2
OPERATION
Power
The BETA 87A requires phantom power. This may be sup-
plied to the microphone from an external power supply (such as
the Shure model PS1A) or directly from preamplifiers, mixers,
or consoles with built-in phantom power. Suitable sources
should provide 11 to 52 Vdc phantom voltage.
Proximity Effect
Unidirectional microphones such as the BETA 87A progres-
sively boost bass frequencies by 10 to 15 dB at 100 Hz when
the microphone is at a distance of about 6 mm (1/4 in.) from the
sound source. This phenomenon, known as proximity effect,
can be used to create a warmer, more powerful sound. To pre-
vent explosive low frequency sound during close-up use, the
BETA 87A bass response gradually rolls off. This provides
greater control and helps the user take advantage of proximity
effect.
Wind Noise
The BETA 87A has an integral wind and pop filter which
provides excellent protection against most wind and breath
noise. Under adverse conditions, such as high winds or close
proximity to a “problem” vocalist, the optional foam windscreen
can be used.
Impedance
A minimum load impedance of 800 ohms should be used
for maximum signal handling and minimum distortion. The load
may be as low as 150 ohms, but a reduction in output signal
strength and output clipping level will result.
SPECIFICATIONS
Cartridge Type
Condenser (electret bias)
Frequency Response
50 to 20,000 Hz (see Figure 2)
Polar Pattern
Supercardioid (see Figure 3)
Output Impedance
Rated at 150 ohms (100 ohms actual
±
20%)
Recommended minimum load impedance: 800 ohms
Sensitivity (at 1,000 Hz)
Open Circuit Voltage
–54 dBV/Pa (2 mV)
. . . . . . . . . . . . . . . . . .
(1 Pa = 94 dB SPL)
Clipping Level (at 1,000 Hz)
1000 ohm Load
–6 dBV (0.5 V)
. . . . . . . . . . . . . . . . . . . . . . . . . .
Maximum SPL (at 1,000 Hz)
142 dB (0.25% THD, 1000 ohm load)
Self-Noise (equivalent sound pressure level; measured with true
r ms voltmeter)
25 dB typical, A-weighted
27 dB typical, weighted per DIN 45 405
Dynamic Range
117 dB (maximum SPL to A-weighted noise level)
Signal-to-Noise Ratio
69 dB at 94 dB SPL (IEC 651)*
Polarity
Positive pressure on diaphragm produces positive voltage on pin
2 relative to pin 3
Power
Phantom Supply Requirement
11 to 52 Vdc, positive
. . . . . . . .
at both pins 2 and 3
Current Drain
1.0 to 1.2 mA
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Connector
Three–pin (XLR) professional audio
Case
Aluminum construction with blue metallic finish, and hardened
steel grille with nickel satin chrome plating
Dimensions
See Figure 4
Net Weight
200 grams (7 oz)
*S/N ratio is difference between 94 dB SPL and equivalent SPL of self–
noise A-weighted.
CERTIFICATION
Conforms to European Union directives, eligible to bear CE
marking; meets European Union EMC Immunity Requirements
(EN 50 082–1, 1992).
FURNISHED ACCESSORIES
Swivel Adapter
A25C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Carrying/Storage Bag
26A13
. . . . . . . . . . . . . . . . . . . . . . . . .
OPTIONAL ACCESSORIES
Phantom Power Supply
PS1A
. . . . . . . . . . . . . . . . . . . . . . . .
Isolation Mount
A53M, A53HM
. . . . . . . . . . . . . . . . . . . . . . . .
Windscreen
A85WS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cable (7.6 m—25 ft)
C25F
. . . . . . . . . . . . . . . . . . . . . . . . . . .
REPLACEMENT PARTS
Grille
RK312
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cartridge
R193
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Replacement Amplifier Assembly
RK356
. . . . . . . . . . . . . . .
