US 3799286 A
A loudspeaker comprising a plurality of side panels disposed uprightly with their side edges facing, and post means between the facing side edges of adjacent panels, each post having a pair of elongated grooves for receiving a pair of panel edges to define a polygonal housing, no two sides of which are parallel to each other, each post further including an elongated portion defining a support for a grill cloth disposed about the girth of said housing and adapted to space said grill cloth apart from each panel of the housing. A plurality of substantially identical speakers are mounted in at least three of the panels, about one-fourth of the speakers facing forwardly of the loudspeaker and about three-fourths of the speakers facing generally rearwardly of the loudspeaker.
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Description (OCR text may contain errors)
United States Patent [1 Carroll [451 Mar. 26, 1974 LOUDSPEAKER  Inventor: James C. Carroll, PO. Box 5301,
Knoxville, Tenn. 37918  Filed: Dec. 20, 1972  Appl. No.: 316,822
Primary ExaminerStephen J. Tomsky [5 7] ABSTRACT A loudspeaker comprising a plurality of side panels disposed uprightly with their side edges facing, and post means between the facing side edges of adjacent panels, each post having a pair of elongated grooves for receiving a pair of panel edges to define a polygonal housing, no two sides of which are parallel to each other, each post further including an elongated portion defining a support for a grill cloth disposed about the girth of said housing and adapted to space said grill cloth apart from each panel of the housing. A plurality of substantially identical speakers are mounted in at least three of the panels, about one-fourth of the speakers facing forwardly of the loudspeaker and about three-fourths of the speakers facing generally rearwardly of the loudspeaker.
9 Claims, 4 Drawing Figures PATENTEDMARZES 1974 SHEET 1 OF 2 LOUDSPEAKER This invention relates to loudspeakers and particularly to the physical construction of such.
In the manufacture of loudspeakers, particularly those intended for use in home entertainment type applications, it is desirable that the loudspeaker provide optimum quality of sound yet be manufactured at a cost such that it can be sold at a relatively low price. This struggle for optimum sound at a low cost to the purchaser has existed in the art for many years. Among the factors involved in the struggle are those elements affecting the quality of the sound such as the number and kind of speakers, the geometry of the speakers and their cabinet, e. g. acoustical coupling, etc., and those elements affecting the structural quality, physical appearance and cost of the product such as its structural integrity when in use, the type and quality of materials of construction, the mode of construction and assembly, etc.
It is an object of this invention to provide a loudspeaker having novel construction. Other objects and advantages will appear from the following description including the drawings in which:
FIG. 1 is a front view, partly cutaway, of a loudspeaker including various features of the invention;
FIG. 2 is a rear view of the loudspeaker of FIG. 1;
FIG. 3 is a top view of the loudspeaker of FIG. 1 with the top cover removed;
FIG. 4 is a fragmentary representation, top view thereformofg cgrner of the loudspeaker of FIG. 3.
The loudspeaker of this disclosure includes a plurality of side panels, no two of which are parallel to each other, disposed in upright positions with the upright side edges of each panel disposed adjacent the upright side edges of adjacent panels. The facing side edges of adjacent panels are separated by an upright post having longitudinal grooves in two of its adjacent sides for receiving the side edges of the panels to define a hollow polygonal housing. One of the side panels serves as the front of the loudspeaker and the two panels most nearly diagonally opposite the front panel define the rear of the loudspeaker. A plurality of speakers is mounted in each of the two rear panels and in the front panel. The speakers are substantially identical and preferably about one-fourth of the total number of speakers are mounted in the front panel and three-eighths of the total number of speakers are mounted in each of the rear panels.
Each post of the housing includes an elongated portion that projects outwardly from the housing to define a support means for a grill cloth disposed about the girth of the housing. This support means maintains the grill cloth spaced apart from the housing so as not to develop shadowing of the speakers. Top and bottom covers close the housing.
No removable fastening means is employed in assembling the panels to their respective posts so that the elements of the loudspeaker do not loosen and induce undesirable baffle resonances when subjected to the vibration occurring during normal use. This is accomplished by employing a panel material which expands when wetted and wetting the side edge of the panel with adhesive prior to fitting it in its respective grooves in a post. The size and shape of each groove is chosen to be such that the groove will receive an adhesivebearing panel edge, but, as the panel expands, it presses against the sides of the groove with a force sufficient to maintain the panel and post together while the adhesive cures or dries, thereby developing a good bond between the panel edge and post.
