Television receiver loudspeaker device

Abstract: A loudspeaker unit for a television receiver includes loudspeakers SP L ,SP R arranged at the back of a television screen surface, sound reflectors for reflecting the sound from the loudspeakers substantially in a forward direction from the television screen surface, and acoustic lenses provided on a surface coplanar with the television screen surface for controlling the sound radiating direction. High quality sound with a sense of ambience and compatibility with the television picture may be produced without enlarging the size of the television receiver cabinet.

Description: This invention relates to a loudspeaker device of a television receiver. Certain conventional television receivers and loudspeaker devices therefor are constructed as shown for example in figures 1 to 4 of the accompanying drawings. In the television receiver, shown in figure 1, loudspeakers SP L ,SP R are embedded within the front sides of a cabinet CT substantially flush with and at left and right sides of a front surface of a Braun tube BR, that is, a television screen surface. In a separate type television receiver, shown in Figure 2, the cabinet CT is separated from loudspeaker boxes or enclosures BX L ,BX R and loudspeakers SP L ,SP R are provided within the loudspeaker boxes BX L , BX R substantially flush with a television screen surface. In the type of television receiver shown in Figure 3, loudspeakers SP L , SP R are embedded within a cabinet CT at the back of the television screen surface, that is, at the back of a Braun tube BR. Finally, in the type of television receiver shown in Figure 4, loudspeakers SP L , SP R are embedded within the lateral sides of a cabinet CT at the lateral sides of a Braun tube BR. In recent years, in addition to high picture quality and a large screen surface, demand has arisen for high sound quality. It is desirable that the sound of a television receiver appears to be radiated from the vicinity of the displayed picture. A further design consideration is that it is also desirable that, even if the screen has a large surface, the cabinet of the receiver itself should not be excessively increased in bulk. These conflicting demands have been difficult to reconcile with the types of conventional television receivers, shown in figures 1 to 4. For example, with the television receiver and the loudspeaker devices shown in Figure 1, where the loudspeakers SP L ,SP R are arranged substantially flush with the television screen surface, although the sense of compatibility of the sound with respect to the television picture may be achieved, the size of the loudspeaker devices SP L ,SP R is limited by the size of the cabinet CT and hence sound of high sound quality cannot be produced in the low frequency part of the spectrum. In other words, with the television receiver of recent years, as shown in Figure 1, the surface of the television receiver in its entirety as viewed from the front side is not increased, that is, the size of the cabinet CT is not increased, although the screen surface is enlarged, as a result of which the size of the loudspeakers SP L ,SP R and those of their magnetic circuits and their enclosures are limited and hence the high sound quality cannot be achieved. With the television receiver shown in figure 2, in which the loudspeaker boxes BX L ,BX R are formed as separate components, even though good sound quality may be achieved, the overall size of the loudspeaker boxes BX L ,BX R and the size of the cabinet CT, summed together, is necessarily increased: With the television receiver shown in Figure 3, in which the loudspeakers SP L ,SP R are arranged at the back of the television screen at the rear lateral sides of the Braun tube BR, permitting the size of the loudspeakers SP L ,SP R to be increased, since these loudspeakers are arranged at a certain angle with respect to the television screen surface, the sound is radiated in a direction conforming to that angle and hence the sense of ambience and compatibility with the television picture cannot be produced. Finally, with the television receiver shown in figure 4, the loudspeakers SP L ,SP R are directed completely to lateral sides, so that the sense of ambience and compatibility with the television picture becomes worse than in the case of the television receiver shown in figure 3. In view of the above described status of the art, it is an object of the present invention to provide a loudspeaker device of a television receiver by means of which the sound of high quality producing the sense of ambience and compatibility with the television picture may be obtained without enlarging the size of the receiver cabinet, or which at least provides the public with a useful choice. EP-A-0,342,117 and US-A-5,119,429, on which the preamble of claim 1 is based, disclose a television wherein a bass loudspeaker is mounted behind the face of the cathode ray tube in an enclosure from which sound produced by the bass loudspeaker emerges through a columnar opening in the front panel of the television. According to the present invention there is provided a loudspeaker unit of a television receiver comprising loudspeaker means provided rearwardly