THE SHURE

TECHNICAL BULLETIN D E V O T E D T O T H E A D V A N C E M E N T O F M I C R O P H O N E T E C H N I Q U E

VOL 2 Nos 1 6 2 JUNE-JULY 1934

1st ANNIVERSARY ISSUE

Part 4

FIELD PROBLEMS IN MICROPHONE PLACEMENT

This is the first anniversary issue of the Shure TECHNI- CAL BULLETIN. In 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 mechan- ical 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 illus- trations.

Every user of microphones is familiar nith the conventional means of mount- ing 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 obvi- ous task of supporting the microphone, but should be unobtrusive, easy to ad- just and above all, convenient for the artist. Considerable attention is given these points in broadcast work, but there is room for considerabie improvement in ~nicrophone set-up technique in pub- lic address practice.

Oftentimes special equipment is nec- essary 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

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 Modd 531 Automatic Friction Lock Floor Stand. (Shure Brothers Co. photo, Courtesy Paul Ash Enterprises. Chicago.)

problem in which a condenser micro- cable running through the horizontal phone was mounted on a special boom tubing. The head was swivgled to per- attached to an automatic friction-lock ,it angular adjustment the hori- floor stand. zontal tubing or boom was built to the

Ordinary overhead suspension was proper length and attached to the ver- discarded 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 ad-

sired 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 mech- the 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 incep- A condenser head was therefore tiorl of sound recording. H~~~ it is

mounted on one end of a length of necessary to sling the microphone above metal tubing with the amplifier case on the cast and well outside the field of the the other end. Head and amplifier were camera, and at the same time provide connected by a low-capacity shielded a rapid adjustment so that moving ac-

01934 Shurc Brothers Company, Chicago. All rights mcrved.

2 THE SHURE TECHNICAL BULLETIN t

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 an- nouncer'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.

The problem of arranging two micro- phones 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 broad- cast purposes while the other supplies input to a house public address sys- tem. It is essential that the two micro- phones 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.

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

Fig. 2 (Right). Condenser micro- phone mounted on an Adjustable Desk Stand. Especially conven- ient for studio routine .announce- ments, remote pickups, and spot- news field work.

Fig. 3 (Below). Two microphones may be mounted on a regular floor stand with the aid of a Dvplex Fixture. A highly desir- able arrangement for dual chan- nel 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 mi- crophone accessories.

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

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 micro- phones. Rings are required of course when two-button microphones are to be mounted. Still other types of micro- phones can be attached either direct

SUSPENSION MOUNTING

Sometimes it is not possible to sup- port 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 pro- vides a solution.

Fig. 5 shows a standard microphone ring fitted with a suspension adapter for overhead support. The adapter is sus- pended from the ceiling by means of two sash cords or the equivalent, the double cord eliminating the tendency for the microphone to twist appre- ciably.

If desired, the supporting cords may be run through pulleys and counter- weights attached to the ends to allow adjustment of the height of the micro- phone. 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

SHURE BROTHERS COMPANY

THE SHURE TECHNICAL BULLETIN 3

the cable terminals themselves at both the microphone and apparatus termi- nals. 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 suspen- sion adapter makes a much better in- stallation, and there is a minimum ten- dency to twist out of position.

Condenser and similar types of micro- phones are often suspended from above, but the relatively heavy weight of the head and amplifier assembly makes the use of separate suspension cordage im- perative to eliminate the danger of open circuits in the connecting cable. A bul- let type condenser microphone sus- pended in this manner is shown in the illustration on page 4. The same sus- pension adapter illustrated in Fig. 5 is also used with the condenser micro- phone and is merely screwed into the threaded hole normally provided for stand mounting. Pulleys and counter- weights are of course applicable as men- tioned above. The bullet type condenser microphone is most convenient for over- head suspension since the swivel mount- ing of the head allows the microphone diaphragm to be faced directly toward the source of sound regardless of the height. Studio and camera type micro- phones are, however, sometimes mounted in this manner.

Fig. 6. A New Microphone Ac-

-A Val- :":?% ontrol or On-Of f Switch which may be m o u n t e d o n Floor Banquet or 0;rk Stands: Ideal where con- trol must be delegated tothc s~eaker.

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 op- eration. The radio amateur seems to have overlooked this highly practical opportunity to relieve operating table congestion.

