Test Bench for the Web: Infinity Cascade Speaker System

In the lab

Frequency response (at 2 meters) front left/right: 77 Hz to 16 kHz ±3.7 dB center: 94 Hz to 16 kHz ±3.8 dB surround: 94 Hz to 15.2 kHz ±3.8 dB subwoofer: 35 to 140 Hz ±2.6 dB

Sensitivity (SPL at 1 meter with 2.8 volts of pink-noise input) front left/right: 86 dB center: 87 dB surround: 84 dB

Impedance (minimum/nominal) front left/right: 4.2/13 ohms center: 3.8/12 ohms surround: 4.1/13ohms

Bass limits (lowest frequency and maximum SPL with limit of 10% distortion at 2 meters in a large room) front left/right: 80 Hz at 84 dB center: 80 Hz at 87 dB surround: 80 Hz at 84 dB subwoofer: 25 Hz at 80 dB SPL 101 dB average SPL from 25 to 62 Hz 109 dB maximum SPL at 62 Hz bandwidth uniformity 92%

All of the curves in the frequency-response graph are weighted to reflect how sound arrives at a listeners ears with normal speaker placement. The curve for the left/right front channels reflects the Model Nine's response with the speaker standing on the floor, averaged over a ±30-degree window and double-weighted at 30 degrees (the most typical listening angle). The center-channel curve reflects the Model Three C's response averaged over ±45 degrees with double weight directly on-axis of the primary listener. The surround-channel curve shows the Model Five's response averaged over ±60 degrees. Both the Model Three C and Model Five were measured on a 6-foot stand, which gives anechoic results to approximately 200 Hz. Except for subwoofers, all measurements are taken at a full 2 meters, which emulates a typical listening distance, allows the outputs of large speakers to fully integrate acoustically, and - unlike near-field measurements - fully includes front-panel reflections and cabinet diffraction.

Front & Surround Speakers The Model Nine's frequency response shows a 5-dB floor-bounce notch centered at 203 Hz (not unusual) and a fair degree of irregularity at higher frequencies (including a 1.4-dB elevation between 2 and 3.5 kHz). Although the tweeter resonance at 23 kHz doesn't show in the trace, a narrow, deep notch at 20 kHz is evident in all traces and becomes more severe as the microphone is moved off-axis. The other center and surround speakers share this basic response shape (sans the floor bounce), but the Model Three C center speaker's output exhibits off-axis lobing at ±15 degrees that becomes progressively worse at wider listening angles. Typical of modern small speakers, all three have relatively limited low-frequency capability.

Subwoofer I measured the Model Twelve 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 up to 3 dB greater sound-pressure level (SPL).

When I drove the Model 12 through its LFE input, its output exhibited a surprising out-of-band peak at 450 Hz that was only 8 dB below the passband level. (It would be highly unusual for the subwoofer to receive a signal through that input with content at such a high frequency, however, so the peak should not matter much in practice.) The acoustical crossover frequency closely matched the markings at each end of the crossover dial (140 Hz at the150-Hz mark and a true 50 Hz at the 50-Hz indication). But at Noon on the dial (no marked frequency) the acoustical crossover frequency was 60 Hz, showing that nearly all the crossover action occurs in the top half of dial rotation. I found only a moderate amount of level/crossover interaction (+3,-2 dB).

SPL (sound-pressure level) capability is limited at 25 Hz, but the Model Twelve will put out a minimum of 104 dB SPL at 32 Hz and higher frequencies. The raised button dials for the RABOS room equalization feature are much easier to use than the recessed set screws found in older models, and the Quick Retest tracks on the RABOS CD are a welcome addition. There is a great amount of interaction among the Frequency, Width, and Level adjustments, however, and it will be practically impossible to set the RABOS by ear, so the charting accessory, test CD, and sound-level meter will be required.

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