"Nousaine" wrote in message
"Arny Krueger" wrote:
Our friend Dave Clark has perhaps the most useful implementation of
the sealed-box technique using 2 18-inch drivers in, if I recall
correctly, about 4-cubic feet.
That was the point that I was introduced to the concept.
Of course, some of us use another idea popularized by Clark over a
decade ago, where no in-room floor space is required. There are
several multi driver Infinite Baffle systems in Michigan alone where
a basement or attic is used as the woofer "enclosure."
This works for people who have homes that are amenable to fairly significant
modifications.
You might think that this approach causes increased distortion at
the lowest frequencies, but as long as you don't have problems with
amplifier distortion, it doesn't have to be a problem. The
distortion produced by most subwoofers at low frequencies is
primarily due to Xmax, and this approach doesn't cause any more cone
motion than occurs in larger boxes.
This is true enough. However certain commercial applications such as
the Sunfire reach a point where is you put a large enough 20 Hz
signal you'll get more 40 Hz output (2nd harmonic louder than the
fundamental ; 100% distortion) which to many people just sounds like
"more bass."
Many low bass instruments also put out more harmonics than fundamental. If
you don't know exactly what that 16' pipe sounds like live, you may not be
able to detect massive amounts of nonlinear distortion when you play the CD.
Due to the
small box and small volume of trapped air, much more force is
required to obtain the cone motion, but that's generally not a
problem as long as the amp and the voice coil are up to handling the
increased power levels.
Simply put, this approach trades clean amplifier power which now
exists in abundance for relatively low prices, for enclosure size.
BTW, Sunfire is not the only manufacturer capitalizing on this
approach, and it has been long described in the technical literature.
By the way; the suit that Carver had against API, (and Velodyne,
Klipsch, Boston Acoustics and others) regarding patent infringement
over certain areas of this design was settled in favor of API. Thus
I'm guessing that we may see more small-sealed subwoofers operating
below resonance in the marketplace.
Low cost, high-powered amplifiers like some of the recent offerings from
Behringer make this a more practical option.