Abstract: A speaker unit for an earphone is provided. The speaker unit for an earphone may include a frame; a magnet; a plate fixed to the frame and in contact with the magnet; a diaphragm; a coil disposed to overlap the magnet and the plate in a radial direction; and a flexible printed circuit board (FPCB), wherein the magnet includes a first surface and a second surface arranged on an outer surface of the magnet, the first surface is a surface in contact with an inner surface of the frame, the second surface is a surface spaced apart from the inner surface of the frame, and the frame forms a first sound emission path defined by a space between the inner surface thereof and the second surface of the magnet in the radial direction.

Abstract: A speaker module includes a first cavity body, a second cavity body disposed adjacent to the first cavity body and a vibration module disposed in the first cavity body and including a first diaphragm and a second diaphragm which are horizontally spaced apart. The first cavity body includes a first sub-cavity and a second sub-cavity which are respectively located on two opposite sides of the vibration module, and the second sub-cavity is communicated with the second cavity body.

Abstract: A vibration module for applying vibrational tractions to a wearer's skin is presented. Use of the vibration module in headphones is illustrated for providing tactile sensations of low frequency for music, for massage, and for electrical recording and stimulation of the wearer. Damped, planar, electromagnetically-actuated vibration modules of the moving magnet type are presented in theory and reduced to practice, and shown to provide a substantially uniform frequency response over the range 40-200 Hz with a minimum of unwanted audio.

Abstract: A suspension arrangement for an audio loudspeaker including a spring element disposed within a voice coil former, where the spring element includes a top portion connected to the voice coil former and an opposite bottom portion connected to a motor of the loudspeaker, and where the spring element is disposed coaxially with the voice coil former and with the motor.

Abstract: A vibration module for applying vibrational tractions to a wearer's skin is presented. Use of the vibration module in headphones is illustrated for providing tactile sensations of low frequency for music, for massage, and for electrical recording and stimulation of the wearer. Damped, planar, electromagnetically-actuated vibration modules of the moving magnet type are presented in theory and reduced to practice, and shown to provide a substantially uniform frequency response over the range 40-200 Hz with a minimum of unwanted audio.

Abstract: A sound amplification system integrated with back cavity pressure sensing, including: a loudspeaker body, including: a vibrating diaphragm, a voice coil connected with the vibrating diaphragm, and a back cavity, wherein the voice coil is connected to a driving unit, a microphone is in the back cavity, and the microphone senses an internal pressure of the back cavity; a computing unit, making an estimation of a displacement of the vibrating diaphragm based on the internal pressure; and a processing unit, determining the displacement of the vibrating diaphragm when compared with a reference displacement, when it is determined that the displacement exceeds a set threshold, a pre-compensation signal is generated and provided to the driving unit.

Abstract: A loudspeaker includes a bottom plate, an internal magnet, an internal plate, an external magnetic part, a frame, a diaphragm, and a voice coil. The internal plate includes a cutout portion so that the internal plate is smaller than the internal magnet when viewed from the top surface of the internal plate. Between the voice coil and the internal plate, there are a holding portion holding magnetic fluid and a void part having a void. The magnetic fluid is held in part of the cutout portion.

Abstract: A speaker includes a first vibrator, a first driving unit, a second vibrator, a second driving unit and a supporting unit. The first vibrator is connected to a diaphragm, which vibrates, thereby emitting sound. The first driving unit vibrates the first vibrator, thereby vibrating the diaphragm. The second vibrator is connected to a weight member. The second driving unit is connected to the opposite side of the first driving unit to the first vibrator, and vibrates the second vibrator on the same vibration axis as the vibration axis of the first vibrator, thereby vibrating the weight member. The supporting unit supports a coupled body, configured by joining the second vibrator and the weight member, at two or more portions in the direction of the vibration axis.