With reference to the Figures, in one embodiment of the loudspeaker 10 there is provided a front panel 12, side panels 14 and 16, and rear panels 18 and 20. In the depicted embodiment, each of the five panels is of rectangular geometry and disposed in an upright position. The depicted panels are of substantially the same size and arranged with their vertical side edges 20 and 22 (panels 12 and 14, respectively, for example) in juxtaposition to the side edges of adjacent panels so as to define a hollow polygonal housing 23. The number, size and position of the several panels are chosen to insure that no two of the panels face each other on the inside of the housing so as to eliminate standing waves between the speakers and the inside housing walls disposed opposite the speakers.
Each of the panels is of a rigid material that resists warpage qnd provides rigidity to the housing. The material preferably is readily available at a relatively low cost. One suitable material is that known in the building trade as particle board. This material comprises wood particles, e. g., sawdust, pressed together and bonded with an adhesive and is of relatively low cost. It exhibits good strength and can be cut and worked using conventional woodworking techniques and equipment. Wood also can be used in the panels but is less desirable, principally because of its cost.
Upright posts 24, 26, 28, 30, and 32 are interposed between the juxtaposed side edges of adjacent panels of the housing 23. The depicted posts are each of rectangular, preferably square, cross-section and oriented such that two adjacent sides 34 and 36 thereof face the side edges 20 and 22 of the adjacent panels 12 and 14. Each of the sides 34 and 36 of each post is provided with an elongated groove 38 and 40, respectively. Each groove is of a size and shape adapted to receive a side edge of a panel and is oriented within the post such that the adjacent panels 12 and 14, fitting in the grooves 38 and 40, for example, define a selected angle A7 therebetween. In the depicted loudspeaker comprising five panels, this angle A7 is substantially 108 degrees.
As shown in the figures, each post is oriented with re spect to the housing 23 so that one corner edge of the post 24 is disposed outwardly of the housing to define a substantially vertical elongated portion 42 projecting from the housing to define a support for a grill cloth 44 that encircles the girth of thehousing 23. Notably, such corner elongated portion 420i each of the five posts in the depicted embodiment projects outwardly from the housing by a distance sufficient to ensure that such elongated portions hold the grill cloth spaced apart from the panels sufficiently to permit the mounting of one or more speakers in a panel without the speaker being in contact with the grill cloth. In this manner, the speaker is not shadowed on the grill cloth, a condition which detracts from the desired appearance of the loudspeaker and lowers its quality. In one suitable embodiment, the elongated portions 42 of the posts project from the housing by a distance sufficient to space the grill cloth 44 about seven-sixteenths inch from each panel. This distance has been found satisfactory to prevent shadowing of a speaker that is about one-eighth inch from the grill cloth at the closest point. In a preferred embodiment, the grill cloth begins and ends at that post 28 disposed between the rear panels 16 and 18 so that the ends 39 and 41 of the cloth may be hidden from view as by a covering strip 45 of L- shape cross section secured over the ends of the grill cloth and the post 28. In the preferred embodiment, each corner post comprises a common 1% inch by 1% inch, square cross section, length of wood, preferably hardwood. This material is readily available at a relatively low price. By reason of the manner of positioning of the post disclosed herein, such material is caused to serve multiple functions with a minimum of cutting or other working of the material as it comes from the supplier thereby minimizing the manufacturing cost of the present loudspeaker. Such lower cost does not sacrifice quality, but rather by means of the present techniques, the quality of the loudspeaker is improved, particularly its stability and durability in service and its physical appearance.
The housing 23 is assembled by joining the panels to the posts. Rigidityof the loudspeaker housing 23 has been found to be obtainable without the use of nails, screws or the like in joining the panels and posts. This is achieved by applying liquid adhesive to the upright side edges of the several panels, inserting the edges into their respective grooves in the posts, and clamping the assembly as by ring clamps about the girth of the housing. As the adhesive is absorbed by the particle board, the board expands. The sides 46 and 48 of the expanding panel edge bear against the sides 50 and 52 of the groove in which the panel edge resides and develops a pressure that ensures a good bond between the panel edge and the post. The clamping rings are retained about the assembly until such bonds are substantially completed, usually after only a few minutes. This assembly procedure is simple, inexpensive and produces joints that are superior in strength and rigidity to joints obtained by conventional methods. The procedure further provides for rapid assembly thereby helping to produce the loudspeaker at a low cost. Several adhesives provide the desired bond between the panels and posts. Casein base adhesives have been found particularly suitable.
