US2007746A - Acoustic device - Google Patents

Description

cierrensteif-E1sv l1 A'11-:1\1'1f OFFICE 4 Radio Corporation of Americana corporation of t Delaware l,Original application July 20, 1925, Serial No.

44,735, now Patent No. 1,868,019, July 19, 1932.` Divided and this application March 21,11928, Serial No. 263,378 1 18 `Claimsl (Cl. 17g-#1155) This invention relates to acoustic devices for Vthedrawing) having au Openiugiu Which One @11d use in reproduction of voice, music or other sigof a diaphragm or cone 54 is supported bya ring nals. It has for its objectV also the'truer and more ornumber of strips i I ofV resilient material such exact reproduction, constancy of volume and in vras rubber, leather or-other materialsorV fabrics. general more faithful likeness/to the original than Plate 3 not only serves tosupDOlt the 00H8 but f 5 1'ie`1etof`ore.` l. ,t y, A also serves to prevent the vibrations. from the It is known that whenever a `vibration was imrearthereof from affecting those emanating from pressedupon anyv vibratile body that there are the front. V,The frustum or coneE servesas the certain frequencies at which reproduction will sound radatinssmedum andpmay be formed of be most eiiicient while at all` others `more or less sorne semi-rigid fabresueh as paper, parchment, 1ro; ineiiiciency occurs resulting in exaggerationl of" cardboard or of alight metal Such aS aluminum certain tones as wellasother'undesirable effects. 0.1" Clulalumiu- This invention attempts .to robviate. these diffcul- At the rear of the `cone is mounted a magnetic ties by so varranging theoscillatory .member-or System 59 Which may be a Permanent magnet 01 members thatdifferent e1e`ments thereof will rean electro-magnet energized by` Coils 2'fqtnd` 5U. 151

i. 55 lL:nountiifig`plate (aportionfonly being shown in spond at their Vmost yecientY period Aof VVibration This Ina-guet iS DTOVideCl With D01@ 131666558 and at different frequencies,` thereby causing the rey591Which are separated by asubstantially circular ,productionY to be 'more uniform and of a more" fluX gapi aud a Centralple pie@ 59 SeparatCd constant volume, aswell asgiving greater sensifrnpole 59 by a Substantially Circular uX @,vitgapw f 2o 'Ihis invention alsorelatesto telephony, telegy ThailuXV pIOduCed DaSSaS'tllIOl-lgh the all gaps raphy,and other allied arts. More specically the between the IeSpeCtiVe D016 DCCS lWithil'l the `arrange:nents hereinfdisclosed represent'what is air gaps are lOQatadCyliuCllfiCal `SleSVS 52 and 57- commonly known as loudspeakers or electrical These SleeVeS lmay be 0f QODlD-l, aluminum 01'v reproducers and the like although it is not intendother lowresistant electrically conductive mateed to .limit its use 'to` this." particular iield.` It frial, or. maybe in the form of multi-turn coils `miglitas well beused with phonographs and other `mounted -on properbrackets or supports. As Vresonant reverberating systems.,` It is also usefulv SllOWIl in Fig. l, Cylindrical SleeVeS aT'l1S i-,V TiV- `wherev`er large amplitudesof vibration `are deeted by means of rivets 55 t0 dierel'lt parta 0f silredatj` pnwithin the, audio Vfrequency range Vthe cone `5ft or fastened by any other suitable 3o `Which should be of constant value,V f .means In Fig-1a multi-turn coils 5ta and 53a Otheriobjects and advantages will be apparent are mountedonsuitable cylindrical supports 52a upon reading thefollovving disclosure including and 57a. l Y

