Abstract: An electroacoustic transducer includes: a diaphragm; a magnetic circuit having a magnetic gap; a frame that holds the diaphragm and the magnetic circuit; a voice coil having one end portion positioned within the magnetic gap and the other end portion coupled to the diaphragm; and a low friction material that is disposed in a sliding portion formed by the voice coil and the magnetic circuit, and includes polymer compounds swollen with liquid.

Abstract: The loudspeaker magnetic circuit is an external-magnet type, and has a magnet, an upper plate, and a lower plate. The magnet is sandwiched between the upper plate and the lower plate. At least one of the lower plate and the upper plate is formed of magnetic powder or a mixture of a magnetic powder and resin.

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 multi-stranded voice coil wire includes an elastic body and at least a metal wire. The metal wire is twisted around the elastic body, the metal wire being surrounded by an insulating layer, and the insulating layer being surrounded by an adhesive layer. In the present invention, the elastic body and the metal wire of different materials are stranded together, which makes the present voice coil has smaller height as compared to the convention voice coil has the same resistance and the same configuration size. This makes the present voice coil have more strength and longer lifetime, and helps to design a thinner loudspeaker and increases the heat dissipation efficiency of the voice coil.

Abstract: The invention relates to an acoustic loudspeaker which includes a magnetic field source. A mobile apparatus includes a diaphragm and a first winding capable of allowing passage of an electrical current representing the sound signal to be generated and of interacting with the magnetic field. The acoustic loudspeaker includes a second winding, both terminals of which are connected by a resistive component. Both terminals of the second winding are electrically isolated from the terminals of the first winding.

Abstract: A vibrating element includes a diaphragm and a voice coil. The diaphragm has a first surface and a second surface opposite to each other, in which the first surface includes a first conductive region and a second conductive region separated from the first conductive region. The voice coil is disposed at the first surface of the diaphragm, in which two ends of the voice coil are respectively electrically connected to the first conductive region and the second conductive region, and the two ends of the voice coil are located within a region circled by the voice coil on the first surface.

Abstract: A method for fabricating a speaker is disclosed. The speaker is equipped with a case having a through cavity, an inner surface forming the cavity and an outer surface, a magnetic bowl coupled to the case, a magnet positioned in the magnetic bowl, a pole plate covering the magnet, a magnetic gap formed by the magnet and the magnetic bowl, a diaphragm supported by the case and vibrating along a vibrating direction, a voice coil connected to the diaphragm, and a hearing aid coil formed on the case. The method includes the steps of: providing a case made of thermoplastic doped with organometallic additive; activating the organometallic additive in the case by a laser beam for forming initial pattern of the hearing aid coil in the inner surface of the case; and bathing the case in copper solution for providing the initial pattern with copper plating layer.

Abstract: A loudspeaker magnetic motor utilizes a voice coil with two or more wire coils that are connected in parallel and that are layered on top of one another. The motor utilizes, as a magnetic field source, a permanent magnet and, more particularly, a permanent magnet that includes a rare earth metal such as a neodymium boron iron magnet.

Abstract: A loudspeaker magnetic motor utilizes a voice coil with two or more wire coils that are connected in parallel and that are layered on top of one another. The motor utilizes, as a magnetic field source, a permanent magnet and, more particularly, a permanent magnet that includes a rare earth metal such as a neodymium boron iron magnet.

Abstract: A loudspeaker magnetic motor utilizes a voice coil with two or more wire coils that are connected in parallel and that are layered on top of one another. The motor utilizes, as a magnetic field source, a permanent magnet and, more particularly, a permanent magnet that includes a rare earth metal such as a neodymium boron iron magnet.

Abstract: An electromechanical transducer 180, motor structure 200 and voice coil winding support structure or bobbin 210 are configured to protect and transport heat away from a voice coil 220 which is would solely within the interior of bobbin 210 and configured for reciprocating movement in close proximity to an extended cooling pole piece 204. A compact, economical and efficient adaptation of a pancake style motor includes generous volume for a powerful magnet 208, while providing an extended, linear range of excursion and continuous cooling for the generously overhung voice coil 220.