Abstract: A speaker device includes: a magnetic circuit including a plate 1, a magnet 2 having no through-hole, and a yoke 3 forming a magnetic gap; a voice coil 6 disposed in the magnetic gap; a diaphragm 4 directly or indirectly fixed to the voice coil 6; and a magnetic fluid 7 disposed in at least a space between an outer peripheral surface of the voice coil 6 and an inner peripheral surface of the yoke 3. A rear surface side space between a rear surface of the diaphragm 4 and a front surface of the plate 1 communicates with a space outside the speaker device through a gap-for-communication 15 which is formed in at least a part, in a peripheral direction of the voice coil 6, of the space between the outer peripheral surface of the plate 1 and the inner peripheral surface of the voice coil 6.

Abstract: [Object] To lower a mechanical resonance sharpness and reduce oscillations near a minimum resonance frequency, to thereby improve the sound quality.

Abstract: [Object] To lower a mechanical resonance sharpness and reduce oscillations near a minimum resonance frequency, to thereby improve the sound quality.

Abstract: A speaker device includes: a magnetic circuit including a plate 1, a magnet 2 having no through-hole, and a yoke 3 forming a magnetic gap; a voice coil 6 disposed in the magnetic gap; a diaphragm 4 directly or indirectly fixed to the voice coil 6; and a magnetic fluid 7 disposed in at least a space between an outer peripheral surface of the voice coil 6 and an inner peripheral surface of the yoke 3. A rear surface side space between a rear surface of the diaphragm 4 and a front surface of the plate 1 communicates with a space outside the speaker device through a gap-for-communication 15 which is formed in at least a part, in a peripheral direction of the voice coil 6, of the space between the outer peripheral surface of the plate 1 and the inner peripheral surface of the voice coil 6.

Abstract: A speaker assembly includes a speaker housing having a substantially closed speaker chamber, the speaker housing including a first wall with a dimple assembly defining a heat sink formed therein. A first driver is mounted and enclosed in the speaker chamber, the first driver including a cone coupled to a driver magnet for generating sound. The driver magnet is in direct contact with the dimple assembly effectively exposing the driver magnet to an exterior of the speaker housing via the heat sink defined by the dimple assembly.

Abstract: A speaker includes a ring-shaped magnet, a yoke having a center pole portion inserted in the center of the magnet, and a ring-shaped plate and arranged on the outer circumferential surface of the center pole portion of the yoke and attached to the magnet. The speaker includes a cylindrically-shaped coil bobbin that is movable in the axial direction of the center pole portion and partially fitted on the center pole portion of the yoke. The speaker includes a voice coil wrapped around the outer circumferential surface of the coil bobbin, part of the voice coil being arranged in a magnetic gap, which is filled with a magnetic fluid, formed between the plate and the center pole portion of the yoke. The speaker includes a diaphragm having its inner circumferential portion connected to the coil bobbin, and that is vibrated as the coil bobbin moves.

Abstract: A loudspeaker is provided which includes: a magnetic circuit including a magnet having at least one hole, a plate fixed to one of a pair of polar surfaces of the magnet, and a box-shaped yoke having an inner bottom surface fixed to the other polar surface of the magnet; a voice coil vertically vibratably provided in a magnetic gap formed by the plate and the yoke; a diaphragm having a peripheral edge connected to an upper end of the voice coil; and a magnetic fluid filled in at least one of a gap between the voice coil and the plate and a gap between the voice coil and the yoke. The loudspeaker includes at least one means for uniformly distributing the magnetic fluid.

Abstract: A speaker and the like, which is capable of wideband reproduction by improving the bass characteristic, and which is suitable for size reduction, is provided. A housing (110) includes one main surface (111) having a polygonal shape, and an opening portion (112) in the one main surface. A diaphragm (120) is disposed in the opening portion so as to cover the one main surface, except for corner regions (115a, 115b, 115c, and 115d) which are areas in the vicinity of respective vertices of a polygonal shape of the one main surface. A driving unit (130) causes the diaphragm to vibrate so as to generate a sound corresponding to a signal inputted from an outside. A plurality of movable supports (140a, 140b, 140c, and 140d) is disposed in the respective corner regions, for supporting the diaphragm by joining the housing and the diaphragm such that the diaphragm is vibratable.

