Shure SM94-LC Handleiding

Shure Microfoon SM94-LC

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Pagina 1/8

Model SM94 User Guide

27C2689 (Rev. 5)

Printed in U.S.A.

MODEL SM94

UNIDIRECTIONAL CONDENSER MICROPHONE

The Model SM94 is a unidirectional electret condenser

microphone tailored to the instrument miking needs of professional

musicians and sound engineers in both live performance and

sound recording. Its smooth, flat frequency response is free of

either a “presence peak” or a low-frequency rolloff, making it a

perfect choice for all types of musical instruments. The SM94 is

equally at home in sound reinforcement systems or in sound

studios and motion picture/TV scoring stages. When used with the

optional windscreen, the SM94 can be used by vocalists and

speechmakers who desire a wide, flat response with minimum

coloration.

The SM94 can be powered by any phantom power source, or by

an internal 1.5-volt AA battery. The battery, which serves as a

backup power source in the event of phantom power failure, can

provide up to 5,000 hours of continuous operation.

The SM94 is supplied with a swivel adapter for use on a

microphone stand, boom or gooseneck, and a zippered vinyl

storage bag. Model SM94-LC is supplied without a cable.

Accessories include a foam windscreen (A3WS), two-channel

phantom power supply (PS1A), and 7.6 m (25 ft.) microphone

cable (C25J).

Features

• Wide, flat response for optimum musical instrument sound re-

production

• Full spectrum sound–no presence peak or low-end rolloff

• Cardioid polar pattern that is uniform with frequency and sym-

metrical about axis for maximum rejection of unwanted sound

and minimum of-axis coloration

• Very low susceptibility to RF and electromagnetic hum

• Low distortion output and wide dynamic range for variety of load

impedances

• Shock–mounted cartridge for reduced handling noise

• Accepts 12 to 48 Vdc phantom power

• Rugged all–metal construction

• Usable over wide range of environmental conditions

• Built–in battery power backup

• Optional foam windscreen

SPECIFICATIONS

Type

Cardioid condenser (electret bias)

Frequency Response

40 to 16,000 Hz (see Figure 1)

TYPICAL FREQUENCY RESPONSE

FIGURE 1

Polar Pattern

Cardioid (unidirectional)–uniform with frequency,

symmetrical about axis (see Figure 2)

TYPICAL POLAR PATTERNS

FIGURE 2

Output Impedance

Rated at 150 ; 200 actual

Recommended Minimum Load Impedance

800

Sensitivity (at 1,000 Hz)

Open Circuit Voltage: –49 dBV/Pa (3.5 mV) (phantom)

–50 dBV/Pa (3.2 mV) (battery) (1 Pa = 94dB SPL)

Output Clipping Level (1 kHz, 3% THD)

800- Load–14 dBV (0.63 V) (phantom), 1% THD;

–23 dBV (0.71 V) (battery), 3% THD

Total Harmonic Distortion

< 0.25% (130 dB SPL at 250 Hz into 800 load)

Maximum SPL

800 Load: 141 dB (phantom), 123 dB (battery)

Hum Pickup

–3 dB equivalent SPL in a 1 millioersted field (60 Hz)

Output Noise (equivalent sound pressure levels;

measured with true rms voltmeter)

22 dB typical, A-weighted

25 dB typical, weighted per DIN 45 505

Dynamic Range

119 dB (phantom); 101 dB (battery) (maximum SPL,

2000– load, to A–weighted noise level)

Signal-to-Noise Ratio

72 dB (IEC 651)* at 94 dB SPL

Overvoltage Protection

Maximum External Voltage Applied to Pins 2 and 3

with respect to Pin 1: +52Vdc

Reverse polarity protected to 75 Vdc

Polarity

Positive pressure on diaphragm produces positive

voltage on pin 2 relative to pin 3

Cartridge Capacitance

24 pF

Power

Phantom Operation

Supply Voltage: 11 to 52 Vdc, (+) pins 2 and 3

Current Drain: 1.0 to 1.2 mA max. at 52 Vdc

Battery Operation

Type: 1.5 V alkaline, AA size (NEDA 15A)

Life: Up to 5,000 hours with fresh battery

Environmental Conditions

Temperature:

Storage: . . . . . . . –29 to 74 C (–20 to 165 F)

Operating: –6.7 to 49 C (20 to 120 F)

Humidity:

Storage . . . . 0–95% relative humidity at room

temperature (72 to 80 F, 22 to 27 C)

Connector

XLR professional audio 3-Pin

Case

Steel and brass construction with gray finish and

stainless steel mesh grille

Dimensions

See Figure 3

OVERALL DIMENSIONS

FIGURE 3

Weight

Net 250 grams (8.8 oz) less battery

Packaged SM94-LC: 949.7 grams (2 Ib 1 1/2 oz)

Certification

Eligible to bear CE Marking. Conforms to European EMC Directive

89/336/EEC. Meets applicable tests and performance criteria in

European Standard EN55103 (1996) parts 1 and 2, for residential

(E1) and light industrial (E2) environments.

