Shure 540SH User Guide

23.9mm	g-27THREAD"f42,1	mm 4
05/16 IN)	(1	-23/32 IN.)

OVERALL DIMENSIONS

FIGURE 2

Net Weight (less cable) 425 grams (15 oz)

Packaged Weight

1.07 kg (2 Ib, 6 oz)

RESPONSE SELECTION

The Model 540SH SONODYNE@II frequency response can be tailored for low-frequency rolloff or midrange emphasis as shown in Figure 1. Both the rolloff and emphasis are desirable if the microphone is used for voice communication or in a paging system, since the tailored response enhances intelligibility of the speaking voice. The microphone is supplied with the extended low and midrange response shown in the solid line curve of Figure 1. To modify the microphone response proceed as follows.

A.Provide midrange emphasis:

1.Hold the microphone in a vertical position; unscrew (turn counterclockwise) and remove the microphone grille-cap assembly (see Figure 3).

2.Remove the perforated aluminum resonator plate (used for extended response); substitute the 18-hole resonator plate (supplied), and add one spacer (for a total of two).

3.Reassemble the grille-cap to the microphone, making certain that the cartridge is properly seated. Tighten securely.

B.Provide low-frequency rolloff:

1.Locate the threaded hole at the back of the microphone (see Figure 3).

2.Use a small screwdriver to remove the headless No. 4-40 set screw in the threaded hole. Opening the acoustic port produces the low-frequency rolloff shown in Figure 1.

ACOUSTIC

rSTEEL SPACERS

LLE-GAP

i1)

R E s o N m o d	GARTwDGEJ	fMcRoPHoNE cnse	REAR VIEW
PLATE			OF MICROPHONE

RESPONSE SELECTION

FIGURE 3

IMPEDANCE SELECTION

The Model 540SH is supplied connected for lowimpedance operation. The low-impedance connection is recommended where long cable lengths are required or under conditions of severe hum disturbance. The permissible cable length is practically unlimited since neither response nor level is appreciably affected by long cables. Shure Model A95 Series Line Matching Transformers are available for use when a lowimpedance microphone line is desirable but the associated amplifier has a high-impedance input. These transformers provide a proper impedance match between a 19 to 300 ohm microphone line and a highimpedance input and are available with various input and output connectors.

To change the Model 540SH to high impedance, proceed as follows.

1.Remove the two screws that hold the switch.

2.Gently pull the switch and its plastic housing forward out of the swivel taking care not to break any leads.

3.With a long-nose pliers, lift upward and disconnect the 2-terminal black plastic impedance selection socket from the back of pin 3 of the audio connector. Take care not to break leads while performing this operation.

4.With the long-nose pliers, replace the impedance selection socket with pin 3 of the audio connector inserted in socket terminal "H". Press the plastic socket firmly in place.

5.Reassemble the switch housing, switch, and switchplate in the swivel taking care not to pinch any leads.

6.Fasten securely with the two previously removed screws.

CONNECTIONS

When using the microphone in low-impedance, the BLACK and WHITE cable leads are the "hot" conductors for balanced-line connections; the shield is connected to the chassis or amplifier ground.

When using the microphone in high impedance, the WHITE cable lead is the "hot" conductor; the shield is connected to the chassis or amplifier ground. The BLACK cable lead should be insulated.

PHASING

To test two microphones andlor their cables for proper phasing, 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 they are in phase with each other. If the sound drops drastically, or if a dead spot is found when talking between the two microphones, either the microphones or their cables (low impedance only) are out of phase. All cables and microphones should be tested in this manner to insure that they are in phase with each other.

To change the phase of a low-impedance microphone cable, either use a Shure A15PRS Phase Reverser or interchange the wires connected to pins 2 and 3 of the connector. To change the phase of a microphone,