GENERALThe Shure 550L is an omnidirectional dynamic base sta-

tion microphone with a frequency response specially tai-lored for voice intelligibility. It is equally useful for radio com-munications, paging and dispatching systems, and itslow-impedance connection makes it adaptable to most PAamplifiers. The low-impedance design also makes it usefulfor long runs of cable, or under severe hum disturbance con-ditions.

The microphone is not affected by heat or humidity. Its ex-clusive ARMO-DUR case is immune to oil, grease, fumes,salt spray, sun, rust, and corrosionand is outstanding in itsability to resist mechanical shocks and vibration. The Mil-lion-Cycle leaf-type switch is designed to withstand rigor-ous operating conditions and constant use.Features Low-impedance operation Crisp, natural, high-intelligibility voice response Fingertip control bar actuates microphone circuit and

external relay or control circuit Long-life switch meets rigorous requirements of com-

munications and paging systems Sturdy, high-impact ARMO-DUR base and microphone

case resists corrosion Reliability under all operating conditions Neoprene feet prevent microphone slippingPRESS-TO-TALK SWITCH OPERATION

The fingertip control bar is a non-locking switch; simply de-press the control bar and release after transmission.WIRING

Figure 1 shows the internal wiring of the 550L microphone.

BLACK

WHITE

RED

BLACK

WHITE

GREEN

SHIELD

TRANSMIT

INTERNAL CONNECTIONSFIGURE 1

The 550L may be wired for balanced or unbalanced op-eration. For unbalanced operation, the green cable wire isconnected to the audio input, the white cable wire is con-nected to the audio ground, and the shield is connected tothe chassis ground. See Table 1.

For balanced operation, the green cable wire is connectedto the audio input positive (+), the white wire is connected tothe audio negative (), and the shield is connected to thechassis ground. See Table 1.

Table 1. Cable-to-Connector WiringINPUT TYPE WIRE

COLORFUNCTION XLR

CONNECTOR1/4 IN.

PHONEPLUG

GREEN AUDIO PIN 2 TIP

UNBALANCED WHITE AUDIO GROUND PIN 3 SLEEVE

SHIELD CHASSIS GROUND PIN 1 SLEEVE

GREEN AUDIO + PIN 2 TIP

BALANCED WHITE AUDIO PIN 3 RING

SHIELD CHASSIS GROUND PIN 1 SLEEVE

NOTE: The red and black wires are not part of the audio cir-cuit. These wires provide a contact closure when the micro-phone switch is depressed. This closure may be used tocontrol an external relay or transmit/receive circuit.

IMPEDANCE MATCHINGLow-impedance operation is extremely useful where long

cable lengths are required, or under conditions of severehum disturbance. The permissible cable length is practicallyunlimited, since neither response nor level is appreciably af-fected. Shure A95 Series Line Matching Transformers areavailable for use in those cases where a low-impedance mi-crophone is to be used with an amplifier with a high-imped-ance input. These transformers provide a proper impedancematch between a 19- to 300-ohm microphone and a high-im-pedance input, and are available with various input and out-put connectors.

Model 550L User Guide

27B8090 (TL)2000, Shure Incorporated Printed in Mexico

SPECIFICATIONSType

DynamicFrequency Response

150 to 6,000 Hz (see Figure 2)

20 200001000 1000050 10098765432 98765432

+10

0

10

Hz

dB

TYPICAL FREQUENCY RESPONSEFIGURE 2

Polar PatternOmnidirectional

Impedance (at 1,000 Hz)Microphone rating impedance is 150 ohms (220 ohmsactual) for connection to microphone inputs rated at75 to 300 ohms

Output Level (at 1,000 Hz)Open Circuit Voltage 54.0 dB/Pa (2.0mV). . . . . . . . . (1 Pa = 94 dB SPL)

SwitchPress-to-Talk Switch actuates microphone circuit andexternal relay or control circuit. Microphone circuitnormally open.

Cable2.1m (7 ft) four-conductor, two-conductor shielded,non-detachable

CaseBrown ARMO-DUR with dull chrome-plated steelscreen

DimensionsSee Figure 3

57 mm(2-1/4 IN.)

57 mm(2-1/4 IN.)

12.7 mm(1/2 IN.)TRAVEL

4.8 mm(3/16 IN.)

264 mm(10-3/8 IN.)

2.8 mm(7/64 IN.)

28.6 mm(1-1/8 IN.)

149 mm(5-7/8 IN.)

66.7 mm(2-5/8 IN.)

44.4 mm(1-3/4 IN.)

OVERALL DIMENSIONSFIGURE 3

Net Weight836 grams (1 lb, 13-1/2 oz)

Shipping Weight1.12 kilograms (2 lb, 7-1/2 oz)

CertificationConforms to European Union directives, eligible tobear CE marking; meets European Union EMC Immu-nity Requirements (EN 500821, 1992).

REPLACEMENT PARTSCartridge R96. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cable C32C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Switch RK321S. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

For additional service or parts information, please contactthe Shure Service Department at 18005162525. Out-side the United States, please contact your authorizedShure Service Center.

SHURE Incorporated Web Address: http://www.shure.com222 Hartrey Avenue, Evanston, IL 602023696, U.S.A.Phone: 847-8662200 Fax: 847-866-2279In Europe, Phone: 49-7131-72140 Fax: 49-7131-721414In Asia, Phone: 852-2893-4290 Fax: 852-2893-4055Elsewhere, Phone: 847-8662200 Fax: 847-866-2585