Top and bottom covers 72 and 74, respectively, are
provided to close the ends of the housing 23. These covers preferably seal the ends of the housing so that the housing is substantially air tight" thereby provid-.
ing for the establishment of acoustical coupling of the several speakers interiorly of the housing and accompanying enhancement of their collective output.
Quality sound from the loudspeaker is obtained through the use of multiple, substantially identical, speakers 54 mounted in the panels l2, l6 and 18. The preferred speaker includes a mounting rim 56 and is inserted in an appropriately sized opening 58 in the panel 12, for example. The speaker 54 is inserted into its opening 58 from the outside of the housing 23 so that the rim 56 butts against the panel 12 when the s eaker is fully inserted. Each speaker is secured to its panel as by screws 60. This procedure causes the speaker to fill the opening 58 in the panel and positions the speaker face 62 outwardly of the plane of the panel so that there is no unfilled portion of the opening of the panel that will develop a shadow on the grill cloth. This construction feature of the disclosed loudspeaker is in large part made possible by the fact that the grill cloth is spaced apart from the panel, hence apart from the speaker, as referred to above. The cone (FIG. 1) of each speaker faces outwardly of the housing.
In a preferred embodiment, each loudspeaker includes sixteen individual speakers 54 each of which is substantially identical to the other speakers in the system. Preferably, four of the speakers are mounted in that panel 12 of the housing which faces a listener and defines the front of the loudspeaker. These four speakers develop about one-fourth of the total sound energy output of the loudspeaker so that about one-fourth of the sound energy is radiated from the front of the loudspeaker. Each of the two panels 16 and 18 most nearly diagonally opposite the front panel 12 are each provided with six speakers so that about three-fourths of the total sound energy from the loudspeaker system is radiated from the rear of the loudspeaker.
For obtaining stereophonic listening effect, the present loudspeakers are employed as a pair, that is, two of the present loudspeakers are disposed within a room and spaced apart from each other by a distance of about six feet with their fronts facing in the same direction and with their rear panels generally facing a wall of the room within which the speakers are located. The loudspeakers are spaced apart from the wall by about 12 18 inches. The pair of speakers thus employs a total of 32 individual speakers, each of which is substantially identical to each other speaker to provide stereophonic listening. This combination of 32 speakers disposed in two separated loud-speakers, each of which contains 16 speakers and having the indicated ratio of forward to rearward radiated sound energy, in rooms of less than about 500 square feet floor area, has been found to provide sound emanating from the speakers which substantially completely fills the room. The result is that the sound appears to be coming from all points of the room. This effect has been particularly evident in rooms of about 200 square feet which appears to be a common room size in a home entertainment center.
Contrary to the prior art teaching that 87 percent of the sound energy received by a listener in the concert hall should be received as reflected or deflected sound energy and that the remainder of the sound energy should be received directly by the listener, the present inventor has found that these concepts are not applicable to home entertainment listening, in part because of the very large number of absorptive surfaces in a home as compared to a concert hall, and in part because of the appreciably greater size of a concert hall as compared with the common home entertainment center. In the latter, there is considerably less volume to be permeated by the sound emanating from the loudspeakers and there is more opportunity for deflecting, reflecting and/or absorbing of the sound by reason of the more closely spaced walls, ceiling, floor, and soundabsorbing objects within the room containing the loudspeakers. It has been noted that in such home entertainment environments, it is common to obtain dead spots" which appear to be the result of improper distribution of the sound energy from the loudspeakers from which the music or other sounds emanate. In accordance with the present invention, an especially large number of identically sized speakers has been found to produce a like large num ber of points of origin for the sound, each of the origins being of the same properties (that is, having the same energy output) and being directed against various reflective surfaces within the room with the result that the listener obtains a substantially uniform quality and density of sound at substantially any point within the room. This effect has been found to be obtained with the 32 speakers found in a pair of loudspeakers each of which has 16 speakers as referred to above. If less than about percent of the sound energy is radiated from the front of the loudspeaker to the listening area, there is an overriding proportion of the reflected sound energy reaching the listener and he experiences a distorted sound which may take the form of an unrealistic reproduction of the sound produced by the loudspeaker. Greater percentages of sound radiated from the front of the loudspeaker also produce a distorted version of the reproduced sound but of an opposite character. For exam ple, greater than about percent forwardly radiated sound will result in unnatural sound dispersion in the room. A like problem exists when an excessive portion of the sound energy is radiated from the rear of the loudspeaker. In addition, the surfaces in a home entertainment center possess widely varying sound absorption characteristics. The disclosed loudspeaker has been found to provide that distribution of sound energy output which tends to overcome the loss of portions of the sound energy due to varying degrees of sound absorption by surfaces in the room.
