Von Schweikert Audio UniField Model Three Loudspeaker (TAS 198)

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Von Schweikert Audio UniField Model Three
Von Schweikert Audio UniField Model Three Loudspeaker (TAS 198)

As I said in my review of the Magico M5s (in Issue 196), the first obligation of a loudspeaker—or, for that matter, any piece of audio gear—is to vanish as a sound source. Thanks to its heroic aluminum-and-birch enclosures, its ultra-low-distortion NanoTec carbon-fiber-sandwich drivers, and its extraordinary (and extraordinarily expensive) elliptical symmetry crossovers, the $89k M5 does just that better than any large multiway dynamic loudspeaker I’ve heard.

Of course, there are all sorts of ways to make a loudspeaker disappear. For instance, rather than trying to force five or six cones and five or six crossovers housed in a large expensive cabinet to pull a Houdini, why not greatly reduce the number of drivers and crossovers and shrink the size of the cabinet? Magico did this very thing with its two-way stand-mount Mini and Mini II—the speakers that made the company’s reputation. With the UniField Model Three, venerable speaker designer Albert von Schweikert has (quite literally) tried to go Magico and his other two-way competition one better.

Although each Model Three looks like a miniaturized WATT/Puppy-style three-way, the UniField is what Von Schweikert calls an “augmented” one-way loudspeaker—“augmented” below 100Hz by a 7" woofer housed in its own compact, tapered, quasi-transmission-line enclosure and above 8kHz by a 3" ribbon that shares a tiny, separate, tapered cabinet with the UniField’s midrange cone. To reproduce everything between woofer and tweet, from 100Hz through 8kHz—a range of 6+ octaves that encompasses the fundamentals and most of the harmonics from nearly the lowest note of a basso (G2) to well above the highest note of a piccolo (D8)—the Model Three depends entirely on a “hand-built” 5" driver, an impregnated paper cone coated with a layer of salt-crystal-sized ceramic spheres and synthetic dampeners. As fans of planar and electrostatic loudspeakers can attest, one of the chief ways of making a loudspeaker disappear is not to cut the audio bandwidth up into little slices reproduced by different cones but to reproduce the entire gamut via a single, extremely low-distortion, extremely high-resolution, crossoverless driver. Throughout most of the musical spectrum, the UniField Three does precisely that.

Of course, the trouble with any single-driver dynamic speaker, even one as extraordinarily full-range as the UniField Three’s marvelous 5" cone, has always been the low bass and top treble. Generally, with a one-way there isn’t enough of either. Without the bottom octaves, larger-scale music unquestionably lacks foundation; without treble, music lacks sparkle and life. This is where Von Schweikert’s “augmentation” comes in. In the mid-to-low bass, the UniField’s transmission-line-loaded, long-throw, magnesium-coned woofer gives the speaker low end that no one-way I know of, and few two- or three-ways, can rival. (The UniField’s 7" transmission-line woofer is claimed to achieve 20Hz extension, down 6dB at 25Hz in free-field measurements. My own measurements—which we will come to—show it to be down about 12dB at 20Hz referenced to 1kHz, which is quite a bit better than respectable bottom-octave performance for a 7" driver in a 22" high, 10" wide, 14" deep enclosure!) On top, the UniField’s 3" aluminum-foil ribbon extends treble performance well past 50kHz.

Playing music back primarily through a single driver augmented by a deep-reaching woofer and high-flying tweeter at crossover points so low and high they are virtually “inaudible” isn’t the only disappearing trick that the Model Three has up its sleeve. Von Schweikert claims that his UniField design also has a carefully controlled dispersion pattern, said to be restricted to +/-30 degrees horizontally in the midband and treble. Achieved by “driver selection, crossover topology, and other proprietary methods,” the UniField’s narrower dispersion reduces the boundary effects of typical wide-dispersion loudspeakers, making the Model Three ideal for smaller rooms in which wall reflections tend to color timbres and play havoc with imaging. (The UniField’s controlled dispersion does not make it suitable for smaller rooms only, BTW; it does just swell in medium-sized ones like mine and, according to Von S, in larger ones too, although its smallish drivers may ultimately limit its ability to “fill” really large spaces at loud levels.) With its front-ported transmission-line bass driver (the damping of which is user-adjustable), the Three can also be placed much closer to back walls than conventional wide-dispersion speakers, including most stand-mounted monitors.

