Magnetic circuit and speaker

Abstract

To provide a loudspeaker and a magnetic circuit for the loudspeaker.SOLUTION: A magnetic circuit assembly may be used in a loudspeaker. A magnetic circuit may include first and second plates, a magnet, and a yoke. The first plate can have a distal surface and a proximal surface. The second plate may have a distal surface and a proximal surface opposite the distal surface. The distal face of the second plate may be disposed along the proximal face of the first plate. At least one of the first and second plates can have a first radial portion with a smaller axial dimension than a second radial portion. A magnet can have the distal surface and the proximal surface such that the distal surface of the magnet is disposed along the proximal surface of the second plate. A yoke can form first and second magnetic circuit gaps in a radial direction between the yoke and each of the first and second plates.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure generally relates to loudspeakers and magnetic circuits for loudspeakers.

Background Art

[0002] Loudspeakers provide high-quality sound that can be heard by listeners from a distance through various media. Various configurations of loudspeakers have been developed over the years. Current loudspeakers have several functions related to the development of magnetic circuits and the conversion of electrical energy into sound waves. Various magnetic circuit assemblies have been developed to conduct magnetic fields in various electrical devices including loudspeakers. However, in the technical field where this application provides solutions, certain features are lacking and multiple problems exist. As documents related to this technical field, Patent Document 1 and Patent Document 2 exist.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

[0004] The exemplary embodiments described herein have innovative features, only one of which is not essential for their desirable attributes or solely responsible for them. Without limiting the scope of the claims, some advantageous features are summarized here.

[0005] In some embodiments, the magnetic circuit assembly may be used in a loudspeaker. The magnetic circuit may include a first and a second plate, a magnet, and a yoke. The first plate may have a distal surface and a proximal surface. The second plate may have a distal surface and a proximal surface on the opposite side of the distal surface. The distal surface of the second plate may be disposed along the proximal surface of the first plate. At least one of the first or second plates may have a first radial portion with an axial dimension smaller than a second radial portion. The magnet may have a distal surface and a proximal surface such that the distal surface of the magnet is disposed along the proximal surface of the second plate. The yoke may be capable of forming first and second magnetic circuit gaps in the radial direction between the yoke and each of the first and second plates.

[0006] The following drawings and related descriptions are provided to illustrate embodiments of the present disclosure and are not intended to limit the scope of the claims.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 8

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Figure 10

Best Mode for Carrying Out the Invention

[0008] Here, with reference to the drawings summarized above, these and other features will be described. The drawings and the associated description are provided to illustrate embodiments and are not intended to limit the scope of any claims. Throughout the drawings, reference numerals may be reused to indicate the correspondence between the elements being referenced. Additionally, where applicable, the first one or two digits of the reference numeral for an element often indicate the number of the drawing in which the element first appears.

[0009] Specific embodiments and examples are disclosed below, but the subject matter of the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and / or uses, and their modifications and equivalents. Accordingly, the appended claims are not limited by any of the specific embodiments described below. For example, in any method or process disclosed herein, the operations or acts of the method or process may be executed in any suitable order and are not necessarily limited to any particular disclosed order. The various operations may be described sequentially as a plurality of individual operations in a manner that may be helpful in understanding the particular embodiments, but the order of description should not be construed as meaning that these operations are order-dependent. Further, the structures, systems, and / or devices described herein may be embodied as integrated components or as separate components. For purposes of comparing the various embodiments, specific aspects and advantages of these embodiments are described. Not all such aspects or advantages are necessarily achieved by a particular embodiment. Thus, for example, the various embodiments may be implemented to achieve or optimize one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as may be taught or suggested herein.

[0010] Existing magnetic circuits are sufficient for certain purposes. However, there is a need to enhance the magnetic performance that can enable previous designs, and even previous dual-gap designs. The design goals of a magnetic circuit can include reducing distortion over a wide range of voice coil positions and improving the control of the movement of the transducer. In this specification, for example, design examples that can enable the improvement of magnetic circuit performance by combining multi-gap (e.g., dual-gap) technology with a multi-magnet (e.g., dual-magnet) topology will be described. The designs described in this specification can enable the generation of a very strong magnetic gap compared to previous known multi-gap designs, and thus can provide a highly efficient transducer design. A particular design can enable the reduction of the depth of a motor by using a particular dual-gap design. For example, a standard gap design can have a depth of nearly 25 mm with similar performance to satisfy the same linear force applied to a desired voice coil (“Xmax”) displacement. The particular designs described in this specification can help reduce the inductance of the voice coil compared to using a standard single-gap motor design. For example, an optimized dual-gap design can enable the creation of an assembly with fewer required tools because certain components (described later) can be used multiple times (e.g., twice) within a single assembly, such as by inverting the components 180 degrees.

[0011] By reducing the motor depth, it is possible to reduce the height of the voice coil (often referred to as the "winding width" (WW)) while still achieving the BL gap width to meet the target Xmax. This enables strong low-frequency (LF) performance with a low total harmonic distortion (THD). Additionally or alternatively, this also allows for a reduction in the internal inductance of the coil, thus reducing distortion and improving high-frequency (HF) extension. The output of the specific speaker embodiments described herein can be as large as 117 dB over a relatively small form factor and a wide operating frequency range (e.g., 70 - 5,000 Hz). Thus, the motor topologies described herein can achieve high motor force with a small form factor, enabling high acoustic output. Additionally or alternatively, the described topologies allow for a reduced WW and thus can reduce mass and inductance, which can be two main inhibiting factors in achieving high transducer efficiency.

[0012] Additionally or alternatively, the topologies described herein can provide improved low-frequency performance. The described topologies can achieve a high Xmax with a small form factor. The saved depth can provide clearance for the movable region to move within the transducer, such that the transducer can generate the target low-frequency acoustic output level. Additionally or alternatively, the designs herein can have improved heat dissipation due to a clear heat path from the motor assembly.

[0013] This specification describes a system for a loudspeaker and a magnetic circuit assembly. Although the description herein relates to loudspeakers and magnetic circuits, it can be understood that one or more features of the present disclosure can also be implemented in other electrical devices such as generators, electromagnets, electric motors, linear actuators, vibration transducers, etc. Some embodiments of the methods and related systems disclosed herein can be used with various loudspeaker designs.

[0014] Unless otherwise expressly indicated, the terms used in this specification are understood to mean their ordinary meaning in the common usage within the relevant technical field.

[0015] FIG. 1 schematically shows a cross-section of a loudspeaker 100 in the form of a ring magnet. The loudspeaker 100 may include one or more components described herein. However, since not all elements of the loudspeaker 100 are required in all embodiments, no single element should be regarded as indispensable to the loudspeaker 100. The loudspeaker 100 shown in FIG. 1 represents a circular magnet (ring or annular magnet) form. However, a core magnet form (slug or internal magnet type) as well as an oval or rectangular magnet form may also be implemented with appropriate adjustments using a magnetic circuit design and configuration substantially similar to those described herein. An example of such an embodiment is provided by FIG. 3. The slight differences between the form of FIG. 1 and the form of FIG. 3 will be apparent to those skilled in the art and are omitted for clarity and brevity.

[0016] The loudspeaker 100 is shown with a central axis A about which the loudspeaker 100 has substantially radial symmetry. Thus, FIG. 1 represents elements that may appear to be replicated but represent common elements arranged around the axis. However, in some designs, multiple elements may be used for a single feature.

