Posted by: "Curt Olson"
> I'm having a hard time visualizing it from your description alone, but
> would like to know more.
Here's a photo of the Crown prototype dish I have, it's the smaller of
the two sizes they tried:
http://frogrecordist.home.mindspring.com/Crown_WSA_Proto3-6.JPG
The direction to the subject you are recording is the way the connector
is pointed, i.e. you pick up from one edge of the dish. The mic is not
centered in the dish, but offset slightly.
The bigger one was reported to be able to pick up across a football
field. Here's some from the Crown mic memo on several versions. The dish
I have is the deeper version, may even be different from any described
below:
PZM Dish
A different type of boundary is a blown bubble boundary which we call
the =93dish.=94 The earliest versions
were a mere 6" in diameter with a depth of about 1". The
cantilever/capsule was mounted on the
concave surface near the center (Figure 6). These dishes did not provide
much more than the standard
plates mounted on stands, so nothing more was done with them for a while.
Fig. 6: The PZM Dish, designed by Mike Lamm of Houston, Texas.
In 1981, I built ten dishes 12" in diameter and 2" deep. Dave Johnson
used these with the San Diego
Symphony. He considered the results a great improvement over the
traditional free-field microphones
he had been using.
Frank Zappa also used them in his classical recording. The engineers
felt that they could be improved
by deepening them, so some were made 3.5" deep. These were startingly
better, with a tightening of
the pickup pattern and better isolation from nearby instruments. They
were used for solo instruments
in concertos, as well as instrumental sections for sound reinforcement
of the orchestra.
Some of these were also produced with a diameter of 28". The reach is
exceptional, but no practical
use has surfaced for these as yet. In foothall games they clearly pick
up the quarterback calls, but
also reach across the field.
The whole 22 year long mic memo newsletter is over 500 pages, there's a
few more mentions in there somewhere. As well as a bunch of other shapes
they tried. So you can tell why I'm interested in this sort of design.
I'm wanting to find dishes to make the 28" or such size. May end up
designing a plastic molding setup.
Walt
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