HOLOPHONE H2-PRO, User Manual

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H2-PRO Surround Sound Microphone User Guide
Rising Sun Productions Ltd. page 16
Appendix A: Directivity measurements
Directivity measurement of the ellipsoid-mounted microphones
The assessment of the directivity pattern was performed in the
INMS GLK anechoic chamber. The ellipsoid holder was mounted
on a rod (16mm diameter) attached to the center of a computer-
controlled turntable (Brüel and Kjaer model 9640 with the 5997
turntable controller). The loudspeaker (Paradigm export monitor)
was placed at a distance of 1.3 m from the front microphone of the
ellipsoid. The directivity patterns of the Front, Right, Left, Right
Surround and the Left Surround microphones were measured at 10
degrees intervals, with the zero degree position indicating the Front
microphone facing the loudspeaker.
The outputs from the prototype Holophone PCM-7 preamplifier
control module of the non-wireless Global Sound Microphone
System were recorded by an eight-channel recorder (TASCAM
DA-38). The pure-tone oscillator (Kroh-hite model 4180) provided
the signal to drive the loudspeaker via a power amplifier at the
following frequencies: 400, 1 000, 4 000, 16 000, and 20 000 Hz.
The sound pressure level at the Front microphone at zero degree
was maintained constant at 94 dB, with the Top channel level
control set to zero to avoid the influence of the microphones by the
top channel.
At each of the above frequencies, the directivity patterns of the
above microphones are shown in the following graphs. The radical
scales of the figures are marked at 5 dB intervals in 1 dB steps.