Abstract: A speaker has a magnet structure mounted ahead of the speaker diaphragm to produce a shallow compact unit. The magnet structure defines a flux gap, and a voice coil residing in the flux gap is connected to a main diaphragm such that drive current applied to the voice coil moves the diaphragm to generate sound. The voice coil and magnet structure provide a flux gap at the rear of the magnet structure, ahead of and centered on the main diaphragm, while the magnet occupies space within the cone, freeing up space in the rear. In one embodiment, the magnet structure has an additional flux gap located at its forward end and the speaker includes an additional diaphragm driven by a coil positioned in the additional flux gap. The main diaphragm and additional diaphragm are better positioned to maintain a common sound center for enhanced spatial fidelity and different tuning techniques present a broad flat response below crossover to form a pinpoint sound source of wide angular coverage.

Abstract: A loudspeaker has a cooling system in which a pole piece has a shorting ring made of non-magnetic conductive material that stabilizes magnetic field to reduce distortion of sound and a heat dissipation plate that couples to the shorting ring to facilitate efficient dissipation of heat. The heat generated by a voice coil of the loudspeaker is transmitted to the shorting ring and is conducted to the heat dissipation plate which acts as a heat sink to allow the heat dissipation. A multiplicity of shorting rings may be provided to further reduce impedance modulation, each of which is coupled to the heat dissipation plate. The heat dissipation plate has a gap in an axial direction of the loudspeaker to prevent an electric current in the shorting ring from flowing through the heat dissipation plate.

Abstract: An electromagnetic driving unit includes a magnet part and a coil part that is translatable along a translation axis with respect to the magnet part. A diaphragm extends from the coil part in a substantially radial direction with respect to the translation axis of the coil part. The magnet part includes two permanent magnets and an intermediate magnetic pole element that is sandwiched between the permanent magnets when viewed along the translation axis of the coil part. In order to improve the efficiency of the driving unit, the permanent magnets and the intermediate magnetic pole element are sandwiched between two external magnetic pole elements, and all pole elements have pole faces that are magnetically directed towards the coil part.

Abstract: A magnet assembly having inner and outer yokes of magnetic flux conductive material which together define an annular air gap and a radially oriented magnet sandwiched between the inner and outer yokes such that a first face of a first magnetic polarity contacts the inner yoke and a second face of a second opposite magnetic polarity contacts the outer yoke, characterised by an axially oriented magnet forming part of the magnet assembly, and wherein the radially oriented magnet is annular and has opposed axial ends, and the inner and outer yokes are annular and together enclose one axial end of radially oriented magnet to define the air gap, and wherein the axially oriented magnet is disposed adjacent to the other axial end of the radially oriented magnet, whereby the inner and outer yokes and the axially oriented magnet together reduce flux leakage from the magnet assembly.

Abstract: An electromagnetic transducer includes a magnetic member, a suspension for supporting the magnetic member at a central portion of the suspension, a diaphragm connected to the suspension, a magnet for generating magnetic flux on the magnetic member, and a coil for generating alternating magnetic flux on the magnetic member.

Abstract: An electroacoustic transducer 20, such as a speaker, a headphone, an earphone, a microphone, an acoustic wave sensor, etc., includes magnet plates 21 and 22, the entirety of which are formed like a disk or a ring; and an acoustic diaphragm 23 disposed parallel to said magnet plates 21 and 22 and having a conductor formed on the plane thereof; wherein a component parallel to the vibration plane of said acoustic diaphragm 23 is zero or in the radius direction of said magnet plates 21 and 22 in the direction of magnetizing respective partial areas of said magnet plates 21 and 22, and angles formed by said magnetizing direction with respect to the vibration plane of said acoustic diaphragm 23 are made gradually different from each other in accordance with the distance from the center axis of said magnet plates 21 and 22.

Abstract: A loudspeaker motor structure uses variable geometry to change the effective magnetic field acting on the voice coil of the motor structure. A magnet generates the magnetic field, which couples into a front plate, a back plate, and a pole piece. In one loudspeaker, the front plate and the pole piece have notches and slots. Rotating the pole piece relative to the front plate varies the width of the gap between the pole piece and the front plate, and the effective magnetic field in the gap. In another loudspeaker, the pole piece moves up and down in relation to the back plate. This movement varies the magnetic coupling between the pole piece and the back plate and, consequently, the effective magnetic field in the gap between the pole piece and the front plate. Variations in the effective magnetic field in the gap result in variations of the loudspeaker parameters.