[0017] Loudspeaker 100 includes a frame 106. In some embodiments, frame 106 may be referred to as a basket or housing. At or near a first end of frame 106, the frame may be attached to the front plate assembly 154 of magnetic circuit assembly 150. Front plate assembly 154 may include a receiving portion (not shown) for receiving the attachment of frame 106. Frame 106 may be attached (e.g., adhered), joined (e.g., soldered, welded), or fixed in another way to front plate assembly 154. For example, in some embodiments, a press fit configuration may be used. In some designs, one or more screws, rivets, or mechanical fasteners may be used to attach frame 106 to front plate assembly 154. In some embodiments, frame 106 may be attached to elastic connector 108 at or near a second end of the frame. In some embodiments, frame 106 may be attached directly to diaphragm 110.

[0018] In some embodiments, front plate assembly 154 can include one or more plates and / or one or more magnets. For example, as shown in FIG. 2, front plate assembly 154 can include a first plate 302, a second plate 304, a second magnet 306, and / or an upper end cap 308. Additionally or alternatively, front plate assembly 154 can include a short-circuit ring 320. These features are described in more detail below. Thus, in some embodiments, frame 106 may be coupled to second magnet 306, upper end cap 308, and / or different elements described herein.

[0019] Frame 106 may comprise a thin plate of a rigid material (e.g., steel, plastic, synthetic resin, wood). In some embodiments, frame 106 includes a non-magnetic material (e.g., aluminum or an aluminum alloy), although a ferromagnetic material such as steel may be used. Frame 106 may also be attached to damper 112. Frame 106 may exhibit radial symmetry or substantially radial symmetry about central axis A.

[0020] Elastic connector 108 may be referred to as a surround, an elastic edge, or an outer suspension. Elastic connector 108 may be joined to frame 106. Elastic connector 108 may be attached to frame 106 using an attachment device. For example, in some designs, gaskets can be used. In some embodiments, elastic connector 108 includes a thin sheet of a rigid or elastic material. Since elastic connector 108 includes a sufficiently thin material, even if the material is rigid, it can support a slight perturbation between frame 106 and diaphragm 110.

[0021] Loudspeaker 100 may also include damper 112. Damper 112 may be referred to as a spider or an inner suspension in some embodiments, although other terms may be used. The first end of damper 112 may be connected to frame 106 closer to the first end than the second end of frame 106. The second end of damper 112 may be attached to bobbin 102. Damper 112 may support bobbin 102 to allow bobbin 102 to vibrate while preventing or reducing contact between bobbin 102 or coil 104 and components of magnetic circuit assembly 150 (e.g., front plate assembly 154, pole piece 158). Bobbin 102 may be attached to damper 112 in several different ways (e.g., adhesively, bonded). In some embodiments, damper 112 may include a resin-containing cloth. Damper 112 may comprise a resin plate forming a ring. As in the case of FIG. 1, as shown from the side, damper 112 may be radially corrugated. The radial corrugations may be formed concentric with central axis A.

[0022] Loudspeaker 100 may generally include a diaphragm 110. When the diaphragm vibrates, sound can be generated and / or amplified. The diaphragm 110 may also be referred to as a cone (e.g., a sound cone). Generally, the diaphragm 110 has a hole at the center of the diaphragm 110 and thus forms a ring, although a flat plate shape may be used. The diaphragm 110 may include an elastic material (e.g., resin, cloth, plastic, paper, fiber, etc.). In many embodiments, the diaphragm 110 is radially symmetric about the central axis A. In such embodiments, sound can be concentrated in a direction along the central axis A. The diaphragm 110 may be attached to or near the first end of the bobbin 102 (e.g., the inner circumference of the diaphragm 110). The elastic connector 108 may be attached to the outer circumference of the diaphragm 110 (e.g., joined, adhered). Thereby, the diaphragm 110 can be engaged with the coil 104.

[0023] A cap 114 may be attached near the inner circumference of the diaphragm 110. The cap 114 may be referred to as a dome, a dust cap, or a dust cover in various embodiments. The cap 114 can be centered on the central axis A. In some embodiments, the cap 114 may be coaxial with the pole piece 158 and / or the yoke assembly 160. The cap 114 may "close" the bobbin 102. As shown in the figure, in some designs, the cap 114 has a dome shape. The cap 114 may not be necessary when its geometric shape is formed into the diaphragm 110 or when a flat plate is used.

[0024] In some embodiments, the loudspeaker 100 includes a bobbin 102. In some embodiments, the bobbin 102 may be referred to as a former or coil former. The bobbin 102 may form a ring surrounding a central axis A. In some designs, the bobbin 102 extends axially at least to the axial position of the front plate assembly 154. Thus, the bobbin 102 may form a cylindrical shape. However, the bobbin 102 may extend further, as shown in FIG. 1. Other alternatives are possible. As shown, the diaphragm 110 and / or the damper 112 may be attached (e.g., joined, adhered) to or near the first axial end of the bobbin 102. Non-circular bobbins having a generally rectangular or rectangular shape as required by the loudspeaker configuration are also possible.

[0025] The bobbin 102 may be configured to support a coil 104. The coil 104 may be referred to as a voice coil in some embodiments. The coil 104 may be composed of a conductor wound through one or more complete windings having a closed shape around the bobbin. The coil 104 may be attached to or otherwise fixed to the bobbin 102 using several means (e.g., adhesion, joining). The coil 104 may be configured to receive an electric current. The electric current results in a magnetic field that interacts with the magnetic field generated by the magnet 152. For example, the interaction may cause the coil 104 to translate axially back and forth. This interaction can vibrate the coil 104, and thus the bobbin 102, axially and / or radially along the central axis A. The vibration can be transmitted, for example, to the diaphragm 110 to generate a desired sound based on an electrical input.

[0026] Coil 104 may comprise a series of windings of a conductive material (e.g., metal) wound around bobbin 102. The windings may have a radial thickness extending radially from bobbin 102. The radial thickness may be less than the gap (not numbered in FIG. 1) between front plate assembly 154 and pole piece 158. For example, coil 104 may be disposed between the outer radius of pole piece 158 and the inner radius of front plate assembly 154. In some designs, coil 104 comprises the same number of windings (e.g., turns) of conductive material axially along the portion of bobbin 102 to which it is fixed. By having such a uniform distribution of windings, a more uniform magnetic field can be provided along the height of coil 104 (e.g., measured axially). The height of coil 104 may be less than the corresponding height of a portion of front plate assembly 154 and / or pole piece 158.

[0027] Loudspeaker 100 generally includes magnetic circuit assembly 150. Generally, magnetic circuit assembly 150 may include front plate assembly 154, magnet 152, and yoke assembly 160. Yoke assembly 160 may comprise back plate 156 and / or pole piece 158. Similar to the other elements described with reference to FIG. 1, the elements of magnetic circuit assembly 150 are shown only schematically. For example, front plate assembly 154 may comprise one or more elements. For example, as described above, front plate assembly 154 may include first plate 302, second plate 304, second magnet 306, and / or other elements. Similarly, magnet 152, back plate 156, and / or pole piece 158 may comprise one or more elements.