of the television screen surface, sound reflector means for reflecting at least a portion of the sound from said loudspeaker means substantially in a forward direction from said television screen surface, characterised by acoustic lens means provided on a surface substantially coplanar with said television screen surface for controlling the radiating direction of the sound. The sound reflector means are provided for covering at least the central voice coil region of the loudspeaker means and approximately 20% to 70%, and preferably 30% to 60%, of the total sound radiating surface of the loudspeaker means. Since the loudspeaker unit is provided at the back of the television screen surface (the phosphor surface of the Braun tube), the screen surface can be increased without limitations placed by the loudspeaker unit, while the sound radiated from the loudspeaker unit can be reflected in a forward direction by a reflector plate, and diffused by an acoustic lens, the foremost part of which lies in a plane coplanar with the television screen surface, the sound producing the sense of ambience and compatibility with the television picture may be obtained. Specifically, the loudspeaker unit provided at the back of the screen surface and at least a portion of the sound from the loudspeaker unit is reflected in a substantially forward direction from the screen surface and radiated by the acoustic lens the forward end of which is arranged in a plane substantially coplanar with the screen surface, so that the well-defined sound image may be produced and the sound of high quality producing the sense of ambience and compatibility with the television picture may be obtained. The invention will be further described by way of non-limitative example with reference to the accompanying drawings, in which:- Figures 1 to 4 are schematic side views showing various types of conventional television receivers. Figure 5 is a schematic plan view showing a loudspeaker unit for a television receiver according to a preferred embodiment of the present invention, with portions of the loudspeaker unit and the television receiver being broken away. Figure 6 is an enlarged schematic plan view of the loudspeaker unit, with a portion thereof being broken away. Figure 7 is a schematic plan view showing a reflector plate and the sound radiating front surface of a loudspeaker. Figure 8 is a front view showing the state in which the loudspeaker and the reflector plate are actually mounted in the loudspeaker unit. Figure 9 is a perspective view showing an acoustic lens. Figure 10 is a partial perspective view showing an acoustic lens and a mesh plate actually mounted on a receiver cabinet. Figure 11 is a perspective view of a television receiver fitted with the loudspeaker unit of the present invention, with a portion of the receiver being broken away to show the structure of the loudspeaker unit. Referring to the drawings, an embodiment of the present invention will be explained in detail. As shown in the schematic plan view of figure 5, the loudspeaker unit for the television receiver of the present embodiment is comprised of left and right full-audio-range stereophonic loudspeakers SP L ,SP R arranged at the back of a television screen surface or at the rear lateral sides of a Braun tube BR, reflector plates RF L ,RF R for reflecting at least a portion of the sound from the loudspeakers SP L ,SP R in a substantially forward direction from the screen surface,and acoustic lenses L L ,L R , the forward end of which is disposed in a plane substantially coplanar with the screen surface and which is adapted for controlling the directivity of the radiated sound. The sound from the loudspeakers SP L ,SP R may also be monaural or stereo, depending upon the type of transmission being received and the audio processing circuitry of the receiver. It is noted that the loudspeakers SP L ,SP R are not provided in a plane coplanar with the television screen surface, but are provided rearwardly thereof, at the rear lateral sides of the Braun tube BR within the receiver cabinet CT. That is, the loudspeakers SP L ,SP R are provided at the rear lateral sides of the Braun tube BR where a wider area or space may be conserved depending on the shape of the Braun tube BR, so that the sound radiating surface or gauge and the capacities of the magnetic circuit and loudspeaker boxes BX L ,BX R may be chosen to be larger. Since the gauges of the loudspeakers SP L ,SP R and the capacities of the magnetic circuit and the loudspeaker boxes BX L ,BX R are chosen to be larger with the present embodiment, the sound quality of, for example, the low-frequency sounds may be improved, while the cabinet CT may remain small-sized. Meanwhile, since the loudspeakers SP L ,SP R of the present embodiment are arranged at the rear lateral sides of the Braun tube BR depending on the shape of the Braun tube, the sound radiating surfaces of the loudspeakers SP L ,SP R are disposed at an angle with respect to the television screen surface. If the sound from these loudspeakers SP L ,SP R is directly taken out to outside in this case, it becomes difficult to produce the sense of ambience or the sense of compatibility with the television