Abstract: A detensioning mask frame assembly for a cathode-ray tube including a subframe constructed of support members that provide a support structure for mask holding blades is disclosed. The support members have different temperature coefficients of expansion, such that when heated, the support members are deflected with different thermal expansion rates causing the mask holding blades to move toward each other, and as such, relieve tension from the mask.

Abstract: A cathode-ray tube having a luminescent screen on a faceplate panel and a tension mask assembly, wherein the assembly comprises a pair of support blades for supporting a tension mask. The tension mask has a pair of mask borders each being fixed to a respective support blade and a plurality of strands extending between the mask borders. The mask further comprises cross wires extending generally perpendicular to the strands on a screen facing side and at least one shield assembly extending between and attached to the mask borders. The shield assembly has a sheath extending along one side of the mask in contact with at least one strand and a shield attached to the cross wires of the mask in overlapping relation to the sheath.

Abstract: Shadow mask in a flat cathode ray tube having a damping wire fastened across a no-hole region between adjacent lines of beam pass through holes formed on a vertical line in the shadow mask for damping vibration of the shadow mask, including means for limiting a position of the damping wire on the no-hole region of the shadow mask, thereby enhancing a damping effect to improve a picture quality, and permitting to simplify a fabrication process and cut down a production cost.

Abstract: A cathode ray tube including a pair of supports arranged in parallel facing each other and a shadow mask acting as a color selection electrode including a large number of apertures. The shadow mask is stretched and held by the supports in a state in which tension is applied by the supports. In the shadow mask before being stretched onto the supports, the shapes of the apertures are varied so that the width of the apertures in the middle portion in the direction in which tension is to be applied narrows gradually from the central portion towards the both end portions in the direction parallel to the longitudinal direction of the support. Thereby, the shapes of the apertures can be made to be uniform over the entire surface in a state in which the shadow mask is stretched. As a result, a cathode ray tube with less color unevenness can be provided.

Abstract: The invention provides a tension mask support frame assembly having a pair of support blade members attached to a frame. The support blade members are attached to opposite sides of the frame at a central location whereby each support blade member has a pair of distal ends extending from the central attachment point. A damping scrubber is disposed in the space between the support blade member and the frame near a distal end of the support blade members. Vibrations in the tension mask are thereby reduced through the transfer of the vibrations to the frame through rubbing action of the damping scrubbers.

Abstract: The present invention provides a color cathode-ray tube that can attenuate vibration of an entire shadow mask positively with a simple structure. The color cathode-ray tube comprises a frame-shaped mask frame and a shadow mask in which many apertures are formed in a flat plate, the shadow mask being stretched and fixed in the mask frame in a condition in which a tension force is applied in one direction. The amplitude in the end portions of the shadow mask is not less than a certain amount relative to the amplitude in the center portion of the shadow mask, in a resonance of the shadow mask caused by a vibration propagated to the color cathode-ray tube. Furthermore, by providing vibration attenuators at the end portions of the shadow mask, vibrations at the end portions of the shadow mask are attenuated as the side surfaces of the shadow mask slide on the vibration attenuators. Thus, vibration of the entire shadow mask can be extinguished positively.

Abstract: The invention relates to a tension mask frame for a CRT having a generally rectangular support frame to which a peripheral portion of a tension mask is attached. The support frame has at least a long side and a short side. One side extends along an outer edge of the mask and protrudes inward toward the outer edge of the mask. The short side is attached to the long side to form a closed corner portion between the long side and short side of the support frame. The closed corner portion is used to suspend the mask within a panel portion of the color cathode ray tube.

Abstract: A cathode ray tube has a tensioned mask supported by a support frame. The tension mask being susceptible to vibration and adapted for mounting in tension within the cathode ray tube. The tension mask includes damper wire support springs attached to, and extending from, opposite sides of the tension mask support frame. The damper wire support springs having a compliance section supporting a damper wire in contact with and across the surface of the tension mask for damping vibrations in the mask.

Abstract: The invention relates to a tension mask frame assembly for a CRT having a substantially rectangular mask support frame. The mask support frame has a pair of long sides extending about a central major axis and a pair of short sides extending about a central minor axis. On at least one pair of these sides, a midsection is disposed between and is continuous with two end sections. The midsection is made of a material having a coefficient of thermal expansion which is less than a coefficient of thermal expansion of the end section material. A tension mask is supported to the mask support frame at attachment points adjacent the pair of sides having the midsection.