All right. We’ve got a virtual single driver speaker, and we’ve made provisions to take the imaging-and-timbre-degrading early reflections of that driver out of the question; now how about the enclosure it is housed in? As you may recall from my M5 review, building a neutral enclosure involves artfully juggling three parameters: stiffness (to push the box’s resonant frequency as high as possible), mass (to damp this high-frequency resonance and reduce its Q), and damping (to further reduce the amplitude of the resonance and kill or, in the case of a transmission line, filter the backwave of the drivers). Wolf chose to build a sealed system with an aluminum baffle (which boasts extremely high stiffness) coupled to an airtight birch-ply box (which boasts extremely high mass and damping). But Von Schweikert feels that aluminum or Corian or other “hard” materials are precisely the wrong stuff to use for speaker baffles and boxes because, says he, the drivers will ring against such hard surfaces. Instead, he builds the walls of his boxes using a tri-laminate constrained-layer sandwich of molded resin-impregnated MDF (for stiffness), artificial stone (for mass), and sheets of viscous material (for damping), bracing them internally with a “honeycomb” of MDF and more viscous damping, and stuffing them with three different kinds of absorptive materials to eliminate cavity resonances (what Von S calls Gradient Density Damping). Where Magico uses an ingenious tension-coupling mechanism to ensure that the cones are the only parts of the drivers that vibrate, Von Schweikert employs a gasket of the same synthetic clay used to damp the hulls of nuclear submarines to keep his driver frames from rattling against baffles and resonating against cabinet walls. He claims that his constrained layer, honeycomb-braced, gradient-density-damped boxes with clay-damped driver-frames reduce enclosure vibration by 300% in comparison to “conventional” enclosures, while the cabinets’ small size and tapered shape ensure low levels of diffraction and reflection.

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 Sidebar: Setting Up the UniField Model Three

The Model Three isn’t particularly difficult to set up. The tiny midrange/tweeter cabinet sits on top of the woofer cabinet at a distance from the woofer’s front baffle that ensures correct time and phase alignment. (The instruction pamphlet explains how to determine this distance.) The woofer cabinet rests on a supplied, short, spiked, T-shaped stand. There is no attachment between the woofer enclosure and this stand, and the stand itself is a bit flimsy, IMO (especially for a $15k speaker). Be sure that the crossbar of the T is facing toward the listening seat when you mount the woofers, or the whole thing can be tipped over. Depending on your room and your seating distance from the speakers, the Model Threes may need a little toe-in. The Threes must be bi-wired. Von Schweikert Audio makes two very good sets of dedicated bi-wire cables for the UniField, although their price ($2.5k and $5k) is steep. The speaker comes with extra stuffing for the transmission line, which you can use (or remove) to tailor the bass to room size and speaker placement. I tried the Model Threes with a variety of amps in two different listening spaces and at various distances from backwalls. At shows, Von Schweikert demonstrates the Model Threes with tubes, perhaps because their slightly brighter, livelier treble complements the Model Threes slightly recessive upper-midrange/lower treble. I liked the treble marginally better with tubes, and I liked the bass marginally better with solid-state. --JV

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Before we discuss the UniField’s sound, let’s look at one other direct challenge to Magico and Wilson—the Three’s hybrid transmission-line bass. According to Von Schweikert (and he’s certainly not alone in saying this), acoustic-suspension bass sounds “strangled” due to the high, energy-robbing pressures and huge impedance peaks of sealed enclosures, while ported bass sounds “slow,” “chesty,” and “one-note” due to the resonances of their hollow ported boxes, the ringing of their under-damped cones, and the mistuning of the ports themselves. His solution is a transmission line—a tunnel of four, stuffed (with Dacron), interconnected chambers, each tuned to a different frequency, which, together, spread and smooth out the bass-range resonances of the woofer’s backwave. There is nothing new about transmission-line bass—IMF and KEF were using it back in the sixties and seventies. But Von Schweikert has spiffed it up with Chebychev alignment and that nifty magnesium driver.

