US1763051A - Loud-speaker - Google Patents

Description

' June 10, M i-c. HOPKINS 1,763,051

LOUD SP EAKER Original File d Ja'nf5 1926 ESheets-Sheet 1 IlTTTIlllllll ll|lllllllllll1jll1l I IINVE T-Q' ATToRNEY Jun 10,11930.

M. c. HOPKINS LOUD SPEAKER Original Filed Jan. 5/1926 5 Shets-Sheet 2 ATTORN EY S June 10, 1930. M. c. HOPKINS mun SPEAKER 3 Sheets-Sheet 5 Original Filed Jan. 5, 1926 WWII:

. ATTORNEY Patented June 10, 1930 UNITED STATES PATENT OFFICE ms 0. HOPKINS, OF wASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOB TO HOP- KINS MBPOBATION, OF JERSEY CITY, NEW JERSEY, A CORPORATION 01' DELA- WAKE f LOUD-SPEAKEB Application fled January l, 1888, Serial Io. 79,889. Renewed December 24, 11m.

The present invention relates to loud speakers of the type disclosed in my nding application, Serial No. 77,033, file Dec. 22, 1921. The loud speaker disclosed in that ap lication .comprises a central relatively lig t'and stifi' tympanum, preferably conical in shape, and a surroundingexternal sound board or resonator having greater mass than that of the central diaphragm. The connection between the central t panum and the external resonator or soun boardis such that the central tympanum will respond to the relatively high frequencies and-will eflicientl reproduce the hi h tones or sounds,

and the relatively low requencies will be transmitted through said connection-to the sound board so that it will respond to the relatively low frequencies and W111 efficiently reproduce them. he principal object of this an invention is to provide a loud speaker of the foregoin t pe, the sound board of which is made of in sa wood.

It has been found that a loud speaker of the foregoing type produces superior results if the sound board be made of balsa wood.

Balsa wood seems to have the requisite properties to improve considerably the regenera-' tion of the relatively low frequencies which are passed on to the sound board for reproao duction. I am not prepared to state exactly what properties of balsa wood are responsible.

for the improved operation of the loud speaker disclosed in this application, but undoubt edly the'soft nature of this type of wood and 85 its extreme lightness are contributing factors. Several forms of loud speakers in which balsa wood may be advantageously employed are disclosed in the accompanying drawings, in which Fi 1 is a front view of a loud speaker especia ly designed for use in hotels, theatres, concert halls and similar places where a large volume of sound is desired; a

Fig. 2 is a side elevation of the speaker shown in Fig. 1;

Fig. 3 is a rear view of the loud speaker shown in Fig. 1;

Fig. 4 is a vertical section taken on the line 4-4 .of Fig. 3;

Fig. 5 is an enlarged detail vertical section of the central portion of the loud s aker showing the connection between the central tympanumand the external sound board;

' Fig. 6 is a front elevation of another type of loud s eaker operating on the same principle as t at shown in Fig. 1;

Fig. 7 is a top plan view of the loud speaker shown in Fig. 6;

Fig. 8 is a rear elevation shown in Fig. 6; v

Fig. 9 is a vertical section taken on the line 99 of Fig. 8.

Referring first to Figs. 1 to 5 inclusive, the loud speaker shown in these'figures comprises a central conical tympanum 1 coupled to a vibratory resonator or sound board 2 by means of a semi-flexible coupling, shown in Fig. 5. The conical tympanum 1 is preferably made ofcover paper out and folded to shape and glued along a radial seam. Near the outer edge of the cone thus formed the paper iscreased and then folded up to form a orwardly flaring brim 3 (Fig. 5,). This brim naturally assumes an angle to the plane ofth e base equal to the angle between the radial elements of the cone and that base. The outer edge portion of the brim 3 is preferably glued to the inner circular edge of the resonator or sound board 2. For this purose the inner circular edge of the sound oard is tapered as shown at 4 and the outer edge portion of the brim 3 seats upon and is glued to the tapering surface thus formed. In gluing or cementing the brim to the bev eled edge 4 it is important that a part of the brim be left free to form a hinge on which the cone may float. Thus with a brim wide the cemented portion may have a width of of an inch more or less and the remainder' of the brim may be left free to SWll'lg.

The resonator or sound board 2 in accordance with this invention is made of balsa wood. It can conveniently be made of 3-ply balsa wood as-shown in Fig. 5 with the grain of the inner ply running transverse to the grain of the two outer plles.

The vibratoryactuating force is applied to the apex of the conical tympanum by means of a rod or wire 5 which is adapted to be 100 of the speaker tympanum approximately 17 inches in out-.

side diameter and the reasonator or sound board approximately 4} feet in outside diameter. The relatively large size of the loud speaker shown in Figs. 1 to 5 inclusive makes it desirable to suspend it by cords or chains which may be attached to any suitable part of the loud speaker, preferably the s ider 8. The loud speaker may be suspended rom the ceiling of a room, a bracket or any other supporting device.

