Floor-standing Speakers

Anthony Gallo Acoustics Reference 3.5 Speakers

ARTICLE INDEX

On the Bench

I measured the Gallo Reference 3.1s with my M-Audio Profire 610 firewire audio interface, with a calibrated Earthworks M30BX microphone and Spectra Plus FFT analysis software. Electrical impedance was measured with a Smith and Larson Woofer Tester 2, calibrated with a 10 ohm 1% resistor.

Here, we see the measured electrical impedance presented as traditional amplitude and phase plots and on a Smith chart, normalized to 8 ohms. As with the Reference 3.1, the Reference 3.5 has widely varying impedance, particularly in the treble. The impedance of the tweeter is highly capacitive, with a magnitude that varies by a factor of 10 from 3 kHz to 20 kHz. The impedance of the 3.5 is slightly more challenging to drive than the 3.1 at low frequencies, reaching close to -50 degrees phase angle and more than 16 ohms magnitude. This very variable electrical impedance is the penalty for the crossoverless design of the 3.5, and will require an amplifier with good stability and control.

Total harmonic distortion was measured at 50 Hz, 1 kHz and 10 kHz with tones normalized to 100 dB SPL at 1m (calibrated at 1 kHz with a Radio Shack SPL meter). THD is about 2% at 50 Hz, about 0.5% higher than the Strada-TR3 combination. This seemed to be a byproduct of using the dual voice coil drive with the Reference SA amp. With this amp turned off, the 50 Hz THD dropped to about 1.5%, in line with the TR-3 measurement. At 1 kHz, the THD measured at 0.5%, a bit better than the Strada. At 10 kHz, the THD drops to 0.3%. These are very good numbers for a speaker with no active correction.

Frequency response was measured at 1m distance on-axis from one speaker, at the listening position with the speakers playing in stereo mode. The test tone was white noise at 100 dB SPL at 1m. The 1m response shows a bit of a bump at high frequencies on axis with the tweeter, a room suckout at 200 Hz, and a bit of a drop off in bass below 40 Hz. At the listening position, the response is much smoother. The treble bump is gone for the most part (there's a little bit of tilted-up treble present). The big room suckout at 200 Hz is gone, but smaller room features are present at 55 Hz, 45 Hz and 40 Hz. Bass response is more or less flat all they way to 20 Hz. For a speaker of this size and price, this performance is exceptional, particularly in the bottom octave. This is evidence of the advantage the 3.5 has over the Strada/TR-3 combination, which can't match the low frequency extension of the 3.5.