US1704354A - Acoustic device - Google Patents

Description

;March 5, 1929. I R WEGEL I 1,704,354

ACOUSTIC DEVICE Filed April 30, 1923 2 Sheets-Sheet l Awe/77W":- 20 1770 A li zyal March 5, 1929. wEGEL 1,704,354

ACOUSTIC DEVICE Filed April 50, 192-3 2 Sheets-Sheet 2 Patented Mar. 5, 1929 UNITED STATES PATENT OFFICE.

'mmonn L. WEGEL, or "mzwxonmn. Y., assmnon 'ro was rnim Enacrmc conrm, mconronarnn, or NEW YORK, N. in; a coarona'rrox or NEW YORK.

ACOUSTIC nEvIon Application filed s in so, 192:; Serial m. 5,407.1 '7

This invention relates toracoustic appara-v tus, the object bein to device capable of aith ully and efliciently roducing sound vibrations within the audilerange.

In accordance with the general features of the invention, there is provided an improvedform of diaphragnrand mounting whereby the system may have symmetrical modes of vibration, sensibly such that if the lowest mode gives sharpreson ance, it will be well below the yoice range, or if 1t givesbroad pedance of the driving element to that of the diaphragm whereby. the vibrations may be efliciently and faithfully transmitted.

- In \,one .of its embodiments, the invention provides an acoustic device wherein a conical diaphragm having such dimensions, stifi'ness,

and weight of material that when supported by a pluralityof light flexible members sub-* stantially radially from a support coaxial with the dlaphragm, its fundamental mode, if prominent, is enough below the voice range to prevent hollow or tubby quality of voice reproduction, but is not so low as to be below the lowest frequency of themusical range.

Another feature of the invention is the connection of the actuating device or driving member tdthe, diaphragm or driven member by a lever system having the proper ratio to equalize. the mechanical impedance of, the

driving and driven members.

It is a well knownfact that notes low in the musical shale 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 producing them. However, more pleasing effects may be obtained ifthe lower notes'can be produced more distinctly. The horns usually employed in connection with'talking machine andloud speak- .ing receivers are inefficient transformers of acoustic vibrations at the frequencies for which theear is less .sensitive. In many,

cases, therefore, the low notes appear to be entirely eliminated. It has been found that large diaphragms, when properly designed,

rovidean acoustic A "actuating d -of vibration below the voice range,

reproduce the lower notes very efficiently,

Other thin s being/equal, the larger the dia-- phragm 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. Inthis respect diaphragms are quantitatively analogous to open and closed pipes. In accordance with the invention a diaphragm preferably conical in form to permit the use of light materials and obtain the proper amount of stifl'- tages of a freediaphragm and'has a further arrangement possesses certaln of the advanadvantage of added stiffness whereby the cir- 1 cular symmetry of the diaphragm is maintained while vibrating The invention atlgso provides for matching the impedance of v evice;to that of the diaphragm whereby the fnost eflicient transformation of energy isob-tained.

A loud speaki g receiver of the type herein described has preferably a fundamental mode 1 that is, between 30 and 7 0 cycles per second, but hot below the lowest vibration in the musical rangewhich is about 16 cycles per second. Such a device wiyll faithfully, 'Tanduniformly transmit. vibratlons throughout the voice range and will amplify the lowfrequency vibrations in the musical scale to the extent that they will have the proper relative sound vibrations.

n accordance with another feature a loud speaking receiver is provided in which a loud-speaking unit comprisin a large conical intensity with respect to the higher frequency diaphragm, its mounting an the actuating member are supported'on a sounding board, or a secondary diaphragm, constituting the rear wall of a cabinetfthe front-wall of whichv is apertured to freely receive the diaphragm I and whereln are provlded one .or more resonantchambers for emphasizing vibrations bf any-desired frequencies.

fIn the drawinggFig. 1 is a sectional view of a loud speaking receiver embodying the im I vention Fig. 2 is a rear view of the device shown in F1 1, showin the su ortin means for.

g g PP g the diaphragm;

' Fig. 3 is an enlarged detail view of the diaphragm' and the supporting means Fig. 4 is a cross sectional view of one fornr of actuating means that may be used;

.Fig. 5 shows in cross section a modification of the diaphragm supporting means;

Fig. 6 is a rear view of the'deviceshown in I avith the actuating device 12 by. means of a rod 25. The diaphragm supporting members 14 are preferably of a light flexible material such as rattan, or aluminum, and may be attached in any suitable manner to a collar 26, adjustably secured to the horizontal'member 11 by means of screws 17 Preferably, the collar 26 is adjusted so that there will be no tension exerted on the diaphragm 13 by the rod 25. The diaphragm 13 is preferably made of a light elastic material such as paper, and is provided with a reinforcing annulus 18 at its periphery to s tifi'en it andmaintain its symmetry while vibrating. The annulus 18 also forms a suitable means to which the supporting members 14 may be cemented or otherwise attached.

