Eminent Technology LFT-VIII Loudspeaker System

Manufacturer: Eminent Technology, 225 East Palmer Street, Tallahassee, FL 32314; 850/575-5655; E-mail: brucet@eminent-tech.com

Price: $1500 (pair)

Source: Manufacturer loan

Reviewer: Howard Ferstler

Eminent Technology has been in business for more than 20 years. Its owner, Bruce Thigpen, currently holds seven audio patents, including one for a vacuum device for clamping LP records, one involving an air-bearing tone arm, and several involving planar-magnetic transducer design. The ironic thing about Mr. Thigpen and his company is that it is located in my home town. I did not even realize that the enterprise was here until I discovered it while surfing speaker web sites for potential product reviews. Talk about a small world.

Bruce designed and built the first push-pull (as opposed to single-ended), full- range magnetic speaker that I know of, and his ribbon-driver patents have been licensed for manufacturing Level 9 Sound Designs, in Canada. That company supplies transducers for Monsoon speakers, as well as modified ribbons to VMPS. Bruceís own company builds planar/ribbon transducers for his Eminent Technology speakers, and does most of the work from scratch at the companyís manufacturing facility in Tallahassee.

An earlier manifestation of the LFT-VIII was reviewed by Kenneth Duke way back in Issue 47 (Winter, 1993). However, what I am reviewing is an updated version, with an all-new woofer and a different crossover network. Like the earlier version, it is a hybrid design (its formal name is hybrid Linear Field Transducer), and it incorporates two proprietary-design, flat-panel, line-source drivers (midrange and tweeter), in combination with an extremely heavy-duty woofer driver.

Panel and cone-woofer speaker arrangements are not unusual, but in this case Bruceís company not only makes the very special planar-magnetic drivers, but also has the woofer custom built by an outside supplier to his very exacting and unique specifications. This is a hands-on operation from the word go, with nothing in the way of OEM, off-the-shelf fickleness allowed to chance.

The LFT-VIII is 13 inches wide and 60 inches tall. The midrange-tweeter panel is mounted to a moderately sized (1,400 cubic inches) woofer enclosure at the bottom, with the bulk of the enclosure extending to the rear. With the grill-screen covers in place, the entire front surface is flat from top to bottom. The panel itself is only an inch thick, but with the grill screens installed (one covers the entire front and the second one covers the back panel area above the woofer section) the depth increases to about 2.75 inches. The screens themselves are held in place by velcro buttons, so they are easy to remove if the user wants to view the raw panels.

The woofer enclosure juts backward about 18 inches (although its sloping backside makes it seem smaller than it is), and there is additional depth in the way of sturdy outriggers front and rear, which are fitted with easily adjustable spikes. The outriggers are relatively inconspicuous and help to stabilize the systems on carpeted surfaces. On hardwood surfaces they might have a tendency to cause floor damage.

The panels themselves are made of flat-black painted steel. They are very solidly constructed and surprisingly heavy. The aluminum-etched mylar sheeting fitted between them is very well protected by those steel braces and the magnet assembly. Note that I said ìbetween them.î As I mentioned at the beginning of this review, Bruce built the first push-pull planar-magnetic speaker and the LFT-VIII carries on this tradition. There are magnets on both sides of the mylar panels, and unlike some other designs that locate the magnets on only one side, this results in a more linear output, particularly at high volume levels.

The midrange driverís mylar diaphragm is about 41 inches long and has an area of 126 square inches, and the tweeter is about 18 inches long and a bit more than a half-inch wide, and has a surface area of 10 square inches. The crossover point between them is a heady 10 kHz. The midrange panel can actually go considerably higher than this frequency, and it would be possible to have the system eschew the use of a tweeter at all. However, doing that would cause severe beaming in the top octave. Having a relatively short line-source tweeter about a half-inch wide handle the top octave minimizes horizontal directional effects. The crossover is a first-order job (6 dB per octave high and low pass), meaning that there is a considerable overlap in output between the drivers above and below 10 kHz. The system weighs in at 65 pounds and is warranted for three years on parts and one year on labor.

At the back of the junction area between the woofer enclosure and the panel, there are electrical connections that allow for standard hookups or biamplification. You can also biwire if you care to, but anybody who knows me knows that I think that biwiring is a waste of resources. Thick jumper wires connect the low-pass and high-pass sections together for a more standard hookup.

