YG Acoustics Anat Reference II Professional loudspeaker Measurements
I measured the YG Acoustics Anat Reference II Professional's behavior mainly using DRA Labs' MLSSA system with a calibrated DPA microphone and an Earthworks Zero Distortion preamplifier. Because of the bulk and mass of the two woofer sections, I could perform a complete set of acoustics measurements only on the 108-lb upper-frequency Main Module. The woofer measurements were performed in situ in Wes Phillips' listening room, as was my reading of the speakers' spatially averaged response. For these measurements I used SMUG Software's FuzzMeasure 2 running on an Apple PowerBook, in conjunction with a Metric Halo ULN-2 FireWire audio interface and a calibrated Earthworks QTC-40 microphone.
The Anat Reference II's voltage sensitivity was significantly higher than average, at an estimated 90.1dB(B)/2.83V/m, though it is a little lower than the specified 92dB. The impedance is specified as 4 ohms, with a 2.7 ohm minimum. However, while our sample was basically a 4 ohm design, the magnitude did drop to almost 2 ohms in the mid-treblewhich is why WP felt the tubed VTL amplifiers lacked sparkleand below 2 ohms above 25kHz (fig.1). The phase angle also varies widely, and the combinations of 4 ohms magnitude and 53° capacitive angle at 110Hz, and 4.8 ohms and 46° at 2.4kHz, mandate the use of a power amplifier that can deliver unrestricted amounts of current. As the Main Module is not fed from a crossover when used with the woofer modules, the former magnitude/phase combination will be unaffected.
Fig.1 YGA Anat Reference II Main Module, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)
The upper (passive) woofer module's impedance (not shown) featured a minimum value of 3 ohms at 200Hz, again requiring use with an amplifier capable of providing high currents. Of course, when used in the Reference II Professional, the upper woofer is driven by the amplifier housed in the lower woofer module, so that will not be a concern.
While the passive woofer module's impedance plot (not shown) indicated the presence of some midrange resonances, those in fig.1 are free from the discontinuities that would suggest the presence of cabinet resonances. Indeed, investigating the vibrational behavior of the metal enclosure's panels revealed an almost entirely nonresonant behavior: the only mode I could find with an accelerometer was on the side panel at 652Hz, but was well down in level (fig.2). It is also high enough in frequency that it will not have any audible consequences.
Fig.2 YGA Anat Reference II Main Module, cumulative spectral-decay plot.
Fig.3 shows the individual responses of the Anat Main Module's tweeter (red trace) and woofers (blue), spliced to the woofer's nearfield output below 300Hz. The latter's peak at 3dB in the upper bass is entirely due to the nearfield measurement condition. The satellite's woofer tuning is therefore maximally flat, with a 6dB frequency of 75Hz, the same as that of the magnitude peak in the impedance plot (fig.1). When used on its own, the Anat Main Module may well sound a little light in the bass. Higher in frequency in fig.3, the crossover can be seen to be set at 1750Hz, as specified, with symmetrical acoustic slopes close to 18dB/octave. Both the tweeter and the twin woofers are impressively flat within their passbands.
Fig.3 YGA Anat Reference II Main Module, acoustic crossover on tweeter axis at 50", corrected for microphone response, with nearfield response of woofer (blue) plotted below 300Hz.
On the left of fig.4 are shown the nearfield responses of the bottom, powered (Professional) woofer module (red trace) and the upper, passive (Studio) woofer module (blue), driven by the amplifier in the lower module. (The crossover settings were those chosen by Wes Phillips rather than the ones YGA's Dick Diamond had used when he set up the speakers in WP's room.) Despite the different enclosure shapes, the two woofer modules offered identical frequency responses, both being down 10dB at 20Hz. The upper woofer module's impedance plot suggests that the sealed-box loading is tuned to the relatively high frequency of 45Hz, which in turn suggests that YGA is using equalization to extend the module's output below resonance. While peaks were evident in both woofer modules' responses at the frequencies of the midrange peaks in the impedance plot, the crossover suppresses these to more than 40dB below the reference level, in which case they should have no audible consequences. The crossover, as adjusted by WP and allowing for the nearfield boost in the satellite's output, is set to 75Hz, with asymmetrical slopes. The Main Module's frequency response, averaged across a 30° horizontal window centered on the tweeter axis (fig.4, black) is extraordinarily flat. Enough said!
Fig.4 YGA Anat Reference II, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response (black), with nearfield responses of upper (Studio) woofer (blue) and lower (Professional) woofer (red), with Main Module woofer response plotted below 300Hz (black).
The Anat Reference II's horizontal dispersion is shown in fig.5. Other than a very slight off-axis flare between 5 and 7kHz, the contour lines in this graph are evenly spaced, and the output increasingly but gently slopes down in the highs with increasing off-axis angle, which is textbook behavior. The short waveguide around the tweeter dome results in the drive-unit's output rapidly dropping off-axis above 12kHz. Only younger listeners might be bothered by a lack of air in the Anat Reference's in-room balance, however. The upper-frequency dispersion in the vertical plane (fig.6) is wide and even, but the use of spaced twin woofers results in severe upper-midrange suckouts more than 20° above or below the tweeter axis. For the most even balance, the listener's ears do need to be pretty much on the tweeter axis.
Fig.5 YGA Anat Reference II, lateral response family at 50", normalized to response on tweeter axis, from back to front: differences in response 905° off axis, reference response, differences in response 590° off axis.
Fig.6 YGA Anat Reference II, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 455° above axis, reference response, differences in response 545° below axis.
Fig.7 shows how these quasi-anechoic measurements added up in WP's listening room, again with woofer settings by WP rather than Dick Diamond. The Anat Reference II Professional's spatially averaged response at the listening chair is superbly flat, falling within ±1dB limits from 300Hz to 7kHz. Above that region, the speaker's output smoothly slopes down, due to the increasing absorptivity of the room's furnishings at higher frequencies in conjunction with the fact that WP sits relatively distant from the speakers. Below 150Hz, the peaks and dips are the residual effects of the room's resonant modes that have not been eliminated by the spatial averaging. It appears that WP set the level of the powered woofer modules a little high, but he was probably doing so to get the midbass region in the correct balance with the upper frequencies, and accepting the effects of the consequent boosts in the upper and low bass. Certainly the low-bass boost is not going to be much of an issue, given how little energy there generally is below 30Hz in music, Kanye West and Bach's organ works notwithstanding.
Fig.7 YGA Anat Reference II, spatially averaged, 1/6-octave response in WP's listening room.
In the time domain, the Anat Main Module's step response (fig.8) indicates that the tweeter and woofers are all connected with the same acoustic polarity. The decay of the tweeter's step is smoothly integrated with the start of the woofers' step, correlating with the excellent frequency-domain integration of their outputs shown in fig.4. As usual, the tweeter output leads that of the woofers. I haven't shown the woofer modules' step responses, as the polarity is adjustable with a rear-panel control. Overall, the cumulative spectral-decay plot is superbly clean (fig.9).
Fig.8 YGA Anat Reference II Main Module, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).
Fig.9 YGA Anat Reference II Main Module, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).
In its ads, YG Acoustics states that the Anat Reference II Professional is "The best loudspeaker on Earth. Period." Its impressive measured behavior doesn't detract from that claim.John Atkinson