Wilson Audio Specialties X-1/Grand SLAMM loudspeaker system
By Martin Colloms   •   December, 1994 How can a reviewer possibly put a value on a loudspeaker as costly as the Wilson Audio Specialties X-1/Grand SLAMM? When he reviewed Wilson's WATT 3/Puppy 2 system ($12,900-$16,000/pair, depending on finish) a few years back (footnote 1), John Atkinson said that it was "one of the more expensive loudspeakers around." The Grand SLAMM costs almost five times as much!

On the other hand, we've all heard about the legendary Wilson WAMM system, which costs a staggering $130,000. At a mere $65,000, the X-1 could be regarded as something of a bargain, especially as it's said to provide a performance envelope approaching that of the bigger, more expensive speaker. Even so, the new Wilson system costs way more than most enthusiasts can afford. (According to Stereophile's most recent reader survey, the average price of a complete high-quality audio system is around $11,700.)

Other big, costly speaker systems represent their designers' attempts at achieving the state of the art. In historical order, we have the Infinity IRS in its various incarnations, the Goldmund Apologue, the MartinLogan Statement, the Apogee Grand, the Genesis I, and the B&W Nautilus. Reviewing such systems can be something of a contest between designer and critic: Can the former win over the latter by the quality of his work alone, regardless of price?

To judge by his WATT/Puppy design, David Wilson of Wilson Audio Specialties is a formidable opponent. I lost the battle several years ago when I bought a pair of WATTs/Puppies for my own use.

The X-1/Grand SLAMM
X-1 stands for the "First eXperimental" system of this type, and SLAMM for "Super Linear Adjustable Modular Monitor." "Super Linear" derives from Wilson's own design target: to make the system subjectively distortion-free over a wholly natural and realistic dynamic range. "Adjustable Modular" reflects the user's control of drive-unit delay, hence system phase accuracy.

What exactly do you get for your $65,000? A pair of imposing, 6'-tall, impressively engineered loudspeaker systems, each containing seven moving-coil drive-units ranging in diameter from 15" to 1". The speaker is finished like a fine piano in black mirror-gloss varnish. (Alternative auto-finish colors, such as Mercedes Gold, may be ordered; a range of veneered side panels is also available.) Together, the two enclosures weigh about half a ton; when I spiked them to my floor, they partly sank into it.

Following the idea that the proportions of the X-1 should roughly follow those of the WATT/Puppy, albeit on a larger scale, the speaker looks slim.

The SLAMMs exert a definite presence in any room; it's definitely a case of beauty being in the eye of the beholder. Responses elicited from visitors ranged from "No way!" to "Superb functional beauty," with "Engineering as art" noted along the way. Silent, the X-1s stand like monoliths, their dark silhouettes reminiscent of the black transmitter on the lunar surface in Kubrick's 2001. But feed them audio signals in electrical form and one's view changes—the resulting sound quality has power and beauty.

The claimed performance envelope approaches that of the WAMM. Key X-1 features include easy, trouble-free use with a single pair of input terminals (see below); and a comparatively kind amplifier loading. This speaker has a very high dynamic range, typically capable of 120dB spl at 1m with a music-related peak program input of 350W—well within the compass of the Krell KSA-300S, for example. The high sensitivity (95dB/W, 8 ohms) is as equally important as the high dynamic range; pretty decent 102dB in-room sound levels will be possible from 20W of single-ended triode power, even if the speaker could never be driven to full stretch by such a source.

Technology
The X-1 is a pure example of the art of loudspeaker engineering—its form truly follows its function. Those requirements inherent in its design concept are realized without compromise, the angled, faceted surfaces of the functional, structural elements accented by their mirror-gloss finish.

The foundation of the design is the generous bass system, the lower of the two modules of the stack. Everything starts here: contact with the floor, the reference plane for the mid and treble enclosures, and, last but by no means least, the location and support for the bass drivers themselves. Above 30Hz, the bass range is handled by two large moving-coil drivers, a 15" and a 12", working in tandem. Instead of the usual four-point mounting, eight Allen-head bolts securely bind the drivers to the rigid enclosure.

Why do two differently-sized bass units share the same enclosure? They don't. Subcompartments in the bass enclosure have specific damping and air-flow control elements graded to ensure the appropriate acoustic power sharing between the two drivers. Working as a pair, they're equivalent to a single 18" woofer, but the combo chosen by Wilson has far superior transient control and maintains higher quality into the low midrange—necessary in view of the overlap required for the first-order crossover (see below).

The considerable enclosure-panel area of such large speakers potentially increases the cabinet's ability to re-radiate unwanted resonant energy. Setting reference standards for low panel resonance and coloration in such a large enclosure is a daunting task; a designer must work much harder than he or she would on a more modest system's far smaller panel area.

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Footnote 1: June 1991, Vol.14 No.6, p.171, with a correction of the measured on-axis response in Vol.14 No.10, p.205. In addition, David Wilson has been interviewed twice in Stereophile: by J. Gordon Holt in January 1985 (Vol.8 No.1, p.94), and by John Atkinson in June 1990 (Vol.13 No.6, p.78). [A third interview, with Wes Phillips, was published in Vol.18 No.11, November 1995.—Ed.]—Martin Colloms