Dunlavy Audio Labs SC-I loudspeaker
Whether small or large, however, all the Dunlavy SC series conform to designer John Dunlavy's basic specification: a vertically symmetrical array of drive-units above and below a central tweeter which, coupled with careful recessing of the physically shallower drivers and the use of first-order crossover filters, results in both a time-coherent performance and a flat amplitude response on the intended listening axis at a distance of 10' or more.
The SC-I is a two-way design, with its central silk-dome VIFA tweeter flanked by two shallow-coned bass/midrange drive-units, each with a nominal 5.5" chassis diameter. The tweeter is mounted in a recess and surrounded with a thick layer of felt to minimize reflections of its output from the edges of the recess (footnote 1). The elegant enclosure is tall and relatively narrow, and veneered on all sides except the front baffle. It is made from MDF, apart from the hardwood top and bottom panels. The black jersey-cloth grille is edged with more felt in front of its radiused batons; the speaker is intended to sound most neutral with the grille in place.
The SC-I is almost completely filled with two grades of acoustic foam to help achieve the desired slightly over-damped woofer alignment (Q = 0.6). The internal wiring is Dunlavy's own cable, with push-on connectors used to power the drivers. The crossover is carried on two glass-fiber circuit boards soldered to the rear of the terminal panel (two pairs of knurled binding posts are provided to allow for bi-wiring). High-quality parts are used, including Solen polypropylene capacitors for the series feed to the tweeter and the various Zobel and equalization networks, and a big air-cored coil in series with the woofers.
The review samples supplied by Dunlavy Audio Labs were taken straight from the production line, and were not hand-chosen as being atypically good; John Dunlavy believes that for a manufacturer to do so would be basically dishonest. On the other hand, as DAL operates 100% quality control and guarantees pair-matching to within about ±0.5dB up to 15kHz, the chance of any one pair of SC-Is sounding different from any other pair must be small!
Setting the SC-Is up on 24" stands straight out of the box in the room positions that I generally have found to work best with small free-space speakers—the Spica TC-60s, for example—proved disappointing. The balance, while neutral through the upper midrange and treble, was excessively lean, with a shelved-down bass. But before I started experimenting with position, I read the comprehensive owner's manual.
There it was, on page IV-4, paragraph D: "The driver's 'free-air resonance'...is directly related to the combined moving mass...and the mechanical compliance of the suspension system. Since [the suspension] is usually fabricated of an impregnated cloth or foamed-plastic material, whose 'mechanical stiffness' becomes slightly more compliant as it vibrates and flexes over time, usage tends to gradually lower the resonant frequency of the driver—a desirable trait that improves, to a small degree, a loudspeaker's performance."
Although the drive-units receive some break-in at the factory, DAL suggests it takes about 12–15 hours for the woofers to reach their specified 80Hz bass-tuning frequency. Accordingly, I ran them in on the pink noise and swept-tone track from the XLO/Sheffield Lab Test CD at 6V RMS for 12 hours before I did any serious listening (footnote 2). The playback level for the pair would have been a neighbor-disturbing 95dB, but I wired the speakers out-of-phase and faced them toward each other, a couple of inches apart. In this way, though the drive-unit suspensions are being mechanically worked, almost all the acoustic output cancels. The cancellation was excellent, confirming DAL's claims for close pair matching. What sound is left is mainly radiated from the enclosures; it was interesting to note that this was dominated by frequencies in the middle of the midrange: 500–700Hz. Perhaps this was an indicator of the SC-I's cabinet resonant behavior (see later).
Well, after a day of muted whooshing sounds, I set the speakers back where they'd been and put on the new Peter McGrath–engineered Mahler First Symphony on Harmonia Mundi (HMU 907118). The lower-midrange/upper-bass was now more fleshed out than it had been before. While this will always be a rather light-balanced loudspeaker, it no longer sounded lean'n'mean. The power region of the orchestra was reproduced in pretty good measure, with the big bass-drum whacks at the start of the fourth movement superbly well-defined. Ultimately, however, I moved the speakers closer to the wall behind them. This did bring up the midbass, but too close to the wall and the speakers' superb soundstaging was compromised. SC-I owners should experiment carefully here—mere inches can mean the difference between perfect and paltry sound. But with the SC-Is some 15" in front of the LP shelves, the bass drum in the Mahler had a satisfying mix of leading-edge clarity and weight to the body of its tone. Perhaps also because I was now sitting a little farther away, the upper mids now seemed slightly better integrated with the treble.
Putting the bass to one side, the area where the SC-I did perform better than almost any speaker I've had in my listening room—even the $8000/pair B&W Silver Signatures—was in the solidity of the stereo images it produced. In this respect, this inexpensive speaker seemed as good as my memories of the much more expensive SC-IV. Centrally placed vocalists seemed to hang in space just in front of the plane of the speakers. Was this palpability of image accurate? It must have been; "stereophonic" is derived from the Greek word stereos, meaning solid. More solid is more better, right?
On the "Mapping the Soundstage" tracks on Stereophile's Test CD 2 and our forthcoming Robert Silverman Concert CD (see November, pp.68–75), the soundstage was as accurately and stably defined as I've ever heard. The sound of the voice and handclaps in each case could be heard to take the path expected from the microphone technique used, with very good image depth. This is excellent performance.
Footnote 1: John Dunlavy holds the US patent (No. 4,167,985, dated 9/18/79) for the use of acoustic absorbing material to control diffraction around drive-units.
Footnote 2: Logistical problems meant that I actually had to perform the measurements before I did any listening to the SC-Is. I refrained from doing the analysis of those measurements until after I had formed my opinion of the speaker's sound quality, however.