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Publication numberUS2915134 A
Publication typeGrant
Publication dateDec 1, 1959
Filing dateApr 29, 1958
Priority dateApr 29, 1958
Publication numberUS 2915134 A, US 2915134A, US-A-2915134, US2915134 A, US2915134A
InventorsBraund John J
Original AssigneeBraund John J
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Loudspeaker apparatus
US 2915134 A
Abstract  available in
Images(3)
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Claims  available in
Description  (OCR text may contain errors)

3 Sheets-Sheet 1 Filed April 29, 1958 INVENT OR. JOhnJ. Braund g F @W, L

A ffornc] J. J. BRAUND LOUDSPEAKER APPARATUS Dec. 1, 1959 Filed April 29, 1958 a v n m P J M Na 3 m V .w J g F )M,

6 4, 5 2 mm 3 I x z mix I m Wm M M w m M m M- J. J. BRAUND 2,915,134

LOUDSPEAKER APPARATUS 3 Sheets-Sheet 3 27 L"' I I I I I I I I l I I I I I g I I I 33 I I I I l I I l I I I I 3 II I I I I I I I I I I I l I I I I 2 I I I U 61:2:

Dec. 1, 1959 Filed April 29, 1958 Fig.

INVENT OR.

John JZBraund a. f L.

United States Patent LOUDSPEAKER APPARATUS 7 John J. Braund, Washington, D.C. Application April '29, 1958, Serial No. 731,808

12 Claims. (G1. 181-31) The present invention relates to loudspeaker apparatus. A primary object of the invention is to provide a highly compact and light-weight portable loudspeaker apparatus of highly economical construction which will modulate the emitted amplified sound vibrations to maintain the true pitch and natural reproduction of the original tones throughout the entire sound register audible to the ear. k k

A further object is to provide loudspeaker apparatus of the above-mentioned character embodying only one loudspeaker and associated sound reflecting or baffle means, wherein the apparatus produces sound with fideli't'y or tone quality equal to or closely approximating the sound; produced by very expensive multiple loudspeaker high fidelity sound producing systems presently available on the market. I

A further important object of the invention is to provide high fidelity loudspeaker apparatus of the abovementioned character, including a novel system of sound reflectors or baffles which are adjustable with fidelity for emphasizing the desired range of tones, or to accominodate the acoustical characteristics of 'a particular loudspeaker employed in the apparatus or the acoustical characteristics of a room in which the apparatus is being used.

A further object is to provide loudspeaker apparatus embodying a single loudspeaker of the broad range type, together with a novel system of sound reflectors or baflles, constructed and arranged to bring out and emphasi'z'ethe extremely lowfrequency and high frequency ranges of the entire audible sound register, as well as the intermediate range or frequencies of the sound register.

Other objects and advantages of the invention will become apparent during the course of the following descri tion.

In the accompanying drawings, forming a part of this application, and in which like numerals are employed to designate like parts throughout the same,

Figure 1 is a front perspective view of a loudspeaker apparatus embodying the invention.

Figure 2"is a similar perspective view of the apparatus with the ornamental cloth grille and grille retainer frame removed.

Figure 3 is a rear side elevation of the apparatus on an enlargedscale and with the rear panel of the sound cabinet or chamber removed to expose to view the internal elements of the apparatus.

Figure 4 is a front elevation of the apparatus with the front panel of the cabinet carrying the loudspeaker and associated elements removed.

Figure 5 is a side elevation of the apparatus shown in Figure 3 and rotated ninety degrees on the drawing and with parts of the cabinet omitted for the purpose of sim- 'plification.

Figure 6 is an enlarged fragmentary diagonal section taken on line 6-6 of Figure 3.

Figure 7 isan enlarged fragmentary perspective view fife forward corner portion-of the sound cabinet.

2,915,134 Patented Dec. 1, 1959 Figure 8 is a diagrammatic plan view of the loudspeaker apparatus illustrating the paths followed by the sound emitted from the loudspeaker.

