Eminent Technology LFT-8A Speakers

by | Apr 27, 2006 | Component Reviews | 1 comment

Eminent Technology LFT-8A Speakers    SRP: $1599 pair

LFT-8 General Specifications

 
Power Requirements             75 Watts Minimum              
Sensitivity                    83 dB (pink noise, 20 – 20kH) at 1 watt/1 meter (2.83 V)    
Frequency Response             25 Hz-20 kHz ±4 dB (typical room)                         
Phase Accuracy                 ± 20-100 Hz-31 kHz           
High Frequency Level           Flat, – 6dB, -12dB at 20kHz smooth rolloff                
Impedance                      Nominal 8 Ohm Rating                  
Maximum SPL                    105 dB at 1 meter             
Dimensions                     13″ W x 60″ H x 1″ Depth                         
Shipping Weight                65 lbs. Each                  
Warranty                       3 Years Parts, 1 Year Labor   
Finish           Oak Standard, Black Painted Oak or Walnut 
 
                                                                                                            
LFT-8 Panel Specifications

Magnet Type                    Ceramic 8                     
Mid-Range Diaphragm Area       126 sq. in.                     
Foil Thickness                 .00033                        
Mylar Thickness                .0005                         
Laminate Adhesive Thickness    .00015                        
Gap Between Conductors         .03                           
Peak-to-Peak Diaphragm
Displacement     .180                                                                        
Tweeter Diaphragm area         10 sq. in.                      
Tweeter Peak to Peak           .050                          
Displacement                                                 

LFT-8 Woofer Driver Specifications

 
Box Volume                     23 Liters                     
                                       1403 in.3                      
                                       .812 ft.3                      
Speaker Diameter               8 inch                        
Magnet Weight                  1 lb. 2 oz.                      
Impedance                          8 Ohms                        
DC Resistance                     6.65 Ohms                     
Inductance                         2.27 mH                        
Free Air Resonance             18 Hz ±15%  

Eminent Technology, Inc.
225 East Palmer Street
Tallahassee, FL 32301                 
Phone: (850)575-5655
FAX: (850)224-5999
Web site: www.eminent-tech.com
E-Mail: info@eminent-tech.com


 
Intro

The Eminent Technology LFT-8 is the firm’s first hybrid loudspeaker using Planar Magnetic transducers combined with a low Q 8″ woofer in a sealed enclosure.
The magnetic drive principle developed by Eminent Technology for the LFT speaker series is unique. As the diaphragm of the speaker moves between the magnets following an audio signal, the magnetic field remains constant. In a way, it is the magnetic equivalent of a push-pull electrostatic loudspeaker, except that it requires no step-up transformer or bias voltage and the audio signal is applied directly to the diaphragm.

In order to obtain a uniform driving force over the entire surface area of the diaphragm, a low mass foil/mylar diaphragm is used with conductor traces etched (like a circuit board) with high resolution. The large surface area of the midrange driver gives good power handling. A lightweight diaphragm is utilized for the high frequency driver. The LFT-VIII minimum recommended amplifier is 50 watts/channel and the maximum is 200 watts/channel. The speaker is moderately efficient; its impedance averages 8 ohms.
 
The low frequency woofer was designed to blend seamlessly with the mid-range and high-frequency drivers. The design uses a very low crossover frequency (180 Hz) between woofer and midrange. The woofer has a very high compliance and operates with a near critically-damped system Q of .58 to insure excellent transient response.
The panels are attached to a rigid steel frame to prevent resonances, and the woofer is mounted in a rigidly braced enclosure. The LFT-VIII is bi-ampable and uses the Edison Price Music Post. The standard finish is oak with black grills (shown), optional finishes are available for an additional charge.
 
Time for New Speakers

The reason for my sudden interest in reviewing speakers was brought on by the demise of my faithful 30-year-old Koss Model 1A electrostatic speakers. They were a really great speaker system that had been heavily modified over the years. They cost $7300 in 1976, it was one of the most expensive speakers of the time. I had listened to hundreds of speaker systems over the years and never felt the need for replacement. A few speakers might have one or two areas slightly better than the Kosses, but none could come up with the whole package of sound that the Koss had. The ones that came close were in the tens of thousands of dollars. The Koss had five bass panels that were about 9 by 22 inches each. The bass panels are also in an enclosed area to control the bass. This made them able to move a fair amount of air but also do it very quickly. This made for a quick punchy mid bass with good detail. Most electrostatic speakers use a single large panel not in an enclosed area for bass and often midrange to. This made for a slower, floppier and less-defined bass. Dynamic drivers usually produce a slower less defined bass.