[0028] In some embodiments, the front plate assembly 154 can be axially adjacent to the magnet 152 and have a common central axis with the central axis A of the magnet 152. However, other arrangements are also possible. The front plate assembly 154 may be fixed to the magnet 152. For example, the front plate assembly 154 may be attached using an adhesive (e.g., glue) or joining techniques. The region where the front plate assembly 154 is attached to the magnet 152 can be referred to as an interface layer. It may be advantageous to reduce the distance (e.g., any gap) between the front plate assembly 154 and the magnet 152, such as the thickness of the interface layer that can include an adhesive or other connection material. Various embodiments of the front plate assembly 154 will be described in more detail below.

[0029] The magnet 152 may be used to provide magnetic flux across the gap between the front plate assembly 154 and the pole piece 158. The magnet 152 may be a permanent magnet (e.g., including an iron-based material such as neodymium and / or ferrite) or an electromagnet (e.g., a temporary magnet). For example, the ring magnet form may include ferrite, and / or the core magnet form may include neodymium. Other variations are also possible, including variations using other types of magnetic materials. In some embodiments, the first magnet 152 may be configured to generate a higher magnetic flux than ferrite. For example, the first magnet 152 may include a rare earth material such as neodymium and / or other rare earth magnetic materials. In certain embodiments, the magnetic circuit includes one or more magnets having a remanence (Br) that is about two to about eight times greater than the remanence of a ferrite magnet. In some embodiments, the magnetic circuit includes one or more magnets having an energy product (BH max) that is about two to about twenty times greater than the energy product of a ferrite magnet. For the same size, a neodymium magnet produces a stronger magnetic field and higher magnetic flux than a ferrite magnet. A neodymium magnet also has a higher magnetic saturation point compared to a ferrite magnet, resulting in a higher magnetic flux. A neodymium magnet may also be referred to as a NdFeB magnet.

[0030] The magnet 152 may be disposed between the front plate assembly 154 and the back plate 156 of the yoke assembly 160. The magnet 152 may be oriented to generate a magnetic field axially through the first and second surfaces of the magnet, with the first surface on the opposite side of the second surface. For example, the poles of the magnet may be oriented parallel to axis A. In some designs, the second surface has an inner radial region and an outer radial region, which will be described in more detail below.

[0031] The yoke assembly 160 (e.g., the back plate 156) may be fixed (e.g., attached) to the magnet 152 at the surface of the magnet 152 opposite the surface to which the front plate assembly 154 is fixed. The yoke assembly 160 may be attached using an adhesive (e.g., glue), bonding techniques, or any other suitable technique. It may be advantageous to reduce the distance (e.g., gap and / or interface layer) between the front plate assembly 154 and the magnet 152, such as that caused by adhesion or other attachment means. Various embodiments of the yoke assembly 160 (including the back plate 156 and / or the pole pieces 158) will be described in more detail below.

[0032] FIG. 2 shows a schematic cross-sectional view of an exemplary embodiment of the ring magnet form of the loudspeaker 100. Elements that are generally numbered may include the functions of the numbers described elsewhere in this specification. The loudspeaker 100 may include a magnetic circuit assembly including a magnet 152, a front plate assembly including a first plate 302 and a second plate 304, and a yoke 360. The first plate 302 and / or the second plate 304 may be separately manufactured (e.g., forged) and attached to the magnet 152. The frame 106 may be attached to the magnet 152 or other parts of the front plate assembly. In some embodiments, the frame 106 may be attached radially adjacent to and / or below the back plate 156. This may help dissipate heat from the loudspeaker 100. As shown in FIG. 2, the coil 104 may be disposed between the bobbin 102 and the front plate assembly. The height of the coil 104 (measured axially) may be lower than the height of the front plate assembly. Thereby, the ratio of the coil 104 within the target region of the magnetic flux can be made larger. For example, such a region is a region having a relatively consistent magnetic flux across the region (see also FIG. 8 below).

[0033] The second plate 304 may be disposed adjacent to the magnet 152. Additionally or alternatively, the first plate 302 may be disposed adjacent to the first magnet 152. The distance between the second plate 304 (and / or the first plate 302) and the magnet 152 may be less than 0.5 mm. For example, this distance may be about 0.1 mm. The distance may include an adhesive gap between the respective components. In some embodiments, the cross-section of the first plate 302 forms an L-shape. The first plate 302 may include a material having a high magnetic permeability such as iron or steel. In some embodiments, the cross-section of the second plate 304 forms an L-shape. In some embodiments, the first plate 302 and the second plate 304 may be substantially identical but may be oriented differently from each other. For example, the first plate 302 and the second plate 304 may be oriented as mirror images of each other (e.g., with respect to a horizontal plane). Thereby, a vertical gap may be formed between the first plate 302 and the second plate 304. In some embodiments, the vertical gap may be closer to the coil 104 than the portions of the first plate 302 and the second plate 304 that are disposed along each other. For example, as shown in FIG. 2, the vertical gap may be disposed between the radially inner portions of the first plate 302 and the second plate 304. However, in other embodiments (e.g., see FIG. 3), the vertical gap may be disposed between the radially outer portion of the first plate 302 and the radially outer portion of the second plate 304. As shown in FIG. 2, at least a portion of the first plate 302 may be disposed between the magnet 152 and the second plate 304. The first plate 302 and / or the second plate 304 may include a metal such as steel (e.g., low-carbon steel), iron, and / or a composite material (e.g., a metamaterial that may have a higher magnetic permeability than a metal or metal alloy).

[0034] As shown in FIG. 2, at least one of the first plate 302 and / or the second plate 304 may have a first radial portion with an axial dimension smaller than that of the second radial portion. The first radial portion (having a smaller axial dimension) may be disposed radially inward of the second radial portion with respect to axis A, as shown in FIG. 2. However, as shown in FIG. 3, in some embodiments, the first radial portion may be disposed radially outward of the second radial portion with respect to axis A.

[0035] As shown in FIG. 2, the distal surface of the second magnet 306 may be disposed distally beyond the most distal surface of the yoke 360. As used herein, "distal" may refer to the surface closest to the elements of the loudspeaker 100 that emit speaker sound (e.g., the elastic connector 108, the diaphragm 110, the cap 114). The "distal" end of the speaker may sometimes be referred to as the "upper end" of the speaker. In contrast, the "proximal" end of the speaker may generally refer to the side of the speaker with the yoke 360, such as the backplate of the yoke 360. The proximal end of the speaker may correspond to the "lower end" of the loudspeaker. Thus, the second magnet 306 may have a surface disposed higher than or above the highest surface of the yoke 360. This arrangement may facilitate the passage of magnetic flux through the outside air above the second magnet 306 and / or various distal elements of the loudspeaker 100 (e.g., the frame 106, the damper 112, the diaphragm 110). Thus, the second magnet 306 may be disposed relative to the yoke 360 such that the frame 106 is configured to conduct magnetic flux from the second magnet 306. Additionally or alternatively, the most distal surface of the first plate 302 may be disposed proximally (e.g., downward) relative to the most distal surface of the yoke 360. This arrangement may further facilitate the flow of magnetic flux through the frame 106. However, in some embodiments, the most distal surface of the first plate 302 may be distal (e.g., upward) relative to the most distal surface of the yoke 360. The term "shell pot" can be used interchangeably with "yoke" or can be considered a type of yoke. The shell pot may form a magnetic structure similar to a pot or shell-like housing that can enclose the magnet and help concentrate the magnetic field in a desired region. The second magnet 306 may include one or more characteristics of the first magnet 152 described above. For example, the second magnet 306 may include a rare earth material such as neodymium and / or other rare earth magnetic materials. The second magnet 306 may have a proximal surface disposed along the distal surface of the first plate 302.

