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Eminent Technology LFT-8c Robert Greene review

A friend of mine forwarded this review to me a couple days ago.  I hadn't seen it as it's just a week old at this point. 

Why would I be interested? I have a pair of LFT-8b speakers that I picked up about 7 months ago.  Wonderful speakers. I always wanted to try a set of panels and, as luck would have it, last summer I found a used pair of 8b's just a short drive from my home..I made the jump.  As it turns out, this was one of the best moves I've made in my 50+ year audio hobby. 

In the last few months, I was considering picking up the 8b to 8c upgrade components, but put it off as I had a number of other projects going on.  Well..the projects got completed and I started a few more projects, though this time around the 8c upgrade is one of them.  I ordered the 8c upgrade yesterday and I'm really looking forward to the adventure once it arrives. 

One thing I've noticed when reading discussions of the LFT-8(no a, b, c)  here on A-gon, is the discussion wanders over the now 36 year history of the LFT-8.  Issues identified in this or that review from 10-20-25 years ago are brought up as if they reflect what the LFT-8 is today.  LFT-8's had a great sound 30 years ago, with a few flaws, as any 30 year old speaker would, and it sounds better today. Nothing surprising there. Most companies cut ties with models as they age and come out with something new, whether they are really new or repackaged parts..that varies.. 

What's my point?  I just find it interesting that Bruce Thigpen (Eminent Technology) came out with the LFT-8 in about 1990 and has been continually improving the model 8 year after year, decade in and decade out, staying in business with no advertising, though with a few shows here and there. There are very few current speakers(let alone businesses) alive today that have a 30+ year history under largely the same name. (Though the Vandy 2 series comes to mind)  Pretty unique in this industry.  It's also pretty unique that a decades old pair of LFT-8 speakers can be upgraded to the current model at a very modest cost. And the upgrade is easily done by any owner. 

So..the latest review:

https://www.theabsolutesound.com/articles/eminent-technology-lft-8c-planar-loudspeaker/

Robert Greene goes into considerable depth in his review, which is specific to the 8c version, though he's done an 8b review in the past. I'm glad it came out as it pushed me over the edge in ordering the 8c upgrade.  I'm not getting any younger..time to give the 8c a spin. 

One last note, I've read in a number of older and current reviews that the LFT-8 speaker placement is..finicky.  I haven't found that to be the case at all.  In the last 7 months I've experimented extensively with placement and they respond well to various setups. My current setup is about 115 inches between the panels (on center) and maybe 30 degrees toe-ed  in from facing directly forward.  Each speaker is 45 inches off the front wall(on center) and 38 inches from the side walls.  I have a great soundstage and and equally great imaging.  My tweeter panels are on the inside. 

 

(...and no..I have no affiliation with ET..just a customer owning a used pair of the 2017 model 8b)

nogaps
bdp24's avatar
bdp24
10,487 posts
 

 

@audibleguy:

The only guy I’m aware of who did double LFT-8’s was Schneider. He placed them side-by-side, which is ill-advised, for a technical reason:

Two drivers reproducing the same frequency need to be close enough to each other to not produce comb-filtering---peaks or holes in the frequency response of the speaker as a result of the phase relationship between the two drivers. Danny Richie of GR Research has made a few videos (viewable on YouTube) explaining phase relationships between drivers and comb-filtering.

The midrange driver of the LFT-8b reproduces 180Hz up to 10kHz. The wavelength of 10kHz is 3.43 centimeters (1.35 inches). 5kHz is 6.86 cm (2.7 inches), 2kHz is 17 cm (6.75 inches), 1kHz 34.3 cm (13.5 inches). If the distance between two drivers reproducing the same frequency (as does the LFT-8b midrange driver when a pair are placed by-by-side) is greater than the wavelength they are reproducing, the result is comb-filtering.

Consider the distance between the two "midrange" drivers of the LFT-8b when placed side-by-side. Far greater than 1.35 inches (10kHz), 2.7 inches (5kHz), 6.75 inches (2kHz) and even 13.5 inches (1kHz). The situation for a pair of side-by-side LFT-8b tweeters is even worse.

The only good way to use double LFT-8b’s is with one atop the other: stacked two high. Even then the tweeters (with a x/o frequency of 10kHz, using a 1st-order filter) will be too far apart to not cause comb-filtering, in this case in the vertical plane (side-by side is in the horizontal plane). The tweeter in one of the two LFT-8’s should be disconnected. Two LFT-8’s stacked is 10 feet tall! And I don’t know how you would support the woofer enclosure of the top speaker!!

IMO not a practical idea. A single pair of Magnepan MG3.7i’s might be a better choice. My choice is of course a single pair of LFT-8b’s with the fantastic Rythmik/GR Research OB/Dipole Sub (either the 2-woofer version, the triple, or even stacked doubles). Disconnect the 8’s stock woofer, and remove frequencies below 180Hz from the signal sent to the planar panels, which will lower the amount of distortion your power amp creates, and leave it with more power available for the LFT-8 panels. 

 

 

ledoux1238
421 posts
 

Enjoy the Music.com just reposted a LFT-8c review which first appeared in 2024. 

 

Regarding Eminent Technology's new speakers, Bruce did not confirm that they would be the 18SL. He did say that they would be in the 20K range. 

bdp24's avatar
bdp24
10,487 posts
 

 

Great @ledoux1238, thanks.

 

ledoux1238
421 posts
 

The Enjoy the Music.com review of the LFT 8c  by Jules Coleman was conducted with the ribbon tweeters placed on the outside edges. I had assumed that the issue of tweeter placement, on the inside edge of the speaker, was established knowledge. For the many years of ownership of the LFT8b / c, I have placed the tweeters on the inside edges. Well, after re-reading the article, I decided to reverse the tweeters placement to the outside edges. My room is about 11’ wide by 33’ deep. The edges of  speakers are placed 10” from side wall with no toe-in. And I much prefer the tweeters on the outside! The soundstage  has a better sense of air around the instruments. It is not as wide on most recordings, which makes sense with the mid-range panels closer together. And perhaps because of this, the soundstage is denser, most robust, and somehow depth is increased. Overall, it is a better presentation in my room, a nice discovery!

bdp24's avatar
bdp24
10,487 posts
 

 

@ledoux1238:

Another factor to keep in mind is the fact that when the midrange drivers are repositioned, the speaker/room interaction is changed. And with no toe-in, the phase relationship between midrange driver and tweeter is as well. An easy way to experiment with midrange/tweeter phase orientation is with varying degrees of speaker toe-in.

Another is that with the width of the LFT-8 midrange driver being 4", horizontal beaming of that driver starts at a relatively low frequency, the beaming of course increasing as the frequency increases. The low-pass filter of the LFT driver is 1st-order at 10kHz, where beaming is at it’s most severe. With the LFT-8 midrange driver on the inside, you are getting less driver output loss due to beaming (even at midrange frequencies, far below 10kHz) compared with that driver on the outside (where the listening position is further off axis).

 

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