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


Back in June I initiated a thread bringing to your attention the LFT-8b loudspeaker from Eminent Technology, and the review of it by Steve Guttenberg. In that review Steve mentioned he would be getting the LFT option of a new woofer section, this one being of dipole design (the 8b woofer is a sealed monopole), the new model designated as the LFT-8c. Below is a link to Steve’s new review of it.

The LFT-8b remains available at a price of $3200 (including shipping within the States), the new LFT-8c selling for $4500 shipped. The 8c woofer system includes a power amp for the front-firing 8" and rear-firing 6.5" woofers, and DSP for planar-magnetic panel/woofer integration.

Not mentioned in this new review is that Guttenberg greatly preferred the LFT-8b to not only the Magnepan MG1.7i, but also the MG3.7i, which retails for almost three times the price of the ET. Steve found the 8c to be even better than the 8b, the dipole woofer blending with the LFT planar-magnetic panels better than did the 8b’s monopole woofer (Magnepan themselves is still working on their upcoming dipole woofer system).

However, he found the 8c woofer to be good down to only 40Hz or so. Hey, 8" and 6.5" woofers can do only so much! And he didn’t like the sound of the DSP when engaged. The $1300 price-differential between the 8b and 8c may be justified, but there is another option:

Any dipole woofer system can be used in place of the 8b’s monopole woofer, it needn’t be the 8c system. A great alternative is the OB/Dipole Sub offered by Rythmik Audio in collaboration with GR Research. This woofer system consists of two (or three, your choice) 12" woofers mounted in a dipole "frame", powered by a Rythmik Audio plate amp (which also contains a dipole-cancellation compensation circuit). The only catch is that the woofer system is offered only in kit form, the user being required to mount the woofers in the frame. GR Research offers just such a frame in both DIY flatpack form and assembled (and even finished, if you wish). This woofer system offers bass reproduction of the bottom octave, with the same superior integration with the m-p panels as that of the 8c’s dipole woofer. The Rythmik Audio plate amp includes all the controls necessary for optimum blending of the panels to woofers, including a continuously-variable 0-180 phase control.

The combined price of the LFT-8b and Rythmik/GRR dipole wooer is still far below that of the MG3.7i, and imo is an outrageous bargain in today’s high end world of loudspeakers. Steve once again mentions he doesn’t like electrostatic loudspeakers, but finds the sound of the LFT-8b and 8c to match ESL’s in transparency, while beating them in dynamics and tonal density.


Post removed 

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.😆

While Guttenberg's reviews of 8b and 8c are both positive, I feel he did not review the  8c quite as it was intended. He dismissed the DSP function of the speaker, saying it did not sound as good. However, the DSP is an integral part of the 8c. The entire signal chain goes through a A-D and D-A conversion, so that one is able to adjust the low pass level as well as time align the high pass signal. The speaker is preset with a -14.5db on the bass and a 0.6ms delay between the panel and the woofer. Both these functions allow the speakers to integrate better with the listening room, provide a much more coherent soundstage with better image depth and width, and a better integrated bass response. 

I know there are those who say they can hear a DSP in the signal chain and dislike it. Just like there are those who claim they can hear a step-up transformer in the vinyl signal chain and dislike it. But with the 8c, it is through the 'digitization' of the signal chain that certain sonic defects could be remedied. I just wished Steve could have made a little more effort in discussing the 8c with and without DSP. 

If it were an issue of more and better bass, than @bdp24 's comment on the Rythmik / GR Research open baffle sub-woofer must be a great solution. But even the Sanders system uses an integrated DSP solution to the design. I just wish the DSP design methodology could be discussed more insightfully. I asked Bruce about the use of DSP in an email. And he claimed that DSP technology has advanced so much  that he can use it to do things that were just impossible a decade before. And given the advancement, he felt that DSP is the lesser of two evils, the other being a passive  crossover design.  

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.😉

I remember going to a previous Axpona show where they did a demo of an unreleased speaker in the 6K range that sounded very good. Does anyone know that model number and when that is being released?

There are many paths up the mountain of good sound. If I had an 8B I would upgrade all the jacks and xover parts and wires with the best stuff (including 12 gauge wax foil coils that are cryoed and used in the best sounding direction.....going into the inside of the coil and out the outside). This would take them to a level that practically no one has ever heard. Then I would disconnect the woofer and on a separate flat open well braced baffle would mount either two Lii Audio or Acoustic Elegance 12 inch woofers and use a separate amp that has full eq to extend the woofs down to 20 hz and also get rid of all room nodes. I had the GR research servo woofs and they do not play above 150 hz even with the highest xover point. I always had a hole between the woofs and my planar speaker (heard and measured). Also you cannot equalize the bass with the servo system. I would use something like a Crown XTi 2002 to biamp. You run the mids and highs from your great normal amp and the woofs get their own amp with they are driven directly with no coils.

