Shure 730S User Guide

DATA SHEET No. 138

DATE: January, 1942

SUBJECT:

MODEL 730S "UNIPLEX" CARDIOID CRYSTAL MICROPHONE

GENERAL :

tion or speech. The true uni-directional "cardioid" characteristic of the "Uniplex" allows highly satis-

factory operation under adverse conditions of background noise and reverberation where a conventional microphone would be practically useless. (See "A

tic Considerations" for a discussion of directional

characteristics).

The "Uniplex" contains a diaphragm-type element combined with acoustical networks which cause cancellation or sound pressures for sounds incident from the rear. The crystal is a Grafoi1 (high capacity) bimorph

unit, triple moisture-sealed to withstand adverse climatic conditions. The microphone has a built-in filter circuit for protection against R.F. burnouts. Case

is pivoted at the rear and may be conveniently pointed in the direction of the desired sound, or pointed up-

wards for non-directional horizontal plane pickup.

The microphone is provided with an S36A Desk

Stand detachable three-way plug and 7-foot single conductor cable. The same Microphone without a stand is available under the Model No. 730SH.

APPLICATIONS:

and other applications where clear, intelligible reproduction or speech is or prime importance. The Microphone has a high output permitting its use with moderate gain amplifiers. The wide-range unidirectional characteristic of the "Uniplex" provides an easy solution to the feedback problem in reverberant locations, permits best utilization of space in small rooms, and allows a practically complete exclusion or unwanted noises.

By pivoting the microphone upwards a 360° non-directional horizontal plane characteristic is obtained which is useful for group or round-table pickup (See "Acoustic Considerations" for information on non-directional placement).

INSTALLATION:

stand. For overhead suspension, an A35B Suspension Adapter may be used. Convenient cable changing is possible due to the built-in receptacle. A 7-foot single-conductor cable is furnished with plug attached.

(See catalog for bulk length and special cables

plug attached).

COhWECTIONS

fler

across a load resistance of though an lnput

shpuld

be used to decrease the low frequency response

of the Mlcrophone for improvement In speech

mfsslon efflclency,

good low frequency response 1s deslred. The shleld or

ground should be connected to the

The

ClOC

cable.

crophone

nectlng cable wlilbe put level as given In the table below. There 1s no frequency dlscrlmlnatlon introduced by the cable, regardless of length.

Copyrlght Shure Brothers, 1942

plugs are available. Added lengths of

Total Cable Length

7 Ft. (Standard) 25 Ft. 50 Ft. 75 Ft.

100 Ft.

(Expressed in db below 1 volt per bar.)

Model 730S is a uni-directional diaphragm-type crystal microphone designed especially for high quality reproduc-

COUS

Model 730S is designed especially for voice transmission and is suitable for public address, amateur broadcasting.

Model 730S is equipped with the standard 5/8"-27 thread and may be mounted on any Shure desk., banquet, or, floor

with

The lnner conductor or “hot” lead of

the cable should be connected to the grld of the

resistance of

hlgher values are

microphone 1s

Longer cable lengths provlded wlth ml-

accompanied

rlrst

tube In the

to 5 megohms. Al-

approximately 4

recownended 1P

chassis,

supplled with a 7-foot length

by a decrease in out-

Output Level* at Cable

Terminals

53.0 db

55.5 db

58.0 db

60.0 db

60.5 db

ampllmegohm trans-

See

Fig.

con-

clent margln of galn to make up for the decrease

output levels shown ln the

does not have the necessary

microphone Preampllflers with

ded 1I the maln

transrormer

II cables are to be joined, the lnner leads should be soldered and lnsulated with a good grade of rubber tape. should be soldered between the shields of the cable to complete the shielding. Longer lengths of cables

with

cost, cables.

OPERATION:

accldently connected to loud speaker or power supply outlets carrying hlgh voltage. Check your connections carefully.

guarantee is volded by tampering with the mechanism.

places where the temperature exceeds should not be exposed to the rays of the sun in very hot weather for any left in closed automoblles parked In the sun hot weather, as the temperature inside the

may easily bulld up to over damage the crystal.

mum length of cable consistent wlth

qulrensnts

cable shleld 1s advlsable.

