Von Schweikert Audio UniField Model Three Loudspeaker (TAS 198)

First Class One-Way Ticket

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.