Abstract: A loudspeaker includes a diaphragm that vibrates back and forth to emit a sound, a magnetic circuit that is provided on a rear side of the diaphragm and has a magnetic gap on a diaphragm side, and a voice coil that is directly or indirectly joined to the diaphragm and disposed within the magnetic gap. A magnetic fluid is loaded within the magnetic gap. Also, a plurality of first edge pieces are provided at different positions in an outer circumferential portion of the diaphragm for vibratably supporting the diaphragm, each of the first edge pieces having a non-linear cross-sectional shape.

Abstract: A loudspeaker includes a diaphragm that vibrates back and forth to emit a sound, a magnetic circuit that is provided on a rear side of the diaphragm and has a magnetic gap on a diaphragm side, and a voice coil that is directly or indirectly joined to the diaphragm and disposed within the magnetic gap. A magnetic fluid is loaded within the magnetic gap. Also, a plurality of first edge pieces are provided at different positions in an outer circumferential portion of the diaphragm for vibratably supporting the diaphragm, each of the first edge pieces having a non-linear cross-sectional shape.

Abstract: A loudspeaker includes a diaphragm that vibrates back and forth to emit a sound, a magnetic circuit that is provided on a rear side of the diaphragm and has a magnetic gap on a diaphragm side, and a voice coil that is directly or indirectly joined to the diaphragm and disposed within the magnetic gap. A magnetic fluid is loaded within the magnetic gap. Also, a plurality of first edge pieces are provided at different positions in an outer circumferential portion of the diaphragm for vibratably supporting the diaphragm, each of the first edge pieces having a non-linear cross-sectional shape.

Abstract: The present invention provides a sensory signal output apparatus wherein a coil is disposed in the gap between a magnet/top plate and a yoke, and a portion elastically supported in the free space vibrates in reaction to the magnetic flux generated in the gap in accordance with the direction of the alternating current signal applied to the coil to generate sound and/or vibration, wherein the yoke has a groove formed at a side other than that with the magnet, and the groove has a diameter smaller than that of the magnet, and an inner edge portion with a magnetic fluid. The sensory signal output apparatus of the present invention improves the position retaining force of the magnetic fluid and reduces the deformation of the magnetic fluid, as the magnetic fluid is formed in the edge of the groove of the yoke corresponding to the edge portion of the magnet which has a relatively bigger magnetic force and magnetic field than the plane portion of the magnet.

Abstract: An electrodynamic transducer with a membrane includes an electrodynamic motor in a carcass in which a coil held by a mandrel connected to the membrane is capable of movement. The mandrel has a shape generated by an essentially linear generatrix, the coil being arranged in an air gap of a vertical free space where it is capable of movement and defined, towards the center of the transducer, by an inner magnetic structure and, towards the periphery of the transducer, by an outer magnetic structure, at least one of the magnetic structures generating a static magnetic field, wherein the transducer does not include any peripheral nor inner suspension and the guiding of the mobile equipment and the pneumatic tightness between the front and rear faces of the membrane being ensured by a ferrofluid. The mandrel is maintained in the air gap by the ferrofluid applied on at least one of the two faces of the mandrel and entirely filling the air gap.

Abstract: A speaker and the like, which is capable of wideband reproduction by improving the bass characteristic, and which is suitable for size reduction, is provided. A housing (110) includes one main surface (111) having a polygonal shape, and an opening portion (112) in the one main surface. A diaphragm (120) is disposed in the opening portion so as to cover the one main surface, except for corner regions (115a, 115b, 115c, and 115d) which are areas in the vicinity of respective vertices of a polygonal shape of the one main surface. A driving unit (130) causes the diaphragm to vibrate so as to generate a sound corresponding to a signal inputted from an outside. A plurality of movable supports (140a, 140b, 140c, and 140d) is disposed in the respective corner regions, for supporting the diaphragm by joining the housing and the diaphragm such that the diaphragm is vibratable.