In the drawings, wherein for the purpose of illustration is shown a preferred embodiment of the invention, the numeral 10 designates generally a rectangular sound box or cabinet forming a sound chamber 11, Figure 8. The cabinet 10 is preferably constructed from relatively thin corrugated plywood or the like, and embodies side walls 12, top and bottom walls 13 and 14, a rear panel or wall 15 and a front panel 16. The box or cabinet 10 is preferably of glued construction, without the use of nails, screws or the like. I

The loudspeaker proper and all associated elements of the apparatus are mounted upon and bodily carried by the front panel 16, as will now be described.

A conventional loudspeaker 17, such as an eight inch permanent magnet speaker of the wide sound range type is arranged centrally of the front panel 16 and rigidly secured to the inner side of the front panel as at T8. The front panel 16 has a relatively large circular opening 19 formed therethrough in registry with the forward end of the loudspeaker cone, as indicated in Figure 2.

Arranged rearwardly of the loudspeaker -17 within the cabinet 10 and concentric with the loudspeaker is a relatively large main sound reflector or bafile 20, preferably formed of thin walled molded plastics materiaL'or the like. The main sound reflector 20 is centrally disposed within the cabinet 10, and as shown in the drawings, is rearwardly concave or bowl-like, and relatively deep, rearwardly of the loudspeaker 17. The forward side of the main sound reflector 20 is entirely open, and the reflector 20, as viewed from the front and rear, Figures 3 and 4, is shaped somewhat like a four leaf clover. By virtue of this clover-leaf shape, the bowl-like reflector 20 comprises four sound reflector portions or quadrants 21 of equal size or volume, and each of which is generally spherically concave, as indicated by the shading on the drawings. The forward open side of the soundreflector 20 is substantially larger than the diameter of the loudspeaker cone and the opening 19, as shown. Although it is preferred to form the main sound reflector 20 of plastics material, the same may be formed of sheet metal or any other suitable material capable of vibrating under the influence of sound.

Rigidly secured to each quadrant 21 of the main sound reflector 20, near the forward side-of the same, and being equidistantly spaced circumferentially of the main sound reflector, are four generally L-shaped brackets 22 which serve to adjustably mount the main sound reflector 20 upon thefront panel 16, through the medium of elements to be described.

The free arm of each bracket 22 is apertured to receive a mounting and adjusting bolt 23, Figure 6, which bolt extends forwardly of the sound reflector 20 and parallel to the common axis of the main sound reflector and loudspeaker 17. The forward end of each bolt 23 has screw-threaded engagement within a suitable nut 24, fixedly anchored within anopening formed through the front panel 16. A pair 'of rubber cups or washers 25 are mounted upon each bolt 23 upon opposite sides-of the projected arm of the adjacent bracket 22, to insulate such bracket against vibrations transmitted through the bolt 23.

A spacer block 26 of woodor the like is arranged upon the inner side of the front panel 16 adjacent to each bolt 23 and apertured to receive such bolt, as shown. Inwardly of each spacer block 26, a relatively small secondary sound reflector or ba'ffle 2-7 is mounted in opposed relation to themain sound reflector20. Each secondary sound reflector 27 has its rear side open, and each secondary sound reflector 27 is forwardly concave or how!- like and preferably shaped identical to the main reflector 20, but considerably smaller than the main reflector, as shown in the drawings. Each secondary sound reflector 27 is preferably formed of thin walled molded plastics material, or the like, and each secondary reoverlapping relation with one quadrant 21 of the main sound reflector 20. Portions of the next adjacent quadrants 28 of each secondary reflector 27 may also overlap the adjacent quadrant 21 of the main sound reflector. The quadrant 28 of each secondary reflector 27 which entirely overlaps the adjacent quadrant 21 of the main sound reflector 20 is disposed centrally of such quadrant 21, as best shown in Figure 4.