Abstract: An internal magnetic circuit is formed by a plate forming a pole piece, a vertically magnetized magnet attached to a bottom face of the plate, and a yoke attached to a bottom face of the magnet. A magnetic gap is formed between the plate and the yoke. The yoke includes a bottom part attached to the bottom face of the magnet, a side part standing on the side of the plate, and a folded-back part folding downwards over the side part to face the magnetic gap. Thus, the internal magnetic circuit having a uniform magnetic flux density inside the magnetic gap along the direction of its length is provided.

Abstract: An electromagnetic transducer, such as an audio speaker, includes a return path member which is a pole piece for external magnet geometries or a cup for internal magnet geometries. The magnetic flux return path for the primary drive magnet is through a first portion of the return path member. A first section of a low reluctance magnetic flux return path for a secondary drive magnet is through a second portion of the return path member. A magnetically conductive plate provides a second section of the low reluctance return path from the second portion of the return path member to the secondary drive magnet.

Abstract: An electroacoustic transducer includes a magnetic circuit of a magnetically conductive material with a pair of opposed surfaces defining a gap therebetween. The magnetic circuit includes a magnet inducing a magnetic field in the gap, the magnet having a surface constituting one of the opposed surfaces. The magnetic circuit further includes a diaphragm and a coil having electrically conducting paths secured to the diaphragm. The coil has portions of its paths situated in the gap.

Abstract: An electromagnetic drive motor assembly (EDMA) has at least one bridge that extends along a radial direction to conduct heat away from the magnetic gap and towards the outer surface of the EDMA. The EDMA includes a conductive ring between a first plate and a second plate. The conductive ring has an inner ring, an outer ring, and at least one bridge between the inner and outer rings. The inner ring is adapted to receive a voice coil such that the heat generated by the voice coil conducts through the inner ring, the bridge, and then to the outer ring. As such, a heat conducting path is provided within the EDMA to remove the heat away from the voice coil. This allows the EDMA to operate more efficiently. The EDMA may also include a flux return having a pole piece that protrudes from the first plate. The inner ring of the conducting ring may receive the pole piece to form an intermediate gap between the pole piece and the inner ring.

Abstract: The present invention relates to an miniature actuator especially suitable for hearing aid applications. The actuator according to the present invention operates according to the change in reluctance principle. In particular, the actuator according to the present invention operates in a balanced configuration comprising two planar coils, two magnets, a membrane and a spacer chip providing the necessary back chamber volume.

Abstract: An electro-mechanical transducer, including a magnetic assembly producing a magnetic field having two or more displaced regions of greater intensity, having magnetic flux in substantially similar directions, separated by and surrounded by regions of lower intensity magnetic field, and an electrically conductive and mobile member disposed in and capable of moving through a magnetic field.

Abstract: A magnetic circuit for a speaker comprises: a bottom yoke including a center pole; a ring magnet; a top plate; and a short-circuiting ring shaped like a hollow cylinder. The short-circuiting ring is disposed close and parallel to a voice coil and attached to the inner portion of the bottom of the top plate.

Abstract: The present invention provides an electromagnetic drive motor assembly (EDMA) that has an inner flux return assembly formed from an upper pole piece and a lower pole piece oppositely disposed relative to each other along the center of the EDMA. An annularly positioned conductive ring (or flux stabilization ring) encircles the inner flux return assembly, concentrically in contact with the outside of the inner flux return assembly. Along the exterior side of the flux return pieces, is a magnet that is between a top plate and a bottom plate. Each plate contacts with the magnet to form a magnetically conductive system. A magnetic gap is formed in between the inner flux return assembly and the top and bottom plates. Disposed within the magnetic gap is a dual coil wound around a cylinder. The dual coil includes a first coil portion and a second coil portion. To minimize the modulation, the top and bottom plates may be saturated and plate tips may be provided near the magnetic gap.

Abstract: An electromagnetic transducer such as an audio speaker, having a push-push geometry in which there are two or more air gaps and the magnetic flux across the air gaps is in the same orientation. If there are more than one voice coil, the voice coils may thus be generating the same electromagnetic polarity by being wound in the same direction about the bobbin, or by being wound in opposite directions and having separate, opposite polarity electrical connections. The transducer exhibits high linearity over a long travel.