\ lspecication, claims andannexed drawings; This It has beenfound best to make the sleeves 52 applicationr'js a division" of a' parentapplication and 5l as light as possible in orderthat they may 35 i'lled by John MintonV and ymyself` on July 20,` 1925, respond to high frequencies more readily Without Serial No. 44,735, nowPatent No. 1,868,019, grant-` absorbing too much energy by their inertia. As ed July 19, .1932." y l, g y] shown,lse`ctions56.arercut out to decreasethe One embodiment` f .the invention is shown in Weight of sleeve` 52. Instead Yof terminating as 40 theaccompanying-drawing if1'iv1`hich, I vshovvnthe frustum 5l!V may be extended' to a 40 Q vFig. lis a vertical cronsssection of the vibrating point Vat its small end,A to form a full cone, in system, v g i t which 'case sleeves 52 andfEl Would be made ,Figi ljfis a sectionalV View of"a`m`odi1'ication flonger. V fof the apparatus sl'iovvrfiinl'ig.v 1, f x Invthe operation. of the ,modification shown in Fig. 2 isa section.througl'iV the line 2--2 of Fig. Fig. 1l, a variable undulating or* alternating -elec- 45 1; and.V -tri'cal currentis caused to flow Vinthe coils Bland ,Figq is a series of graphs ofthe sound charl53"-in-.accordance with the'vibrations which are 'ltacteristicsof thedevice, 1 l H l i ldesired to be impressedupon the cone 54." TheseVK lFig. 4 is a diagrammaticI view showing how the currents will `inducevari'able Lcirci'ikar eddy cur- Si alDll,lagm4 will .vibrate t atma certain high frerents in sleeves 52 and 51, in a manner Well known 50 -quencmand t v, Vin theart.` `.ijvariableforceactingfon'conduc-- Fig; 5' is 'a' diagrammaricillustration, of aptors 52 and 51 will result due to the action of 'proved circuits for the.,apparatus.v f 1 thetpermanent magnet fields in air gaps lilY and Inthe drawing number denotesanextended 62 on thecurrentsin sleeves 52` and 51. The

4magnitude of these forces, as is wellknown, is 55 vof .the front or large portions of vthe cone. vthese two portionsfare operated jointly from the directly dependent on the length of conductor, strength of current, and strength of the steady magnetic eld. The direction of the force will be such as to move the cone along its axis. In Fig. la where a pair of coils Sla, and 53a attached to the cones are used to carry the modulated current instead of the sleeves 52 and 5l, the coils 5i and 53 will of course be dispensed with. The action however will be the same.

As shown, the sleeve 52 is connected to an outer part of cone 54 and therefore will produce a greater response to vibrations of lower fre quency, when the cone Vibrates as a whole, while' sleeve 5l being connected to one end of the cone, will be more responsive to vibrations of a highv frequency producing nodes and anti-nodes along the length of the cone 55s. This action of the sleeves may be aided by permitting only the lower frequencies in the outer winding 5| while the higher frequencies are confined to the inner winding 53 by any suitable circuit arrangements such, for example, as those shown `in lthe application of VJohn Minton and myself, Serial No. 35,893, filed June 9, 1925. Fig. 5 illustrates diagrammatically a circuit corresponding to the circuit shown in Fig. 2 of application S. N. 35,893. The condenser'll keeps the lown frequencies out of the inner Winding 53a and the inductance i8 keeps the high frequencies out of the outer winding 5 la.

The outer portion of the cone, particularly where the 'cylinder 52 is fastened to it, will be hard to s'et in vibration at higher frequencies because of the large mass of cylinder 52 and for this reason will act as a nodal region forhigh frequency vibrations. The form of vibration of the cone for higher frequencies will ythen be somewhat as shown in Fig. 4 the portions b and c will vibrate in sections, the portionV a' where the sleeve 52 joins the cone being a nodal region for the high frequency vibrations. The actual motion of the cone willthen be a back and forth rmotion similar to that of la piston combinedowith the sectional vibration 'or whipping action. VFor .moderately high frequencies the pistonaction vwill be almost entirely effective. However, as the first frequency at which this whipping action of the cone becomes more pronounced, the amplitude of'this'mode of vibration becomes much 'greaterthan that of the pure piston motion and as 7a result much more sound is radiated at this frequency. This mode of vibration occurs not only at this one frequency buty at still higherv 1) and by the current flow .in coils Bia and 53a (-Fig. la) itwill be understood that any other desired means may be used to operate the sleeves.

' If the'vibrating system shown is analyzed and theA sound characteristics thereof plotted, curves similar to those shown inFig. 3 will result, ordinates representing audibility and abscissas representing frequency. Curve l shows thejcharacteristic of the rear portion of the cone to which sleevel57 is attached' while curve 2 shows that If same source or bythe same current, the two characteristic curves will be superimposed upon each other giving a resultant 3 which shows a smaller percentage of variation.

WhileI have shown the diaphragm for emitting the sound to be of conical shape it is understood that diaphragms of other shapevwhich function in a similar manner may be used instead.' without departing from the spirit of my invention. That for which I` ask protection by Letters Patent isz- 1'. Inan acoustic device, a vibratile member, an actuating` element, .means attaching said elementto the outer portion of said member, and means responsive to high frequencies for vibrating the inner portion -cf said vibratile member whereby a nodal region is produced adjacent said 'first named means.

" 3. Acoustic apparatus comprising a vibratile diaphragm system having an outer diaphragm portionl more responsiveA at lower audible fr equencies than at some higher audible frequencies, and a central portion moreresponsive at said yhigher audible frequencies than at said lower audible frequencies, and separate means for vibrating each of saidy diaphragm portions.

