Omni-directional speaker system

Abstract: An omni-directional speaker system comprises a speaker cabinet and at least one speaker unit fixed in the speaker cabinet. To provide an omni-directional speaker system for generating sound waves equally in every direction by 360° which is low in price and satisfies the user demand a first reflecting plate has a hole and is installed in front of the speaker unit for dispersing sound waves transmitted therefrom and a second reflecting plate is dispersed in front of said hole.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an omni-directional speaker system, and in particular, to an omni-directional speaker system with three-dimensional 360° directivity, which can be used for general purpose miniaturization applications and satisfy the user demand of home theatre. 2. Description of the Related Art Omni-directional speaker systems started to be produced in 1958 and have been put on the market mainly for high fidelity (Hi-Fi) applications by several manufacturers. There are two types of omni-directional speaker systems depending on their structures. One type is obtained by combining a plurality of directional speakers. Despite high quality omni-directional sound source, this omni-directional speaker system has the disadvantage that its cabinet becomes large, heavy, and difficult to fabricate. FIGs. 1A to 1D are schematic views of conventional differently configured speaker systems. In the drawings, for example, a hexahedral cabinet 10 of FIG. 1A has a speaker unit on each face thereof, and an octahedral cabinet 20 of FIG. 1B also has the speaker unit on each face thereof. A spherical cabinet 40 of FIG. 1D has a plurality of speaker units 11 on the upper, lower, left, and right portions. These speaker cabinets are large, heavy, and difficult to fabricate. The other type of omni-directional speaker system uses a diffuser on its frontal face. As shown in FIG. 2, a diffuser-type omni-directional speaker system of Pioneer Co., Japan, includes a spherical cabinet 50 supported by a cabinet leg 51. A sound absorbing material 52 is applied on the inner surface of the cabinet 50 and a speaker unit 53 is directed upward in the upper portion of the cabinet 50. Fixing legs 55 are installed on the cabinet 50 to support a diffuser 54. In the speaker system, sound waves emitted from the speaker unit 53 is reflected from the diffuser 54 on the fixing legs 55 and diffused bidirectionally so that a listener can listen stereophonic sound. Such a speaker system allows the cabinet to be miniaturized but has limitations in realizing 360° omni-directivity and controlling sound quality. Moreover, the sound pressure of treble and intermediate sound is different from that of bass sound due to sensitiveness of the treble and intermediate sound to directivity and use of a reflecting plate, thereby making it difficult to balance the treble and intermediate sound. As a result, to obtain omni-directivity with a single speaker having a diffuser on its front face, an expensive speaker unit should be used to turn up the sound pressure level of the treble and intermediate sound or a complicated diffuser should be employed. That is why the above speaker system fails to achieve popularity. Another diffuser type omni-directional speaker system, also made by Pioneer Co., Japan, is shown in FIG. 3. In the lower portion of a cylindrical cabinet 60 sealed up and down, a woofer 62 is mounted on a speaker baffle 63 over a diffuser 61, and three ducts 64 and three tweeters 65 are provided in the upper portion thereof. In the speaker system, bass sound emitted from the woofer 62 is diffused bidirectionally through reflection from the diffuser 61, and sideward through the duct 64. Treble sound emitted from the tweeters 65 in the upper portion of the cabinet 60 is diffused bidirectionally so that a listener can listen stereophonic sound. This speaker system requires a plurality of speakers, thereby increasing the size and weight of the cabinet and making it difficult to realize 360° omni-directivity and control sound quality. US-A-4 322 578 discloses an apparatus for achieving a uniform omni-directional radiation of sound waves, wherein this apparatus is a loud speaker comprising a housing with a reflection-diffraction system in front of the housing. This system comprises a number of reflectors, wherein at least the first three reflectors are not totally reflecting and each have a zone of transparency. These zones are made of circular holes. SUMMARY OF THE INVENTION An object of the present invention is to provide an omni-directional speaker system for generating sound waves equally in every direction by 360°, which can be used for general purpose miniaturization applications at a low price and satisfy the user