In the lab
Frequency response (at 2 meters)
front left/right: 36 Hz to 17.2 kHz ±3.3 dB
center (Stand mode): 87 Hz to 17.6 kHz ±2.6 dB
surround (Bipole mode): 115 Hz to 14.4 kHz ±2.5 dB
surround (Dipole mode): 552 Hz to 15.3 kHz ±3.5 dB
subwoofer: 37 to 82 Hz ±2.2 dB
Sensitivity (SPL at 1 meter with 2.8 volts of pink-noise input)
front left/right: 89 dB
center (Stand mode): 89 dB
surround (Bipole mode): 83 dB
front left/right: 4/6 ohms
center: 4.1/6 ohms
surround: 6.7/8 ohms
Bass limits (lowest frequency and maximum SPL with limit of 10% distortion at 2 meters in a large room)
front left/right: 32 Hz at 83 dB SPL
center: 50 Hz at 83 dB SPL
surround: 80 Hz at 89 dB SPL
subwoofer : 25 Hz at 84 dB SPL
104 dB average maximum SPL from 25 to 62 Hz
112 dB maximum SPL at 50 Hz
All of the curves in the frequency-response graph are weighted according to how sound arrives at a listeners ears with normal speaker placement. The curve for the left/right front channels reflects the 633-T's response with the speaker standing on the floor, averaged over a ±30° window with double weight at 30° (the most typical listening angle). The center-channel curve reflects the 634-VAC's response averaged over ±45°, with double weight directly on-axis of the primary listener with the speaker set to Stand mode. The surround-channel curves show the 534-SS's response averaged over ±60° in both its Bipole and Dipole modes.
I measured the center and surround channel speakers with them placed on a 6-foot stand, which gives anechoic results to approximately 200 Hz. Excepting those for the subwoofer, all measurements are taken at a full 2 meters, which emulates a typical listening distance, enables the outputs of large speakers to fully integrate acoustically, and, unlike near-field measurements, fully includes front-panel reflections and cabinet diffraction.
Towers, Center, and Surrounds
Measurements for the 633-T show excellent bass extension but also a bass bump just below 100 Hz, followed by a floor-reflection notch of equal magnitude at 200 Hz. The speaker's response also has a curious 3-dB elevation between 1.2 and 2.5 kHz, near its crossover point.
The 634-VAC's response has roughly the same character as the tower's but with 3 dB less output below 500 Hz when set to Stand mode. In Cabinet mode, output below 500 Hz is reduced by another 2 to 3 dB. Thanks to the speaker's vertical midrange/tweeter array, its response is virtually free from off-axis lobing - meaning that all listeners should experience similar sound quality.
When operated in its Bipole mode, the 534-SS surround speaker's averaged response is similar to the center speaker's but with less bass extension. In Dipole mode, low-frequency response falls off much faster - an additional 6 to 8 dB per octave below 550 Hz - and the speaker's bass limit goes to 75 dB SPL at 100 Hz. As with most bi-directional speakers, the 634-SS's response varies radically according to listening angle.
I measured the S-12 subwoofer's bass limits with it set to maximum bandwidth and placed in the optimal corner of a 7,500-cubic-foot room. In a smaller room, users can expect 2 to 3 Hz deeper extension and as much as 3 dB greater sound-pressure level (SPL).
Maximum output averaged 104 dB SPL from 25 to 62 Hz, with an absolute maximum of 112 dB SPL at 50 Hz, all within our 10% distortion limit. The S-12 will gladly make more bass if distortion is ignored, however: 101 dB SPL at 25 Hz, but with distortion greater than 100%, versus 84 dB with 10% max distortion.
Although the S-12's crossover dial is marked from 40 to 160 Hz, its actual acoustical operating range was just 70 to 82 Hz.
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