Abstract: There is provided an acoustic vibratory plate having at least first to third laminated bodies layered. In the acoustic vibratory plate, the first and third laminated bodies are formed of a polymer material, and the second laminated body is formed of a polymer material different from the polymer material forming the first and third laminated bodies in dynamic internal loss.

Abstract: A method for manufacturing an electroacoustic transducer diaphragm of a multilayered structure which includes a first diaphragm layer made from a synthetic resin material and molded into a predetermined shape through injection molding, and a second diaphragm layer laminated in close contact with the first diaphragm layer and made from a material differing from that of the first diaphragm layer, the method includes inserting the second diaphragm layer into a mold for injection molding, and forming the first diaphragm layer integrally with the second diaphragm layer by injection foam-molding within the injection mold.

Abstract: There is provided an acoustic diaphragm which includes a diaphragm base material composed of a paper article comprised of fine mica flakes, pulp fibers, and polyvinyl alcohol fibers and formed to be a multi-cellular structure; and a sheet material combined with the paper article or the diaphragm base material.

Abstract: A loudspeaker diaphragm having light weight and an excellent balance between a rigidity and an internal loss, and a simple and inexpensive method for manufacturing such a diaphragm are provided. The loudspeaker diaphragm includes a base layer having a woven fabric of a polyethylene naphthalate fiber impregnated with a thermosetting resin, and optionally a thermoplastic resin layer and/or a thermoplastic elastomer layer. The polyethylene naphthalate fiber is preferably an untwisted fiber. A fiber/resin weight ratio in the base layer is preferably in the range of 60/40 to 80/20. Preferably, the thermoplastic resin layer has a finely foamed structure and an average diameter of a cell in the finely foamed structure is 10 to 60 ?m.

Abstract: A speaker diaphragm made of a resin containing a thermoplastic polymeric material is provided. The speaker diaphragm includes a changed portion formed on the diaphragm that is molded using the resin. The changed portion is formed by partially changing physical properties of the thermoplastic polymeric material for dispersing local vibrations based on a characteristic of local vibrations measured in advance.

Abstract: On one surface of a piece of wooden sheet, a cloth or paper is adhered to make an adhered sheet. An approximately V-shaped notch is provided on the adhered sheet, the adhered sheet is wetted to be softened, and a lubricant which acts to keep water is impregnated thereinto. Edge portions of the notch are overlapped, and the adhered sheet is tentatively molded in an approximately horn shape by a first hot press molding. The adhered sheet is then dried, impregnated with thermosetting resin, and half-dried. The adhered sheet is subject to a second hot press molding. A moisture-proof agent is applied on the adhered sheet, a center hole for a voice coil and periphery are removed to make a speaker diaphragm having a predetermined dimension and shape.

Abstract: A resin-molded component such as a loudspeaker diaphragm, in which rigidity is enhanced while light weight and high specific modulus of elasticity are maintained, is formed by applying carbon dioxide gas with a predetermined pressure to a thermoplastic resin in which crystallization is facilitated in the resin flowing direction to fill a mold. After the resin is filled, injection molding is performed by somewhat moving the mold to form five layers of: oriented minute-foaming layers, having approximately cylindrical foams, the length of which is twice the diameter thereof in the resin flowing direction in the mold, an unfoamed core layer positioned between both the foaming layers, and unfoamed skin layers formed on the front and rear surfaces.

Abstract: A piezoelectric electroacoustic transducer, including a plurality of piezoelectric layers deposited to define a deposited product, flexurally vibrates the deposited product by polarizing the entire piezoelectric ceramic layers in the same thickness direction and also by applying an alternating signal between external electrodes disposed on the front/rear major surfaces of the deposited product and an internal electrode disposed between the ceramic layers. A dummy electrode is provided between the ceramic layers outside the internal electrode via a gap, and a portion of the internal electrode is exposed at at least one side surface of the piezoelectric ceramic layers, while the dummy electrode is exposed at the other side surface of the piezoelectric ceramic layers. The external electrodes extend to the side surfaces other than the side surface at which the internal electrode is exposed.