The actuating device 12 may be of any well known type of receiver magnet system, but it is preferable to use one of the type described in Patent No. 1,365,898 of January 18, 1921, to H. G. Egerton, modified as shown in Fig. 4, wherein the armature 15 is connected to the diaphragm 13thr0ugh a lever system cdmprising an intermediate lever 19,

preferably a reed type lever, one end-of which is connected to the armature 15 by means of rod 16, and the other end ofwhich may be supported-on the pole piece 8 in any suitable manner. The rod 25 connects the diaphragm 1.3 to a point intermediate the ends of the lever 19. By providing the proper ratio of lever arms the mechanical impedance of the actuating device may-be matched to that of the diaphragm thereby providing the most efficient arrangement for transforming the energy delivered to the armature .15 into sound vibrations. I

A diaphragm having a diameter of about 18 inches coupled to the receiver system heregives excellent resuts...

in described through a lever system having a reduction ratio of a proximately two to one However, in. any

case the proper ratio will depend uponthe characteristics, including the dimensions, of v cured which in turn are carried by the collar 26. I

, A receiver of the character shown in Fig,

1 or Fig. -5 may be mounted in a cabinet as- I shown. in Figs. 8 and 9 and supported therein on a sounding board, or diaphragm, 22 which may constitute the rear wall of the cabinet. The sounding board 22 is preferably made of wood and so designed as to have a lower frequency of freevibration than that of the diaphragm 13. The front wall 21 is provided with an opening slight-1y larger than the diaphragm 13 and the space between the edge of the diaphragm 13 and the edge of the opening is closed by an annular membrane 23 which should be formed of a very light material such as will offer no resistance to the movements of the diaphragm 13. In the cabinet there may be provided one or more resonant chambers 28. The sounding board 22 and the resonant chambers 28 are preferably designed so as to be resonant for vibrations of such frequencies as it may be desirous to emphasize.

Although the invention has been described in connection with a loud speaking receiver, obviously it may be readily adapted to a transmitter, or a phonograph reproducer by substituting means -well known in the art for the actuating device described.

'The invention claimed is:

1. An acoustic device, comprising a conical diaphragm, and a resilient means peripherally supporting said diaphragm, said means extending substantially radially from the axis of said diaphragm.

2. An acoustic device, comprising a conical diaphragm having a low natural period, and means for peripherally supporting said diaphragm whereby it ma vibrate substantially in accordance with its ree mode of vibration, said means comprising a plurality of resilient members.

3. An acoustic device comprising a. conical diaphragm and resilient means supporting I,

prising a plurality of members extending substantially radially inward from the periphery of said diaphragm.

t. An acoustic device, comprising a conical diaphragm having a definite impedance, an actuating device having a diflerent impedance, means comprising a system of levers for connecting said actuating device to said 'diaphragm and matching their impedanees and resilient radially extending means for supporting said diaphragm. v i

5. An acoustic device comprising a conical diaphragm having a fundamental mode of vibration below the voice range and Within the musical range, and resilient means peripherally supporting said diaphragm at intervals, said means extending radially inward from the periphery of said diaphragm.

6. An acoustic device comprising a large direct-acting diaphragm, a support substantially concentric with said diaphragm, and of less diameter than said diaphragm, and resilient supporting means connecting the diaphragm with said support.

T. An acoustic device comprising a large direct-acting diaphragm, means for actuating said diaphragmin accordance with sound, a base member, a collar support mounted on said base member, said collar being substantially concentric with and of smaller diameter than said diaphragm, resilient supporting means connecting the edge portion of the diaphragm with said collar, and means for supporting said actuating means from said base member.

8. In a sound reproducer i a large directacting diaphragm of light exible material,

I J a central support, an actuatin device mounted on said support and operatively coupled to said diaphragm to actuate the same in accordance with sounds, and diaphragm-supporting means also attached to said support and to said diaphragm at a distance from the point of attachment of said actuating device to the diaphragm, the connection through said support from the portion of the diaphragm attached to the supporting means to the point of attachment of the diaphragm to said actuating device being flexible to permit the said portion and said point of the diaphragm to be readily shifted with respect to each other.

9. A loud speaker comprising a large direct-acting diaphragm formed to possess inherent stifl'ness in the direction of axial movement, a central mounting, means secured thereto for vibrating said diaphragm in accordance with sounds to be produced, and flexible supporting means attached to the diaphragm at its peripheral portion and extending inwardly to said mounting for maintaining the circular symmetry of said diaphragm while permitting free vibration of its peripheral portion. k

10. An acoustic device comprising a vibratable member, driving means therefor at tached to said member, a flexible support for said member rigidly attached theretoand extending inwardly from the edge of said mem her and an apertured member for holding said support and said driving means.

In witness whereof,I hereunto subscribe my name this 28th day of April A. D; 1923.

- RAYMONP L., WEGEL.

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