You could also wait till next year when ET might bring out a speaker using the new 90db panels (not the two boxer he showed in Florida). This would need to have new woofers and bigger box on bottom to match. Also, I suggested to Bruce that he sell the new 90db drivers on the panel by itself.....with no us DIY people can make our own super xover and bi-amp as described above. We will see what he does.

Here are some more ways to get tricked out planar sound:

Put two 12 inch woofs on an open baffle and above it mount 4 of the 8 inch planar drivers from Parts Express ($60 each...or optionally, use the way more expnsive Radian Planars) you have a 32 inch line source of planar drivers running from 300hz on up (high 90s sensitivity). You get the Minidsp Flex pure digital version...xover ($500) and make a super power supply for it.....and get two modified pure digital amps (VTV D300 or Peachtree GaN1) and use a stereo amp per channel mounted right behind the speaker. All xover and eq and delays done via the minidsp. This system would have no preamp, no DAC and no analog interconnects.....just some coax digital cables and very short speaker wires that are connected from the amps directly to the speaker drivers......this whole system with out streamer would be around $8-9K.....for everything including the wood for the baffle. Would be killer. Think about it.....No DAC, Preamp, analog cables, no long speaker wires. Xover and eq done totally in the digital domain......pure digital amps.....two state of the art 12 inch woofers per side and 4 highly efficient planars per side.....all perfectly equalized and time aligned for your listening position........

If you want to stay with analog class D or class A or whatever then you can get the new Danville dspNexus xover and bi or tri amp with it. Check out what Richard is doing at Hollis Audio Lab. He just showed a stack of 3 servo woofs and the mid/highs were a single planar 10 inch driver from Radian mounted on a small open baffle. He is now experimenting with adding a small tweeter to give better dispersion (tri-amping). Please check out his forum on Audio Circle. He has helped one person with ET speakers to use the Danville xover with 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.

@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!

There is no death......there is nothing to fear.

Here is a SUPER SIMPLE serious speaker. Buy a pair of the Lii Audio Platinum 10 inch full range drivers ($2200) and mount them on a four foot by 2 foot piece of multiply damped baffle and have four foot by 2 foot wings on the sides going back. Now you have a full range open baffle speaker that costs around $2500 for the drivers and wood and is 100 db efficient and when properly burned in and wired directly from your amp to the voice coil wires.....will sound incredible....You should get close to 40 hz in room with no eq. You could build a test baffle in one afternoon and start enjoying them while they burn in. My friend has the Silver 10s mounted on the above mentioned open baffle and he gets 40 hz flat in his room. He did mount an AMT on top with a copper foil cap to make it even better. His drivers are $1200. He goes to shows and the only thing he likes better at a show than what he has are the expensive silver Supreme Borresen speakers driven with 100K worth of stuff. He uses a tube amp he built himself. Plenty ways up the mountain of great sound.

You might want to check out the wild horn loaded cabinet that Decware designed for the Platinum speaker driver. There are sound bites on You tube. He does not wire directly to the voice coil wires.....he uses the junk binding posts on the speaker and probably another binding post on the front of the speaker (not good...he is not much of a tweaker). But his cabinet is way cool.

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.

Here is a SUPER SIMPLE serious speaker. Buy a pair of the Lii Audio Platinum 10 inch full range drivers ($2200) and mount them on a four foot by 2 foot piece of multiply damped baffle and have four foot by 2 foot wings on the sides going back. Now you have a full range open baffle speaker that costs around $2500 for the drivers and wood and is 100 db efficient and when properly burned in and wired directly from your amp to the voice coil wires.....will sound incredible...

@ricevs I bought of pair of Lii Audio's that someone else built with baltic birch plywood...without the baffle step filter network he had built with Dayton parts, I didn't like them. They were too shouty when connected directly to the amp. With the filter they were better...but ultimately I sold them and replaced with Tekton Lore...which I am quite fond of. I have a long history with single driver designs and on some recordings, they are remarkable....but I am now of the opinion that they need filtering for the rising response or DSP to handle it.

