Shure SM81 Handleiding

Shure Microfoon SM81

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MODEL SM81

UNIDIRECTIONAL CONDENSER MICROPHONE

The Shure Model SM81 is a high-quality, unidirectional

condenser microphone designed for studio recording, broad-

casting, and sound reinforcement. Its wide frequency re-

sponse, low noise characteristics, and low RF susceptibility

have made it a standard for applications involving acoustic in-

struments, especially guitar, piano, and cymbals.

The SM81 is ruggedly constructed. It operates on phantom

power and performs over a wide range of temperatures and hu-

midity conditions. It is furnished with a swivel adapter, attenua-

tor-switch lock, foam windscreen, and case for carrying and

storage. Other accessories are available.

Model SM81 Features

•20 Hz to 20 kHz frequency response

•Flat response curve for accurate reproduction of sound

sources

•Low noise and high output clipping level

•Low distortion over a wide range of load impedances

•Cardioid polar pattern, uniform with frequency and symme-

tric about axis, providing maximum rejection and minimum

coloration of off-axis sounds

•Low RF susceptibility

•Selectable low-frequency response: flat, 6 or 18 dB/octave

rolloﬀ

•0 dB/10 dB lockable attenuator switch

•Phantom powering (DIN 45 596 voltages of 12 to 48 Vdc)

•Rugged steel construction for durability

•Field-usable over wide range of temperature and humidity

conditions

SPECIFICATIONS

Type

Condenser (electret bias)

Frequency Response

20 to 20,000 Hz (see Figure 1)

20 200001000 10000

50 100

98765432 98765432

+10

–10

1 METER

TYPICAL FREQUENCY RESPONSE

FIGURE 1

Polar Pattern

Cardioid (unidirectional) response—uniform with

frequency, symmetrical about axis (see Figure 2)

150o

120o

150o

120o

180o

30o

60o

90o

30o

60o

90o

–5 dB

–10 dB

–15 dB

–20 dB

500 kHz

100 Hz

1 kHz

150o

120o

150o

120o

180

30o

60 o

90o

30 o

60o

90o

–5 dB

–10 dB

–15 dB

–20 dB

2 kHz

5 kHz

10 kHz

TYPICAL POLAR PATTERNS

FIGURE 2

Output Impedance

Rated at 150 Ω (85 Ω actual)

Recommended minimum load impedance: 800 Ω (May

be used with loads as low as 150 Ω with reduced clip-

ping level)

Output Configuration and Connector

Balanced, transformer-coupled output; male XLR con-

nector

Sensitivity (at 1,000 Hz)

Open Circuit Voltage –45 dBV/Pascal (5.6 mV). . . . . . . (1 Pascal = 94 dB SPL)

Clipping Level (at 1,000 Hz)

800 Ω Load –4 dBV (0.63 V). . . . . . . . . . . . . . . . . . . . . . .

150 Ω Load –15 dBV (0.18 V). . . . . . . . . . . . . . . . . . . . . .

Total Harmonic Distortion

Less than 0.5% (131 dB SPL at 250 Hz into 800 Ω load)

Model SM81 User Guide

27B2916 (BJ)

E2002, Shure Incorporated Printed in U.S.A.

Maximum SPL (at 1,000 Hz)

800 Ω load 136 dB (attenuator at 0). . . . . . . . . . . . . . . .

146 dB (attenuator at –10)

150 Ω load 128 dB (attenuator at 0). . . . . . . . . . . . . . . .

138 dB (attenuator at –10)

Hum Pickup

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

Self-Noise (equivalent sound pressure levels; measured

with true rms voltmeter)

16 dB typical, A-weighted

19 dB typical, weighted per DIN 45 405

Signal-to-Noise Ratio

78 dB (IEC 651)* at 94 dB SPL

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

and microphone self-noise A-weighted.

Overvoltage and Reverse Polarity Protection

Max. external voltage applied to pins 2 and 3 with

respect to pin 1 + 52 Vdc. . . . . . . . . . . . . . . . . . . . . .

Reverse polarity protection 200 mA max.. . . . . . . . . . . .

(diode-clamped)

Polarity

Positive pressure on diaphragm produces positive volt-

age on pin 2 relative to pin 3

Cartridge Capacitance

54 pF

Low Frequency Response Switch Positions

Flat; –6 dB/octave below 100 Hz; –18 dB/octave below

80 Hz

Attenuator Switch Positions (Lockable)

0 or –10 dB

Power

Supply Voltage 11 to 52 Vdc, positive, pins 2 and 3. .

Current Drain 1.2 mA max.. . . . . . . . . . . . . . . . . . . . . . . .

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)

Case

Steel construction with vinyl metallic paint ﬁnish and

stainless steel screens

Dimensions

See Figure 3

Weight

Net 230 grams (8 oz). . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Packaged 740 grams (1 lb 10 oz). . . . . . . . . . . . . . . . . .

Certiﬁcation

Eligible to bear CE marking. Conforms to European

EMC Directive 89/336/EEC. Meets applicable tests and

performance criteria in European EMC Standard EN

55103 (1996) parts 1 and 2 for residential (E1) and light

industrial (E2) environments.

OPERATION

Power

The SM81 requires phantom power. This may be supplied

to the microphone by a mixer, preamplifier or console with built-

in phantom power or from an external power supply (such as

the Shure model PS1A). Phantom power sources providing be-

tween 11 and 52 Vdc are suitable.

Use only high-quality cables because intermittent shorts

between broken shield wires and balanced conductors will

cause extremely large noise transients in the system. Avoid

ground loops due to grounded connector shells or the micro-

phone case touching other grounded metal objects. Follow

generally accepted audio grounding practices.