picture on account of sound directivity and the like. With this in view, with the loudspeaker unit of the present embodiment, the sound from the loudspeakers SP L ,SP R is adapted to be directed forwardly from the television screen surface by means of the reflector plates RF L ,RF R and the acoustic lenses L L ,L R . Referring to figure 6, showing the right-side loudspeaker SP R and a near-by region, sound waves radiated from the loudspeaker SP R are transmitted through the reflector plate RF R and the acoustic lens L L , comprised of mid plates (lens plates) L R 1, L R 2 and L R 3, and thereby modified in their travelling and diffusing directions, as indicated by sound waves W1 to W4. A sound wave W5, which is not transmitted through these reflector plates RF R or the acoustic lens L R , is radiated to outside through a meshed plate M R having a large number of orifices in the form of a netting or a honeycomb. It is noted that the reflector plate RF R is disposed so as to overlie, as viewed from the front, at least a inner region of the voice coil VC of the associated loudspeaker drive unit, as shown in figure 7 showing the projection of the reflector plate on the front sound radiating surface of the loudspeaker SP R . By arranging the reflector plate RF R so as to overlie at least the inner space of the voice coil VC, the mid to high frequency sounds, radiated from the central region of the loudspeaker SP R , that is the voice coil VC and the near-by region, and exhibiting high directivity with respect to the front surface of the loudspeaker SP R , are reflected by the reflector plate RF R so as to be modified in their proceeding direction. The reflector plate RF R is so oriented that the sound reflected thereby is directed forwardly of the television screen surface. If the entire sound radiating surface of the loudspeaker SP R is covered by the reflector plate RF R , the sound undergoes suppression and deterioration of sound quality. Given this consideration, the area of the sound radiating surface of the loudspeaker SP R covered by the reflector plate RF R is selected in the present embodiment to be approximately 20% to 70% and preferably 30% to 60% of the total sound radiating surface of the loudspeaker SP R . In addition, the area of the central region of the sound radiating surface of the loudspeaker SP R covered by the reflector surface RF R is preferably about twice the area of the inner space of the voice coil VC. Meanwhile, the reflector plate RF R may be designed so that its angle of orientation may be modified as desired for changing the direction of sound reflection in a desired manner. By using the above described reflector plate RF R , the sound radiated from the loudspeaker SP R , in particular, the mid to high frequency sounds which exhibit greatest directivity, may be radiated in a forward direction from the television screen surface, while being also directly radiated to outside by means of the meshed plate M R , without producing sound suppression. On the other hand, the low frequency sounds from the loudspeaker SP R are radiated to the outside by means of the reflector plate RF R and the acoustic lens L R , while being also radiated directly to outside by means of the meshed plate M R , similarly to the mid to high frequency sounds. Since low frequency sounds directly radiated to outside by means of the meshed plate M R are also turned round towards the front side of the screen surface to produce the low frequency sound producing the sense of ambience and compatibility with the displayed picture. It is noted that the reflector plate RF R may be molded of synthetic resins exhibiting high surface hardness and low inner losses, such as acrylonitrile-butadienestryrene (ABS) or styrene. In this manner, the mid to high frequency sound may be reflected effectively. Figure 8 shows the loudspeaker SP R and the reflector plate RF R actually built into the loudspeaker unit which is viewed from the front side of the loudspeaker SP R . In figure 8, DT R indicates a duct for taking out the sound within the loudspeaker box BX R to outside. The acoustic lens L R is used for controlling sound directively, that is, the direction and diffusion of the emitted sound. Specifically, the direction of the proceeding sound may be modified as a function of the length of the gap between the mid plates (lens plates) L R 1, L R 2 and L R 3, that is, the distance between the inlet and the outlet of the sound or the length of the sound path. In addition, a semicircular notch C is provided in a central region of each of the mid plates L R 1, L R 2 and L R 3 for expanding the sound from the loudspeaker SP R , that is, for converting the planar wave into a cylindrical wave or a spherical wave. It is noted that, considering the sound emanating from the loudspeaker SP R in figure 6, the sound wave W1 schematically represents the sound wave travelling through a space between the mid plate L R 1 and the wall surface of the cabinet towards the Braun tube BR, the sound wave W2 the sound wave travelling through the space between the mid plates L R 1 and L R 2, the sound wave W3 the sound wave once reflected by, for example, the reflective plate RF R to travel subsequently