US1930912A - Sound reproducer - Google Patents

Description

Oct. 17, 1933;. E, H SMYTHE 1,930,912

SOUND REPRODUCER Filed Aug. 17 1926 a W ju/ Mme Patented Oct. 17, 1933 v a A 9 2 Western Electric Company, Incorporated, New York, N. Y., a -corporation ofgNew York I Applican 's ugust 17,1926. s rial no. 129,734 l n v fzo Claims. (01.1'81-31) V This invention relates to reproizlucers soundreproducer having a modified form of pe-H employing large directractingdiaphragms. ripheral' support and havinga partially enclosed An object of the invention is to reproduce air chamber on both sides of the diaphragm; efiiciently and faithfully all sounds within the Fig.5 is a partial cross-sectional view showing I 5 audible range. r p f '1 f a modification of the double air chamber con 60,.

Another object of the invention isto increase struction. V j the energy imparted to the air from a sound, Thev sound reproducer shown-in Fig. 1 comradiating surface and to'reduce the radiation prises a radiator having a front conical diaof out of phase energy, -I phragm anda rear frusto-conical section ll 10 The invention provides a sound 'reproducer cemented together base to baset Both portions es having a transversely rigid and preferablyconiofthe radiator are preferably constructed of cal diaphragm and an annular transversely rigid light stifi material, such as thin wood veneer or and preferably frusto-conical section which are blotting paper. An annular binding strip 12 is supported solely at their common periphery in; disposed about the truncated end of the frusto-' 15 such a way that the periphery is constrained conical section 11- for apurpose hereinafter de- 70. with respectto transverse movement and: is left scribed. 7 H a a free and unconstrained with respect to radial Theradiator is mounted within an annular and torsionalmovement. V f trough-like framel3 preferably comprising two Low frequency sound vibrations appliedatfthe semi-circular portions which may be clamped apex of the diaphragm..cause the periphery to togetherby means of bolts l4 after the radiator 75, expand and contract permitting the entire suris placed inside the-frame. Theidevice ismount face of the diaphragm to vib'rate ina direction ed; on a stand 15 havinglan upright portion 16. transverse to the plane of its base, andproducing to which are bolted diametrically opposite edge; a transverse movementof the frusto-conical secof theframe l3. 7 I f r tion in opposite direction to the transverse move- ;"I he cones 10 and ll are supported at their so, ment of the diaphragm, As aresult of this accommon periphery by means of tautcords -17; tion, the soundwaves transmitted by the outer passing through-the small holes 18 in thede surface .of the frusto-com'cal section'are in phase pending rims of the frame 13,. V The; cords 1 7 may with the waves-of corresponding frequencies be laccd backandforth th h 3 1 9 51 30 transmitted by the outer surface of th'e conical as; is m rei marl shown in Eigs 2 and t 85H,

40 serves to improve the radiationof energvin the H.,C-. Ha1 rison.-

diaphragm, and the er surfaces of 5 these commonperipheral edge of the cones being asmembers cooperate to'produce, sound, waves: in tenedto. the cords by means of cement l9, A.

phase opposite tothat of ,thewavesprodu d'by supporting member 20 mounted on the upright the outer surfaces, .1 f a v 1 I 35 Accordingto another feature of; the invention, ,diaphragm 10. The member 22 is provided for '90. a partially enclosed air chamberis provided on connecting the driving stem of the receiver unit each side of the conical diaphragm; The-col to the apex of thediaphragm. Thereceiverunit umns ofair confined in each air chamber add 2l maybeof the typedisclosed and claimed air mass reactance to the diaphragm, which U. S. Batent1,709,571,;granted April 16, 1929 tolow frequency range; f i 1, ".In'theqconstruction described above the pe- The inventionswill be described indetailin ripheryj oftthe-double cone structure is conconnection with the accompanying drawing, in strained in a transverse directionby means ofthe which similar reference characters designate; cords 17-, hut;is left free to move radially and similar parts in the, difierent 1 views, and in tqrsionally. This construction reduces the oppo- 10o which:

