US3132712A

US3132712A - Loud-speaker enclosure

Info

Publication number: US3132712A
Application number: US212A
Authority: US
Inventors: Wilbur L Maddy
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-01-04
Filing date: 1960-01-04
Publication date: 1964-05-12
Anticipated expiration: 1981-05-12

Description

May 12, 1964 MADDY 3,132,712

LOUD-SPEAKER ENCLOSURE Filed Jan. 4, 1960 RP PS INVENTOR. W/YbUr L. Maddy Z: T 4 ATTORNE rs.

electrical signals. have resulted in more and more expensive, complex and space-consuming apparatuses. many skilled in the high fidelity sound field that satis- United States Patent M 3,132,712 LOUD-SPEAKER ENCLOSURE Wilbur L. Maddy, 2051 Central Park, Apt. 2,

Topeka, Kans. Filed Jan. 4, 1960, Ser. No. 212 4 Claims. (Cl. 181-31) This invention relates generally to the field of sound transducer equipment and, more particularly, to improvements in enclosureapparatus for loud-speakers such as are utilized for the reproduction of music, speechor other audio intelligence in homes, stores and other surroundings.

The increasing interest in recent years in the high fidelity reproduction of sound has focused attention upon the sound reproducing portion of high fidelity systems, since it has been recognized that, regardless of the degree of perfection attained in the handling of audio frequency electrical signals, the final usable output, that is, the reproduced sound itself, is limited in its quality by the operation of the sound transducing portion of the system. The prior art has sought many solutions to the problem of attaining high quality sound reproduction of audio In the main, however, these efiorts It is currently felt by believed that such large speaker mustbe supplemented by one or more additional loud-speakers or tweeters to handle certain higher frequency parts of the range of sounds to be reproduced. More recently, the problem has been further compounded by the necessity of providing a pair mental to the obtaining and enjoyment of high quality systerms by the average householder.

Accordingly, it is the primary object of this invention to provide sound reproducing apparatus of an improved type adapted to give quality reproduction performance at moderate cost and with a minimum of complexity and consumption of space.

It has been found that loud-speakers of even the smaller sizes, such as eight inch cone diameter will, without supplementation by additional speakers or tweeters, give extremely realistic and pleasing sound reproduction per formance when enclosed by means such as contemplated by the present invention, which advantageously is also relatively small in size and inexpensive to manufacture.

It is, therefore, a further object of the invention to provide enclosure apparatus for use with conventional loud-speakers of any size, but particularly adapted for improving the overall performance which may be obtained from loud-speakers of the smaller sizes now seldom considered even usable for overall frequency reproduction in high fidelity systems.

It is a further important object of the invention to provide such enclosure apparatus which will be of greatly decreased volume, as compared with any of the nowconventional types of high fidelity loud-speaker enclosures.

It is a further object of the invention to provide such enclosure apparatus which may be constructed of various .materials including, preferably, a wooden cabinet, but

also including cabinet structures of metal, plastic or the like, without the disadvantageous effects of vibrations,

resonances and the like which are suffered in conventional 3,132,712 Patented May 12, 1964 ice types of speaker enclosure apparatuses when materials of the latter types are employed.

Itis another of thevery important objects of the invention to provide and utilize in association with the cabinet structure of the enclosure, an improved type of acoustical filter disposed within the cabinet structure in such relation to the latter and to the rear of the cone of the loudspeaker as to automatically adapt to the dynamiodiaphragm action of the speaker cone and the levels of fre quency and amplitude of sounds being transduced in such manner as to improve the reproduction qualities which would otherwise be enjoyed from the speaker employed to such an extent .that an eight inch speaker of moderate cost, for example, will give results comparable to, if not better than, loud-speakers of almosttwice that size and several times that cost housed in ordinary enclosures.

It is another object of the invention to provide such enclosure apparatus for loud-speakers, which. is dimerisioned in accordancewith certain critical ranges of proportions of the various dimensions, which cooperate with the improved acoustical filteremployed in the apparatus of the invention, in such manner that sound waves in duced in the air within the cabinet structure rearwardly of the cone of the loud-speaker by the dynamic diaphragm action of the latter, will be damped in amplitude and re tarded during both their rearward emanation from the speaker cone. and their forward reflection back to the latter by the cabinet structure in a manner affected by the frequency and amplitude of the particular sound waves being handled, so thatthe reflected rear waves are controlled to supplement by positive acoustical feedback of critically proper amount and phase the electrically induced original action of the speaker cone in producing a high quality and faithful'reproduction of the audioelectrical signals fed to the loud-speaker.

