US1913451A

US1913451A - Acoustic apparatus

Info

Publication number: US1913451A
Application number: US729009A
Authority: US
Inventors: Clarence E Lane
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1924-07-30
Filing date: 1924-07-30
Publication date: 1933-06-13
Anticipated expiration: 1950-06-13
Also published as: DE556082C; GB237878A; NL18435C; FR600923A

Description

June 13, 1933. c, E, LA E 1,913,451

ACOUSTIC APPARATUS Filed July so, 1924 Patented June 13, 1933 UNITED STATES PATENT OFFICE CLARENCE E. LANE, 013 MONTCLAIB, NEW JERSEY, ASSIGNOR TO \VESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPGRATION OF NEW YORK ACOUSTIC APPARATUS Application filed July 30, 1924. Serial No. 729,009.

This invention relates to acoustic devices, the object being to provide a diaphragm which will faithfully and efficiently repro duce sound vibrations throughout the entire range of frequencies of importance in music and speech.

In accordance with the general features of the invention there is provided. an improved form of direct acting conical diaphragm in which the dominating modes of vibrations, particularly at the lower frequencies, are asymmetrical.

In its preferred embodiment the invention provides a large direct acting hollow acoustic diaphragm having an elliptical periphery, substantially free to vibrate, 'the front and back members of which have conic surfaces truncated obliquely to their axes so that the conic section formed by the conic surface and a cutting plane of either member is an ellipse. The members are secured together at their elliptical edges by any suitable means such as cement. In addition the rear member is provided with an opening whereby suitable actuating means may be mounted within the diaphragm in operative relation to the apex of the front member. A suitable standard carries a bracket for supporting the actuating device and an annulus "to which the inner edge of the rear member is secured for supporting the diaphragm.

It is a well known fact that horns and other devices commonly employed in connection with talking machines and loud speaking receivers are inefficient reproducers of acoustic vibrations at low frequencies. In many cases, the lower notes appear to be entirely eliminated. It has been found that large diaphragms 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 at its periphery has a lower natural period than when rigidly secured. In this respect diaphragms are analogous to open and closed pipes which for the same dimensions have a lower frequency when closed. The diaphragm of the invention is preferably conical in form to permit the use of light materials nance and noticeable distortion within the audible range. The present invention overcomes this diiiiculty by providing a diaphragm in which, due to the lack of symmetry in the construction, there are substantially no dominating modes of vibrations. Particularly is this true in the low frequency range where resonance is most noticeable in symmetrical diaphragms.

Referring to the drawing, Fig. 1 is a front view of the loud speaking receiver embodying the invention, Fig. 2 is a side View, and Fig. 3 is detail sectional view of the diaphragm.

The front member 5 is a conic surface truncated obliquely to its axis so that the conic section formed by the cutting plane. is an ellipse. Parchment paper or a good grade of hard drawing paper may be used for the entire surface or if desired the front member 5 may be made in two sections, 6 and 7, having overlapping edges in which case it is preferable to make section 6 of a hard surfaced blotting paper and the insertion 7 of a lighter and stiffer paper such as described above. The latter arrangement has been found to extend the range of response to slightly higher frequencies without affecting the low frequency range.

The back member 8 is preferably formed in substantially the same manner as front member 5, but is intersected by a plane at right angles to the axis of the conic surface to provide an opening in the diaphragm. Members 5 and 8 are secured in opposing relation at their outer periphery in any suitable manner. As shown tlieelliptical base of the member 5 is slightly larger than that of memher 8 which abuts against its inner surface and is cemented'thereto. I

A standard 9 carries an annulus 13 to which the inner edge of the member 8 may be rigidly attached by any well known means and forms a suitable support for the diaphragm. The standard 9 also carries a bracket 12 on which is mounted a suitable actuating means 10, connected to the apex of the front member 5 by means of a rod 11. As shown the actuating means 10 is supported so that the rod 11 has its axis coincident with the axis of the front member 5.

A diaphragm constructed in accordance with the invention gives a substantially smooth response characteristic over the range of frequencies of most important in speech r and music. F or example, a diaphragm hav ing the following proportions will give uni form response as low as fifty cycles per second: Major axes approximately 3 feet, angle at the apex approximately 148 and the eccentricity of the apex such that the ratio of the shortest element to the longest is approximately 1, to A diaphragm of this size and proportions reproduces the low notes of a pipe organ with exceptional fidelity without sacrificing any of the higher notes. Obviously for ordinary uses diaphragms as large as this are not required. For a diaphragm of this type the range of response will be approximately the same as for a symmetrical diaphragm of the same area but the response within this range will be much more uniform.

Vhat is claimed is:

1. A large direct acting diaphragm comprising an initially formed conical front member having an eccentric apex and an opposing initially formed conical rear member the outer range of which is secured to the outer edge of said front member.

2. A direct acting hollow diaphragm comprising two initially formed conical members having elliptical bases joined together.

3. A direct acting diaphragm comprising an oblique conical front member having an elliptical base and an opposing rear conical member having bases in planes oblique to each other for supporting said front member.

