Snell Type K/II loudspeaker

In some ways, building an inexpensive yet musical two-way loudspeaker is a greater design challenge than creating a cost-no-object reference product. Although the latter is a much more complex endeavor, the venerable two-way box seems to bring out the creativity and resources of the designer. Rather than throw money at the product in the form of more expensive drivers, enclosures, or components, the designer of a low-cost two-way is forced to go back to the basics, rethink closely-held tenets, and rely on ingenuity and sheer talent to squeeze the most music from a given cost. Consequently, the inexpensive two-way is the perfect vehicle for designers to develop their skills. If one has mastered this art form, one is much more likely to achieve success when more ambitious designs are attempted.

The $465/pair Snell Type K/II represents the effort of a distinguished designer, Kevin Voecks and is the lowest-priced loudspeaker in the six-model Snell line, which culminates in the highly regarded Type A/IIIi (footnote 1). Snell has applied the same design philosophy and manufacturing methods to the inexpensive Type K/II as is lavished on the $4650 Type A/IIIi. The primary engineering goal of Kevin Voecks, designer of the Snell line, is to provide flat amplitude response (footnote 2) not just on the loudspeaker's axis, but over a wider horizontal and vertical forward window so that room boundary reflections do not have a different spectral balance that would color the loudspeaker's direct sound. The contribution of sidewall reflections to what the listener ultimately hears is significant; a loudspeaker with off-axis amplitude anomalies may measure quite flat on-axis, but have tonal colorations when placed in a room. Consequently, Snell loudspeakers' amplitude response is specified over a 30° horizontal window, not just directly on-axis. In addition, the loudspeaker's response is optimized over a 45° vertical window, taking into account floor and ceiling reflections. Flat amplitude response off-axis is achieved with higher-order crossover slopes (18dB/octave) and careful driver design.

Like other Snell loudspeakers, the Type K/II's development was heavily influenced by the testing procedures at Canada's National Research Council, headed by Dr. Floyd Toole (footnote 3). The NRC provides loudspeaker-evaluation services including double-blind listening tests, on- and off-axis amplitude measurements, and a full-size anechoic chamber. Many loudspeakers tested at the NRC share some design parameters: high-order crossovers and flat response over a wide window.

The Type K/II is very ordinary looking, except for the nice cabinet work. As soon as the veneer is cut, loudspeakers become pairs, assuring matching grain within a pair. Cabinets are hand-sanded and -oiled, unusual in an inexpensive product. All cabinetry is done in Snell's own cabinet shop. The Type K/II's enclosure is made from ¾" high-density particle-board. According to Kevin Voecks, no internal bracing was needed because of the small unsupported wall dimensions. Snell's Type K/II stands carry a suggested retail price of $98/pair.

The enclosure rear has a rectangular inset that holds two pairs of five-way binding posts. Like all Snell loudspeakers, the Type K/II can be bi-amped or -wired. Shorting bars are provided for single-wire operation. A tweeter level control is provided next to the binding posts. Where the Snell Type A/IIIi (which uses the same tweeter as the Type K/II) features a two-position switch that allows the user to switch the rear tweeter on or off, the Type K/II's rotary knob provides infinite variability over a fairly narrow range. The knob's 12 o'clock position is marked "optimal."

The Type K/II's 8" polypropylene-cone woofer, specially manufactured for Snell, uses a special surround designed to dissipate stored energy. The cone shape and dustcap are designed for flat off-axis response, the cast-magnesium basket and the voice-coil for high power handling. The tweeter is the popular Vifa 1" treated textile-dome unit found in the Dahlquist DQ-12 and Triad System Seven, both of which I've reviewed (in Vol.13 Nos.4 and 10, respectively). Despite this tweeter's rising top-end response, many designers feel that its other attributes compensate for this tendency toward excessive upper-treble output. (My primary criticism of both the DQ-12 and Triad System Seven was too much treble energy.) Crossover frequency is 2.7kHz, with third-order slopes. Air-core inductors are used throughout, and film capacitors are used where appropriate. The crossovers are hardwired into the loudspeaker, rather than connected with push-on terminals.

What really distinguishes the Type K/II's crossover (and those in all other Snell loudspeakers) is the careful matching of crossover to drivers. Because raw driver manufacturers typically guarantee ±3dB tolerance in frequency response, it is difficult to achieve production units close in performance to the prototype. Snell overcomes this problem by measuring each driver and adjusting crossover component values to compensate for driver tolerances. Crossover component values are adjusted with trimmer caps and by varying the number of inductor winding turns. The result is that each Type K/II's frequency response is within 0.5dB of the prototype. This is an extraordinarily tight production standard for any loudspeaker, much less one in the Type K/II's price range. As far as I know, this exacting procedure is unique to Snell (footnote 4).

Listening
I auditioned the Type K/IIs on the same Celestion spiked and lead-shot/sand–filled stands used with the Phase Technology PC-80s. The stands placed the Type K's tweeters 40" above the floor, 4" above ear level. After some experimentation, I listened to the speakers toed-in toward the listener, 50" from the rear wall, 36" from the side walls. Before listening to the Type K/II, I spent some time with the Spica TC-50s.



Footnote 1: Larry Greenhill reviewed the Type A/IIIi in Vol.13 No.3. His comprehensive review also includes a history of the Type A's evolution and critical reception over its remarkably long life.

Footnote 2: See TJN's interview with Kevin Voecks in Vol.13 No.3.

Footnote 3: A bound edition reprinting Dr. Toole's earlier papers is available for $3.75 (US), including postage, from the National Research Council, Division of Physics, Ottawa, Ontario K1A 0R6, Canada. These papers are essential reading for anyone interested in loudspeaker design and testing.

Footnote 4: Each pair of KEF's Reference series loudspeakers are also carefully matched in this manner, though I understand they are not matched pair to pair.—John Atkinson

Company Info
Snell Acoustics
300 Jubilee Drive, PO Box 3717
Peabody, MA 01961-3717
(978) 538-6262
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