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.....


Yep, there it is. By the way, the recommendation of an aluminum wrench is a REAL good one. The magnets in the LFT drivers exert a pretty strong pull on ferrous materials (steel)!

@bdp24, yes...nothing like having a tool yanked from your hand. 😬

Brass wrenches are better, but mind the alloy and test cheap. *l*

Agreed, a nude Maggie isn't cute by no means and I'll give the 8's a nod for at least looking 'business-like' about being sans grilles... ;)
Some of us don't mind facing nudes..😏

I have my Heils...I know a good ribbon or planar when I stumble into them.
I'd give the 8s' my time. *S*

We have a pair of LFT-8b speakers, and the sound is wonderful. Very detailed, great separation and frequency integration, though we do use them with subwoofers for extended bass.

I have to agree that the finish is not as high as many expensive speakers. I think Bruce found a way to manufacture excellent sounding speakers at a truly low price compared to others, and the tradeoff is that while these are hand-made in the US, he uses pretty common materials - steel plate, steel channels, neodymium magnets, and mylar with printed aluminum. Yes, I agree the woofer boxes could be supplied with threaded inserts, and the wood trim could be more impressive.

However, the sound is quite amazing, and very satisfying. We can listen all day with no fatigue, and the speakers handle a wide range of music and volumes. These replaced MTM/subwoofer box speakers with Seas Excel drivers that sounded great.

We also have an ET-2 tonearm on our Oracle turntable, and while it is fussy to set up, and I wouldn’t recommend it to someone who isn’t technically competent so they can do their own adjustments from time to time if needed, we have overcome most of the challenges with the tonearm, including installing the air pump in a sound-isolated cabinet a few feet away from the turntable. It also has the damping trough which really enhances the sound and performance.

One challenge with the speakers is the midrange panels have to be adjusted properly, and the mylar can stretch over time. We had one speaker that gave me a lot of trouble with adjustment, but Bruce sent me a couple of additional hex adjusters, and finally, when the panel wouldn’t stay in adjustment (buzz at very specific mid-low frequencies at loud volume), Bruce sent me an entire replacement steel frame/panel with mid-range panel installed and adjusted, all under warranty. A week later, Bruce sent me replacement tweeter ribbons and fuses/fuse blocks (at no cost) because I had stupidly blown the tweeters by incorrectly connecting a new active crossover. Fortunately I have the tools and expertise to replace the ribbons myself rather than sending them in for replacement - and what I'll be doing later this morning.

What I’ve come to accept is that Eminent Technology makes true audiophile gear, but it can sometimes require maintenance skills that not all audiophiles have acquired. However,, Bruce goes out of his way to ensure that any problems are resolved. I’ll be ordering the new woofer/DSP upgrades tomorrow!