Schoeps MAB 1000 Bedienungsanleitung PDF herunterladen (Seite 13)

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1. OCT Front System with MAB 1000

(OCT=Optimized Cardioid Triangle by Dr.

Theile, Institut für Rundfunktechnik IRT)

Aim: the pickup of the three front chan nels

(L, C, R) of a surround recording

The preferred setup for OCT uses a forward-

facing cardioid for the center channel. For the

front L and R channels two supercardioid micro-

phones are placed at opposite ends of an

imaginary line running about 8 cm behind the

center microphone. These two microphones

should be 40 – 90 cm apart, depending on

the required recording angle*, and must face

squarely outward, away from center (see dia-

grams below and on the following pages).

Good separation between the center-to-left

sector and the center-to-right sector is obtained

with this method. For example, sound origi-

nating from half right is picked up only very

weakly by the left microphone. Sound from

the extreme right will be picked up directly

on-axis by the right-facing supercardioid (0 dB)

and by the forward-facing cardioid (attenuated

by 6 dB due to its direc tional pattern). Finally

it will be picked up, with a delay caused by the

increased distance, on the rear lobe of the left-

facing supercardioid. The polar pattern attenu-

ation for this will be 10 dB and the polarity will

be inverted. These factors prevent the forma-

tion of annoying “phantom images“ of sound

sources in the wrong sector during playback.

A clean center channel is conveyed by this

system, since front-incident sound is picked up

mainly by the cardioid in the center. Because

of their high directivity, the left and right micro-

phones pick up front-incident sound only at a

much lower level.

If the cardioid is placed 8 cm forward, the

following recording angles* will result, depend-

ing on the distance between the supercardioids:

40 cm: 160°, 50 cm: 140°,

60 cm: 120°, 70 cm: 110°,

80 cm: 100°, 90 cm: 90°,

It is better to err in the direction of greater

spacing, so that one can be sure to avoid cen-

ter-heavy images.

The fact that the supercardioids receive so

much of their sound from off axis necessitates

the use of small-diaphragm condenser micro-

phones, as only this type of microphone has

the requisite independence of frequency

response from the angle of sound incidence.

The CCM 41V and the MK 41V are particularly

well suited for this application but the CCM 41

or MK 41 can also be used.

Surround with OCT Front System

CCM 41VL or

CCM 41L

8 cm

40 – 90 cm, dependent on

the intended recording angle*

CCM 41VL or

CCM 41 L

CCM 4L

(an omni, e.g. CCM 2SL,

can be substituted)

1.1 OCT Front System

basic version

FRONT

* the range within which the sound sources should

be placed, as “seen“ by the microphone

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