Abstract: A cathode ray tube includes a pair of plate members (7) facing each other, a pair of supporters (14) adhered to the respective plate members (7) to support the plate members (7), and a shadow mask (6) adhered to the respective plate members (7) while being applied with tensile force. The supporters (14) have crank-shaped steps (15) formed to protrude toward the shadow mask (6). Thereby, an internal moment of a shadow mask structure can be decreased, and thus, displacement of the shadow mask (6) in the axial direction is suppressed even when the shadow mask (6) is expanded by heat generated by impact of electron beams, and q-value deviation is suppressed as well. Moreover, since the crank-shaped steps (15) are helpful in blocking a transverse clearance with a ferrous material, the magnetic properties can be improved.

Abstract: A cathode ray tube has a tensioned mask supported by a support frame. The tension mask being susceptible to vibration and adapted for mounting in tension within the cathode ray tube. The tension mask includes damper wire support springs attached to, and extending from, opposite sides of the tension mask support frame. The damper wire support springs having a compliance section supporting a damper wire in contact with and across the surface of the tension mask for damping vibrations in the mask.

Abstract: A shadow mask includes a mask body having a principal mask surface with electron beam passage apertures, a skirt portion, and long and short axes, and a mask frame attached to outside the skirt portion. The mask frame has a coefficient of thermal expansion higher than that of the mask body. The skirt portion includes first and second tongue portions situated on the short and long axes, respectively. Each of the first and second tongue portions is fixed to the mask frame. The mask body is formed to fulfill relations given by (Ca·Wb)<(Cb·Wa), and V<H, where Ca and Wa are the length and width of the first tongue portion, respectively, Cb and Wb are the length and width of the second tongue portion, respectively, H and V are the length of the principal mask surface in the directions of the long and short axes, respectively.

Abstract: The present invention provides a tension mask for a cathode-ray tube. The tension mask has an active aperture portion formed by a plurality of parallel strands extending between cantilevers on opposed sides of a mask support frame. The tension mask further comprises border shields mounted over each end of the frame cantilevers, whereby the strand ends are held to the cantilevers in a predetermined spaced-apart relationship. The border shields on opposing sides of the frame extend toward the active aperture portion of the tension mask and is substantially aligned with the screen matrix of the CRT. The tension mask has a lower coefficient of thermal expansion than that of the mask frame, cantilevers, and border shield.

Abstract: A lightweight cathode ray tube is formed by reducing a cross-sectional area on the apeture grill tapes in the aperture grill. One exemplary embodiment of the reduced cross-sectional area aperture grill tape includes a central longitudinal channel in a side of the aperture grill tape that faces away from the screen. The reduction in cross-sectional area reduces a linear density of the tape thereby decreasing the tension required by the frame. As each of the aperture grill tapes includes this central longitudinal channel, the weight of the overall aperture grill is significantly reduced and the aperture grill frame weight is reduced due to the lower aperture grill tension. A method for producing the reduced cross-sectional area aperture grill tape is possible without significantly increasing the cost of manufacturing the aperture grill tape.

Abstract: A color display tube (1) is disclosed with an improved suspension of the color selection electrode (12). In order to have a color display tube with good properties of, for instance, color purity, it is of eminent importance that the color selection electrode (12) has and excellent positional stability. Especially wide screen tubes seem to be more sensitive to external shocks by which the color selection electrode (12) may shift and cause discolorations. The positional stability of the color selection electrode (12) can be improved by decreasing the friction between the color selection electrode (12) and the supporting elements (17) in the display window (3) of the color display tube (1). This is achieved by applying a supporting element (17) with a free end portion (22) having a small diameter and by applying a low force between the suspension means (20) and the supporting elements (17).

Abstract: A skirt portion of a mask body includes cut portions. The width of the cut portions along the minor or major axis ranges from 0.10×L to 0.45×L, where L is the distance from an end of the minor or major axis to a diagonal end, and the height of the cut portions along the tube axis is equal to 5% to 40% of the height of the skirt portion along the tube axis in a region near the minor or major axis.

Abstract: A color CRT suppresses deformation of the main shadow mask surface after fastening the shadow mask to the mask frame. Numerous substantially rectangular grooves or substantially circular recesses are formed in the damper part disposed to the shadow mask skirt so that the bending strength in the circumference direction of the skirt is greater than the bending strength in the direction parallel to the tube axis.