Abstract: There is provided an electrically conductive damper device for a speaker in which local bending is reduced and break-downs of material of the damper and metallic wires incorporated in the damper are prevented, by additionally providing one or more sheets of damper fabric as a reinforcing damper 142 and by bonding it to a main damper 141 by way of various kinds of resin, in order to reinforce a neck portion of the electrically conductive damper. Further, properties of the damper can be adjusted by varying an outer diameter of the reinforcing damper 142, or by selecting the resin to be employed as an adhesive.

Abstract: A speaker includes a housing having a diffusion opening provided with a laser vibration diaphragm. The laser vibration diaphragm has reflective spatial patterns, so that the speaker may present multiple-image variations under different rays of light, thereby enhancing a viewing effect and aesthetic quality of the speaker. Thus, the laser vibration diaphragm may produce spatial variations by the difference of incident angles of the light, thereby obtaining a viewable strong sensation to the people, and thereby enhancing the viewing effect and aesthetic quality of the speaker.

Abstract: A structure of an acoustic diaphragm adapted to be used in a planar diaphragm speaker is provided. The structure includes a bottom carbon fiber layer and a top carbon fiber disposed on the bottom carbon fiber layer, wherein the fibers of the top carbon fiber layer and the fibers of the bottom fiber layer are parallel with each other.

Abstract: A loudspeaker diaphragm having light weight and an excellent balance between a rigidity and an internal loss, and a simple and inexpensive method for manufacturing such a diaphragm are provided. A loudspeaker diaphragm according to the present invention includes a base layer having a woven fabric of a polyethylene naphthalate fiber impregnated with a thermosetting resin, and optionally a thermoplastic resin layer and/or a thermoplastic elastomer layer. The polyethylene naphthalate fiber is preferably an untwisted fiber. A fiber/resin ratio in the base layer is preferably in the range of 60/40 to 80/20. Preferably, the thermoplastic resin layer has a finely foamed structure and an average diameter of a cell in the finely foamed structure is 10 to 60 &mgr;m.

Abstract: A molded foam resin, surface of which can be designed easily at low cost, a process for forming a molded foam resin, and a speaker diaphragm made of molded foam resin are provided, in which a molded foam resin is formed by injection molding of foaming agent-containing resin and has a foamed zone having a three layer-structure consisting of a foamed layer inside and a non-foamed layer outside and a non-foamed zone having a single layer-structure consisting of a non-foamed layer.

Abstract: A speaker includes a housing having a diffusion opening provided with a laser vibration diaphragm. The laser vibration diaphragm has reflective spatial patterns, so that the speaker may present multiple-image variations under different rays of light, thereby enhancing a viewing effect and aesthetic quality of the speaker. Thus, the laser vibration diaphragm may produce spatial variations by the difference of incident angles of the light, thereby obtaining a viewable strong sensation to the people, and thereby enhancing the viewing effect and aesthetic quality of the speaker.

Abstract: A structure of an acoustic diaphragm adapted to be used in a planar diaphragm speaker is provided. The structure includes a bottom carbon fiber layer and a top carbon fiber layer disposed on the bottom carbon fiber layer, wherein the fibers of the top carbon fiber layer and the fibers of the bottom fiber layer are parallel with each other.

Abstract: A method of producing cone diaphragm having color patterns includes steps of using a fiber-made thin sheet as a base material; printing the base material with a high molecular ink; soaking the printed base material in a high molecular resin material; or alternatively, first soaking the base material in the high molecular resin material and drying the base material, and then printing the base material wish the high molecular ink; so that the base material is coated with a layer of the high molecular resin to maintain a desired brilliance of the color patterns; drying the base material and positioning it in a high-temperature mold, so that the base material is molded into a cone having a predetermined shape; painting outer surfaces of the molded cone with a paint; and trimming the molded and painted cone to produce a finished cone diaphragm having color patterns.

