Floor Loudspeaker Reviews

I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Focal Aria 936's frequency response in the farfield, and an Earthworks QTC-40 for the nearfield responses. The Earthworks microphone has a small, ¼" capsule, and so presents minimal obstruction to air flow in the ports. For logistical reasons, I measured a different sample from those auditioned by Robert Deutsch. The speaker was bolted to its plinth for the measurements, so that the downward-firing port was the specified distance from the floor. All measurements were performed with the grille removed.

My estimate of the Focal's voltage sensitivity was 89.5dB(B)/2.83V/m—close to the specified 90dB, and usefully a little higher than average. The Aria 936 is specified as having a nominal impedance of 8 ohms and a minimum impedance of 2.8 ohms; my measurement (fig.1) confirmed the minimum value at 108Hz, but as the impedance stays below 4 ohms from the upper bass though the lower midrange, where music has high levels of energy, I would recommended using a amplifier rated into 4 ohms with this speaker.

The small wrinkle at 22.9kHz in the impedance traces indicates that this is the frequency of the metal-diaphragm tweeter's primary breakup mode. The traces are otherwise free from the midrange discontinuities that would suggest the presence of enclosure resonances. Nevertheless, investigating the cabinet walls' vibrational behavior with a plastic-tape accelerometer uncovered modes at 234, 332, and 344Hz. These resonances were lowest in level on the sidewalls (fig.2) and highest on the rear and top panels, where their effects will be less audible.

The Focal's impedance-magnitude trace has a clearly defined minimum value at 40Hz, which would be the tuning frequency of the port in a reflex design; however, with its three woofers and two ports, the Aria 936's low-frequency behavior is complicated. Fig.3 shows the nearfield responses of the midrange drive-unit (black trace), top woofer (blue), middle woofer (green), bottom woofer (red), front port (purple), and bottom port (gray), all with their levels plotted in the ratios of their radiating diameters. The midrange crosses over to the three woofers at around 150Hz, though the top woofer rolls off a little slower in the midrange than the lower two woofers. The middle and top woofers appear to be loaded by the front-firing port, with very similar minimum-motion notches in their outputs at around 44Hz. The bottom woofer's minimum-motion notch occurs slightly lower in frequency, at 39Hz. Both port outputs are commendably free from midrange resonant peaks.

The complex sum of these nearfield responses, taking into account both acoustic phase and the different distance of each radiator from a nominal farfield microphone position, is shown as the trace below 300Hz in fig.4. A large part of the upper-bass peak apparent in this graph will be due to the inevitable exaggeration of the nearfield measurement technique. But with the overlap between the outputs of the three woofers and the midrange drive-unit in the same region, it is hard to escape the conclusion that the Aria 936 will have too much upper-bass energy in all but very large rooms. I note that Bob Deutsch found that the Focal's bass sounded extended, but without the low frequencies sounding "boomy or bloated," which suggests that the woofer alignment is on the overdamped side. Though the tuning frequencies of the ports bracket 40Hz, close to the frequency of the lowest string of the electric bass and double bass, RD did comment on the Aria 936's excellent low-frequency extension; I suspect that this is actually related to the speaker's exaggerated upper bass.

Higher in frequency in fig.4, the 936's midrange and treble are extraordinarily smooth and even. The rise in response due to the tweeter's primary diaphragm resonance occurs above 15kHz, and it can be seen that there is a sharply defined antiresonance above 20kHz, but below the frequency of the tweeter resonance. A loudspeaker's perceived tonal balance depends not just on its frequency response but also on how that response changes off axis. Fig.5 shows the Aria 936's horizontal radiation pattern, referenced to the tweeter-axis response. Despite the midrange drive-unit's relatively large radiating diameter, there is only a relatively slight off-axis flare at the base of the tweeter's passband, and the contour lines in this graph are evenly spaced and uniform. As is always the case with a 1" tweeter, the output falls off to the sides above 10kHz, but this will not lead to a lack of top-octave air in rooms of normal size. In the vertical plane (fig.6), a suckout at the upper crossover frequency occurs 10° above the tweeter axis, but as the tweeter is a high 43" above the floor, this will not be a problem. The average ear height for a seated listener is 36" from the floor, so it's just as well that the upper-frequency suckout doesn't start to develop until 10° below the tweeter axis.

Turning to the time domain, the Focal Aria 936's step response on the tweeter axis (fig.7) shows that the tweeter and midrange drive-units are connected in positive acoustic polarity, the woofers in inverted polarity. But more important than the individual drive-unit polarities is the fact that the decay of each unit's step smoothly blends with the start of that of the next lower in frequency. This suggests optimal crossover design, given the different distance of each unit's acoustic center from the microphone position. RD commented on the Aria 936's superb transparency, which is what I would have expected from the clean decay seen in the speaker's cumulative spectral-decay plot (fig.8).

The Focal Aria 936's measured performance would not be out of place in an expensive loudspeaker. That it costs just $3999/pair makes it an extraordinary value.—John Atkinson