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THE SYNTHESIS LM-250 LM-20: Two-way dynamic speaker. Driver compliment: 6 1 / 2" polypropylene woofer. 1" soft polymer dome tweeter. Crossover: 1,500 Hz.
Sensitivity: 90 dB. Finish: oak side panels, with brown open-cell foam grill. Dimensions: 14 1 / 2" by 14 1 / 2" by 10 1 / 2". Weight: 18 pounds. Price: $600 per pair.
LM-250: Two-way dynamic speaker.
Driver compliment: 8" polypropylene woofer. 1" doped fabric dome tweeter. Crossover 1250 Hz.
Sensitivity: 91 db. Dimensions: 10 1 / 2" by 10 1 / 2" by 33 3 / 4 ". Weight: 46 pounds. Price: $1185 per pair.
MANUFACTURER: Synthesis, 2817 Dorr Avenue, Fairfax, Va., 22031. (703) 698-7905.
One of the most basic differences between mid -fi and the high end is the level of speed, transparency, and resolution in speaker systems. Most low- and medium priced speakers have a nice built-in boom in the upper bass and rolled highs. Coupled to the usual lack of phase coherence and speed in the upper midrange and treble, the inevitable result is a speaker system with poor resolution, and bass overhang, lacking in soundstage data, detail, and air.
Only a limited number of manufacturers of cone systems have broken out of this mold. Snell, Spica, Thiel, and Vandersteen are the names that come most easily to mind, although I've also been impressed with the work of Fanfare, GNP, Kindel, VMPS, and several other less-well publicized products.
If you want to see a real horror story, look at the Consumer Reports frequency sweeps for affordable speakers-they're horrible for even the low-priced products from most high-end manufacturers, and those sweeps (and accuracy scores) ignore phase accuracy, pulse response, and other sonic horrors associated with these speakers.
The Synthesis brand name is part of Con rad Johnson's effort to join the elite who strive for real accuracy-Thiel, Vandersteen, etc.-and beat these manufacturers at their own game. The designs have been heavily influenced by speaker designer Dave Fokos (and Bill Conrad and Lew Johnson), using FFT and computer analysis, as well as the less-known engineering technique of actually listening to the product. John Fuselier's research work had some influence on the initial design work, as did careful listening to competing high-end products.
The first three products resulting from this design effort are the LM-20, LM-200, and LM-250. All three speakers use top quality drivers and crossovers, including the two models under review, which represent the top and bottom of the line (though a larger model with more extended bass is under design). The LM-20: $600/pair The LM-20 bottom-of-the-line is a full-range small monitor designed for stand mounting several feet away from side and rear walls. It is fully time- and phase aligned,' and has an exceptionally heavy cabinet shaped to improve time alignment, reduce standing waves, and reduce diffraction effects. It benefits (as do most speakers) from having as few pieces of furniture as possible between the speakers and the listening position.
The LM-20s are tight and fast over their entire apparent bandwidth, and have an exceptionally extended, flat, detailed-and moderately demanding-treble. Unlike the upper octaves in less transparent and revealing speakers, the LM-20s clearly reveal the grain and hardness in poor electronics.
Unlike some small monitors, however, their highs are not over-demanding in terms of the components likely to be used with a $600 speaker system: you can thoroughly enjoy the LM-20 speakers with NAD-level equipment. The characteristic upper midrange hardness of Harmon/Kardon electronics comes through a bit too well, but is still quite listenable, and the LM-20s also pair well with most Yamaha electronics. You only have to watch out for some of the harsher Technics and Sansui equipment-their upper midrange comes through too clearly and can get fatiguing.
At the same time, the LM-20s mate quite well with less expensive tube gear, the new transistor-tube hybrids, and moderate priced separates from companies like Adcom, PS Audio, and Superphon.
The transition from the highs to the midrange is very good, and cleaner and more detailed than that of most small British monitors. Harmonic detail is excellent, and musical changes are unusually smooth. There are some minor variations in timbre, but none of the kind that change the basic sound character of instruments and voices. Strings, woodwinds, and brass are all very detailed, but keep their musical air. Voice is relatively neutral, but with perhaps a touch too much upper midrange.
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1. I’m unhappy with this statement since, as far as I know, neither IC nor any other members of Stereophile’s staff has a technique for measuring time or phase-alignment More accurate would he are claimed to he fully time- and phase-aligned• -LA
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Like the Spicas, and almost all small monitors, however, the LM-20s' coherence begins to break down in the lower midrange. From the upper bass down, the LM-20s are lacking in energy and power.
The result is an imbalance that I can easily live with, but never forget. The highs are too clear, the soundstage perspective is slightly forward, undertones are never correct, hall effects are muted, and the deep bass register is simply gone.
The LM-20 does have slightly more bass extension than the Spica TC-50s without their subwoofer, and is flatter, tighter, and cleaner than the bass of most British small monitors, including several that cost almost three times as much. There is sufficient natural bass to fully cover male voice and most of the cello. I've found that most British speakers have an apparent rise be tween 90 and 150 Hz that at least slightly colors voice, strings, and everything else.
As for soundstaging, the LM-20s float a wide image with good height and moderate depth. On the proper stands, placed at least 18" from the rear and side walls, and with the optimal listening position (slightly closer to the speakers than the distance between them), the LM-20s do a very good job of placing instruments in a stable wide arc without the artificial spotlighting common in very small point source monitors.
Dynamics are also surprisingly good.
The LM-20s will never be rock speakers, but they do play louder than the Spicas, and also rival the Spicas in the resolution of low-level musical data. Dynamic transitions are relatively smooth from low- to high-level passages, although there is the normal small-monitor tendency to slightly emphasize the top octaves as the volume rises to high listening levels.
