Shure

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THE SHURE

TECHNICAL BULLETIN DEVOTED

TO

THE

ADVANCEMENT

VOL 2 Nos 1 6 2 1st ANNIVERSARY

Part

OF

MICROPHONE

TECHNIQUE

JUNE-JULY 1934 ISSUE

4

FIELD PROBLEMS IN MICROPHONE PLACEMENT

This is the first anniversary issue of the Shure TECHNICAL BULLETIN. I n it, we present another installment of the series of articles dealing with microphone placement problems. Previous issues have covered various electric and acoustic phases of the subject. The present article deals in the main with the mechanical problems of microphone mounting encountered by broadcast and sound technicians. Special fittings and new microphone accessories which are very useful in various types of sound work are shown in the illustrations. Fig. I. A special condenser microphone for "piano-vocal" pickups. It consists of a Shure Model 40 Condenser Head swivel-mounted at one end of the boom. The head is connected to the 40C amplifier on the other end of the boom through low-capacity shielded cable. The boom is mounted on a M o d d 531 Automatic Friction Lock Floor Stand. (Shure Brothers Co. photo, Courtesy Paul Ash Enterprises. Chicago.)

Every user of microphones is familiar nith the conventional means of mounting these instrumentson floor, banquet or desk type stands, but very often these orthodox accessories are not suited to the problem at hand. The mounting device must not only perform its obvious task of supporting the microphone, but should be unobtrusive, easy to adjust and above all, convenient for the artist. Considerable attention is given these points in broadcast work, but there is room for considerabie improvement in ~nicrophoneset-up technique in public address practice. Oftentimes special equipment is necessary to attain the above enumerated objectives, for instance, in the rase of piano-vocal pickup work. Fig. 1 shows one very satisfactory solution of this 01934

problem in which a condenser microphone was mounted on a special boom attached to an automatic friction-lock floor stand.

cable running through the horizontal tubing. The head was swivgled to per,it angular adjustment the horizontal tubing or boom was built to the

Ordinary overhead suspension was proper length and attached to the verdiscarded in this particular installation tical plunger of the floor stand. In this due to the difficulty of adjusting the way, a portable mounting was provided microphone to the exact position de- which could be quickly set UP and adsired in the horizontal plane. Neither justed to exactly the Proper height and could a conventional bullet or studio- position for any particular artist. type condenser microphone assembly be Adjustable booms of a different type, used because of the requirement that some of them with very elaborate mechthe artist's view of music rack and key- anisms, cable reels and other features board be free and unobstructed. have been standard equipment in the moving picture industry since the incepA condenser head was therefore tiorl of sound recording. H~~~ it is mounted on one end of a length of metal tubing with the amplifier case on the other end. Head and amplifier were connected by a low-capacity shielded

Shurc Brothers Company, Chicago. All rights mcrved.

necessary to sling the microphone above the cast and well outside the field of the camera, and at the same time provide a rapid adjustment so that moving ac-

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THE SHURE TECHNICAL BULLETIN

tion can he followed closely. At the present time there appear to be few uses for siich equipment outside the moving picture industry. MOUNTING THE CONDENSER MICROPHONE Although the condenser microphone is usually to be seen mounted on a floor stand, Figs. 2, 3 and 4 show a variety of mountings for condenser and similar microphones. In Fig. 2, the microphone is mounted on a desk stand. This low mounting is very convenient for announcer's use when the instrument is placed on a table or desk for either studio or remote service. The desk stand is likewise ideal for the principal's desk in a school public address installation and for many similar purposes.

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Fig. 2 (Right). Condenser microphone mounted on an Adjustable Desk Stand. Especially convenient for studio routine .announcements, remote pickups, and spotnews field work. Fig. 3 (Below). Two microphones may be mounted on a regular floor stand with the aid of a Dvplex Fixture. A highly desirable arrangement for dual channel pickups (broadcast and house P.A. system, etc.) Fig. 4 (Lower left). The Duplex Fixture applied to a Banquet Stand-another example of the convenience of specialized microphone accessories.

(as illustrated for the condenser units) or with the aid of special adapters. Duplex fixtures and coupling adapters are now available conimercially. SUSPENSION MOUNTING

The problem of arranging two microphones close together for dual channel pickup of the same program is solved with the aid of an ordinary stand and a duplex fixture as shown in Figs. 3 and 4. One microphone is often used for broadcast purposes while the other supplies input to a house public address system. It is essential that the two microphones be placed close together for such work so that a singer or speaker may stand close to both units to provide proper pickup for both channels.

Sometimes it is not possible to support the microphone on a stand in the usual manner. A typical example is the case of an orchestra playing on a small, crowded platform where the floor space required for a regular floor stand would interfere seriously with the action and movements of the orchestra leader and singers. Here sus,pension mounting provides a solution. Fig. 5 shows a standard microphone ring fitted with a suspension adapter for overhead support. The adapter is suspended from the ceiling by means of two sash cords or the equivalent, the double cord eliminating the tendency for the microphone to twist appreciably.