demand of home theatre. This object is solved by an omni-directional speaker system with the features of claim 1. The speaker cabinet may be formed by separably combining upper and lower hemispherical cabinets, each of the upper and lower speaker cabinets has a fixing rib which includes an engaging protrusion and an engaging groove corresponding to an engaging groove and an engaging protrusion of the other speaker cabinet, and the speaker unit is formed by separably combining upper and lower speaker with the lower surfaces thereof facing each other in the speaker cabinet. The speaker cabinet may include a plurality of openings of a predetermined size on the surface thereof, for better dispersal of sound waves emitted from the speaker unit, and the second reflecting plate may be supported by a plurality of support ribs to be integrated with the first reflecting plate. The first reflecting plate is convex toward the interior of the speaker cabinet, the second reflecting plate is convex toward the hole, and the hole is spherical. According to the present invention an omni-directional speaker system is provided which offers an optimal dispersal of sound and is cheap by using a relatively cheap and general conical speaker unit for improving diffusion of treble and intermediate range sound. A sound reflecting plate of a speaker cabinet in a three dimensional 360° omni-directional speaker system, may have a hole to offer more direct sound components to a listener. BRIEF DESCRIPTION OF THE DRAWINGS The above objects and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which: FIGs. 1A to 1D are schematic views of conventional differently configured speaker systems; FIG. 2 is a schematic view of a conventional diffuser-type speaker system; FIG. 3 is a schematic view of another conventional diffuser-type speaker system; FIG. 4 is a perspective view of an omni-directional speaker system according to a first embodiment of the present invention; FIG. 5 is a sectional view of the omni-directional speaker system according to the first embodiment of the present invention; FIG. 6 is a sectional view of an omni-directional speaker cabinet according to the first embodiment of the present invention; FIG. 7 is an exploded perspective view of an omni-directional speaker system according to a second embodiment of the present invention; FIG. 8 is an assembled perspective view of the omni-directional speaker system shown in FIG. 7; FIG. 9 is a sectional view of the omni-directional speaker system shown in FIG. 8; FIG. 10 is an exploded perspective view of a speaker system in which an omni-directional speaker cabinet shown in FIG. 8 is to be installed; FIG. 11 is a partially cut perspective view of the speaker system in which the omni-directional speaker cabinet of FIG. 8 is assembled; FIG. 12 is a sectional view of the speaker system in which the omni-directional speaker cabinet of FIG. 8 is assembled; FIG. 13 is a view illustrating the directions in which sound waves are diffused from the speaker system of FIG. 12; FIG. 14 is a perspective view of an omni-directional speaker system according to another example; FIG. 15 is a sectional view of the omni-directional speaker system shown in FIG. 14; FIG. 16 is a schematic view of an omni-directional speaker cabinet shown in FIG. 14; FIG. 17 is a perspective view of an omni-directional speaker system according to a further example; FIG. 18 is a sectional view of the omni-directional speaker system shown in FIG. 17; and FIG. 19 is a schematic view of an omni-directional speaker cabinet shown in FIG. 17. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Like reference numerals denote the same components in the drawings. It should be noted that a detailed description of a related known function or structure of the present invention will be omitted if it is deemed to obscure the subject matter of the present invention. FIGs. 4 and 5 are perspective and sectional views of an omni-directional speaker system according to a first embodiment of the present invention, respectively. FIG. 6 is a schematic view of an omni-directional speaker cabinet according to the first embodiment of the present invention. Referring to FIGs. 4, 5, and 6, speaker units 71 are fixed in a spherical speaker cabinet 70 in the omni-directional speaker system of the present invention. First reflecting plates 72 are disposed over the upper surfaces of the speaker units 71, for dispersing sound waves. Holes 73 pass through the centres of the first reflecting plates 72. Over the holes 73 are formed second reflecting plates 74. Openings 75 of a predetermined size are formed on the overall surface of the speaker cabinet 70, for better dispersal of sound waves emitted from the speaker units 71 and then reflected from the