Handbook for Sound Engineers

550 Chapter 16

always remain dominant. This microphone is the one
through which the actors pictured on the screen will be
heard.

16.7.6 SASS Microphones

The Crown® SASS-P MK II or Stereo Ambient
Sampling System™, Fig. 16-127, is a patented,
mono-compatible, near-coincident array stereo
condenser microphone using PZM technology.

The SASS uses two PZMs mounted on boundaries
(with a foam barrier between them) to make each micro-
phone directional. Another Crown model, SASS-B, is a
similarly shaped stereo boundary mount for Brüel &
Kjaer 4006 microphones and is used for applications
requiring extremely low noise.
Controlled polar patterns and human-head-sized
spacing between capsules create a focused, natural
stereo image with no hole-in-the-middle for loud-
speaker reproduction, summing comfortably to mono if
required.
The broad acceptance angle (125°) of each capsule
picks up ambient sidewall and ceiling reflections from
the room, providing natural reproduction of acoustics in
good halls and ambient environments. This pattern is
consistent for almost ±90° vertical.
A foam barrier/baffle between the capsules shapes
the pickup angle of each capsule toward the front,
limiting overlap of the two sides at higher frequencies.
Although the microphone capsules are spaced a few
centimeters apart, there is little phase cancellation when
both channels are combined to mono because of the
shadowing effect of the baffle. While there are phase
differences between channels, the extreme amplitude
differences between the channels caused by the baffle,
reduce phase cancellations in mono up to 20 kHz.

The SASS has relatively small boundaries. However,

it has a flat response down to low frequencies because

there is no 6 dB shelf as in standard PZM microphones

(see Section 16.6.1.2.3). The flat response is attained

because the capsules are omnidirectional below 500 Hz,

and their outputs at low frequencies are equal in level,

which, when summed in stereo listening, causes a 3 dB

rise in perceived level. This effectively counteracts one

half of the low frequency shelf normally experienced

with small boundaries.

In addition, when the microphone is used in a rever-

berant sound field, the effective low-frequency level is

boosted another 3 dB because the pattern is omnidirec-

tional at low frequencies and unidirectional at high

frequencies. All of the low-frequency shelf is compen-

sated, so the effective frequency response is uniform

from 20 Hz–20 kHz. Fig. 16-128 is the polar response

of the left channel (the right channel is the reverse of the

left channel).

16.7.7 Surround Sound Microphone System

16.7.7.1 Schoeps 5.1 Surround System

The Schoeps 5.1 surround system consists of the KFM

360 sphere microphone, two figure 8 microphones with

Figure 16-127. Crown® SASS-P MK II stereo microphone.
Courtesy of Crown International, Inc.

Figure 16-128. SASS-P MK II polar response, of the left

channel. 0° sound incidence is perpendicular to the

boundary. The right channel is a mirror image of the left

channel. Courtesy Crown International.