Sidebar 3: Measurements
When I learned that Rogier van Bakel was reviewing Focal's Maestro Utopia Evo, I flashed back to the logistical difficulties I experienced when I reviewed an earlier version of this loudspeaker, the Maestro Utopia III, in July 2010. The Evo is the same size—almost 5' high—and weight—256lb—as the earlier speaker. It made sense, therefore, to drive my test gear the 500 miles to RvB's place in Maine rather than struggle with the loudspeaker's bulk at my Brooklyn home.
For the measurements, I drove one of the Focal Maestro Utopia Evos, serial number A1BPEF00543, with RvB's Krell FPB 200c. I used DRA Labs' MLSSA system with a calibrated DPA 4006 microphone to measure the speaker's behavior in the farfield and an Earthworks QTC-40 mike for the nearfield responses. It wasn't possible to raise the Maestro Utopia Evo off the floor for the measurements, so the first reflection from the ground occurs earlier than is usually the case with my measurements. I therefore measured the response and dispersion with the microphone at 1m rather than my usual 50". RvB and I moved one of the speakers away from the sidewall so that it fired along his listening room's diagonal, but it wasn't possible to measure the off-axis response more than 45° to each side of the tweeter axis.
Footnote 1: EPDR is the resistive load that gives rise to the same peak dissipation in an amplifier's output devices as the loudspeaker. See "Audio Power Amplifiers for Loudspeaker Loads," JAES, Vol.42 No.9, September 1994, and stereophile.com/reference/707heavy/index.html".
Fig.1 Focal Maestro Utopia Evo, jumpers set to Neutral, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).
Focal specifies the Maestro Utopia Evo's sensitivity as a high 93dB/2.83V/m. My B-weighted estimate was very similar, at 92.7dB(B)/2.83V/m. The Utopia Evo's nominal impedance is specified as 8 ohms. I measured the speaker's impedance parameters with Dayton Audio's DATS V2 system. The speaker's impedance magnitude (fig.1, solid trace) remains between 4 and 8 ohms throughout the midrange and treble. The minimum value is 2.5 ohms at 83Hz. This measurement was taken with the three jumpers set to their central, Neutral position. With the jumpers set to High, the port-tuning frequency didn't change, but the impedance peak in the low bass rose to 14.5 ohms. The minimum value with this setting was 2.3 ohms. With the jumpers set to Low, the minimum value rose slightly to 2.6 ohms and the low-frequency peak dropped by almost 2 ohms. The electrical phase angle (fig.1, dotted trace) is occasionally high, especially at low frequencies. The equivalent peak dissipation resistance, or EPDR (footnote 1), lies below 3 ohms between 19.5Hz and 42Hz and between 53Hz and 221Hz and below 2 ohms in several regions in the bass. The minimum EPDR values are 1.52 ohms at 26Hz, 1.48 ohms at 72Hz, and 1.675 ohms at 121Hz. The Maestro Utopia Evo is a demanding load for the partnering amplifier, though this will be ameliorated by the high sensitivity.
Fig.2 Focal Maestro Utopia Evo, cumulative spectral-decay plot calculated from output of accelerometer fastened to rear of midrange enclosure (measurement bandwidth, 2kHz).
The three enclosures seemed inert when I rapped them with my knuckles. The woofer enclosure was impressively silent. The only significant resonant modes I found with a plastic-tape accelerometer were on the midrange enclosure's top and side panels, at 320Hz and 344Hz (fig.2). However, these are of relatively high Q (Quality Factor) and the affected areas are small, both of which will work against there being audible consequences.
Fig.3 Focal Maestro Utopia Evo, jumpers set to Neutral, acoustic crossover on tweeter axis at 1m, corrected for microphone response, with the nearfield midrange (green), woofer (blue), and port (red) responses plotted below 355Hz, 355Hz, and 400Hz.