The choice of the stand for duplex service depends, of course, on the particular pickup conditions. A floor stand

is best for orchestra work indoors and addresses and speeches whenever the microphone cannot be placed on a rostrum or table. For banquets and similar functions, the regular banquet stand placed on the table is the ideal arrangement. Similar types of mountings may be employed for other types of microphones. Rings are required of course when two-button microphones are to be mounted. Still other types of microphones can be attached either direct

SHURE BROTHERS COMPANY

If desired, the supporting cords may be run through pulleys and counterweights attached to the ends to allow adjustment of the height of the microphone. The microphone can be pushed up out of the way when not in use by the singer, while still providing good pickup of the orchestra music.

It is also possible to suspend the microphone ring from the microphone cable itself, although usually this method is not to be recommended for both mechanical and electrical reasons. In addition the ring tends to twist and is inconvenient to use. However, if cord suspension of the microphone ring is employed, the technician should make certain that all strain is removed from

THE SHURE TECHNICAL BULLETIN the cable terminals themselves at both the microphone and apparatus terminals. This can he accomplished by making a knot in the cable below the hole in the ring, or by building up the diameter of the cable with varnished twine or friction tape. There should be ample slack in the microphone leads between nlicrophone terminals and the point of strain relief. A regular suspension adapter makes a much better installation, and there is a minimum tendency to twist out of position.

Suspension mounting is especially cot!venient wherever the available floor or desk space is limited. Jt is very well suited to the crowded operating room of the amateur radiophone transmitter, freeing valuable table space for controls and switches which require manual operation. The radio amateur seems to have overlooked this highly practical opportunity to relieve operating table congestion.

Condenser and similar types of microphones are often suspended from above, but the relatively heavy weight of the head and amplifier assembly makes the use of separate suspension cordage imperative to eliminate the danger of open circuits in the connecting cable. A bullet type condenser microphone suspended in this manner is shown in the illustration on page 4. The same suspension adapter illustrated in Fig. 5 is also used with the condenser microphone and is merely screwed into the threaded hole normally provided for stand mounting. Pulleys and counterweights are of course applicable as mentioned above. The bullet type condenser microphone is most convenient for overhead suspension since the swivel mounting of the head allows the microphone diaphragm to be faced directly toward the source of sound regardless of the height. Studio and camera type microphones are, however, sometimes mounted in this manner.

A brand new microphone accessory

Fig. 6. A New Microphone AcVal-A ontrol or O n - O f f Switch which may be m o u n t e d on Floor Banquet or 0;rk Stands: Ideal where control must be delegated tothc s~eaker.

":?%

3

STAND VOLUME CONTROL OR SWITCH which is extremely valuable for installations in which there is no control operator on-duty to monitor volume, is the stand volunle control or switch illustrated in Fig. 6. The i in all cast housing is designed to be threaded onto the stand and accommodates a ~nicrophonering or threaded case. A speaker can adjust the volume level to suit without leaving the microphone. The unit is also furnished with an ON-OFF switch in place of the volume control. The switch is used to break either the center conductor (batt e r ~circuit) of a two-button microphone or one side of the circuit in the case of a single-button unit. Thus it is possible for the speaker to throw the microphone in or out of circuit at will without leaving his place, a feature that is often very useful. The volume control consists of a miniature rheostat properly tapered, which is silnply shunted across the microphone eirwif. In the ease of a *webutton microphone, the variable res'istance is connected across the buttons. If the buttons are reasonably well balanced in resistance, this shunt resistance will not disturb either the individual button currents or the total current supplied from the batteries. It is also possible, of course, to connect the rheostat in series with the center conductor in the case of two-button microphones, although the former method has been found to give a wider range of volume adjustment. Volunie controls or switches of these types may be built into hand microphones and are available commercially in this form,

215

Flg. 5. The Suspens~on Ring, a microphone mounting often used for vocal selections in dance orchestra work. Pulleys and counterweights permit quick adjustments when space for regular Floor Stand mounting is not available.

SPECIAL MICROPHONE STANDS A number of special microphone stands for portable service have been developed and serve to illustrate the utility of specialized accessories. An ingenious combination of a standard microphone ring and a suitable handle results in an ideal mounting for two-button microphones which must be carried about by the announcer when covering spot news broadcasts and sports events. The ordinary desk stand is cumbersome and difficult to carry, both of which objections have been overcome in the spedal hand mounting described here. A portable floor stand, which may be folded into the small length of 30 inches (ring removed) for transportation and packing, and yet is extensible to a height of 105 inches. is a valuable ac" cessory for portable public address and broadcast remote control pickup equipment. AUTOMATIC FRICTION LOCK FLOOR STANDS The older type of floor stand, with its wing-nuts, set-screws or clamps is now practically obsolete. The "Automatic Friction Lock" floor stand developed by Shure Brothers Company dispenses with all of these cumbersome and unreliable clamping mechanisms. The ~ l u n g e ris sr~pportedthrough friction exerted by spring-supported leather washers, holding the microphone firmly in position, yet allowing easy adjustment of the height or position of the unit. The action is smooth and reliable,-so reliable

W.Huron St., Chicago, U. S. A.