Abstract: The invention proposes a contact connection for sound reproduction devices according to the flexural wave principle. Since the drive systems 21 of such installations require high current intensities and such current intensities could only be properly transmitted by massive contact connections which however hinder the flexural wave propagation, the object of the invention is to propose a contact connection which eliminates the problems of the state of the art, and which is also very easy to implement. To that end it is proposed that at least one of the two cover layers 12 and/or the core layer 11 contain conductive areas 17 which are connected to the lines 32 of a sound signal source. It is particularly advantageous if the conductive areas 17 can be manufactured together with the components that are also used to manufacture the core layer 11.

Abstract: An acoustic diaphragm arranged to face a driving device of a loudspeaker is disclosed. The acoustic diaphragm comprises at least one laminated structure, one of which includes a first carbon fiber layer, a glue layer formed on the first carbon fiber layer, and a second carbon fiber layer formed on the glue layer. The acoustic diaphragm of the present invention has small distortion of sound, less deformation by external force, better stereo, and sound quality, as compared with a conventional diaphragm.

Abstract: Disclosed is a piezoelectric diaphragm with a transparent piezoelectric member and a transparent electrode. Also disclosed is a portable electronic device that has a display means to display an image and a piezoelectric speaker having a transparent piezoelectric member and a transparent electrode. In this portable electronic device, the piezoelectric speaker is disposed in front of the display means.

Abstract: A molded foam resin, surface of which can be designed easily at low cost, a process for forming a molded foam resin, and a speaker diaphragm made of molded foam resin are provided, in which a molded foam resin is formed by injection molding of foaming agent-containing resin and has a foamed zone having a three layer-structure consisting of a foamed layer inside and a non-foamed layer outside and a non-foamed zone having a single layer-structure consisting of a non-foamed layer.

Abstract: The loudspeaker comprises a cone (2) and a beading (4) attached to the cone (2). The beading (4) is composed of a sprayable plastic layer which is soft in its solid state. The manufacture of the loudspeaker is facilitated by a process in which an open negative mold (16) is used in which the cone (2) is arranged and immobilized. Following this, the plastic is sprayed into the open negative mold (16) and the beading (4) is formed as a soft plastic layer which attaches itself to the cone (2).

Abstract: The invention presents a sound reproduction device which operates in accordance with the flexural wave principle. Such devices have in common that a panel 10 is provided in which flexural waves are produced by a drive arrangement 16. The drive arrangements 16 in the state of the art are connected to one of the surfaces of the panel 10 and are held by a support structure which functions as a countersupport. Such support structures either hinder the propagation of the flexural waves along the surface of the panel 10 and/or lead to an increase in the constructed depth of such a sound reproduction device. To avoid these disadvantages of the state of the art, the drive system 16 is located in a cutout 15 of the panel 10.

Abstract: A panel-form loudspeaker has a resonant multi-mode radiator panel which is excited at frequencies above the fundamental frequency and the coincidence frequency of the panel to provide high radiation efficiency through multi-modal motions within the panel, in contrast to the pistonic motions required of conventional loudspeakers. The radiator panel is skinned composite with a honeycomb or similar core and must be such that it has a ratio of bending stiffness to the third power of panel mass per unit area (in mks units) of at least 10 and preferably at least 100. An aluminum skinned, aluminum honeycomb cored composite can meet this more severe criterion easily.

