SENNHEISER ELECTRONIC GMBH & CO. KG
COMPONENT MAINTENANCE MANUAL
HMEC 26 SERIES
Page 1003
Feb 10/10
23-41-48
C. Adjusting the microphones sensitivity/Re-adjusting to factory pre-set
The microphone sensitivity is factory pre-set by Sennheiser to 80 mV/Pa (40 mV
±6 dB according to
RTCA DO-214, subparagraph 2.2.1.1). This value is optimized for most cases of operation and needs no
adjustment.
(1) If needed, you can adjust the microphone sensitivity to your individual needs (see also headsets
instruction manual). Turn a small screwdriver in the direction of the arrow.
The re-adjustment to the original factory pre-set of 80 mV/Pa (40 mV
±6 dB according to
RTCA DO-214, subparagraph 2.2.1.1) is desribed in RTCA DO-214, subparagraph 2.6.2.1b.
A simple set-up for an approximated re-adjustment is shown in Figure 1001.
Figure 1001
Microphone sensitivity adjustment
Oscilloscope
(for the frequency
range measurement
of the microphone)
Multimeter
Power supply
8 to 16V DC
Microphone Hi
Microphone Lo
Nearfield
sensitivity
25 µF
220 ohms
470 ohms
SPL = 94 dB at the front
side of the microphone
6 mm
Transducer with
a diameter of
approx. 30 mm
Measurement set-up goes
as an example/schematic
Sine wave generator
(1 kHz AF output signal)
Oct 30/08
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