*S/N ratio is difference between microphone output at 94 dB SPL and

microphone self-noise A-weighted.

OPERATION

The SM94 is designed for phantom powering by a Shure PS1A

Power Supply, or by any microphone power supply providing 12 to

48 Vdc phantom voltage, or by any microphone mixer (such as the

Shure SCM262 and SCM268) with a phantom supply. In addition,

the SM94 can be powered by a single 1.5-volt AA alkaline battery.

The battery also serves as a backup in case of phantom power

failure. A new alkaline battery will provide up to 5,000 hours of

continuous microphone operation. Note that the microphone is

powered at all times during battery operation but there is no battery

drain during phantom-powered operation.

BATTERY OPERATION

Disconnect the microphone cable, and unscrew the SM94 handle,

turning counterclockwise (from top) until the handle is free of the

microphone body. Slide the handle away from the grille, exposing

the battery compartment. Insert a new battery (or replace the old

battery), observing the polarity marking in the compartment.

Slide the handle toward the grille, and tighten the handle by turning

it clockwise (from top).

WIND NOISE

Use the optional foam windscreen (A3WS) when using the SM94

outdoors on a windy day, indoors near strong air currents such as

air-moving equipment, or as a vocal microphone.

CIRCUIT DESCRIPTION

A block diagram of the SM94 is shown in Figure 4. The capacitor

cartridge is followed by an impedance converter stage. This stage

has an active load to obtain good load-driving capability with the

low battery voltage of 1.5 volts.

The audio signal is transformer-coupled for a balanced output to

the microphone connector. An active power supply circuit

regulates the phantom voltage, and the 1.5-volt battery provides

instantaneous backup in case the phantom power supply fails. The

regulator/reverse voltage protector provides built-in protection

against miswired cables and equipment.

TROUBLESHOOTING

Due to the circuit complexity of the SM94, only basic servicing is

recommended. The following steps should be taken if problems

arise:

1. Check the power supply output voltage. For the Shure PS1A,

this should be 21.5, ±1.5 Vdc, open circuit.

2. Check the voltage on connector pins 2 and 3 (at back of

connector, with cable connector removed from shell, but

connected to microphone). The voltage at pins 2 and 3 with

reference to pin 1 should be between 10 and 48 Vdc.

3. If the microphone does not work on phantom power, battery

operation may still be possible. Similarly, if battery operation is

impaired, the SM94 may still operate on phantom power. In

either case, you should send the microphone to an Authorized

Shure Service Center at your earliest opportunity.

ARCHITECTS' SPECIFICATIONS

The microphone shall be a condenser microphone with a

frequency response of 40 to 16,000 Hz. It shall have a cardioid

directional characteristic, with cancellation at the sides of 6 dB and

a minimum cancellation at the rear of 15 dB at 1 kHz. The

microphone shall have a rated output impedance of 150 for

connection to microphone inputs of 150 or higher. The open

circuit voltage shall be –49 dBV/Pa (3.5 mV) dB equals 1 volt per

Pascal).

The overall dimensions shall be 190.5 mm (7–1/2 in.) in length by

27.7 mm (1–3/32 in.) in diameter. The handle diameter shall be

24.1 mm (15/16 in.) The weight shall be 250 grams (8.8 oz).

The microphone shall be capable of being powered by a phantom

power supply with an output of 11 to 52 Vdc, or by a mixer, audio

console or tape recorder capable of supplying 11 to 52 Vdc, or by

an internal 1.5-volt battery.

The microphone shall be a Shure Model SM94.

FURNISHED ACCESSORIES

Swivel Adapter .................................................................. A25D

Carrying/Storage Bag ...................................................... 26A13

OPTIONAL ACCESSORIES

Phantom Power Supply.................................................... PS1A

Switch-Selectable Attenuator ........................................ A15AS

Isolation Mount ................................................................. A53M

Windscreen ..................................................................... A3WS

7.6 m (25 ft.) Cable .......................................................... C25J

REPLACEMENT PARTS

Screen and Grille ......................................................... RK255G

BLOCK DIAGRAM

FIGURE 4

CAPACITOR

CARTRIDGE

FET

IMPEDANCE CONVERTER

WITH ACTIVE LOAD

BALANCED

TRANSFORMER

BATTERY

REGULATOR/

REVERSE VOLTAGE

PROTECTOR

LF RESPONSE

FILTER

CLASS A

COMPOUND

AMPLIFIER

RFI

FILTER

Product specificaties

Merk:	Shure
Categorie:	Microfoon
Model:	SM94-LC
Kleur van het product:	Grijs
Soort:	Microfoon voor studio's
Connectiviteitstechnologie:	Bedraad
Aansluiting:	XLR-3
Microphone direction type:	Cardioïde
Gevoeligheid microfoon:	49 dB
Frequentie microfoon:	40 - 16000 Hz
Type batterij:	AA
Gewicht microfoon:	250 g