Abstract: The invention herein of a standard-sized Vibrating Diaphragm speaker structure, primarily includes a stand with an enlarged opening in the front and a magnetic element in the rear, a cylinder inside a magnetic element, a spring panel sticking with a cylinder, and a Vibrating Diaphragm located on the enlarged opening of the stand. The inner face of Vibrating Diaphragm sticks with cylinder. The improved structure of the invention is characterized as that the surface of Vibrating Diaphragm is free of end fixture and it sticks with a foam washer, which is located at the lower portion of Vibrating Diaphragm and is stuck with an enlarged opening of a stand. Thus, the effective vibration area for a Vibrating Diaphragm is maximized and the output of sound magnitude for a speaker is enhanced. A foam washer substitutes the function of flexible movement for an end fixture of the invention of prior art to achieve normal sound output of a speaker.

Abstract: A composite loudspeaker diaphragm is disclosed having first and second substantially flat carbon fiber skins, and a honeycomb core sandwiched between the first and second carbon skins. In a preferred form, each carbon fiber skin comprises a sheet formed of primarily unidirectional carbon filaments bound together by an epoxy resin. In the preferred embodiment, the honeycomb core is formed of nomex, and is glued with epoxy to the first and second carbon skins, and then heated. The sandwich diaphragm is manufactured so that the direction of the carbon fibers of the cross plies of each outer skin are out of phase relative to each other, preferably in the range of approximately ninety degrees. The improved diaphragm is used in an flat-panel loudspeaker system having improved performance at higher frequencies.

Abstract: A diaphragm for speakers comprises a self-support, shaped body including a tightly woven synthetic polymer fiber cloth substrate which has, at least a diaphragm portion and edge portion shaped integrally with and extending from the diaphragm portion. The diaphragm portion of the cloth substrate had a polymer resin at least partially impregnated therein and the edge portion has a relatively flexible polymer material at least partially impregnated therein so that the edge portion is lower in stiffness than the diaphragm portion. The diaphragm-edge integral molding is fabricated by applying the respective types of polymers to the diaphragm and edge portions of the cloth substrate and subjecting the applied substrate to hot pressing in a mold capable of forming the integral molding. When applied as dynamic speakers, the integral molding exhibits a broad frequency band, low distortion rates and high sound quality.

Abstract: A seismic method and system for generating seismic source energy in marine geophysical operations. A slotted housing is moveable by the actuation of piezoelectric elements to generate high power, low frequency seismic source signals. When the piezoelectric elements are activated by electric power, displacement of such elements is enlarged by the slotted housing to generate a pressure pulse in the water. The invention permits single source pressure pulse generation having sufficient power and low frequency. The housing can be towed by a seismic vessel or can be integrated into a self-contained marine vehicle.

Abstract: A loudspeaker diaphragm is provided as an injection molded material including 50 to 80 weight % of a matrix resin of polyolefins and 20 to 50 weight % of flaky mica having an average aspect ratio of more than 10 and including at least 3 weight % or more of pearl mica. The matrix resin of polyolefins includes respective flakes of the flaky mica orientated in parallel to thereby improve the acoustic characteristics and concurrently the design appearance of the diaphragm. The design appearance of the diaphragm can have bright colors and a pearly luster.

Abstract: A loudspeaker vibrating diaphragm with has a foam layer and two un-foamed skin layers formed on both sides of the foam layer. The average foaming magnification including the foam layer and two un-foamed skin layers is 1.1-3.0. The average foaming magnification is the ratio of the thickness of the resin after foaming (which equals the sum of the thicknesses of the foamed layer and the two un-foamed layers) to the thickness of the resin before foaming. The foam layer contains foaming bubble cells which are formed with their longer axes arranged in the thickness direction of the diaphragm. The thickness of each un-foamed skin layer is 0.05-0.20 mm.

Abstract: A diaphragm for speakers comprises a self-support, shaped body including a tightly woven synthetic polymer fiber cloth substrate which has at least a diaphragm portion and edge portion shaped integrally with and extending from the diaphragm portion. The diaphragm portion of the cloth substrate had a polymer resin at least partially impregnated therein and the edge portion has a relatively flexible polymer material at least partially impregnated therein so that the edge portion is lower in stiffness than the diaphragm portion. The diaphragm-edge integral molding is fabricated by applying the respective types of polymers to the diaphragm and edge portions of the cloth substrate and subjecting the applied substrate to hot pressing in a mold capable of forming the integral molding. When applied as dynamic speakers, the integral molding exhibits a broad frequency band, low distortion rates and high sound quality.