first reflecting plates 72. The speaker cabinet 70 is obtained by separably combining two hemispherical cabinets in a vertical direction. Each of the upper and lower speaker cabinets has a fixing rib including engaging protrusions and grooves 76 and 77 corresponding to engaging grooves and protrusions 77 and 76 in the fixing rib of the other speaker cabinet, for use in engaging the upper and lower cabinets. The speaker units 71 can be separably combined in a vertical direction with the lower surfaces thereof facing each other, or integrally formed. The second reflecting plates 74 are supported over the holes 73 by a plurality of support ribs 78 to be integrated with the first reflecting plates 72. The first reflecting plates 72 are of a hemisphere convex toward the interior of the speaker cabinet 70. The second reflecting plates 74 are of a hemisphere convex toward the holes 73. The holes 73 are formed into a sphere. In the above omni-directional speaker system, the second reflecting plates 74 are formed over the holes 73 of the first reflecting plates 72, and the speaker units 71 are fixed facing to each other and spaced from the first reflecting plates 72, in the upper and lower speaker cabinets having the openings 75 of the predetermined size formed on their surfaces to achieve a better dispersal of reflected sound. Then, the upper and lower speaker cabinets are combined by use of the engaging protrusions and grooves 76 and 77. Thus, the speaker cabinet 70 becomes spherical to have a three dimensional 360° directivity. In the thus-constituted omni-directional speaker system, sound waves emitted from the speaker units 71 are reflected from the first reflecting plates 72 and dispersed at an incident angle through the openings 75 of the speaker cabinet 70. Here, since the frequency characteristics of the reflected sound is significantly affected by the distance L between the speaker unit 71 and the first reflecting plates 72, the distance L should be constant. Part of the sound waves of the speaker unit 71 are directly dispersed through the holes 73, and the other sound waves are reflected from the second reflecting plates 74 and then from the first reflecting plates 72 before they are dispersed forward. The size of the holes 73 determines that of the second reflecting plates 74 and depends on the distance L between the speaker unit 71 and the first reflecting plates 72. Therefore, the size of the holes 73 is closely related with the frequency characteristics of the reflected sound. In addition, the spherical shape of the first and second reflecting plates 72 and 74 contributes to improvement of the frequency characteristics. Referring to FIGs. 7, 8, and 9, there will be a detailed description of an omni-directional speaker system according to a second embodiment of the present invention. In the speaker system, speaker units 81 are fixedly installed to face each other with respect to partitions 87 in a speaker cabinet 80. First reflecting plates 82 having holes 85 at the centres thereof are formed in front of holes 83 in the speaker units 81, for dispersing soundwaves. Second reflecting plates 84 are positioned in front of the holes 85. The first and second reflecting plates 82 and 84 acts to reflect and thus disperse sound waves emitted from the speaker units 81 fixed in the speaker cabinet 80 in every direction. The speaker cabinet 80 is preferably rectangular hexahedral, formed by separably combining two cabinets having fixing ribs at the sides thereof. The first reflecting plates 82 are supported by a plurality of support ribs 88 to be integrated with the speaker cabinet 80. The second reflecting plates 84 are supported by a plurality of support ribs 89 to be integrated with the first reflecting plates 82. The first reflecting plates 82 are of a hemisphere convex toward the holes 83 of the speaker cabinet 80, and the second reflecting plates 84 are of a hemisphere convex toward the holes 85 of the first reflecting plates 82. The holes 83 and 85 are spherical. In order to achieve a good dispersal of reflected sound in the above omni-directional speaker system, the speaker units 81 are fixed to face each other in both frontal and rear speaker cabinets. The speaker units 81 are spaced from the first reflecting plates 82 by a predetermined distance. As shown in FIG. 9, sound waves a emitted from the holes 83 of the speaker units 81 are reflected at an incident angle from the first reflecting plates 82 and dispersed sideward and rearward. The frequency characteristics of the reflected sound waves a varies with the distance between the speaker units 81 and the first reflecting plates 82. Thus, the distance should be constant. Part of sound waves b emitted from the speaker unit 81 is directly dispersed through the