US1501720A - Sound amplifier for phonographs - Google Patents

Description

H. L. PAGE SOUND AMPLIFIER FOR PHONOGRAPHS Filed Bed. 27. 1921 2 Sheets-Sheet 1 lizacw I .EZ06W5ZI i July 15 1924. g gg z H. L. PAGE SOUND AMPLIFIER FOR FHONOGRAPHS Filed Dec 27. 1921 2 Sheas-$heet 2 Fatented July 15,

UNITED; STATES PATENT OFFICE.

Application and December 27, 1921.

To all whom itmag; concern.

Be it known that I, Hownnn L. PAGE, a citizen of the Unied States, residing at Cl1i cage, in the county of Cook and State of Illinois, have invented a certainnew and useful Improvement in Sound Amplifiers for Phonographs, of which the following is a specification.

It is well understood in the phonographio that the vibrating diaphragm which delivers the sound waves to he received by the listening public and interpreted as sound is practically powerless in its operation unless some sort of an amplifying device is provided, in the older phonographic art, this device has been a plain horn, originally of sheet metal, more recently of wood. The theory on which these old amplifiers act is that the sound waves delivered by the diaphragm are reflectedforward and backward across the horn from its smaller to its larger end, until when they leave the horn and out into the room, they have set a sufficiently large volume of air into motion that the desired result is produced. It is well understood that as these diagonally reflected waves within the horn cross from side to side of the horn to produce this result, successive waves intersect each other with more or less distortion of the waves and a consequent blurring of the sound produced, so that it is frequently impossible, when standing-at the large end of the phonograph horn, to tell which of several similar words was actually deliveredby the diaphragm.

The object of this invention is to provide device for application 'and connection with,

a phonograph diaphragm, which will perform all the desired functions of the phonogra n horn of commerce and do away with all of its objections, thereby producing practically clear and readily understood sounds throughout the room into which the phonographic diaphragm is expected to del ver audible, pleasing sounds.

Broadly speaking, the invention consists in replacing the phonographic horn of commorce, operating in the manner described, with a egmcntal spherical resonator of such a material and such a shape that the sound was delivered by the phonograph diagm cause the walls of this sphere to viin perfect synchronism with the irsgm, thereby producingvn the room proper movements of SUfilClQDt volumes air to give to the listener clear and dis- Serial No. 524,893.

tinct sound reproductions of the actual movements of the phonograph diaphragm without the distortion and mixing of sounds which has heretofore taken place in devices of the prior'art.

The invention further consists in many special features and details of construction which will be hereafter more fully set forth in the specification and. claims.

Referring to the drawings, in which like numerals designate the same parts throughout the several views- Figure 1 is a sectional detail view of the complete mechanismillustrating this inven tion in its preferred form;

Figure 2 is a somewhat reduced, sectional view on the line 22 of Figure 1;

Figure 3 is a diagrammatic sectional view of the conventional phonograph horn of the old art here inserted for illustrative purposes, as referred to hereafter;

Figure 4 is a corresponding diagrammatic View of the device of this invention;

Figures 5 and 6 are sectiohal views of devices of the type of this invention, in which the vibrating spherical portions are not of proper curvature to produce the desired results, these figures being inserted for illustrative use hereafter;

Figure 7 is a sectional, detail view of a supplemental sound amplifying device ap plied to the device of Figures 1 and 2 of this invention; and

Figure 8 is an end view of the device of Figure 7 but on a reduced scale.

In the structure of Figure 1, the phonograph diaphragm 10 is shown enclosed within an annular ring 12 between two washers 14 and 16 and retained in place by a suitable screw threaded annular nut 18. The ring 12 is screw threaded on its outer surface so that it, and all the parts heretofore referred to carried by it, can travel horizontally along internal screw threads 20 on the inside of a cylindrical opening formed in the sort of a hub 22 on one side of the truncated sphere 24, more fully described hereafter. This ring 12 is detachably securable in adjusted position along the screw threads 20 by any conventional means, as for instance a set screw 26. By loosening this screw 26 and rotating the ring 12, the diaphragm 10 may be adjusted towards and from the center 3 of the truncated sphere 24.

The spherical chamber 24 is truncated or cut off on a plane 52- so located on the opposite side of the center 30 from the "diaphragm that a perforation 3% is formed in the sphere at this point, of substantially the same area as the vibrating portion of the diaphragm .10, this for reasons which will more clearly appear hereafter.

The spherical wall portion of the truncated portion 24: is made up of'any suitable vibrating material, in the particular case here illustrated and preferably, a series of contacting wooden segments 24, glued together along their respective lines of contact 36, as shown in the drawings. These segments are made of a suitable sort of wood and sufficient thinness so that when they are fastened together to form the segmental sphere 24, the finished segmental spherical surface will be an 'efiicient vibrating, spherical sounding board which will take up sound waves impressed upon it from the inside and deliver themto the outside room from the outside surface of the sphere.

The foregoing requirement is of great importance in this invention as the correct operation of the device depends upon 1mparting to the air particles in plane 32 a maximum motion and insuring that the pressure at this point be a minimum.

It is evident that as plane 32 and diaphragm 10 are both planes of maximum motion with reference to the center 30 of the sphere 24: that their successful coordination rests upon the maintenance of center 30 in a nodal relation. It is further evident that point 80 acting as a sound node would be a point of minimum motion at all times, and further that as the Walls 2 vibrated outwardly, point 30, would undergo a-minimum pressure while when the walls Z P were moving inwardly, point 30 would undergo a maximum pressure.

