Shure SM90 User Guide
222 HARTREY AVE., EVANSTON, IL. 60204 U.S.A.
AREA CODE 312/866-2200 l CABLE: SHUREMlCRO
THE SOUND OF THE PROFESSlONALS
®
PROFESSIONAL PRODUCTS
the best location for any particular purpose or effect
desired.
The carefully optimized design of the SM90 includes
an entirely new cartridge, developed at Shure. The result
is high output and extremely faithful sound reproduction across the entire audio frequency range. The supplied low-distortion, high-clipping-level preamplifier provides switch-selectable low-frequency Flat or Lo-Cut
response for additional help in obtaining the best possible microphone signal even under difficult conditions.
The SM90 is powered either by two readily available
9-volt alkaline batteries (300 hours continuous battery
life) or by an 11-to-52 Vdc simplex (phantom) supply
from broadcast, sound-reinforcement, or recording
equipment.
The SM90 consists of a small, rugged, surfacemounted microphone finished in professional durable
matte-black enamel; a 7.6m (25 ft) small diameter two-
conductor shielded interconnecting cable with two
3-socket miniature Switchcraft connectors; and a sturdy preamplifier assembly with battery compartment,
battery On/Off switch, green LED battery-condition in-
dicator, low-frequency Flat/Lo Cut switch, and standard
3-pin professional audio connector output.
GENERAL
The SM90 Microphone is designed specifically for
surface-mounted applications. It is a professionalquality permanently-biased condenser microphone with
a hemispherical pickup pattern (omnidirectional in the
hemisphere above the mounting surface.)
The SM90 takes advantage of the well-known principle that, at a barrier or boundary, sound pressure
doubles compared to its value if the boundary is removed. When placed sufficiently near the boundary surface, a microphone has effectively 6 dB higher sensitivity and approximately 3 dB greater rejection of random background noise.
Because of its high sensitivity and extremely flat frequency response, the SM90 can be used for distant
pickup in circumstances where close miking would not
be practical. The low-frequency cutoff switch in the preamplifier permits using the SM90 even in environments
where low-frequency noise (e.g., from fans or air conditioners) would otherwise make distant pickup impossible. And the omnidirectional polar pattern of the SM90
means sound is picked up equally in the full 360° hemisphere around the microphone; there is no off-axis
sound coloration or variation.
The SM90 can also be used for close pickup of an in-
dividual instrument, mounted, for instance, inside the
lid of a grand piano or on the floor next to a bass drum.
Experimentation and critical listening will demonstrate
Features:
l Wide flat frequency response for faithful sound
reproduction across the audio spectrum
l
Switch-selectable 12 dB/octave low-frequency cutoff
permits tailoring response to suit conditions
l Omnidirectional polar pattern for pickup in full
hemisphere surrounding microphone mounting sur-
face
l High sensitivity and high signal-to-noise ratio
l Very low distortion and high output clipping level
l Battery or simplex powering: uses standard 9-volt
alkaline batteries: accepts wide range of simplex
voltages - 11 to 52 Vdc
l Low susceptibility to RFI, electrostatic and electro-
magnetic hum
l Extremely rugged construction of both microphone
and preamplifier for outstanding reliability
l Low profile and matte black finish for unobtrusive
appearance on-camera or onstage; on floor, table,
ceiling, wall, or lectern
l Usable over very wide range of temperature and
humidity
Copyright 1984, Shure Brothers Inc.
27A2162 (DJ)
Printed in U.S.A.
Patent Pending
SPECIFICATIONS
Type
Condenser (electret bias) for surface mounting
Frequency Response
20 to 20,000 Hz at 30° incidence to infinite surface
(see Figure 1)
TYPICAL FREQUENCY RESPONSE
FIGURE 1
Polar Pattern
Omnidirectional in hemisphere above mounting
surface
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 30° incidence to flat surface)
Open Circuit Voltage . . . . . . . . . . . -66.0 dB (0.5 mV)
0 dB = 1V/µbar
Preamplifier Output Clipping Level
than 0.1% THD)
800 ohm load
150 ohm load
Maximum SPL (at 1,000 Hz, sound source at 30° incidence to flat surface)
800 ohm load
150 ohm load
Hum Pickup
-19 dB equivalent SPL in 1 m0e field (60 Hz)
Output Noise
20 dB SPL, A-weighted
23 dB SPL, weighted per DIN 45 405
Signal-to-Noise Ratio
74 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 (NEMA 1604A),
approximately 300 hours continuous with fresh
alkaline batteries
(at 1,000 Hz, measured with sound source
(at 1,000 Hz, less
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0 dBV (1.0V)
-13 dBV (0.22V)
141 dB
131 dB
Simplex
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:
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 total battery voltage). Move to Off to prevent battery drain when unit is not in use.
LED Indicator:
when switch is moved to On to indicate at least 8
hours of battery life remaining.
Flat/Lo Cut Switch:
rolloff below 30 Hz; in Lo Cut position, 12 dB/octave
cutoff below 80 Hz (see Figure 1)
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:
perforated steel grille with replaceable or cleanable
fine mesh screen and foam pad wind/dirt barrier
Preamplifier:
Dimensions
See Figure 2
Environmental Conditions
Operating Temperature: -18° to 57°C (0° to
135°F)
Storage Temperature:
168°F)
Relative Humidity (Operating or Storage):
Net Weight
Microphone: 280 grams (9.9 oz) less cable
Preamplifier:
Voltage:
OVERALL DIMENSIONS
11 to 52 Vdc, operational down to
Move to On to power from
Green LED flashes momentarily
In Flat position, 6 dB/octave
Matte black enamel die-cast base and
Matte black enamel die-cast aluminum
FIGURE 2
-29° to 74°C (-20° to
320 grams (11.3 oz) with batteries
0 to 95%
-2-
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