[0036] The upper cap 308 may be disposed along the distal surface of the second magnet 306. The upper cap 308 may facilitate good coupling of the second magnet 306, the first plate 302, and the second plate 304. For example, coupling elements (e.g., screws, nails, rivets, or other mechanical fasteners) may pass through these elements, and the upper cap 308 may be coupled to the ends of the coupling elements to provide a rigid assembly. In some embodiments, the upper cap 308 is the uppermost element of a front plate assembly (e.g., front plate assembly 154). Further details regarding the front plate assembly shown in FIG. 2 are described with respect to FIG. 6 below.

[0037] The loudspeaker 100 may further include a short - circuit ring 320. The short - circuit ring 320 may be disposed between the bobbin 102 and the yoke 360. Further details regarding the short - circuit ring 320 are described below. The yoke 360 may be solid along the central axis A. Alternatively, as shown in FIG. 2, the yoke 360 may include ventilation holes 356 therein. The ventilation holes 356 may help cool the loudspeaker 100 and / or the magnetic circuit assembly.

[0038] As described above, a core magnet form may be used instead of the ring magnet form. Many of the components used in the core magnet form are the same as or similar to those described with respect to the ring magnet form. FIG. 3 schematically shows a cross section of a loudspeaker 100 with a core magnet form. As shown, the coil 104 may be disposed between the pole piece 158 and the bobbin 102 and / or the front plate assembly 154. The bobbin 102 may be disposed between the coil 104 and the front plate assembly 154. As shown, the pole piece 158 may be disposed radially outward from the magnet 152 and / or the front plate assembly 154. The loudspeaker 100 may include a vent hole 356. In some embodiments, the loudspeaker 100 with a core magnet form may include a shorting ring (not shown). One or more shorting rings may be disposed near the pole piece 158 and / or the front plate assembly 154, such as between the pole piece 158 and the coil 104. As described herein, other variations are possible.

[0039] FIG. 4 shows a schematic cross-sectional view of an exemplary embodiment of the core magnet configuration of the loudspeaker 100. The radial orientation of the magnetic circuit assembly is essentially opposite to the orientation of the assembly of FIG. 2 with respect to the central axis A. For example, in some embodiments, the axial gap between the first plate 302 and the second plate 304 may be disposed at the radially outer portions of the first plate 302 and the second plate 304 with respect to the axis A. According to some embodiments, the short-circuit ring 320 may be disposed within the axial gap as shown. As shown, in some embodiments, the coil 104 is disposed between the yoke 360 and the bobbin 102. The height of the coil 104 (measured axially) may be less than the height of the second plate 304. Further details of the magnetic circuit assembly and other elements of the loudspeaker 100 are provided below (e.g., with respect to FIGS. 1 and 6). As shown in FIG. 4, the loudspeaker 100 may not include ventilation holes. Additionally or alternatively, one or more coupling elements (e.g., screws, nails, or other mechanical fasteners) may be used to maintain the physical proximity of the plurality of magnetic circuit elements, such as the front plate assembly, together. As shown, a central screw is used to couple the upper end cap 308, the second magnet 306, the first plate 302, the second plate 304, the first magnet 152, and the yoke 360 to each other. Other arrangements are possible.

[0040] FIG. 5 shows a schematic cross-sectional view of a portion of a magnetic circuit assembly 150 that can be used, for example, in a loudspeaker. In some embodiments, pole pieces 158 may be used to complete the magnetic circuit within the magnetic circuit assembly 150. In some designs, the pole pieces 158 include one or more vent holes (e.g., hollow portions extending axially through the pole pieces 158) not shown in FIG. 1. Such vent holes can be beneficial for cooling the magnetic circuit assembly 150 and / or the loudspeaker 100. The one or more vent holes may be disposed axially downward of the coil 104 (e.g., between the magnet 152 and the pole piece 158). Accordingly, the one or more vent holes may be disposed radially from axis A. The loudspeaker 100 can include a plurality of vent holes, such as 3, 4, 6, or 8. When a plurality of vent holes are included, they may be disposed symmetrically in the radial direction. The one or more vent holes can be used to improve cooling, reduce mechanical resistance, and / or reduce air noise. Vent holes disposed around axis A may be more effective at reducing mechanical resistance, while outer peripheral vent holes may be more effective at cooling the magnetic circuit (e.g., particularly the coil 104). Such outer peripheral vent holes can promote cooling air over the coil.

[0041] The magnetic pole piece 158 may be shaped to accommodate different needs of various embodiments. In some embodiments, the magnetic pole piece 158 may be tapered at one end (e.g., front, rear). This can reduce manufacturing requirements, for example, to enable size and weight requirements suitable for a loudspeaker or to optimize the amount of magnetic flux passing through the magnetic pole piece 158. As shown in FIG. 5, some embodiments include a T-shaped magnetic pole piece 158 that can be useful for optimizing the target width (e.g., radial width) of the gap 204. However, in other embodiments, the magnetic pole piece 158 does not include a T-shape. In some designs, the magnetic pole piece 158 may include a surface on the opposite side of the generally smooth and / or flat magnet 152. The surface may extend, for example, parallel to the axis A. In some embodiments, the surface represents the radial boundary of the magnetic pole piece 158. The magnetic pole piece 158 may be composed of a single magnetic pole element (as shown in FIGS. 1-2), but in some embodiments, the magnetic pole piece 158 comprises two or more elements.

[0042] The yoke assembly 160 provides a part of the magnetic circuit of the magnetic circuit assembly 150. In some designs, the yoke assembly 160 includes two separate elements such as a separate back plate 156 and a magnetic pole piece 158. For example, as shown in FIG. 10, the yoke 360 may include a first magnetic yoke 358 and a second magnetic yoke 359 that are different from each other. In some embodiments, the first magnetic yoke 358 and the second magnetic yoke 359 may be fused to each other or may be an integral element. As in FIG. 1, the back plate 156 and the magnetic pole piece 158 may be an example of a single yoke assembly 160. However, the yoke assembly 160 may be composed of a single piece in which the back plate 156 and the magnetic pole piece 158 form a continuous piece (as shown in FIGS. 1-2). The yoke assembly 160 may include a surface perpendicular to the axis A.

[0043] The magnetic circuit assembly 150 may be configured to generate a magnetic circuit that passes through the front plate assembly 154 and across the gap 204 through the yoke assembly 160. The magnetic circuit assembly 150 may be configured to pass about 80-99% of the magnetic flux within the magnetic circuit across the gap 204. This may particularly apply to the core magnet configuration. In some embodiments (e.g., ring magnet form), the magnetic flux across the gap 204 may be 50-80% of the total magnetic flux. In some embodiments, the magnetic flux may be about 70% of the total magnetic flux. One or more elements of the magnetic circuit assembly 150 may be within the gap 204. For example, the bobbin 102 and / or the coil 104 may be disposed within the gap 204. When the magnetic flux interacts with the coil 104, the coil 104 may vibrate and produce sound from, for example, the loudspeaker 100.

