Eminent Technology LFT-8b in Harry's system

Thanks again Bruce. Say, where inside the woofer bin is the x/o located? I haven't removed a woofer to have a look inside, though I have the parts for the "Davey" mod (to remove the woofer's resonance in the 1200-1500Hz range), just a cap and resistor.

I am also considering moving the x/o to the top of the woofer bin, right behind the LFT panel. Shorter runs of wire (maybe silver) soldered onto the driver terminals, eliminating the stock spade connectors.

Yup, ESL’s are IT for transparency imo. I have QUAD ESL’s, Stax phones, and a pair of ESS Transtatic’s with three of the RTR ESL tweeters, I’ve heard the big Soundlabs, and had I the requisite space and funds would have a pair of them too!

The impedance modulus of the LFT-8b is a good point to bring up. Thigpen says he could give the speaker any impedance he wanted, and chose 8 ohms. The LFT panels themselves are 11 ohms (and mostly resistive in nature), and may be bi-amped separately from the woofer (two sets of binding posts are provided).

The earlier full-range LFT models (LFT 3, 4---which I also own, and 6) are 4 ohms, like Maggies. The 3 and 6 are bi-ampable (at 400Hz, I believe), so a tube amp could be used with a big ss amp for the bass.

The LFT driver is much more robustly-built than the somewhat-garage-ish construction of the Maggies. The substantial metal driver frame is bolted into a cutout in the solid oak speaker baffle, whereas the Maggies have no metal driver frame, the Mylar being merely glued (and stapled?) onto the MDF (yuck) frames. The LFT is also a push-pull design, one reason listeners find it to be a very low distortion-sounding design, closer in sound to an ESL than to the Maggies.

Scot, I went through a similar learning curve back in the mid-70’s. I bought a pair of Magneplanar Tympani T-I’s in ’73, but grew dissatisfied by their slightly opaque lack of transparency and missing bottom octave. In ’74 I replaced them with a pair of Fulton Model J’s, which cured both problems (the J’s had an array of six of the great RTR ESL tweeter, and a transmissionline-loaded woofer that went pretty deep). But I soon missed the qualities large planar loudspeakers excel at, and sold the Fultons, forever after a diehard planar lover and owner.

People continue to ignore the LFT-8, buying Maggies instead. I have nothing against them (I currently own a pair of Tympani T-IVa’s, though I don’t have a room big enough to use them), but compare the LFT-8b to the MG1.7i; if you have already bought a pair of 1.7’s, you’ll wish you hadn’t ;-). The problem is, ET doesn’t have many dealers, so one can’t easily audition them. Luckily, Brooks Berdan Ltd. had a pair (Brooks was a big fan of ET and Bruce Thigpen), where I heard them. ET has a money-back offer on the LFT-8, with I believe a 30-day audition period. I suppose the consumer has to pay the shipping, but to hear the LFT it might be worth it. Consumers without a dealer within 150 miles can buy factory-direct, at list price.

The Rythmik A370 plate amp (the amp in the OB/Dipole Sub) is no ordinary amp. It is a well designed 370 watt class A/B analog amp, controlling the dual 12" woofers in a servo-feedback circuit. The front-to-back cancellation inherent in dipoles is counteracted with a 6dB/octave shelving circuit, providing response to below 20Hz at sufficient SPL for most music. The dipole operation of the sub works particularly well with dipole speakers for the obvious reason, as well as exciting one less room mode than monopole subs.

Clio, if you ever see an Electron Kinetics Eagle 2 amp at a reasonable price (less than $500 or so), consider getting it for your 8" woofers. It is a KILLER bass amp!

The low price of the LFT-8b works against it in the mind of audiophiles who equate price with quality and performance. But it’s more than just that; far more people own Magnepan MG1.7’s than LFT-8b’s (approximately the same price after Mye and Sound Anchor stands, respectively, are bought for each), many of them not even knowing of Eminent Technology. That’s a result of ET having far fewer dealers than Magnepan, and getting far fewer reviews. I believe many 1.7 owners, had they heard the Magnepans and ET’s side-by-side, would have instead purchased the ET’s. But ET exists like a cult-level band, known only by the hippest music lovers. Flying under the radar, so to speak.

