Aerial Acoustics 10T loudspeaker Measurements

Suggestive of air

I measured the Aerial 10T using the DRA Labs MLSSA system (v.10.0A), an Italian Outline speaker turntable, and a B&K 4006 ½" microphone calibrated to be flat on-axis at my typical measuring distances. My estimate of the Aerial's B-weighted sensitivity was exactly to specification at 86dB/W/m. (My congratulations to the 10T's designers for not exaggerating this figure, a practice pandemic among the speaker industry, I've found.) This respectable figure implies that the speaker will play reasonably loud with an amplifier of around 100W.

Its plot of electrical impedance (fig.1), however, reveals that it sucks quite a lot of current from the partnering amplifier to achieve that sensitivity. The magnitude drops to 3 ohms or below in the midbass and mid-treble, and is coupled with a demanding electrical phase angle some of the time. I wouldn't recommend this speaker be used with wimpy single-ended amplifiers, and tube amplifiers should definitely be used from their 4 ohm transformer taps.

Fig.1 Aerial 10T, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

Fig.1 also reveals the tuning of the large port to lie at a low 21Hz, this confirmed by fig.2, which shows the individual responses of the 10T's drive-units, measured on the tweeter axis at a distance of 50" (above 300Hz) and in the nearfield (below 300Hz). The port output features a slight resonant mode at 220Hz, but this is well down in level. The woofer crosses over to the midrange at the specified 360Hz, while the tweeter takes over above 2.9kHz. However, I was surprised to see that the acoustic crossover slopes are closer to 12dB/octave, with only the midrange/tweeter filters approaching the specified 24dB/octave. The tweeter's ultrasonic resonance can be seen at 26kHz. This should be inaudible to all but bats and infants. Unusually for a metal-dome design, the unit's output in the 10-20kHz octave doesn't droop.

Fig.2 Aerial 10T, acoustic crossover on tweeter axis at 50", corrected for microphone response, with nearfield midrange, woofer, and port responses plotted below 400Hz.

The 10T's overall response on the tweeter axis is shown in fig.3. It is commendably flat through the midrange and treble, with only a slight rise in the midbass apparent. The bass is well-extended, with a calculated -6dB point of 19Hz.

Fig.3 Aerial 10T, anechoic response on tweeter axis at 50", averaged across 30 degrees horizontal window and corrected for microphone response, with complex sum of nearfield woofer and port responses plotted below 300Hz.

Vertically, the 10T's response stays basically flat as long as the listener's ears are between the top and bottom of the midrange/tweeter head-unit. Stand up, however, and a deep notch appears at the upper crossover frequency, which will make the speaker sound rather hollow. Laterally (fig.4), the Aerial features reasonably wide and even dispersion, the top audio octave not rolling off significantly until more than 20 degrees off-axis. But note the flare in the radiation pattern at the bottom of the tweeter's passband: This might tend to make the speaker sound a little bright if placed close to nonabsorbent sidewalls.

Fig.4 Aerial 10T, horizontal response family at 50", normalized to response on tweeter axis, from back to front: differences in response 90 degrees-5 degrees off-axis; reference response; differences in response 5 degrees-90 degrees off-axis.

In the time domain, the 10T's step response (fig.5) reveals that the three drive-units are all connected with positive acoustic polarity, but that the tweeter's output arrives at the ear slightly before that of the midrange, which in turn arrives before that of the woofer. The 10T's cumulative spectral-decay or waterfall plot (fig.6) shows a basically clean decay, broken only by a ridge due to the tweeter's ultrasonic resonance and a slight amount of delayed energy at 3.2kHz.

Fig.5 Aerial 10T, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

Fig.6 Aerial 10T, cumulative spectral-decay plot at 50" (0.15ms risetime).

Overall, this is a superb set of measurements for a loudspeaker from a company making its review debut in Stereophile. I'm not surprised Wes liked its sound; so did I.—John Atkinson

Aerial Acoustics
P.O. Box 81248
Wellesley Hills, MA 02181
(617) 235-7715
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