Speaking of hookups, the two pairs of connectors on the system are five-way binding posts that Bruce makes himself and also sells independently under the Edison Price name. These ìMusic Postî fittings are the most solid speaker binding posts I have ever seen. They are machined from tellurium copper bar stock, and pairs of them are then molded into a clear polycarbonate housing that is designed for easy installation as a replacement for standard double binding posts. One interesting characteristic of these posts is that you can tighten the knurled nut part of the fitting after inserting a banana plug, compressing the front of the post around the plug shaft for a really solid hookup. These connectors are also for sale independently at $22 per pair, and under some conditions they would make fine do-it-yourself replacements for the cheaper versions found on some speakers or even amplifiers.

By modern standards, the LFT-VIII is relatively insensitive to electrical inputs. With 2.83 volts applied, the measured output at one meter is rated at only 83 dB. This means that a fair amount of power is required to get the speakers to do their stuff. ET suggests a minimum of 75 watts, and that is a safe minimum.

In one listening session done some time after my initial series of tests and auditions, I got good results with a Yamaha integrated amp that was rated at a modest 80 wpc into eight ohms. However, it has to be pointed out that the average impedance of the LFT-VIII is somewhat above that, meaning that solid-state amplifiers will not be able to generate as much power as their typical eight-ohm ratings would indicate. For this reason, I suggest using an amp capable of at least 100 watts per channel into eight ohms, with 200 wpc not being unreasonable.

The binding posts behind the panels are internally connected to several sets of screw connectors that are located close to the bottom of the rear grill. One set is connected directly to the midrange panel and should be left alone. The tweeter has three hot-lead connectors, however, with low-, medium-, and high-output options available. While this is a somewhat tedious way to adjust the output of the tweeter, it does insure a much more solid and reliable connection than what would be possible with a simple toggle or rotary switch.

As I noted above, the woofer is built to unusual specifications, and it is dedicated for use in this speaker system. It is a seriously heavy-duty eight-inch driver, with a considerably weightier than average diaphragm (56 grams). It has a free-air resonance of 18 Hz, and is mounted in the above-noted 1,400 cubic-inch enclosure in the classic acoustic suspension manner. The woofer crosses over to the midrange at 180 Hz, with both the high- and low-pass crossover sections being first order (6 dB per octave) slopes.

Those who have read some of my reviews in the past know how much stock I put in a well-written ownerís manual. Many that come with speakers do not do much more than tell the owner what a great set of speakers they have, and besides a few cursory suggestions and some hyped info, leave the set up and placement work to the userís imagination.

The LFT-VIII manual is an exception. After explaining how to assemble the systems (they ship in three cartons and the panels have to be carefully attached to the woofer sections), the booklet goes on to explain in detail how the LFT-VIII systems were designed, how they work, and how to get the best out of them. It also delivers a brief history of the operation of other flat-panel designs to the point of almost being a treatise on the subject. It is easily the most informative and candid loudspeaker ownerís manual I have ever encountered.

I set the speakers up in my 18 x 22-foot main room (3,400 cubic feet), and oriented them several feet out from the 22-foot front wall and several more feet from both side walls. The systems are mirror-imaged pairs, and they should be oriented with the tweeters inboard from the midrange drivers. Following the suggestion in the manual, I angled them towards the listening area. I used a Samsung DVD player for CD playback duties, used my vintage Carver C1 preamp for control duties, and initially powered the systems with a pair of Sherbourn 1/300MB monoblock amps. Although I do not put much stock in exotic wires, I used a set of Dunlavy LCR Ultra cables, just to make everything as top-tier as I could.

I then used my AudioControl SA-3051 RTA to do one of my standard 20-second integration measurements while slowly moving the microphone over a 1 x 1 x 5 foot area near seated ear-height level at the listening couch.

The results were indicative of a very well engineered speaker system. Indeed, excepting a 3-dB dip centered at 315 Hz, over the very important range between 250 Hz and 9 kHz the response was a remarkable +/- 2 dB, which is right up there with the best systems I have auditioned in the pastóand I am talking about the best of those systems at any price.

Below 250 Hz, the output was typically influenced by boundary-related artifacts, but the results were easily as good as what I got earlier with the $6,800 Triad InRoom Silver and $5,600 Waveform MC/MC.1 sub/sat systems, and also with the $5,500 Dunlavy Cantatas. Room gain allowed the low end to climb steadily in output below 250 Hz and it peaked at about 80 Hz, with a gradual sloping downward below that frequency. We are talking about really gradual here; indeed, the low-end extension was solid down to 31.5 Hz, with a fairly rapid falloff below that frequency. That is exemplary performance for a pair of 8-inch woofers of any kind.

