US1659933A - Loud speaker - Google Patents

Description

Feb. 2l, 1928.

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UNITED lSTATES PATENT OFFICE.

RAYMOND L. WEGEL, 0F NEW YORK, Y.,

PANY, INCORPORATED, 0F NEW YORK,

ASSIGNOR TO WESTERN ELECTRIC COM- N. Y., A CORPORATION OF NEW YORK.

Loon SPEAKER.

Original application filed April 30, 1923, Serial December 1, 1925.

This invention relates to acoustic appara# tus, the object being to provide an acoustic device capable of faithfully-and efliciently reproducing sound vibrations within the audible range.

This is' a division of my application, Serial No. 635,407, med April 3o, 1923.

In accordance with the general features of the invention, there is provided an improved form of diaphragm and mounting whereby the system may have symmetrical modes of vibration, sensibly such that if the l lowest mode gives sharp resonance, it will be well below the voice range, or'if it gives broad resonance it may be in the lower part ofthe lvoice range,- and means for matching the impedance of the driving element to that of the diaphragm v whereby the vibrations may be efficiently and faithfully transmitted. p It is a well known fact that tones low in the musical scale are heard less distinctly than those high in the scale. This may be due to the ear being less sensitive to the lower frequency tones giving 'the impression that less energy is involved in producingr them.v However, more pleasing effects may be obtainedif the lower notes can be produced more distinctly. The horns usually heretofore employed in vconnection with talking machine and loud speaking receivers (are ieiiicient transformers of acoustic vibrations at the frequencies for which the ear is less sensitive. In many cases, therefore, the low notesappear to be entirely eliminated.v It has been. found that large diaphragme, when properly designed, reproduce the lower notes very efficiently. Other things being equal, the larger the diaphragm the lower its fundamental mode of vibration and the same diaphragm, when free, has a lower natural period than when rigidly secured at its periphery. In accordance with the invention a diaphragm preferably conical in form to permit the use of light materials and obtain the proper amount of stiffness is provided with an elastic mounting such that for low frequenciessubstantially the whole of the daphragm may vibrate. This arrangement possesses certain of the advantages of a free diaphragm and vhas a further advantage of' added stiffness whereby the cir-` No. 635,407. Divided and this application :Bled

Serial No. 72,449.

the present application, the acoustic device comprises as a front member a relatively large sheet of thin, light material formed to possess inherent stiffness, such as by being made in conical form, and porting member secured to the rear or hollow side of said sheet and extending inwardly in all directions so as to form with the front member a partially enclosed chamber. Means are provided for vibrating the front member in accordance with the sounds to be produced. The rear member is suitably'mounted on a support, in the present instance through the medium of means of attachment secured to the rear member at its inner edge.

In the particular embodiment of the invention shown in the drawing, Fig. 1 is a sectional view of a loud speaking receiver embodying the invention;

Fig. 2 is a rear view of the device shown in Fig. 1.

A standard 10 carries at its upper end a lhorizontal member-11, to one end of which is attached an actuating device 12. A conical diaphragm 13 is supported on the horizontal member 11 by means of the frustro-conical member 24 and is operatively associated with the actuating device 12 by means ofa rod 25. The frustro-conical member 24 is preferably made of the same material as the' ,but it is preferable to use one of the type described in Patent'No. 1,365,898 of January 18, 1921, to H. C. Egerton, suitablyattached an elasticy supto the diaphra m 13, as, for'exam le, in the manner described in my prior app cation of which the present application is a division.

A diaphragm having a diameter of about 18 inches suitably coupled to the receiver "system herein described has been found satisfactory.

Acoustic devices of the form and' construction substantially as described have been 'found very eective for the faithful production of sounds covering a wide range=- of frequencies including those low in the speech and music range, which have been mainly .or wholly suppressed by reproducers of the prior art.

rIhe presence ofthe rear member 24 has been found to increase very materially the effectiveness of the device in producing the lower tones. Itwill be noted that the diaphragm 13 has v4different extents of vibration at different frequencies, and as the lowest frequencies are approached more nearly the whole of the diaphragm vtends to be eiectively involved. The rear of the diaphragm 13 being partially closed oif byv the rear member 24, there is produced a confining action on the enclosed air atthose frequencies at which the diaphragm vibrates eectively system due to its manner of support andv permi-t the'system to vibrate more readilyand strongly at the `-low frequencies. At.A higher frequencies where the diaphragm has` a different extent of vibration so that, for example, onlya small portion v ibrates eectively, this additional effective ai-r mass which is produced by the confining tendency of the rear member 24 at the low lfrequencies yin the manner described above, disappears and permits the diaphragm to vibrate more edectively at the high frequencies Ithan it would if the same mass reactance were pres# ent asis present at the low frequencies.

A further advantage of the rear member 24 is that it serves to keep the sound issuing from the rear of the -dlaphragm -1'3 away from that produced by the front surface of the diaphragm, at least in the region ofthe reproducer itself, and reduces the. loss s which may result from an out-of-phase min? vling of the sounds from the two sides of the evlce.