,for construction out of materials having hard Walls, its

adaptability for construction in attractive nonsymmetrically shaped cabinets and other features and details of side edge of a loud-speaker enclosure apparatus constructed in accordance with the invention;

FIG. 2 is a cross-sectional view of the apparatus of FIG. 1, taken looking rearwardly from immediately to the rear of the front-wall of the enclosure structure; as

illustrated by the line 22 of FIG. 3, the loud-speaker being removed to show the interior of the enclosure structure; and

FIG. 3 is a cross-sectional view of the apparatus of FIG. 1, taken looking downwardly from immediately be low the top wall of the enclosure structure, as illustrated by the line 3-3 in FIG. 2. q

It should be pointed out at the outset, that the natural qualities of sound reproduction, the sound propagation characteristics and the overall fidelity and performance which have been achieved by utilizing conventional loudspeakers of moderate size and conventional design in the 70.

improvedenclosure apparatus of this invention, have been of such surprising excellence, as compared either with the same loud-speaker enclosed in conventional enclosures or with even much larger and more expensive conventional or specially designed loud-speakers in large, expensive conventional enclosures of various types, that it is difficult to fully explain on a theoretical basis exactly why such startlingly improved results are achieved by the invention. Accordingly, at this time, no detailed theoretical explanation of the advantageous phenomena achieved will be attempted. However, current observations indicate that the performance characteristics of the invention mentioned probably depend upon certain critical ranges of the proportioning of the dimensions of the cabinet structure of the enclosure and/or the nature of the acoustical 'filter employed and its relationship to the cone of the loud-speaker and the inner surfaces of the walls of the cabinet structure.

wall 12 and generally parallel to the latter, and a top wall 16, a bottom wall 18 and a pair of

side walls

20 and 22 extending between the front and

rear walls

12 and 14 respectively and presenting a cabinet structure which is completely enclosed except for an opening 24 provided in the front wall 12. The

walls

12, 14, 16, 18, 2t) and 22 may be secured together in any suitable fashion and,

when the cabinet structure is formed of metal, plastic or the like, may include integral connections between certain of the walls. Where the cabinet structure of the apparatus lil is constructed of wood, any of the techniques known to the Wood cabinetry art, such as glue, screws or the like, will be satisfactory for assembling the walls tov gether, the important thing being that the cabinet structure is relatively rigid and relatively airtight, except for the opening 24.

With constructions of the cabine structure from other materials, means for the interconnection of the wall elements may be taken from those which are conventional and known by persons skilled in the art of constructing objects from such materials.

The cabinet structure presented by the

walls

12, 14, 16, 18, 20 and 22 present a housing for enclosing and mounting a loud-speaker generally designated 26 whose frame 28 may be secured to the front wall by any conventional fastening means such as at 30. The speaker 26 also includes a magnet or coil portion as at 32 adapted for electrical connection with a source of audio frequency electrical signals and a cone 34 adapted to be vibrated by the action of such electrical signals upon the magnet or coil portion 32. It is to be understood that such speaker 26 may be of conventional design and could be, for example, either of the permanent magnet or dynamic type. The important consideration, or more accurately, privilege conceded by the invention in connection with the loud-speaker 26, is that it may be of relatively small size both in terms of the diameter of the cone 34 and the overall depth of the speaker assembly 26. Shallow loud-speakers of eight inch diameter have been found to produce superb results when utilized with the enclosure apparatus of this invention. The speaker 26 should be so positioned on the front wall 12 that the cone 34 aligns with the opening 24 in the front wall 12, it being understood that such opening 24 will be of size generally corresponding to the effective diameter of the cone 34. In order to protect the speaker cone 34 from the entry of foreign materials through the opening 24, as well as to improve the decorative qualities of the apparatus 10, a porous grill cloth as at 36 may be extended over the opening 24 and, if desired for decorative purposes, also extended over a portion or all of the front wall 12 and suitably fastened in any conventional manner, the illustrative embodiment being described showing the fastening of the grill cloth 36 by the sandwiching of opposite margins thereof between the front wall and the

corresponding side wall

20 or 22 as at 38.

The acoustical filter forming an important part of the inventive structure is generally designated by the numeral 40. Such filter 40 is preferably formed from a generally rectangular piece of material commonly known as rubberized horsehair padding material, which finds its heretofore usual application in the field of upholstering. Such material, which is used for the acoustical filter 40 in the preferred illustrative embodiment of the invention, is formed of a great number of random disposed, relatively stiff horsehair fibers which are individually coated, in

whole 'or in part, by a rubber or other elastic material, which also serves to interconnect the random disposed fibers at their zones of mutual contact. The material mentioned is available in sheets of various thicknesses from about one inch to about two inches in thickness. For enclosure apparatus 10, for accomodating an average size eight inch loud-speaker, the acoustical filter 40 may be preferably of about one and one-half inches thickness, while for the shallower size speakers of eight inch diameter or for larger speakers, a thickness of about two inches for the acoustical filter 40 is to be preferred.