Above 8 kHz, the response of the systems began to taper off, as one might expect with line-source radiating systems. Bruce had supplied me with a three-meter room-response curve he had run on the systems, and the same amount rolloff showed up there. I had measured with the tweeter set to the middle position, but the results with the high position were close to the same. The response was down 5 dB at 10 kHz and 9 dB down at about 13 kHz. Remember that this is the average room response, which will always be influenced by off-axis power-response losses in drivers as the frequency climbs.

We have to put this in proper context, however. While I tend to prefer a strong reverberant field response into the top octave, when you listen to systems that are more directional up high they have a certain degree of focus and detail that is hard to criticize. And of course when a speaker is also radiating from the rear the front-wall reflections add a degree of spaciousness and depth that is hard to define but nearly always advantageous. When listening to most music, the response characteristics of the LFT-VIII in the top octave are surprisingly close to the proper live-performance mark.

I also did my usual maximum-output tests with the woofers. When I do this with subwoofers I place them in the left-front corner of my room, about 17 feet from a fixed microphone position. When doing it with a stereo pair of speakers I will leave the microphone in place, but of course the speakers themselves will not both be in the corner. Rather, they are in a standard stereo position, and in this case the LFT-VIII units were about 12 feet from the sweet spot.

Under those conditions, the systems could cleanly hit 100 dB at 31.5 Hz and 90 dB at 20 Hz. As points of reference, I will note that the Dunlavy Cantatas I reviewed in Issue 87 (which have 10-inch woofers) could hit 102 and 100 dB, respectively and a pair of Polk Lsi25 systems I am currently reviewing (also outfitted with 10 inchers) could hit 101 and 83. The Sunfire Subwoofer Super Junior I am also currently reviewing could only cleanly hit 96 dB at 31.5 Hz and was out of the picture altogether at 20.

Working together, the maximum output abilities of the two LFT-VIII systems were roughly comparable to either the RBH 12-SE or the Velodyne CT-120 subwoofers that I reviewed in issues 89 and 85. Whatís more, I believe that the ET systems were a bit cleaner and flatter down really low than those two subwoofers.

I also used the Delos Surround Spectacular test CD set (DE 3179) to check out imaging characteristics, left/right panning smoothness, and bass-sweep response. In each case the results were as good as I have heard with any other speaker systems. The subjective bass sweep was particularly impressive, with clean extension down to below 30 Hz. Even at 25 Hz the sound was clean and strong, and at 20 Hz, the clean signal was still there, although it was substantially reduced in intensity. These are terrific little woofers that are nearly as linear down at the bottom as a Hsu VTF-2 subwoofer, although they will not play quite as loud above 25 Hz.

Of course, test-tone evaluations, with and without electrical measurements, will only give us part of the story - perhaps only the least important part. The systems also sounded terrific with musical inputs, both when listening to them only and also when comparing them to other fine systems.

One of my favorite musical discs remains Seventeenth Century Music and Dance from the Viennese Court, a selection original-instrument performed material by Heinrich Biber and Johann Schmelzer (Chesky 173). With the ET speakers the result was some of the most realistic sounding string tones I have heard in my listening room. In addition, the soundstage was very refined, with a proper degree of ambiance. In the same Baroque tradition was a marvelous transcription of recorders and string works by Antonio Vivaldi, Giuseppe Sammartini, and William Babell (Claves 50-9706). The sound on this release is ultra-clean and detailed, and the ET systems handled the reproducing task in championship style.

Another interesting and well-recorded disc was the Symphony Number Four, by Vaughan Williams, coupled with his Mass in G minor and Six Choral Songs (Chandos 9984). The Number Four is a rather dissonant work that stands in contrast to some of the other Vaughan Williams symphonies, and it stands in rather serious contrast to the Mass. The recording itself was magnificently handled by the ET systems, with the vocal parts reproduced about as well as possible. A newer, equally large-scaled presentation was a wonderful rendition of Holstís The Planets (Naxos 8.55576). With it, the sound was smooth, clean, and dynamic, with a very good blend between the performers and the hall acoustics. There is some deep bass on this disc, and the ET speakers had no trouble with it at all.