Abstract: In a color cathode-ray tube with a shadow mask stretched and held by supporters while being provided with a tensile force, a member with a substantially L-shaped cross-section is used for each of the supporters, which is obtained by forming of a strip plate material having a middle part and thinner thickness-deviation portions on both sides of the middle part by rolling of a metal material; and then bending and deforming of the strip plate material in its width direction by roll forming to form a bent and deformed portion in the middle part. The supporter obtained by such a method can be reduced in weight while maintaining substantially the same strength as that of a conventional product, can be processed economically in relatively simple steps, and has less thickness variation. Therefore, an inexpensive color cathode-ray tube having stable qualities and causing less color unevenness can be provided.

Abstract: A color selection apparatus for a cathode ray tube includes an iron mask having a longitudinal axis and a short axis and a frame coupled with the mask and tensing the mask in one direction of the longitudinal and short axes.

Abstract: Panel/shadow mask assembly including a substantially flat panel having an effective surface with a coat of fluorescent material thereon, a rail fastener fitted to a periphery of the panel wherein a surface of the rail fastener on a side of the effective surface of the panel has a radius of curvature, and a shadow mask fixed to the rail fastener under pretension, thereby doubling a foreign matter washing efficiency and preventing a quality deterioration of the flat cathode ray tube.

Abstract: A color cathode ray tube includes a shadow mask having an apertured portion, an imperforate portion and a skirt portion. The shadow mask of an iron-nickel alloy is suspended within a support frame, has a descending step portion around the imperforate portion, the skirt portion which is fitted in the support frame is integral with the descending step portion, is provided with plural beads parallel with a height of the skirt portion and protruding inward. The descending step portion satisfies one of conditions (a)-(c) of (a) its height is from 30% to 501 of H0, (b) its width is from 65% to 80% of W0, or (c) its height H and width W are from 30% to 50% of H0 and from 65% to 80% of W0, respectively, where H0 and W0 are its height and width at centerlines of long and short sides of the skirt portion, respectively.

Abstract: A tension mask frame assembly for a color cathode-ray-tube including a frame having four respective sides, two of the sides paralleling each other and having insert receiving brackets for supporting strand termination inserts therein and vertical mask strands welded to said termination inserts. The strands have a plurality of cross-wires extending perpendicular to the strands and attached thereto by a conductive bonding material. The wires and termination inserts are composed of materials having a first coefficient of thermal expansion. The frame and receiving brackets are composed of materials having a second coefficient of thermal expansion. The termination inserts thermally expand and contract independently of the frame and receiving brackets, whereby movement of the strands in the horizontal dimension is controlled by thermal expansion and contraction of the termination inserts and cross-wires.

Abstract: The color cathode ray tube according to the present invention can improve the brightness without compromising strength by making the bridge width in one-dimensional tension type shadow mask narrower to a certain degree. The color cathode ray tube has a color selection electrode, the color selection electrode including a pair of supports facing each other; a shadow mask provided with a plurality of slot apertures, the shadow mask being stretched and fixed by the pair of supports; and elastic members arranged between the supports, and holding the supports. Bridges between vertically adjacent slot apertures are formed on the shadow mask. Defining the bridge width W as the largest vertical width of a bridge, the narrowest bridge width Wmin is in a range of 3-10% of a vertical pitch of the slot apertures. With this configuration, the necessary strength can be ensured, and the brightness can be improved without compromising strength, because the bridge widths W can be made narrower.

Abstract: A color selection apparatus for a cathode ray tube (CRT) is disclosed. The color selection apparatus includes a frame having a pair of supporting members disposed in parallel and spaced away from each other and a pair of elastic members disposed between and coupled to the supporting members, and a mask coupled to the supporting members and provided with a plurality of beam-passing apertures. Each of the elastic members is formed in a continuously nonlinear-shape in its longitudinal direction.

Abstract: The invention provides a tension mask support frame assembly having a pair of support blade members attached to a frame. The support blade members are attached to opposite sides of the frame at a central location whereby each support blade member has a pair of distal ends extending from the central attachment point. A damping scrubber is disposed in the space between the support blade member and the frame near a distal end of the support blade members. Vibrations in the tension mask are thereby reduced through the transfer of the vibrations to the frame through rubbing action of the damping scrubbers.

