Wilson Audio Specialties Duette loudspeaker Measurements
Sidebar 3: Measurements
A mid-March visit John Marks and I made to Derry, New Hampshire, retailer Fidelis provided an opportunity for me to give the Wilson Audio Duettes a listen in John's Rhode Island room on my way back to New York. As I'd taken along my portable speaker-measuring gearEarthworks QTC-40 microphone, Metric Halo ULN-2 FireWire audio interface, and MacBook laptop running SMUG Software's FuzzMeasure programI also examined the Duettes' in-room response. The speakers were driven by the Parasound Halo JC 1 monoblocks, as they had been for some of JM's auditioning.
I performed this in my usual manner: I average 20 1/6-octavesmoothed responses taken for each speaker individually in a rectangular grid measuring 36" by 18" and centered on the positions of the listener's ears in his chair. The resulting response correlates well with a speaker's perceived tonal balance, I have found.
The Duette's spectrum, shown as the red trace in fig.1, reveals four features. First is the smooth, gentle rolloff above 5kHz, which is due both to the increasing directivity of the 1" tweeter in its top octaves and to the increasing absorption of the room furnishings. This doesn't mean the speaker sounds rolled off; I agree with John Marks about the speaker's top-octave balance being optimal. Second is a slight lack of energy at the top of the woofer's passband compared with the regions below and above. This is the result of the relatively large woofer's radiation pattern narrowing at the top of its passband, contrasting with the wider dispersion of the tweeter at the bottom of its passband.
Third, the lower midrange is suppressed a little compared with the level in the upper midrange. I believe that this is a factor of the speakers being used well away from room boundaries rather than on bookshelves, where boundary reinforcement would tend to fill in this region. Finally, though there are slight peaks and dips between 50 and 300Hz in this trace, due to room modes that have not been eliminated by the spatial averaging, the transition through the lower midrange and upper bass is otherwise smooth, and the speaker offers useful output in-room down to 30Hz. This is excellent bass performance for a two-way bookshelf design.
The blue trace in fig.1 shows the response of the Vivid B1 in JM's room, taken under identical circumstances, other than being driven by an Ayre Acoustics integrated amplifier instead of the Parasound monoblocks. Being a three-way, the Vivid can use a smaller-diameter, hence wider-dispersion midrange driver than the Duette's 8" woofer, which results in a smoother in-room output in the upper crossover region, with otherwise a similar top-octave balance. The Vivid's double-woofer arrangement gives greater low-frequency extension in-room, but with a less well-managed lower-midrange transition overall and a "lumpier" bass output.
When I listened to the Duettes, I was as astonished by the speaker's resolution as JM had been. Hearing the CD version of Shelby Lynne singing the title track of her Just a Little Lovin' (Lost Highways B0009789-02, our March 2008 "Recording of the Month"), I was made aware of something I hadn't heard before: some very low-level analog-tape print-through in the pause before she begins each verse. (Though, to be fair, most of my experience of this track is of the LP, which seems free from this problem; perhaps the CD was mastered from a duplicate tape that had been stored "heads-out.") The Duette's low frequencies were also first-rate: extended, with perhaps a slight midbass excess, though with superb definition. The use of a larger-than-usual woofer for a two-way bookshelf design gives optimal bass performance, in terms of both sensitivity and power handling.
The Duette was not quite as uncolored as the Vivid B1, which I auditioned in both JM's and my rooms. There was a slight nasality to Shelby Lynne's and Norah Jones's voices. This character was not audible in male voices, but, like the Duette's rather forward sound, stemmed, I feel, from the speaker's in-room behavior at the top of the midrange. I found I could reduce the audibility of the coloration by opening the drapes that JM had to the left speaker's sides, which had been closed for the measuring and my initial auditioning. This suggests that the Duettes should be used well away from the sidewalls. Overall, however, the Wilson Audio Duettes produced a sound that allowed all the music I listened to during my visit to communicate very effectively.John Atkinson