General Description

The Model 545SD is a dual-impedance, unidirectional, dynamic microphone. Shipped connected for low-impedance operation, it features a silent magnetic reed on/off switch.

The Classic Unidyne is a favorite for instrument pickup and recording,and can be used on lecterns for public address systems such as those used in political conventions and legislatures, convention halls, hotels, public auditoriums, stadiums, schools, and churches.


  • Exceptionally uniform cardioid pattern minimizes feedback in PA applications
  • Selectable dual-impedance operation
  • Silent magnetic reed on/off switch with lock option
  • Cardioid dynamic
  • Frequency response: 50 to 15,000 Hz


When using the microphone with a balanced input, pins 2 and 3 are the audio signal carriers. When using the microphone with an unbalanced input, use a cable wired with pin 2 as the signal carrier and pin 3 connected to the cable shield (ground), such as the Shure C20AHZ high-impedance cable.

Impedance Selection

The microphone is shipped connected for low impedance operation. To change to high impedance, proceed as follows:

  1. Remove plug element at receptacle end of microphone by turning slotted setscrew in (counterclockwise) and carefully withdrawing plug element from case.
  2. Disconnect 2-terminal impedance selection socket from rear of plug element.
  3. Reconnect 2-terminal impedance selection socket in reverse position so that pin 3 of plug element is inserted in socket terminal "H" (White).
  4. Reassemble plug element into microphone and seal setscrew securely by turning out (clockwise).



All cables and microphones should be tested to ensure that they have the same polarity. To test two microphones and/or their cables for proper polarity, connect them to an amplifier and talk or sing into them while holding them three or four inches apart. The sound from the speakers should be the same when talking into either microphone or directly between them. If the sound drops drastically, or if a dead spot is found when talking between the two microphones, either the microphones or their cables have opposite polarity.

To change the polarity of a microphone cable, either use a Shure A15PRS phase reverser or interchange the wires connected to pins 2 and 3 of the three-pin connector at one end of the cable. To change the polarity of a microphone, the microphone cartridge leads must be interchanged. This should be performed by your dealer, the Shure Factory Service Department, or other qualified service personnel.



Dynamic (moving coil)

Frequency Response

50 to 15,000 Hz


Dual. Microphone rating impedance is 150 ohms (250 ohms actual) for connection to microphone inputs rated at 19 to 300 ohms and 'High' for connection to high-impedance microphone inputs. Wired for low impedance as supplied. To change impedance, see sections on Impedance Selection and Connections.

Output Level

Open Circuit Voltage [1], at 1kHz

L -58.0 dB (1.3 mV
H -35.0 dB (17.6 mV


Positive pressure on diaphragm produces positive voltage on pin 2 with respect to pin 3


Built-in magnetic reed on/off switch with lockplate. To lock switch in the ON position, remove screw on lockplate and turn lockplate 180°. Reassemble and tighten screw.

Cartridge Shock Mount

Internal rubber vibration isolator

Swivel Adapter

Positive action, adjustable through 90° from vertical to horizontal, permits easy removal for handheld use, suitable for mounting on stand with 5/8 in.-27 thread


Chrome-plated die casting with ARMO-DUR grille and stainless steel screen

Net Weight

less cable

255  g (9oz.)


Furnished Accessories

Microphone Clip for SM58, SM57, SM87A, BETA87A, BETA87C, PGA57, PGA58, PGA48, PGA81 A25D

Replacement Parts

Cartridge for 544 Series, 545 Series R45
Grille for Shure SM57 and 545SD RK244G

Optional Accessories

Line Matching Transformers A95
Shock Stopper® Isolation Mount A55M
Shock Stopper Isolation Mount A55HM
Over/Under Dual Mount for two microphones: SM57, BETA57A or 545 Series microphones A26M
Gray Locking Foam Windscreen for 545 Series, SM57 A2WS-GRA
Black Locking Foam Windscreen for 545 Series, SM57 A2WS-BLK
7.6 m (25 ft.) Cable (XLR-XLR) C25J
20' Cable with ¼" Phone Plug on Equipment End (Pin 2 Hot) C20AHZ


This product meets the Essential Requirements of all relevant European directives and is eligible for CE marking.

The CE Declaration of Conformity can be obtained from:

Authorized European representative:

Shure Europe GmbH

Headquarters Europe, Middle East & Africa

Department: EMEA Approval

Jakob-Dieffenbacher-Str. 12

75031 Eppingen, Germany

Phone: +49-7262-92 49 0

Fax: +49-7262-92 49 11 4