US 2235518 A
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Description (OCR text may contain errors)
March 18, 1941.
l. n sosHAw 2,235,518
' IIG'ROPHQNE CDNTROL SYSTEIl Filld Aug. 27, 1938 `2 .Sheets-Sheet 2 [EL IQ. Gow/Aw,
E MW@ 'A Patented Mar. ,18, 1941 PATENT oFFicE i 2,235,518 MlonornoNE coN'rnoL SYSTEM Irl B. Goshaw, Beverly Hills, Calif., assigner to Radio Corporation oi' America, a corporation of Delaware Application August 27, 1938K, Serial No. 227,054
pictures, sound is picked up by amicrophone. and r it has been the general practice to suspend the microphone on the end of the telescoping cross arm of a boom, the microphone being raised, lowered and moved horizontally by movement of the cross arm. So as not to unnecessarily move the microphone during recording. the boom isv generally placed so as to position the microphone at some iixed position where all the sounds may reach it with comparable energy and a similar frequency response if the microphone isA always directed at the particular source of sound, re-
gardless of its position on the set. To change the microphones direction, it must be rotated so as to follow the movement of a sound source about the set or to shift from one source to another in different parts of the set.
Several methods of and means for accomplishing the rotation ot a microphone at the end oi a boom have been suggested and pati ented. The useof amotor for accomplishing this result is disclosed in U. S. Patent 1,924,679,
this practice, however. having the fault of creating electrical disturbances caused by the operation oi the motor, which are picked up by the immediately adjacent microphone. An advance over the motor control 'is shown in U. S.
Patent 2,122,778. This improvement employs a purely mechanical system which, although eliminatingV electrical motor disturbances, does create wind reaction and complicates the mechanism' of v the boom structure, as itis necessary to provide u means for extending and withdrawing the operating cables, as shown in the patent. otherv mechanical systems have-'been emplyed. such as square shafts and bevel gears which may be rotated by .the boom operator to rotate the micro- I phone.
The prent invention eliminates-the motor and all mechanical devices and permits the 'microphone toremain absolutely nxed while eitective rotation thereof is obtained.v The operto ator need only `rotate a knob on a dial similar to a radio receiver to 4follow the sound source about the set without actually moving the microphone in any respect. The boom structure is."
simplified since only 'the usual electrical'cable electrical circuit used is based upon the disclosure in U; S. Patent to L. J. Anderson, No. 2,173,219,0f Sept. 19, 1939, and the microphone is of the ktype shown in -U. S.,Reissue Patent 19,115 of March 13, 1934. v 5
An object of the invention, therefore, is to simplify a microphone boom construction while providing means for accomplishing all the necessary movements oi the microphone'.
Another object of the invention is to obtain 1@ eiective rotation ofa microphone mounted on the end of a boom without any physical movement of the microphone.
Another object of the invention is to reduce interference with the pick-up sensitivity of a microphone.
Although the novel features which are believed to be characteristic of this invention will be pointed out with particularity in the claims appending herewith, the invention itself, its 'objects 20 and advantages, the manner oi its organization and the mode oi' its operation will be better understood byreierring to the following description read in commotion with the accompanying drawings forming a part thereof, in which: 25
Figure 1 is a side elevation oi a movable microphone'v boom embodying the invention;
Figure 2 is a circuit diagram employed in Fig. 1,' and v Figures 3, 4 and 5 are characteristic curves oi 30 the -microphone used in the invention.
Referring now to Fig. 1, a truck having wheels, 5 and 8. crosspieces 1, and braces t and 9 has mounted thereon, a column member l I. Pivoted and rotatable on the column Iiis cross arm l2 85 having a'telescoping endpiece i3 at the end of which is' mounted a microphone cradle support I5 resiliently supporting, by rubber bands or springs I6, il, I8 and i9, a microphone pre-arnpliiler 2l and microphone 22. The cradle. micro- .40 phone and amplier are not rotatable in any manner with respect to the end oi the arm I3.
To the left ofthe column il, the arm i2 has mounted thereona traveling counterweight 24 hung on a roller block 2i. The arm I8 is extendso ed and withdrawn within the arm i2, and the weight 2t moved correspondingly to balance the z arm I3,;by actuating a bell crank 2l .operating on a wheel 2T rotatable 'about the pivot, point 19. Two cables shown by the dotted lines are also employed for this purpose. One end of one of the cables is'attached to the inner end of arm I3 at Il, from which the cable extends around a Dulley'i at the left-hand end of the arm I2. A around a pulley -32 on the block i5. a pulley 88 65 `together and to ground at 81.
.rotation of the pulley 21 in one direction will extend the arm I3, and rotation of the pulley 21 in the other direction will Withdraw the arm I3, the weight 24 traveling along the left-hand end oi the arm I2 to counterbalance the weight of the microphone and associated elements as their distance varies from the column II.
'I'he pick-up leads from the microphone are contained in a cable 42, which is attached to the cause any slack in the cable 42, since the travel-y ing block 25 takes up the slack automatically. For positioning the microphone,-therefore, the truck is ilrst placed, then the pulley 21 rotated to extend the microphone, after which the arm I2 may be rotated on the column iI to further position it. Thereafter, the microphone may re` main absolutely xed with respect to a certain scene, the action being followed solely by the turning of a knob 54 at the dial 50. Although an amplifier 2| has been shown positioned adjacent the microphone 32, this is not a` necessity and this amplifier may be positioned on the column I or included in the amplier at 5i.