The loud speaker shown in Figs. 6 to 9 inclusive is very similar in construction to that above described as it comprises a conical tympanum 1', a. sounding board or resonator 2, a spider 8 for supporting. the casing 7 of the electromagnetic actuating mechanism,

and a forwardly flaring brim 3 on the cone which is attached to the inner edge of the sound board in the same manner as explained in connection with Figs. 1 to 5. The resonator or soundboard 2 of this form of the loud speaker is also made of balsa wood as in the case, of the loud speaker described above. The main difference between the speaker shown in Figs. 6 to 9 inclusive and that shown in the first five figures is that the sound board or resonator 2 is of smaller diameter than the-sound board shown in the first five figures. The conical tympanum 1- may or may not be smaller than the conical tympanum of the loud speaker of Figures 1 to 5. The reduction in overall size of the loud speaker shown in Figs. 6 to 9 inclusive makes it possible to support the speaker on a table or other horizontal surface and for this reason the sound board 2' is provided with suitable legs or cross pieces 10 glued or otherwise fastened to the sound board. The sound board may be provided with an opening 11 to provide a hand grip for moving the loud speaker from one place to another. In con.- structing a loud speaker of the type shown in Figs. 6 to 9 I have found that excellent results are obtained by making the cone 2 approximately 15 in diameter and the sound board approximately 22 in diameter. This makes the transverse width of the annular sound board approximately 3%" but good results may be obtained by making the sound board of even less width than this or of even greater width than the sound board shown in Figs. 1 to 5 inclusive.

In both types of speaker the 'central conimediate tones while the surrounding annular resonator or .-ound board efficiently reproduces the lower or bass notes. By reason of the fact that the sound. board is made of balsa woodthe reproduction of the lower or bass notes is considerably improved. The lower notes are not onl more accuratel reproduced but the tonal quality is conslderably improved, the reproduction being soft and mellow.

- In a loud speaker constructed in accordance with the foregoing description, the regenerated or reproduced sound waves are substantially directly proportional both quantitatively and qualitatively to the actuating force and the sound so reproduced retains substantially the same balanceof high and low tones as the'original sound from which the actuating force'was derived.

In the claims the term diaphragm is used to designate the entire vibratory body including the tympanum and the soundboard. y

I claim:

1. A loud speaker comprising a central I relatively light and stiff t mpanum, an external balsa wood sound board of reater mass than the diaphragm, and a flexible coupling between the two adapted to permit the central tympanum to respond to rela-- tively high frequencies and adapted to transmit the relatively low frequencies to the sound board.

2. A loud speaker comprising a central conical tympanum, an external balsa wood sound board of greatermass than the tympanum, and a flexible coupling between the two adapted to permit the conical tympanum to respond to relatively high frequencies and adapted to transmit the relatively low frequencies to the sound board.

3. A loud speaker comprisin a central conical tympanum, an external balsa wood sound board and a connection between the conical tympanum and the sound board adapted to permit the central tympanum to respond to'relatively high frequencies and adapted to transmit the relatively low frequencies to the sound board.

4. A loud speaker comprising a central conical tympanum, a balsa wood sound board extending radially beyond the conical tympanum and a connection between the conical tympanum and the wooden sound board adapted to permit the conical tympanum to respond to relatively high frequencies and adapted to transmit the relatively low frethe conical tympanum, said forwardly flan ing brim portion of the conical tympanuin. being attached to the sound board.

6. A loud speaker comprising a conical tympanum provided with a peripheral cerrugation forming a hinge portion and a balsa wood sound board ext-ending radially beyond the conical tympanum, said hinge portion being secured to said sound board.

7. A loud speaker comprising a balsa wood soundboard, and a conical tyn'ipanum flexibly connected thereto so that a portion of the sound board extends radially beyond the conical tympanum, the flexible connection between the conical tympanum and the sound board being adapted to permit the conical tympanum to respond to relatively high frequencies and being adapted to transmit the relatively low frequencies to the sound board;

8. A. loud speaker comprising a central conical tympanum made of paper, an external sound board made of balsa wood, and a lie:-

ible connection between the two adapted to' permit the conical tympanum to respond to relatively high frequencies and adapted to transmit the relatively low frequencies to the sound board'.

9. A loud speaker comprising a balsa wood sound board having a central opening a conical tympanum mounted in said opening actuating means for the conical tympanum and means for supporting said actuating means comprising a support attached to the sound board and spanning the central opening thereof.

10. A loud speaker comprising an annular flat balsa wood sound board having a circular central opening, a conical tympanum having a circular periphery, said conical tympanuin being mounted in said opening, and a flexible coupling between the conical tympanum and the sound board adapted to permit the conical tympanum to respond to relatively high frequencies and adapted to transmit relatively low "frequencies to the sound board.

11. A loud speaker comprising an annular balsa wood sound board having a central opening the edge portion of which is provided with a tapering seat, and a conical tympanum 'niounted in said opening, said tvmpanum having a forwardly flaring frusto-conical brim portion secured to the sound board on said tapering seat.

12. A loud speaker comprising a flat annu- 'lar sound board made of balsa wood, said sound board having a central opening the edge portion of which is provided with a tapering seat, and a fibrous conical tympanum mounted in said opening and having an integral forwardly projecting brim portion, a part of said brim portion being attached to the sound board a t said tapering seat.

13. A loud speaker comprising a .diaphragrn, and means for applying vibratory energy thereto the portion of said diaphragm where the energy applied being of relatively small mass and freely responshre to the higher ia'mpiencies, and said diaphragm havin other portion of greater mass formed oi. balsa wood which is freely responsive to the lower lrequencics.

14:. A loud speaker comprising a diaphragm having a. sound reproducing rim of bah-a vmod which is freely responsive to the lower frequencies and a portion of less mass within said rim. which is freely responsive to the higher frequencies and means for impressing vibratory energy on said portion Within the rim.

In testimony whereof I atfix my signature.

MARCUS C. HOPKINS.

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