So…how does Albert Von Schweikert’s challenge to the Magico Mini II and Wilson Sophia 2 and YG Acoustics Kipod Studio sound? Well, the short answer is “lovely,” just as it did at the RMAF and CES shows where Robert Harley and I initially heard it. Indeed, on the very first cuts I played through the UniField Three—Alison Krauss and Union Station’s live recording of “Forget About It” (on MoFi vinyl) I was immediately struck by how realistically the Model Three reproduced Krauss’ lead soprano and Dan Tyminski’s baritone backup. Both voices were wonderfully well focused (though not at all miniaturized), completely “freed-up” from the little midrange driver and its tiny enclosure, extremely well resolved in color and texture (Krauss’s slight characteristic tremolo was as audible through the UniFields as it was through the Magico M5s or those paragons of low-level resolution, the MartinLogan CLXes), and quite persuasively “there” in the room with me. Violin, guitar, and dobro were also extraordinarily free from driver/enclosure coloration as if, like the two voices, they weren’t being projected from a loudspeaker but hanging mobile-like in open air, although each was hanging a little further back in the soundfield than what I was used to hearing through other transducers and, while sweet as sugar in timbre, each was a bit less present and brilliant than it usually sounds. It wasn’t until the electric bass came in midway through the number that I began to feel like I was hearing a driver in a box. Though deep-reaching and shockingly well-defined in the bottom octave, the UniField’s transmission line was adding a bit of woolliness to the midbass, making certain notes of the Fender sound slightly louder, less crisply defined, and more forward in the mix. The effect wasn’t unpleasant or unnatural—the bass still sounded like a bass, but the instrument was a tad louder and plummier than it sounded through the M5s or the CLXes or other systems on which I’ve auditioned this LP. On the tiptop, cymbals were every bit as clear and sweet and delicately detailed as guitars and dobro but, like both, a little recessed in perspective, softened in dynamic, and less scintillant in texture.

After listening to several other cuts—like Reiner Bredemeyer’s cantata for voice and percussion Synchronisiert:Asynchron [Nova], the Prokofiev First Violin Sonata with Nadia Salerno-Sonnenberg and Sondra Rivers [Music Masters], and a variety of larger-scale music—I began to form a clear picture of the UniField’s sound, which stayed remarkably consistent on every LP or CD: A little dark in overall balance (rather like the beautiful, liquid-sounding BAlabo electronics), with a gorgeous, boxless, natural midrange, superb midrange transient response, great soundstaging and imaging (as good as it gets, in fact), excellent very deep bass (at moderate to moderately loud playback levels), but a little thicker, louder, and boxier in the midbass than in the midband, and a little softer, less brilliant, and more laidback in the upper mids and treble than in either the midband or the bass. Where it was playing, that single 5" driver in Von Schweikert’s enclosure was superb. The trouble (if you want to call it that) was that I could clearly hear where it stopped playing—in the midbass and the upper mids/lower treble—and where the “augmenting” drivers were picking up the baton.

At this point I decided to do an RTA (a series of them, actually) and, sure enough, the speakers measured exactly the way they sounded—very slightly humped up in the midbass and very slightly sucked out in the presence/brilliance range (see above).

This is actually excellent frequency response for a quasi-“one-way” loudspeaker—exceptionally flat in the heart of the midrange, from 100Hz to 2kHz where it appears as if the 5" driver begins to slowly roll off. I imagine that Von Schweikert could have brought the tweeter in at a slightly lower frequency to fill up this slight dip in the presence and brilliance range, but didn’t want to risk drawing attention to the ribbon, as so many ribbon/cone hybrid speakers do, by ladling excess top-end energy onto his smooth-as-silk “one-way” sound. So he settled quite sensibly on this highly musical compromise. It isn’t much of a compromise in the listening. Instruments that reach up this high are just a little more laid-back in the soundstage, totally devoid of sibilance or aggressiveness (even when they are sibilant or aggressive), and a bit less naturally brilliant, airy, and harmonically complex. Oh, their harmonics are still there, but they’re being resolved at a slightly lower volume level that makes the overtones of high-pitched instruments sound very sweet but a little concentrated, like the taste of condensed milk.

The smallish hump in the midbass, where the woofer takes over from the 5" driver, is also relatively benign. As noted, you hear it as a bit more loudness and prominence on kettle or bass drum (where it very attractively accentuates the resonant bodies of the instruments) or on certain notes in ostinatos of piano, doublebass, and bass guitar—like the effects of a minor room resonance. It doesn’t greatly change the pitches or colors of the notes themselves, just amplifies and thickens them a little, slightly reducing their crispness of definition. Until you play the UniField Threes very loud—and the whole soundfield begins to compress and congest—this little midbass hump certainly doesn’t obscure the upper bass or the bottom bass, which, as noted, is shockingly deep and articulate for such a tiny driver in such a tiny enclosure, adding genuinely lifelike “finish” to truly deep bass notes. (The uncanny clarity the UniField Threes bring to the deep bullroarer rumble of the bowed bass drums in Cage’s Third Construction [New World], not to mention the phenomenally large, wide, freed-up-from-drivers-and-enclosures soundstage they throw on this cut and so many others, has to be heard to be believed from such a small transducer and cabinet.)

