Handbook for Sound Engineers

524 Chapter 16

16.6.1.1 Phase Coherent Cardioid (PCC)

The phase coherent cardioid microphone (PCC) is a
surface-mounted supercardioid microphone with many
of the same benefits as the PZM. Unlike the PZM,
however, the PCC uses a subminiature supercardioid
microphone capsule.

Technically, the PCC is not a pressure zone micro-
phone. The diaphragm of a PZM is parallel to the
boundary; the diaphragm of the PCC is perpendicular to
the boundary. Unlike a PZM, the PCC aims along the
plane on which it is mounted. In other words, the main
pickup axis is parallel with the plane.

The Crown PCC-160 microphone, a Phase Coherent
Cardioid surface-mounted boundary microphone, Fig.
16-68, is intended for use on stage floors, lecterns, and
conference tables wherever gain-before-feedback and
articulation are important. Fig. 16-69 shows the hori-
zontal polar response for this microphone.

The PCC-160 can be directly phantom powered. A
bass-tilt switch is provided for tailoring low end
response.

16.6.1.2 Directivity

The PZM picks up sounds arriving from any direction

above the surface it is mounted on (hemispherical). It is

often necessary to discriminate against sounds arriving

from certain directions. To make the microphone direc-

tional or hemicardioid (reject sounds from the rear) the

capsule can be mounted with the cantilever in a corner

boundary made of ¼ inch (6 mm) thick Plexiglas. The

larger the boundary, the better it discriminates against

low-frequency sounds from the rear.

For best results, a corner boundary 12 in × 24 in

wide (0.3 m × 0.6 m) is recommended and is nearly

invisible to the audience, Fig. 16-70.

A boom-mounted or suspended PZM can be taped to

the center of a ¼ inch (6 mm) thick 2 ft × 2 ft

(0.6 m × 0.6 m) or 4 ft × 4 ft (1.2 m × 1.2 m) panel. The

microphone should be placed 4 inches (10 cm)

off-center for a smoother frequency response. Using

clear acrylic plastic (Plexiglas) makes the panel nearly

invisible from a distance. If the edges of the Plexiglas

pick up light, they can be taped or painted black.

16.6.1.2.1 Sensitivity Effects

If a PZM capsule is placed very near a single large

boundary (within 0.020 inch or 0.50 mm), such as a

large plate, floor, or wall, incoming sound reflects off

the surface. The reflected sound wave adds to the

incoming sound wave in the Pressure Zone next to the

boundary. This coherent addition of sound waves

doubles the sound pressure at the microphone, effec-

tively increasing the microphone sensitivity or output

by 6 dB over a standard microphone.

If the PZM capsule is placed at the junction of two

boundaries at right angles to each other, such as the

Figure 16-68. Crown PCC®-200 Phase Coherent Cardioid
microphone. Courtesy Crown International, Inc.

Figure 16-69. The horizontal plane polar response of the
PCC-160 phase coherent cardioid microphone with the
source 30° above the infinite boundary. Courtesy Crown
International, Inc.

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Figure 16-70. Corner boundary used to control directivity

of pressure zone microphones.