The saddle centered on 32Hz in the Maestro Utopia Evo's impedance-magnitude plot suggests that this is the tuning frequency of the downward-firing port on the woofer bin's base. The port's nearfield response (fig.3, red trace) features a broad peak between 20Hz and 90Hz, which implies extended low frequencies. The two woofers behaved identically; their summed nearfield response (fig.3, blue trace) had the expected reflex notch at 32Hz and peaked between 50Hz and 150Hz. The woofers' upper-frequency output rolls off sharply, crossing over to the midrange unit's output (green trace) at the specified 280Hz. The farfield response of the midrange unit and tweeter on the tweeter axis (green trace above 355Hz), with the jumpers set to Neutral, is even, with small, narrow suckouts balanced by equally small peaks.
Fig.4 Focal Maestro Utopia Evo, jumpers set to Neutral, anechoic response on tweeter axis at 1m, averaged across 30° horizontal window and corrected for microphone response, with the complex sum of the nearfield responses plotted below 300Hz.
The black trace above 300Hz in fig.4 shows the Focal's farfield output averaged across a 30° horizontal window centered on the tweeter axis, again with the jumpers set to Neutral. The balance is respectably even throughout the midrange and treble. With the low-frequency jumper set to Neutral, the complex sum of the nearfield midrange, woofer, and port responses (fig.4, black trace below 300Hz) has a large peak between 30Hz and 150Hz. This boost will be due in part to the nearfield measurement technique, which assumes that the drive units are placed on a true infinite baffle, ie, one which extends to infinity in both vertical and horizontal planes. But this low-frequency behavior, which I could hear with the pseudorandom MLSSA signal, does suggest that the Maestro Utopia Evo's reflex alignment is underdamped.
Fig.5 Focal Maestro Utopia Evo, lateral response family at 1m, normalized to response on tweeter axis, from back to front: differences in response 45–5° off axis, reference response, differences in response 5–45° off axis.
Fig.6 Focal Maestro Utopia Evo, vertical response family at 1m, normalized to response on tweeter axis, from back to front: differences in response 15–5° above axis, reference response, differences in response 5–10° below axis.
The Maestro Utopia Evo's horizontal dispersion (fig.5) is well-controlled, with the tweeter's top-octave output gently rolling off more than 15° off-axis to the sides. In the vertical plane (fig.6), the tweeter-axis balance is maintained 5° above and below that axis, which is useful considering that the tweeter is 47" from the floor. A suckout at 2.4kHz, close to the upper crossover frequency, appears 10° below the tweeter axis.
Fig.7 Focal Maestro Utopia Evo, step response on tweeter axis at 1m (5ms time window, 30kHz bandwidth).
Fig.8 Focal Maestro Utopia Evo, cumulative spectral-decay plot on tweeter axis at 1m (0.15ms risetime).
In the time domain, the Maestro Utopia Evo's step response on the tweeter axis (fig.7) indicates that the tweeter and midrange unit are both connected in negative acoustic polarity, the woofers in positive polarity. The tweeter's output arrives first at the microphone, followed by that of the midrange unit, then that of the woofers. The decay of each unit's step blends smoothly with the start of that of the next lower in frequency, which implies optimal crossover implementation. The Focal's cumulative spectral-decay (waterfall) plot (fig.8) was affected by the early reflection from the floor in front of the speaker, which meant I had to window the impulse response more aggressively than usual when I calculated this graph. The initial decay is impressively clean in the region covered by the tweeter, but some low-level hash is present at the top of the midrange unit's passband.
The Focal Maestro Utopia Evo's measured performance offers a full-range output coupled with wide dispersion and a neutrally balanced midrange and treble. Overall, it measured very similarly to the Utopia III, though with more of an under-damped low-frequency alignment, which will not be optimal if the speaker is used in small rooms or positioned too close to the room's boundaries.—John Atkinson
Footnote 1: EPDR is the resistive load that gives rise to the same peak dissipation in an amplifier's output devices as the loudspeaker. See "Audio Power Amplifiers for Loudspeaker Loads," JAES, Vol.42 No.9, September 1994, and stereophile.com/reference/707heavy/index.html".
