US3430728A - Loudspeaker assembly with loudspeaker supported by vibratory diaphragm - Google Patents

Description

March 4, 1969 w. s. DUNNING 3,430728 LOUDSPEAKER ASSEMBLY WITH LOUDSPEAKER SUPPORTED BY VIBRATORY DIAPHRAGM Filed March 27. 1968 #Tryk/vifs.

United States Patent O 3,430,728 LOUDSPEAKER ASSEMBLY WITH LOUDSPEAKER SUPPORTED BY VIBRATORY DIAPHRAGM William S. Dunning, Bloomingdale, NJ.

(98--15 Horace Harding Blvd., Rego Park, N.Y. 11368) Filed Mar. 27, 1968, Ser. No. 716,616

U.S. Cl. 181-31 10 Claims Int. Cl. G10k 13/00; H04r 7/16 ABSTRACT F THE DISCLOSURE A loudspeaker assembly is disclosed having a loudspeaker peripherally supported by a vibratory diaphragm at the front of the loudspeaker cone. Behind the loudspeaker is a first, inner enclosure nested in a second, outer enclosure acoustically isolated from an outer cabinet. The enclosures have sound absorbing walls. A nonresonant board closes the inner enclosure. Sound waves developed at the rear of the loudspeaker cone are wholly absorbed in the enclosures.

This invention concerns a new and improved loudspeaker assembly. The invention involves improvements over those described in my prior U.S. Patent 3,275,100, issued Sept. 27, 1966.

In the prior patent I have described a loudspeaker assembly in which a loudspeaker is wholly supported by a vibratory sheet or diaphragm. In the present invention, I arrange the cabinet in which the loudspeaker is mounted in such a way that the rear of the loudspeaker is exposed to sound absorbent enclosures acoustically isolated from the cabinet. The assembly thus constitutes an infinite baille in a relatively small cabinet.

According to the invention a stretched canvas sheet supports the loudspeaker in a cabinet having rigid walls. Behind the canvas sheet is a rigid board having a floating mounting. The board is resiliently supported by fibrous pads defining two sound absorbing box-like enclosures in the cabinet. The two enclosures are separated by a dead air space. The rear of the loudspeaker cone radiates waves into an acoustically isolated chamber where the waves are wholly absorbed and suppressed. Waves generated at the front of the loudspeaker cone are free to radiate outwardly, reinforced by vibrations of the vibratory sheet which supports the loudspeaker.

Other objects and advantages of the invention will become apparent from the following detailed description taken together with the drawing, wherein:

FIG. l is a perspective view of a loudspeaker assembly embodying the invention.

FIG. 2 is a vertical enlarged central sectional view taken on line 2 2 of FIG. l.

FIG. 3 and FIG. 4 are vertical sectional views taken on lines 3*3 and 4 4 respectively of FIG. 2.

FIG. 5 is a fragmentary enlarged sectional view of a portion of FIG. 2, showing details of construction.

FIG. 6 is a perspective View of a spacer block.

Referring to the drawing, there is shown a loudspeaker assembly 10 including a generally rectangular five-sided cabinet 12, with a top wall 14, bottom 15, side walls 16, 17 and back wall 18. Lining the five walls are five thick pads 21-25 of compressed fibrous material defining a box-like sound absorbing enclosure 28. Nested within the enclosure 28 is a generally rectangular five-sided boxlike sound absorbing enclosure 30 formed by five flat thick rectangular pads 31-35 of compressed fibrous material. The pads 31-35 are spaced respectively from pads 21-25 by space 37. Four rigid corner spacer blocks 36 are provided at the four rear inside corners of enclosure 28 to receive and support the rear outside corners of en- Patented Mar. 4, 1969 closure 30. A resilient rectangular gasket 38 surrounds the outer sides of pads 31-34 at their front edge. The gasket is secured by glue or cement 39, 40 to the inner sides of pads 21-24 and outer sides of pads 31-34. A rectangular rigid board 42 is fitted just inside the front of the outer enclosure 28 and is secured by glue or cement 44 all around its rear periphery to the front side of gasket 38. The rear of the board is abutted to the front edges of pads 31-34. By the arrangement described, a chamber 45 is defined by closure 30 closed by board 42.

