Directional Characteristics Of Loudspeakers - BRUEL & KJAER 1013 Instructions And Applications

independent of room response the measurement has to be carried out in an
anechoic chamber. The complete measuring set-up in Fig. 5.8 covers a
straight frequency range of 200--40ooo Hz. By substituting the Beat Fre-
quency Oscillator Type 1013 and the Microphone Type 4133 by other B
&
K
types the frequency range can be altered to cover 20 to 20ooo Hz. The
range of sound pressure level is approximately 2o-160
dB
with reference
2 X 10-
4
~tbar.
Fig. 5.9 shows a recording of the free field characteristic obtained in the axis
of the loudspeaker.
Directional Characteristics of Loudspeakers.
When the Level Recorder is combined with the Turntable Type 3921 a
complete equipment for the automatic measurement of directional char-
acteristics is obtained. For description of the Turntable and its operation,
the reader is referred to the instruction book of the Level Recorder Type
2305.
With the measuring arrangement illustrated in Fig. 5.10 the directional
characteristic of a tweeter was recorded at various frequencies. In Fig. 5.11
the results are reproduced.
The measuring equipment consists, apart from the Turntable and the Level
Recorder, of the B & K Beat Frequency Oscillator (BFO) Type 1013, the
1618-¥~
Fig. 5.10. Measuring arrangement for recording directional characteristics of
loudspeakers.
34