Ryan wrote:

I first heard about these 30 inch (the diamter of the cone, not the
driver)speakers at the dreaded Full Sail (known to my fellow graduates
as "Full Male" for its serious lack of the opposite sex). While I
majored in Digital Media (web design, CD-ROM design), the first three
months of school are the same for every student. We all attended the
beginning classes at the same time, and then went our seperate ways
after three months, so I managed to learn a good bit about the
recording world. One of the professors happened to mention this in a
lecture, just as a side note.

The amount of level that a driver can produce is a function of the amount
of air that it can move. This is function of the area of the driver and
the amount of displacement of the driver (the Xmax).

A 15" driver can move about twice the air of a 12" driver with the same
Xmax (since 15^2 is about twice 12^2).

So, you can get a big driver, or you can get a driver with a very long
displacement. The Carver boxes manage to get a lot of low end out of
a small driver, since it operates like a deep piston over a very wide
range.

BUT, how low the driver will work depends on the resonant frequency of
the driver, or Fs. Speakers aren't really of much use too far below
the Fs, even with cabinet trickery. If you actually look at the numbers,
you'll find most pro audio drivers tend to be big and move a lot of air
but don't actually go very low. On the other hand, NHT makes a subwoofer
driver that is only 10" but has a 16 Hz Fs.... doesn't get very loud, but
it gets very, very deep and accurate.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."