Abstract: An electromagnetic transducer, such as an audio speaker, includes a return path member which is a pole piece for external magnet geometries or a cup for internal magnet geometries. The magnetic flux return path for the primary drive magnet is through a first portion of the return path member. A first section of a low reluctance magnetic flux return path for a secondary drive magnet is through a second portion of the return path member. A magnetically conductive plate provides a second section of the low reluctance return path from the second portion of the return path member to the secondary drive magnet.

Abstract: An electromagnetic transducer includes: a first diaphragm; a second diaphragm provided in a central portion of the first diaphragm, the second diaphragm comprising a magnetic material having a first opening in a central portion thereof; a yoke disposed so as to oppose the first diaphragm; a center pole disposed between the yoke and the first diaphragm, wherein the center pole has a shape which allows insertion into the first opening; a coil disposed so as to surround the center pole; and a first magnet disposed so as to surround the coil.

Abstract: An electromagnetic transducer such as an audio speaker exhibiting highly linear performance over a greatly extended excursion. The motor structure includes a stack of two or more magnet and plate pairs, with the magnets polarized in the same orientation such that the magnetic flux flows in the same direction over all of the magnetic air gaps. The voice coil is handed off from gap to gap with a configuration providing a substantially constant BL over an end-to-end distance at least as large as the thickness of one plate plus twice the thickness of one magnet.

Abstract: Loudspeaker and other transducers of the dual-voice-coil/dual-magnetic-gap type can be improved by the addition of one or more annular shorting rings strategically located in the vicinity of the two magnetic gaps. The shorting rings have no effect on a steady state magnetic field but act in opposition to any change in flux density or any displacement of the flux lines such as those that occur under the loading imposed when the voice coils are driven hard with audio frequency current. The location of the shorting rings determines their effect: location close to a voice coil reduces the voice coil inductance, location entirely within the magnetic flux loop centerline favors reduction of second harmonic distortion and higher order even harmonic distortion, a centered location on the flux loop centerline, i.e.

Abstract: The present invention provides an electromagnetic drive motor assembly (EDMA) that has an inner flux return assembly formed from an upper pole piece and a lower pole piece oppositely disposed relative to each other along the center of the EDMA. An annularly positioned conductive ring (or flux stabilization ring) encircles the inner flux return assembly, concentrically in contact with the outside of the inner flux return assembly. Along the exterior side of the flux return pieces, is a magnet that is between a top plate and a bottom plate. Each plate contacts with the magnet to form a magnetically conductive system. A magnetic gap is formed in between the inner flux return assembly and the top and bottom plates. Disposed within the magnetic gap is a dual coil wound around a cylinder. The dual coil includes a first coil portion and a second coil portion. To minimize the modulation, the top and bottom plates may be saturated and plate tips may be provided near the magnetic gap.

Abstract: A core having a coil wound thereon is fixed to a base at the bottom. The base is fixed to a case made of synthetic resin by insert molding. A diaphragm is fixed to the case in circumference, and also a magnetic flux guide member is fixed to the case in circumference. Since the diaphragm and the magnetic flux guide member is commonly fixed to the case, no variation in the distance between the diaphragm and the magnetic flux guide member would occur for every product. Further, a gap L is formed between the magnet and the magnetic flux guide member, and an air hole is formed in the magnetic flux guide member. This improves the passage of air and reduces air dumper effect without modifying the magnet in shape.

Abstract: Ring magnets (5) are concentrically placed with certain spacings (6) on a magnetic frame (4). The magnetic members on the magnets (5) are removed, and the magnets are arranged so that the polarities of adjacent magnets (5)are alternately opposite to each other, thus forming a magnetic circuit. Ribs (7) are provided to a planar vibrating plate (1) and a voice coil (2) fabricated by vertically stacking conductive wires annularly is attached to the planar vibrating plate (1). The planar vibrating plate (1) is secured to a frame (4) through a gasket (3). The voice coil (2) is inserted into magnetic gaps of spacings (6). Since no magnetic body is placed over the magnets (5), the height of the magnetic circuit can be low, and an increase of the reactance due to provision of the magnetic body of the voice coil (2) does not occur. Since the rigidity of the planar vibrating plate (1) is high, it is unnecessary to secure the planar vibrating plate (1) to the frame (4). while applying a tension.

Abstract: An electroacoustic transducer 1 includes a base 24 made of a magnetic material; a magnetic core 22 made of a magnetic material and upstanding on the base 24; a diaphragm 20 made of a magnetic material and spaced from a leading end of the magnetic core; a magnetic field generating member 25 cooperating with the base 24, the magnetic core 22 and the diaphragm 20 to constitute a magnetic circuit, for supplying a static magnetic field; a coil 23 placed around the magnetic core, for supplying an oscillating magnetic field to the magnetic circuit. The magnetic field generating member 25 constitutes a multiplex ring structure in which a magnet 25a and a support ring 26 are integrated together, whose faces opposing the diaphragm 20 have respectively magnetic poles of the same polarity.

