General

UNIDYNE® III MODEL 545SD User Guide

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).

SET SCREW

PLUG ELEMENT

IMPEDANCE SELECTION SOCKET	PIN 3

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)

©2005, Shure Incorporated		Printed in U.S.A.
27D3059 (Rev. 10)