Bedrock AM100, Руководство по эксплуатации

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108 Bedrock AM100 operating manual © Bedrock Audio BV, 2021
A2. BAMT1-MP309 microphone
The BAMT1-MP309 is an alternative class 2 microphone-preamp combination offered for
use with the Bedrock AM100. The MP309 is a high-end Class II / Type II free field micro-
phone capsule.
A2.1. Typical free field response and actuator to free field corrections for the
BAMT1-MP309.
The typical free field response of the MP201 capsule is specified in this section. The MP201
(including grid) was measured by the manufacturer at 0 degrees incidence, based on aver-
age values of microphone capsules against a B&K 4180 response using a B&K 4228 Piston-
phone. Microphones were mounted on M201 preamp. The typical actuator reponse was
determined using a GRAS RA0015 and a GRAS 14AA. The measurement uncertainty is
+/- 0.2 dB.
We specify three series of measurements results in this paragraph, marked as columns (1),
(2) en (3) in the table below. A description of the data in these columns, and their uses for
measurement and calibration, is given below.
• Column (1) is the typical free-field response of the microphone. To en-
hance the accuracy of free-field measurements, users may subtract the typi-
cal free field response values in dB from the measured sound pressure levels
per frequency band.
• The typical free field response of column (1) is also used for periodic elec-
tric testing according to 61672-3. In that case, the typical free field response
(1) is added to the measurement values to obtain an equivalent acoustic
sound pressure level when the capsule is removed and an electrical test sig-
nal is applied at the microphone preamplifier input using a 16 pF coupler.
• The typical actuator response of column (2) is not usually applied directly,
but was measured to be able to calculate the actuator to free-field corrac-
tions of column (3)
• For periodic acoustic or actuator testing according to 61672-3, the actuator-
to-free-field correction of column (3) is added to the measurement values
to obtain an equivalent acoustic sound pressure level when the capsule is
measured using an electrostatic actuator. The actuator-to-free-field is in
literature also often referred to as the free field correction.