The same is true of Music Reference (the RM nkj refers to directly above is Roger Modjeski, designer/builder/owner of Music Reference products. Roger designed the direct-drive tube amps for the Beveridge ESL’s, and now makes his own direct-drive tube amp/ESL loudspeaker with sub system, available for $12,000/pr). Roger is very much like Eminent Technology’s Bruce Thigpen, designing and making products offering ridiculous value, yet owned by far fewer audiophiles than those of more "trendy" companies, ownership of which carries with it more audiophile cache’ and bragging rights.

How many have compared an RM-9 or RM-200 against an ARC, Conrad-Johnson, Quicksilver, Jadis, VTL, Manley, Shindo, Cary, Lamm, Ypsilon, McIntosh, Allnic, etc. amp? Aside from Brooks Berdan, only Michael Fremer, as far as I know. Brooks had sold ARC when he was at GNP Audio, and chose VTL, Jadis, McIntosh, and, yes, Music Reference as his tube brands (along with a few others) when he opened his own shop. It was he who turned me on to both Eminent Technology and Music Reference, two of his favorite companies and product lines. Wise man.

Wow, a new pair of LFT-6’s! I’m gonna look into that.

Bruce includes a chart of the LFT-8’s impedance curve in both the owners manual and on the ET site, and the inductance of the dynamic woofer does cause an impedance dip. But the panels themselves have a very even, and for magnetic-planar and ribbon drivers, very high impedance characteristic, making them a good candidate for bi-amping and tube amplification, if that’s what one desires. Maggies, in contrast, present a 4 ohm and lower load to the amp, a real challenge for a tube design. The lifespan of tubes is greatly shortened when asked to drive low impedance loads, inefficient ones even more so.

Another point worth mentioning is that some consider the LFT-8’s dynamic woofer, though optimized for and blending well with the panels, to be the speaker’s weak point. If one desires more (or "better") bass output capability, the rather low 180Hz x/o frequency between panel and woofer allows one to use a sub of one’s choosing in it’s place. I am about to try just that with the bass panels of a pair of Magneplanar Tympani-IVa’s, an idea I became aware of recently on the Planar Speaker Asylum Forum.. Should be interesting

kot, I tried for quite a while to find a pair of the LFT-6’s, but never did. I had to settle for the LFT-4, which it's sort of a half-size version of the 6. It’s great for smaller rooms, as long as one has the usual distance from the wall behind the speaker than dipoles require---3’ minimum, 5’ better.

The LFT-8b is a great candidate for bi-amping (or at least bi-wiring), and ET makes it easy. There are two pair of binding posts on the top of the woofer box, one for the woofer and one for the magnetic-planar midrange & ribbon tweeter drivers. The x/o is 1st order (6dB/octave), so one can bi-amp passively---it’s cheap! Vertical bi-amping with identical amps helps with that, as their input sensitivities are matched. Or, a moderately powered tube amp can drive the panels, and a ss the woofer. The LFT has a nominal impedance of 8 ohms, but the panel itself is 11-12 ohms, great for tubes.

I second kot's recommendation of the Electron Kinetics Eagle 2A, one of which I own. A great, great amp for bass in particular. I haven't heard the updated/modified version kot cites, but even the original is fantastic, a real classic.

A new review from Harry arrived today---HW Review #2 (07-03-2017). The subject of the review is the Modwright 150 Phono Section, but here a couple of quotes from the review regarding one of the speakers Harry listened to the Modwright through---yes, the Eminent Technology LFT-8b:

"A $2500 wonder."

"I typically find the ET's to have the best mid-range I have ever heard from any speaker."

The other speakers mentioned in the review are KEF Blade 2, JBL Everest, and Joseph Audio Pearl 3.

No apology necessary Lew! To assume ignorance is not a bad idea ;-).

Modjeski’s new ESL is sold as an integrated speaker/direct-drive tube amp---no output transformer in the amp, no step-up transformer in the ESL. A stand-alone direct-drive amp is impossible, as a universal model/design can’t take into consideration the different nature/characteristics/needs of all the speakers it may be asked to drive. A direct-drive amp must be designed for a specific speaker, and for that speaker alone. I’ll bet the Beveridge was Roger’s first attempt at such a design, and I wonder how his new one differs from it. He did also design a "normal" OTL, the rights to which he sold to Counterpoint, who manufactured and marketed it as the SA-4.

