A Matter Of Diffusion Page 5
With or without the companion powered subwoofer (the 2W), the Vandersteen 2Cs have always sounded coherent and believable in the main soundroom. Pushed to around 98dB or more, though, the upper midrange/lower treble begins to "trumpet" and coarsen---an effect owing to either limitations of drivers or room acoustics, I could never clearly determine. The RPGs revealed the blame to be with the room, not the speakers. With the full diffusor complement the Vandersteens showed that they can be pushed quite hard in a large-ish room without distress. (A good test for this is the Vaughan Williams Tallis Fantasia, Nimbus CD 5019.) The diffusors did not seem to alter the specificity of the 2Cs' already sharply drawn images, but they wrapped these images in a larger, warmer, and more alive space. They also suppressed a slight "a" (as in "cat") coloration in the speakers, previously evident at moderately loud levels and up. These were unambiguous improvements: On a purely commercial level, we found sales of 2Cs to increase dramatically during the evaluation period. The diffusors had no detectable effect on the sound of the matching subwoofer, but did reveal the supplied crossover unit, with its 8-switch blocks, to be wholly unsatisfactory. (Vandersteen suggests using it only to establish the correct capacitor value, then ordering that specific value in a single-value, in-line package.)
Imaging on the Spendor SP1s has always been strong at center-fill, even without toeing-in; with the diffusors in place the space around instruments seemed to expand literally, well past the side walls. The speakers seemed to energize the room's entire air space, not just the area between and behind the speakers themselves. As with the Divas, Vandersteens, and Quads, the diffusors often seemed to escalate the overall musical energy level in the room. The diffusors did not alter the SP1s' characteristic upper-bass "plumminess," which probably issues from the speaker's thin-wall cabinet construction rather than dispersion problems or room interaction per se. The Spica TC50s fared similarly, sounding far bigger than they look, and again seeming to drive the 4500 cubic feet of listening room with relative ease. This effect was also clearly in evidence when I substituted a modestly powered integrated amp, the British Fidelity A1. With diffusors, treble reproduction sweetened tonally and deepened spatially.
Now we come to the puzzler---the $17,000 Waveforms. Looking like nothing so much as a chopped-and-channeled pyramid in the Art Deco style, this 200-lb. bruiser is based on research done at the National Research Council's facility in Ottawa, Canada. Furniture designer John Otvos---a charming young fellow from the old school---decided to leave his imprint on the speaker architecturally rather than sonically. For the sonics he sought Paul Barton of the NRC, requesting a design that, on the NRC's kind of controlled, double-blind listening tests, would consistently outscore all competitors. No constraints were placed on driver technology, parts costs, or enclosure design. Barton's prescription is surprisingly conventional: a 15" woofer, two 6-inchers, a soft-dome tweeter, and ribbon supertweeter. An active crossover is supplied, and the speaker must be biamped. This was the first time Otvos had played the speakers in a US dealer's showroom, and he worried aloud about the effects the RPGs might have on the sound. Having experienced positive results with all other speakers, and having considered the supporting technical rationale, I wondered if Otvos wasn't voicing a preliminary objection in order to later dismiss the auditioning results if they turned out unfavorable. We played the speakers---the Levinson No.23 on top, the stout Bryston 4B on bottom---and found that Otvos had not worried in vain.