Posted by Wayne Parham [ 70.234.106.31 ] on January 25, 2008 at 10:34:55:

In Reply to: Re: You've got mail! posted by Roland on January 25, 2008 at 05:27:00:

There are some basic differences between the two subs. The three π sub is a direct radiating reflex cabinet with Helmholtz frequency of 20Hz. The 12π hornsub is a push-pull folded horn with 1/4λ path length frequency of 30Hz.

The LAB12 woofer is a good driver, but its motor is a fairly common ferrite structure without a shorting ring. In the three π cabinet, excursion is lowest when the sub is used above 20Hz. Below that frequency, excursion and distortion rise rapidly.

The 12π basshorn subwoofer has three mechanisms that reduce distortion. One is push-pull drive, which works at all frequencies in the passband, but only reduces even numbered harmonics. The second mechanism is horn loading, which reduces excursion in the passband (above 30Hz), which in turn reduces distortion above 30Hz. The third thing is the front chamber and horn folds provide a low-pass filter that attenuates high frequencies, and that results in a reduction of harmonics from third on up.

The difference in output is about 15dB too. While that's not an indicator of quality all by itself, the fact remains that you need about 50x the power for the three π to equal the output of the 12π. So the 12π is loafing where the three π might be nearing its limits.

The three π is tuned lower, so that's the one area where it will perform better. You'll get flat response down to 20Hz. It is also a much smaller box.

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