Dunlavy Audio Labs Signature SC-VI loudspeaker Measurements
As with some other monster speakers—the JMlab Grande Utopia in May '96, for example, and the Jadis Eurythmie II in March—the SC-VI's size and weight precluded measuring it in Stereophile's listening room, where I routinely perform speaker measurements. (Generally speaking, to perform an acoustic measurement in a room requires the room to be very much larger than the loudspeaker.) But in the case of the big Dunlavy, the fact that the company is based in Colorado Springs—a mere six-hour hop by car over the Raton Pass from Stereophile World HQ in Santa Fe, New Mexico—suggested a strategy. If Muhammad couldn't come to the mountain, the mountain could overnight with Muhammad.
Accordingly, I drove up to Dunlavy Audio Labs and measured the speaker in the larger of the company's two anechoic chambers. The DRA Labs MLSSA system was the same as I usually use, though the microphone was a calibrated B&K 4133 rather than Stereophile's B&K 4006. (On a previous trip, I had measured a Rogers LS3/5a in the same chamber with both mikes, to check how close they were.) To forestall any criticisms of favoritism, John Dunlavy (after showing me where everything was) disappeared and allowed me to make to make my measurements free from influence. However, I would like to take this opportunity to thank John's staff for physically setting the test speaker up in the chamber.
The SC-VI's impedance magnitude and electrical phase angle are shown in fig.1. The value varies very little over the audioband, with maxima of 5.3 ohms at 28Hz and 5.6 ohms at 300Hz, and minima of 4 ohms at 60Hz and 2.76 ohms at 11kHz. Note also the low phase angle; the speaker quite closely approximates a 4 ohm resistor in its electrical characteristic. Coupled with a high sensitivity, around 91dB/2.83V/m, the SC-VI is not a hard load for an amplifier to drive, provided it is rated into 4 ohms.
Fig.1 Dunlavy SC-VI, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).
The SC-VI's on-axis frequency response, taken at the recommended minimum microphone distance of 10', is shown in fig.2. Astonishingly flat, it meets ±1dB limits from 200Hz to 20kHz. In the bass, the limitations of the Dunlavy Audio Labs anechoic chamber make the data unreliable below 200Hz or so, so I've spliced the nearfield response to the curve in this region. It can be seen that the SC-VI is basically flat to 30Hz, with a somewhat overdamped nature, rolling of to -5dB at 20Hz. This particular sample hadn't had many hours on it; it would be expected that the 15" woofer suspensions would loosen up with continued play, giving a still well-damped response but with a little more extension.
Fig.2 Dunlavy SC-VI, anechoic response on tweeter axis at 10', with nearfield woofer response plotted below 100Hz.