Abstract: A shadow mask support frame for a cathode-ray color display tube of generally rectangular shape in top plan view. The shadow mask support frame includes two end upstands, which are located opposite each other and which are intended to support a shadow mask, and two lateral upstands, which are intended to keep the end upstands apart or separated from each other. The end upstands and the lateral upstands are of generally tubular shape and constitute an almost continuous closed hollow body containing at least one plane closed line located entirely inside the hollow body and passing inside each of the end and lateral upstands. It may be produced by folding a single metal strip or by fitting two drawn shells together.

Abstract: A split foot damper for damping vibrational energy on a tension mask having a border with an edge. The apparatus has a first element having a first portion in moveable contact with a surface of the border and a second portion in moveable contact with the edge of the border, and a second element having a third portion in moveable contact with the surface of the border and a fourth portion in moveable contact with the edge of the border, where the two elements are connected to each other at a point that is affixed to the surface of the border. As the mask vibrates, the vibrational energy is transferred to the split foot damper, wherein vibrational energy is dissipated as the portions of the split foot damper makes contact against the surface and edge of the border.

Abstract: The invention relates to a tension mask frame assembly for a CRT having a substantially rectangular mask support frame. The mask support frame has a pair of long sides extending about a central major axis and a pair of short sides extending about a central minor axis. On at least one pair of these sides, a midsection is disposed between and is continuous with two end sections. The midsection is made of a material having a coefficient of thermal expansion which is less than a coefficient of thermal expansion of the end section material. A tension mask is supported to the mask support frame at attachment points adjacent the pair of sides having the midsection.

Abstract: The present invention discloses a mask frame assembly in a cathode ray tube which is capable of minimizing a Howling phenomenon and preventing local wrinkles of a shadow mask by optimizing positioning of compression of the mask frame assembly.

Abstract: A stud for mounting a shadowmask in a cathode ray tube comprises a tubular body symmetrically arrayed about a longitudinal axis and having a given diameter and a spherical projection fixedly mounted upon one end of the tubular body. The sphere has a diameter greater than the given diameter. In alternate embodiments the tubular body can have plural diameters.

Abstract: A color cathode ray tube including a shadow mask assembly and an inner shield provided for the shadow mask assembly which are disposed within the tube. The shadow mask assembly includes a substantially rectangular shadow mask, a substantially rectangular mask frame, and a spring for mounting the shadow mask assembly in the panel of the cathode ray tube. The shadow mask has a curved surface having electron beam passing holes and a skirt folded from the margin of the curved surface and extending in a tube axis direction. At least one of the major and minor sides of the substantially rectangular shadow mask has a curvature convex to the tube axis with corners thereof being round and at least one of the major and minor sides of the substantially rectangular mask frame is linear or has a curvature concave to the tube axis with corners thereof being round.

Abstract: A mask-frame assembly for a cathode ray tube includes a mask frame having a front portion and a side portion perpendicularly extending from the edge of the front portion and having notches, and a shadow mask having a front screen portion and a skirt portion welded to non-notched parts of the side portion of the mask frame. A portion of the skirt portion is not welded to the mask frame but exposed outside the mask frame so as to improve a thermal exchange.

Abstract: A color cathode-ray tube is provided with constitution between a shadow mask electrode and a frame body such that difference of expansion and contraction between the shadow mask electrode and the frame body according to heat brings no-picture quality deterioration with practical cost. The shadow mask electrode made of metal whose thermal expansion rate is low. The shadow mask electrode is supported by a shadow mask electrode supporting body made of metal whose thermal expansion rate is approximately the same as that of the shadow mask electrode. The shadow mask electrode supporting body is supported by a frame body made of metal whose thermal expansion rate is different from that of the shadow mask electrode.

Abstract: A color selection means is described in which the mask (50) is stretched under tension and connected to a support frame. The support frame accurately determines the mask contour, while the mask is connected to this frame in a flexible way by mechanical means so that differences in expansion behavior of the mask and the frame can be handled. These connection means can be either lugs or resilient elements (59). Such a color selection means may be used in a color display tube having an at least substantially flat display screen.