The two quasi-ribbon midrange drivers produced very quick detailed sound. No dynamic driver can match the speed of an electrostatic or ribbon midrange. Most electrostatic speakers expect the bass panels to cover the midrange also. This produces a compromised sound. The Koss then had both a treble and a tweeter driver. This made them capable of producing very light airy high frequencies. Up until now no dynamic tweeter could compete. Lately new tweeters made from diamond, beryllium or ceramic material have closed the gap quite a bit. Unfortunately they are very expensive at this time. Ribbon tweeters are starting to be used in more mostly dynamic designs to get these high frequencies. The Oregon Triode Society had made a DAT recording of a large local organ. The recording was taken around to various systems in town. The Koss system produced the most realistic reproduction of the sound. This was a real feat considering that most electrostatics do not do well at Big and Loud. The Koss system produced sound in excess of 115 dB. I feel if the Koss speakers were produced today with modern materials that they might be the best speakers in the world. But I also estimate that they would cost between 50 and 100 thousand dollars. So begins the “Mission Impossible” to find a speaker to replace the Koss at an affordable price.

 
Speaker Design Considerations

Speaker design is fraught with compromises. The ideal speaker system would be a single point source. It would create all frequencies, at all volumes, in proper wave and phase alignment. Physics and reality both say that this can not happen. Producing sound is creating air movement. High frequencies require small but very fast air movement. Bass requires much larger air movement and only somewhat slower. No driver we have now can do this. So we have drivers of different sizes (woofers, midrange and tweeters). This means the designer needs a crossover network to send the proper signal to drivers. Unfortunately, crossovers always create phase shift. The more narrow the frequency range that a driver needs to produce the better it can be designed to produce that range. But the more drivers you use the more crossovers you need, causing more phase shift. There is also a problem with multiple drivers regarding time alignment. Normally a tone is produced with its harmonics riding on top. If a tone and its harmonics come from different drivers, they cannot properly ride on each other. The best that a multidriver speaker can do is attempt to make the waves arrive at the listener at the same time and in the proper phase.

Most speaker systems are either two or three way. The two way systems are usually smaller and image better. Their faults are that they generally do not go to the frequency extremes as well or have good dynamics or high sound pressure ability. The three way systems generally play louder and have better frequency extremes. They may not image quiet as well and have more room interaction problems. Four way systems usually have what we call a subwoofer – dealing with frequencies below 60 hertz. Many speakers may say they go down below 70 cycles, but very few will do it in a real room. The manufacturer may say his speaker goes down to 50 cycles with the caveat of +/- 5-10 dB. For every 3 dB the sound pressure is cut in half. The response is usually measured about 3 feet directly in front of the driver. Sound at these frequencies also becomes problematic because of room acoustics and size. Good low frequency is the hardest for a speaker system to produce. The five-way system usually contains a super-tweeter. That is a driver designed to go from 10,000 cycles to above 35,000 cycles. Most speaker systems are designed to roll off completely by 20,000 cycles. People with good hearing are said to only hear to up to 20 thousand cycles. Reviews on the new add-on super tweeters are positive and seem to indicate that you may not technically hear them, but that you will sense them and it will make the music seem more realistic. I hope to soon try them out to see what I can observe.

The biggest compromises come with woofer selection. You can pick a larger, heavier woofer, with a longer throw to produce more and lower bass. The problem is that it will be slower-sounding and take a bigger amplifier to control it. The problem is increased by how high in the frequency range to woofer has to cover. You could choose a smaller, lighter and faster woofer that will create snappier bass and better higher frequencies. The problem is that it will not create as deep or as much bass as the bigger woofer. Some of the bigger systems use multiple units of a driver to create more sound. The problem with this is that the same note is being played by drivers at a distance from each other. The worst case of this is a vertical row of woofers. The bass is smeared by a note coming from a large area at slightly different times. The bass image is usually unrealistically big and the sound a little tubby. Big speaker systems also need large rooms to make them sound the best. Room acoustical treatment also becomes more important. There is no perfect speaker out there – all speakers have compromises. Hopefully the more money you spend the less compromises must be made. What a speaker buyer must do is choose what compromises he can live with.

