As he promised, Guttenberg reviews the Eminent Technology LFT-8c.

Several years ago one poster on the Planar Speaker Asylum (I believe it was) wrote about speaking with Thigpen regarding upgrading the LFT-8 x/o. Bruce was not-in-the-least offended, and in fact provided the LFT-8 owner with details on how to do just that. The schematic for the LFT-8 x/o is of course included in the speaker’s owner manual, as well as on the Eminent Technology website..

@ledoux1238: And it is members such as yourself that keeps me from abandoning Audiogon altogether.

In addition to the LFT-8, we also have in common the Trans-Fi Terminator arm, mine mounted on a VPI Aries (with a TNT-5 platter). The Terminator is another hi-fi bargain. Over-performing (price-to-sound quality relationship) components is where the fun lies for me.

@ledoux1238: Thanks for the heads up, I’m gonna read it right now.

@deep_333: I didn’t have the @vonhelmholtz enquiry removed. Why do you assume I did? And your implication regarding me "rewarding" Thigpen (rather than merely wanting to bring the ET LFT-8 to the attention of Audiogon members) is a perfect example of one reason I am no longer interested in participating on Audiogon.

@seanheis1: Though reviewer Corey Greenberg loved the LFT-8 ("These are MIGHTY fine speakers, rivaling many well-known models at considerably higher prices. In terms of detail and midrange clarity, they are some of the most impressive speakers I’ve heard at ANY price. The LFT-8’s gave the impression of a very fast, natural-sounding speaker."), John Atkinson’s measurements of it were indeed pretty bad. Measuring a dipole planar loudspeaker is fraught with peril, the measurements not at all correlating with the sound the speaker produces. That’s why Magnepan doesn’t send out their speakers for review.

Something to be aware of: The LFT-8 Greenberg received for reviewed was the original version. Partway trough his evaluation, Bruce Thigpen send him a revised planar panel, which had it’s ribbon tweeter moved from the top of the panel to its’ middle. The LFT-8 then later had three other revisions made---a different woofer, tweeter, and cross-over. With one of the revisions came the 8a nomenclature, another the 8b.

Ric is serious about cabinets. When he was building speakers using the BG NEO drivers and Rythmik/GR Research 12" woofers mounted on an open baffle, he made the baffle with 3 layers of MDF, Green Glue between layers.

I made my open baffle (W-frames for the OB/Dipole Subs) and sealed enclosures (for the 15" woofers) using one layer of MDF and one of Baltic Birch, with a layer of ASC Wall Damp between them. I braced the sealed enclosures with strips of Baltic Birch (two pieces of 3/4" x 1.5" glued together to make a 1.5" x 1.5" brace), one every 6" in all three planes (front-to-back, top-to-bottom, and left-to-right). Very stiff and non-resonant. With the Rythmik Audio servo-feedback woofers installed, I get the best bass reproduction I’ve ever had.

I had originally designed enclosures as per Danny Richie’s idea of doing a double-walled box, with a 1/2" space between the two boxes into which sand is poured. But with the serious bracing and the resulting size of the 4cu.ft. enclosures being 24" H x 18" W x 24" D (those braces eat up a lot of internal volume), I decided to use the Wall Damp means of absorbing wall vibration (the frequency of which---due to the bracing---is way above those the woofer is reproducing) instead. Using two different forms of wood---with different resonance characteristics---is another way to combat enclosure wall resonance.

I don’t have a table saw, so I hired a woodworker to cut all the wood for me, working off the diagrams I supplied him. He also had a CNC machine, so the cuts are very clean. The internal MDF walls are glued together, the outer BB walls (cut to size on top of the inner walls by myself with a router) just finished with clear lacquer. Looks European! I left a 1" space in the front of each H-frame and sealed enclosure for inset grills, like speakers had in the 1960’s.

I say all this to make the point that building the Rythmik Audio/GR Research OB/Dipole Sub---or even a GR Research or other brand DIY loudspeaker---is not beyond the abilities of younger audiophiles (no offense, fellow gray-hairs ;-). For the older or mechanically-challenged fellas, Danny Richie offers flat pack kits---and even fully-assembled enclosures and I believe completely finished speakers---via some woodworkers who collaborate with Danny, so it’s a path to champagne sound quality at beer prices worth considering.

But for a plug & play loudspeaker, can the Eminent Technology LFT-8b or 8c be beaten at its’ selling price? If your taste runs to dipole planar loudspeakers, I don’t think so.