The forward substantially fiat wall 29 of each secondary sound reflector 27 is apertured somewhat eccentrically as shown at 30 to receive the adjacent bolt 23, Figure 6, and inwardly of the reflector wall 29, a vibration deadening washer 31 of rubber or the like is mounted upon each bolt 23 and engaging the wall 29. A compressible coil spring 32 surrounds each bolt 23 between the outermost washer 25 and the washer 31, as shown in Figure 6. The spring 32 is under tension, and serves to maintain the forward wall 29 of the secondary sound reflector 27 seated against the inner side of the spacer block 26. The spring 32 also serves to maintain the mounting bracket 22 firmly gripped between the resilient washers or cups 25.

Preferably, although not necessarily, a plurality of soft compressible spacer elements 33 of sponge rubber or the like are interposed between the opposed spaced edges of the main and secondary sound reflectors, at the points where these edges cross one another. The purpose of these compressible spacer elements 33 is to assure that the opposed edges of the main and secondary sound reflectors do not come into physical contact while they are vibrating under the influence of sound emitted from the loudspeaker 17. In some instances, the main and secondary sound reflectors 20 and 27 may be adjusted quite close to each other, and the compressible spacer elements 33 will prevent the opposed edges of the sound reflectors from contacting.

As shown in Figure 2, the front panel 16 of the sound cabinet is provided with four auxiliary sound emitting openings, spaced outwardly of the main circular opening 19 which registers with the loudspeaker. These auxiliary openings are preferably shaped in the manner shown in Figure 2, and arranged in two pairs with the openings of each pair identical as to shape and size, as indicated at 34 and 35. The pair of openings 34 are spaced equidistantly from opposite sides of the central opening 19 and are arranged in overlying relation to the outer portions of pairs of the quadrants 21 of the main sound reflector 20. The side openings 34 also partially overlie the closed sides of the secondary sound reflectors 27, as shown in Figure 2. The top and bottom openings 35 are likewise equidistantly spaced from the top and bottom of the central opening 19, and overlie upper and lower portions of the quadrants 21 of the main sound reflector 20. The openings 35 also overlie portions of the secondary sound reflectors 27, as shown in Figure 2.

The entire forward face of the front panel 16 is preferably covered by an ornamental cloth grille 36, through which sound may readily pass. The marginal portions of the cloth grille 36 are covered by a forward plywood frame 37, rigidly secured to the front panel 16, outwardly of the auxiliary sound emitting openings 34 and 35. The

frame 37 is entirely open inwardly of the outer straight edges of the openings 34 and 35 shown in Figure 2.

Operation The voice coil of the loudspeaker 17 is energized, and the loudspeaker emits the amplified broadcast sound, including a wide range of tones or sound frequencies which the speaker is capable of producing. In this connection, I prefer to employ a high quality loudspeaker capable of producing the extremely high pitch and also the low pitch or bass sounds, as well as all intermediate pitches or tones. The general purpose of the system of sound reflectors employed in the invention is to aid or supplement the loudspeaker 17 in faithfully producing a full range of tones over the entire audible register, some of which tones would become lost or inaudible, without the aid of the main and secondary sound reflectors 20 and 27.

In order to accommodate the acoustical characteristics of a particular loudspeaker 17, and also the acoustical characteristics of a particular room or area in which the loudspeaker apparatus is used, it may be desirable to adjust the position of the main sound reflector 20 relative to the loudspeaker 17 and secondary sound reflectors 27 to achieve the best overall results with the apparatus. In order to shift the main sound reflector 20 forwardly or rearwardly within the cabinet 10, the four adjusting screws 23 may be, adjusted forwardly or rearwardly upon the front panel 16. This serves to shift the main sound reflector 20 toward or from the loudspeaker and toward or from the secondary sound reflectors 27, and the compressible spacer elements 33 yield to permit the desired adjustment. The springs 32 serve at all times to hold the secondary sound reflectors 27 in contact with the spacer blocks 26, and the springs. also resiliently urge the innermost rubber washers 25 against the heads of the adjusting screws 23.

