Shure SM91 Half-Cardioid Surface-Mounted Condenser Microphone
Shure SM91 Cardioid Condenser Microphone
Preamplifier Sold Separately
The SM91 Microphone is designed specifically for surface-mounted applications. It is a professional quality permanently-biased condenser microphone with a half-cardioid directional pattern (cardioid in the hemisphere above the mounting surface.)
Features:
- Wide flat frequency response for accurate sound reproduction across the audio spectrum
- Switch-selectable 12 dB/octave low-frequency cutoff permits tailoring response to suit conditions
- Half-cardioid polar pattern minimizes pickup from rear of microphone, permits aiming microphone, e.g., toward performers and away from audience, or toward singers and away from instruments
- High sensitivity and high signal-to-noise-ratio
- Very low distortion and high output clipping level
- Battery or simplex powering: uses standard 9-volt alkaline batteries; accepts wide range of simplex voltages – 11 to 52 Vdc
- Low susceptibility to RFI, electrostatic and electromagnetic hum
- Extremely rugged construction of both microphone and preamplifier for outstanding reliability
- Low profile and matte black finish for unobtrusive appearance on-camera or onstage; on floor, table, ceiling, wall, or lectern
- Usable over very wide range of temperature and humidity
Specifications:
- Type: Cardioid condenser (electret bias) for surface mounting
- Frequency Response: 20 to 20,000 Hz at 30° incidence to infinite surface
- Polar Pattern: Half-cardioid (cardioid in hemisphere above mounting surface), uniform with frequency, symmetrical about axis
- Output Impedance:
- Rated at 150 ohms (90 ohms actual)
- Recommended minimum load impedance: 800 ohms (May be used with loads as low as 150 ohms with reduced clipping level)
- Output Level (at 1,000 Hz, measured with sound source at 30° incidence to infinite surface):
- Open Circuit Voltage: -71.5 dB (0.27 mV)
- 0 dB = 1 V/μbar
- Preamplifier Output Clipping Level (at 1,000 Hz, less than 0.1% THD):
- 800 ohm load: 0 dBV (1.0V)
- 150 ohm load: -13 dBV (0.22V)
- Maximum SPL (at 1,000 Hz, sound source at 30° incidence to infinite surface):
- 800 ohm load: 146.5 dB
- 150 ohm load: 136.5 dB
- Hum Pickup: -13.5 dB equivalent SPL in 1 m0e field (60 Hz)
- Output Noise:
- 25.5 dB SPL, A-weighted
- 28.5 dB SPL, weighted per DIN 45 405
- Signal-to-Noise Ratio: 68.5 dB re 94 dB SPL
- Dynamic Range: 121 dB
- Phasing: Positive pressure on diaphragm produces positive voltage on pin 2 relative to pin 3 of preamplifier output connector.
- Power:
- Battery: Two 9-Vdc alkaline (NEDA 1604A), approximately 300 hours continuous with fresh alkaline batteries
- Simplex Voltage: 11 to 52 Vdc, operational down to 9 Vdc; 1.8 mA current drain; permissible to use simplex power with batteries in place or removed
- Switches and Indicator:
- Two recessed slide switches and green LED indicator on top surface of preamplifier assembly
- Battery On/Off Switch: Move to On to power from batteries or to use batteries as backup power in case of interruption to external power supply (no battery drain occurs as long as simplex voltage source is greater than battery voltage). Move to Off to prevent battery drain when unit is not in use.
- LED Indicator: Green LED flashes momentarily when switch is moved to On to indicate at least 8 hours of battery life remaining.
- Flat/Lo Cut Switch: In Flat position, 6 dB/octave rolloff below 30 Hz; In Lo Cut position, 12 dB/octave rolloff below 80 Hz
- Cable: 7.6m (25 ft) two-conductor shielded, small diameter, interconnecting cable with 3-socket miniature Switchcraft connector on each end to mate with microphone output connector and preamplifier input connector
- Case:
- Microphone: Matte black enamel die-cast base and perforated steel grille with replaceable or cleanable fine mesh screen and foam pad wind/dirt barrier
- Preamplifier: Matte black enamel die-casting
- Dimensions(L x H x W):
- Microphone: 95.3mm(3 3/4in) x 129mm(5 3/32in) x 15.9mm(5/8in)
- Preamplifier: 60.8mm(2 26/64in) x 112mm(4 25/64in) x 34.9mm(1 3/4in)
- Environmental Conditions:
- Operating Temperature: -18° to 57°C (0° to 135°F)
- Storage Temperature: -29° to 74°C (-20° to 168°F)
- Relative Humidity (Operating or Storage): 0 to 95%
- Net Weight
- Microphone: 263 grams (9.3 oz) less cable
- Preamplifier: 435 grams (15.4 oz) less batteries