Abstract: An acoustic diaphragm employed in a speaker or the like and a method for producing the acoustic diaphragm are disclosed. A diaphragm substrate is a diaphragm exhibiting air permeability such as a paper diaphragm. The substrate is processed with filling by microfibrilated pulp. For filling, the substrate is immersed in the liquid dispersion of the microfibrilated pulp and the pulp is deposited on the substrate under suction. When the microfibrilated pulp is deposited on the substrate under suction, any voids present in the substrate are closed by the microfibrilated pulp so that air tightness is improved without lowering the sound quality or detracting from desirable properties of the diaphragm, such as low density, high toughness and low losses.

Abstract: A planar-type loudspeaker incorporating a substantially planar diaphragm constructed from a pre-expanded cellular plastic material, such as polystyrene, in which separate portions of the diaphragm have different densities. The higher density portion is designed for the reproduction of high frequencies, and the lower density section is used for the reproduction of low frequencies. In one embodiment, the diaphragm is formed by laminating together a pair of diaphragm members having the different densities to define a single sound producing region, to which a single voice coil assembly is coupled. In another embodiment, the diaphragm is formed as a unitary, one-piece structure having separate but contiguous sound producing regions, each with its own density material and voice coil assembly for reproducing a specified frequency range of sound.

Abstract: Process for the preparation of films or diaphragms for acoustic applications, exhibiting improved vibration properties, and films or diaphragms obtained by this process, particularly diaphragms for electro-mechanical transducers, particularly for loudspeakers. The invention has for an object a process for preparing films or diaphragms for acoustic applications exhibiting improved vibration properties, consisting in preparing a dispersion, in a liquid, of at least one macropolymer, especially at least one synthetic macropolymer having at least 30,000 atoms in a molecule, adding, to the dispersion, a product capable of swelling said macropolymer and of transforming said dispersion in a gel of similar material, and drying sale gel or similar material by evaporating substantially all the liquid from the gel or similar material, thereby obtaining the film or diaphragm in the porous solid slate. NO DRAWING.

Abstract: The invention is intended to improve the durability and durability of a diaphragm of centrally convex form. A diaphragm comprises a substantially circular woven base fabric (1) formed of warp yarns (1a and 1a') radially extending in centrally convex form from the central region and weft yarns (1b) helically interwoven with the warp yarns (1a), and a rubber member (2) of centrally convex membrane form molded integrally with the base fabric (1).

Abstract: An acoustic diaphragm is obtained by forming micro-fibrillated cellulose into a web by a process similar to a paper-making process. The micro-fibrillated cellulose is the cellulose obtained by beating to the Canadian standard freeness of not more than 300 ml, or bacterial cellulose. Since the micro-fibrillated cellulose is poor in wet strength, it is reinforced by a reinforcement element and, in this state, is formed into the web on a wire screen. The reinforcement element may be detached after forming the web, or may be left laminated with the cellulose web so that the resulting composite product is used as the acoustic diaphragm.

Abstract: A diaphragm for microphones having a laminate structure which imparts damping characteristics to the diaphragm is disclosed. The laminate comprises upper and lower resilient layers composed of a plastic film. The upper and lower layers constrain a center layer composed of an elastomeric material having a high dissipation of vibratory shear motion. Manufacturing techniques for making such diaphragms are disclosed.

Abstract: A speaker diaphragm has a laminated construction in which a core layer is made of a porous diamond type wafer or wafers and sandwiched by a pair of surface layers made of diamond type material. Presence of numerous small pores in the core layer reduces the specific gravity of the entire diaphragm, thereby increasing efficiency in acoustic conversion. The porous construction of the core layer reduces internal loss of the diaphragm, and suppresses resonance in the treble range.