With reference to diagrammatic Figure 8, the full range of sound emitted from the loudspeaker 17 passes forwardly of the cabinet 10 through the central opening 19 in the usual manner as indicated by the arrows 38 in Figure 8. The sheet metal shell or basket 39 of the loudspeaker has the usual plurality of circumferentially equidistantly spaced openings 40 formed therein, and part of the sound emitted by the loudspeaker 17 passes through the openings 40 and is reflected rearwardly and into the concave quadrants 21 of the main sound reflector 20, as indicated by the arrows 41 in Figure 8. The sound waves thus entering the main reflector 20 are reflected forwardly by the main sound reflector and superimposed upon the sound waves emanating from the opening 19. Part of the sound reflected forwardly by the main reflector 20 passes through the auxiliary openings 34 and 35 of the front panel 16. This sound reflected from the main reflector 20 represents the extreme low frequencies of the audible register, and the main sound reflector 20 preserves and emanates these extremely low pitch or bass sounds, which otherwise would not be faithfully produced by the loudspeaker 17 without the use of the sound reflector 20.

Part of the sound reflected forwardly by the quadrants 21 0f the main sound reflector 20 enters and is intercepted by the rearwardly opening secondary sound 1'6? flectors 27, as indicated in Figure 8, and the secondary sound reflectors reflect this part of the sound rearwardly in the cabinet 10, toward the rear panel 15 as indicated by the alrows 42. This rearwardly reflected sound from the secondary sound reflectors 27 impinges on the rearpanel 15 of the cabinet and is again reflected forwardly as shown by the arrows 43 and this sound travels forwardly and is emitted through the auxiliary openings 34 and 35 and superposed upon the other emitted sounds as indicated by the arrows 44 in Figure 8.

The sound which is intercepted and reflected by the secondary sound reflectors 27 represents theextreme high frequency or high pitch ,portions of the audible register which would ordinarily notbe faithfully produced by the single loudspeaker 17, without the aid of the secondary sound reflectors. The combined action of the main and secondary sound reflectors 20 and 27 thus aids the single loudspeaker 17 in faithfully producing all of the tones of theaudibl'e register, including extremely low pitch and high pitch tones and all intermediate tones.

I have found by actual comparison tests that the single loudspeaker 17 used in conjunction with the main and secondary reflectors 20 and 27 produces with high fidelity a full range of tones, substantially equal in quality,

volume and carrying ability to the tones produced by ex-tremely expensive and large, high fidelity sound systems, employing a plurality of loudspeakers and a complicated system of internal sound cabinet baffles or sound reflecting panels. My system appears to function as though the main sound reflector 20 were a low pitch sound producing loudspeaker, commonly 'known as a woofer, and as though the secondary sound reflectors 27 were extremely high pitch sound producing loudspeakers, commonly known as tweeters. Nevertheless, as shown and described, the excellent results obtained by my apparatus are obtained with the use of only'one broad range loudspeaker 17. Conventional high fidelity sound producing systems employ an extremely large and expensive wooden cabinet, with a complicated system of baflles and a plurality of expensive loudspeakers, including intermediate range loudspeakers, woofers and tweeters. The necessity for all of this is eliminated in my system, and as stated, the results obtained appear to be substantially equal to'those obtained with the cumbersome and expensive conventional systems using a plurality of loudspeakers.

I wish to point out that the particular clover-leafed shape of the sound reflectors 20 and 27 appearsto be important in achieving the best possible results with the apparatus. The reason for this is not entirely understood, but it has been found by experimentation that the use of sound reflectors 20,-and 27 of this particular shape, and having the quadrants 21 and 28, produces better results than in the case where the sound reflectors 20 and 27 are merely generally spherically shaped, without the clover leaf. configuration and the resulting quadrants 21 and28. However, this feature is not believed to be extremely critical, and satisfactory results can be obtained where the reflectors 20 and 27 are merely plain bowllike reflectors of substantially spherical configuration.