When asked what I want from a system, like most audiophiles I answer Everything! The main thing I find missing in most systems is the speed of the music produced. Live sound has a quickness to it and is usually somewhat transient. A system needs to capture the initial attack of a sound, play the note and get off the note quickly and at the proper time. The next thing I find missing in most systems is transient ability, both macro and micro. This means getting to full loudness or quietness quickly. A slowed initial transient vastly reduces the excitement of music. A slowed drop from a note covers up harmonics and fine detail. A system that does not have good micro-dynamics robs the music of emotion. I feel that less bass is better than mediocre bass. These biases are why I have a tendency to like electrostatic and ribbon type of speakers. I had heard the ET speakers about ten years ago and was impressed. They had also received good reviews in other publications. I requested a pair for review. I listened around town, while waiting for the ETs, to speakers costing up to $10,000, but could find nothing that was satisfactory to me.

                                                       
The Arrival

With glee and trepidation I received the ETs after several months of waiting. They arrived with one of the most thorough shipping packaging I had seen. I had also requested that Sound Anchor stands be sent. The speakers and stands arrived in four large fairly heavy boxes. The thorough packaging meant about 20 minutes to unpack them. They must then be assembled. If you buy them from a dealer, hopefully they will be already assembled. I highly suggest two people for the process. I did it myself, but it would have been faster and easier with two. I assembled then where I thought they might go. I ran about ten hours of rock FM radio thru the ETs, before I started seriously listen to them.

                                              
Initial Observations

The speakers seem well-built, especially considering the price. They were taller than I expected from the pictures. With the grill cloths on, they looked very presentable, better than I expected. The woofer box was quite heavy for their size. Unfortunately they did not ship the standard feet, so I could not compare them with the Sound Anchors. I found that the speakers were a bit side-to-side tippy because of their height and narrowness. From the photo of the standard feet, they would not have worked with my thick carpet, but might be more usable on a hard surface floor. Because of their construction the speakers were not easy to move around even though they only weighed less than 70 lbs. Being about one quarter of the size of the Kosses, they made my room much more open feeling and greatly increased the viewing angle for my TV display. The speaker binding posts are made for bi-amping or bi-wiring with one set for the ribbons and one for the woofer. Jumper wires are included if you only use a stereo amp. The posts are of good quality, but I didn’t like the slit for the bare wire instead of a round hole. It would be hard to get large gauge wire in the slit. I feel it is  better to use a spade or ring connector anyway.  
                                                
                                               
The System and Setup

I run a combined audio and video system. My room is 20 by 20 feet, with 9 foot acoustically-tiled ceiling. There is a thick heavy pile carpet on the floor. The room is heavily acoustically-treated and fairly dead. The system is set up on one of the 20 foot walls. The equipment rack is on the right third of the wall. The speakers, with the 60” XRB1 LCD projection TV in the middle, are on the left two-thirds of the wall. The speakers are out about 5 feet from the rear wall. The speakers are powered by a modified Crown Macro Reference amplifier. The preamp is a modified Outlaw Audio 950. The sound sources are a modified Marantz DV8300 combo player, Monarchy CD/LD drive unit feeding a  MSB Ultra DAC, Teac 5500 open reel tape recorder, and a Direct TV DVR satellite receiver. Main cabling is Cardas Hex Gold. I biwired the speakers using separate cables to the ribbons and the woofer. Digital, video and surround cables are Jena Labs. Surround amps are NAD GFA 545  (rear), Sumo Polaris (sides), and a bridged-to- mono Parasound HCA 600 (center). The rear and center channel speakers are Radio Shack’s original model with Linaeum tweeters. The side channels are Chapman Mini Monitors. Accessories used are Corner Tunes; Bright Star sandboxes; Shakti stones, On Lines and Sonic Hallographs; lead bricks and sheets; Tube Traps; various isolation feet; TeknaSonic vibration absorbers; Mapingo squares; and speaker cable risers. Subwoofers are a pair of Thorough Bass Technology Magellan 8s and a single Paradigm 8 inch sub. I used the Sound Anchor stands for the former ETs, which I consider a necessity. Surround sound levels were calibrated using a sound pressure meter for both the preamp and 5.1 output of the Marantz.

                                                     
Initial Listening 

Right off, the sound of the speakers was fairly good. The woofer mated seamlessly with the ribbons. They mated very well with my subwoofers and surround speakers, fairly detailed and dynamic. The LFT-8s liked being played with the surround system because it helped to fill the room with sound. When I switched to stereo I had to increase the volume about 8 dB to fill the room with sound equivalent to that of the system in surround mode. Even with a very dead large room the speakers could fill the room with sound on their own. The speakers do like some power however. I would say that at least 200 watts of high current power is advisable. The bass was not real deep, but it was tight. Speed was good in all frequency ranges. The general sound was a little on the polite side.