Abstract: An electroacoustical apparatus and method is described that alters the output properties of an audio device to improve the sound properties for both hearing impaired and normal hearing listeners. The device includes a coil element of specific design and may incorporate digital signal processing techniques to modify audio signal output. The electrical device and method of processing provides for the beneficial alteration of sound waves to an audio signal, and further modification of the audio signal to provide for improved loudness and clarity characteristics. The improved characteristics provide for greater intelligibility of the audio signal to persons with hearing impairments and to persons with normal hearing.

Abstract: A bobbin includes a paper matrix and a plurality of carbon nanotubes dispersed in the paper matrix. A loudspeaker includes a magnetic circuit, a bobbin, a voice coil, a damper, and a diaphragm. The magnetic circuit defines a magnetic gap. The bobbin is located in the magnetic gap and includes a paper matrix and a plurality of carbon nanotubes dispersed in the paper matrix. The voice coil is wounded on the bobbin. The damper is fixed to the bobbin. The diaphragm includes an inner rim fixed to the bobbin and held mechanically by the damper.

Abstract: A bobbin for a loudspeaker includes at least one base and at least one carbon nanotube structure. The at least one carbon nanotube structure is positioned on at least one surface of the base. A loudspeaker includes a magnetic circuit, a bobbin; a voice coil, and a diaphragm. The magnetic circuit defines a magnetic gap. The bobbin is located in the magnetic gap and includes at least one carbon nanotube structure. The voice coil is wounded on the bobbin. The diaphragm includes an inner rim fixed to the bobbin.

Abstract: A bobbin is a hollow tubular structure formed of a carbon nanotube composite structure. A loudspeaker includes a magnetic circuit; a bobbin; a voice coil; and a diaphragm. The magnetic circuit defines a magnetic gap. The bobbin is located in the magnetic gap. The voice coil is wounded on the bobbin. The diaphragm includes an inner rim fixed to the bobbin. The bobbin is a hollow tubular structure formed of a carbon nanotube composite structure.

Abstract: A speaker includes a case, a dome, a diaphragm, a first voice coil, a second voice coil, a first pole plate, a second pole plate, a first magnet, a second magnet and a yoke. The case is supported on the frame to form a receiving room therebetween. The yoke includes a bottom portion and a side portion perpendicularly extending upward from the center of the bottom portion. A first magnetic gap is formed between the inner wall of the side portion and the outer wall of the magnet for receiving the first voice coil, and a second magnetic gap is formed between the outer wall of the side portion and the inner wall of the second magnet for receiving the second voice coil.

Abstract: A micro-speaker includes a frame, a yoke received in the frame, a connecting plate received in the yoke, a magnet received in the yoke, a pole plate attached onto the magnet, a diaphragm attached to the frame, a voice coil positioned on the connecting plate and surrounding the magnet, and a case covering the diaphragm. The diaphragm includes a central area in a center thereof, a joint area at an outer periphery thereof, and a connecting area between the central area and the joint area. The connecting plate includes a central portion formed in a central thereof for connecting with the central area of the diaphragm, and an oblique wall obliquely connecting to the central portion. The voice coil is wrapped on the oblique wall.

Abstract: An audio amplifier, that includes a planar inductor structure that includes a first plurality of windings, formed on layers of a first circuit board and a second plurality of windings, formed on layers of a second circuit board. The planar inductor structure may further include a sense winding.

Abstract: The present invention relates generally to a compact speaker with secondary wire suspension. The secondary suspension assembly is the speaker has a suspension assembly with preferably 3 wires which provide stability to reduce wobbling while maintaining linear excursion.

Abstract: A drive cone 11 and a diaphragm 14 are integrally driven by a voice coil 6 movably disposed in a magnetic gap 5. Peripheral edge portions of the drive cone 11 and the diaphragm 14 are supported by a frame 12 via different edge portions 13 and 15, respectively. The drive cone 11 is provided with a rising-up portion 11a which rises up toward an acoustic radiation direction from a inner circumferential end, and a rising-down portion 11b which rises down toward a direction reverse to the acoustic radiation direction. An inner circumferential edge of the diaphragm 14 is fixed at an annular top formed between the rising-up portion and the rising-down portion. Moreover, a first rib 11c and a second rib 11d are formed on the drive cone 11 in such a manner as to rise up toward the acoustic radiation direction integrally with the drive cone. The diaphragm 14 is supported also at the tips of the ribs.