Abstract: A speaker has a magnet structure mounted ahead of the speaker diaphragm to produce a shallow compact unit. The magnet structure defines a flux gap, and a voice coil residing in the flux gap is connected to a main diaphragm such that drive current applied to the voice coil moves the diaphragm to generate sound. The voice coil and magnet structure provide a flux gap at the rear of the magnet structure, ahead of and centered on the main diaphragm, while the magnet occupies space within the cone, freeing up space in the rear. In one embodiment, the magnet structure has an additional flux gap located at its forward end and the speaker includes an additional diaphragm driven by a coil positioned in the additional flux gap. The main diaphragm and additional diaphragm are better positioned to maintain a common sound center for enhanced spatial fidelity and different tuning techniques present a broad flat response below crossover to form a pinpoint sound source of wide angular coverage.

Abstract: The present invention provides an electromagnetic drive motor assembly (EDMA) that has an inner flux return assembly formed from an upper pole piece and a lower pole piece oppositely disposed relative to each other along the center of the EDMA. An annularly positioned conductive ring (or flux stabilization ring) encircles the inner flux return assembly, concentrically in contact with the outside of the inner flux return assembly. Along the exterior side of the flux return pieces, is a magnet that is between a top plate and a bottom plate. Each plate contacts with the magnet to form a magnetically conductive system. A magnetic gap is formed in between the inner flux return assembly and the top and bottom plates. Disposed within the magnetic gap is a dual coil wound around a cylinder. The dual coil includes a first coil portion and a second coil portion. To minimize the modulation, the top and bottom plates may be saturated and plate tips may be provided near the magnetic gap.

Abstract: Loudspeakers and other transducers of the dual-voice-coil/dual-magnetic-gap type can be improved by the addition of one or more annular shorting rings strategically located in the vicinity of the two magnetic gaps. The shorting rings have no effect on a steady state magnetic field but act in opposition to any change in flux density or any displacement of the flux lines such as those that occur under the loading imposed when the voice coils are driven hard with audio frequency current. The location of the shorting rings determines their effect: location close to a voice coil reduces the voice coil inductance, location entirely within the magnetic flux loop centerline favors reduction of second harmonic and higher order even harmonic distortion, a centered location on the flux loop centerline, i.e.

Abstract: An electromagnetic transducer, such as an audio speaker, in which magnetic flux is provided to the drive magnetic air gap(s) by both an external permanent magnet (as in conventional pole plate geometry transducers) and an internal permanent magnet (as in conventional neo or cup geometry transducers). Both magnets may have the same polarity orientation, enabling them to be simultaneously charged after assembly of the transducer's motor structure. A lower one of the permanent magnets uses the yoke as its return path. A low reluctance return path is provided for the upper one of the permanent magnets to improve performance.

Abstract: A speaker with enhanced magnetic flux loop includes a core magnet (12) installed inside hollow space of a bottom yoke (11), and a ring-shape magnet (13) with opposing polarity placed on the outer periphery of the core magnet (12). The ring-shape magnet (13) acts as an induction medium in a magnetic flux loop flowing across the core magnet (12), thus bottom yoke the magnetic flux within the boundary of the yoke (11) and preventing loss of magnetic flux. The dual magnet architecture brings about increased sensitivity to sound and output volume for the speaker, whilst the external dimensions of the conventional speaker can be scaled down as a result of smaller yoke (11).

Abstract: A magnetic circuit for a speaker comprises: a bonded magnet shaped rectangular in top plan view, having on its top face a plurality of grooves formed to extend all the way along two opposing sides thereof and arrayed in parallel with one another at predetermined intervals, and magnetized such that magnetic fluxes at two adjacent grooves are directed inversely to each other; and a plurality of plate-like pole pieces fixedly disposed on the top face of the bonded magnet, and arrayed along the grooves such that two adjacent pole pieces form an air gap located along the center of each groove thereby forming a magnetic gap. And, there is provided a speaker which uses the magnetic circuit thereby achieving a reduced profile.