In summary, the LM-20s are not a rival to the Quad ESL-63s, or to the better cone competition in the $1000-plus bracket, but they seriously rival the Spicas (costing 5150 more), and are useful additions to the high end in a price point where there is appallingly little U.S. competition. Given the re cent fortunes of the British pound, the LM-20s are also severe competition for even the best British small monitors under $900. Many British speakers will be sweeter and more forgiving, but none I know of in this price range are capable of more resolution or transparency from the midrange up.
All in all, the LM-20 is a very good speaker system for reasonably priced systems and small to medium rooms, and is exceptionally well suited to lovers of jazz groups, small orchestras, chamber music, soloists, and voice. At the same time, it has reasonable ability to deal with all but organ, heavy metal, and the Russians and Austrians in a state of bass-heavy musical heat.
The LM - 250: $1185/pair
The LM-250 is the top-of-the-line Synthesis, and competes directly with the lower priced Thiel and Vandersteens. It is a two-way system using an 8" polypropylene woofer and a 1" doped-fabric tweeter. The woofer has an exceptionally large 31 oz. magnet. The tweeter uses ferrofluid damping.
These speakers are mounted in a 3 / 4 " walled enclosure using MDF, which is heavier and denser than particle board or wood. The enclosure is deliberately narrow to improve dispersion, and the inside panel is sloped to provide time alignment and reduce standing waves. Computer testing has been used extensively to allow a combination of mounting and damping that minimizes inter-driver and driver/ cabinet interaction.
The crossover is a quasi-first order for both the transition to tweeter and woofer.
Linear phase is preserved throughout the crossover region, and the low crossover point of 1250 Hz has been chosen to reduce the normal breakup of 8" cones when used to 1500 hz and above.
The crossover is exceptional: it uses only polystyrene capacitors. Conrad-Johnson claims that these capacitors are extremely costly compared to other types, but have absorption and dissipation characteristics literally hundreds of times lower than electrolytics, about half polypropylenes, and more than five times lower than most Mylars. While the exact merits of such capacitors are controversial, few audio designers don't believe that high quality capacitors make a major improvement in speaker sound quality.
The LM-250s are heavy at 46 lbs each, and are designed for use with spiked feet.
As the British discovered several years in advance of us Yanks, spiking the speakers to the floor sharply reduces the slight movement of the speaker cabinet in response to bass vibration. This movement blurs high frequency response, and ex plains why spike feet and heavy speaker bases or mounting stands have become the rule for high-end systems.
The end result is a transparent and well focused monitor speaker with the same excellent highs as the LM-20, a smoother and more detailed upper midrange, and excellent middle and lower midrange. The bass is tight and well controlled, but lacks extension below the upper midbass. In short, the LM-250 is a more accurate version of the LM-20, with more bass energy.
It is also more demanding of associated electronics. The LM-250 is a very flat and detailed speaker. It has more depth and more realistic soundstage width and information than the LM-20 (which is no slouch), but requires electronics without grain or hardness, and a cartridge with good resolving power and no hardness in the upper octaves. The problems from CDs are clearer than usual on the LM-250s; it is not a machine for mediocre CD players.
The LM-250 mates very well with Conrad-Johnson's vacuum tube amplifiers (surprise!), although it is better suited to the power and superior upper-octave ac curacy of the Premiere Four than the MV-45 or MV--55. It also did well with the Adcom 555, and much better with the PS Audio 200CV or Krell KSA-50. It did an exceptionally good job of revealing the soundstage character of all these amplifiers, and their relative levels of resolution.
It is no speaker for the ordinary receiver or transistor amplifier: the flat upper mid range, treble balance, and amount of detail is very unforgiving, almost to the point of annoyance on such products.
I should point out that this is, in many ways, a speaker for the classical music listener, or at least the listener willing to trade accuracy for bass. It's not so much that the bass is weak, but rather that obvious tradeoffs are made between transparency and bass energy. The result is an imbalance characteristic of many of to day's better speakers: there is always more upper octave data present in the music reproduced by the LM-250s than is musically natural, because the information is not balanced by extended bass. No lover of chamber music, voice, or solo instruments is likely to object to this tradeoff (except lovers of grand piano and the more popular bassoon ditties), but many people who prefer a strong bass line may feel differently.
These tradeoffs are quite legitimate at the price point, but they make speakers like the Thiel CS-2 and Vandersteen 2C tough com petition for the LM-250. You will have to choose one designer's view of transparency over another, and perhaps choose that transparency over bass. I strongly suggest that you do this by extended listening, if possible on your own electronics. Listen to a mix of full orchestral, jazz with a strong bass line, female voice (popular, not operatic), woodwinds, and both solo and massed violins. If you're dumb enough to listen to unfamiliar demo records in choosing between speakers of this caliber, you deserve never knowing whether your choice was right.
There are other differences you may hear (more warmth and bass with the Vandersteens, better string tone than the Thiels but slightly less detail, arguably slightly less convincing woodwinds, etc.), but I suspect many of these differences will change with different cartridges and electronics. The main point, in any case, is that the LM-250s compete in transparency and overall performance with two of the best speakers in the field, and are good enough to merit close listening. You will be paying for transparency and accuracy of timbre if you buy the LM-250s, and only you can decide whether these strengths in the LM-250s are right for your system.
Author's addendum: Recent changes to the cabinet design and the tweeter surround of the LM-250 have significantly improved the speaker's airiness and imaging specificity, as well as widening the effective listening area.
Owners of very early models are advised to contact Conrad-johnson to determine if their speaker needs updating.
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[based on a March 1986, Stereophile review article]
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