This maintaining of point 30 as a sound node while the diaphragm vibrates requires that the area ofboth the diaphragm 10 and that of aperture 34 shall bear a definite relation to the vibrating walls 24 and it is through the co-ordination produced by this relation that we secure the maximum vibration of walls 24".

For the purpose described, the phonograph diaphragm 10 when used as a reproducer is energized by conventional means not entering into this invention and therefore not shown, which delivers the necessary vibrations to the diaphragm by means of the conventional rod 38 connected to the center of the diaphragm.

In order that the truncated sphere shall produce the desired results of this invention, it is necessary that the sphere have its center, in the case shown in Figures 1 and 2 the center 30, at such a point with reference to the diaphragm 10 that when the sound waves delivered by the diaphragm 10 are projected into the truncated sphere 24, plane 32 shall become an "ntinode with reference to the center 80. It is to insure this operation of the device that the adjusting mechanism at the left hand end of Figure 1 is provided so that the operator may adjust the diaphragm backward and forward toward the center 30 of the sphere until this result, ontuning of the vice in which the relative area of the diaphragm 40 is too small to produce satisfactory results. In this case, the area of the diaphragm 40 is not sufficient to impart to the large volume of contained air the energy necessary to cause the walls 42 to vibrate in unison with all the sounds produced by the diaphra m 40. The desirable sounding board e ects of walls 42 are not developed'as their -area is relatively so great that the amplitude of their vibration is too small to produce satisfactory results. In Figure 6, the sphere is truncated on one side to make a large opening 52 where the diaphragm 54 is located and is truncated on the other side in a small opening 56. In this case the area of the diaphragm is greatly in excess of that indicated by aperture 56. This difference in area prohibits the maintenance of an antinode at aperture 58 as the sphere center 60 is no longer a node of minimum motion. The large diaphragm 54 tends to produce a node at some point nearer the aperture 56 than the point 60, say at point 58. It is evident that point 58 cannot maintain the same nodal relation with both of the points 62 and 64:, situated on the sounding board. cal sounding board does not satisfactorily vibrate and the device would not produce satisfactory results. Further, the shifting of the nodal center toward the aperture 56 results in a' large loss of sound energy through this aperture which is to be avoided as the device indicatedin Figure 1 is particularly designed to retain the maximum amount of sound energy inside the sphere in order to insure the greatest degree of vibration of the walls of the device. It will be noticed that in order to secure the best results from the device of 'Figure 1 that the walls 24? should be in the correct sound phase relation to the vibrating diaphragm 10. It is to secure this harmoni-= In this case, the spherious relation that the position of the diaphragm 10 is adjustable for if the repeated sound waves generated by the continual vibration of the diaphragm 10 should not reach the spherical sounding board 2-1 so as to re-enforce each the effect of the other, this condition will be rectified by moving the diaphragm 10 the fraction of a sound wave length either forward or backward. This cooperative relation is essential to cause the walls 24, to manifest their maXi-' mum vibratable qualities.

One of the features of the invention is to make the opening 3a of substantially the same size as the effective vibrating part of the diaphragm 10 so that when the de-' vice is used as a receiver for the purpose of making phonographic records, the voice of a person talking into the opening 34.- at a point, say 66, has a chance to travel, as shown in Figure 4, directly through the truncated sphere to the diaphragm 10, with all portions of the sound waves 72, which lie between the parallel lines 68 and 70, entirely unaffected by the walls of the sphere 24, only the extreme and unimportant ends 72 of such waves 72 coming in contact with the interior of the sphere. The result of this is practically perfect transmission of thevoice speaking at 66 to the diaphragm 10, something which is impossible in devices of the horn type, for as illustrated in Figure 3, a person talking into the horn 74 from the point 76 and toward the diaphragm 78, produces sound waves 80 which as they progress toward the diaphragm 78 are bent by the converging walls of the horn until at the time the waves strike the diaphragm they have the curved form 82 which, as is well understood in the art, fails to give the diaphragm the same sound which isproduced by the straight lines 80. The further bad result is obtained in devices of the prior art, by the fact that two adjacent curved waves 82 will, shown in Figure 3, strike the diaphragm 78 at the same time, producin sound confusion.

ln explanation it may be stated that the use of this truncated spherical resonator to obtain the desired results is made possible by the use of very must larger diaboard 84 of suitable material, preferably wood, and connecting the two spherical members together by two oppositely disposed, aligned radial posts 86 of suitable material, usually wood, performing exactly the same functions as the post which is found in the center of a violin for transferring sound waves. from the upper surface to the lower surface of the violin. In actual practice this supplemental device materially increases the sound delivering capacity of the mechanism as the vibrations of the Walls of member 24 are imparted without distortion to a member capable of affecting a larger surface of air.

For recording purposes, the device opcrates most satisfactorily when the diaphragmlO is of gold beater skin or other parchment like material, as is fully set forth and claimed in a companion application. For reproducing purposes the ordinary metal, mica or glass diaphragm is perfectly adaptable.

What I claim is:

1. 1h mechanism of the class described, a hollow sphere, of vibratable, sound transmittable material, cut away on one side to form an opening for a vibratable diaphragm, a vibratable diaphragm at said opening and means for shifting the dia phragm towards and from the sphere center, for the purposes set forth.

2, In mechanism of the class described, a truncated hollow sphere having openings of approximately equal size on opposite sides, a vibratable diaphragm mounted at one opening, and means for shifting the diaphragm toward and from the sphere center, for the purpose set forth.

In witness whereof, I have hereunto sub- HOWARD L. PAGE.

scribed my name.

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