The "acoustical filter 40 is bent forwardly on each side of a central portion 43 thereof, preferably into the generally arcuate configuration of a wall section of a cylinder and is disposed within the cabinet structure of the apparatus 10 so that a rearwardly convex central portion of the filter 40 is disposed along and in contact with an elongated central portion of the rear wall 14 as at 42. The opposite front surface of the acoustical filter 40 preferably extends forwardly into contact with the rear of the magnet or coil portion 32 of the speaker 26 as at 44. The

opposite side portions

46 and 48 of the acoustical filter 40 then bend arcuately forwardly and to the side and each extend into contact. with the inner surface of the cabinet structure in proximity to the corresponding of the

inner corners

50 and 52 presented by the juncture of the

side walls

20 and 22 respectively with the front Wall 12.

'The acoustical filter 40 thus divides the hollow interior of the cabinet structure of apparatus 10 into a chamber 54 forwardly of the filter 4t and in which the speaker 26 is received, and a pair of

rear chambers

56 and 58 between the rear of the filter 4t and the rear wall 14 on the opposite sides of the area of interengagement as at 42. The degree of arcuate bending of the filter 40 is, of course, controlled by the general proportions of the interior of the cabinet structure of the apparatus 10.

It has been found that the dimensioning of the walls 12 et seq. of the cabinet structure of apparatus v10, involve critical ranges of proportions, if the unexpectedly desirable results of the invention are to be fully achieved, which may be defined as including constructions in which the lateral dimension of the front wall 12 and side wall 14 running generally parallel to the elongated area of contact 42 between the filter 40 and the rear wall .14, is between about one hundred percent and one hundred twenty-five percent of the other or perpendicular, lateral dimension of such front wall 12 and rear wall 14 running perpendicularly to the elongated area ofcontact 42 and in which the dimension of the

side walls

20 and 22 and the

top walls

16 and 18 perpendicular to the aforesaid lateral dimensions of said front wall 12 and rear wall 14, i.e., the distance between front wall 12 and rear wall 14, is between about thirty percent and about fifty percent of the last-mentioned lateral dimension of the front wall 12 and rear wall 14. It may be observed that the enclosure apparatus 10 functionsequally Well whether disposed or oriented as illustrated in the drawing or turned upon its side; accordingly, the dimensions in question have thus been referred to as perpendicular lateral dimensions of the front and

rear walls

12 and 14 rather than height and width, which may be interchanged by different disposition of the apparatus 10. Satisfactory functioning of the apparatus has been achieved with various sizes of cabinet structures, and, of course, correspondingly dimensioned filters 40, when the proportions thereof have been chosen with-in the ranges just mentioned. It has been further observed, however, that a slight peaking or optimization of even such vastly improved results is enjoyed when the length, width and front to back depth of the cabinet structure are approximately in the ratio of 100:80z30 respectively, where the length is defined as the dimension generally parallel to the area of engagement 42 and width is defined as the dimension generally perpendicular to such area of engagement 42. One example of dimensioning of the cabinet structure of the apparatus which has been found very satisfactory in operation and capable of attaining the markedly improved results characterizing the invention, involved a height of sixteen and one-half inches, a width of twelve and one-half inches, and a depth of four and one-half inches where a conventional eight inch loudspeaker 26 was employed. Another illustrative example of dimensioning found to be satisfactory with a twelve inch loud-speaker was a height of eighteen and one-half inches, 21 width of fourteen and one-half inches and depth of six and one-half inches. It should be noted that all of the references to dimension and proportions thereof of the cabinet structure of enclosure apparatus 10 mentioned hereinabove and in the claims that follow, refer to theinner dimensions of the

Walls

12, 14, 15, 18, 20 and 22 which define the chamber within the enclosure structure 10.

Having thus described an illustrative, preferred embodiment of the invention, the principles and concepts involved will be clear. It necessarily follows that those skilled in the art may make a number of minor variations, modifications or adaptations of the apparatus differing in specific constructional detail from the preferred embodiment described without departing from the true spirit, principles and teachings of the invention. Accordingly, it is to be understood that the invention should be deemed as limited only by the scope of the claims that follow.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. Enclosure apparatus for a loud-speaker of the type provided with an open frame, an assembly on said frame for converting audio frequency electrical signals applied to said assembly into audio frequency mechanical vibrations of a part of said assembly, and a speaker diaphragm structtue having an outer portion thereof supported on said frame, an inner portion thereof coupled with said part for vibration with the latter and both generally forwardly facing and generally rearwardly facing areas thereof exposed, said apparatus comprising a housing having a front Wall provided with an aperture therein and wall means interconnecting said front wall to present a closed chamber Within said housing except for said aperture, said Wall means comprising a sound rellecting rear wall in spaced relationship to said front wall and sound refleeting side wall means interconnecting said front and rear Walls; means for mounting said frame of said loudspeaker on said housing to dispose said diaphragm structure within said chamber and in alignment with said aperture; and an acoustical filter having negligible damping and absorption effects on sound Waves propagated theret'hrough, said filter comprising a fibrous, sound pervious partition having a generally concave side and an opposite, generally convex side, said partition being of substantially uniform thickness and composed of random disposed, relatively stiff fibers at least partially coated and interconnected at zones of contact therebetween by a resilient binder substance, the partition being disposed within said chamber between said diaphragm structure and said rear wall and extending generally later-ally of said chamber with a central portion of said generally convex side engaged with said rear wall and the opposite, generally concave side of said portion engaged with said assembly.

