;-) Richard picked up the tab (Brooks and I had our women in tow, and there were a few others in our party), a good thing as it was the highest I’ve ever seen!

@bdp24 thanks for the aluminum hex wrench suggestions.  I hadn’t thought about the magnets but you’re right.


@gktaudio you’re absolutely right.  Something my friend and I have pondered is whether Bruce would be willing to make a premium build version of the LFT-8bs if offered enough money.  They are an absolute steal at the $2500 price point.  Although I think he may have raised prices a bit recently.

@sandpat: Yup, they’ve gone up to $3200/pr, plus a coupla hundred for a pair of the Sound Anchor base/stand. But that does include shipping within the Continental U.S.A., making them imo a better value than the $3000/pr Magnepan MG1.7i (I auditioned them both).

I’ve tried to install subs in a Mazda RX7 (rotary engine). It’s darn near impossible!