Abstract: A voice coil 6 is movably disposed in a magnetic gap 5. A drive cone (first diaphragm) 11 and a diaphragm (second diaphragm) 14 are integrally driven by the voice coil 6. Peripheral edge portion of the drive cone 11 and the diaphragm 14 are supported by a frame 12 through edge portions 13 and 15, respectively. An annular adhesive receiver 8 is disposed in a peripheral surface of a voice coil bobbin 7 around which the voice coil 6 is wound, and an inner peripheral edge 11a of the drive cone 11 is accommodated in the adhesive receiver 8. The drive cone 11, the adhesive receiver 8 and the voice coil bobbin 7 are connected to each other by an adhesive filled into the adhesive receiver 8.

Abstract: A micro-speaker includes a frame, a yoke received in the frame, a connecting plate received in the yoke, a magnet received in the yoke, a pole plate attached onto the magnet, a diaphragm attached to the frame, a voice coil positioned on the connecting plate and surrounding the magnet, and a case covering the diaphragm. The diaphragm includes a central area in a center thereof, a joint area at an outer periphery thereof, and a connecting area between the central area and the joint area. The connecting plate includes a central portion formed in a central thereof for connecting with the central area of the diaphragm, and an oblique wall obliquely connecting to the central portion. The voice coil is wrapped on the oblique wall.

Abstract: A loudspeaker includes a frame, a magnetic circuit supported by the frame, voice coil body provided movably in relation to a magnetic gap provided at the magnetic circuit, a diaphragm having an outer rim being joined via a first edge to the frame and an inner rim being joined to the voice coil body, and a damper located towards the magnetic circuit from the diaphragm. The damper has an inner rim joined to the voice coil body. The damper has an outer rim joined via a second edge to the frame. The second edge protrudes towards the diaphragm or in a direction opposite to the diaphragm. The damper includes a first protrusion protruding towards the diaphragm and a second protrusion protruding in a direction opposite to a direction in which the first protrusion protrudes. A protrusion out of the first and second protrusions is closest to the second edge among the protrusions.

Abstract: A speaker device includes a magnetic circuit which includes a magnetic gap, a diaphragm which has a recessed part arranged in the magnetic gap and extending in a direction substantially orthogonal with respect to an extending direction of a magnetic flux in the magnetic gap, and a voice coil which is formed into an annular shape and has a first parallel part extending in one direction and a second parallel part extending in a direction in parallel with the first parallel part and opposite to the first parallel part with a constant space. Particularly, the first parallel part and the second parallel part are arranged in a direction in parallel with an extending direction of the recessed part, respectively. The first parallel part is arranged in the recessed part to be positioned in the magnetic gap, and the second parallel part is positioned above the recessed part.

Abstract: A vibrating element (1) for an electroacoustic transducer, particularly for a loudspeaker, is provided, comprising a diaphragm (2) with at least two electrically conductive areas (3a, 3b) separated from each other, and with a recess (4). In the recess (4) a coil (5) is arranged with two connecting leads (6a, 6b), which are electrically contacted with one conductive area each (3a, 3b). The contact points (8a . . . 8d) are then located in the area of the recess (4). Furthermore, a method for the manufacturing of a vibrating element (1) is provided. The recess (4), the inserting of the coil (5) into the recess (4) as well as optionally the contacting of connecting leads (6a, 6b) with the conductive areas (3a, 3b) can then take place in one process step.

Abstract: A speaker may include a voice coil bobbin and a center pole. The voice coil bobbin may include a nonmetallic pipe body as a base of the voice coil bobbin, a first nonmagnetic and electric conductor film which is formed on an inner peripheral face of the pipe body, and a second electric conductor film which is formed on an outer peripheral face of the pipe body such that the first electric conductor film is covered by the second electric conductor film through the pipe body. An electrostatic capacity that is formed between the voice coil bobbin and the center pole is detected and outputted as an electric signal.

Abstract: A thread winding part or a reinforcing wire winding part is formed by winding a heat resistant fiber thread or a reinforcing wire around the voice coil bobbin in contact with both coil ends of the wire winding part or a coil end of the same on a magnetic-circuit side. A bent part bent outward is formed on the lower end of the voice coil bobbin on the magnetic circuit side. This prevents the wire winding part from shifting from its mounting position and from coming off to the lower side. In the resulting voice coil, the wire winding part hardly comes off the voice coil bobbin even if the wire binding of the wire winding part is loosened by Joule heat, speaker vibrations, etc.

