US1742002A - Eccentric cone loud-speaker - Google Patents

Description

A. M L. NICOLSON ECGENTRIC com: LOUD SPEAKER Dec. 31, 1929.

Filed March 11, 1927 INVENTOR ALEXANDER MtLEAN NICULSON ATTORNEY Patented Dec. 31, 1929 UNITED STATES PATENT OFFICE ALEXANDER MCLEAN NICOLSON, OF NEW YORK, N. Y., ASSIGNOR T0 WIRED RADIO, INC., 01* NEW YORK, N. Y., A CORPORATION OF DELAWARE EGCENTRIC CONE LOUD-SPEAKER Application filed March 11, 1927. Serial No. 174,491.

This invention relates to sound reproducing apparatus and more particularly, to so called loud speakers adapted to reproduce audible sounds such as speech, music and the like, from mechanical vibrations corresponding thereto, the mechanical vibrations being derived from electrical oscillations corresponding to the sounds to be reproduced, or from a mechanical record of the same.

It is an object of this invention to provide a loud speaker or sound radiating device which shall be as nearly as possible, a faithful reproducer of the Vibrations impressed thereon, and, to this end, shall be free from parasitic resonance at various frequencies which would tend to diminish the accuracy of reproduction desired.

It is a further object of this invention to provide a sound reproducer utilizing a conical diaphragm having sound radiating elements of a range of size whereby certain parts of the diaphragm shall be more effective at certain frequencies than at other frequencies in order to obtain a better tonal balance between various frequencies.

It is still a further object of this invention to provide apparatus comprising a cone diaphragm in which sound vibrations may be initiated at different points, in different phase relation, thereby controlling the mode of vibration of the diaphragm.

It is still a further object of this invention to provide such apparatus inwhich the driving force is supplied by a piezo-electric crystal device. Still other objects of this invention will be apparent from the specification.

The features of novelty which I believe to be characteristic of my invention, are set forth wit-h particularity in the appended claims. My invention itself, however, both as to its fundamental principles and as to its practical embodiments will best be understood by reference. to the specification and the accompanying drawing, in which,

Figure 1 is a view of a loud speaker embodying my invention with the base shown in side elevatlon and the sound reproducing diaphragm illustrated in cross-section; Fig. 2 is a front view of the loud speaker of my invention; Fig. 3 is a top view of the loud speaker With the sound reproducing diaphragm shown in lateral cross-section.

Fig. 4, is a sectional view, similar to Fig, it, of a slightly modified form of my invenion.

Fig. 5, is asimilar View of still another form of my invention.

In accordance with this invention, I utilize, for the purpose of producing sound waves, a relatively large rigid conical diaphragm having at least one side thereof freely exposed to unconfined air. Means are proyided for. driving or vibrating the diaphragm 1n accordance with the mechanical vibrations corresponding to the sound Waves to be reproduced. The conic'al diaphragm is preferably arranged in such manner that the apex of the cone is unsymmetrically disposed with reference to the periphery thereof; in other Words, the generatrix of the conical surface. The driving force is preferably, although not necessarily, applied at the apex of the diaphragm as a mechanical stress or vibration having a component in the plane of the material of the diaphragm.

As will be understood, vibrations impressed upon the apex of the diaphragm, cause a stress wave or vibration to travel outwardly in all directions toward the periphery of the cone.

The provision of the apex in an unsymmetrical position with reference to the periphery of the diaphragm provides sound radiatingsectionsofvarying areas,varyingfro1n a minimum area at top of the diaphragm to the maximum area at the bottom of the diaphragm, and the sound radiating characteristics of the different areas are different, since the natural resonances of the various parts of the diphragm are different. As a result of this, it is possible by proper proportioning of the various parts to provide a better balance between low, high and intermediate frequencies than in devices of the prior art, 95 in which the driving force is applied to the apex, which is at a symmetrical point with reference to the periphery ofthe diaphragm and in which the sound radiating areas around the periphery are all the same size.

Under certain conditions, I may prefer to apply the mechanical driving force to a plurality of points on opposite sides of the axis of symmetry of the diaphragm in a predetermined dillerent phase relation: for example, one side of the diaphragm may be driven forward while the other side is being driven to the rear. It will be understood that under these conditions, a different mode of vibration will exist in the diaphragm from that existing when the driving force is applied at a single point such as the apex and a difference in tone reproduction will result.

For the purpose of driving the conical diaphragm, I prefer to utilize a piezo-electr1o crystal device, such for example as acrystal of Rochelle salt exhibiting the well known hour glass configuration, or a composite piezo-electric device, such as shown and described in my copending applications:

Cast piczo-electric device, Serial No. 155,897. filed Dec. 20, 1926.

Composite piezo-electric crystal device, Serial No. 155,898, filed Dec. 20, 1926.

Composite piezoelectric torsion device, Serial No. 155,899, filed Dec. 20, 1926.