Abstract: A loudspeaker component is bonded to a diaphragm formed of an olefinic resin, by applying an adhesion primer to bonding positions of the component and/or the diaphragm, applying an adhesive to the bonding positions after the primer has cured, and superposing the component and diaphragm. An air curing unsaturated polyester resin is used as the adhesion primer.

Abstract: A speaker diaphragm includes a combined fiber paper made with crushed silk chips and a crushed bast fiber. In the preferred embodiment, the bast fiber is a natural Manila hemp fiber. The silk fiber contributes vibration damping to the diaphragm while the bast fiber contributes strength and stiffness. The crushed silk chips and the crushed bast are mixed with water to produce a slurry from which the water is drained to produce the combined fiber paper. In a further embodiment of the invention, a layer of a different material is disposed between two layers of the combined filter paper. The layer of different material is selected from a hard wound silk gauze, a glass fiber, a polyamid fiber and a carbon fiber.

Abstract: An improved audio transducer includes a diaphragm having a pair of cylindrically-shaped webs that provide greater bandwidth, reduced distortion and greater horizontal dispersion of sound. The audio output of the transducer is further improved by forming the diaphragm of a polyvinyl fluoride film. Other improvements include the use of damping pads to damp internal sound waves and damping strips on the diaphragm to minimize distortion at the resonant frequency of the transducer. In one alternative embodiment a laminated diaphragm is used to damp resonance in the high-frequency end of the transducer operating range.

Abstract: A membrane for a loudspeaker is designed so as to facilitate manufacture and to improve the tone of the loudspeaker. The membrane consists of a first plastic film (5a) which serves to retain the shape and a second plastic film (56) laminated to the first film which serves to damper partial oscillations. The membrane is particularly suitable as a conical membrane for a loudspeaker for a television receiver.

Abstract: There is a dynamic microphone comprising: a diaphragm which can vibrate by an acoustic wave and a voice coil which is joined to the diaphragm so as to transverse a magnetic field formed by the magnet and can vibrate integratedly with the diaphragm, wherein a number of peripheral treatment agents for damping are coated in a dot shape or a discontinuous stripe shape at intervals onto either one of the front surface and the back surface of the portion of the diaphragm excluding the center dome. With the above construction, a change in stiffness of the diaphragm by the peripheral treatment agents is extremely reduced, it is prevented that the diaphragm resonates at a special frquency, a sudden attenuation of the low frequency limit is prevented, and a low sound can be also certainly collected.

Abstract: A process for preparing a wholly carbonaceous integrated diaphragm for acoustic equipment use comprises blending under application of high shearing force a mixture of one or more kinds of organic high polymeric substances carbonizable on baking and powder of graphite with crystals high elastic modulus developed therein; extrusion-molding the uniformly blended and dispersed mixture through a profile extrusion die to give a core material with orientation along the direction of the extrusion and to be cut to a desired form; independently blending and sheeting under application of high shearing force the mixture with the organic powder oriented to high degree parallel to the direction of the surface of the sheet and further passing the sheet through a calendering roll to give a skin material in the form of a film or sheet; bonding said skin material on both sides of the core material by the use of such organic liquid composition that provides high yield of carbon residue on baking and then baking the resulting un

Abstract: A diaphragm for acoustic equipment wherein a surface-hardened layer of SiC film is formed on the surface of the diaphragm substrate comprising a completely carbonaceous film. Thus, the diaphragm for acoustic equipment having superior acoustic characteristics by utilizing the superior physical characteristics of carbon can be used effectively as a diaphragm for digital-audio equipment which are now very popular.