Abstract: An armored voice coil assembly comprises a former that is impregnated with a curable resin, preferably polyimide resin. Voice coil wire is wound around the outside surface of the former and is then preferably encased with an outer layer of resin impregnated glass fabric wrapped around the voice coil windings, effectively enveloping the voice coil within inner and outer layers of fabric and resin. The armored voice coil assembly is then cured into a solid shape.

Abstract: A speaker includes a magnetic circuit forming a slit-like magnetic gap, a frame that houses and holds the magnetic circuit, a diaphragm attached to the frame so as to be capable of vibrating, a voice coil unit that is placed so as to pass through substantially the center of the magnetic gap, and has its one end coupled to the diaphragm, and a damper attached to the frame to support the other end of the voice coil unit. The voice coil unit has a planar-type coil bobbin section, and a voice coil section having a coil member wound in a planar track shape and disposed so as to extend through the coil bobbin section from one side to the other side and from the other side to the one side.

Abstract: A voice coil includes a cylindrical bobbin formed of a first material; a coil which surrounds on an outer circumferential surface of the bobbin; and a plurality of reinforcement members formed of a material having a propagation speed faster than the first material and provided on the outer circumferential surface of the cylindrical bobbin.

Abstract: A mobile terminal includes a portable terminal housing and a speaker housing positioned in the portable terminal housing. The speaker housing includes a first micro-speaker having a first frequency response and a second micro-speaker having a second frequency response and positioned proximate the first micro-speaker. The terminal housing further includes a first passageway extending from a front face of the first micro-speaker to a first opening in the terminal housing, and a second passageway extending from a back face of the second micro-speaker to a second opening in the terminal housing displaced from the first opening. A grommet adjacent the speaker housing acoustically separates at least a portion of the first passageway from the second passageway. The first passageway may be completely acoustically separated from the second passageway by the grommet and/or a gasket and/or a foam structure.

Abstract: A speaker device includes a terminal member, a connecting member, a conductive damper and a diaphragm. The connecting member has a terminal mounting part. The terminal mounting part has a projecting part and a connecting part. The connecting member has a hole in its upper end portion and a fixing part at its lower end portion. The terminal member is mounted to the terminal mounting part. At this time, the projecting part is inserted into the hole, and the fixing part is inserted into a groove. Thereby, at positions of two spots, the terminal member is physically fixed to the connecting member. The connecting part is connected to the conductive member of the conductive damper. Thus, a soldering operation of the connecting part and the conductive member can be performed easily. Then soldering is performed for the terminal member, a lead wire of a voice coil and the conductive member.

Abstract: A speaker device includes a terminal member, a connecting member, a conductive damper and a voice coil. The terminal member has a first connecting part, a slit, a hole, a second connecting part and a fixing part. The connecting member has a projecting portion on a bent portion and a groove at an area in the vicinity of a lower end of an outer peripheral wall of the cylindrical portion. The terminal member is mounted to the connecting member. A lead wire is wound around the slit of the connecting part, and a portion thereof is soldered. The projecting portion is inserted into the hole. The fixing part is inserted into the groove. The second connecting part is connected to a conductive member of the conductive damper disposed at the area in the vicinity of the lower end of the outer peripheral wall of the cylindrical portion by the soldering.

Abstract: An audio speaker driver having a voice coil with graduated windings such that different sections of the voice coil have different electrical resistances and/or lengths per unit of height of the voice coil. A center portion of the voice coil gives a greater BL, while outer portions give lower overall electrical resistance, such that the audio speaker driver is highly efficient and linear during low excursion operation, with a smoother transition from the linear region to the grossly non-linear region. The wire of the graduated voice coil can have varying cross-sectional area over its length, can be wound on varying on-center spacing, can be wound in different numbers of layers in the various sections, and/or it can fork into interlaced, parallel windings.

Abstract: There is provided a speaker apparatus manufactured by using a voice coil configured so that a lead wire electrically connected to a coil is clamped between an insulating sheet and a bobbin.