(over)

Model 730S "Uniplex" Cardioid Crystal Microphone

Most modern hlgh-gain

or near the main ampllfler

Cable should be of hlgh quality

Metal brald sleeve or a serve of fine wire

standard plug attached may be purchased at small

and

may be used interchangeably with shorter

(See Catalog3

Crystal microphones may be seriously damaged

The microphone case should not be opened. Our

Crystalmlcrophones

When

used near a radlo transmitter, the

should be used. Careful grounding of the

low impedance output are

ampllfler

mixer

input.

No polarlzlng voltage 1s required for

crystal

considerable

ampllflers

table.

galn,‘a preampllller

system has low impedance

microphones.

should not be used or kept

have a

the

andlow

length of time - or

125O

and permanently

placement’re-

Printed in

surfl-

ampllrler

at the

suggested.

reconunen-

capacity.

1250

F. They

during

automobl;le

U.S.A.

mlnl-

NO.

138

DATA SHEET

No special precautions beyond ordinary care are necessary in the operation of the "Uniplex" microphones. They will operate efficiently and dependably under all ordinary conditions.

ACOUSTIC

CONSIDERATIONS:

The high-frequency response of

the 730S is accentuated and

the low frequencies are attenuated to give a smoothly rising response characteristic. (See Fig. C). The result of this is a microphone in which a high degree of speech intelligibility is achieved without undue loss of quality. The expression "cardioid type" response simply means that the horizontal polar characteristic approximates a cardioid of

ing the dead side (rear) of the microphone towards the audience or other source of interfering sound, pickup can be concentrated on the

desired source. Reverberation energy pickup is decreased approximately two-thirds. The microphone can be placed close to reflecting surfaces without objectionable effects if the rear side of the microphone is toward the reflecting surface. This is particularly valuable in small halls.

It is desirable to experiment with microphone placement and orientation in order to secure the greatest benefits from the unidirectional characteristic.

revolution. There is a wide, useful pickup angle at the front of the microphone while the response at the sides is down 6 db and the rear response is down of the order of 15 db from the front side response over a broad range of frequencies. The true unidirectional characteristic of the "Uniplex" should not be confused

Voltage Sensitivity: 2.25 millivolts r.m.s. per bar at

with the relatively slight directional effect at high frequencies only which can be produced by baffle-effects in the conventional pressure

microphone.

The result of this unidirectional characteristic is a complete elimination of acoustic feedback at volume levels which would cause

This is equivalent to 53 db below 1 volt per bar.

Internal Output

Recommended Load

Impedance :

Impedance:

considerable feedback with conventional semidirectional microphones. In practically all

cases it is possible to increase loud-speaker

levels when a Uniplex is installed. By direct-

SPECIFICATIONS

the end of a 7-foot cable across 1 to 5 megohms at 400 cycles.

Equivalent to a 1500 micro-microfared condenser.

1 to 5 megohms.

Height, Overall (a)*. . . .

Height, Case (h)* . . . . . 3-1/8

Width (b)*. . . . . . . . . 3-1/8

Thickness (c)*. . . . . . .

Finish. . . . . . . . . . . Satin Chrome

Net Weight. . . . . . . . . 2-1/4 lbs.

Shipping Weight . . . . . . 2-1/2 lbs.

Code Word . . . . . . . . .

* See Fig. B.

GUARANTEE:

period of one year from date of shipment from

the factory, provided all instructions are complied with fully. In case of damage, re-

turn the microphone to the factory for re-

pairs. Our guarantee is voided if the microphone case is opened.

LICENSE NOTICE:

FIG. C TYPICAL FREQUENCY RESPONSE. SHURE MODEL 730S "UNIPLEX" MICROPHONE

Each microphone is guaranteed to be free from electrical and mechanical defects for a

Shure patent 2,198,424. Other patents allowed. Licensed under patents of the Brush Development Company.

4-3/8

3-3/8

RUPOD