Snell Acoustics XA 2900 surround speaker system
Snell Acoustics has come a long way since the late Peter Snell founded the company in 1976. Now owned by Boston Acoustics and led by current head designer David Smith, it remains a small operation still dedicated to producing exceptional loudspeakers. The company's current flagship, the XA Reference, at $30,000/pair, is a far cry in sophistication and price from the first Type A ($1370/pair in 1976 dollars, as I recall), but if you look at an XA with its grille in place, it looks uncannily like a taller, narrower Type A.
The XA Reference was reviewed by Larry Greenhill in the April 2002 issue of our sister publication Stereophile (the review also appears in the Archive section of www.stereophile.com). I won't discuss that model here, but I mention it because the main subject of this review, the Snell XA 2900, is physically identical to the Tower in everything but size, cosmetics, and bass configuration. Functionally, the floorstanding Tower has four woofers and is a full-range speaker in every sense. The smaller XA 2900 responds down to approximately 40Hz.
There are two versions of the XA 2900. One, the XA 2900 Tall, is designed to be positioned vertically. The other, called the Standard, version, is configured horizontally and is intended for center-channel operation. It can be used for that purpose with a pair of XA References at the left and right or, alternately, with two XA 2900 Talls. The system used for this review consisted of the latter (left and right front), one horizontal Standard (center), and a pair of Snell's new AMC900THX dipole surrounds. This system will most often be sold with Snell's long-available flagship subwoofer, the Sub 1800 ($2500, external amplifier required). While this is a fine subwoofer, it's immense—one of the largest subs commercially available. For logistical reasons, therefore, I mated the XA 2900 system with the much more compact but highly capable Revel B15 already resident in my system.
In our July/August 1999 issue we reviewed Snell's XA 90ps system, which employs a multi-driver design that Snell refers to as an eXpanding Array, or XA. The XA 2900 uses the same technique. Briefly put, the drivers are arranged in such a way that the effective length of the array grows longer in proportion to the radiated wavelength. Translation: The system is designed to have a very even response in the vertical plane, traditionally a problem area with multi-driver systems. The XA 2900's vertical response is said to be very smooth within a range of ±15°. Beyond that, its high-frequency performance drops off, which should reduce the effects of floor and ceiling reflections.
While Snell's literature states that the eXpanding Array "has a very wide sweet spot with virtually no change in frequency response or perceived tonal balance," I'm not exactly certain why an XA should affect the horizontal sweet spot (which appears to be implied by the statement). The XA is designed to smooth the vertical response, whereas it's a speaker's horizontal response that primarily determines its imaging. Nevertheless, I found nothing to criticize about the system's soundstaging abilities.
To perform properly, the eXpanding Array requires that the drivers be mounted very close together, especially the upper ranges. The XA 2900's tweeter and two midranges are mounted on a computer-cut plate. The XA design also requires as low a mid/tweeter crossover point as possible; to accomplish that, the tweeter is set in a short waveguide that allows it to respond down to its 2.4kHz crossover point without risk of overload. While the XA Reference has a gracefully sculpted cabinet to minimize diffraction from this mid-tweeter array, the XA 2900 uses small pieces of foam positioned on either side of the drivers to perform the same function. Grilles are provided, but since they did not appear to be designed to minimize baffle reflections (quite the opposite, in fact), I did most of my listening without them (they were also left off for the measurements).
The XA 2900's cabinet is massive. Its double walls (triple for the baffle) are separated by a lossy polymer material to further reduce vibrations. A hard rap of the knuckles on the side of this speaker produced nothing more than a sore hand.
Snell speakers have always been beautifully crafted. While the XA 2900 is as well-built as any speaker I can name, and well-finished, its proportions are more than a little ungainly, particularly on top of almost any speaker stand I know of. And while the driver array will be attractive in a high-tech way to the dedicated audiophile, its appearance isn't likely to endear it to significant others. But it isn't intended to. The speaker has been designed specifically for custom installations in which it will be hidden behind a screen or in a cabinet of some sort. The latter is anathema to serious home-theater fans, since a speaker will nearly always sound best when it's well clear of walls or furniture.
But that isn't always possible. To minimize the effects of compromised positioning, Snell has designed the XA 2900 with four separate three-position adjustment switches, each of which operates in a different frequency range—Lower Mid, Upper Mid, Lower Treble, Upper Treble. For example, a boost above about 10kHz can help compensate for the losses encountered when a speaker is mounted behind a perforated screen. While nothing can fully correct for this (a perf screen is, at best, a mediocre grillecloth material), Snell has studied the phenomenon and used the results (required boosts of about 3dB at 10kHz and 6dB at 20kHz) in the design of the XA 2900's compensation switches. (The XA Reference is also equipped with similar switches, but their response range is more subtle since that speaker will usually be used freestanding and well away from nearby walls, large cabinets, and video screens.)
The switches can also be used to compensate for other setup problems, including one that I encountered. I had to place the XA 2900 center below my non-perf screen, which placed the centers of the woofers about 10 inches off the floor. Moving the two low-range switches to their negative positions minimized (though didn't always totally eliminate) a slight tendency to excessive warmth from male voices. I also ultimately set the switches of the left and right speakers the same way. The positions for the best sound in your room, however, may well be different; that's why the switches are there.