Fig. l is a side. viewppartly in section, of a forces intl'ieiront and rear cones and'givesfree sound reproducer comprising a..double cone play;to]any-;-tendency toward peripheral exparnstructure supportedat the periphery in accordsionand contractionatthe periphery as the dia-f ance with the invention; 3 1 p H I I a Fig. 2 'isa front elevation on a reduced scale; and contracts radially,andneripherally-as a reof the sound reproducer showninFig- 1; Y 7 .sultpf the driving forceappliedatthe apex this] 7 Fig. 3 is afragmentary: view illustrating the. expansion and contraction produce a transverse, method ofsupporting the double cone structure; movementi of the rear frusto-conicalsection :11; r

Fig. 4 is. aside view, partly in sectiom offa inopposite direction to thetransversemovemont very light gauge 2 of the conical diaphragm 10. Pressure waves which are produced by the frusto-conical section 11 are therefore in phase with the waves of corresponding frequencies produced by the diaphragm 10. This particular action occurs in the low frequency range where it increases and emphasizes the pulsating, or pumping action in the enclosed air space between the front and rear cones. This has the effect of increasing the air transformer action and the effective air mass reactance upon the rear surface of the diaphragm 10 and improving the response in the low frequency part of the scale.

The truncated end of the frusto-conical section 11 is left unsupported and free to vibrate, the sole support being at the common peripheral edge of the double cone structure. The binding strip 12 disposed around thetruncated edge of the frusto-conical section 11 is primarily to give circular rigidity, and to provide stiffening of the inneredge to resist the radially inwardly and I outwardly moving forces caused by the peripheral expansion and contraction, and thus make these forces effective in producing the transverse movement of the frusto-conical section 11. By

giving this stiffening ring the proper value of stiffness with respect to its mass, it is possible to exercise control-over the part of the frequency scale at which the pumping action of the frustoconical section will be made effective.

The modification of the invention shown in Fig. 4 includes a stationary supporting wall 23 in the form of a truncated cone which is mounted at its small and in the annular member 24 in any suitable manner. Since the mass of this stationary wall is unimportant, it may be made entirely of metal, heavy cardboard or the like. The peripheral support for the sound radiator comprises aring 25 of light flexible material, such as duralumin or light stifi paper, which as shown may be made integral with the stationary wall 23 or may be attached thereto in any suitable manner. The ring 25 is transversely slotted to provide a plurality of tongues 26 which offer very slight resistance to the radially acting forces developed in the conical diaphragm l0, and at the sametime offer a large resistance to transverse movement. The common periphery of the conical diaphragm 10 and the frusto-coni cal section 11 is seated in the upturned ends 2'7 of the flexible'tongues 26.

In this construction, openings are provided on both sides of the conical diaphragm at 12 and 24, respectively, the frusto-conical section 11 and' the stationary wall 23 closed air chambers on phragm. The air enclosed in these chambers is found to add air mass reactance to the diaphragm, which tends to" lower its fundamental frequency and hence improves the performance in the low frequency range. Since it is desired in this construction to'secure the maximum air transformer action on cal diaphragm, a ribbon of light cloth a 28 is pasted over the peripheral supporting ring 25 in such a way as to cover the slots formed by the tongues 26 without preventing the tongues from yielding to the radial movements of the diaphragm. The cloth covering 28 is to prevent air leakage through the peripheral supporting ring.

providing partially en-' Fig. 5 shows a modification of the double air chamber construction of Fig. 4. The'edges of the-section 11 and the wall 23 are bent outwardlyto form flanges 29. The periphery of the diaphragm i0 is supported between loosely packed both sides-of the dia-- both surfaces of the coni 1.- A sound reproducer comprising a large direct acting diaphragm having a configuration to impart to it inherent stiffness from the center outwardly, and means for constraining the edge of said diaphragm with respect to transverse movements, said means exercising substantially no constraint to movements of said diaphragm edge in a radial direction.

2. A sound reproducer comprising a conical diaphragm driven at the apex, and means for constraining said diaphragm in a direction perpendicular to the plane of its base the periphery of which may move substantially freely in a direction along said plane.

3. A sound reproducer comprising a conical diaphragm driven at the apex, and a support for the base of said diaphragm including a plurality of flexible members maintaining said base in one plane, said members imposing substantially no restraint to the expansion and contraction of the base in response to sound vibrations.