holes 85 of the first reflecting plates 82, and the other sound waves b are reflected from the second reflecting plates 84 and then the first reflecting plates 82, thereby to be dispersed forward. The size of the holes 85 of the first reflecting plates 82 determines that of the second reflecting plates 84, and depends on the distance between the speaker unit 81 and the first reflecting plates 82. Therefore, the size of the holes 85 is closely related with the frequency characteristics of the reflected sound. Further, the hemispherical shape of the first and second reflecting plates 82 and 84 contributes improvement of the frequency characteristics. A speaker system in which the above omni-directional speaker cabinet is assembled with a tweeter cabinet will be describe referring to FIGs. 10 and 11. A hexahedral intermediate and bass sound speaker cabinet 90 has a sound absorbing material 91 applied to the inner walls thereof and a hole 92 formed into the bottom thereof. An intermediate and bass sound speaker unit 93 is inserted into the hole 92, with the upper surface thereof directed downward. A stand 94, which has a reflecting plate 95 convex at its centre and legs 96 in the corners thereof, is engaged with the intermediate and bass sound cabinet 90 by screws 97. Then, a front panel 98 is attached to the frontal surface of the intermediate and bass sound cabinet 90. The treble and intermediate sound speaker cabinet 80 having the treble and intermediate speaker units 81 is mounted on the treble and intermediate sound speaker cabinet 90. An upper panel 100 having a grill 99 is mounted on the treble and intermediate sound cabinet 90 to cover the multi-directional speaker cabinet 80 with the grill 99. The grill 99 is installed at the centre of the upper panel 100, protruded upward into a rectangle. In the above speaker system, the rectangular hexahedral speaker cabinet can be replaced with the spherical speaker cabinet according to the first embodiment of the present invention. In the above speaker system, sound waves c emitted from the intermediate and bass sound speaker unit 93 under the hole 92 of the intermediate and bass sound speaker cabinet 90 is reflected from the convex reflecting plate 95 on the stand 94 and dispersed through the space between the intermediate and bass sound speaker cabinet 90 and the stand 94, as shown in FIGs. 12 and 13. Sound waves a emitted from the holes 83 of the speaker units 81 are reflected from the first reflecting plates 82 at an incident angle and dispersed sideward and rearward. Part of sound waves b emitted from the treble and intermediate sound speaker unit 80 are directly dispersed through the holes 83 of the first reflecting plates 82, and the other sound waves b are reflected from the second reflecting plates 84 and then the first reflecting plates 82, thereby to be dispersed. That is, the sound waves emitted from the intermediate and bass sound speaker unit 93 is reflected from the convex reflecting plate 95 and dispersed in every direction, and the sound waves emitted from the treble and intermediate sound speaker units 81 are dispersed in every direction by the first and second reflecting plates 83 and 84. A three-dimensional 360° omni-directional speaker system as describe above disperses sound waves equally in every direction by 360°, can be used for miniaturization applications at a low price, and can satisfy the user demand of home theatre. In an omni-directional speaker system according to an example without a second reflecting plate, the speaker units 71 are fixed in a spherical cabinet 70-1, as shown in FIGs. 14, 15, and 16. Sound reflecting plates 72-1 are formed over the upper surfaces of the speaker units 71, for dispersion of sound waves. The sound reflecting plates 72 are convex toward the interior of the cabinet 70-1. The cabinet 70-1 is formed by separably combining hemispherical cabinets. The upper cabinet has a fixing rib 74-1 which includes engaging protrusions 76 and grooves 77. The lower cabinet has a fixing rib 75-1 which includes engaging protrusions 76 and grooves 77. The engaging protrusions 76 and grooves 77 of the upper cabinet correspond to the engaging grooves 77 and protrusions 76 of the lower cabinet. The speaker units 71 may be separably combined to face each other or integrally formed. The speaker units 71 are fixed in the cabinet 70-1, apart from the sound reflecting plates 72-1 by a predetermined distance. Then, the upper and lower cabinets are combined into a sphere by engaging the engaging protrusions 76 of the fixing ribs 74-1 with the engaging grooves 77 of the fixing ribs 75-1, so that the cabinet 70-1 has a three- dimensional 360°directivity. The hemispherical sound reflecting plates 72 are formed over the speaker units 