Company Address: 7320 Hollister Ave., Goleta, Cal. 93117.
I have known Sao Win for a long time, as we both live in the same city and are heavily into audio. About two years ago, I helped him test some of his speaker prototypes. I was taken by the astonishing resolution of his speakers, though it was accompanied by some edginess and irritation when listening with source material and electronics I knew to be good. Further refinement of the diaphragm materials and adjustment of the crossover eliminated the irritation while leaving the resolution and transparency intact. I've been lucky enough to get a pair of the Win Research Group's final version to listen to for an extended period.
I am now getting the most incredibly musical and realistic sound that I have had so far in my home. The SM-10 speakers are so good that although the differences between amplifiers and other electronics are clearly audible, they don't seem to matter as much as with other speakers I have lived with.
Among the CD equipment used to listen to the Win Research SM-10s was a Krell MD-1 transport feeding a VTL Straight Line D/A converter going into the wonderfully transparent First Sound Reference II passive signal se lector and attenuator. Records were played with an Oracle turntable fitted with a Well Tempered Arm and Spectral Audio MCR-1 Select pickup feeding an EAR Head step-up transformer and a tube phono preamp. Power amplifiers used were a pair of Quicksilver M135 prototype mono tube amps, the fabulous Carver Silver Sevens, and a very good little switching amplifier de signed by my good friend and mentor, Mack Turner.
How realistic is the SM-10's sound? Imaging is wide and deep, and recording spaces and boundaries are revealed with newly perceived precision. Tonal accuracy and resolution of musical details are simply stunning-and all this with very low amounts of harshness and irritation! The only complaint I have is that the bass doesn't go down deeper. Its quality is excellent, how ever, and is very good down to a perceived 40 or 50 Hz in my room. (I will try various subwoofers in the near future.) After living with the SM-10s, if I had to opt for lesser reproduction above 60 Hz in order to get good low bass, I wouldn't make that trade.
The fit and finish of these speakers is classic Win. Sao Win is such a perfectionist that he worked with the company that finishes the enclosures for months until he was satisfied with the perfection of the black lacquer.
What are some of the technologies that make such an outstanding speaker? First, the transducer unit is a flat-plane coaxial design whose woofer is a ring radiator with an outer diameter of 6 1/2 inches and about a 3-inch inner diameter. The flat-plane tweeter diaphragm is mounted inside that 3-inch circle. By "flat-plane," I mean that the woofer and tweeter membranes are approximately in the plane of the front surface of the enclosure. This arrangement eliminates the tunneling and diffractive effects of having a tweeter located back at a conventional cone's apex, as in other coaxial designs, and helps to improve the alignment of the two radiators in time.
The woofer diaphragm is driven nod ally (about halfway between its center and outer diameter) by a voice-coil of very large diameter, and it is laminated from thin layers of woven carbon fiber and a silica-gel catalyst, compressed under high temperature and pressure.
The result is a moving assembly of surprisingly low mass, some 29 grams.
Very high damping of breakup modes above the woofer's operating range is another important benefit of this construction technique.
The tweeter diaphragm is also flat and is a disc about 1 inch in diameter.
This disc is made out of mica and alumina ceramic and is, like the woofer, compressed under high pressure and temperature. The resulting diaphragm is nodally driven, like the woofer. This tweeter's suspension has considerably more excursion capability than I have seen in other tweeters. Win Research says that this tweeter diaphragm has 10 times the bending stiffness and twice the internal damping loss of titanium.
Considerable research and computing went into the magnetic design of the drivers. The magnetic material used is Alnico 8. In my experience, the use of Alnico magnets in speakers makes them sound fast and accurate.
Last, but certainly not least, is the die-cast basket and frame assembly of the coaxial driver unit. It is made of an inert aluminum/zinc alloy.
Beneath the enclosure's beauty is design technology as extensive as that used for the drivers, including the use of computerized finite-element analysis to reduce and optimize vibration. The material used in the enclosure is Medex, 1 1/4 inches thick, with complex internal bracing. The driver assembly is mounted to some of the internal braces rather than the front panel itself.
All edges of the enclosure are rounded with a large radius, to eliminate diffraction radiation.
The stands are an integral part of the SM-10 system and were designed especially for these speakers to get the transducer up at listening ear height.
Special "Neural rubber" isolation mounts decouple the speaker from the stands.
Mounted on the rear of the stand legs is the passive crossover unit. The crossover is outside of the enclosure to reduce vibration effects on the cross over components and to eliminate any magnetic coupling from the drivers.
This crossover has two sets of inputs, for bi-wiring the speakers to amplifiers.
The crossover's electrical characteristics and the drivers' electromechanical characteristics yield a net fourth-order low-pass roll-off for the woofer, mated to a second-order high-pass characteristic for the tweeter, at an effective crossover frequency of around 3.5 kHz. The quality of the components in the crossover is first-rate, with Litz-wire inductors used along with all film capacitors. The damping resistors are made in semiconductor TO-220 cases with little finned heat-sinks to dissipate heat! At $6,250 a pair, these speakers are not cheap, and they certainly won't appeal to all buyers looking at speakers in this price range. For many, however, I firmly believe that the SM-10s' compelling honesty and realism will make the price worth it. For my part, I have not enjoyed reproduced music as much as I have in the recent months with the SM-10s. When my editor asked if I would send the pair that I have to Audio for photography, my heart stopped momentarily and I quickly said to myself, "No way, Jose!" I couldn't bear the thought of being without them!
-Bascom H. King
(adapted from Audio magazine, Jul. 1992)
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