A Matter Of Diffusion Page 4

The Particulars
I'll begin with the clearest success story: the KEF 107s. In the untreated soundroom the much-praised 107s betrayed a blare and honk that deepened my appreciation for unalloyed silence. After finding the speakers and the supplied equalizer (the KUBE) to be in proper working order, I got a feeling worse than buyer's remorse: I felt I'd been saddled with a patient with severe personality disorders---and one that was hard to move, took up valuable floor space, and cost me a fair chunk of change into the bargain. When the diffusors were deployed it was as if the patient had undergone electroshock therapy. A ratty blare gave way to a sweetness and harmonic balance of which I had never thought the speaker capable. Violins and violas shed their pinched, hollow sound; and the brass---jeeminee, I about wore out the preamp's mute switch every time they started that insufferable blatting and hooting---actually bore a commendable similitude to the real thing. The soundstage virtually uncorked itself, opening up in all dimensions, and the clumping of instruments around the speakers gave way to a handsome delineation of placement along all three axes---left/right, front/back, and up/down. The whole room seemed acoustically and infectiously energized. Especially on orchestral, big band, and Dire Straits-type pop music, the effect was big, fleshy, and compelling. If not in quite the same league as the admittedly much more expensive WAMM, Infinity IRS, or Apogee Diva systems, the 107s began to sound like they deserved some of their glowing press and word-of-mouth accounts. During one listening episode, a customer who had heard the 107s in the room's pre-RPG days walked in and asked, incredulously, "What did you do to those things?"

I'm going to lump the Apogees and Magnepans together---ah, what strange bedfellows acoustics make---not because I'm ignorant of their political differences, but because the diffusors are. Being dipolar line-source designs, both are sensitive not only to rear and side wall proximity, but to the physical attributes of those walls as well. Highly absorptive surfaces like Sonex or Owens-Corning acoustical panels rob the speakers of their characteristic lively, expansive sound, while plain reflective walls can impart a "slap" that creates an interesting but sometimes unnatural spatial effect. If you want the best from them, you seem forever consigned to fussing with their placement. With diffusors in place, the hard slap gave way to a more evenly distributed foldback of the rear wave into the room. Here I mean "evenly distributed" in both the tonal sense (viz, no erratic or spiky colorations) and the spatial one (eg, no more listening-position hot spots). The Divas offered a ferocious grip on the music coupled with a rich ambience---almost a "wraparound" effect---that seemed to deposit the listener nearer the stage, but in a larger and more acoustically inviting space. It seemed the overall energy level had been turned up. The change affected the very way one experiences music. The urge to dissect the sound gave way to just basking in it. Recordings like Gary Karr's Albinoni Adagio, the old Rachmaninov Symphonic Dances on Vox Turnabout, and Ernest Bloch's Schelomo on Mercury Living Presence unfurled a concert-hall acoustic you wanted to reach out and touch. Once-submerged details of orchestration and phrasing were presented with a tangibility that often brought a new sense of proportion and wholeness to complex orchestral music. On many recordings, music flowed with a rolling or "speaking" quality with the Diva/RPG combination. Certainly I have never heard Apogees anywhere to rival the hall-type glow that music regained with the Divas played in the diffusor-treated soundroom.

With the Scintillas, Duettas, and MGIIIas, the diffusored systems improved markedly, yet it must be said that never were the speakers "transformed" into sounding like something else---such as Divas or Quads or Acoustats, for example. Rather, they were clearly themselves, minus some familiar warts, and stretching out in a friendlier and more exciting space. With all three, musical images appeared to move off the surface of the speakers and into the room, where they assumed more realistic shapes and positions. It should be noted that the diffusors also ameliorated a dry middle-treble range on the MGIIIas, yielding a fuller, more harmonically natural lighting to violins, violas, clarinets, and trumpets. Owners of the various Apogees and Magnepans (and other dipolar line sources) will likely find that a cluster of RPGs on the walls behind and around the speakers will facilitate placement of these otherwise fussy monoliths.

In the untreated soundroom the Booth Curvefront IIs---$3500 hand-finished beauties resembling the Dahlquist DQ-20s or the larger Keveks and employing a choice selection of Dynaudio drivers---had suffered a lack of top-to-bottom tonal consistency that bordered on discombobulation. Powerful and "physical" nearly throughout their range, they unfortunately never allowed one to settle in and unwind with the music. They displayed an unhappy knack for taking a recording with a full soundstage, collapsing it into two small boxes, then megaphoning what was left of it into your face. With the RPGs, the Curvefront IIs were a somewhat different animal, with a generous and sometimes downright comfortable presentation, and at least hinting at an octave-to-octave seamlessness that had previously seemed far away indeed. The megaphoning gave way almost to a dipole-like ability to illuminate all corners of the room effortlessly. A nasal, ringing coloration subsided, bringing a more natural timbre to male voices of all types, from Fischer-Dieskau and Hermann Prey to Johnny Hartmann and Mick Hucknall (Simply Red). The change---"transformation," rather---was strikingly effective, and again I suspect that, given normal, sheetrock sidewalls, the Booth's significant off-axis energy output had previously exaggerated and distorted their true midrange potential.