@peter_s: Very well. In fact, since the LFT-8b has limited response below 40Hz or so, it is an excellent candidate for add-on subs. And since the response of the woofer at 40Hz and above is unusually "fast"-sounding, it blends well with subs. I myself use a pair of Rythmik Audio F15HP subs (I bought the kit version, building my own 4cu.ft. enclosures), using them crossed over at 40Hz. I also built a pair of the Rythmik Audio/GR Research OB/Dipole Subs to use in place of the LFT-8b’s woofers, but that’s a story for another time.😉

The LFT-8b---having a sealed dynamic woofer for reproduction of frequencies 180Hz and lower---doesn’t suffer from the dipole cancellation found in full-range dipoles (such as Maggies). But an 8" dynamic woofer in a sealed enclosure---even one of the quality of that employed in the LFT-8b---can do only so much. Since the LFT-8b woofer is a monopole, there will be no discontinuity between it and a sub swarm also of monopole design.

Bruce Thigpen intentionally uses a higher-than-normal-mass woofer in the 8b (he in fact mass loads the driver), sacrificing the ability to play above 180Hz in exchange for better performance below that low crossover frequency. The LFT (Linear Field Transducer, invented and patented by Thigpen) magnetic-planar driver reproduces 180Hz up to 10kHz, with no crossover in that frequency band! That’s one major reason for the 8b’s unusually-high sound quality. Another is the LFT driver being of push-pull design (magnets on both sides of the Mylar diaphragm), in contrast to the single-ended Maggies such as the MG1.7i.

$3200 for the sound quality provided by the LFT-8b? You have to hear it to believe it!

Damn Ric, you’re gonna scare off potential LFT-8b/c buyers!

Sure, an outright fanatic like Ric Schultz can concoct a Frankenstein LFT loudspeaker, but most audiophiles (including those reading this thread) are looking for a plug & play loudspeaker, not a complicated project. Heck, even building the Rythmik Audio/GR Research OB/Dipole Subwoofer is beyond the interest and/or capabilities of your "normal" audiophile. I found it to be relatively easy, and I’m no master cabinet builder.

The recommendation of the Eminent Technology LFT-8b/c was suggested as an alternative to the far more commonly known Magnepan planar-magnetic loudspeakers. In the opinion of myself and Steve Guttenberg, the LFT-8b is superior to the Maggies, only slightly higher in price to the clearly-inferior MG1.7i (I compared the two), and less than 1/2 the price of the MG3.7i. The 3.7i I have not heard, Steve has. Make of that what you will.

Good points you raise @ledoux1238. I admit to having reservations about digitizing all signals passing through the DSP of the 8c (and the Sanders version of same). I accept the assertion that digital technology has improved to the point of it being as close to complete transparency as is much of analogue, but still, why do it if you don’t have to?

One thing to know is that the 0-180 degree phase control (which provides from zero to 16ms of delay), gain control, damping control (high/low/medium), extension filter (14Hz/20Hz/28HZ), and crossover frequency (up to 300Hz!) and slope (1st/2nd/4th order) controls (amongst others) included in the Rythmik Audio plate amp make possible the integration of the LFT-8 panels and OB/Dipole Sub just as well as does the DSP unit. In addition, the OB/Dipole Sub features Brian Ding’s Direct Servo Feedback control of the 12" woofers, which also provide full output down to slightly below 20Hz, over an octave lower than the LFT-8 b and c woofers.

At any rate, both the b and c version of the LFT-8 really deserve to be more widely known by audiophiles interested in planar-magnetic dipole loudspeakers. Why on Earth it took Guttenberg 33 years to get around to hearing them is what I would like to know! Everyone knows about Maggies, while the Eminent Technology LFT-8 remains virtually unknown. Bruce Thigpen may prefer to keep Eminent Technology at a manageable size, but sending a few pair of LFT-8c’s out for review by print mags may provide him with a better eventual retirement.😉

The now-deleted post was from @vonhelmholtz, asking "Are you a dealer, or a representative of ET?" No offense taken, that’s a fair question.

The answer is nope, just a very satisfied ET LFT-8b owner, doing what I can to help reward the outstanding work of ET designer Bruce Thigpen, and direct magnetic-planar loudspeaker fans to what I consider the best value in that type design.

I’ve owned three pair of Maggies, one currently (Tympani T-IVa), and very well understand their appeal and widespread popularity. But imo the LFT-8 is THE magnetic-planar loudspeaker to own.

I am also a past owner of a pair of Infinity RS-1b, and imo the LFT-8 also bests that loudspeaker. The LFT-8 is good enough to have made me retire my Quad ESL’s, which was for many years my loudspeaker of choice, weaknesses and all.

I would still love a pair of SoundLab ESL’s, or even a pair Sanders. But the LFT-8 will do quite well for now.😆