STAND VOLUME CONTROL OR SWITCH

A brand new microphone accessory which is extremely valuable for installa- tions in which there is no control op- erator on-duty to monitor volume, is the stand volunle control or switch illus- trated in Fig. 6.

The i in all cast housing is designed to be threaded onto the stand and accom- modates a ~nicrophone ring or threaded case. A speaker can adjust the volume level to suit without leaving the micro- phone. The unit is also furnished with an ON-OFF switch in place of the vol- ume control. The switch is used to break either the center conductor (bat- t 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 leav- ing his place, a feature that is often very useful.

The volume control consists of a min- iature rheostat properly tapered, which

Flg. 5. The Suspens~on Ring, a microphone mounting often used for vocal selections in dance orchestra work. Pulleys and counterweights permit quick adjust- ments 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 stand- ard 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- "

is silnply shunted across the micro- cessory for portable public address and phone eirwif. In the ease of a *we- broadcast remote control pickup equip- button microphone, the variable res'ist- ment. ance is connected across the buttons. If the buttons are reasonably well balanced AUTOMATIC FRICTION LOCK

in resistance, this shunt resistance will FLOOR STANDS

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, al- though 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 micro- phones and are available commercially in this form,

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 r is sr~pported through friction exerted by spring-supported leather washers, hold- ing the microphone firmly in position, yet allowing easy adjustment of the height or position of the unit. The ac- tion is smooth and reliable,-so reliable

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

4 THE SHURE TECHNICAL BULLETIN

that it is guaranteed indefinitely by thc ,dgmeI1t is made of the source of all manufacturers. A chrornium plated material. knurled collar at the top of the barrel may be turned for initial adjustment of friction to suit the weight of the micro- phone. No further adjustn~ents of any iort are necessary thereafter. Perhaps equally i~ i lpor~anl to the sound n ~ a n w110 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 avail- able from the manufahurer.

Thc Shure TECHNICAL. BULLETIIV is pi~hlished monthly. It is rllailed with- ~ u t charge to cr~ston~ers of Shure Broth- t 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 be- lo%,.

THE SHURE TECHNICAL No. I-Condenser vs. Two-Button Mi- BULLETIN crophones.

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 restate- ment of the purpose and policies of this pu hlication.

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 ' es- sentially independent and the editorial

No. 2-Field Problelns in 'Micro- phone Placement; Part 1-Broadcast- ing.

h o . 3-Field Problems in Micro- phone Placement; Part 2-Public Ad- dress Systems.

No. &Mixing Circuit Design Data.

No. 5-The Microphone-An Electric Ear; Noise Measurements; Einaural Transmission.

No. &Field Problems in Micro- phone Placement; Part 3-Multiple Microphone Systems.

(*ontents embrac.es a much wider scope No. 7-Electro-Acoustic Tests of Mi.

than the particular products manufac- (arophone Performance.

tured by its publishers. The avowed purpose of the BULLETIN is "the ad- No. P-High-Quality Sound Repro- vancement of microphone technique," a duction-An Outline of Factors Affect- purpose which broadens its scope to in- ing Fidelity. dude practical acoustics, theoretical and

No. 9-The Truth About Microphone practical data on microphone construe-

Response Curves tion, operation and applications, sound ~neasi~rements and standardization, the No. 1 0-Transformers for Speech-In- theory, design and operation of ampli- put Circuits. fyirlg equipment and broadcast, public address and sound recording problems No. 1 ]-Amateur Radiophone Trans.

in general. mitters; Part 1.

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 perform- ance of the 40D i s identical with that of our well-known 40C 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, sur- pended 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 dia- phragm stretching and special back-plate construction for equalization of damping. Full barometric compensation.

The 40D Condenser Microphone is suppl i~d complete with two spe- cially tested, non-micro- List phonic type '30 tubes. Price twelve ,feet of shielded rubber-covered cable, a special suspension adap- $60 ter and complete instruc- (Including tions.

No. 12-Amateur Radiophone Trans- Altbough the articles in the BULLE-

mitterr; Part 2. these readers have been kind enough to TIN are staff-written, the comments and write of their interest in the ~ublication. contributions of its readers are wel- The Present su1)scription list includes The Editor hereby acknowledges witjl conled. Although there is 110 payment readers in every State of the Union and heartfek thanks, all suek cordial ex- for reader contributions, full acknowl- in many foreign countries. Many of pressions.-Editor.

SHURE BROTHERS COMPANY 215 W. Huron St., Chicago. U. S. A.