The Fifth Element #25

Wilson Benesch, distributed in the US by The Sound Organisation, is a Sheffield, UK-based engineering firm that made its début in the audio world by making a tonearm from carbon fiber. (See Jonathan Scull's report on his visit to the WB factory in December 1996, Vol.19 No.12).

Someone who responded to an online survey on Stereophile's website nominated Wilson Benesch as a worthy company whose products have been neglected in the pages of Stereophile. That caused me some measure of chagrin. I'd pretty much dedicated my January 2002 column to WB's radical Discovery loudspeaker (Vol.25 No.1). I also prominently covered WB's more conventional Arc (November 2002, Vol.25 No.11), and had a pair of their next-to-top-of-the-line Chimeras here for quite some time, preparing for my column recommending stereo systems at various price points for actress and lingerie model Rebecca Romijn-Stamos (May 2002, Vol.25 No.5). By the way, I later saw Romijn-Stamos in Femme Fatale. Does she kiss her mother with that mouth? Criminy. And she seemed like such a nice girl. Were fair Rebecca ready to lay out serious long green on a two-channel system, the Chimeras were right there at the top of the list.

Wilson Benesch's first loudspeaker, the A.C.T. One (A.C.T. stands for Advanced Composite Technology), was introduced in 1994. It won 12 awards, and was selected as the reference loudspeaker for two audio journals published outside the US. The One was followed in 1997 by the A.C.T. Two, which was slightly larger and nearly half again as expensive. (The Ones cost about $10,000/pair, the Twos about $15,000.) I believe that Wilson Benesch remains the only manufacturer to use carbon-fiber composite as a structural element in a loudspeaker enclosure. When, five years ago, I first heard and wrote about the A.C.T. One (The Abso!ute Sound, No.119), I had been aware of carbon-fiber composite only from racing yachts and open-wheel racing cars.

The A.C.T. One and Two have since been discontinued in favor of a new speaker, somewhat confusingly called the A.C.T. (Perhaps they should have christened it the Just Plain A.C.T.) The good news is that the new speaker costs $12,500 in the US, which is $2500 less than a speaker it replaces in the line. The US price is also lower than the A.C.T.'s suggested retail price in the UK, translated into today's weak dollars.

The hallmarks of Wilson Benesch's "house sound" are extremely low distortion, seamless coherence, unfussy easefulness, rounded liquidity of tone, articulate dynamics, and seductively natural imaging and soundstaging. I think there are five major technical factors that contribute to making all these benefits possible.

• Carbon fiber's combination of low mass, high rigidity, and high self-damping results in an enclosure that contributes very little degradation in terms of time smear or ringing.

• In addition to enhancing rigidity, the cabinet's sloping top and curved shape reduce diffraction effects and make room placement less critical.

• The use of nearly identical drivers for the bass and bass-midrange—which makes the A.C.T. a 2.5-way design rather than a three-way—would seem to make dispersion more uniform (or, more precisely, make the rate of change of dispersion more uniform), and the transition between those two drivers harder to perceive. (The bass driver's cone is slightly more heavy and stiff than the midrange driver's; the voice-coils are also different.)

• Closely related to that, the A.C.T.'s crossover is very simple, aiming for the least possible compromise of phase integrity. The crossover's bass-driver section has one inductor, which rolls the woofer off above 500Hz. The bass-midrange driver sees all the same bass from the amplifier as does the bass driver, but its slightly lighter cone and higher port tuning are said to give it an acoustical low-bass rolloff. The bass-midrange driver section of the crossover (again) has one inductor, rolling it off at 5000Hz. The tweeter crossover is a simple first-order design that rolls in at 5000Hz; the tweeter's bandwidth is supposed to extend to 30kHz (-6dB).

• The use of a high-quality silk-dome tweeter avoids the problems potentially associated with out-of-bandwidth ringing from metal or exotic-material treble drivers. While I admit that people cannot hear steady tones above some frequency, I remain convinced that the ear/brain system does in some way respond to transients in the high-harmonic range. "Keeping the bad stuff up where people can't hear it" is not a design goal I find myself instinctively agreeing with.

The A.C.T. One was the most strikingly elegant loudspeaker I had ever seen. Simply beautiful. It was about 42" high, 9" wide, and 14" deep. Its top was of solid cherry, tapering from rear to front. The front panel consisted of an alloy baffle in which the drivers were mounted, and, below that, furniture-grade cherry veneer. The side caps (vertical corner pieces) were solid cherry. Viewed from in front and above, the A.C.T. One had a front-to-rear shape reminiscent of a boat's prow, a bouzouki, a balalaika, or a bishop's miter: square at the bottom, the sides gently curving to meet a rounded point, which was the speaker's structural "spine." The side panels were made of glossy-black quilted carbon-fiber composite, the first such use in a loudspeaker.

I could easily envision a pair of A.C.T. Ones fitting right in in a model room at the Winter Antiques Show, surrounded by Biedermeier furniture, Persian rugs, and old oil paintings. Or, for that matter, in an austere loft. The styling was a neat hybrid of hi-tech and early 19th-century fruitwood-and-black.

The new A.C.T. is the same size and shape—the same entire "look"—as the One, but with the internal volume of the larger Two. That bit of legerdemain was accomplished by replacing the older speaker's internal structural bracing, formerly made from wood-based composites, with a unitary assembly of laser-cut welded steel. Furthermore, while the older speakers used separate carbon-fiber panels for each side, the new A.C.T.'s carbon-fiber structure is a continuous monocoque in a U-shape or arch design. Wilson Benesch claims that the A.C.T. has the stiffest structure ever employed in a floorstanding loudspeaker system. As might be expected, the new speaker is heavier than was the One, at about 100 lbs. The review pair's side endcaps were finished in Regal Silver, while the tops were high-gloss black. The black fabric grilles are held on by elegantly machined posts.

The A.C.T.'s 7" bass and bass-midrange drivers are Wilson Benesch's proprietary Tactic drive-units, which have basket structures machined from solid metal billets, and cones made from isotactic polypropylene. This driver was first developed for, and at first exclusively available in, the company's flagship model, the Bishop. (The original A.C.T. One's drivers were sourced from ScanSpeak.) The tweeter is a new hand-painted silk-dome unit. Its mounting plate has a crescent shape cut out of its lower edge, in order to bring the tweeter's center closer to the bass-midrange driver's center.

The A.C.T. uses its predecessors' unique, cantilevered design of an intermediate plate plus a base plinth. The rear spikes attach to the steel intermediate plate; the front spikes attach to the base plinth proper. The A.C.T. also has a double-ported enclosure. One port is at the bottom, above the steel intermediate plate. There is also a small port near the top of the rear "spine." I gather that this is more along the line of pressure release for the midrange driver. The manufacturer specifies a -3dB point of 35Hz.

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