One very big boom in an unexpectedly small package.
After a long year of periodic building and waiting for money or parts, I finally had a subwoofer that could credibly perform an earthquake simulation without moving so much as a millimeter while doing it:
Figure 25. The completed subwoofer, ready to rumble.
I have no precision performance measurements. However, by ear and by the clipping indicator under sine testing, I can say that it hits pretty hard down into the low 20s before losing power. The amplifier, as built, is only able to deliver about 225W into the 4Ω driver at the onset of clipping but that is plenty with a driver this size.
The sub matched perfectly to a pair of home-brew 2-ways I was using at the time. Those were built around sealed boxes and 8" woofers with good results, but rolled off somewhere in the high 30s. These were later biamped using ESP's P3A amplifier, and the complete system had stronger, cleaner response across the 25Hz-20kHz frequency band than anything else I had heard at the time.
Thus ended a long, fun, and sometimes tedious project, but it was worth the carefulness that went into the design. In spite of its novice aspects, the subwoofer was still working perfectly more than two years later. Someday I may revisit this project and clean up the loose ends, but unlike some of my other early projects, there were no pressing reasons to rebuild this one right away. §
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