Although the invention has been described in connection with a loud speaking receiver, obviously it may be readil adapted to a transmitter, or a phonograp reproducerby substituting means well known in the art vfor the actuating device described.

`What is claimed is:

l. An acoustic device comprising a conical diaphragm, a frustro-conical member secured at' its peripheral portion to the peripheral portion of said diaphragm to provide a hol- -lew chamber, and means for support-ing the device at the other edge of said frustro-conical member wherebyjthe peripheries of said I'diaphragm and member are free to vibrate.

2. An acoustic device comprising two conical members opposed to each other and secured at their peripheral portions to form a hollow chamber, and means within said chamber for driving one of said members.

`3. An acoustic device comprising in combin'ation an apertured supporting structure, an outwardly flaring member secured to said supporting structure, a sheet of light thin material secured to said 'darin member at its outer edge portion and forming therewith a partial enclosure,and means for vibrating said sheet in accordance with sounds of speech or music frequencies.

4. A loud speaker comprising a cone shaped member of paper-like material of the order of 18 inches in diameter, a frustrecone-shaped member, both members being secured together at their edge portions, said frustro-cone-shaped member having an aperture therein of an area equivalent to the area` of a circle equal in diameter to the order of one-half the diameter of said cone-shaped ,member, means attached to the frustro-coneshaped member at a distance from its periphery for supporting both members, and means to vibrate the cone-shaped member in accordancewith speech or music vibrations.

5. A loud s eaker comprisingtwo dished sheetssecuretogether .at 'their' edge por' tions to form a hollow enclosure, supporting means attached to one vof 'sa-id sheetsl 'remote from its edge and permitting the edgeto vibrate, a sound opening in one of said sheets and means insidel theenclosure for vibrating one ofgsaid sheets inaccordance with speech and music vibrations.

' 6. A loud speaker comprisingntwo dished of the sound opening therein and permitting the peripheral portions of said sheets to vibrate freely, and driving meansv supported from said mounting means and provided with a driving connection to a point on the other of said sheets.

7. A. loud speaker com rising' a hollow.`

bod presenting opposite y facing dished sur aces uniting with each other at their peripheral portions,'asound opening in one of said surfaces, means'remote from the peripheral portion of said loud speaker for mounting t e same and permitting the peripheral portion to vibrate freely, an ac vtuatingldevice, supporting means therefor connected to said hollow body in the vicinity of the edge of the sound opening therein,

said actuating device having a driving confront conical member'and cut away at its,

opposite end, `a support, and resilientfmeans connectingsaidv rear conicaly member with said support.y

9. Anacoustic device comprisingia front conical member, aninwardly turned rear conical member for separating acoustically the rear surface of the front conical vmember from its front surface, driving means for said front'conical member and means for supporting said member so that the edge of said front conical member is freeto vibrate when said driving means is active.

10. An acoustic device comprising a front conical portion', an inwardly turned rear conical portion for separating acoustically the rear surface of the front portion from its front surface and for minimizing the short circuiting of energy around.v the edge of the front conical portion, a support for said members engaging the rear conical por? tion, Aand driving means .attached to the front conical portion.-

11. An acoustic device comprising a conical member, driving means therefor attached to the apex thereof, flexible supporting means for the conical member inturned from the base thereof, said liexible supporting means serving to formN a partly enclosed chamber for air for the rear surface of the' front cone to add air mass reactance and to prevent the short circuiting of energy between the front and rear surfaces of the" conicalmember, and a support coaxial with the axis of the conical member for holding the flexible supporting means and the' driving means.

12. A loud speakerA comprising' a front cone memberv of light exible material, a

rear frustro-cone member joined at its outer edge portion to the edge portion of said cone member, means attached to said frustro-coneY at a distance from its periphery for supporting both members and means attached tothe front cone member for vibrating it in accordance with sounds to be produced, said last means when idle'permitting said members to assume a condition free from external tension.

13. A loud speaker comprising a large direct-acting cone member of light flexible material freely exposed on its exterior side to unconlined air, means on` its opposite side tor-.partially conlining a body of air comprising a rustro-cone member having its louter edge portion joined to the edge portion of said cone member, means mounted within the'enclosure formed by said two 'members for driving said cone member in accordance with sounds'to be produced, and

a common support for said driving means and said members.

14. .A loud speaker comprising a cone.

shaped-diapln'agm and a. frustro-cone shaped member having its outer edge portion secured directly to and continuously along the edge portion of said diaphragm so as to form .with said diaphragm a partially enclosed chamber, the inner edge of said frustro-cone member defining an aperture opening to the free air, and means. withinsaid chamber for actuating said diaphragm in accordance with soundvibrations.

15. An acoustic device comprising a large direct acting conical diaphragm, a rustro# conical member secured at its peripheral portion tothe peripheral portion of said diaphragm in such a Way as to constitute a struc-- j'tu'reliexible axially and rigid transverse to thejaxis of the cone, means for supporting the device at the other edge of said frustreconical member and driving means for said diaphragm positioned within the enclosure formed bysaid diaphragm .and said member.

In Witness whereof, I hereunto subscribe my name this 30th 4day of November A. D.,

RAYMOND L. WEGEL.

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