Handbook for Sound Engineers

Microphones 545

modulation signal). Although two individual micro-

phones may be used, single-unit M/S microphones are

more convenient and generally have closer cartridge

placement. Fig. 16-116, a Shure VP88, and Fig. 16-117,

an AKG C-422, are examples of M/S microphones.

Fig. 16-118 indicates the pickup patterns for a

typical M/S microphone configuration. The mid

cartridge is oriented with its front (the point of greatest

sensitivity) aimed at the center of the incoming sound

stage. A cardioid (unidirectional) pattern as shown is

often chosen for the mid cartridge, although other

patterns may also be used. For symmetrical stereo

pickup, the side cartridge must have a side-to-side

facing bidirectional pattern (by convention, the lobe

with the same polarity as the front mid signal aims 90°

to the left, and the opposite polarity lobe to the right).

In a stereo FM or television receiver, the mono sum

baseband signal and the stereo difference subcarrier

signal are demodulated and then decoded, using a

sum-and-difference matrix, into left and right stereo

audio signals. Similarly, the mid (mono) signal and the

Figure 16-115. ORTF microphone technique.

Figure 16-116. Shure VP88 stereo condenser microphone.
Courtesy Shure Incorporated.

110°

0°

Left Right

7 in

(17 cm)

Figure 16-117. AKG C422 stereo coincident microphone.

Courtesy AKG Acoustics, Inc.

Figure 16-118. MS Microphone Pickup Patterns.