A/B Stereo - Schoeps MAB 1000 Bedienungsanleitung

A/B Stereo

Area to be recorded
(e.g. orchestra or band)
a
Distance d between the microphones and
recording angle α; the sound sources should
be lying within the recording angle
The distance a is particularly important: it
influences not only the reproduction, but also
the sound, since it defines the ratio of direct
to reflected sound (diffuse sound). At a small
distance, the recording will sound "dry" while,
at a large distance, more "room" will be
recorded. The latter could be desirable if the
room has nice acoustics. What this all implies
is that it is best to choose the distance primarily
for aesthetic purposes, where the acoustic
properties of the room are as important as
anything else. In the process, the distance d
between the microphones will be set which
derives from the relationship of microphone
distance a to stage width b. It can be obtained
from the table which follows.
Even in A/B recordings with pressure trans-
ducers the microphones can be turned slightly
outward, since pressure transducers at higher
frequencies do not have an ideal omnidirec-
tional pattern. This characteristic can be
exploited to obtain level differences between
the channels.
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b
stereo
main axis
α
d
b/a
0.54
0.73
0.93
1.15
1.40
1.68
2.0
2.38
3.46
5.50
11.3
oo
stage width
b/a =
microphone distance from stage
Table 1
This table is used to determine the recording
angle from the ratio b/a. a and b can be meas-
ured in meters, steps etc.
recording
angle α:
60°
80°
100°
120°
140°
Table 2
This table is for "spaced omni" recordings, and
gives the distance d between the microphones
as a function of the recording angle α .
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angle α
30°
40°
50°
60°
70°
80°
90°
100°
120°
140°
160°
180°
distance d
between the
microphones:
76 cm
60 cm
50 cm
44 cm
40 cm