[0044] As shown, in some embodiments (e.g., in the ring magnet form), the winding of coil 104 is disposed on the side of bobbin 102 opposite to pole piece 158. However, in other embodiments (e.g., in the core magnet form), the winding of coil 104 may be on the side of bobbin 102 opposite to magnet 152, or on both sides of the bobbin. The height 208 of coil 104 may be defined along axis A (e.g., as shown in FIG. 5). In some embodiments, the height 208 of coil 104 may be approximately equal to the height of the front plate assembly 154 and / or the T-shaped portion (if available) of the yoke assembly 160. In some designs, the height 208 of coil 104 is smaller or larger than the height of the front plate assembly 154. For example, the height 208 of coil 104 may be approximately half of the height of the front plate assembly 154. In some embodiments, the height 208 may be from about 0.1 mm to 150 mm. For example, in some embodiments, the height 208 may be from about 10 mm to 30 mm. This range can provide a sufficiently small form factor while still achieving a fairly large volume. In some examples, the height 208 of coil 104 is about 12 mm. This may be about half of the height of the voice coil in other models of speakers that can produce the same volume output. For larger speakers, a larger height 208 is possible. The height 208 of coil 104 may be referred to as the "winding width" or WW. The width of coil 104 (e.g., in the radial direction) may be from about 55% to 90% of the width of gap 204. In some embodiments, the width of coil 104 is about 71% or about 75% of the width of gap 204. It may be advantageous to reduce the width of gap 204. For example, by reducing the width of gap 204, the performance of loudspeaker 100 can be improved, for example, by improving the sound integrity with respect to the electrical input. The gap 204 may have a width from about 1 mm to 12 mm. In some embodiments, the gap 204 has a width of about 3.5 mm. In some embodiments, the width is about 2 mm.In some embodiments, other combinations of gap height and winding width may be necessary to produce a particular range of linear displacement of the speaker within a particular tolerance in the BL product variation due to coil stroke. The BL product is the power factor of the speaker and approximately corresponds to the product of the length of the conductor (L) placed in the magnetic field and the magnetic field strength (B) surrounding the conductor, and also approximately corresponds to the driving force generated by the conductor when a constant current passes through the conductor.

[0045] Magnetic circuit assemblies, such as those found in loudspeakers, may take various forms. For example, embodiments of the magnetic circuit assembly may generally include one or more of the features described above. In certain situations, it may be advantageous to increase the amount of magnetic flux crossing the gap (e.g., gap 204) by reducing the magnetic resistance in other regions of the magnetic circuit. This may be accomplished in several ways. One way may include, for example, reducing or eliminating gaps (e.g., adhesive gaps or other interface layers) between separate components of the magnetic circuit, including gaps between components of the magnet 152, between components of the front plate assembly 154, between components of the back plate 156, between components of the pole pieces 158, and / or between any of the aforementioned components. For example, it may be advantageous to provide separate first and second plates in the front plate assembly 154, each of which is directly fixed (e.g., by an adhesive) to the magnet 152. In some embodiments, the separate first and second front plates are forged and adhered to the magnet without machining, thus eliminating the gap between the front plate components, reducing magnetic losses, and saving substantial manufacturing costs.

[0046] FIG. 6 shows a schematic cross-sectional view of an exemplary magnetic circuit assembly 350. The magnetic circuit assembly 350 may include a first magnet 152, a front plate assembly 154 including a first plate 302, a second plate 304, a second magnet 306, and an upper end cap 308, and a yoke 360. The magnetic circuit assembly 350 may include other elements not shown and / or described elsewhere in this specification. The yoke 360 may be coupled to the first magnet 152 along a proximal surface of the magnet 152. The second plate 304 may be coupled to the first magnet 152 along a distal surface of the first magnet 152 and a proximal surface of the second plate 304. The first plate 302 may be coupled to the second plate 302 along a distal surface of the second plate 304 and a proximal surface of the first plate 304. The second magnet 306 may be coupled to the first plate 302 along a distal surface of the first plate 302 and a proximal surface of the second magnet 306. The upper end cap 308 may be coupled to the second magnet 306 along a distal surface of the second magnet 306 and a proximal surface of the upper end cap 308. The first plate 302 and / or the second plate 304 may be separately manufactured (e.g., forged) and attached as shown. The first plate 302 and the second plate 304 may be manufactured as interchangeable parts. The first plate 302 and the second plate 304 may exhibit planar symmetry only in one rotational direction along a plane. For example, as shown, a 180-degree rotation of the first plate 302 about a vertical axis no longer results in planar symmetry with the second plate 304. As a further example, a 180-degree rotation of the first plate 302 about a horizontal axis may reverse the planar symmetry between the first plate 302 and the second plate 304 as shown.

[0047] As shown, in some embodiments, each of the first plate 302 and the second plate 304 can have a respective first radial portion with an axial dimension smaller than that of the respective second radial portion. As shown, the second plate 304 has a first radial portion 304a and a second radial portion 304b. The first plate 302 can have a similar radial portion (not labeled). In some embodiments, the first radial portion 304a can be a radially inner portion with respect to the second radial portion 304b (e.g., in FIG. 2). Alternatively, the first radial portion 304a can be a radially outer portion with respect to the second radial portion 304b (e.g., in FIG. 4). The distance between the first plate 302 and the magnet 152 can be less than 0.5 mm. In some embodiments, the distance is about 0.1 mm and can be a location where an adhesive is applied. The first plate 302 can be fixed to the magnet 152 (e.g., adjacent to the first region) along the proximal surface of the first plate 302. The first plate 302 can be fixed to the magnet 152 using attachment means known in the art (e.g., adhesion, bonding, etc.). In some designs, the side surface 302c of the first plate 302 is radially aligned with the side surface 304c of the second plate 304 (e.g., equidistant from the central axis A). In some embodiments, the cross-section of the first plate 302 forms an L-shape (e.g., an inverted L). Additionally or alternatively, the cross-section of the second plate 304 can form an L-shape. The first plate 302 and / or the second plate 304 can exhibit asymmetry across a horizontal axis. Additionally or alternatively, the first plate 302 and / or the second plate 304 can exhibit asymmetry along a vertical axis. The first plate 302 can include a material with a high magnetic permeability such as steel (e.g., low-carbon steel) and / or iron. Other materials with a higher magnetic permeability, such as composite materials, are possible.

[0048] The height of the side surface of the first plate 302 (e.g., defined axially) may be at least partially determined by the material used for the first plate 302. For example, it may be advantageous to avoid magnetic saturation of the material within the first plate 302. However, a specific minimum saturation level may be preferred. For example, in some embodiments, one or more components of the magnetic circuit (e.g., coil 104, front plate assembly 154, etc.) can have a saturation level of about 85% to 99% of the saturation point of the material of the one or more components. As an example, a particular type of steel (e.g., low-carbon steel) may have a magnetic saturation point of about 2T. In this example, a saturation level above about 90% (e.g., 1.8T) and / or from about 92.5% (e.g., 1.7T) to 97.5% (e.g., 1.95T) may be preferred. Saturation levels within these ranges help reduce the effects of the current passing through the coil and / or the movement of the coil 104 while in a fixed magnetic field, and thus reduce magnetic flux modulation. This can also reduce the resulting distortion. Further, this reduces the effect of the material (e.g., steel) on the inductance of the coil and can further reduce distortion.

[0049] The second plate 304 of the front plate assembly 154 may be disposed adjacent to the distal surface of the magnet 152. The distance between the second plate 304 and the magnet 152 may be less than 0.5 mm. In some embodiments, the first radial portion 304a and the second radial portion 304b may not overlap.