Internally clamped composite piezo-electrictorsion device, Serial No. 155,900, filed Dec. 20. 1926.

Orientation of component crystals in composite piezo-electric devices, Serial No. 155.902, filed Dec. 20, 1926.

Since the internal motional impedance of such devices is as high as any load that can be impressed thereon by a diaphragm, of the usual size, a relatively heavy and strong d1aphragm, such for example as a conical diaphragm of metal, may be utilized with its resulting advantages.

Under certain conditions, I may prefer to use a diaphragm having what I term a ridge pole apex, and this may be used particularly when it is desired to drive opposite sides of the diaphragm in opposite phase.

1 Under other condition, when it is desired to apply a simple push-pull motion to the apex of the diaphragm, I may use a cone having a single point apex.

Referring now more particularly to Fig. 1, 1 designates a cone of suitable material such as heavy paper, cardboard, wood, composition or metal, as previously pointed out,- adapted to be supported by suitable base 2 having an angular arm extending therefrom, and terminating in a crystal container 4. The base 2, arm 3, and crystal container 4, are preferably relatively heavy, whereby vibrations of the crystal device 6 mounted therein, will cause vibration of the cone rather than vibration of the base. The crystal container 4 is provided with a cavity 5 adapted to receive the crystal which may be cemented therein at the botom by means of suitable cement, such for example, as Rochelle salt melt comprising Rochelle salt from which the desired amount of water has. been removed by heating it at a temperature above its melting point, as described in the applications above referred to.

The cavity 5 in the crystal container, will preferably be made larger than the crystal so as to afford sufficient clearance to mount the crystal therein. The basal plane of the crystal may be secured to the bottom of the cavity 5 by the cement 5 and the remaining space may be packed with felt or similar material, if desired.

A suitable stress plate 9 of strong resilient material such as steel is secured to the top basal plane of the crystal as by cementing, bolting, or the like, and electrodes are applied 111 such manner that the application of electrical oscillations to the electrodes causes torsional vibration of the crystal device 6 The electrodes 7 and 8 may be arranged in any desired manner suitable for the purpose, for example, one electrode may be an internal electrode within the crystal, formed for example, by drilling through the crystal and cementing a conducting member in the hole so formed, while the other electrode may be an equatorial or belt electrode forming a loop about the crystal parallel to the basal planes, and may, for example consist of a coating of metal foil applied thereto, or a coating of graphite. Suitable leads are attached one to each electrode for connection to the source of power.

The stress plate 9 may be cemented or bolted to the diaphragm as shown in Figs. 1 and 3, in this instance forming what I may term a ridge pole diaphragm in which the apex mstead of being a point, consists of a line extending normally to the axis of symmetry. Application of electrical oscillations to the electrodes 7 and 8 causes vibration of the top of the crystal with reference to the bottom thereof, thereby tending to oscillate the stress plate, as shown by the arrows in Fig. 3, which, as will be seen, causes vibrations in opposite phase in the parts of the diaphragm on opposite sides of the axis of symmetry.

Referring now to Fig. 4, I have shown a modilied form which may be utilized when it is desired to use a diaphragm having a single point apex: in this instance, the stress plate 9 may be cut at an angle to form two driving edges 11 and 12, which may be cemented or bolted against the diaphragm.

Referring now to Fig. 5, I have shown an additional modification which may be utilized when it is desired to provide a diaphragm having a single point apex driven by a push-pull movement. In this instance, the crystal device may be mounted on one side of the axis of symmetry, and stress plate 9 may be fitted with a driving rod 14:, which is cemented or bolted to the apex 13 of the diaphragm.

While I have shown and described certain preferred embodiments of my invention, it will be understood that modifications and changes may be made without departing from the spirit and sco e thereof, as will be understood by those skilled in the art.

I claim:

1. A loud speaker, comprising a relatively large conical diaphragm, exposed on one side to unconfined air, and having its apex unsymmetrically disposed with reference to its periphery, and means for initiating Vibrations in said diaphragm in different phase relation at diflerent points thereof.

2. A loud speaker, comprising a relatively large conical diaphragm exposed on oneside to unconfined air and having its apex unsymmetrically disposed With reference to its periphery, and means for simultaneously initiating vibrations of said diaphragm mechanically out of phase simultaneously at a plurality of points symmetrically disposed with respect to said apex.

3. A loud speaker, comprising a relatively large conical diaphragm exposed on one side to unconfined air and having its apex unsymmetrically disposed with reference to its periphery, and means for initiating vibrations of said diaphragm mechanically out of phase simultaneously at a plurality of separated points on said diaphragm, symmetrically disposed on opposite sides of the axis of symmetry of said dia hragm.

Signed at New ork city, in the county of New York and State of New York, this tenth day of March A. D. 1927.

l ALEXANDER McLEAN NICOLSON.

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