` 4. Acoustic apparatus comprising a' vibr'atile member, a coil responsive to high frequencies attachedto said vibratile member for causing vibration thereof, anda coil responsive to lowfrequencies also attached to said vibratile member 'for causingr vibration thereof. y

L 5, Acousticr apparatus comprising a 4vibra/tile diaphragm and a pairof separate windings for vibrating said diaphragm, one of said windings `being responsive .to high yfrequencies. andthe other of said windings lbeing responsive .to low frequencies. M

6. Acoustic apparatus comprising a truncated conical diaphragm, a pair of 'separate windings for vibrating said diaphragm, one of said windings being adapted to respond to high frequencies and the other winding being adaptedta respond to low frequencies, and a'coil form-secured to said diaphragm atits smaller base, at leastone of said windings being located on said coilv form.

'7. Acoustic apparatus. comprising a frustum shaped diaphragm, va winding4 responsive to high frequencies connected, to said diaphragm immediately adjacent thev smaller base thereof, and a vsecond winding for said diaphragm located at a lposition more remote from saidY smaller base than the position of the. rst mentioned winding.

8. Acoustic apparatus comprising a magnet system, means for producing sound waves, a pair of voice coils connected Ato said means forV producing sound waves and arranged to be threaded by lines of force from said. magnet system, one of saidl coils being adapted to respond to high frequencies and the other coil being adapted to respond to low frequencies,f and lcircuits for supplying to each coil the frequencies to which Vit is adapted to respond. v

9. Acoustic apparatus comprising a truncated conical diaphragm, ay voice coil responsive to high frequencies, a voice `coil responsive tolow fre- ,quenciea means for transferring lmechanicalviconnected to said diaphragm immediately yadja4 cent its smallerbase', a `magnet system providing lines of force to thread saidvoicecoils, separate circuits `for energizing said voice coils separately from a single source of` energy,` and -a condenser connected in series in the circuit" supplying energy to the voice coil responsive tohighfrequencies for substantially keeping lowfrequencies out oflthat voice coil. i

. l0. Acoustic apparatus comprising a truncated diaphragm, a pair of separate voicecoil windings connected with said diaphragm, means connecting at least onef of said` windings to said diaphragm immediately, adjacent the smaller base "thereof, circuits for separatelysupplying energy to said windings, and means in `one of` said circuits for causing a predomination of certain frequencies in the winding energized by that circuit. j 11. Acoustic apparatus comprising a diaphi'agm, a plurality of voice coils connected with said diaphragm, meansforming` magnetic lines of force threading said voice coils, and circuits-i for supplying energy t said voice coils separately and at diierent frequencies. y

12. A sound reproducer of theielectrodynamic type comprising an` electromagnetic system, a

` sound reproducing diaphragm and a plurality of windings movable withgsaid` diaphragm, means i l f whereby said windings areresponsive to different ranges of audio frequency notes, `saidwindings operating in theeld of said electromagnetic l system for conjointly imparting vibrations to said diaphragm. 1

, 13. In aloud speaker, a diaphragm, a plurality r of actuating coils connected to said q diaphragm and movable therewith, a source of electricwaves of frequencies extending over a substantial part of the audible spectrum, circuit connections be`` tween said source and saidcoils and means included in said:4 circuit connectionswhereby one of said coilsis rendered most responsive to a band ,of frequencies embracing'a fractional part of the audible spectrum, and another of said coils is rendered lmost responsive to a different fractional part of the audible spectrum.

14. A sound reproducer of the moving coil type comprising an electromagnetic system, vibratory n sound reproducing means, a plurality of windings movable with said vibratory means and operable in the field of said electromagnetic system to Aactuate said means, andmeans whereby said Windings are responsivev to'different ranges of audio frequency notes.

15. A loudspeaker having a diaphragm, a plurality of movable coils for actuating said diaphragm, a field magnet structure operatively associatedwith' said coils, means for simultaneously connecting said coils in a circuit of variable impulses, and means whereby said coils accentuate dilerent bands of frequencies. i

16. `In an electrodynamic translating device a plurality of windings movable to cut the lines of '.quencynotes.

18. In a loudspeaker, the combination of a magnet system adapted to, provide magnetic lines offorce, a plurality of independent coils mounted in operative relation to the' pole pieces of said magnet system, said coils being positioned to cut said magnetic lines of force, means whereby each of said coils is eiciently responsive to a selected band of audio frequencies, and sound reproducing means controlled by said coils to reproduce practically the'entire audible range of notes.

i ABRAHAM S. RINGEL.

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