It should also be mentioned that the use of relatively thin plywood, such as plywood approximately one-quarter of an inch in thickness, for the walls and panels of the cabinet appears to contribute materially to the overall excellent quality of sound produced by my system. Like- Wise, the provision of the auxiliary sound emitting openings 34 and 35, as shown in Figure 2, appears to aid materially in achieving the desired excellent results.

I also wish to point out that the adjusting screws 23 for the main sound reflector 20 serve a further purpose in the apparatus. When the screws 23 are tightened to bring the frontal edge of the main sound reflector 20 closer to the secondary sound reflectors 27, the tensioninthe springs 32 will be increased. This increase in tension on the springs 32 will affect the vibrating characteristics of the main and secondary sound reflectors 20 and 27. That is to say, when the screws 23 are tightened and the springs 32 have their tension increased, the wall 29 of each secondary sound reflector 27 will be more tightly gripped than where the springs 32 are under less tension. This will tend to increase the frequency of vibration and increase the pitch of the sound reflected from each secondary sound reflector 27. Likewise, the tightening of the screws 23 and the increased tension on the springs 32 will cause the brackets 22 of the main sound reflector 20 to be more tightly gripped, and since the brackets 22 are rigid with the main sound reflector, the frequencyof vibration of the main sound reflector will be changed and increased as in the case of the secondary sound reflectors. When the screws '23 are tightened, the main sound reflector will reflect sound from the loudspeaker 17 with a higher pitch and with a greater frequency of vibration, than when the screws 23 are relatively loose and the main sound reflector is spaced a relatively greater distance from the secondary sound reflectors. Likewise, when the screws 23 are relatively loose and less tension is on the springs 32, the secondary sound reflectors will vibrate with less frequency and tend to reflect sound of a lower pitch. Thus, the screws 23 and associated elements not only serve as a means to adjust the position of the main sound reflector 20, but also serve as a means to adjust the tone quality or fre quency of vibration of the main and secondary sound reflectors, and this constitutes .an important feature of the invention. k

It is to be understood that the form of the invention herewith shown and described is to be taken as a preferred example of the same, and that various changes in the shape, size and arrangement of parts may be re sorted to, without departing from the spirit of the in: vention or scope of the subjoined claims.

Having thus described my invention, I claim:

1. Loudspeaker apparatus comprising a cabinet defining a sound chamber, a loudspeaker mounted within said cabinet, one wall of said cabinet having a sound emitting opening adjacent to the loudspeaker, a main bowl-like sound reflector arranged within the cabinet rearwardly of the loudspeaker and being forwardly open relative to the loudspeaker, a plurality of secondary bowl-like sound reflectors mounted within a cabinet outwardly of the loudspeaker and spaced therefrom and being rearwardly open and arranged in opposition to said main sound reflector, and adjustable resilient supporting means connected with said main and secondary sound reflectors and bodily supporting them and secured to a Wall of said cabinet and constructed and arranged so that said main and secondary sound reflectors may be relatively shifted toward and from each other and the main sound reflector may be shifted toward and from said loudspeaker. I

2. High fidelity loudspeaker apparatuscomprising a cabinet defining a sound chamber and including a loudspeaker panel, a loudspeaker arranged within the cabinet and secured to said loudspeaker panel, said loudspeaker panel having a main opening substantially registering with the loudspeaker and a plurality of secondary openings arranged outwardly of the main opening and said loudspeaker, a main forwardly open bowl-like sound reflector arranged within the cabinet rearwardly of the loudspeaker and loudspeaker panel and being substantiall'y larger than the diameter of the loudspeaker, adjustable supporting means for the main sound reflector and connected with the loudspeaker panel of said cabinet, whereby the main sound reflector may be adjusted forwardly or rearwardly with respect to the loudspeaker and loudspeaker panel, portions of the main sound reflector extending adjacent to said secondary openings of the loudspeaker panel, and a plurality of rearwardly open bowllike secondary sound reflectors substantially smaller than the main sound reflector mounted within said cabinet outwardly of the side wall of said loudspeaker and near said secondary openings and facing the main sound reflector and arranged at least in partial overlapping relation therewith.