Abstract: In an electroacoustic transducer, a pair of coil terminals elongating from a voice coil are electrically connected to a pair of terminal members attached to a frame via a flexible printed circuit board, respectively. According to the configuration, even in a case where an electroacoustic transducer is used at a high sound pressure, breakage of the coil terminals hardly occurs. In the flexible printed circuit board, the width of an intermediate portion is set to be smaller than the widths of an end portion on the side of the coil terminals and an end portion on the side of the terminal members. Therefore, the flexibility of the intermediate portion can be enhanced, whereby transmission of characteristic vibration of the flexible printed circuit board to a diaphragm, and stress concentration in the vicinity of the end portions are effectively suppressed.

Abstract: An acoustic driver has a voice coil in which adjacent turns of the coil are spaced apart. The driver is placed at one end of a foam-lined, elongated structure, such as a tube. An opposing end of the structure is, in one embodiment, enclosed by a wall that is connected to the structure by a suspension so that it moves in sympathy with the driver. In another embodiment, the structure cooperates with the acoustic driver to form one or more restrictive passageways confined around the driver's motor and an inner surface of the structure. The passageway(s) couple a volume of air in the structure to the exterior of the structure in a manner that reduces the transmission of acoustic energy without creating alternating pressure within the structure that interferes with the movement of the voice coil's diaphragm, at its maximum points of excursion.

Abstract: A lead wire of a voice coil is wired along the surface of a diaphragm. The lead wire is bent toward a reverse side of the diaphragm at a peripheral edge portion of the diaphragm. The lead wire is led to the interior of a frame. An external terminal is provided to extend from outside to inside the frame. In addition, a connecting portion for connecting the lead wire and the external terminal is provided inside the frame. The connecting portion is prevented from coming into contact with another part and becoming short-circuited.

Abstract: The two coil spring terminals have the structure of double coil spring terminal including a small diameter coil spring terminal and a large diameter coil spring terminal. In this case, a terminal holder is provided with a clamping portion for clamping the large diameter coil spring terminal between the terminal holder and an internal circuit board. Specifically, the terminal holder is formed, in an upper end portion of its outer peripheral surface, with an annular groove which is adapted to be engaged with a small diameter portion formed in an upper end portion of the large diameter coil spring terminal. This omits fixation of the large diameter coil spring terminal to the internal circuit board, and necessity of soldering the two coil spring terminals respectively to the internal circuit board as a conventional art, enhancing mounting workability of the terminal holder.

Abstract: An evenly elastically deformable damper for speaker is disclosed to include a damper body of a plain weave fabric having elastic warp wires and weft wires intercrossed in X and Y directions and a center through hole cut through the top and bottom surfaces and bonded to a voice coil, a plurality of reinforcing patches stitched to the damper body in a crossed manner around the center through hole of the damper body to secure lead wires to the damper body and formed of a plain weave fabric having elastic warp wires and weft wires intercrossed in direction A and direction B at about 45° relative to X and Y directions to keep the damper body in balance and to prevent damage of the lead wires when vibrated with the voice coil.

Abstract: An electro-acoustic transducer wherein a stopper of a terminal is composed of an elastic body having an impulsive-force resistance and an excellent resilience. The stopper is mounted on the yoke or lower plate of magnetic circuit, which is made of a metallic material having an impulsive-force resistance. In this way, the stopper can restrict the terminal within the reversibility limit value of the spring force of the metallic material, and hence can enhance the reliability.

Abstract: A diaphragm subassembly comprises a voice coil, a diaphragm, a frame, and a pair of terminal members. A magnetic circuit unit comprises a yoke, a magnet, and a base. The diaphragm subassembly and the magnetic circuit unit are accommodated in a bottomed cylindrical cover. In the manufacturing process, the cover is placed with the open end directed upward. The diaphragm subassembly, the yoke, the magnet, and the base are dropped into the cover in this order. The manufacturing process of a dynamic electroacoustic transducer is thereby simplified.

Abstract: A small earphone or headphone which can produce a wide band acoustic output from a low-pitched tone to a high-pitched tone and can generate a body-sensitive vibration independent output or a body-sensitive vibration output synchronized with a music. The earphone or headphone is mounting a vibration actuator which is provided with a magnetic circuit including a permanent magnet, a yoke, and a plate for concentrating the flux of the permanent magnet, with a coil disposed in an air gap of the magnetic circuit, with a diaphragm fixed with the coil and being imparted with a driving force therefrom, and with a vibration transmitting section for supporting the magnetic circuit flexibly through a suspension comprising a flexible spring.

