Shure SM12A User manual

HEAD-WORN MICROPHONE WITH RECEIVER
GENERAL
The Shure Model SM12A Professional Head-Worn Micro-
phone with Receiver is a low-impedance, unidirectional, dy-
namic microphone with an integral earphone assembly. The
SM12A offers convenient, hands-free operation for sports
and news announcing, interviewing and intercommunica-
tion systems, and for special events remote broadcasting. A
close-talking unit, the SM12A can be used under noisy con-
ditions without loss or masking of voice signals. The SM12A
and the supplied dual-spring steel headband is rugged and
reliable. A miniature windscreen to protect against wind
noise and explosive breath sounds and two connector belt
clips are also supplied.
Features:
SClose-talk operation and unidirectional polar pattern for
effective noise reduction
SSmooth natural voice frequency response
SLocking adjustment knob permits boom to pivot 20°in
any direction
SBoom length adjustment through 89 mm (3 1/2 in.)
range
SBuilt-in receiver protection circuit automatically avoids
excessive sound pressure level
SReceiver ear tube adjustable through 55°arc
SLight weight plus dual headband eliminate user fatigue
SDoes not interfere with eyeglasses
SRuggedly constructed of stainless steel, aluminum and
high-impact thermoplastic
SConvenient, secure clips attach connectors to belt or
clothing
RIGHT SIDE OPERATION
As supplied, the microphone is positioned on the left side,
as shown in Figure 1. For right side usage (see photo), re-
move the retaining clip and attach it to the other (unused)
hole in the headband arm so the screw is at the top.
CLEANING THE REVEIVER TIP
A decrease in receiver output may be due to clogging of
the receiver tip. The tip may be cleaned by removing it from
the ear tube and inserting a toothpick or similar device
through the tip hole. If clogging is apparent in the ear tube,
carefully remove the obstruction from the ear tube tip.
CAUTION:Do not disturb the foam damping material lo-
cated just inside the ear tube tip.
WARNING
Sustained high volume levels in conjunction with
a tightly fitting receiver tip may adversely affect the
user’s hearing. Make certain the volume is set to
a confortable listening level and position the re-
ceiver tip at the entrance of the ear.
ASSEMBLY
Microphone
Receiver Tip
Pivot Housing
Retaining
Clip
Pivot
Adjustment
Knob
Headband
Headband
Arm
Boom
SM12A POSITIONED FOR LEFT SIDE OPERATION
FIGURE 1
1. Position the lower headband arms perpendicular to the
headband.
2. Snap the microphone pivot housing into the retaining
clip with the pivot adjustment knob upward and the mi-
crophone toward the front.
Model SM12A User Guide
27B2325 (CC)
2003, Shure Incorporated
Printed in U.S.A.

2
3. Loosen the pivot adjustment knob, position the boom so
that the microphone is near where the side of the mouth
will be, and tighten the pivot adjustment knob.
4. Place the assembled microphone on the user’s head
and pull the headband arms downward until they rest
against the head just over the ears. Position the receiver
tip at the entrance to the ear. (Make certain cable is free
of receiver ear tube.)
5. Loosen the pivot adjustment knob and position the mi-
crophone as close as possible to the corner of the
mouth. For optimum close-talking operation, the micro-
phone should be less than 25 mm (1 in.) from the corner
of the mouth. Be sure to position the microphone at the
corner (not the center) of the mouth to eliminate explo-
sive breath sounds (“pop”). Tighten the adjustment
knob.
6.. Snap the microphone connector belt clip over the
groove in the 3-pin audio connector and the receiver
connector belt clip over the groove in the phone plug.
The clips can now be fastened to the user’s belt or other
clothing. Attach the 3-pin audio connector to the micro-
phone cable and the phone plug to the monitoring unit
cable.
MICROPHONE SPECIFICATIONS
TYPE
Dynamic, Close-Talking
FREQUENCY RESPONSE: At 8 mm (5/16 in.)
50 to 15,000 Hz (see Figure 2)
POLAR PATTERN
Cardioid (unidirectional) response-uniform with frequen-
cy, symmetrical about axis (see Figure 3)
Impedance
Microphone rating impedance is 150 ohms (200 ohms ac-
tual) for connection to microphone inputs rated at 19 to
300 ohms
Sensitivity (close-talked at 1,000 Hz)
Open Circuit Voltage –67.0 dBV/Pa (.45 mV). . . . . . . . .
(1 Pa = 94 dB SPL). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hum Sensitivity (typical)
38.4 dB equivalent SPL in a 1 millioersted field
Phasing
Positive pressure on diaphragm produces positive voltage
on pin 2 of microphone connector
Connector
Male XLR audio connector (TA3M)
Receiver
Type
Dynamic
Frequency Response
70 to 12,000 Hz
Impedance
2,000 ohms at 1 kHz (200-ohms cartridge with matching
transformer in phone plug)
Output Level
105 dB SPL with 1.4V at 1 kHz (1.0 mW into 2 cc cavity)
Phasing
Positive voltage on phone plug tip produces positive pres-
sure in ear tube
Connector
Phone plug (contains matching 200:2,000 ohm transformer)
GENERAL SPECIFICATIONS
Cable
Non-detachable, 1.5m (5 ft), four conductor, shielded,
plastic-jacketed; additional 762 mm (2.5 ft), two-conduc-
tor receiver cable attached to micorphone connector.
Case
Black thermoplastic microphone and pivot housing, anod-
ized aluminum end caps, stainless steel grille, ear tube
and boom
Dimensions
See Figure 4
Net Weight
84 grams (3 ounces) less cable and connectors
Packaged Weight
978 grams (2 lb, 2 1/2 oz)
CERTIFICATION
Eligible to bear CE Marking. Conforms to European EMC Di-
rective 89/336/EEC. Meets applicable tests and perfor-
mance criteria in European Standard EN55103 (1996) parts
1 and 2, for residential (E1) and light industrial (E2) environ-
ments.
ACCESSORIES AND REPLACEMENT PARTS
The following furnished accessories and replacement
parts may be ordered through your Authorized Shure Pro-
fessional Products Dealer or from Shure Incorporated.
Connector Belt Clip RK200BC. . . . . . . . . . . . . . . . . . . . .
Windscreen RK 184WS. . . . . . . . . . . . . . . . . . . . . . . . . .
Carrying Case 90DJ2600. . . . . . . . . . . . . . . . . . . . . . . .
Microphone Cartridge R93. . . . . . . . . . . . . . . . . . . . . . . .
Receiver Cartridge 90EL2600. . . . . . . . . . . . . . . . . . . . .
Headband Assembly RK352. . . . . . . . . . . . . . . . . . . . . .
Receiver Tip 90FS2600. . . . . . . . . . . . . . . . . . . . . . . . . .