                                              
Tweaking the Speakers

Now lets see what they can really sound like. I moved them to 8 ft. apart and toed them in a bit. I aimed them so that that the tweeter and center of the midrange panel were the same distance from the ears of a centered listener to the system. The sound now had more focus, better detail and a little more dynamics. I next put a TeknaSonic vibration absorber on the sloped back of each woofer box. Again there was improvement in detail, focus and dynamics. I next put a 25 lb. lead brick on each side of the binding posts on top of the woofer box. The bass became even tighter and the sound throughout the frequency range was improved. An audio friend was over when I did the last tweak. I commented to him that the one thing I noticed that was slightly lacking was the forward push on the sound of horn instruments and voices. I then put a 25 lb. lead brick on each of the Sound Anchor legs behind the woofer box. This fixed the deficiency for the most part. The sound was greatly improved; it was now crisp, detailed, layered, dynamic and totally musical.

Do not for a minute think that these tweaks are making up for some deficiency in these speakers. The tweaks have worked well on every speaker system I have tried them on. The better the system is, the bigger difference it made. It worked very well in a $100,000+ system with the Avalon Eidolon speakers. I then recalibrated the system and started to really enjoy the music. On the Proprius recording of Cantate Domino the sound stage was both wide and deep. The voices were layered in precise positions with better clarity than I had heard before. The room acoustics of the organ were well represented. The sound stage held together even during very loud complex passages. On the Mary Gauthier disc Mercy Now her voice was solid, well-positioned and detailed. Bass was deep and tight. The accompanying instruments were solid and detailed. This is an album with great song writing and very strong accompanying instrumentation. It sounds like a very good SACD except it is a standard CD. The speakers let you hear all the emotion and sound that was put down on the disc. On the Dire Strait’s SACD Brothers in Arms the speakers showed that they could also rock out. The sound was crisp yet had a good sense of drive. In the opening of Gorecki’s Symphony No. 3 on a Naïve SACD the speakers gave me new insight into the opening of the symphony. I had played it on an audiophile friend’s system that also had the Thorough Bass subwoofers. It sounded good but not very interesting. The ETs brought out dynamic contrasts and nuances the made the music far more interesting. The bass frequencies had a better sense of power and tonality. The LA4’s SACD Just Friends sounds better than anything I have heard on disc before. The guitar was wonderfully detailed and crisp. The cymbals rang out with exquisite airiness, and the bass was solid and deep. I thought, now this is what music should sound like! On scene three (the Naval battle scene) of the movie Master and Commander, the transient ability of the ETs had you diving for cover. The speed and dynamics happened so quickly that it was almost scary. I found myself putting on an album to listen to a certain cut and ending up listening to the whole album.

                                                      
Conclusions

Listening to these speakers made me think of lyrics from the rock opera Tommy:

 
Listening to you I get the music, gazing at you I get the heat, following you I climb the mountain, I get excitement at your feet! Right behind you I see the millions, on you I see the glory, from you, I get the opinions, from you, I get the story.
The speakers have many strong characteristics. First they are very dynamic. Their imaging ability is strong and pinpoint. They capture nuances and dynamic contrasts extremely well. They do a great job flushing out the emotion and feeling of a piece of music. Their bass, while not real deep, is tight and controlled. It is as good or better than most speakers under $10,000, and some much more expensive than that. This makes them perfect for fast musical subwoofers like the Thorough Bass subs. The highs, if they are on the recording, are very airy. They have fairly good punch to the midrange. They do need a fair amount of power. I would say at least 200 WPC. A lot more than that is a good idea. They are very particular about music quality. The ETs will quickly show you differences in recording quality. Compared to the Koss they are better in all areas except two: Because of their size and being ribbons they do not have as much room-filling sound ability at low volume as the much bigger Kosses. I found myself turning up the volume on quiet sections of music, then feeling it became too loud on loud passages.
My room is really dead acoustically, being set up for the large Koss speaker system. I will be experimenting with reducing the amount of damping in the room. If a person wants more sound they might consider the double ETs as reviewed in Positive Feedback a couple of years back. The second is sheer high level volume. The Koss were unfazed at 115 dB sound levels, where I would not feel comfortable above 98 dB with the ETs. The ETs seem very happy in a good surround sound system. Are they a speaker system for everybody? The answer is no. If you want to play 100 dB+ hard rock or a lot of heavy symphonic climaxes at above 100 dB level, they are probably not the speakers for you. If however you want to revel in good music at normal volumes, I cannot think of an affordable speaker system that will give you as much musical insight and enjoyment as the ETs. This is the best value in speakers I know of. A $1600 speaker that can deliver audiophile sound is what the average audiophile has been hoping for.
— Clay Swartz
 

 

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