Of course, when auditioning speakers there is no substitute for comparing a new pair to a pair of systems previously found to be exemplary performers. I set up the LFT-VIII systems next to a pair of stand-mounted Triad InRoom Silver jobs, supported by a Hsu VTF-2 subwoofer. (The Triads are small enough to not cause too much in the way of adjacent-speaker interference effects and the 28-inch stands I used were skinny enough to not cause too much trouble themselves.) The ET systems remained driven by the Carver/Sherbourn combination, while the Triad/Hsu combination (a speaker package that would normally list for about $4,500) was under the control of an Onkyo TX-DS787 receiver. The subwoofer was integrated with the Triads at 80 Hz by the Onkyoís built-in crossover network. The LFT-VIII systems ran full bandwidth, with no subwoofer. Average levels were carefully matched.

The pairs were staggered, AB/AB, so as to keep each the same distances apart. This does cause a soundstage shift when comparing, but I believe that the importance of keeping the spread distances the same outweighs precise soundstaging considerations, especially considering that all one needs to do to compensate is shift oneís head to either side about a foot during the switchoffs.

With a recording of the Telemann Recorder Suite and some additional recorder concertos (Naxos 8.554018), the two combinations were equally impressive. The ET systems sounded a bit more mellow and subdued, while at the same time the slightly brighter sounding Triads managed to sound more distant. The two pairs sounded nearly identical with the recorders themselves, which is understandable, given that both are extremely flat responding over that instrumentís operating range.

The previously mentioned Planets recording showed the ET systems to be more open in their presentation. The Triads continued to sound more distant, with the LFT-VIII pair delivering a somewhat bigger soundstage.

Of course, my main comparison disc remains the Delos Engineerís Choice II recording (DE 3179), which contains an impressive cross-section of material recorded by John Eargle. With this material, the more subtle differences between the systems were highlighted, although they indeed remained subtle.

With the discís guitar sections, the Triads continued to sound more distant, but the face-off would have to be considered a dead heat in terms of which pair sounded best. With larger-scale material, the ET systems were richer sounding in the middle bass, with a larger sense of soundstage depth and spread. The Triads often seemed more focused in terms of imaging, but the ET systems were more spacious. Clarity and definition came across as an almost dead heat, with each speaker taking turns with the lead during specific musical passages. With the female vocal selection the ET systems seemed a bit richer and clearer sounding, and as usual the Triads seemed a bit more distant. The overall contest was a tie.

In addition to comparing against the Triads, I also had the LFT-VIII systems face off against a $1,500 (including stands) pair of low-profile AR Phantom 8.3 units, also with subwoofer assistance, with the low bass this time handled by the Sunfire Subwoofer Super Junior. The combined package has a list price of $2,500.

It was easy to see that the ET systems were closer to the Phantoms in terms of spatial presentation and frequency balance than they were to the Silvers. On a variety of musical selections (mostly from the Delos disc), the LFT-VIII units were a bit more spacious but also maybe a bit less detailed than the AR systems. The latter were also just a tad brighter sounding at times, although with violin string tones the two pairs often sounded nearly the same. Overall, the AR systems were a bit more analytical and a bit less diffuse than the ET systems. There was no way to award first prize to either package, although the pint-sized Sunfire sub was no match for the ET systems when really low bass signals were present.

I also did a series of quick pop-music face-offs with all three packages, with my top choice being the very well recorded Dire Straits album On Every Street (Warner 26680). Both combinations were superb, with the Triads and AR systems having a bit more snap with the snare drums and with the ET systems having a bit more richness in the middle bass region than either of the other combinations. Vocals were excellent with all three.

Finally, because the ET systems were performing so well, I hauled out a pair of $5,500 Dunlavy Cantatas and did a quick series of face-offs with them. (A comparison like this is problematical, because the large size of the Cantata enclosures certainly interfered with the radiation patterns of the two ET systems.) The results were as expected, given that when I had previously compared the Triads against the Dunlavys, and the result was a technical dead heat. The LFT-VIII systems easily held their own against the Dunlavy units, although admittedly the lead changed places a number of times, depending upon what track was being played. Even with seriously room-filling material, the ET systems were able to easily keep up with the Cantatas.

The above series of comparisons, in combination with the measurements, make this an easy report to summarize. The Eminent Technology LFT-VIII systems are among the best full-range loudspeakers I have yet auditioned. They can hold their own against some superb satellite/subwoofer combinations that cost considerably more than the modest price of the ET systems, and even held their own against speakers that some consider to be a reference standard in the upper-middle price category. In addition to sounding superb, they make a technological styling statement that will appeal to a lot of audio buffs. I know that the style appealed to me.

If you purchase a pair of these speakers, I simply cannot see how you could be anything but eminently satisfied.


Copywrite 2003 by the Sensible Sound and Howard Ferstler

This article reprinted with permission from The Sensible Sound. All Rights Reserved.

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