71, for reflecting and dispersing sound waves. The size of the sound reflecting plates 72 is set to be equal to the vibration radius of the speaker units 71, that is, the cross-section area of vibration plates in the speaker units 71, to increase reflection efficiency and the size of the sound reflecting plates 72-1. The reflecting plates 72-1 is hemispherical to reflect sound waves in unspecified directions and thus more broadly, for use in a three-dimensional 360° omni-directional speaker system. Sound waves a emitted from the speaker units 71 are reflected from the sound reflecting plates 72-1 at an incident angle and first reflected sound waves b are dispersed through the cabinet 70-1. The frequency characteristics of the reflected sound is significantly affected by the distance L between the speaker units 71 and the sound reflecting plates 72-1. Thus, the distance L should be constant. Sound waves emitted from the speaker units 71 are reflected from the hemispherical sound reflecting plates 72-1 and dispersed in every direction. The omni-direction speaker system as described above can disperse sound waves equally in every direction by 360°, improves dispersal of intermediate and treble sound which is the most important issue in an omni-directional speaker system, and can be provided at a low price by use of relatively cheap and general conical speaker units. An omni-directional speaker system according to a further example without a second reflecting plate will be described referring to FIGs. 17, 18, and 19. The speaker units 71 are fixed in the spherical cabinet 70-1, and the sound reflecting plates 72 are formed over the upper surfaces of the speaker units 71, for dispersion of sound waves. The sound reflecting plates 72 have the holes 73 in the centres thereof. The cabinet 70-1 is formed by separably combining hemispherical cabinets. The upper cabinet has the fixing rib 74-1 which includes the engaging protrusions 76 and grooves 77. The lower cabinet has the fixing rib 75-1 which includes the engaging protrusions 76 and grooves 77. The engaging protrusions 76 and grooves 77 of the upper cabinet correspond to the engaging grooves 77 and protrusions 76 of the lower cabinet. The speaker units 71 may be separably combined to face each other or integrally formed. The sound reflecting plates 72 are convex toward the interior of the cabinet 70-1. The holes 73 are formed into a sphere of a predetermined size to improve the directivity of the speaker upward and downward, sound pressure, and frequency response characteristics. The speaker units 71 are fixed in the cabinet 70-1, apart from the sound reflecting plates 72 by a predetermined distance. Then, the upper and lower cabinets are combined into a sphere by engaging the engaging protrusions 76 of the fixing ribs 74-1 with the engaging grooves 77 of the fixing ribs 75-1, so that the cabinet 70-1 has a three- dimensional 360°directivity. Sound waves a emitted from the speaker units 71 are directly dispersed through the holes 73 of the sound reflecting plate 72. Sound waves b emitted from the speaker units 71 are reflected from the sound reflecting plates 72 at an incident angle and dispersed sideward through the cabinet 70-1. The frequency characteristics of the reflected sound is significantly affected by the distance L between the speaker units 71 and the sound reflecting plates 72. Thus, the distance L should be constant. Part of sound waves emitted from the speaker units 71 are directly dispersed forward through the holes 73 of the sound reflecting plates 72, and the other sound waves are reflected from the hemispherical sound reflecting plates 72 and dispersed sideward. The size of the holes 73 is affected by the distance L between the speaker units 71 and the sound reflecting plates 72. Therefore, the size of the holes 73 is closely related with the frequency characteristics of the reflected sound. The omni-direction speaker system as described above can disperse sound waves equally in every direction by 360°. The ratio of direct sound, which directly reaches the listener from a sound source like an instrument or voice, to indirect sound, which is reflected from an obstacle such as the floor, ceiling, and walls of a room and then reaches the listener, should be 7:3 to provide music to a listener with natural feeling. To satisfy this condition, the holes are formed into the sound reflecting plates. Thus, more direct sound can be provided to the listener. While the present invention has been described in detail with reference to the specific embodiments, they are mere exemplary applications. Thus, it is to be clearly understood that many variations can be made by anyone skilled in the art within the scope of the present invention, as defined by the claims.