4. A sound reproducer comprising a conical diaphragm driven at the apex, and a support for the base of said diaphragm including a plurality of circularly disposed members which are flexible only in a direction of the plane of said base.

5. A sound reproducer comprising a conical diaphragm and a frusto-conical section having their bases joined together to form a common periphery, and means for constraining said periphery with respect to transverse movement, said means exercising substantially no restraint to the free movement of said periphery in a radial direction.

6. A sound reproducer comprising a conical diaphragm and a frusto-conical section bound together along an edge, and a support for said bound edge including a plurality of flexible membersmaintaining said edge in one plane, said support exercising substantially no restraint to the expansion and contraction of said bound edge in response to sound vibrations.

'1. A sound reproducer comprising a conical diaphragm driven at the apex, a frusto-conical section having its base joined to diaphragm, and a flexible support for said diaphragm and said frusto-conical section, said support constraining said joined bases to movement in one plane to cause said frusto-conical section to move in an opposite direction to that of said diathe base of said riphery, means for driving said conical diaphragm at the apex, and a support for said periphery including a plurality of circularly disposed members which are inherently flexible in a direction of the plane of said periphery and are inherently rigid in a direction perpendicular to the plane of said periphery.

9. A sound reproducer comprising a large direct acting diaphragm, and means providing a partially enclosed air chamber on both sides of said diaphragm, the area of the opening of each chamher being smaller than the radiating area of the diaphragm.

10. A sound reproducer comprising a conical diaphragm, a frusto-conical supportformingi a partially enclosed air chamber on one side of said diaphragm, and a frusto-conical section forming a partially enclosed air chamber on the other side of said diaphragm;-

11. A sound reproducer comprising a conical diaphragm driven at the apex, a frusto-conical section forming, a partially enclosed air chamber on one side of said diaphragm, a stationary frusto-conical support forming a partially enclosed air chamber on the other side of said diaphragm, and means for flexibly connecting said diaphragm and frusto-conical section to said sup port. I

121A sound reproducer comprising a conical diaphragm driven at the apex, a frusto-conical section attached to and forming a partially enclosed air chamber on one side of said diaphragm, a stationary frusto-conical support forming a partially enclosed air chamber on the other side of said diaphragm, and means for connecting said diaphragm and frusto-conic'al section to said support including a plurality of circularly disposed memberswhich are inherently flexible only in a directionof the plane of the base of said diaphragm.

the plane of said edge, said means imposing substantially no restraint to the movementof said edge in the plane of the periphery. 1

14. A sound reproducer comprising a large direct acting diaphragm having a configuration to impart to it inherent stiffness from the center outwardly, and means to allow of a minimum of movement of s the edge of said diaphragm in a direction transverse to the plane of its base, said member, an actuating said housing,

element, and a p 3 means offering a minimum of restraint to the movement of said edge in the plane of the said diaphragms base.

15. A loud speaker comprising a supporting member, a housing carried by said supporting device positioned within a cone shaped diaphragm actuated by said actuating device, and a horn carried by said housing and conforming to the. shape of said cone shaped diaphragm for providing a chamber between the exterior surface of said cone shaped diaphragm and the interior wall of said horn.

16. A sound reproducing device comprising a large size diaphragm inherently weakening the higher harmonics, and an air obstruction wall opposite said diaphragm to form an outwardly flaring air chamber for accentuation of said high- ,er harmonics.

17. A loud-speaking device comprising a large sizecone-shaped diaphragm, and an air obstruction wall opposite said diaphragm to form an outwardly flaring sound air chamber.

18. In combination with an electric loudspeaker, a loudspeaker actuating element, a coneshaped sound producing surface operated by said sound amplifying chamber associated. with said cone-shaped surface to form a tapering opening towards the apex of said cone.

19. A loud speaker including a base, a strut extending from the base, a diaphragm mounting means supported by the strut, a diaphragm mounted on the mounting means, and asound reproducing unit connected to the diaphragm for applying vibrations thereon, and means forming a loadingchamber for applying an air column load on the diaphragm. V

20. A sound reproducer comprising a direct acting diaphragm, and means including a frustoconical member providing a partially enclosed air chamber on each side of said diaphragm, the larger baseof said member abutting on the periphery of said diaphragm.

EDWIN I-I. SMYTHE.

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