When Stereophile reviewed the original version it was kind of a disaster...John Atkinson is normally pretty nice about poor measuring speakers but this one just looked broken. A lot of time has passed and my question for Eminent would be how they addressed the super rough response, ringing, and rough spectral decay.

@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.

John Atkinson knows how to measure a dipole...but I agree an average Joe would struggle to get the best possible measurement just like they would struggle to get the room and placement just right for that tiny sweet spot...reviewer gatekeeping is pretty severe with family owned hi-fi brands & really anything high end like Wilson/'s smart business.  

Magnepan measures poorly due to things like phase cancellation and a first order appears some Eminent speakers do the same and the top model uses DSP for some frequencies...but higher frequency beaming with planar designs can't be fixed.        

There are people that rip out the Magnepan filter & replace it with a DSP crossover to presumably level the response and time align the tweeter and great satisfaction based on self-reporting....but to each their own.

This is not to say that one cannot love a speaker that has a highly uneven frequency response and ringing. Zu Audio would not exist if people didn't like what it did...including it's editorialization of the response and masking other frequencies.

Regarding Corey Greenberg, he did note a lack of coherence between the mid and bass panel. Steve Guttenberg noted the same. However, Steve Guttenberg noted an improvement in coherence with the DSP version...not surprising....but then he did mention he didn't like how the DSP changed the sound so he turned DSP who knows...I have heard DSP sound terrible and I have heard DSP that is transparent...all about implementation and the technology used of course.  



My friend has the Lii Audio silver 10s ($1200 the pair) and he says they measure and sound very flat (no lowther shout). You need to seriously burn these drivers in and you CANNOT listen to their binding posts.....remove the binding posts and hardwire your speaker wire to the voice coil wire....its like a completely different speaker.

Of course, the latest 8b would sound and measure way better than the original 8......but modding the heck out of them brings them to another whole level.

Here is another variety of what I described above about getting planar sound on the cheap.  You get a Minidsp Flex (analog version)......use a Fossi amp for the woofs and an Aegir or other inxpensive tube amp or class D amp (another $100 Fossi, for instance)......You use 2 12 inch Beyma 12BR70 woofs ($160 each) on an open baffle and above it you mount 4 Parts express $60 planar drivers in series parallel (woofs in parallel).  WE are talking 94db woofs and 94db line source here!!!  The mini dsp is the xover, the preamp and the DAC all in one.  With both 12 inch woofs being directly driven by an amp and with no inductors in series and with equalization, the bass would kill, (I mean slaughter) the ET speaker.  You cross over around 400 hz to the mini line array planars and you will have sound so good you would die.  You run your wires directly from the two amps to the drivers (voice coil wires on woofs).  The minidsp ($500), wood ($300), wire ($300), 4 woofs ($700) and 8 planars ($550) would be around.$2500 with whatever amps you want (you probably already have an amp for the highs.....some or you have another amp laying around for the bass.  I would lake this anyday over a stock 83db sensitive 8B.  Of course, as I mentioned above a fully tweaked 8b with open baffle bi-amped speaker would be probably better (better planars?).  Alternatively, you could use one 10 inch planar driver from Radian ($660 a pair).....these might be more transparent than the Parts express planars but probably have less horizontal dispersion and way less vertical dispersion.  (If you sit in one spot then the Radians might be the ticket).

@ricevs I'm sure that would be amazing if you were able to get the filters right in the mini DSP. 

Regarding Lii Audio I still wouldn't connect amp directly to driver without passive filter or DSP for baffle step correction...there is no getting around the rising response...having said that, some people love a rising response for the extra presence it brings...just not me.  

What do you mean "if you get the filters right"  Using a DSP is easy....a 10 year old can do it.  You decide what slope you want and what frequency (I would start with 400hz and 24db per octave with the mentioned drivers) and then you measure the adjust the amp levels and equalize and time align.....can be done in an hour by anyone with a measurement mic and a brain.  Of course, you can play with different xover frequencies and slopes (and fine tune the tweeter delay...mostly by ear).  Always fun to play.  But hard? way.   

Which Lii driver did you have?  They are all different.  As I said, my friend measured his Silver 10 (burned in for hundreds of hours and wired directly to voice coil wire) and it measured flat and sounded that way.....measured way flatter than the spec measurement from Lii.

@ricevs Lii 15 

I don't really want to start an argument but a single driver design playing wideband with no filtering can't measure flat. I wish this wasn't a truth, but it is. 

Regarding DSP, I agree easy to play with....