[0050] In some embodiments, a space axially separates the first plate 302 from the second plate 304 (e.g., the plates are not in contact). The second plate 304 may be fixed to the magnet 152 using attachment means known in the art (e.g., adhesion, bonding, etc.). The short-circuit ring 320 may be disposed within the space axially separating the first plate 302 from the second plate 304. Additionally or alternatively, the first plate 302 and the second plate 304 may be disposed adjacent to each other along respective portions (e.g., radial portions) of each plate. Thereby, the short-circuit ring can be disposed in a more advantageous position within the assembly relative to the rest position of the voice coil winding.

[0051] As shown in FIG. 6, in some embodiments, at least a portion of each of the first plate 302 and the second plate 304 may be disposed between the magnet 152 and the second magnet 306. In some designs, the first plate 302 is disposed between the magnet 152 and the second plate 304 along an axis parallel to axis A. The first plate 302 and the second plate 304 may be substantially composed of a ferromagnetic metal such as iron or steel. The height of the side surface 304c (e.g., defined axially) may be determined at least in part by the material used for the second plate 304. For example, it may be advantageous to avoid magnetic saturation of the material within the second plate 304. However, as described herein, a particular level of magnetic saturation may be preferred in some cases.

[0052] Yoke 360 may have the common features of the yoke assembly 160 described with respect to FIGS. 1-2 above. Yoke 360 may form a U-shape. For example, a first leg of yoke 360 forming a first portion of the "U-shape" may be fixed to the base end face of magnet 152. A second leg of yoke 360 forming a second portion of the "U-shape" may extend a greater axial distance than the first leg. As shown in FIG. 6, a first portion 330 of the second leg of yoke 360 may be disposed opposite magnet 152. A second portion 332 of the second leg of yoke 360 may be disposed opposite side face 304c of the second plate 304 to form a first gap 312. A third portion 334 of the second leg of yoke 360 may be opposite side face 302c of the first plate 302 to form a second gap 314. The second leg of yoke 360 may be tapered axially as shown in FIG. 6. For example, the third portion 334 of yoke 360 may be narrower than the first portion 330 of yoke 360. The extending surface 340 of yoke 360 may be a plane and / or parallel to axis A. The height of the most distal portion of the third portion 334 of yoke 360 may be proximal (e.g., below) the most distal surface of the upper end cap 308 and / or the most distal surface of the second magnet 306. As described above, this arrangement can enhance the magnetic flux passing through air and / or one or more portions of the frame (e.g., the speaker frame).

[0053] The magnetic circuit assembly 350 may include a coil 104 (not shown). The coil 104 may be wound around a bobbin 102. Other features of the coil 104 and / or the bobbin 102 of the magnetic circuit assembly 350 may be as described above with respect to FIGS. 1-2. The coil 104 may have a height 208 that extends within the first gap 312 and / or the second gap 314. The coil 104 may be configured to be modulated within the first gap 312 and / or the second gap 314 during use, depending on the need for a magnetic circuit (e.g., to produce a modified sound). In some designs, the coil 104 extends from the height of the distal surface of the first plate 302 to the height of the proximal surface of the second plate 304. However, the coil 104 may be shorter (e.g., have a smaller height 208) than this.

[0054] As described below, the tapered radial portions of the first plate 302 and the second plate 304 can enhance the magnetic flux across the corresponding first gap 312 and second gap 314. Thereby, the strength of the magnetic circuit can be increased. This makes it possible to reach performance thresholds that were previously unattainable with similar form factors. For example, the magnetic circuit assembly 150, when included in a speaker assembly such as those described herein, may allow for an increase in volume.

[0055] As described above, some embodiments of the magnetic circuit assembly 350 may include a short - circuit ring 320. The short - circuit ring 320 may be referred to as a Faraday loop or a short - circuited turn. The short - circuit ring 320 may include a metal (e.g., copper, aluminum) or other conductive material. The short - circuit ring 320 may be configured to be a magnetic flux insulator such that the short - circuit ring 320 does not conduct magnetic flux well. For example, it may be advantageous to include one or more short - circuit rings (e.g., short - circuit ring 320) to improve the function of the magnetic circuit assembly 350 by reducing the increase in impedance as the frequency increases. The short - circuit ring may also reduce the effect of the current flowing through the voice coil moving across the gap of the permanent magnetic field (e.g., gap 204). Additionally or alternatively, the short - circuit ring 320 may reduce the effective inductance of the coil 104 (not shown) over one or more ranges of frequencies (e.g., higher frequencies). The effective frequency range can be affected by how much the short - circuit ring reduces the inductance. For example, without being limited to theory, the larger the inductance reduction, the smaller the frequency range in which the short - circuit ring is effective. In some designs, the short - circuit ring (e.g., short - circuit ring 320) is adjacent to the yoke 360. However, one or more short - circuit rings can be arranged in a number of configurations. For example, the short - circuit ring 320 may be arranged between the first plate 302 and the magnet 152, between the first plate 302 and the second plate 304 (as shown), and / or adjacent to or near a part of the yoke 360. For example, the short - circuit ring 320 may be arranged adjacent to or near the yoke 360 opposite the second plate 304, opposite the first plate 302, opposite the magnet 152, and / or in a groove of the yoke 360. In a particular configuration (e.g., core - magnet form), the short - circuit ring is arranged radially inside the coil 104.In some embodiments, the short - circuit ring can be replaced with an electrically - short - circuited loop of conductive wire that occupies the same space, or a loop of conductive wire that is placed inside or outside the motor assembly and is connected to a selected or variable electrical resistance that is placed in series electrically with the wire loop, thereby providing an adjusted or variable effect of the short - circuit structure.

[0056] FIG. 7 shows another exemplary magnetic - circuit assembly 350 along with modeled magnetic flux lines. As shown, magnet 152 can be oriented to produce magnetic flux lines that exit magnet 152 parallel to central axis A. The arrangement and shape of the first plate 302, the second plate 304, and the yoke 360 can result in compact magnetic flux lines across first gap 312 and second gap 314 (not shown here). In these gaps, coil 104 can be configured to translate. Such compact magnetic flux lines can prevent substantial leakage of the magnetic field from the magnetic - circuit assembly. A design using multiple plates within the front - plate assembly as shown in FIG. 7 can promote a more uniform magnetic - field strength across the region where coil 104 is placed than other designs. FIG. 7 shows a short - circuit ring 320 disposed between the first plate 302 and the second plate 304. The short - circuit ring 320 may be adjacent to one or both of the first plate 302 and / or the second plate 304. For example, the short - circuit ring 320 may be attached to one or both of them, or may be mechanically captured between both. Providing separate plates 302, 304 can better enable the placement of the short - circuit ring 320 between the plates, and thus provide a further advantage of the design described herein.

[0057] FIG. 8 shows a graph of values regarding the product of magnetic field strength (B, unit: T) along the distance (L, unit: m) over the exemplary voice coil of various magnetic circuits described with respect to FIG. 7 (BL product, unit: Tm) (in units of mm). The voice coil may be, for example, coil 104. In general, it may be advantageous to approximate a constant (or “flat”) BL value over a longer length of the voice coil position with respect to the stationary position of the voice coil. As shown, the BL value is flat, for example, from -5.0 mm to 10.0 mm. This can result in an improved sound quality compared to a loudspeaker having a greater gradient within the domain of -5.0 mm to 10.0 mm, and enhance the linearity of the response of coil 104 to an input signal. For example, this can reduce harmonic distortion. FIG. 8 also shows the values of magnetic field strength (B, unit: T) along the exemplary voice coil of various magnetic circuits described with respect to FIG. 7 (in units of mm). In general, it may be advantageous to approximate B values symmetric with respect to the center of the voice coil. As shown, the B values of the design shown in FIG. 7 are fairly symmetric over the distances shown. This can improve the predictability and consistency of the sound produced from a given input.

