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Output Impedance
Output Impedance
Rated at 150 Ω; 200 Ω actual
Rated at 150 Ω; 200 Ω actual
Recommended Minimum Load Impedance
Recommended Minimum Load Impedance
800 Ω
800 Ω
Sensitivity (at 1,000 Hz)
Sensitivity (at 1,000 Hz)
Open Circuit Voltage: –49 dBV/Pa (3.5 mV) (phantom)
Open Circuit Voltage: –49 dBV/Pa (3.5 mV) (phantom)
–50 dBV/Pa (3.2 mV) (battery) (1 Pa = 94dB SPL)
–50 dBV/Pa (3.2 mV) (battery) (1 Pa = 94dB SPL)
Output Clipping Level (1 kHz, 3% THD)
Output Clipping Level (1 kHz, 3% THD)
800-Ω Load–14 dBV (0.63 V) (phantom), 1% THD;
800-Ω Load–14 dBV (0.63 V) (phantom), 1% THD;
–23 dBV (0.71 V) (battery), 3% THD
–23 dBV (0.71 V) (battery), 3% THD
Total Harmonic Distortion
Total Harmonic Distortion
< 0.25% (130 dB SPL at 250 Hz into 800 Ω load)
< 0.25% (130 dB SPL at 250 Hz into 800 Ω load)
Maximum SPL
Maximum SPL
800 Ω Load: 141 dB (phantom), 123 dB (battery)
800 Ω Load: 141 dB (phantom), 123 dB (battery)
Hum Pickup
Hum Pickup
–3 dB equivalent SPL in a 1 millioersted field (60 Hz)
–3 dB equivalent SPL in a 1 millioersted field (60 Hz)
Output Noise (equivalent sound pressure levels;
Output Noise (equivalent sound pressure levels;
measured with true rms voltmeter)
measured with true rms voltmeter)
22 dB typical, A-weighted
22 dB typical, A-weighted
25 dB typical, weighted per DIN 45 505
25 dB typical, weighted per DIN 45 505
Dynamic Range
Dynamic Range
119 dB (phantom); 101 dB (battery) (maximum SPL,
119 dB (phantom); 101 dB (battery) (maximum SPL,
2000–Ω load, to A–weighted noise level)
2000–Ω load, to A–weighted noise level)
Signal-to-Noise Ratio
Signal-to-Noise Ratio
72 dB (IEC 651)* at 94 dB SPL
72 dB (IEC 651)* at 94 dB SPL
Overvoltage Protection
Overvoltage Protection
Maximum External Voltage Applied to Pins 2 and 3
Maximum External Voltage Applied to Pins 2 and 3
with respect to Pin 1: +52Vdc
with respect to Pin 1: +52Vdc
Reverse polarity protected to 75 Vdc
Reverse polarity protected to 75 Vdc
Polarity
Polarity
Positive pressure on diaphragm produces positive
Positive pressure on diaphragm produces positive
voltage on pin 2 relative to pin 3
voltage on pin 2 relative to pin 3
Cartridge Capacitance
Cartridge Capacitance
24 pF
24 pF
Power
Power
Phantom Operation
Phantom Operation
Supply Voltage: 11 to 52 Vdc, (+) pins 2 and 3
Supply Voltage: 11 to 52 Vdc, (+) pins 2 and 3
Current Drain: 1.0 to 1.2 mA max. at 52 Vdc
Current Drain: 1.0 to 1.2 mA max. at 52 Vdc
Battery Operation
Battery Operation
Type: 1.5 V alkaline, AA size (NEDA 15A)
Type: 1.5 V alkaline, AA size (NEDA 15A)
Life: Up to 5,000 hours with fresh battery
Life: Up to 5,000 hours with fresh battery
Environmental Conditions
Environmental Conditions
Temperature:
Temperature:
Storage: . . . . . . . –29° to 74° C (–20° to 165° F)
Storage: . . . . . . . –29° to 74° C (–20° to 165° F)
Operating:
Operating:
–6.7° to 49° C (20° to 120° F)
–6.7° to 49° C (20° to 120° F)
Humidity:
Humidity:
Storage . . . . 0–95% relative humidity at room
Storage . . . . 0–95% relative humidity at room
temperature (72° to 80° F, 22° to 27° C)
temperature (72° to 80° F, 22° to 27° C)
Connector
Connector
XLR professional audio 3-Pin
XLR professional audio 3-Pin
Case
Case
Steel and brass construction with gray finish and
Steel and brass construction with gray finish and
stainless steel mesh grille
stainless steel mesh grille
Dimensions
Dimensions
See Figure 3
See Figure 3
OVERALL DIMENSIONS
OVERALL DIMENSIONS
Weight
Weight
Net
Net
Packaged SM94-LC: 949.7 grams (2 Ib 1 1/2 oz)
Packaged SM94-LC: 949.7 grams (2 Ib 1 1/2 oz)
Certification
Certification
Eligible to bear CE Marking. Conforms to European EMC Directive
Eligible to bear CE Marking. Conforms to European EMC Directive
89/336/EEC. Meets applicable tests and performance criteria in
89/336/EEC. Meets applicable tests and performance criteria in
European Standard EN55103 (1996) parts 1 and 2, for residential
European Standard EN55103 (1996) parts 1 and 2, for residential
(E1) and light industrial (E2) environments.