Abstract: The invention relates to an electrodynamic transducer (1) with a dome type diaphragm (2), comprising an electrodynamic motor with a coil (6) borne by a mandrel (3) integral with the diaphragm suspended to a yoke (7), the coil being placed in an air gap of a vertical free space in which it can move and which is defined, toward the center, by an internal magnetic construction (4), and toward the periphery, by an external magnetic construction (5), wherein the suspension comprises neither peripheral suspension nor internal suspension, the transducer comprises at least two magnetic field confinement means (11) in the air gap in order to form by mean of a ferromagnetic liquid at least two ferrofluidic seals (12, 13, 14) stepped in the air gap, fulfilling at least the guidance of the coil and the pneumatic tightness between the front and rear faces of the diaphragm, at least one of the ferrofluidic seals being continuous. Application to loudspeakers.

Abstract: A speaker apparatus has a container holding a volume of ferrofluid, a permanent magnet suspended in the ferrofluid, and a magnetic excitation apparatus proximate the container. Operation of the excitation apparatus causes movement of the permanent magnet, translated through the ferrofluid to walls of the container, which walls act as resonators creating sound waves in surrounding medium. Audio production is accomplished placing a ferrofluid and a permanent magnet in a container, placing an excitation apparatus in proximity of the permanent magnet, and driving the excitation apparatus to cause movement of the permanent magnet translated through the ferrofluid to walls of the container, which walls act as resonators creating sound waves in surrounding medium.

Abstract: A headgear system enhanced for generating sound has at least one speaker apparatus connected to or integrated into the structure of the headgear system, the speaker apparatus including a magnet suspended in a magnetic fluid, and at least one resonator connected to the at least one speaker apparatus. The system is characterized in that excitation of the magnet produces vibration translated to the resonator to generate the sound.

Abstract: A loudspeaker according to the present invention includes: a diaphragm that vibrates back and forth to emit a sound; a magnetic circuit that is provided on a rear side of the diaphragm and has a magnetic gap on a diaphragm side; a voice coil that is directly or indirectly joined to the diaphragm and disposed within the magnetic gap; a magnetic fluid that is loaded within the magnetic gap; and a plurality of first edge pieces that are provided at different positions in an outer circumferential portion of the diaphragm for vibratably supporting the diaphragm, each of the first edge pieces having a non-linear cross-sectional shape.

Abstract: An audio speaker has a driver unit having a support frame with a central portion forming a magnetic structure defining an annular gap around a central magnetic post, a vibration system having a diaphragm and a voice coil, the voice coil is attached to one side of the diaphragm where the vibration system is fixed to the support frame and where the voice coil is movably mounted in the annular gap, and a magnetic fluid disposed in the annular gap only in a space between one side of the voice coil and a surface of the annular gap having a higher magnetic flux density.

Abstract: A speaker apparatus has a container holding a volume of ferrofluid, a permanent magnet suspended in the ferrofluid, and a magnetic excitation apparatus proximate the container. Operation of the excitation apparatus causes movement of the permanent magnet, translated through the ferrofluid to walls of the container, which walls act as resonators creating sound waves in surrounding medium. Audio production is accomplished placing a ferrofluid and a permanent magnet in a container, placing an excitation apparatus in proximity of the permanent magnet, and driving the excitation apparatus to cause movement of the permanent magnet translated through the ferrofluid to walls of the container, which walls act as resonators creating sound waves in surrounding medium.

Abstract: A hearing aid includes a sound input device, and a speaker, wherein the speaker includes a compartment with magnet suspended in a fluid containing magnetic particles and wherein a coil wrapped around the compartment or in close proximity thereto excites the magnet to vibrate causing pressure waves to vibrate a diaphragm proximal to the magnet.