[0058] FIG. 9 shows a schematic cross-sectional view of another exemplary embodiment of the ring magnet form of a loudspeaker according to some embodiments. As shown in FIG. 9, the magnetic circuit assembly may include a first plate 302 and a second plate 304 below (e.g., proximal to) the ferromagnetic metal frame of the loudspeaker. As shown, the first magnet 152 can be disposed along the surface of the yoke 360, and the second plate 304 can be disposed along the surface of the first magnet 152. The first plate 302 and the second plate 304 may be arranged such that the most distal surface of the yoke 360 is distal to the most distal surface of the first plate 302 to provide a symmetric magnetic field distribution between the two magnetic gaps. The distal surface of the most distal plate interfaces with the proximal surface of the ferromagnetic frame of the speaker and forms part of the magnetic circuit. The second magnet 306 interfaces with the ferromagnetic frame of the loudspeaker on its proximal side and with air on its distal side, forming an air return path for the second magnet 306. Thus, in some embodiments, the ferromagnetic member of the frame can be "sandwiched" between the second magnet 306 and the first plate 302. In some embodiments, the upper end cap 308 is included along the distal surface of the second magnet 306. However, in certain embodiments, the upper end cap may not be present.

[0059] FIG. 10 shows a schematic cross-sectional view of an exemplary embodiment of a ring magnet form of a loudspeaker according to some embodiments. The embodiment shown in FIG. 10 can include many of the features included in FIG. 9. FIG. 10 includes a second magnet 306 that is proximal (e.g., below) a portion of the yoke 360 and above different portions of the yoke 360. As shown, the second magnet 306 is disposed between the pole piece of the first magnetic yoke 358 and the inner surface of the second magnetic yoke 359. The first magnetic yoke 358 may be U-shaped. The second magnetic yoke 359 may function as a magnetic path around one or more of the other elements in the magnetic circuit assembly. For example, the second yoke 359 may be coupled to the first plate 302 and / or the second magnet 306 as shown. The second magnetic yoke 359 can function as a shield for capturing lost magnetic flux, thus improving magnetic efficiency. This shielding effect can reduce the interaction between the magnetic field and certain types of sensitive devices. The first magnet 152 can help supply additional magnetic flux to the front plate assembly in the reinforcing direction, increasing the available magnetic flux in the magnetic circuit. The second magnet 306 may include one or more features of the second magnet 306 described above in other embodiments.

[0060] Exemplary embodiment Item 1. A magnetic circuit included in a loudspeaker, comprising: a first plate having a distal surface and a proximal surface; a second plate having a distal surface and a proximal surface opposite to the distal surface, wherein the distal surface of the second plate is disposed along the proximal surface of the first plate, and at least one of the first or second plates has a first radial portion with an axial dimension smaller than a second radial portion; a magnet having a distal surface and a proximal surface, wherein the distal surface of the magnet is disposed along the proximal surface of the second plate; and a yoke disposed along the proximal surface of the magnet, the yoke being shaped to form first and second magnetic circuit gaps in the radial direction between the yoke and each of the first and second plates.

[0061] Item 2. The magnetic circuit of Item 1, wherein the yoke is U-shaped.

[0062] Item 3. The first and second magnetic circuit gaps are dimensioned to receive a voice coil therein, the magnetic circuit of Item 1.

[0063] Item 4. The first radial portion forms an axial gap with the other of the first plate or the second plate, the magnetic circuit of Item 3.

[0064] Item 5. The axial gap is configured to receive a short-circuit ring therein, the magnetic circuit of Item 4.

[0065] Item 6. The magnet forms a ring magnet, the magnetic circuit of Item 1.

[0066] Item 7. The magnet is configured to generate a higher magnetic flux than ferrite, the magnetic circuit of Item 1.

[0067] Item 8. The magnet includes neodymium, the magnetic circuit of Item 1.

[0068] Item 9. The magnetic circuit of Item 1 further includes a second magnet having a proximal surface disposed along the distal surface of the first plate.

[0069] Item 10. The magnetic circuit of Item 9 further includes a second magnet having a distal surface disposed distally beyond the distal surface of the yoke.

[0070] Item 11. The magnetic circuit of Item 1 further includes a frame coupled to the distal end of the yoke, and the second magnet is disposed with respect to the yoke such that magnetic flux from the magnet substantially passes through the frame.

[0071] Item 12. Each of the first and second plates has a respective first radial portion with an axial dimension smaller than that of its respective second radial portion, the magnetic circuit of Item 1.

[0072] Item 13. The first radial portion is closer to the first magnetic circuit gap than the second radial portion, the magnetic circuit of Item 1.

[0073] Item 14. A first magnet having a distal surface and a proximal surface, a first plate having a distal surface and a proximal surface, wherein the distal surface of the first plate is arranged along the proximal surface of the first magnet, a first plate, a second plate having a distal surface and a proximal surface, wherein the distal surface of the second plate is arranged along the proximal surface of the first plate, a second plate, a second magnet having a distal surface and a proximal surface, wherein the distal surface of the second magnet is arranged along the proximal surface of the second plate, a second magnet, and a yoke arranged along the proximal surface of the second magnet, the yoke being shaped to form first and second magnetic circuit gaps in the radial direction between the yoke and each of the first and second plates, a magnetic circuit in which the distal surface of the first magnet is arranged on the distal side beyond the most distal surface of the yoke, a voice coil configured to be arranged at least between the first and second magnetic circuit gaps, a diaphragm engaged with the voice coil, and a frame configured to support the diaphragm and be operably coupled to the yoke. A speaker comprising.

[0074] Item 15. The speaker according to Item 14, wherein the outer radial portion of the first plate has an axial dimension smaller than that of the inner radial portion of the first plate, and the outer radial portion of the second plate has an axial dimension smaller than that of the inner radial portion of the second plate.

[0075] Item 16. The speaker according to Item 15, wherein the inner radial portions of the first and second plates form an axial gap.

[0076] Item 17. The speaker according to Item 16, wherein the axial gap is configured to receive a short-circuit ring therein.

[0077] Item 18. The speaker according to Item 14, wherein the first magnet is arranged relative to the yoke such that the frame is configured to conduct magnetic flux from the first magnet.

[0078] Item 19. A first plate and a second plate each disposed between a first magnet and a second magnet, wherein at least one of the first or second plates exhibits asymmetry across a horizontal axis, the first plate and the second plate; a yoke disposed along the second magnet, the yoke being shaped to form first and second magnetic circuit gaps in the radial direction between the yoke and each of the first and second plates; a magnetic circuit comprising the yoke; a voice coil configured to be disposed at least between the first and second magnetic circuit gaps; a diaphragm engaged with the voice coil; and a frame configured to support the diaphragm, the first magnet being disposed relative to the yoke such that the frame is configured to conduct magnetic flux from the first magnet. A speaker.

[0079] Item 20. The speaker according to Item 19, wherein an outer radial portion of the first plate has an axial dimension smaller than an inner radial portion of the first plate, and an outer radial portion of the second plate has an axial dimension smaller than an inner radial portion of the second plate.