Albert Von Schweikert set out to produce a tiny, full-range, single-voiced speaker for small rooms that, unlike so many speakers for small rooms, would not rob you of the deep bass, imaging precision, and dynamic scale of big speakers. The design he settled on is very nearly unique—an “augmented” one-way. That you can occasionally hear the augmentation (or its effects) doesn’t change the fact that throughout most of its range the UniField really does speak with one beautiful and persuasively lifelike voice. Though the Three is not a speaker for really big spaces or for rock concerts played back at stadium levels and at $15k the pair has a good deal of serious competition, it certainly fills a niche for apartment and condo dwellers who hanker for full-range sound in a small svelte package. Though I wouldn’t call the UniField a completely neutral loudspeaker—it has, by design, a voice of its own that is robust but meltingly beautiful, superbly focused but never edgy, supremely quick but never aggressive, highly detailed but highly forgiving—it is a constant pleasure to listen to and never less than musically convincing.

SPECS & PRICING

Von Schweikert Audio UniField Model Three Loudspeaker

Driver Complement: 3-inch ribbon tweeter, 5-inch composite cone full-range driver, 7-inch magnesium cone woofer
Frequency Range: 32Hz to 40kHz (-3dB down points are 25Hz and 50kHz)
Sensitivity: 88dB @ one watt/one meter in anechoic conditions, 91dB in-room
Distortion: Less than 0.8% at normal listening level (5 watts)
Impedance: 8 ohms nominal (4 ohms minimum)
Power Rating: 300 watts peak, 100 watts RMS (minimum of 20 watts)
Weight: 190 lbs./pr. (including stands)
Dimension: 10" x 40" x 14"
Price: $15,000 (including stands)

Von Schweikert Audio
41110 Sandalwood Circle, Unit #122
Murrieta, California, 92562
(951) 696-3662
www.vonschweikert.com

JV’s Reference System

Loudspeakers: Magico M5, MartinLogan CLX, Focal Diablo Utopia

Linestage preamps: Audio Research Reference 5, Soulution 720, BAlabo BC-1 Mk-II, Technical Brain TBC-Zero

Phonostage preamps: Audio Research Reference 2, Audio Tekne TEA-2000, Lamm Industries LP-2 Deluxe, Technical Brain TEQ/TMC-Zero

Power amplifiers: Audio Research Reference 610T, Soulution 700, Lamm ML-2, BAlabo BP-1 Mk-II, Technical Brain TBP-Zero ver. 2

Analog source: Walker Audio Proscenium Black Diamond record player, AAS Gabriel/Da Vinci turntable with DaVinci Grandezza and Nobile tonearms

Phono cartridges: DaVinci Reference Cartridge Grandezza, Air Tight PC-1 Supreme, Clearaudio Goldfinger v2

Digital source: dCS Scarlatti with U-Clock, Soulution 740, ARC Reference CD8

Cable and interconnect: Tara Labs “Zero” Gold interconnect, Tara Labs “Omega” Gold speaker cable, Tara Labs “The One” Cobalt power cords, MIT Oracle MA-X interconnect, MIT Oracle MA speaker cable, Synergistic Research Absolute Reference speakers cables and interconnects, Audio Tekne Litz wire cable and interconnect

Accessories: Shakti Hallographs (6), A/V Room Services Metu acoustic panels and corner traps, ASC Tube Traps, Symposium Isis equipment stand, Symposium Ultra equipment platforms, Symposium Rollerblocks, Symposium Fat Padz, Walker Prologue Reference equipment stand, Walker Prologue amp stands, Shunyata Research Hydra V-Ray power distributor and Anaconda Helix Alpha/VX power cables, Tara Labs PM 2 AC Power Screens, Shunyata Research Dark Field Cable Elevators, Walker Valid Points and Resonance Control discs, Winds Arm Load meter, Clearaudio Double Matrix record cleaner, HiFi-Tuning silver/gold fuses

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