(E1) and light industrial (E2) environments.
*S/N ratio is difference between microphone output at 94 dB SPL and
*S/N ratio is difference between microphone output at 94 dB SPL and
microphone self-noise A-weighted.
microphone self-noise A-weighted.
OPERATION
OPERATION
The SM94 is designed for phantom powering by a Shure PS1A
The SM94 is designed for phantom powering by a Shure PS1A
Power Supply, or by any microphone power supply providing 12 to
Power Supply, or by any microphone power supply providing 12 to
48 Vdc phantom voltage, or by any microphone mixer (such as the
48 Vdc phantom voltage, or by any microphone mixer (such as the
Shure SCM262 and SCM268) with a phantom supply. In addition,
Shure SCM262 and SCM268) with a phantom supply. In addition,
the SM94 can be powered by a single 1.5-volt AA alkaline battery.
the SM94 can be powered by a single 1.5-volt AA alkaline battery.
The battery also serves as a backup in case of phantom power
The battery also serves as a backup in case of phantom power
failure. A new alkaline battery will provide up to 5,000 hours of
failure. A new alkaline battery will provide up to 5,000 hours of
continuous microphone operation. Note that the microphone is
continuous microphone operation. Note that the microphone is
powered at all times during battery operation but there is no battery
powered at all times during battery operation but there is no battery
drain during phantom-powered operation.
drain during phantom-powered operation.
BATTERY OPERATION
BATTERY OPERATION
Disconnect the microphone cable, and unscrew the SM94 handle,
Disconnect the microphone cable, and unscrew the SM94 handle,
turning counterclockwise (from top) until the handle is free of the
turning counterclockwise (from top) until the handle is free of the
microphone body. Slide the handle away from the grille, exposing
microphone body. Slide the handle away from the grille, exposing
the battery compartment. Insert a new battery (or replace the old
the battery compartment. Insert a new battery (or replace the old
battery), observing the polarity marking in the compartment.
battery), observing the polarity marking in the compartment.
Slide the handle toward the grille, and tighten the handle by turning
Slide the handle toward the grille, and tighten the handle by turning
it clockwise (from top).
it clockwise (from top).
WIND NOISE
WIND NOISE
Use the optional foam windscreen (A3WS) when using the SM94
Use the optional foam windscreen (A3WS) when using the SM94
outdoors on a windy day, indoors near strong air currents such as
outdoors on a windy day, indoors near strong air currents such as
air-moving equipment, or as a vocal microphone.
air-moving equipment, or as a vocal microphone.
CIRCUIT DESCRIPTION
CIRCUIT DESCRIPTION
A block diagram of the SM94 is shown in Figure 4. The capacitor
A block diagram of the SM94 is shown in Figure 4. The capacitor
cartridge is followed by an impedance converter stage. This stage
cartridge is followed by an impedance converter stage. This stage
has an active load to obtain good load-driving capability with the
has an active load to obtain good load-driving capability with the
low battery voltage of 1.5 volts.
low battery voltage of 1.5 volts.
The audio signal is transformer-coupled for a balanced output to
The audio signal is transformer-coupled for a balanced output to
the microphone connector. An active power supply circuit
the microphone connector. An active power supply circuit
2
2
FIGURE 3
FIGURE 3
250 grams (8.8 oz) less battery
250 grams (8.8 oz) less battery
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