Subwoofers

Crystal Acoustics TX-12SUB THX Ultra2 Certified Subwoofer

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Crystal Acoustics TX-12SUB THX Ultra2 Certified Subwoofer On the Bench

Following my normal protocol, all bench tests were performed with the Crystal sub in the middle of the room, to avoid interaction with corners and walls. Except as noted below, all measurements were taken from one foot at a height equal to the center of the speaker.

Some comparisons to the THX-12SUB Select sub are worth noting. Distortion vs. output at 100 decibels and 31.5 Hz is essentially identical for both subs. I measured the Select sub at 108 db with only 3.9 THD+N, but didn't push it farther. I was not as timid with the Ultra2 sub, and at 31.5 Hz reached 110.7 decibels before bumping up against 10% THD+N. Keep in mind that 3 decibel increase required a doubling of power.

The difference in low-end extension between the TX-12SUB and the Select2 certified version was more pronounced. The THX Select sub was rated by Crystal to 35 Hz, a somewhat conservative figure as I measured 10% THD+N at 27 Hz.

However, the Ultra2 certified TX-12SUB is a completely different animal. It measured below 10% THD+N all the way down to 12 Hz.

Crystal Acoustics lists 15 Hz as the bottom of its useable output, and I wondered just how much oomph it could deliver at that subsonic level. Would you believe 98 decibels of 15 Hz output under 10% THD+N! Plus, the first odd-order harmonic (at 30 Hz) barely registered 50 decibels, while the second-order harmonic (at 45 Hz) was at 78 decibels. Since our ears tend to interpret odd-order harmonics as harsh unpleasant sounds, the predominance of even-order harmonics is yet another positive test result for the TX-12SUB.

Here are the in-room response graphs, the frequency dip corresponding with room-based nulls as the microphone (simulating the listening position) moves farther out into the room.