Abstract: The invention relates to an electrodynamic transducer (1) with a dome type diaphragm (2), comprising an electrodynamic motor with a coil (6) borne by a mandrel (3) integral with the diaphragm suspended to a yoke (7), the coil being placed in an air gap of a vertical free space in which it can move and which is defined, toward the center, by an internal magnetic construction (4), and toward the periphery, by an external magnetic construction (5), wherein the suspension comprises neither peripheral suspension nor internal suspension, the transducer comprises at least two magnetic field confinement means (11) in the air gap in order to form by mean of a ferromagnetic liquid at least two ferrofluidic seals (12, 13, 14) stepped in the air gap, fulfilling at least the guidance of the coil and the pneumatic tightness between the front and rear faces of the diaphragm, at least one of the ferrofluidic seals being continuous. Application to loudspeakers.

Abstract: The invention is a novel circuit wherein maximum shove is achieved yet the transducer's height profile is minimized. The profile is minimized by using mated beveled surfaces on an annular magnet and the top plate which prevents the top plate from reaching saturation and reduces the reluctance f the magnetic flux path. A novel anti-fringe geometry to reduce flux leakage and net saturation in the center post improves the magnetic reluctance of the circuit. An external housing assembly is provided with integral suspension elements for radial stiffness and axial compliance and for aligning the circuit within the housing to prevent cocking and resulting distortion.

Abstract: A speaker apparatus has a container holding a volume of ferrofluid, a permanent magnet suspended in the ferrofluid, and a magnetic excitation apparatus proximate the container. Operation of the excitation apparatus causes movement of the permanent magnet, translated through the ferrofluid to walls of the container, which walls act as resonators creating sound waves in surrounding medium. Audio production is accomplished placing a ferrofluid and a permanent magnet in a container, placing an excitation apparatus in proximity of the permanent magnet, and driving the excitation apparatus to cause movement of the permanent magnet translated through the ferrofluid to walls of the container, which walls act as resonators creating sound waves in surrounding medium.

Abstract: The present invention provides an intertial-type voice actuator that includes a magnetic flux conductive material core with a continuous channel. The channel has antifringing groove. The actuator employs a radially polarized cylindrical magnet spaced in the channel to form a magnetic gap and a conductive coil positioned at least partially in the gap. A multi-component suspension system provides high quality sound using an antifriction bearing, a viscous magnetic fluid, and a spider suspension. The inertial-type actuator is completed by an integrated mounting apparatus. In one embodiment, a receiver and an output disk are interlocked by helical wedges and the actuator is mounted on a soundboard. In another embodiment, a special receiving cavity is attached to a wall stud for intrawall installation. The cavity is equipped with longitudinal electrical contacts so that the actuator can move and still be connected. After the actuator is inserted, the wall covering is installed.

Abstract: An audio speaker includes a driver unit having a magnetic pole case defining a radial gap, a vibration system having a diaphragm and a voice coil where the vibration system is fixed to the drive unit and the voice coil is movably mounted into the radial gap, and a residual magnetic fluid layer disposed on the surfaces of one or more of the magnetic pole case and the voice coil where an air gap exists between the voice coil and the magnetic pole case.

Abstract: An audio speaker has a driver unit having a support frame with a central portion forming a magnetic structure defining an annular gap around a central magnetic post, a vibration system having a diaphragm and a voice coil, the voice coil is attached to one side of the diaphragm where the vibration system is fixed to the support frame and where the voice coil is movably mounted in the annular gap, and a magnetic fluid disposed in the annular gap only in a space between one side of the voice coil and a surface of the annular gap having a higher magnetic flux density.

Abstract: The micro-speaker includes a driver unit having a housing, a magnet disposed within the housing forming a radial gap between the magnet and the circumferential walls of the housing, and a magnetic plate disposed on the magnet, a vibration system having a diaphragm and a voice coil where the vibration system is fixed to the drive unit and the voice coil protrudes into the radial gap, and a volatile magnetic fluid in the radial gap about the voice coil.