-Referring now to the circuit employed to produce the rotational results above-described, refer.. ence is made to Fig, 2 wherein the microphone 22 is shown as comprising a pair of slightly crimped conductive ribbons 60 and 5I mounted at right angles to one another between respective magnets 52, B3 and B4. The microphone ribbon 68 is connected through transformers 66 and 61 with the input of a vacuum tube 68 having a biasing resistance 69 and bypass condenser 10 in its cathode circuit. The output of ribbon 6I is similarly connected through transformers 'lil .and 1I to the input of a vacuum tube 12 having biasing resistance 13 and the bypass condenser 14 in its cathode circuit. It will be noted that the input totube 12 is connected in phase opposition to the input to tube 68. l
The outputs'of tubes 68 and 12 are capacityresistance coupled by condensers B8' and 12' and resistances 68 and 13' to respective tubes 16 and 11 through respective potentiometer resistances 18 and 19, these last resistances being arranged in circular formation so that sliders 80 and 8|, respectively, may be operated simultaneously through a connection 83. The other terminals of resistances 18 and 18 are connected 83 has a pointer 84 mounted thereon for cooperation with a dial 85. Thus, by the turning of the knob 54 (see Fig. 1), sliders 80 and 8l are moved over their respective resistances in such a, manner that when one resistance is entirely out, the other resistance is entirely in, and vice versa, thus making either ribbon 60 or 5I effective. Intermediate positions utilize both ribbons The connection simultaneously and produce intermediate patterns, as'will be described.
The output of the potentiometer. 50 is impressed on tubes 16 and 11, mentioned above. amplied therein and transmitted through transformer 89 for transmission to a recorder or other load circuit.
Referring now to Figs. 3, 4 and 5, when the pointer 84 isto its extreme left position, the
microphone characteristic will be in accordance -with Fig. 3 and will, therefore, be directional to a sound source positioned inthe neighborhood of 45 with respect to the front position of the microphone. With the dial pointer 84 in the extreme'right position, the microphone characteristie will be in accordance with Fig. 4, or at an angle of 90 with respect to the characteristic of Fig. 3, since the ribbons 60 and 6I are at right angles. With the pointer 84 in its central position, the characteristic of the microphone 22 is shown in Fig. 5. Intermediate positions of the pointer will provide the microphone with intermediate characteristics.v This variation of 90 is satisfactory for the majority of sets since the characteristics are circular though greater variations are obtainable with different settings of the microphone ribbons. It is to be understood that separate microphones positioned at right angles may also be employed without departing from the spirit of the invention.
Thus, without actual physical or bodily translation of the microphone 22, eii'ective rotation thereof is obtained by the simple manipulation of the knob 54 on the dial 50, which eliminates wind resistance and disturbances caused by movement of the microphone while simplifying the boom structure itself.
I claim as my invention:
1. A microphone boomlsystem comprising a vertical standard,'a telescoping cross arm earried by said standard, a microphone carried by said cross "arm, said cross arm being adapted to move said microphone vertically and horizontally, and adjustable means mounted on said standard for producing a rotational effect to said microphone while maintaining said microphone stationary.
2. A microphone boom system comprising a' said standard for changing the directional charmicrophone mounted on the end of said cross.
arm, and means mounted on said standard for producing effective rotation of said microphone, said means comprising a miovable member slidable over a plurality fof resistances for changing the vdirectional characteristic of said microphone. `4. A microphone mounting comprising a standard, a cross arm mounted on said standard, a microphone mounted on said cross arm adapted to be moved vertically and horizontally, a cable from said microphone, said cable being attached to said standard, and adjustable means mounted onsaid standard and connected to said cable for varying the pointing of said microphone, said microphone remaining' `stationary during said variation.
5. A microphone mounting including a beam,
a microphone supported in xed relation with said beam, and adjustable means coupled to said microphone and attached to said beam for remotely controlling the pointing of said microphone while maintaining said microphone stationary.
6. A microphone boom system comprising a vertical standard, a cross arm mounted for rotation and pivoting on said standard, an arm member adapted to telescope within one end of said cross arm, a Weight member adapted to vary in position along'the other end portion of said cross arm, rotatable means mounted on said standard, means interconnecting said arm member, said Weight member and said rotatable means for extending and retracting said telescoping member and correspondingly varying the position oil said Weight member on said cross arm by rotation of said rotatable member, a microphone mounted at the end of said arm mem-v ber, a cable 4attached to said microphone and said standard, said cable being mounted on said weight member, and adjustable means mounted on said standard and connected to said cable for producing a rotational eiect to said microphone While maintaining said microphone stationary.
7. A microphone mounting comprising a microphone, an amplifier connected to said microphone, a hanger for supporting said microphone and amplier, a cross arm for supporting said hanger, a standard for supporting said cross arm,
resistances, means for simultaneously operating each of said sliders for varying the directional characteristic of' said microphone i'or producing a rotational effect to said microphone while maintaining said microphone stationary.
9. A microphone directional control comprising means for iixedly supporting a microphonev in a deinite location, a pair of resistances mounted in circulai` form remote from said microphone, electrical connections between said microphone and said resistances, a connecting slider for each of said resistances, means for interconnecting said 1 sliders for simultaneous operation thereof, one
position of said -means including all of one of said resistances and eliminating the other of said resistances, and another position of said means eliminating the first-mentioned resistance and including the second-mentioned resistance', a stationary scale associated with said last-mentioned means, and means for rotating said last-mentioned means.
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