François Yves Le Gal wrote:
On Wed, 14 Apr 2004 04:47:48 -0000, "Rich Andrews."
wrote:

I have been looking at various speaker designs and wondered why more
people don't build or produce vertical arrays.

Most people follow the herd.

Is it the cost involved or the size or ???

Both are limiting factors. You should add that very few system
simulation software deal with arrays, and, that, at the commercial
level, the excellent so-called "Bessel array" is covered by a number
of Philips patents.

I think that the basic Philips patents on Bessel arrays may have run out,
at least in the US.

http://www.ee.ic.ac.uk/hp/staff/pnay...philips091.pdf
is dated 1983 which makes publication at 20 years old of 18. It's probably
worth more searching at the US patent office to confirm.

There's a later Keele AES paper that points out that many of the Bessel
arrays that Phillips proposed, aren't really all that good. But the N=5 and
N=25 versions have withstood scrutiny.

BTW I built a Bessel array composed of 5 speakers earlier this year. It
worked as promised, and had very low lobing. It sounded very much like one
of the drivers it was composed of, only it could go louder. The practical
trick is finding drivers that will result in a useable system impedance.
There's a tendency to end up too high or too low.

The real practical problem with arrays is that as long as you can readily
obtain individual drivers that can handle more power, a small number of
drivers is the more economical way to go. Therefore, arrays end up being
chosen when high sound levels and/or controlled directivity are desired.
They are typically made up of drivers that already have very good
power-handling capacity.