Tower Speaker Reviews

Bottom Line

Saying that a $5,800 two-way speaker’s not for everybody might be the most obvious statement ever made in an audio review. The question is: Who is it for? The answer: audiophiles who want a really big soundstage and precise imaging, with some great bass thrown in for good measure, and who are willing to experiment with amplification to find the just-right match for the Gibbon 88.

Test Bench

Frequency response
44 Hz to 20 kHz ±4.8 dB (on-axis)
44 Hz to 20 kHz ±4.1 dB (avg ±30°)

Sensitivity (SPL at 1 meter/1 watt)
87.2 dB

Impedance (minimum/nominal)
4.8/8 ohms

Bass output (CEA-2010 standard)
• Ultra-low bass (20-31.5 Hz) average: 90.2 dB
20 Hz: NA
25 Hz: 87.6 dB
31.5 Hz: 97.0 dB
• Low bass (40-63 Hz) average: 107.8 dB
40 Hz: 108.4 dB
50 Hz: 107.6 dB
63 Hz: 107.4 dB

I measured the frequency response of the Gibbon 88 by placing it on a measurement turntable on the ground and placing the measurement microphone 2 meters away at about the height of the tweeter. I moved the mike around a bit to get the smoothest possible measurement. I also placed about 2 feet of fiberglass insulation between the speaker and the mike to absorb the bounce from the floor. I used this technique for quasi-anechoic measurements (which removes the effects of reflections from nearby objects) down to 250 Hz, averaging curves at 0°, ±10°, ±20°, and ±30° and smoothing the result by 1/12th octave. Below 250 Hz, I used ground plane technique, placing the mike on the ground directly in front of the speaker at a distance of 2 meters, and smoothed the result to 1/3rd octave. For the quasi-anechoic measurements, I used a Clio FW analyzer in MLS mode; for the ground plane measurements, I used log chirp mode.

The Gibbon 88 has smooth response overall, with a little bit of emphasis at 700 Hz (which I didn’t hear) and at 3.8 kHz (which, based on my comments about the speaker’s brightness, I did seem to hear). The upper treble energy, above about 5 kHz, seems a little low. The averaged response is actually a little flatter than the on-axis response, which indicates broad dispersion. Indeed, off-axis response is superb. Because of the asymmetrical tweeter positioning, it’s not the same on both sides, but regardless of which side I measured on, the only anomaly I saw in the curves was a slight, smooth dip of about 4 dB at 4 kHz, at both ±45° and ±60°. All of these measurements were taken without the grille; adding the grille creates only a subtle change in the sound, with a maximum effect of -1.3 dB at 4 kHz. Almost any amp can drive the Gibbon 88 to high levels with no problem. Sensitivity (average response from 300 Hz to 10 kHz at 1 meter with a 2.83-volt signal) is good at 87.2 dB. Impedance averages about 8 ohms, and drops to a minimum of 4.8 ohms at 19 kHz, with a phase shift of just +6°.

I performed the CEA-2010 output measurement at 2 meters; I added 6 dB to scale the measurements to the 1-meter reporting standard mandated by CEA-2010. Averages are done in pascals per recent amendments to the CEA-2010 procedure. A Krell S-300i integrated amp provided the power. Per CEA-2010 practice, because I couldn’t get enough output for a measurement at 20 Hz, I calculated the ultra-low bass average by subtracting 18 dB from the 25-Hz figure and using that for the 20-Hz figure.

The low bass (40-63 Hz) output is comparable to what you’d get from a very small subwoofer, like the ones included with soundbars, but of course that’s for just one speaker. For two speakers, you can add roughly 6 dB to get an approximate average output of 113.8 dB, comparable to that of a good 8-inch subwoofer and plenty for most music listening. The Gibbon 88 does have usable response down to 25 Hz, but its output drops pretty fast below 40 Hz.