Abstract: An electromagnetic transducer is described including a magnet assembly (50) and a conductive drive coil (52). The magnet assembly provides an emanating magnetic field within which the drive coil is located. The drive coil is a flat ring coil having a width that is equal to or greater than its height. As assembled, the drive coil is mounted in close proximity to the magnet assembly such that relative axial motion may occur between them during use. In one embodiment, the magnet assembly includes two permanent disc magnets (64), (66) having axial magnetizations and being oriented with like poles facing one another to produce a radially emanating magnetic field. In another embodiment, the magnet assembly includes a pair of axially magnetized permanent ring magnets (64), (66) also oriented with like poles facing one another.

Abstract: A loud speaker includes a circuit board and a base. The circuit board includes a plurality of contacts on a side thereof. The base is formed of plastic material by injection molding. The base includes an insertion groove in an end thereof. The circuit board is embedded in the insertion groove. The base further includes a plurality of grooves in communication with the insertion groove. The grooves are respectively aligned with the contacts of the circuit board. The circuit board is placed in a mold for forming the base and the circuit board is embedded in the base after formation of the base by injection molding.

Abstract: A speaker includes a substantially rectangular case having connection terminals at corners, a substantially rectangular voice coil, a diaphragm, and a substantially rectangular magnetic circuit. A lead drawn out from a corner of the voice coil in proximity to one of the connection terminals extends to the vicinity of another corner on a shorter side of the voice coil. The lead is bent, and then is connected to the connection terminal. This configuration can provide a speaker for use in portable equipment, such as a portable telephone, that can meet the requirements of space reduction without impairing characteristics, such as sound quality and sound pressure, and has excellent connection reliability of the terminal and reduced cost.

Abstract: A speaker interconnection block with two voice coils to be driven with separate amplifiers, or to use one amplifier to drive the two voice coils in series or parallel without having to reinterconnect the voice coils. This is achieved by locating the negative voice coil terminals next to each other and the positive voice terminals next to each other on the connection block. When two amplifiers are used to drive the voice coils, the sequence of connections of the amplifiers matches those of the voice coils mentioned above. When only one amplifier is used, that amplifier is connected between the two amplifier terminals farthest from each other. To connect the voice coils in series a single jumper is used to interconnect the two terminals in the center, and for parallel connection two jumpers are used to connect to two terminals at the ends of the sequence together separately.

Abstract: An improved structure for the sound coil of loudspeaker comprises a cylinder provided with multiple layers of coils surrounding one end thereon. The coils are divided into sections in the middle position which provide more than two conducting wires. The cylinder is rolled by a single plate and is provided with four layers of coils. The conducting wire extends to the other end of cylinder and is wrapped with oilpaper; and connects to a piece of thick wire. The cylinder is provided with several ventilation holes. Every two layers of coil being a independent wire material, the sound coil comprised four conducting wires; or each layer of coil being a independent wire material, the sound coil comprised eight conducting wires. Thus the sound coil produces larger output power and reduces the size of sound coil, the coils surrounding the cylinder, production costs, and the size of products.

Abstract: Supplemental portions are added to lead portions of a voice coil attached to a coil bobbin. The supplemental portions each has a shape, which can be restored repeatedly in response to stress, applied to the lead portions. In the case where stress is exerted on the lead portions under the influence of the pulling stress and compressive stress produced in the winding portion when a large driving current is supplied to the voice coil, the supplemental portions are deformed, thereby preventing the wire breaking at the lead portions.

Abstract: An electromagnetic transducer is described including a magnet assembly (50) and a conductive drive coil (52). The magnet assembly provides an emanating magnetic field within which the drive coil is located. The drive coil is a flat ring coil having a width that is equal to or greater than its height. As assembled, the drive coil is mounted in close proximity to the magnet assembly such that relative axial motion may occur between them during use. In one embodiment, the magnet assembly includes two permanent disc magnets (64), (66) having axial magnetizations and being oriented with like poles facing one another to produce a radially emanating magnetic field. In another embodiment, the magnet assembly includes a pair of axially magnetized permanent ring magnets (64), (66) also oriented with like poles facing one another.