Abstract: A cathode ray tube includes a tension mask attached to a rectangular mask frame assembly that has two long sides paralleling a central major axis thereof and two short sides paralleling a central minor axis thereof. The two long sides are disposed at generally a right angle with respect to the two short sides with each of the sides connected to form a continuous generally planar support frame having an inner and outer peripheral surface. The support frame is formed of a material having a first coefficient of thermal expansion and includes a detensioning member formed of a second coefficient of thermal expansion on the peripheral surface of at least one side of the frame to facilitate detensioning of the mask.

Abstract: A color selection apparatus for a cathode ray tube. A mask frame having a pair of supporting members is disposed in parallel and spaced away from each other. A pair of elastic members is disposed between and coupled to the supporting members. A tensioned mask is coupled to the supporting members and is provided with a plurality of beam-passing apertures. A spring assembly includes a hook having a frame fixing part fixed on the mask frame and a spring fixing part and a spring fixed to the spring fixing part. The hook has a cut-away portion defined by cutting a portion of the frame fixing part. The cut-away portion forms a welding portion for welding the hook to the mask frame.

Abstract: A color picture tube (10) has a tensioned mask (24) supported by a support frame (28) mounted within the tube. The mask has a significantly lower coefficient of thermal expansion than the frame. Intermediate members (48) are located between the mask and the frame. The intermediate members are of a material having a coefficient of thermal expansion similar to that of the mask. The frame has elongated tabs (46) extending therefrom. Each of the tabs is attached at one end thereof to the remaining portion of the frame. The distal ends of the tabs are welded to the intermediate members.

Abstract: A mask-frame assembly for a cathode ray tube includes a mask frame having a front portion and a side portion perpendicularly extending from the edge of the front portion and having notches, and a shadow mask having a front screen portion and a skirt portion welded to non-notched parts of the side portion of the mask frame. A portion of the skirt portion is not welded to the mask frame but exposed outside the mask frame so as to improve a thermal exchange.

Abstract: In the structure of the present invention, there can be provided a cathode ray tube in which deviation in the trajectory of the electron beams by the leakage magnetic field from the mask frame (1) is decreased by using a polygonal mask frame (1) in which the relative magnetic permeability of longer side members (31) out of two side members adjacent to each other at the joint portion of the mask frame (1) is the same as or larger than the relative magnetic permeability of the other side members (21). Thus, the significance of the present invention in industrial terms is large.

Abstract: An apparatus and method for terminating crosswires on a tension focus mask. The apparatus includes a busbar support rail aligned with a busbar attached by a set of spacers and busbar support clips, a termination assembly and a set of termination spring clips. The method includes aligning the busbar support rail with the busbar, attaching busbar support clips to the busbar, affixing spacers to a side of the busbar and then placing a termination strip along the side of the spacer. After all the elements have been aligned, crosswires are drawn across the top of the busbar and attached to the termination strip. An electrical adhesive is applied over the busbar top and allowed to cure. After the electrical adhesive cures, the crosswires between the busbar and the termination strip are cut so as to provide electrical isolation.

Abstract: A color cathode ray tube can reduce a warp amount derived from a spring back after shaping a shadow mask and can suppress the deformation of a main surface of the shadow mask after fixedly securing the shadow mask and a mask frame to each other. The color cathode ray tube includes tongue portions which are protruded from distal ends of skirt portions of the shadow mask and a plurality of stress absorption holes are formed in the tongue portions.

Abstract: The present invention provides an improved tension mask frame assembly 10 in which mask support members 40 are provided with side walls 42, 46 and a back wall 44 that are held together primarily by means of either tabs formed along an edge of the back wall 48 received into respective apertures 50 in the side wall 42 or by means of a ridge 69 formed in the side wall 62 which abuts the back wall 64.

Abstract: The present invention describes the details of a flat mask before tension is applied, an assembling method of that flat mask, and a tension mask assembly manufactured by using that method in order to obtain satisfactory thermal expansion, uniform stress distribution and linearity. The flat mask includes an apertured portion and supporting ends surrounding the apertured portion. The apertured portion comprises a plurality of concave pin-cushion type or convex barrel type strips, a plurality of real bridges connecting strips and dividing slots, and dummy bridges formed in the slots. The short supporting ends have the same width along a longitudinal direction and are formed to have the same curvature as the strips facing the supporting ends. The short supporting ends are preferably half-etched in order to make the volume of material removed from the short supporting ends greater than the volume of material removed from the apertured portion.