through the space between the mid plates L R 2 and L R 3 and the sound wave W4 the sound wave once reflected by the reflector plate RF R to travel subsequently through the space between the mid plate L R 3 and the outer wall surface of the cabinet CT. However, the sound waves W1,W2 may be occasionally reflected by the reflector plate RF R , while the sound waves W3,W4 may be transmitted directly through the gaps of the acoustic lens without having been once reflected by the reflector plate RF R . The sound direction may be changed as desired by changing the length of each sound duct of the acoustic lens L R . For example, with the mid plate L R 1 of the maximum length, the mid plate L R 3 of the minimum length and the mid plate L R 2 of an intermediate length, the sound emanating from the acoustic lens L R is directed towards the centre of the television screen surface. On the other hand, by reversing the relation of the sound duct lengths, the sound from the acoustic lens L R is directed away from the centre of the television screen surface. The sound direction may also be changed by changing the mounting angles of the mid plates. With the use of the above described acoustic lens L R , it becomes possible to produce the expanded sound with improved directivity by aligning the wave fronts of the mid to high frequency sounds which are strongly directive and radiated in the form of an acute beam. Meanwhile, the sound radiated towards the front side FW and the sound surrounding the television receiver SW are shown schematically by chain-dotted lines in figure 5. The acoustic lens L R and the meshed plate M R are shown assembled to the cabinet CT in figure 10 which is a perspective view partially broken away. With the above described television receiver loudspeaker unit arranged by arranging the loudspeakers SP L ,SP R on the rear lateral sides of the Braun tube BR, the sound radiating surfaces or gauges of the loudspeakers SP L ,SP R and the capacities of the magnetic circuit and the loudspeaker boxes BX L , BX R may be enlarged to enable the sound quality of the low frequency sounds, for example, to be improved. On the other hand, by reflecting at least a portion of the sound from the loudspeakers SP L ,SP R by the reflector plates RF L ,RF R and radiating the sound towards the front side of the television screen surface by the acoustic lenses L L , L R , the forward sides of which are arranged substantially on the same surface as the television screen surface, the sound from the loudspeakers SP L ,SP R above all, the strongly directive mid to high frequency sound, may be radiated towards the front side of the television screen surface to provide a more definite sound image and more expanded mid to high frequency sounds. Besides, since the sound from the loudspeakers SP L ,SP R is radiated directly to outside through the meshed plates M L ,M R for preventing sound suppression as well as providing a sense of ambience having an extended sound field and producing low frequency sound compatible with the displayed picture. Meanwhile, the television receiver of the present embodiment is shown in perspective in figure 11, partly broken away, in which the sound from the loudspeaker SP R is radiated not only forwardly but also laterally of the television screen surface, as indicated by chain-dotted lines therein.

Claims: A loudspeaker unit of a television receiver comprising loudspeaker means (SP L , SP R ) provided rearwardly of the television screen surface, sound reflector means (RF L , RF R ) for reflecting at least a portion of the sound from said loudspeaker means substantially in a forward direction from said television screen surface, characterised by acoustic lens means (L L , L R ) provided on a surface substantially coplanar with said television screen surface for controlling the radiating direction of the sound. A loudspeaker unit as claimed in claim 1, wherein said loudspeaker means comprise a left side speaker (SP L ) and a right side loudspeaker (SP R ) for stereophonic and/or monaural sound reproduction. A loudspeaker unit as claimed in claim 2, wherein said left and right side loudspeaker (SP L , SP R ) are arranged at an obtuse angle with respect to the television screen surface. A loudspeaker unit as claimed in claim 1, 2 or 3, wherein said sound reflector means (RF L , RF R ) form a part of a cabinet (LT) of the television receiver. A loudspeaker unit as claimed in any one of claims 1 to 4, wherein said sound reflector means (RF L , RF R ) covers an area about 30% to 60% of the entire sound radiating surface of said loudspeaker means (SP L , SP R ). A loudspeaker unit as claimed in any one of claims 1 to 4, wherein said sound reflector means (RF L , RF R ) covers an area of about 20% of 70% of the entire sound radiating surface of said loudspeaker means (SP L , SP R ). A loudspeaker unit as claimed in any one of claims 1 to 6, wherein said loudspeaker means (SP L , SP R ) are enclosed within associated loudspeaker boxes (BX L , BX R ).

Inventors: KOIZUMI HIROSHI C O SONY CORPO, KOIZUMI, HIROSHI, C/O SONY CORPORATION
Applicants: SONY CORP, SONY CORPORATION
Application year: 1991
Main classification: H04R5
IPC codes: H04R1, H04R5, H04N5