4

THE SHURE TECHNICAL BULLETIN

that it is guaranteed indefinitely by thc manufacturers. A chrornium plated knurled collar at the top of the barrel may be turned for initial adjustment of friction to suit the weight of the microphone. No further adjustn~entsof any iort are necessary thereafter. Perhaps n l the sound n ~ a nw110 equally i ~ i l p o r ~ a to appreciates finished equipment is the fact that the close-fitting parts of the "Automatic Friction Lock" cannot rattle and all adjustments are entirely silent. The stands are finished in baked rubber black japan with chromium plated ring and collar. They will accommodate microphones of all makes and types, special coupling adapters being available from the manufahurer.

THE SHURE TECHNICAL BULLETIN Since this is the anniversary issue of the Shure TECHNICAL BULLETIN, it is only natural that some space in the BULLETIN be devoted to a mention of this fact, together with a brief restatement of the purpose and policies of this pu hlication.

,dgmeI1t is made material.

Altbough the articles in the BULLETIN are staff-written, the comments and contributions of its readers are welconled. Although there is 110 payment for reader contributions, full acknowl-

SHURE BROTHERS COMPANY

the source of all

Thc Shure TECHNICAL. BULLETIIV is pi~hlishedmonthly. It is rllailed with~ u charge t to cr~ston~ers of Shure Brotht a r s Coli~pauy, distri1)utors of sound equipment, officials of lwoadcast stations and other microphorle users. Those not entitled to receive the BULLETIN under one of the above classifications, may subscrihe at the yearly rate of 50 cents, A limited number of back issues are available at 6 cents each. Subscription charges are entirely nominal and only partially defray the costs of handling and mailing. Yurnbers and titles of the first twelve issues of the BULLETIN are listed belo%,. No. I-Condenser crophones.

vs. Two-Button Mi-

No. 2-Field Problelns in 'Microphone Placement; Part 1-Broadcasting. h o . 3-Field Problems in Microphone Placement; Part 2-Public Address Systems.

No. &Mixing The BULLETIN is the official pu1,lieation of Shure Brothers Cornpan,. "Microphone Headquarters," 215 West Huron Street, Chicago, U.S.A. Although a n~anufacturer's "house organ," the editorial policy of the BULLETIN IS ' essentially independent and the editorial (*ontents embrac.es a much wider scope than the particular products manufactured by its publishers. The avowed purpose of the BULLETIN is "the advancement of microphone technique," a purpose which broadens its scope to ind u d e practical acoustics, theoretical and practical data on microphone construetion, operation and applications, sound ~neasi~rements and standardization, the theory, design and operation of amplifyirlg equipment and broadcast, public address and sound recording problems in general.

of

Circuit Design Data.

No. 5-The Microphone-An Electric Ear; Noise Measurements; Einaural Transmission. Problems in MicroNo. &Field phone Placement; Part 3-Multiple Microphone Systems. No. 7-Electro-Acoustic (arophone Performance.

Tests of Mi.

QUARTERS-but, it has a long record of service behind it. The head used on the new 40D has been in continuous production since early in 1933. In fact the performance of the 40D is identical with that of our well-known 4 0 C Studio Type Condenser Microphone now in use in many broadcast stations. The swivel head of the 40D can be aimed directly at the source of sound for best pickup and quality of reproduction whether the microphone is placed on a tabre, surpended from the ceiling, or mounted on any Shure Microphone stand in the usual manner. The instrument is essentially a high-quality.. aii damped stretched-diaphragm condenser head and a two-stage head amplifier using type '30 tubes. An excellent frequency characteristic is secured through proper diaphragm stretching and special back-plate construction for equalization of damping. Full barometric compensation. The 40D Condenser Microphone is s u p p l i ~ d complete with two specially tested, non-microphonic type '30 tubes. Price twelve ,feet of shielded rubber-covered cable, a special suspension adapter and complete instruc- (Including tions.

List

$60

Sound ReproNo. P-High-Quality duction-An Outline of Factors Affecting Fidelity. No. 9-The Truth About Microphone Response Curves No. 10-Transformers put Circuits.

for Speech-In-

No. 1]-Amateur mitters; Part 1.

Radiophone Trans.

No. 12-Amateur mitterr; Part 2.

Radiophone Trans-

The Present su1)scription list includes readers in every State of the Union and in many foreign countries. Many of

215

these readers have been kind enough to write of their interest in the ~ublication. The Editor hereby acknowledges witjl heartfek thanks, all suek cordial expressions.-Editor.

W. Huron St., Chicago. U. S. A.