Abstract: A speaker comprising: a magnetic circuit provided with a through hole, and a recess formed around the through hole for retaining a magnetic fluid. The speaker further comprises a bearing provided in the through hole and a shaft supported by the bearing to be movable up and down and fixed to a center cap fixed to a voice coil. A gap between the bearing and the shaft is filled with the magnetic fluid. The speaker eliminates a damper, and realizes a very low f0 which has not been obtained before. Furthermore, the magnetic fluid absorbs friction and resonance between the bearing and the shaft, and the magnetic fluid is kept in the recess and is supplied smoothly into the gap between the shaft and the bearing. Thus, generation of abnormal sounds is suppressed and a large amplitude operation is realized in the speakers of the present invention.

Abstract: A loudspeaker has a diaphragm with a voice coil disposed about its perimeter and extending in a gap into which the flux of an annular rare earth magnet is focused. An opening behind the diaphragm communicates through the speaker frame. The voice coil may have two or more windings that are connected in parallel, and may, e.g., be layered on top of one another, so that the impedance of the coil, as well as its depth in the front/back direction of motion, are low. The voice coil is preferably implemented using a polyamide form or bobbin, which has patterned lead-in conductors embedded therein to bring power to wire windings on the perimeter of the coil. The lead-in conductors extend to, or through, the central opening of a ring magnet, providing a robust ribbon input connection.

Abstract: The method of assembling a speaker includes disposing a quantity of volatile magnetic fluid containing a pre-determined amount of lubricating oil into a radial gap of a driver unit, aligning a vibration system having a diaphragm and a voice coil to the driver unit such that the voice coil is movably mounted into the radial gap, fixing the vibration system to the driver unit, and removing the volatile component of the volatile magnetic fluid. The speaker includes a driver unit having a magnetic pole case defining a radial gap, a vibration system having a diaphragm and a voice coil where the vibration system is fixed to the drive unit and the voice coil is movably mounted into the radial gap, and a residual magnetic fluid layer disposed on the surfaces of one or more of the magnetic pole case and the voice coil where an air gap exists between the voice coil and the magnetic pole case.

Abstract: The micro-speaker includes a driver unit having a housing, a magnet disposed within the housing forming a radial gap between the magnet and the circumferential walls of the housing, and a magnetic plate disposed on the magnet, a vibration system having a diaphragm and a voice coil where the vibration system is fixed to the drive unit and the voice coil protrudes into the radial gap, and a volatile magnetic fluid in the radial gap about the voice coil.

Abstract: The method of assembling a micro-speaker includes disposing a quantity of volatile magnetic fluid into a radial gap of a driver unit, aligning a vibration system having a diaphragm and a voice coil to the driver unit such that the voice coil is accommodated into the radial gap, fixing the vibration system to the driver unit, and removing the volatile component of the volatile magnetic fluid. The micro-speaker includes a driver unit having a housing, a magnet disposed within the housing forming a radial gap between the magnet and the circumferential walls of the housing, and a magnetic plate disposed on the magnet, a vibration system having a diaphragm and a voice coil where the vibration system is fixed to the drive unit and the voice coil protrudes into the radial gap, and a volatile magnetic fluid in the radial gap about the voice coil.

Abstract: The present invention provides a transducer for converting between mechanical vibration and electrical signal, the transducer comprising a housing enclosing a substantially cylindrical permanent magnet and a coil, the magnet having a side-to-side polar orientation. The transducer may be used as sensor that is part of a sensor array for detecting vibrations from a hollow-bodied musical instrument and converting the vibrations into electrical signals for amplification.

Abstract: A receiver for converting electrical energy to acoustical energy, and a method of manufacturing the receiver, are disclosed. The receiver comprises an armature having a peripheral edge, a magnet stack and a weld joint for attaching the armature to the magnet stack at the peripheral edge of said armature. The method comprises providing an armature having a peripheral edge, providing a magnet stack adjacent said armature, and welding said armature to the magnet stack at the peripheral edge of said armature.

