Theatre Design & Technology - Winter 1981 - 20

Figure 5

Stereo

M-S

'-'~
__","""",.L.41'./.L/'J

*i~
."

*

I

.-~j,;~

...........

'-'"~~

_~

PZM Microphone
facing straight towards the center of the ensemble (the Middle
mic) and a bidirectional or figure-eight microphone oriented left
and right (the Side mic)(see Fig. 5). Because of the orientation
of the two elements, the cardioid element picks up the center
area, algebraically represented by L + R, any sound common to
both left and right. The figure eight element reproduces the
difference signal, L - R, or anything not in the center of the
stereo image. The two microphone signals, when added together, first in polarity and then out of polarity, yield an accurate left
and right stereo image that is pleasant to listen to in stereo and
gives excellent mono compatibility. Of course, to achieve the
best monophonic blending the two microphones should be as
close to each other as possible. There are stereo microphones
that combine two separate elements in the same case, each one
with an adjustable pickup pattern, separated by fractions of an
inch, that assure accurate mono blending of the signals. The
adjustable patterns allow the same stereo microphone to be
used for X - Y, M - S, or other stereo pickup techniques not
mentioned here.

The Pressure Zone Microphone
No contemporary article on microphones would be complete
without mentioning the pressure zone microphone or PZM™
The pressure zone microphone is an omnidirectional microphone specifically designed to take advantage of the f100rwave
and direct sound wave coincidently. Its diaphragm is small,

about '14" in diameter, making its impulse or transient response
very good. The PZM is not a contact microphone as some
people say, but rather, a pressure transducer that takes advantage of the pressure zone that develops as a vibrating air
molecule bounces off a reflecting surface. The microphone
works best on a large boundary surface such as a wall or floor
but I have also used them attached to plexiglas sheets about 3'
x 4' flown over an ensemble with some success.
The PZM is well suited for dramatic work. I have used them for
sound reinforcement, built them into sets (or coffins in the case
of a recent production of Dracula), and even used them as
lavaliere microphones on performers. Although the PZM is an
omnidirectional microphone, its directional characteristics can
be controlled by using some sound absoprtion material next to
the "dead" side of the microphone.
While it may be argued that the frequency response of many
microphones is flatter than that of the PZM by 2 or 3 dB, and the
PZM really is not that efficient a transducer, a PZM makes you
think more about microphone placement with an eye (or ear)
toward phasing problems than a standard microphone does.
A $500 studio microphone placed within a few inches of a
reflecting surface can create notches and dips in the frequency
response that might be 20-30 dB deep. A PZM, however, will not
exhibit these comb filtering effects when properly positioned,
making the 2 or 3 dB variation in its response the limiting factor
in recording instead of the 20 or 30 dB dips caused by incorrect
placement of the studio microphone.
A final word about PZM's. Although a floor mounting is an
excellent location there are situations where it just will not work.
Trying to record an orchestra, for example, with the microphones-PZM or otherwise-at the edge of the stage a few feet
from the orchestra, will probably result in poor balance between
sections. The violins will be almost on top of the microphones
while the brass and woodwinds might be three or four times
farther away. Recall what varying the distance between microphone and performer does to the reverberation quality of the
recording. The violins will wind up sounding too dry while the
brass/woodwinds will probably be too reverberant. The solution
is to fly the microphones so that the ratio of differences in
subject-to-microphone distances will be less. The PZM in a floor
mount configuration is hard to beat for small ensembles, piano
(try taping one to the inside of the cover for a tight sound), or
vocalists, but for the larger groups, conventional placements still
have an edge.
This article is by no means exhaustive, and the serious
practitioner is encouraged to peruse some of the excellent
books and articles written on the subject, some of which are
included in the bibliography. Everyone should experiment with
their microphones. They are tools, not magic, and will give you
good performance even if they are not "megabuck" studio
models, if they are placed with some thought to their acoustic
environment and their relationship to the placement of other
microphones in the setup.D

References/Suggested Reading
Barclay, Clay. "PZM, Theory and Practice of a New Microphone
Design." DB-The Sound Engineering Magazine, June 1981.
Bartlett, Bruce. "Stereo Microphone Techniques." DB- The Sound Engineering Magazine, December 1979.
Burroughs, Lou. Microphones: Design and Application. New York:
Sagamore Publishing Co. Inc., 1974.
Collison, David. Stage Sound. New York: Drama Book Specialists
(Publishers). 1976.
Davis, Don and Carolyn. Sound System Engineering. Indianapolis:
Howard W. Sams and Co. Inc., 1975.
Eargle, John. Sound Recording. New York: Van Nostrand Reinhold Co.,
1976.
Olson, Harry F. Modern Sound Reproduction. New York: Van Nostrand
Reinhold Co., 1972.

Tom Hayes holds degrees in physics, technical theater, and broadcasting. He is currently Audio Director at Krannert Center for the Performing Arts.
18

Theatre Design & Technology

USITIlWinter, 1981



Table of Contents for the Digital Edition of Theatre Design & Technology - Winter 1981

Contents
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Theatre Design & Technology - Winter 1981 - Contents
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