The pads 3134 terminate short of the open front of the cabinet. A resilient rectangular ring gasket 46 is secured by a suitable adhesive to the front edges 48 of all pads 31-34. Secured to the front face of this gasket is a rigid rectangular ring or frame 50. The ring is spaced from the side, top and bottom walls of the cabinet by another resilient ring gasket 51 cemented to both the insides of the walls 14-17 and t0 the outer periphery of ring 50. The ring 50 thus floats freely supported by the ring gaskets 46 and 51 at its periphery and at its rear side.

Secured to the ring 50 by a suitable cement or glue layer 52 is a vibratory diaphragm 54 made of a rectangular sheet of airtight canvas. The canvas sheet is stretched tight and flat. The sheet has a central hole 55. The sheet abuts a resilient spacer ring 56 which surrounds hole 55. The ring 56 is secured to cement or glue 58 to the front side of board 42. The front side of ring 56 is not attached to the sheet 54. Ring 56 is preferably made of a closed cell, foam plastic material such as polyurethane foam. The board 42 is made of wood or plastic.

Loudspeaker 60 is wholly supported by sheet 54. The loudspeaker has a frustoconical vibratory cone 62 formed with a peripheral flange 64 which abuts the rear side of the sheet 54 at the rim of hole 55. Spider frame 66 of the loudspeaker is integral with a ring flange y68 which abuts flange 64. A ring 70 abuts the front of the sheet S4 around hole 55. Rivets or bolts 72 extend through holes 73 in the flange and are secured in holes 74 in flange 68; see FIG. 5. At the rear of conical spider frame 66 is secured and supported a permanent magnet 75. A voice coil 76 is attached to the rear end of cone 62. To the coil are connected wires 78 which convey audio frequency signals to the coil. The cone 62 and frame 66 extend through a hole 80 at the center of board 42. By the arrangement described, the rear side of cone 62 is open to the chamber 45 and extends into the enclosure 30. Resilient ring 56 wh-olly surrounds the forward part of the cone at its outer or rear side. A space 81 is defined between board 42 and diaphragm 54 by ring 56 and by both rings 50 and gasket 51.

The loudspeaker as clearly shown in the drawing is wholly supported by the vibratory sheet 54. The inner or front side of the cone `62 is open to radiate sound waves will be directed forwardly in a relatively narrow conical field. The intermediate and low frequency waves will radiate in wider fields. The lowest frequency waves will impinge on the vibratory sheet 54 which will vibrate with and reinforce these low frequency waves to iniprove the bass response of the assembly.

Waves emitted at the rear of the loudspeaker cone will be absorbed inside the chamber 45 defined by enclosure 30. Those which strike board 42 inside chamber 45 will be reflected to pads 31-35 where they will be absorbed. Any waves which pass through pads 31-35 will be absorbed in the dead air space 37 or will be finally suppressed by pads 21-25 of enclosure 28. The system thus constitutes an infinite baille at the rear of the loudspeaker cone, since no waves emitted at the rear of the cone can come around to the front o-f the cabinet to interfere with or cancel waves emitted at the front of the cabinet. Board 42 floats on its resilient mounting and serves as a nonresonant, shield and reflector. Ring 56 cooperates with board 42 in Wholly suppressing waves tending to pass into space 81 between the sheet 54 and board 42. The sheet 54 can vibrate since it is supported in tension at its periphery and at the resilient ring 56.

The improved acoustic results obtained with the present invention depend on the complete acoustic isolation of the vibratory sheet 54 from the inner sound absorbing enclosures 28 and 30. Also, since the loudspeaker frame and magnet are wholly free from the cabinet, no vibrations can be transmitted to the walls of the cabinet which are thus acoustically isolated from both the loudspeaker and from the interior enclosure 30.

While I have illustrated and described the preferred embodiments of my invention, it is to be understood that I do not limit myself to the precise constructions herein disclosed and that various changes and modifications may be made within the scope of the invention as defined in t the appended claims.