3
TYPICAL MICROPHONE FREQUENCY RESPONSE
FIGURE 2
TYPICAL POLAR PATTERN
FIGURE 3

4
EARPHONE VOLUME CONTROL
A simple volume control circuit can be built to enable the
SM12A earphone receiver to be connected to the speaker
output of a power amplifier with an output of up to 200 watts
into 4 ohms. (The volume control need not be connected di-
rectly to the power amplifier. It can also be connected to an
unused phone jack on a working stage monitor.)
WARNING
Although the SM12A’s receiver circuit is protected
against excessive level, it is capable of an output of over
121 dB SPL sufficient to cause hearing damage with
prolonged exposure. Always take care to turn the vol-
ume control on this circuit all the way down before insert-
ing the earpiece into your ear. Then turn the control up
gradually until a confortable listening level is reached.
VOLUME CONTROL
FIGURE 6
PARTS LIST
2 Two-circuit phone jacks. . . . . . . . . . . . . . . . . . . . . . . . .
1 Resistor, 2.2k, 1W. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 Potentiometer, 25k, 1W (or larger). . . . . . . . . . . . . . .
1 Plastic or metal box. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Connecting leads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ARCHITECT’S SPECIFICATIONS
The microphone with receiver shall be the Shure Model
SM12A or equivalent. The microphone shall be a moving–
coil (dynamic) type with a frequency response of 50 to
15,000 Hz. The unit shall have a cardioid polar characteris-
tic. The cancellation at the rear shall be 15 to 20 dB. The mi-
crophone shall be low impedance with a rated impedance of
150 ohms for connection to microphone inputs rated at 19
to 300 ohms.
The microphone output shall be – 66.0 dB where 0 dB =
1 milliwatt per 10 microbars.
The receiver shall be a dynamic type with a frequency re-
sponse of 70 to 12,000 Hz. The receiver shall be sup–plied
with an integral connector–mounted matching transformer
designed with an impedance of 2,000 ohms.
The microphone with receiver shall be a head-worn type,
and shall be provided with a 1.5m (5 ft), non-detachable,
four-conductor (two-conductor shielded) cable with a pro-
fessional three-pin audio connector designed to mate with
Cannon XL series, 3-Pin Mini Connector (TA3M) or equiva-
lent connectors. An additional 762 mm (2.5 ft) cable length
shall be provided between microphone and receiver (phone
plug) connectors. The microphone shall also be provided
with a headband, two connector belt clips, and a foam wind-
screen.
The overall dimensions of the microphone shall be 203
mm (8 in.) in length and 44.5 mm (1–3/4 in.) in maximum
height (pivot housing). The microphone housing shall be
15.9 mm (5/8 in.) in diameter and 14 mm (9/16 in.) in height.
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