Sidebar 3: Vandersteen Seven Mk.II Measurements
As the Mk.II Model Seven loudspeaker differs only in detail from the original Model Seven, I refer you to the measurements sidebar that accompanied Michael Fremer's review for the overall picture. I performed only a few measurements on the updated version. Fig.1 shows its electrical impedance and phase, taken with the two pairs of binding posts in parallel. This is generally similar to that of the Mk.1, and, like that speaker, drops to a low value at the top of the audioband, particularly with the rear tweeter turned on. The minimum magnitude is 2.55 ohms at 17kHz, but between 80Hz and 12kHz the impedance remains within more reasonable limits of from 4 to 7 ohms, with a generally low phase angle. The peak at 62Hz indicates the tuning frequency of the front-mounted 7" woofer.
The rear tweeters were turned off for this measurement; you can see that the Model Sevens have lower levels of mid-treble and top-octave energy than the Carmels, conforming more closely to the optimal upper-frequency rolloff in my room. (What you don't want to see in this kind of measurement is a flat treble response, which corresponds to a rising on-axis output in this region.)
Finally, like its predecessor, Vandersteen's Model Seven Mk.II offers a true time-coincident output, due to the stepped-back subbaffles for the upper-frequency drivers, the first-order crossover slopes, and the fact that all its drive-units are connected in positive acoustic polarity. Richard Vandersteen strongly believes that a loudspeaker should faithfully preserve the waveform produced by the power amplifier, including "all of the delicate time-domain relationships that comprise the recorded musical performance." Fig.3 shows the left-channel speaker's step response at the position of my ears in the listening room—although it is subsequently disturbed by room reflections, the initial arrival is an almost textbook right-triangle shape. Goal achieved.—John Atkinson
Fig.1 Vandersteen Model Seven Mk.II, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).
The red trace in fig.2 shows the spatially averaged response of the Model Seven Mk.IIs in my listening room. As usual, I generated this graph by averaging 20 1?6-octave–smoothed responses taken for each speaker individually in a vertical rectangular grid measuring 36" by 18" and centered on the positions of my ears in the listening chair. I used an Earthworks QTC-40 omni microphone and a Creative E-MU0404USB audio interface, in conjunction with SMUGSoftware's Fuzzmeasure 3.0 running on my MacBook Pro. The blue trace in this graph shows the spatially averaged response of the YGA Carmel Two speaker, which I reviewed in December 2015, taken under identical conditions. The two different speakers have broadly similar measured responses between the upper bass and the mid-treble, though the Vandersteens have less energy at the bottom of the midrange. The Model Seven's powered subwoofers extend their output to 20Hz, though even with the settings of the 11-band equalizer chosen by Richard Vandersteen when he set the speakers up in my room, the low bass is a little too high in level, the midbass a little too low.
Fig.2 Vandersteen Model Seven Mk.II, spatially averaged, 1/6-octave response in JA's listening room (red); and of YGA Carmel Two (blue).
Fig.3 Vandersteen Model Seven Mk.II, step response on upper-midrange axis at JA's listening position (5ms time window, 48kHz bandwidth).