Abstract: The present invention provides an improved support blade structure 40 for use on a tension mask frame assembly 10. The support blade structure 40 is formed of a material having a first coefficient of thermal expansion and includes fastening portions 51 and an insert member 60 connected at a generally central location to the support blade structure 40. The insert member 60 is formed of a material having a second coefficient of thermal expansion and has a plurality of apertures 62, 64 extending in a row along its length. The aperatures 62, 64 are dimensioned to be larger than the fastening portions 51 passing therethrough to loosely connect the insert member 60 to the support blade structure 40. This allows the insert member 60 to be connected at the center while it's ends are free to slide relative to the support blade structure 40 during thermal cycling.

Abstract: A color selection apparatus for a cathode ray tube. A mask is formed having a long axis and a short axis. A frame supports the mask in one of a long axis direction and a short axis direction. The mask has a plurality of strips separated by a predetermined distance. A plurality of first beam apertures are formed as single long slits between the strips in a center portion of the mask. A plurality of second beam apertures are formed on outer portions of the mask to both sides of the center portion of the mask. The second beam apertures are divided into a plurality of individual units within a single column by real bridges and at least one dummy bridge for each individual second beam aperture unit. The at least on dummy bridge extends inwardly from the strips but does not cross completely through the individual second beam aperture unit.

Abstract: A shadow mask for a cathode ray tube includes through-holes defined by first and second recessed formed at first and second surfaces of the shadow mask, respectively. Each through-hole has a first wall farther away from a center of the shadow mask than a second wall thereof. The second recess has a smaller size than that of the first recess. The first wall is formed of a first wall portion defined by an inner surface of the first recess and a second wall portion defined by an inner surface of the second recess. The second wall portion of through-holes located at a peripheral region of the first region has a configuration such that electron beams reflected therefrom are directed to an inner surface of the first recess to thereby reduce electron beams reflected therefrom in directions different from a direction in which the electron beams are originally directed before the electron beams enter the shadow mask.

Abstract: A mask assembly for a cathode ray tube includes a tension mask having an effective portion formed with strips spaced apart from each other forming slots there between and a non-effective portion surrounding the effective portion. A mask frame includes a pair of supporting members along long sides of the tension mask and a pair of elastic members spacing the supporting members from each other by a predetermined distance. Vibration damping members damp vibration of the tension mask, where the vibration damping members are tensioned in a longitudinal direction to pressurize the non-effective portion.

Abstract: A cathode ray tube includes a pair of plate members (7) facing each other, a pair of supporters (14) adhered to the respective plate members (7) to support the plate members (7), and a shadow mask (6) adhered to the respective plate members (7) while being applied with tensile force. The supporters (14) have crank-shaped steps (15) formed to protrude toward the shadow mask (6). Thereby, an internal moment of a shadow mask structure can be decreased, and thus, displacement of the shadow mask (6) in the axial direction is suppressed even when the shadow mask (6) is expanded by heat generated by impact of electron beams, and q-value deviation is suppressed as well. Moreover, since the crank-shaped steps (15) are helpful in blocking a transverse clearance with a ferrous material, the magnetic properties can be improved.

Abstract: In the case of shadow masks which are pretensioned vertically and horizontally and the horizontal pretension of which is produced by stretching in the vertical direction, an expensive mask material having a low coefficient of thermal expansion can only be replaced by a less expensive mask material, such as iron, if the tension forces which can be produced for pretensioning the mask in the horizontal direction are markedly higher than the hitherto produced forces. For this purpose, the outer boundaries of the shadow-mask sides which are not connected to the mask frame are implemented such that they have a curved shape and a higher strength. In this way, it is possible to produce in a direction perpendicular to the stretching direction tension forces which are higher than the hitherto produced forces.

Abstract: A color selecting apparatus for a cathode-ray tube including a frame, and a mask supported in the frame with tension along a minor axis, where the mask having a rectangular hole part formed with a plurality of electron beam-passing apertures, a non-hole part surrounding the hole part, and a pair of vibration attenuating members attached at both ends of the surface of the non-hole part, facing each other along a major axis, for attenuating vibration waves which transmit along the major axis. The vibration attenuating members are made of a metal having a greater mass than the non-hole part, and attached by spot-welding so that they are away from the non-hole part by a predetermined gap at every portion except the welding points. Therefore, the vibration attenuating members serve as a damper to attenuate vibrations which are transmit in the major direction, particularly vibrations generated by the speakers.