4:. A direct acting diaphragm comprising a conical member having an eccentric apex and an apertured flexible member having conical surface yieldingly supporting said conical member at its periphery and extending inwardly therefrom.

5. A large direct acting hollow diaphragm one member of which comprises the surface of a cone of revolution between its apex and a plane oblique to its axis.

6. A large direct acting diaphragm comprising a front conical member having an elliptical periphery and a rear conical member comprising that proportion of a conic surface lying between truncating planes oblique to each other for supporting said front memher.

7. An acoustic device comprising a diaphragm having a front conical member the periphery of which is elliptical and a rear opposing truncated conical member the smaller and larger bases of which are circular and elliptical respectively, the elliptical bases of said front and rear members being secured to gether, means associated with the circular base for supporting said diaphragm and actuating means carried by said supporting means operatively associated with said front member.

8. An acoustic device comprising a conical diaphragm having an oblique conical member, actuated means therefor, and means c0- axial with said member for connecting said actuating means thereto.

9. In an acoustic device a direct acting diaphragm comprising an oblique conical front member having an elliptical base, the length of the longest element of said front member being approximately 3 times the length of the shortest element, and an apertured flexible rear member supporting said front memher at its periphery and extending inwardly therefrom.

10. In an acoustic device a diaphragm comprising an oblique conical member having a vibratile periphery and means supporting said conical member whereby its outer edge has various degrees of stifi'ness.

11. In an acoustic device, a large direct acting conical diaphragm, actuating means eccentrically attached thereto, and means supporting said actuating means and eccentrically supporting said diaphragm.

12. A hollow acoustic diaphragm comprising two oblique conical members joined together at their bases.

13. An acoustic device comprising a diaphragm, means spaced eccentrically from the periphery for supporting said dia hragm, and means carried by said support or actuating said diaphragm.

14. A11 acoustic device comprising a conical diaphragm, actuating means therefor, and means transmitting vibrations from said actuating means to said diaphragm in a direction oblique to the plane of the periphery of said diaphragm.

15. A sound reproducing diaphragm con sisting of a large direct acting sound reproducing diaphragm consisting of a thin sheet of material having an elliptical periphery, means for supporting the periphery of said diaphragm for relatively free vibration, and means for subjecting said diaphragm to mechanical vibration substantially at the center thereof.

16. A sound reproducing diaphragm comprising a large direct acting cone of thin sheet material having an elliptical periphery, means for flexibly supporting the periphery thereof, and means for subjecting said diaphragm at its apex to mechanical vibration.

17. In a sound amplifying device, a diaphragm, said diaphragm comprising an elliptical cone and an elliptical truncated cone surrounding said elliptical cone, the lesser circumference of said truncated cone and the circumference of said cone being coincident.

18. An acoustic device comprising a diaphragm having an elliptical periphery, a member associated therewith in such manner as to enclose a body of air between it and the diaphragm, and actuating means operatively connected with the diaphragm.

19. An acoustic device comprising a diaphragm, the outer edge of which is elliptical in form and substantially free to vibrate, a member associated therewith in such manner as to enclose a body of air between it and the diaphragm, and actuating means operatively connected with the diaphragm.

20. An acoustic device comprising a conical diaphragm, the outer edge of which is elliptical in form and substantially free to vibrate, a rear member associated therewith in such manner as to enclose a body of air between it and the diaphragm, and actuating means operatively connected with the apex of the diaphragm.

21. An acoustic device comprising a large direct-acting dished diaphragm, the outer edge of which is elliptical in form and sub stantially free to vibrate, a member associated therewith in such manner as to enclose a body of air between it and the diaphragm, and actuating means operatively connected with the diaphragm at a portion thereof removed from its outer edge.

22. An acoustic device comprising a diaphragm having an elliptical periphery, means on one side of said diaphragm for actuating it, and means connected to the diaphragm periphery and extending away from the dia phragm on the same side of the diaphragm as the first means, said second means defining an air body on said one side of said diaphragm.

23. An acoustic device comprising a vibratory conical member having an elliptical periphery, a hollow member having an elliptical peripheral portion connected to said conical member at its periphery, and means responsive to impulses of sound wave frequency connected to the conical member.

24. An acoustic device comprising a vibratory conical member having an elliptical periphery, a hollow vibratory member having an elliptical peripheral portion connected to the conical member at the periphery thereof, and means responsive to impulses of sound wave frequency connected to said conical member.

25. An acoustic device comprising a vibratory conical member having an elliptical periphery, a hollow vibratory member having an elliptical peripheral portion connected to the conical member at the periphery thereof and supporting said conical member and means responsive to impulses of sound wave frequency connected to said conical member.

26. An acoustic device comprising a directacting vibratory member having a plurality of portions one of which is a lighter and stiffer material than the other and each of which has an elliptical periphery, means for supporting said member, and means responsive to impulses of sound wave frequency connected to said member.

27. An acoustic device comprising a hollow vibratory member having a conical and a frusto-conical portion each having elliptical peripheries, and another hollow member supporting said first member, said second hollow member being connected to the frustoconical portionat the periphery of the larger base thereof.

In witness whereof, I hereunto subscribe my name this 28th day of July A. D. 1924.

CLARENCE E. LANE.