3. Loudspeaker apparatus comprising a sound cabinet including a panel having a main opening and a plurality of secondary openings surrounding and spaced from the main opening, a single loudspeaker mounted within said cabinet adjacent to said main opening, a main relatively large bowl-like sound reflector substantially larger in diameter than the loudspeaker arranged within said cabinet rearwardly of the loudspeaker and being forwardly open and facing said panel and spaced therefrom, adjustable supporting means for the main sound reflector and secured to said panel, whereby the main sound reflector may be adjusted forwardly or rearwardly with respect to the loudspeaker and said panel, and a plurality of relatively small bowl-like secondary sound reflectors mounted within said cabinet laterally outwardly of the loudspeaker and near said secondary openings of the panel and being rearwardly open and facing the main sound reflector and spaced therefrom and at least partially overlapping the main sound reflector.

4. Loudspeaker apparatus according to claim 3, Wherein the main and secondary sound reflectors have a clover- ,leaf-like frontal shape imparting thereto a plurality of separately defined generally spherically formed chambers.

5. Loudspeaker apparatus comprising a sound cabinet including a front panel having a main central opening and a plurality of secondary openings spaced from the central opening in surrounding relation thereto, a loudspeaker secured to the inner side of the front panel adjacent to the main central opening, a main forwardly open bowl-like sound reflector arranged within said cabinet and being materially larger than the loudspeaker and spaced rearwardly of said front panel and facing the front panel and having portions facing said secondary openings of the front panel, adjustable resilient means connected with the front panel laterally outwardly of the loudspeaker and bodily carrying the main sound reflector and rendering it adjustable toward and from the front panel, and a plurality of rearwardly open bowl-like secondary sound reflectors materially smaller than the main sound reflector arranged within said cabinet and connected with said adjustable resilient means and arranged laterally outwardly of the loudspeaker and near said secondary openings and being in opposed relation to said main sound reflector and having portions arranged outwardly of the wall of the main sound reflector, said portions adapted to reflect sound rearwardly of the-main sound reflector in said cabinet.

6. Loudspeaker apparatus according to claim 5, wherein the main sound reflector and each secondary sound reflector has generally the configuration of the four-leafed clover to provide upon the main sound reflector and each secondary sound reflector individually formed quadrants of generally spherical formation, at least one quadrant of each secondary sound reflector facing and in opposed relation to one quadrant of the main sound reflector.

7. Loudspeaker apparatus comprising a cabinet defining a sound chamber, said cabinet having sound emitting opening means, a loudspeaker mounted within said cabinet adjacent to said opening means, a relatively large bowl-like sound reflector mounted within said cabinet near the rear side of the loudspeaker and beingsubstantially concentric with the loudspeaker and materially larger than the diameter of the loudspeaker, said sound reflector being open at its side facing the loudspeaker and said opening means, a plurality of relatively small bowl-like sound reflectors arranged within said cabinet in opposed relation to the large sound reflector and being open at their sides facing away from the loudspeaker and facing the open side of the large sound reflector and adapted to reflect sound away from said opening means in said cabinet, and resilient supporting means common to said relatively large and realtively small sound reflectors and supporting the same bodily within said cabinet and secured to a wall of said cabinet.

