Earthworks M30BX User Manual - page 2
Description
Earthworks M30BX is an omnidirectional
(pressure) microphone designed and cali-
brated for measurement purposes. It is a pre-
polarized condenser microphone directly
coupled to a wideband, low output imped-
ance preamplifier. The M30BX requires a sin-
gle type P28L (Lithium) or 4LR44 or equiva-
lent 6V battery as a power source. It features
a linear free-field frequency response from
9 Hz to 30kHz (please see the enclosed indi-
vidual calibration chart).It has very low han-
dling noise, a uniform polar pattern, and has
6dB of extra gain available. Its unique circuit-
ry excludes the transconductance of the in-
put FET from the overall gain structure. This
means the sensitivity remains very stable
when the microphone is subjected to varia-
tions in ambient temperature. The M30BX
meets or exceeds ANSI Type 1 requirements.
Each microphone is delivered with its own
calibration chart providing its individually mea-
sured open-circuit sensitivity for both gain posi-
tions, and the frequency response curve. A com-
puter file containing the frequency response
data for importing directly into measurement
software is available from Earthworks, Inc. upon
request at an extra cost. A mounting clip, a cali-
brator adapter, an XLR to RCA adapter, and a
battery are included with the microphone.
Applications
Earthworks M30BX is ideally suited for on-
location acoustical measurements including
loudspeaker design and quality control, sound
system setup and troubleshooting, room acous-
tics, or any application where an accurate free-
field measurement microphone is required and
portability is important or a power source is not
readily available. Many test systems manufactur-
ers, such as DRA Labs (MLSSA™), Smaart™
and DEQX™, are recommending M30BX
microphones. The wide linear minimum-phase
response and fast well-damped impulse response
(Fig. 2) make M30BX an excellent microphone
for loudspeaker design, especially for time do-
main measurements.
The M30BX is simple to operate. Make sure
the battery (included) is properly installed in
the microphone. To open the battery com-
partment hold the microphone by the upper
body and unscrew the lower, larger part of
the microphone (this cover is not remov-
able). The battery is only switched on when
an XLR connector is plugged into the mi-
crophone. The M30BX will not operate from
phantom power.
The M30BX will drive either balanced or
unbalanced inputs. An XLR to RCA adapter is
enclosed for driving unbalanced inputs of sound
cards directly. Please note that the best S/N ratio
is achieved using a balanced interface.
Inside the battery compartment there is a gain
switch. At the “0dB” setting the M30BX has nor-
mal condenser sensitivity. At the “6dB” setting
the extra dB of gain is applied, eliminating a need
for an external preamplifier for most applications.
Calibration
The microphone is calibrated at the factory
at 1 kHz (therefore independent of any fre-
quency weighting). The sensitivity in mV/Pa
is provided on the calibration chart for both
gain positions. Make sure to use the actual
data rather than relying upo n the nominal
14dB gain figure. If on-site calibration is re-
quired, use the enclosed one half inch stan-
dard calibration adapter.
Specifications
Frequency response: 9Hz to 30kHz +1/-3dB
Polar Pattern: Omnidirectional
Sensitivity: 30mV/Pa (Typical)
with 6dB Gain 60mV/Pa (Typical)
Power Requirements: 6V Battery Type P28
(2CR-1/N, 4LR44 or eq.)
Peak Acoustic Input: 130dB SPL
with 14dB Gain 124dB SPL
Output:
XLR (Fig. 1)
Minimum Load: 600
Ω btw. pins 2 & 3
Noise:
22dB, A equivalent
Dimensions L x D: 220 x 23 mm
(8.65 x .910 in.)
Weight:
180g (.4lb)
Compliant
Fig 1. XLR Output Connector Assignment of M30BX
Fig 2. Impulse Response (Typical) of M30BX
Fig 3. Polar Response (Typical) of M30BX
Version 5 July 12, 2012
Specifications are subject to change without notice.