Your KEF driver project was very advanced for a hobbiest, Lew. Transmissionlines are not easy to build, requiring a lot of knowledge of acoustical theory, speaker enclosure design, and cabinet building. I’m impressed!

I know what an OTL is, ya big silly ;-). I had a pair of Atma-Sphere M60’s for years, which I bought for driving my old Quads. One cool thing about them is you can take out half the output tubes, to create a 30 watt version of the amp, perfect for the easily-overdriven Quads.

You’re right, an ESL speaker with a direct-drive tube amp has not only no output transformer in the amp, but no step-up transformer in the speaker, eliminating two sources of distortion. I know Modjeski’s current ESL speaker/D-D amp product is designed and built that way, as I believe the Beveridge was. I think it was to accomplish that that Mr. M was hired by Mr. B. I think they were both in the Santa Barbara area at that time, a beautiful city on the California/Pacific Ocean coast, just north of Los Angeles. Modjeski relocated to the San Francisco bay area a couple of years ago, where he runs Music Reference and teaches a course in amplifier design at a local adult education school. Wish I still lived in San Jose!

When I bought the TranStatics in ’81 (for $400, out of The Recycler, a weekly S. California paper), one of them had a generic oval woofer instead of a B139. I called ESS in Sacramento, and they had one, and only one, left. I paid all of 39 bucks for it! The B139 ESS used in the speaker wasn’t the standard version---not having the four "ears" through which mounting bolts pass---just a perfect oval. I first heard the speaker in ’71, but being a starving musician couldn’t come close to buying a pair. They retailed for $1200 in ’71, the Infinity Servo-Static $2000. Ten years later I was happy to find the TranStatics, and could now buy them. Still have 'em, but man are they heavy---140 lbs. apiece

Nice Lew! I'm a fan of the B139 (Dave Wilson is too, using a pair in each WAMM, for mid-bass), and I have a pair of ESS TranStatic I's that use it in a quarter-wave (I think it's called) transmissionline. The  midrange is covered by a KEF B110 5" Bextrene cone, the highs by a trio of those great RTR ESL tweeters, the same ones Bob Fulton used in his Model J. I had a pair of those in '74, for about six months.

I'm dying to hear Modjeski's current Direct-Drive ESL speakers, powered by tube amps of his with no output transformers---the amps driving the ESL's directly (hence their name ;-).

Ha! Hyperbole on my part Lew, obviously. But close to it (let's say 120dB @ 1Hz ;-), the Rotary Woofer not being constrained by physical excursion like mechanical transducers. A really fascinating, revolutionary, visionary creation from the mind of the brilliant Bruce Thigpen.

You have Beveridges, Lew? Another visionary product, with direct-drive amps for the ESL drivers designed by Roger Modjeski of Music Reference. I'm green with envy!

Good point about the LFT-8b maintaining it's resolution at lower level/volume. It's more like an ESL than a magnetic-planar in that regard. That Maggies need to be cranked to a certain level to fully "open up" is widely acknowledged, being somewhat veiled and opaque at low levels. That is another reason the LFT-8 is better for a smaller room than are the Maggies. I love Maggies too (my first high end speaker was the original Tympani-I, and I now own a pair of Tympani-IV's and IVa's), but they really need a bigger room than does the LFT-8b.

The fact that the LFT-8 has been in production for twenty-five years, and has had only two revisions---a change of the woofer and the tweeter, both retrofitable to the first LFT-8 ever made, and at nominal cost---speaks to the "correctness" of it's design. The recent Magnepan "i" revision can not be performed on the 1.7, which must be a real drag to owners of that fine speaker.

The LFT-8's magnetic-planar midrange driver, which as has already been stated covers the frequency range of 180Hz to 10kHz (without a x/o, the entire midrange and all but the top octave reproduced by a single driver!), has remained unchanged in all that time. As has the x/o and woofer box. The m-p driver and ribbon tweeter are bolted onto a metal frame, while the Maggie drivers are glued onto an MDF frame, which exhibits some flex and resonance, hence the need for the Mye stands. Big difference!

All the LFT-8 needs is the revolutionary Eminent Technology TRW-17 Rotary Woofer. Unlike the LFT-8, however, it ain't cheap!