Innovative engineering is often an iterative process At frequencies above 50Hz, the system routes
of refinement and testing. For Nelson Pass, this its output to another set of speakers — the Klein
means constructing ever-huger sound systems, Horns, so-named because they look like Klein
and then field-testing them by throwing ever- bottles (“klein” also means “small” in German). The
louder parties. Klein Horns’ massive wooden cabinets take sound
For his latest creation, Pass built speakers pressure and raise its volume acoustically by
that deliver bone-shaking volumes down beyond routing it through chambers that follow the same
the low threshold of human hearing. The lowest “exponential horn” principle as a trumpet, only for
registers are handled by a pair of sub-subwoofers sub-tuba frequencies. As with El Pipe-O, the Horns’
known as El Pipe-O, named after their resemblance dimensions are dictated by the lowest frequencies,
to an old college roommate’s beloved water pipe. the magic number being one quarter of the bottom
El Pipe-O’s acoustical properties derive from note’s wavelength, or 9½ feet for a 30Hz tone.
twin, 10-foot-tall cylinders cut from 24-inch-diam- Rounding out the system are a pair of ribbon
eter cardboard tubing, normally used to cast con- tweeters and a crossover network that directs the
crete pillars. Mounted over 21-inch (read: immense) sound to the six speaker channels. All together,
woofers, these tubes act like organ pipes. At one they produce sound that’s flat over the entire
party, Pass and his collaborators decided to test audible spectrum (and even a bit below), even at
whether the manufacturer’s peak power rating for mad volumes. —Paul Spinrad
these woofers, 800 watts, was accurate. After blow-
ing the speakers out, they concluded that it was. >>Pass DIY: passdiy.com
Photograph by Nelson Pass
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