Dunlavy Audio Labs Signature SC-VI loudspeaker Page 2

A time-coherent presentation is not merely a matter of putting all your drivers in the right place. Crossover design is critical. Designing a crossover that not only permits time-coherent speaker blending—mandating the use of first-order slopes—but also compensates for the inherent nonlinearities in amplitude and phase endemic to all drivers, is no easy task.

The first step in the Dunlavy crossover design process is to test raw drivers. Not only the frequency response, but the phase response, dispersion, impulse response, and step response are tested under anechoic conditions. The resultant data are fed into a computer model to determine what enclosure dimensions and crossover will be necessary for optimal performance. While it may sound simple to implement 6dB/octave crossovers between drivers—most "how to build your own loudspeaker" cookbooks have charts listing the resistors and capacitors needed for "textbook" results—very few designers take into consideration each driver's phase, amplitude, and impedance anomalies. Dunlavy's crossovers not only correct phase problems in each driver, but also power response, vertical and horizontal dispersion characteristics, and phase shifts during rolloff. No "cookbook" crossover even begins to accomplish all this. Don't try this at home unless you have your own anechoic chamber and proprietary computer modeling software.

Many—no, most high-end speaker manufacturers point with pride to the final "voicing" phase of the design process, in which they enlist their "golden ears" to make the final adjustments to their products to make them "magic." Dunlavy believes this process is hokum. While ears can tell you if something is wrong, they can never help you put things right. Only comprehensive measurement, along with critical comparative listening (footnote 2), can determine if a speaker is accurate. Certainly musically pleasing speakers can be created by carefully "voicing" a transducer, but such products will never be accurate.

The most fascinating aspect of the Dunlavy Signature SC-VI's design is not what radical new materials and technologies John Dunlavy has brought to speaker design, but how well he has used existing technology to achieve outstanding results. While all parts are of the highest quality, including fiberglass printed circuit boards, air-core inductors, and high-Q polypropylene capacitors, nowhere in the Signature VI will you find anything exceedingly exotic. $400 tweeters and $200/foot wire are absent from inside the Signature VI, not due to their expense, but because John Dunlavy found their use resulted in no noticeable or measurable sonic improvements. Dunlavy speakers also use very little in the way of exotic drivers, since John Dunlavy feels that hi-tech materials such as Kevlar and titanium are no better at achieving perfect pistonic response than more conventional materials. As John Dunlavy is fond of pointing out, "Why pay for floobie dust?"

To confirm that all Dunlavy speakers are up to specifications, each and every speaker, from the under-$1000/pair SC-I to the SC-VI, is run through a complete battery of tests in an anechoic chamber prior to shipping. All test results are compared to a master specification set (the speakers must perform within a particular performance "window" of maximum and minimum specs), and the results are kept on file. I've seen Dunlavy's test notebooks. Sample-to-sample variations appear to be minuscule.

My review pair of Signature VIs were the first ones ever made with a cherry finish. I personally prefer it to the Dalwood rose, oak, teak, or dreaded black ash veneers. The speaker somehow seems less massive in cherry. If you are a connoisseur of piano-gloss wood finishes, you may be disappointed by the quality of the finish on the SC-VI. A few more coats of shellac and quite a bit more sanding are needed to bring their veneer up to a high-gloss level. Audiophiles who buy with their eyes as well as their ears may find the finish below par, especially compared to the wood-art produced by Avalon, Jadis, or Sonus Faber.

The Signature SC-VIs are big (over 6' tall) and heavy (530 lbs each). Each speaker requires at least four strong folks, two of whom must be professional piano movers, to get it into your home. The supplied unpacking instructions should be rigorously followed for pain-free setup. If you live in an apartment or have your listening room on the second floor of your home, I recommend you enlist a structural engineer to determine if your domicile can actually support these behemoths. Ideally, they should be situated on a slab concrete floor—anything that can not only support their weight, but also deal with their bass transients. If your room can be overloaded by low-bass energy, the Signature VIs will do it.

To perform optimally, the Signature VIs need a large room. It's not only that their physical size requires a room bigger than 24' by 20', but a listener must be at least 10' away from the drivers to achieve proper time/phase coherency.

Also, don't bother placing them in a large room without a good deal of room treatment. At the 1995 Winter CES, Krell tried using a pair of Signature VIs in a large, totally undamped room. They sounded terrible. Putting Dunlavys in an acoustically lively room is a sure recipe for sonic disaster. This speaker was designed for well-damped rooms. It throws out a lot of sound, evenly, in all forward directions. If you do not damp early room reflections, the sound will turn to mush. If you can't spend the time, money, and effort to completely damp early reflections, don't even consider the Dunlavy Signature VI. Your room must be carefully arranged around these speakers.

Footnote 2: By "comparative listening" I mean comparing a speaker's output to live music. Dunlavy does extensive "live vs recorded" tests, using his large anechoic chamber to record classical chamber music and soloists. He plays back the recordings through his speakers and compares the sound with the performers playing live between the speakers. He also records the Colorado Springs Symphony Orchestra, and uses his tapes to check speaker accuracy.
Dunlavy Audio Labs
P.O. Box 49399
Colorado Springs, CO 80949-9399
(719) 592-1159