Impedance

A minimum load impedance of 800 Ω or greater should be

used for maximum signal handling and minimum distortion. The

load may be as low as 150 Ω, but a reduction in output clipping

level will result. It should be noted that the power supply itself

may add loading (3300 Ω in the Shure PS1A power supply) to

the microphones.

PS1A Power Supply

When using the Shure PS1A to phantom power the SM81,

connect the microphone cable to the SM81 and to the MICRO-

PHONE connector of the power supply. The power supply uses

the balanced audio cable pair to carry the supply current to the

microphone and the cable shield as a ground return.

Connect the OUTPUT connector of the power supply to a

low-impedance microphone input of a mixer, audio console or

tape recorder. A second SM81 may be connected to the re-

maining power supply channel in a similar manner.

212 mm

20 mm

23.5 mm

OVERALL DIMENSIONS

FIGURE 3

Low-Frequency Response Filter

The SM81 has a three-position low-frequency response fil-

ter controlled by a switch located on its handle. The switch is

recessed to avoid accidental movement, but may be easily

moved with fingertips. The user may select either flat response,

low-frequency rolloff of 6 dB per octave below 100 Hz, or low-

frequency cutoﬀ of 18 dB per octave below 80 Hz (see

Figure 1). When close-miking instruments or vocalists, an

increase in low-frequency response (proximity eﬀect) takes

place. Figure 4 illustrates this eﬀect with the switch in each of

the three positions. Note that the low-frequency response filter

may be used to compensate for proximity effect or reduce low-

frequency noise from stage traffic and other sources.

20 100050 100

+10

–10

152.4 MM ( )

PROXIMITY EFFECT AND COMPENSATION

FIGURE 4

Attenuator Switch

The SM81 has a switchable 10 dB capacitive attenuator to

prevent high sound pressure levels from overloading its internal

electronics. The attenuator is engaged by rotating the actuator

ring, located directly below the grille assembly, until it reaches

the “– ”10 position. This reduces the output of the microphone

by 10 dB and increases the maximum sound pressure level at

clipping by 10 dB. There are no intermediate levels of attenua-

tion available.

The attenuator ring may be locked in either the “ ”0 or 10“– ”

position as follows. Unscrew the grille and cartridge assembly

by unscrewing counter-clockwise from the top. Turn the actua-

tor ring to the “ ”0 or 10 position as desired. Insert the actuator“– ”

ring lock (small clear piece of plastic) in the area behind the ac-

tuator ring between the pin and the edge of the slot. This will

prevent the ring from turning. Replace the grill and cartridge as-

sembly.

Mixer Overload

The SM81’s output is about 15 dB higher than most dynam-

ic microphones. At moderate to high SPLs, this additional out-

put may require attenuation (or padding). If no attenuation is

available on the preamplifier, mixer or console being used, a re-

sistive attenuator can be inserted between the microphone and

the input. The Shure Model A15AS Attenuator (15, 20, or 25 dB

switch-selectable) is specially designed for use with condenser

microphones such as the SM81. Alternately, the attenuator de-

sign shown in Figure 5 may be used. The resistors shown are

1/2-watt, 1% tolerance, and the circuit may be packaged in a

Switchcraft S3FM adapter housing. The circuit will provide15

dB of attenuation and can be used between the SM81 and the

PS1A (or other power supply), or between the PS1A and the

mixer. Two of these circuits may be used in series to provide 30

dB of attenuation. (Note that, due to excessive loading, com-

mercially available 150 Ω attenuators, such as the Shure Model

A15AS, are not recommended when two are used in series.)

OUTPUT TO

MIXER

INPUT FROM

MICROPHONE

12 3

412

215

15 DB ATTENUATOR CIRCUIT

FIGURE 5

Wind Noise

The wide frequency response of the SM81 makes it sensi-

tive to wind, breath, and air currents from heating, ventilation

and cooling (HVAC) systems. The foam windscreen included

with the SM81 can be used to reduce wind and breath noise,

while the low-frequency response filter can be used to reduce

low-frequency room noise caused by HVAC systems.

The Model A81G Pop Filter Grille attenuates breath pop-

ping sounds when the microphone is close-talked, and permits

its use outdoors with minimal pickup of rushing and rumbling

sounds. To install the A81G, slip it over the SM81 until the inside

of the A81G touches the top of the microphone. Tighten the

A81G by rotating the knurled collar clockwise from the bottom.

(Note: When removing the A81G, first loosen the knurled collar.

Otherwise the cartridge will unscrew with the A81G.)

For outdoor use under very windy conditions, use the Mod-

el A81WS large foam windscreen.

CAPACITOR

CARTRIDGE

FET

IMPEDANCE

CONVERTER

RESPONSE

FILTER

CLASS A

COMPOUND

AMPLIFIER

RFI

FILTER

BALANCED

TRANSFORMER

REGULATOR/

REVERSE

VOLTAGE

PROTECT

CAPACITIVE

ATTENUATOR

BLOCK DIAGRAM

FIGURE 6

Product specificaties

Merk:	Shure
Categorie:	Microfoon
Model:	SM81
Kleur van het product:	Metallic
Gewicht verpakking:	740 g
Soort:	Microfoon voor podiumpresentaties
Aansluiting:	XLR-3
Stroomverbruik:	1.2 mA
Signaal/ruis-verhouding:	78 dB
Microphone direction type:	Unidirectioneel
Gevoeligheid microfoon:	-45 dB
Frequentie microfoon:	20 - 20000 Hz
Microphone input impedance:	150 Ohm
Gewicht microfoon:	230 g
Afmetingen microfoon (DxH):	23.5 x 212 mm