[0080] Item 21. The speaker according to Item 20, wherein the inner radial portions of the first and second plates form an axial gap.

[0081] Item 22. The speaker according to Item 21, wherein the axial gap is configured to receive a short-circuit ring therein.

[0082] Item 23. The speaker according to Item 21, wherein at least one of the first or second magnets contains neodymium.

[0083] Conclusion Throughout this specification, references to "some embodiments" or "embodiments" mean that the particular features, structures, or characteristics described in connection with the embodiments are included in at least some embodiments. Thus, appearances of the phrases "in some embodiments" or "in embodiments" in various places throughout this specification are not necessarily all referring to the same embodiments, but may refer to one or more of the same or different embodiments. Further, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments, as would be apparent to one of ordinary skill in the art from the disclosure.

[0084] As used in this application, the terms "comprising", "including", "having", and the like are synonyms and are used in an inclusive, open-ended fashion and do not exclude additional elements, features, acts, operations, etc. Also, the term "or" is used in an inclusive sense (and not an exclusive sense), so that for example, when used to connect a list of elements, the term "or" means one, some, or all of the elements in the list.

[0085] Similarly, in the above description of embodiments, it should be understood that various features may be grouped together in a single embodiment, figure, or description for the purpose of simplifying the disclosure and aiding in the understanding of one or more aspects of the invention. However, the disclosed method should not be construed as reflecting an intention that any claim requires more features than are explicitly recited in that claim. Rather, aspects of the invention lie in combinations of fewer features than all the features of any single foregoing disclosed embodiment. Thus, there is no feature or group of features that is necessary or essential to each embodiment.

[0086] Numerous applications, publications, and external documents may be incorporated herein by reference. Any inconsistencies or conflicts between the description in the body of this specification and the description in any incorporated document should be resolved in favor of the description in the body of the specification.

[0087] Although described in the exemplary context of specific preferred embodiments and examples, it will be understood by those skilled in the art that the present disclosure extends beyond the specifically described embodiments to other alternative embodiments and / or uses and obvious modifications and equivalents. Accordingly, it is intended that the appended claims not be limited by the foregoing specific embodiments.

Description of Reference Numerals

[0088] 100 Loudspeaker 102 Bobbin 104 Coil 106 Frame 108 Elastic Connector 110 Diaphragm 112 Damper 114 Cap 150 Magnetic Circuit Assembly 152 Magnet 154 Front Plate Assembly 156 Back Plate 158 Pole Piece 160 Yoke Assembly 204 Gap 208 Height 302 First Plate 302c Side 304 Second Plate 304a First Radial Portion 304b Second Radial Portion 304c Side 306 Second Magnet 308 Upper End Cap 312 First Gap 314 Second Gap 320 Short - Circuit Ring 330 First Portion 332 Second Portion 334 Third Portion 340 Extending Surface 350 Magnetic Circuit Assembly 356 Vent Hole 358 First Magnetic Yoke 359 Second magnetic yoke 360 Yoke A Central axis

Claims

1. A magnetic circuit included in a loudspeaker, comprising: a first plate having a distal surface and a proximal surface; a second plate having a distal surface and a proximal surface opposite to the distal surface, wherein the distal surface of the second plate is arranged along the proximal surface of the first plate, and at least one of the first or second plates has a first radial portion with an axial dimension smaller than a second radial portion; a magnet having a distal surface and a proximal surface, wherein the distal surface of the magnet is arranged along the proximal surface of the second plate; a second magnet configured to increase the magnetic flux in the magnetic circuit; a yoke arranged along the proximal surface of the magnet, and shaped to form first and second magnetic circuit gaps in the radial direction between the yoke and each of the first and second plates; A magnetic circuit comprising the above components.

2. The magnetic circuit according to claim 1, wherein the yoke is U-shaped.

3. The magnetic circuit according to claim 1, wherein the first and second magnetic circuit gaps are dimensioned to receive a voice coil therein.

4. The magnetic circuit according to claim 3, wherein the first radial portion forms an axial gap with the other of the first plate or the second plate.

5. The magnetic circuit according to claim 4, wherein the axial gap is configured to receive a short-circuit ring therein.

6. The magnetic circuit according to claim 1, wherein the magnet forms a ring magnet.

7. The magnetic circuit according to claim 1, wherein the magnet is configured to generate a magnetic flux higher than that of ferrite.

8. The magnetic circuit according to claim 1, wherein the magnet contains neodymium.

9. The magnetic circuit according to claim 1, wherein the second magnet has a proximal surface arranged along the distal surface of the first plate.

10. The magnetic circuit according to claim 9, wherein the second magnet has a distal surface arranged distally beyond the most distal surface of the yoke.

11. The magnetic circuit according to claim 1, further comprising a frame coupled to the distal end of the yoke, and the second magnet is arranged relative to the yoke such that the magnetic flux from the magnet substantially passes through the frame.

12. The magnetic circuit according to claim 1, wherein each of the first and second plates has a respective first radial portion having an axial dimension smaller than that of the respective second radial portion.

13. The magnetic circuit according to claim 1, wherein the first radial portion is closer to the first magnetic circuit gap than the second radial portion.

14. A first magnet having a distal surface and a proximal surface, A first plate having a distal surface and a proximal surface, wherein the distal surface of the first plate is disposed along the proximal surface of the first magnet, A second plate having a distal surface and a proximal surface, wherein the distal surface of the second plate is disposed along the proximal surface of the first plate, A second magnet having a distal surface and a proximal surface, wherein the distal surface of the second magnet is disposed along the proximal surface of the second plate, A yoke disposed along the proximal surface of the second magnet and shaped to form first and second magnetic circuit gaps in the radial direction between the yoke and each of the first and second plates, A magnetic circuit in which the distal surface of the first magnet is disposed distally beyond the most distal surface of the yoke, A voice coil configured to be disposed at least between the first and second magnetic circuit gaps, A diaphragm engaged with the voice coil, A frame configured to support the diaphragm and be operably coupled to the yoke A speaker comprising.

15. The speaker according to claim 14, wherein an outer radial portion of the first plate has an axial dimension smaller than that of an inner radial portion of the first plate, and an outer radial portion of the second plate has an axial dimension smaller than that of an inner radial portion of the second plate.

16. The speaker according to claim 15, wherein the inner radial portions of the first and second plates form an axial gap.

17. The speaker according to claim 16, wherein the axial gap is configured to receive a short-circuit ring therein.

18. The speaker according to claim 14, wherein the first magnet is disposed relative to the yoke such that the frame is configured to conduct magnetic flux from the first magnet.

19. A first plate and a second plate each disposed between a first magnet and a second magnet, wherein at least one of the first or second plates exhibits asymmetry across a horizontal axis, the first plate and the second plate; A yoke disposed along the second magnet and shaped to form first and second magnetic circuit gaps in the radial direction between the yoke and each of the first and second plates, a magnetic circuit comprising the yoke; A voice coil configured to be disposed at least between the first and second magnetic circuit gaps; A diaphragm engaged with the voice coil; A frame configured to support the diaphragm, wherein the first magnet is disposed relative to the yoke such that the frame is configured to conduct magnetic flux from the first magnet; A speaker.

20. The speaker according to claim 19, wherein an outer radial portion of the first plate has an axial dimension smaller than an inner radial portion of the first plate, and an outer radial portion of the second plate has an axial dimension smaller than an inner radial portion of the second plate.

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