Abstract: An electromagnetic transducer, such as an audio speaker, includes a return path member which is a pole piece for external magnet geometries or a cup for internal magnet geometries. The magnetic flux return path for the primary drive magnet is through a first portion of the return path member. A first section of a low reluctance magnetic flux return path for a secondary drive magnet is through a second portion of the return path member. A magnetically conductive plate provides a second section of the low reluctance return path from the second portion of the return path member to the secondary drive magnet.

Abstract: An electromagnetic transducer such as an audio speaker, having a push-push geometry in which there are two or more air gaps and the magnetic flux across the air gaps is in the same orientation. If there are more than one voice coil, the voice coils may thus be generating the same electromagnetic polarity by being wound in the same direction about the bobbin, or by being wound in opposite directions and having separate, opposite polarity electrical connections. The transducer exhibits high linearity over a long travel.

Abstract: A speaker has an annular magnet structure. First and second annular magnets are arranged concentrically with each other and connected by a shunt at one end and a pole-defining structure at the other end to concentrate magnetic flux in a cylindrical voice coil gap. The shunt and pole structure are stacked such that the combined magnetic assembly has an opening extending centrally therethrough. A voice coil rides in the cylindrical magnetic flux gap and its leads are brought out through the opening to the other side of the magnet. When used with an enclosure, the diaphragm of the speaker may communicate through the central opening with the volume of a tuned enclosure extending behind the speaker, or the opening may serve as a port of the enclosure, allowing further degrees of control over total acoustics. In one embodiment, annular magnets of axial polarity are oppositely poled, and are positioned concentrically with a space between them.

Abstract: An actuator is provided in which one or more separate compensating coils are employed to alter the distribution of the magnetic flux density in the air gap to produce a substantially constant force throughout the stroke; and in which current in the separate compensating coils can be adjusted with the stroke using separate power supplies and position feedback.

Abstract: A magnetic circuit for a speaker comprises: a bottom yoke including a center pole; a ring magnet; a top plate; and a short-circuiting ring shaped like a hollow cylinder. The short-circuiting ring is disposed close and parallel to a voice coil and attached to the inner portion of the bottom of the top plate.

Abstract: The invention relates to an electromagnetic driver comprising a soft magnetic core in the form of an E with three legs and a back, an alternating field driver, magnetically coupled to the soft magnetic core, for generating an alternating magnetic field in the soft magnetic core, depending upon a sound signal, a constant field driver magnetically coupled to the soft magnetic core for generation of a constant magnetic field in the soft magnetic core, a soft magnetic element for coupling to the plate of the planar diaphragm loudspeaker, lying opposite the back and magnetically closing the legs across at least one small induction gap, whereby the constant field and the alternating field are asymmetrically superimposed such that a resulting force, or a resulting torque on the soft magnetic element, is proportional to the sound signal.

Abstract: A magnetic core for speaker is constructed to include an annular magnet connectable to the body of the speaker, a center magnet mounted in the center of the annular magnet and connectable to the body of the speaker, an annular magnetically conducting plate mounted on the topmost edge of the annular magnet, and a center magnetically conducting plate mounted on the topmost edge of the center magnet for producing a magnetic loop with the annular magnetically conducting plate.

Abstract: A magnetic core for speaker is constructed to include an annular magnet connectable to the body of the speaker, a center magnet mounted in the center of the annular magnet and connectable to the body of the speaker, an annular magnetically conducting plate mounted on the topmost edge of the annular magnet, and a center magnetically conducting plate mounted on the topmost edge of the center magnet for producing a magnetic loop with the annular magnetically conducting plate.

Abstract: An internal magnetic circuit is formed by a plate forming a pole piece, a vertically magnetized magnet attached to a bottom face of the plate, and a yoke attached to a bottom face of the magnet. A magnetic gap is formed between the plate and the yoke. The yoke includes a bottom part attached to the bottom face of the magnet, a side part standing on the side of the plate, and a folded-back part folding downwards over the side part to face the magnetic gap. Thus, the internal magnetic circuit having a uniform magnetic flux density inside the magnetic gap along the direction of its length is provided.

Abstract: An electromagnetic transducer, includes: a first diaphragm disposed in a vibratile manner; a second diaphragm provided in a central portion of the first diaphragm, the second diaphragm being formed of a magnetic material; a yoke disposed in a position opposing the first diaphragm; a center pole provided on a face of the yoke that opposes the first diaphragm; a coil substantially surrounding the center pole; a magnet substantially surrounding the coil; and a thin magnetic plate provided between the magnet and the first diaphragm, an inner periphery of the thin magnetic plate being in overlapping relation to an outer periphery of the second diaphragm.