Abstract: An electroacoustic diaphragm is provided, which diaphragm comprising a pyrolytic graphite film obtained from a polymer selected from polyoxadiazole, an aromatic polyimide obtained by polycondensation or pyromellitic acid and an aromatic diamine, polybenzthiazole, polybenzbisthiazole, polybenzoxazole, polybenzbisoxazole, poly(pyromellitimide), poly(m-phenyleneisophthalamide). poly(m-phenylenebenzoimidazole), poly(m-phenylenebenzobisimidazole), polythiazole and poly-p-phenylenevinylene. The graphite film has a discontinuous layer of a polymeric material formed on and in the film whereby not only good electroacoustic characteristics, but also good mechanical strength and good adhesion of an adhesive applied thereof are obtained. A method for fabricating such diaphragm is also described.

Abstract: A speaker cone plate is provided with an inorganic surfacial hard layer formed at least on a face of a metal substrate and is subjected to a reinforcing treatment by hot isostatic pressing, wherein the surfacial hard layer may be composed of a carbide, an oxide, a borie or a phosphide or may be formed by plasma thermal spraying of an inorganic substance containing silicon nitride whiskers or silicon carbide whiskers.

Abstract: A dipole loudspeaker includes a rigid support containing an opening and a generally planar multi-layered flexible diaphragm mounted on the support and extending across the opening. The diaphragm is formed of a plurality of layers of thin flexible membrane material, each of the layers having a different height and containing a thin electrical conductor arranged in a predetermined pattern on one surface thereof. The conductor patterns on each of the membranes have different masses, whereby the membrane defines along its height areas of various thickness and varying mass whereby the membrane is suitable for more accurately reproducing or generating high and low frequencies when the electrical conductors are connected with a source of sound signal currents. A plurality of magnets are mounted in spaced relation opposite at least one surface of the membrane and the conductor patterns for vibrating the membrane to reproduce the sound in response to the sound signal currents through the conductor.

Abstract: A transducer which has an astigmatic directional characteristic which depends on its assymetrical stiffness or, respectively, speed of sound of the material of a resonant membrane (2) which is composed of a composite fiber material.

Abstract: An electrodynamic loudspeaker (1) has a diaphragm comprising a central part (2) and a peripheral part (3), and a voice-coil device (9, 10) coupled to the central part (2). The surface ratio S.sub.2 /S.sub.1 complies with the relationship 0.5.ltoreq.S.sub.2 /S.sub.1 .ltoreq.6, where S.sub.1 and S.sub.2 are the surface areas of the central part (2) and the peripheral part (3) respectively. The mass ratio m.sub.2 /m.sub.1 complies with the relationship 0.5.ltoreq.m.sub.2 /m.sub.1 .ltoreq.8 where m.sub.1 and m.sub.2 are the mass of the central part (2) and the voice-coil device (9, 10) and the mass of the peripheral part (3) respectively. Further, the stiffness imposed on the diaphragm by the space (6, 6') defined by the diaphragm (2, 3) and the chassis (4) and/or the magnet system (7) is smaller than the stiffness of the diaphragm itself. Thus it is possible to derive a car loudspeaker which has a specific dip in its frequency response characteristic P (FIG. 2a), measured in an anechoic room.

Abstract: A dome-shaped acoustic motor diaphragm having a core of aluminum foil in the form of a spider web configuration resulting in the dome shape, the diaphragm being in the form of an annular semi-dome outer diaphragm part and a dome-shaped cylindrical inner diaphragm part. The spider web core also enables a wide variety of diaphragm shapes to be possible. A voice coil bobbin is passed through a lower diaphragm layer and unto the underside of an upper diaphram layer via the core which more or less is the greatest height of the same core in the region of the outer diaphragm part, thereby resulting in a highly effective bonding strength between these parts. Damping is accomplished by means of a cylindrical bellows having a height representing the maximum excursion distance of the movable parts. A bobbin guide positioned within the bobbin and bonded to the inner face of the lower magnetic pole piece prevents the bobbin and voice coil in the annular air gap from contacting the pole pieces.