What is claimed is:

1. A loudspeaker assembly comprising a magnetic loudspeaker having a rigid conical laterally apertured frame with an annular fiange at its wider end; a magnet secured to the apical end of the frame; a conical vibratory cone nested in the frame; electrically energized driving means carried by the magnet and operatively connected to the apical end of the cone to drive the same axially, said cone having a peripheral rim registering with and abutted to said flange; a diaphragm having an opening therein; means securing both the fiange of the frame and the rim of the cone to the edge of said opening in sealing relationship, so that the entire loudspeaker is supported only by the diaphragm and is free from all other external support; a rigid frame extending around the diaphragm at its rear outer margin, said rear margin of the diaphragm being secured to the frame; a rigid board disposed to the rear of and spaced from said diaphragm to permit free vibration of the diaphragm; a resilient spacer ring surrounding the loudspeaker and interposed between the board and diaphragm to define a space therebetween, said ring being located close to the loudspeaker to stop radially traveling waves emitted from the rear of the cone and to serve as a vibration damping means for the diaphragm in the area immediately around the cone; and sound absorbing enclosure means closed by said board, said board having a hole therein, said cone extending rearwardly through said hole in the board into said enclosure means, so that waves emitted by the rear side of the cone into said enclosure means are absorbed completely in the enclosure means and are prevented from reaching the front side ofthe cone.

2. A loudspeaker assembly as defined by claim 1, further comprising a box-like cabinet with open front; a resilient first gasket surrounding and secured to said rigid frame, said gasket being joined to the inside of the cabinet at its open front so that the diaphragm is stretched taut across the front of the cabinet and overlays the front of said resilient spacer ring, said sound absorbing enclosure means being disposed inside the cabinet, whereby both the diaphragm and the outside of the cabinet are isolated and separated mechanically and acoustically from the inside of said enclosure means.

3. A loudspeaker assembly as defined by claim 2, wherein said enclosure means comprises a box-like enclosure with sound absorbing walls formed of compressed fibrous material, said enclosure having an open front,

said board abutting and closing the open front of said enclosure.

4. A loudspeaker assembly as defined by claim 2, wherein said enclosure means comprises a first box-like enclosure having sound absorbing walls formed of sound absorbing fibrous material lining the inside of said cabinet, said enclosure means further comprising a second box-like enclosure having other sound absorbing walls formed to sound absorbing fibrous material, both of said enclosures having open front ends, said board closing the open front ends of both enclosures.

5. A loudspeaker assembly as defined by claim 4 further comprising spacer means interposed between the two box like enclosures and defining a dead air space therebetween said spacer means supporting the second enclosure inside the first enclosure.

5. A loudspeaker assembly as defined by claim 5, wherein said spacer means comprises a resilient second gasket surrounding the rear side of said board at its margin, said second gasket being secured to said margin of the board and between the first and second enclosures at their front ends so that the board is entirely resiliently supported and spaced from the inside of the cabinet at all points.

7. A loudspeaker assembly as defined by claim 1, wherein the vibratory diaphragm is a sheet to permit free vibration of the sheet in its area between said rigid frame and the resilient spacer ring.

8. A loudspeaker assembly as dened by claim 7, further comprising a resilient first gasket surrounding and secured to said rigid frame, said gasket being joined to the inside of the cabinet at its open front so that the diaphragm is stretched taut across the front of the cabinet and overlays the front of said resilient spacer ring, said sound absorbing enclosure means being disposed inside the cabinet, whereby both the diaphragm and the outside of the cabinet are'isolated and separated mechanically and acoustically from the inside of said enclosure means.

9*. A loudspeaker assembly as defined by claim 8, wherein said enclosure means comprises a first box-like enclosure having sound absorbing walls formed of sound absorbing fibrous material lining the inside of said cabinet, said enclosure means further comprising a second box-like enclosure having other of sound absorbing walls formed of sound absorbing fibrous material, both of said enclosures having open front ends, said board closing the open front ends of both enclosures.

10. A loudspeaker assembly as defined by claim 9, wherein the spacer means comprises a resilient second gasket surrounding the rear side of said board at its margin, said second gasket being secured to said margin of the board and between the rst and second enclosures at their front ends so that the board is entirely resiliently supported and spaced from the inside of the cabinet at all points.

References Cited UNITED STATES PATENTS 3,275,100 9/1966 Dunning 181-31 3,291,251 12/1966 Zemrowski 181-31 3,317,000 5/1967 Heidrich 181-31 STEPHEN J. TOMSKY, Primary Examiner.

U.S. Cl. X.R.

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