Shure M545SD - Manual

UNIDYNE

®

III MODEL 545SD

User Guide

©

2005, Shure Incorporated

27D3059 (Rev. 10)

Printed in U.S.A.

GENERAL

The UNlDYNE

®

III Model 545SD is a dual-impedance, unidirectional,

dynamic microphone. Shipped connected for low-impedance opera-

tion, it features a silent magnetic reed on/off switch.
The UNlDYNE III 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.

FEATURES

• 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

CONNECTIONS

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 C20HZ high-impedance cable.

IMPEDANCE SELECTION

The microphone is shipped connected for low impedance

operation. To change to high impedance, proceed as follows (refer

to Figure 1):
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 ter-
minal “H” (White).

4. Reassemble plug element into microphone and seal setscrew

securely by turning out (clockwise).

IMPEDANCE SELECTION-

RECEPTACLE END OF MICROPHONE

FIGURE 1

POLARITY

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.

SPECIFICATIONS

Type

Dynamic

Frequency Response

50 to 15,000 Hz (see Figure 2)

Polar Pattern

Cardioid (unidirectional)-uniform with frequency, symmetrical
about axis (see Figure 3)

lmpedance

Dual. Microphone rating impedance is 150 ohms (250 ohms ac-
tual) 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 lmpedance Selection and Connections.

Output Level

(at 1,000 Hz)

“L”

“H”

Open Circuit Voltage*

-58.0 dB

-35.0 dB

(1.3 mV)

(17.6 mV)

*0 dB = 1 volt per Pascal (1 Pa = 94 dB SPL)

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SET SCREW

PLUG ELEMENT

IMPEDANCE SELECTION SOCKET

PIN 3