8. Loudspeaker apparatus comprising a sound cabinet having a loudspeaker panel, said loudspeaker panel having a central opening and a plurality of secondary openings spaced from the central opening and arranged in surrounding relation thereto, a loudspeaker secured to the inner side of the loudspeaker panel and substantially registering with said central opening, a main forwardly open bowl-like sound reflector arranged within said cabinet substantially centrally thereof and rearwardly of the loudspeaker and being substantially larger in diameter than the loudspeaker, a plurality of mounting brackets carried by the main sound reflector near its periphery, a corresponding number of adjustable mounting bolts connected with said mounting brackets and having screwthreaded engagement with the loudspeaker panel and supporting the main sound reflector and rendering it adjustable toward and from the loudspeaker panel, a corresponding number of rearwardly open bowl-like secondary sound reflectors connected with said bolts and being substantially smaller than the main sound reflector and facing the main sound reflector and spaced therefrom and having portions extending beyond the periphery of the main sound reflector, the secondary sound reflectors being spaced from the periphery of the loudspeaker, and springs mounted upon said bolts and arranged between the secondary sound reflectors and the mounting brackets of the main sound reflector and serving to resiliently urge the main and secondary sound reflectors away from engagement with each other.

9. Loudspeaker apparatus according to claim 8, and compressible spacer means arranged between the marginal edges of the main and secondary sound reflectors to prevent'such edges from contacting when the main sound reflector is adjusted toward said loudspeaker panel.

10. Loudspeaker apparatus according to claim 8, and compressible vibration dampening means connected with said bolts and engaging said mounting brackets to insulate the same from vibrations transmitted through the bolts.

11. Loudspeaker apparatus comprising a cabinet defining a sound chamber, a loudspeaker mounted within the cabinet adjacent to one wall of the cabinet, said one wall having an opening in substantial registration with the loudspeaker and a plurality of secondary openings surrounding the first-named opening and spaced therefrom, a main forwardly open bowl-like sound reflector arranged within the cabinet rearwardly of the loudspeaker and being larger in diameter than the loudspeaker, a plurality of rearwardly open bowl-like secondary sound reflectors substantially smaller than the main sound reflector arranged within the cabinet outwardly of the loudspeaker and near the secondary openings and facing the main sound reflector near marginal portions of the main sound reflector, and adjustable resilient means interconnecting the main and secondary sound reflectors and supporting the main sound reflector and operable to vary the distance between the main and secondary sound reflectors and also adapted to exert a variable holding force upon the main and secondary sound reflectors to vary their frequencies of vibration and their pitch characteristics when they reflect sound in the apparatus.

12. Loudspeaker apparatus according to claim 11, and wherein said adjustable resilient means comprises a plurality of screw-threaded elements engaging said one wall of the cabinet and connected with the main and secondary sound reflectors, and a corresponding number of springs mounted upon said screw-threaded elements and connected with the main and secondary sound reflectors, whereby all of said sound reflectors are tuned by the loosening or tightening of said screw-threaded elements.

References Cited in the file of this patent UNITED STATES PATENTS 1,532,811 Graham Apr. 7, 1925 FOREIGN PATENTS 473,046 France Sept. 5, 1914 109,966 Australia Feb. 29, 1940

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1532811 *Aug 29, 1924Apr 7, 1925Graham Edward AlfredCabinet for use with sound-reproducing devices
AU109966B * Title not available
FR473046A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3097720 *Sep 20, 1960Jul 16, 1963Jr George H TaylorAcoustical enclosure and low frequency sound amplifier for a loudspeaker
US4225010 *Apr 18, 1979Sep 30, 1980Arthur P. BagbyLoudspeaker system
US4231445 *Dec 4, 1978Nov 4, 1980Johnson Rubein VAcoustic lens speaker cabinet
US4509192 *Apr 7, 1983Apr 2, 1985Straughn Roy DSpeaker enclosure
US4967872 *Jun 19, 1989Nov 6, 1990F. H. Hart Engineering Co., Inc.Loud speaker system
US7549507 *Aug 6, 2004Jun 23, 2009Babcock-Hitachi Kabushiki KaishaDuct wall structure
US8820471 *Dec 12, 2012Sep 2, 2014Yamaha CorporationSpeaker
US20130146389 *Dec 12, 2012Jun 13, 2013Yamaha CorporationSpeaker
Classifications
U.S. Classification181/156
International ClassificationH04R1/34, H04R1/32
Cooperative ClassificationH04R1/345
European ClassificationH04R1/34C