Abstract: A loudspeaker has a diaphragm with a voice coil disposed about its perimeter and extending in a gap into which the flux of an annular rare earth magnet is focused. An opening behind the diaphragm communicates through the speaker frame. The voice coil may have two or more windings that are connected in parallel, and may, e.g., be layered on top of one another, so that the impedance of the coil, as well as its depth in the front/back direction of motion, are low. The voice coil is preferably implemented using a polyimide form or bobbin, which has patterned lead-in conductors embedded therein to bring power to wire windings on the perimeter of the coil. The lead-in conductors extend to, or through, the central opening of a ring magnet, providing a robust ribbon input connection. The ribbon lead-in may be symmetrical, and the central opening further provides an air channel that couples to an auxiliary chamber for enhanced sound.

Abstract: The method of assembling a speaker includes disposing a quantity of volatile magnetic fluid containing a pre-determined amount of lubricating oil into a radial gap of a driver unit, aligning a vibration system having a diaphragm and a voice coil to the driver unit such that the voice coil is movably mounted into the radial gap, fixing the vibration system to the driver unit, and removing the volatile component of the volatile magnetic fluid. The speaker includes a driver unit having a magnetic pole case defining a radial gap, a vibration system having a diaphragm and a voice coil where the vibration system is fixed to the drive unit and the voice coil is movably mounted into the radial gap, and a residual magnetic fluid layer disposed on the surfaces of one or more of the magnetic pole case and the voice coil where an air gap exists between the voice coil and the magnetic pole case.

Abstract: The method of assembling a micro-speaker includes disposing a quantity of volatile magnetic fluid into a radial gap of a driver unit, aligning a vibration system having a diaphragm and a voice coil to the driver unit such that the voice coil is accommodated into the radial gap, fixing the vibration system to the driver unit, and removing the volatile component of the volatile magnetic fluid. The micro-speaker includes a driver unit having a housing, a magnet disposed within the housing forming a radial gap between the magnet and the circumferential walls of the housing, and a magnetic plate disposed on the magnet, a vibration system having a diaphragm and a voice coil where the vibration system is fixed to the drive unit and the voice coil protrudes into the radial gap, and a volatile magnetic fluid in the radial gap about the voice coil.

Abstract: An electromagnetic sound producing device has a yoke, a coil, a permanent magnet, and a diaphragm provided in a case. The permanent magnet is made of SmFeN-base isotropy plastic magnetic material.

Abstract: The invention relates to a manufacturing process of an electrical conductor or circuit compensated for radio interferences, including those from the electrical circuit itself. An application of a semi-conductor material (2) of resistivity coefficient allowing the external surface of the conductor (1) to the electrical circuit to be maintained at a static electrical potential near to that of the conductor (1) and the random electrical discharge currents to be absorbed is made to eliminate the interface micro-discharge interference phenomena. Application in the field of HiFi, home automation, instrumentation.

Abstract: A loudspeaker includes: a frame; a vibrating section including a diaphragm having an internal periphery and an external periphery, a voice coil attached to the internal periphery of the diaphragm, a spider which connects the voice coil to the frame, and a dust cap attached to the internal periphery of the diaphragm; and a surround which connects the external periphery of the diaphragm to the frame, wherein the ratio between the weight of the vibrating section and the weight of the surround is 0.9:1 to 1.5:1.

Abstract: An electrodynamic acoustic transducer with a coil which projects into an air gap subject to an electromagnetic field, wherein an acoustic short circuit is prevented. The electrodynamic transducer has a membrane comprising two differently profiled portions, an acoustically effective central portion with a convexity in form of a spherical cap, and a ring-shaped bead which borders the central portion and serves to elastically support the membrane. The ring-shaped bead is arranged beneath the central portion and extends radially inwards starting from a coil seat of the coil. The air gap is sealed by means of a liquid or solid medium, such as ferrofluid, such that an acoustic short circuit between the front volume and the rear volume of the transducer is prevented.