Stereophile

MEASUREMEN­TS

Because of the SVS Ultra Evolution Pinnacle loudspeake­r’s size and bulk, I performed the measuremen­ts in Sasha Matson’s listening room. I used DRA Labs’ MLSSA system, a calibrated DPA 4006 microphone, and an Earthworks microphone preamplifi­er to measure the quasi-anechoic frequencya­nd time-domain behavior in the farfield. I used an Earthworks QTC-40 microphone for the nearfield responses and Dayton Audio’s DATS V2 system to measure the impedance magnitude and phase. The SVS speaker’s tweeter is just 32.5" from the floor. We lifted the speaker onto a small dolly for the measuremen­ts; because we weren’t able to raise it higher, I took the farfield measuremen­ts at 1m rather than my usual 50”, pushing the reflection­s of the speaker’s output from the floor back in time.

SVS specifies the Ultra Evolution Pinnacle’s voltage sensitivit­y as 88dB/2.83V/m, which was confirmed by my measuremen­t. The Ultra Evolution Pinnacle’s nominal impedance is specified as 6 ohms. The impedance magnitude (fig.1, solid trace) was lower than 6 ohms in the upper bass, midrange, and treble. The minimum impedance was 2.32 ohms at 85Hz. The electrical phase angle (fig.1, dotted trace) is high at low frequencie­s, which means that the effective resistance, or EPDR,1 drops below 3 ohms from 53Hz to 215Hz and below 2 ohms from 56Hz to 93Hz. The minimum EPDR values are 1.48 ohms at 29Hz and 1 ohm at 72Hz. As music can have high energy at the latter frequency, the Ultra Evolution Pinnacle needs to be partnered with an amplifier that doesn’t have a problem delivering current into low impedances. (I used SM’s McIntosh MC462 amplifier, which I found can deliver up to 536W into 2 ohms,2 for the measuremen­ts.)

The impedance traces are free from the slight discontinu­ities that would imply the presence of resonances of some kind. Even so, using a plastic-tape accelerome­ter, I found two resonant modes on the sidewalls, one at 277Hz level with the lower

woofers (fig.2), another at 773Hz level with the upper woofers. These modes are relatively high in level, but they have a high Q (Quality Factor); this will reduce the chance of audible consequenc­es.

The saddle centered on 31Hz in the impedance magnitude trace suggests that this is the tuning frequency of the two ports mounted on the SVS’s rear panel. However, when I looked at the individual behavior of the woofers in the nearfield, the front woofers (blue trace below 300Hz in fig.3) had the expected reflex tuning notch at 36Hz while the rear woofers’ notch (green trace) lay at 28.3Hz. The sum of the ports’ nearfield responses (fig.3, red trace) peaks at the tuning frequency before rolling off cleanly at lower and higher frequencie­s.

Higher in frequency in fig.3, the black trace shows the nearfield response of the midrange units, spliced at 350Hz to the farfield response of the midrange units and tweeter measured on the latter’s axis. The crossover between the woofers and midranges lies just above 100Hz, with each rolling off smoothly above and below that frequency. The higher-frequency units’ balance is generally even, though there is a slight lack of energy in the presence region.

This can also be seen in the Ultra Evolution Pinnacle’s farfield response, averaged across a 30° horizontal window centered on the tweeter axis (fig.4). The response is otherwise even through the midrange and high treble, and the diamond-coated tweeter’s output has a high-level resonant peak at 29kHz. The complex sum of the woofers’ and ports’ nearfield responses is shown as the black trace below 300Hz in fig.4. The peak in the bass is mostly due to

the nearfield measuremen­t technique.3

The speaker’s horizontal radiation pattern, normalized to the response on the tweeter axis, which therefore appears as a straight line, is shown in fig.5. The dispersion is generally well-controlled, though the radiation pattern narrows in the top octave. More importantl­y, the lack of energy in the presence region in the on-axis output tends to fill in to the speaker’s sides. Experiment­ing with toe-in should therefore optimize the SVS speaker’s treble balance.

Fig.6 shows the Ultra Evolution Pinnacle’s dispersion in the vertical plane, again normalized to the response on the tweeter axis. The dispersion is relatively uniform up to 10° above and below that axis, which is useful considerin­g that the tweeter is several inches below the ear height of a typical listener in a typical chair.

In the time domain, the SVS’s step response on the tweeter axis (fig.7) indicates that the tweeter and woofers are connected in positive acoustic polarity, the midrange units in inverse polarity. The tweeter’s output arrives first at the microphone followed by that of the midrange units; the decay of the tweeter’s step blends smoothly with the start of the midrange step. The decay of that step then smoothly blends with the start of the woofers’ step. This all implies an optimum crossover topology, coupled with the offset of the drivers’ acoustic centers on the curved front baffle. (Ignore the reflection­s of the speaker’s output from the floor between 6.4ms and 7ms in this graph.) Other than some low-level delayed energy at the top of the midrange units’ passband, the Ultra Evolution Pinnacle’s cumulative spectralde­cay, or waterfall, plot (fig.8) is very clean.

The SVS Ultra Evolution Pinnacle measured well, but its current-hungry impedance and lack of presence region energy on-axis will require care taken in system matching and setup.—John Atkinson 3 A nearfield measuremen­t assumes that the baffle extends to infinity in both horizontal and vertical planes, which means that the loudspeake­r is firing into hemispheri­cal space rather than a full sphere. See stereophil­e.com/content/measuring-loudspeake­rs-part-three-page-6.