Towers, Center, and Surrounds

This system is attractively styled, but its measured performance was mediocre. The CM7, CM Centre, and CM1 all show a depression between 1.4 and 4 kHz at every radiating angle and that worsens as the angle gets wider. With the port plugs out, all three show a bump between 100 and 200 Hz, and the CM7 also has a 3-dB floor-bounce notch at 300 Hz.

Inserting the supplied foam plug into the CM7 tower's port (which partially blocks it) dramatically changes the cabinet tuning, cutting low-frequency output starting around 200 Hz: The speaker's output was reduced by 2 dB at 100 Hz and 10 dB at 60 Hz, and the low end of its usable frequency response went from 39 to 84 Hz. Interestingly, inserting the plugs for the other speakers had little effect on their static frequency response, perhaps a function of their much smaller cabinet volumes. But the measured bass limit, which was practically unaffected by plugging the port in the CM7 (less than a full dB), was altered by the plug in the two smaller speakers, presumably because of the loss of the port's output, which normally would reduce the woofer excursion required at very low frequencies.

Subwoofer

I measured the ASW 750 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).

SPL capability is impressive in the critical 40- to 62-Hz frequency range, and the subwoofer maxed out at 109 dB (within our 10% distortion limit) at 62 Hz. Output fell at 21 dB/octave below this point, however. For its low-end bass limit (again, with 10% maximum distortion), it produced a true 25 Hz at 92 dB.

The ASW 750 has limited upper-frequency response, with the half-power point at 103 Hz when the low-pass filter is bypassed and only 79 Hz when the crossover is set to a marked 180 Hz. Measurements showed that the true acoustical range of the crossover-frequency control is only 50 to 79 Hz, despite dial markings that run from 40 to 180 Hz. There is significant level interaction as the control is moved downward in frequency (over 10 dB), so users must be sure to double check and adjust the level after making adjustments to the crossover. The sub's EQ option cuts output starting at 50 Hz and below, attenuating by up to 10 dB at 20 Hz. The protection circuit on the subwoofer also limits the output, with loud cracking noises emitted when the subwoofer is driven into overload.

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