2. Apparatus as set forth in claim 1, wherein said chamber is parallelepipedal and characterized by a dimensional relationship in which one lateral dimension thereof is between about 100% and about 125% of the other lateral dimension thereof, and the front-to-back dimension thereof is between about 30% and about of said other lateral dimension thereof.

3. Apparatus as set forth in claim 2, wherein said chamber is characterized by a dimensional relationship in which its length, width and front-.to-back depth are in the approximate ratio of :80:30 respectively.

4. Apparatus as set forth in claim 1, wherein said partition is composed of rubberized horsehair padding material.

References Cited in the file of this patent UNITED STATES PATENTS 1,844,802 Seabert Feb. 9, 1932 2,065,751 Scheldorf Dec. 29, 1936 2,775,309 Villchur Dec. 25, 1956 3,082,839 Whitcas Mar. 26, 1963 FOREIGN PATENTS 434,563 Great Britain Sept. 4, 1935 483,745 Great Britain Apr. 26, 1938 512,610 Great Britain Sept. 21, 1939 1,005,731 France Jan. 2, 1952 502,238 Italy Nov. 29, 1954 1,154,792 France Nov. 12, 1957

Claims

1. ENCLOSURE APPARATUS FOR A LOUD-SPEAKER OF THE TYPE PROVIDED WITH AN OPEN FRAME, AN ASSEMBLY ON SAID FRAME FOR CONVERTING AUDIO FREQUENCY ELECTRICAL SIGNALS APPLIED TO SAID ASSEMBLY INTO AUDIO FREQUENCY MECHANICAL VIBRATIONS OF A PART OF SAID ASSEMBLY, AND A SPEAKER DIAPHRAGM STRUCTURE HAVING AN OUTER PORTION THEREOF SUPPORTED ON SAID FRAME, AN INNER PORTION THEREOF COUPLED WITH SAID PART FOR VIBRATION WITH THE LATTER AND BOTH GENERALLY FORWARDLY FACING AND GENERALLY REARWARDLY FACING AREAS THEREOF EXPOSED, SAID APPARATUS COMPRISING A HOUSING HAVING A FRONT WALL PROVIDED WITH AN APERTURE THEREIN AND WALL MEANS INTERCONNECTING SAID FRONT WALL TO PRESENT A CLOSED CHAMBER WITHIN SAID HOUSING EXCEPT FOR SAID APERTURE, SAID WALL MEANS COMPRISING A SOUND REFLECTING REAR WALL IN SPACED RELATIONSHIP TO SAID FRONT WALL AND SOUND REFLECTING SIDE WALL MEANS INTERCONNECTING SAID FRONT AND REAR WALLS; MEANS FOR MOUNTING SAID FRAME OF SAID LOUDSPEAKER ON SAID HOUSING TO DISPOSE SAID DIAPHRAGM STRUCTURE WITHIN SAID CHAMBER AND IN ALIGNMENT WITH SAID APERTURE; AN ACOUSTICAL FILTER HAVING NEGLIGIBLE DAMPING AND ABSORPTION EFFECTS ON SOUND WAVES PROPAGATED THERETHROUGH, SAID FILTER COMPRISING A FIBROUS, SOUND PERVIOUS PARTITION HAVING A GENERALLY CONCAVE SIDE AND AN OPPOSITE, GENERALLY CONVEX SIDE, SAID PARTITION BEING OF SUBSTANTIALLY UNIFORM THICKNESS AND COMPOSED OF RANDOM DISPOSED, RELATIVELY STIFF FIBERS AT LEAST PARTIALLY COATED AND INTERCONNECTED AT ZONES OF CONTACT THEREBETWEEN BY A RESILIENT BINDER SUBSTANCE, THE PARTITION BEING DISPOSED WITHIN SAID CHAMBER BETWEEN SAID DIAPHRAGM STRUCTURE AND SAID REAR WALL AND EXTENDING GENERALLY LATERALLY OF SAID CHAMBER WITH A CENTRAL PORTION OF SAID GENERALLY CONVEX SIDE ENGAGED WITH SAID REAR WALL AND THE OPPOSITE, GENERALLY CONCAVE SIDE OF SAID PORTION ENGAGED WITH SAID ASSEMBLY.