Claims: An omni-directional speaker system comprising a speaker cabinet (70, 80) and at least one speaker unit (71, 81) fixed in the speaker cabinet, a first reflecting plate (72, 82) having a hole (73, 83) and installed in front of the speaker unit for dispersing sound waves emitted therefrom and a second reflecting plate (74, 84) disposed in front of said hole (73, 83) characterized in that the first reflecting plate (72, 82) is convex towards the interior of the speaker cabinet (70, 80). The omni-directional speaker system according to claim 1, characterized in that said first reflecting plate (72, 82) is installed in the speaker cabinet (70). The omni-directional speaker system according to claim 1, characterized in that the speaker cabinet (80) has holes (85) in both sides thereof and a partition (87) in the center of the speaker cabinet, said speaker units (81) are disposed to face each other with respect to the partition (81) and first reflecting plates (82) are installed in front of each hole (85) of the speaker cabinet, whereby sound waves emitted from the speaker units are dispersed in every direction by the first and second reflecting plates (82, 84). The omni-directional speaker system according to one of the previous claims, characterized in that said speaker cabinet (70, 80) is formed by separably combining cabinets. The omni-directional speaker system according to claim 4, characterized in that the cabinets (70) are hemispherical. The omni-directional speaker system according to at least one of the previous claims, characterized in that each cabinet has at least one fixing rib (74-1, 75-1) which includes an engaging protrusion (76) and an engaging groove (77) corresponding to an engaging groove at an engaging protrusion of the other speaker cabinet. The omni-directional speaker system according to one of the previous claims, characterized in that the speaker cabinet (70, 80) includes a plurality of openings (75,83) of a predetermined size on the surface thereof for better dispersal of sound waves emitted from the speaker unit. The omni-directional speaker system according to one of the previous claims, characterized in that said second reflecting plate (72) is supported by a plurality of support ribs (78) to be integrated with the first reflecting plate (72). The omni-directional speaker system according to at least one of the previous claims, characterized In that the first reflecting plates (82) are supported by a plurality of support ribs (88) to be integrated with the speaker cabinet (80). The omni-directional speaker system according to one of the previous claims, characterized in that the second reflecting plate (74, 84) is convex towards the hole (73, 85). The omni-directional speaker system according to one of the previous claims, characterized in that the holes (73, 85) are spherical. The omni-directional speaker system according to one of the previous claims, comprising an intermediate and bass speaker cabinet (90) having a sound absorbing material (91) applied to the inner walls thereof and a hole (92) formed into the bottom thereof; an intermediate and bass sound speaker unit (93) inserted into the hole, and a stand (94) having legs for supporting the intermediate and bass speaker cabinet (90) and a reflecting plate (95) in the center thereof, characterized in that the reflecting plate (95) of the stand (94) is convex in the center thereof towards the intermediate and bass sound speaker unit (93). The omni-directional speaker system according to one of the previous claims, characterized in that the first reflecting plates are supported by a plurality of support ribs (88) integrated with the omni-directional speaker cabinet and the second reflecting plates are supported by a plurality of support ribs (78) integrated with the first reflecting plates. The omni-directional speaker system according to one of the previous claims, characterized in that the first and second reflecting plates (72, 82; 74, 84; 95) are formed into a hemisphere convex towards the interior of the omni-directional speaker.

Inventors: CHOI JAE-SOON, HAM HOON-SOO, JEON SANG-HUN, KIM MIN, KWAK JUNG-HUN, LEE JONG-MIN, CHOI, JAE-SOON, HAM, HOON-SOO, JEON, SANG-HUN, KIM, MIN, KWAK, JUNG-HUN, LEE, JONG-MIN
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1998
Main classification: H04R1
IPC codes: H04R1, H05K5