Abstract: A loudspeaker comprises a motor structure which incorporates a magnetic flux control system including a field winding, a controller connected between a voltage source and the field winding and, a polarity reversal switch preferably located across the filed winding. The magnetic flux control system is operative to produce a magnetic flux, which, depending on the level and polarity of electrical current supplied to the field winding, either reinforces or opposes the static magnetic flux produced by the magnet of the motor structure of the loudspeaker, thus altering the motor strength of the loudspeaker system.

Abstract: Disclosed is a concentric magnetic configuration for a speaker system which can produce a full range of frequency sounds from a single source magnet. The magnetic configuration of the present invention includes a high frequency pole plate and one or more middle yoke iron plate placed directly on a cylindrical permanent magnet wherein at least one magnetic flux controlling slot is formed beneath the high frequency pole plate and the middle yoke plate. The multiple air gaps defined by the pole plate and middle yoke iron produce a full range of frequency magnetic fields which can drive the high, medium, and low frequency voice coils.

Abstract: A magnetic circuit includes an annular magnet magnetized in the axial direction thereof; an annular stacked plate disposed on the magnet and including first and second annular plates; and a yoke facing the inner circumferential surface of the stacked plate across a cylindrical space. Upper and lower magnetic gaps are provided at two axially separated positions in the cylindrical space. A loudspeaker includes the magnetic circuit; a voice coil placed in the upper and lower magnetic gaps; a diaphragm connected to the voice coil; and a frame fixed to the stacked plate and supporting the diaphragm in a vibratable manner. The inner circumferential portions of the first and second annular plates are axially deformed downward and upward, respectively, such that the inner circumferential surface of the stacked plate faces the lower and upper magnetic gaps. The remaining portions of the first and second annular plates are stacked on the magnet.

Abstract: Disclosed is a concentric magnetic configuration for a speaker system which can produce a full range of frequency sounds from a single source magnet. The magnetic configuration of the present invention includes a high frequency pole plate and one or more middle yoke iron plate placed directly on a cylindrical permanent magnet wherein at least one magnetic flux controlling slot is formed beneath the high frequency pole plate and the middle yoke plate. The multiple air gaps defined by the pole plate and middle yoke iron produce a full range of frequency magnetic fields which can drive the high, medium, and low frequency voice coils.

Abstract: An electro-mechancial transducer, including a magnetic assembly producing a magnetic field having two or more displaced regions of greater intensity, having magnetic flex in substantially similar directions, separated by and surrounded by regions of lower intensity magnetic field, and an electrically conductive and mobile member disposed in and capable of moving through a magnetic field.

Abstract: A core having a coil wound thereon is fixed to a base at the bottom. The base is fixed to a case made of synthetic resin by insert molding. A diaphragm is fixed to the case in circumference, and also a magnetic flux guide member is fixed to the case in circumference. Since the diaphragm and the magnetic flux guide member is commonly fixed to the case, no variation in the distance between the diaphragm and the magnetic flux guide member would occur for every product. Further, a gap L is formed between the magnet and the magnetic flux guide member, and an air hole is formed in the magnetic flux guide member. This improves the passage of air and reduces air dumper effect without modifying the magnet in shape.

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: A speaker has an annular magnet structure. First and second annular magnets are arranged concentrically with each other and connected by a shunt at one end and a pole-defining structure at the other end to concentrate magnetic flux in a cylindrical voice coil gap. The shunt and pole structure are stacked such that the combined magnetic assembly has an opening extending centrally therethrough. A voice coil rides in the cylindrical magnetic flux gap and its leads are brought out through the opening to the other side of the magnet. When used with an enclosure, the diaphragm of the speaker may communicate through the central opening with the volume of a tuned enclosure extending behind the speaker, or the opening may serve as a port of the enclosure, allowing further degrees of control over total acoustics. In one embodiment, annular magnets of axial polarity are oppositely poled, and are positioned concentrically with a space between them.

Abstract: The present invention relates to an miniature actuator especially suitable for hearing aid applications. The actuator according to the present invention operates according to the change in reluctance principle. In particular, the actuator according to the present invention operates in a balanced configuration comprising two planar coils, two magnets, a membrane and a spacer chip providing the necessary back chamber volume.

Abstract: A dual magnetic field speaker. The speaker includes two magnets, two yokes, two plates, and a voice coil having an upper winding and a lower winding disposed in an air gap. The speaker generates a constant intensity of magnetic flux that produces two monostable magnetic fields.