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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.....

128x128bdp24
tomic601's avatar
tomic601
12,744 posts
 

Any of the powered bass biamplified Vandersteen models are flat in most rooms to the twenties, my 7’s with the patented Ti / aluminum push pull sub are -1 db at 20 in a decent sized room ( see Poverty Bay sound in my system photos ). My Treo w single Sub 3 are flat  into the high twenties…. and without using ANY of the available 11 bands of ANALOG eq….

EJ - you are welcome to visit any time… and as you have previously invited me, i really should get down to hear your Tympani - you know i am a fan….

Also, Bruce is his own genius… i dont think we can know his goals for ET ? Thankfully we have the speakers…. yes of course, i have heard them…they are very sweet, somebody looking for a planer, curved panel nit included would do WELL to audition them….

Best to all on our shared quest for better more emotional music reproduction 

Jim

tomic601's avatar
tomic601
12,744 posts
 

And i agree w genius and frustration w ET-2. I sold more than a few maddening Souther back in day and agree there as well. Thankfully we do have at disposal here on the forum an excellent thread on the ET-2 arm optimization / maintenance by many contributors…..

Peace

arion's avatar
arion
156 posts
 

@bdp24

During the development of our OB line arrays we researched and tried several types of woofers configurations and ultimately designed our own dipole woofer system. We came to the conclusion that dipole woofers complement OB speakers best, at least in our case. Our dipole woofers have been successfully used with several dipole panel speaker system. I call them woofers and not sub-woofers because they cover from 20Hz to 120Hz in our system and work very well up to 200Hz. 

arion's avatar
arion
156 posts
 

@bdp24

Sorry, hit the "post" button...

I suggest looking into dipole woofers to best compliment OB speakers, not necessarily ours because there are lower priced systems out there.

bdp24's avatar
bdp24 OP
9,408 posts
 

Not a problem @arion, at least for me. Yep, for dipole loudspeakers (of which most OB loudspeakers are) dipole woofers ARE are the way to go. And I complete agree with your calling drivers which reproduce "only" down to 20Hz woofers, not subwoofers. Separate enclosure with driver(s) became known as subwoofers because most "full" range loudspeakers are of course nothing of the sort. Since those speakers have woofers, what should the industry call a product which reproduces very-low frequencies, those below what the speaker's own woofers can't reproduce? Why subwoofers, of course!

@tomic601: Hey there Jim! Yep, I heard the Vandersteen subs many times over the years at Brooks Berdan Ltd., one of Richard's first and best dealers (he sold a LOT of Model's 2 and 3). When Brooks decided to not sell Richard's new higher-priced models (beginning with the Model 5, I believe) I knew he was making a big mistake. That was not acceptable to Richard, and Brooks was no longer a Vandersteen dealer. Brooks, you fool! ;-).

Brooks wanted to sell his customers (and potential customers) who were looking for higher-priced loudspeakers Wilsons, not Vandersteens. Why not offer your customers the choice of both? The more product you sell of one company, the better wholesale price you get, hence more profit. I sat in on a meeting Brooks took with Wilson's head of sales at CES, and witnessed how dealers are pressured to sell more product. It wasn't pretty.

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