Shure SM12A User manual

Model SM12A User Guide
©2005, Shure Incorporated
27C2325 (Rev. 8)
Printed in U.S.A.
HEAD-WORN MICROPHONE WITH RECEIVER
GENERAL
The Shure Model SM12A Professional Head-Worn Microphone
with Receiver is a low-impedance, unidirectional, dynamic
microphone with an integral earphone assembly. The SM12A
offers convenient, hands-free operation for sports and news
announcing, interviewing and intercommunication systems,
and for special events remote broadcasting. A close-talking
unit, the SM12A can be used under noisy conditions 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:
• Close-talk operation and unidirectional polar pattern for
effective noise reduction
• Smooth natural voice frequency response
• Locking adjustment knob permits boom to pivot 20
° in any
direction
• Boom length adjustment through 89 mm (3 1/2 in.) range
• Built-in receiver protection circuit automatically avoids
excessive sound pressure level
• Receiver ear tube adjustable through 55
° arc
• Light weight plus dual headband eliminate user fatigue
• Does not interfere with eyeglasses
• Ruggedly constructed of stainless steel, aluminum and
high-impact thermoplastic
• Convenient, 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),
remove the retaining clip and attach it to the other (unused)
hole in the headband arm so the screw is at the top.
CLEANING THE RECEIVER 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
located just inside the ear tube tip.
ASSEMBLY
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
microphone toward the front.
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.
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 receiver tip at the entrance of the ear.
Microphone
Receiver Tip
Pivot Housing
Retaining
Clip
Pivot
Adjustment
Knob
Headband
Headband
Arm
Boom

2
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
microphone as close as possible to the corner of the
mouth. For optimum close-talking operation, the
microphone 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
explosive 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
microphone 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 frequency, sym-
metrical about axis (see Figure 3)
Impedance
Microphone rating impedance is 150 ohms (200 ohms actual)
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 trans-
former 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 pressure 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, plas-
tic-jacketed; additional 762 mm (2.5 ft), two-conductor receiver
cable attached to microphone connector.
Case
Black thermoplastic microphone and pivot housing, anodized
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
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.
ACCESSORIES AND REPLACEMENT PARTS
The following furnished accessories and replacement parts
may be ordered through your Authorized Shure
Professional 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
directly to the power amplifier. It can also be connected to
an unused phone jack on a working stage monitor.)
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
characteristic. The cancellation at the rear shall be 15 to 20
dB. The microphone 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
response 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
professional three-pin audio connector designed to mate
with Cannon XL series, 3-Pin Mini Connector (TA3M) or
equivalent 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 windscreen.
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.
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 volume control on
this circuit all the way down before inserting the earpiece
into your ear. Then turn the control up gradually until a
confortable listening level is reached.
SHURE Incorporated http://www.shure.com
United States, Canada, Latin America, Caribbean:
5800 W. Touhy Avenue, Niles, IL 60714-4608, U.S.A.
Phone: [phone] U.S. Fax: [phone] Intl Fax: [phone]
Europe, Middle East, Africa:
Shure Europe GmbH, Phone: [phone] Fax: [phone]
Asia, Pacific:
Shure Asia Limited, Phone: [phone] Fax: [phone]