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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,
creates a warmer, more powerful sound. To prevent 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 providing
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
Use a minimum load impedance of 800 ohms 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 results.
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 –52.5 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)
140.5 dB (0.25% THD, 1000 ohm load)
Self-Noise (equivalent sound pressure level; measured with true
rms voltmeter)
23.5 dB typical, A-weighted
25.5 dB typical, weighted per DIN 45 405
Dynamic Range
117 dB (maximum SPL to A-weighted noise level)
Signal-to-Noise Ratio
70.5 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
207 grams (7.6 oz)
*S/N ratio is difference between 94 dB SPL and equivalent SPL of self–
noise A-weighted.
CERTIFICATION
Eligible to bear CE Marking. Conforms to European EMC Directive
89/336/EEC. Meets applicable tests and performance criteria in
European Standard EN55103 (1996) parts 1 and 2, for residential
(E1) and light industrial (E2) environments.
FURNISHED ACCESSORIES
Swivel Adapter A25D. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Carrying/Storage Bag 26A13. . . . . . . . . . . . . . . . . . . . . . . . .
OPTIONAL ACCESSORIES
Phantom Power Supply PS1A. . . . . . . . . . . . . . . . . . . . . . . .
Isolation Mount A55M, A55HM. . . . . . . . . . . . . . . . . . . . . . . .
Windscreen A85WS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cable (7.6 m—25 ft) C25F. . . . . . . . . . . . . . . . . . . . . . . . . . .
REPLACEMENT PARTS
Grille RK312. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cartridge R193. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Replacement Amplifier Assembly 90KF2600. . . . . . . . . . . .