Handbook for Sound Engineers

542 Chapter 16

By using the DSP-4P processor, Fig. 16-108, the
following settings can be made independently of one
another in three adjustable frequency ranges. With the
three knobs in the upper row, the directional patterns in
each of the three frequency bands can be set. The
settings are indicated by a circle of LEDs around each
of the knobs. At the lower left of each knob is the omni-
directional setting; at the lower right is the figure 8
setting. Eleven intermediate pattern settings are avail-
able. The knobs in the lower row are set between those
in the upper row. They are used for setting the bound-
aries between the frequency ranges; 100 Hz–1 kHz and
1–10 kHz, respectively, in octave steps.

The three buttons at the lower right are for storing
and recalling presets. If the unprocessed microphone
signals have been recorded, these adjustments can be
made during postprocessing.
The processor operates at 24-bit resolution with
either a 44.1 kHz or 48 kHz sampling rate. When a
digital device is connected to the input, the PolarFlex™
processor adapts to its clock signal.

16.7 Stereo Microphones

Stereo microphones are microphones or systems used
for coincident, XY, M/S, SASS, binaural in-the-head,
and binaural in-the-ear (ITE) recording. These systems
have the microphones close together (in proximity of a
point source or ear-to-ear distance) and produce the
stereophonic effect by intensity stereo, time-based
stereo, or a combination of both.

16.7.1 Coincident Microphones

A highly versatile stereo pickup is the coincident micro-
phone technique.11,12,13 Coincident means that sound
reaches both microphones at the same time, implying
that they are at the same point in space. In practice, the

two microphones cannot occupy the same point, but

they are placed as closely together as possible. There

are special-purpose stereo microphones available that

combine the two microphones in one case. Since they

are essentially at the same point, there can be no time

differences between arrival of any sound from any

direction; thus no cancellation can occur. It might first

appear that there could be no stereophonic result from

this configuration. The two microphones are usually

unidirectional and oriented at 90° to one another. The

combination is then aimed at the sound source, each

microphone 45° to a line through the source. Stereo

results from intensity differences—the left microphone

(which is to the right of the pair) will receive sounds

from the left-hand part of the stage with greater volume

than it will receive from the right-hand side of the stage.

The stereo result, although often not as spectacular

as that obtained from spaced microphones, is fully

mono compatible, and it most accurately reproduces the

sound of the acoustic environment. It is quite foolproof

and quick to set up.

Variations of the coincident technique include

changing the angle between the microphone (some

stereo microphones are adjustable); using bidirectional

microphones, which results in more reverberant sound;

using combinations of unidirectional and bidirectional

microphones; and using matrix systems, which electri-

cally provide sum and difference signals from the left

and right channels (these can be manipulated later for

the desired effect).

The basic coincident technique was developed in the

1930s (along with the first stereo recordings) by English

engineer Alan Blumlein.^14 Blumlein used two figure 8

pattern ribbon microphones mounted so that their

pattern lobes were at right angles (90°) to each other, as

shown in Fig. 16-104. The stereo effect is produced

Figure 16-108. Schoeps DSP-4P microphone processor.
Courtesy Schoeps GmbH.

(^1) » 3
Figure 16-109. Coincident microphone technique using
two bidirectional microphones.
A B
B A
Source