The use of a plurality of substantially identical speakers within a single housing increases the probability of acoustical coupling between two or more of the speakers and reduces the amplitude of undesirable sound resonances in the free air response of the drivers. This potential problem is eliminated in the disclosed loudspeaker by the use of nonparallel side panels as referred to above. Accordingly, in the present speaker, the number and size of the panels used in the multisided housing are chosen to preclude the speakers mounted in one panel from being oriented directly opposite and in alignment with one or more of the other speakers. As noted, this is accomplished through the use of an uneven number of equally sized panels, five such panels being a preferred number. Fewer or more panels increase the difficulty and cost of assembly and- /or establishment of the desired spacing of the grill cloth from the panels in the manner disclosed hereinbefore.
As desired, the polygonal housing may be filled with an acoustically absorbing material that will eliminate the interaction among the individual speakers at frequencies above a few hundred Hertz.
lt is noted that through the use of the disclosed techniques for bonding the panels to the posts, there is a substantial larger area of glued surface at each corner. This is in contrast to the glued mitered joints employed heretofore.
While a preferred embodiment has been shown and described, it will be understood that there is no intent to limit the invention by such disclosure, but rather, it is intended to cover all modifications and alternate constructions falling within the spirit and scope of the invention as defined in the appended claims.
What is claimed is:
l. A loudspeaker adapted to mount a plurality of speakers within a single enclosure comprising five side panels disposed in an upstanding position,
with the vertical side edges of each panel disposed contiguous to the vertical side edges of adjacent panels to define a hollow polygonal housing having no two upright sides thereof parallel to each other,
a plurality of elongated post means, each disposed between contiguous side edges of adjacent panels, means defining an elongated slot extending along each of the adjacent sides of each of said post means, each of said contiguous side edges of said adjacent panels on opposite sides of each of said post means being received in one of said slot means, each of said post means including an elongated portion projecting outwardly from said housing to define a support means for grill cloth means,
grill cloth means disposed about the periphery of said housing in contact with said support means of each post means whereby said grill cloth is held spaced apart from said side panels, and
top and bottom closure means disposed on opposite ends of said housing.
2. The loudspeaker of claim 1 and including a plurality of substantially identical speakers, about one-fourth of-which are mounted in a panel facing a listener and defining the front of said loudspeaker, and about threeeighths are mounted in each of those two panels most nearly diagonally opposite said front panel whereby said speakers in said rear panels are directed away from a listener.
3. The loudspeaker of claim 2 wherein said grill cloth begins and ends at that post disposed between the adjacent side edges of the two most rearward panels which serve as mounting means for those speakers directed rearwardly of said loudspeaker.
4. The loudspeaker of claim 3 and including an elongated strip of generally L-shaped cross section disposed over the ends of said grill cloth.
5. The loudspeaker of claim 1 wherein said panels defining said polygonal housing are of substantially the same size.
6. The loudspeaker of claim 1 wherein said post means are substantially identical to each other and each possesses a substantially square cross section, one elongated corner of which projects outwardly from said housing.
7. The loudspeaker of claim 1 and including adhesive means disposed along each of the side edges of said panels and adapted to bond said panels to said post means.
8. The loudspeaker of claim 7 wherein each of said panels comprises particle board which expands when said adhesive is applied thereto.
9. in a loudspeaker of the type particularly useful in home entertainment centers and adapted to house a plurality of speakers, a majority of which are positioned to direct their sound energy along indirect paths to a listener and less than a majority of which are positioned to direct their sound energy along direct paths to said listener, the improvement comprising a plurality of side panels disposed in upstanding position, with the vertical side edges of each panel disposed contiguous to the vertical side edges of adjacent panels to define a hollow polygonal housing having no two upright sides thereof parallel to each other and providing means for mounting said speakers such that no speaker has opposite its mounting panel another parallel plane to establish standing waves,
a plurality of elongated post means, each disposed between contiguous side edges of adjacent panels,
grill cloth means disposed about the periphery of said housing in contact with said support means of each post means whereby said grill cloth is held spaced apart from said side panels and out of contact with said speakers, and,
top and bottom closure means disposed on opposite ends of said housing.