Magnetic circuit and loudspeaker

Abstract

The invention provides a magnetic circuit and a loudspeaker. The magnetic circuit may include first and second plates, 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 opposite 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 plate or the second plate may have a first radial portion and a second radial portion, the first radial portion having a smaller axial dimension than the 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 radially form a first magnetic path gap and a second magnetic path gap between the yoke and the first plate and the second plate, respectively.

Description

Technical Field

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

[0002] Loudspeakers provide listeners with high-quality sound that can be heard from a distance and through various media. Over the years, various loudspeaker configurations have been developed. Current loudspeakers have certain functionality in developing magnetic circuits and converting electrical energy into sound waves. Various magnetic circuit components have been developed to direct magnetic fields in various electrical devices including loudspeakers. However, there are still some missing functions and many problems in this field, and the present application provides solutions for these. Summary of the Invention

[0003] The exemplary embodiments described herein have multiple innovative features, none of which is indispensable or solely determines its desired characteristics. Without limiting the scope of the claims, some of the advantageous features will now be summarized.

[0004] In some embodiments, a magnetic circuit component can be used in a loudspeaker. The magnetic circuit can include a first plate and a second plate, a magnet, and a yoke. The first plate can have a distal surface and a proximal surface. The second plate can have a distal surface and a proximal surface opposite to the distal surface. The distal surface of the second plate can be disposed along the proximal surface of the first plate. At least one of the first plate or the second plate can have a first radial portion and a second radial portion, and the first radial portion has a smaller radial dimension than the second radial portion. The magnet can 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 can radially form a first magnetic circuit gap and a second magnetic circuit gap between the yoke and the first plate and the second plate, respectively. Brief Description of the Drawings

[0005] The following drawings and related descriptions are used to illustrate embodiments of the present disclosure and do not limit the scope of the claims.

[0006] Figure 1 A cross-section of the design of an exemplary loudspeaker 100 is schematically shown.

[0007] Figure 2 A cross-sectional schematic view of an exemplary embodiment of an annular magnet design of a loudspeaker according to some embodiments is shown.

[0008] Figure 3 A cross-section of an exemplary loudspeaker with a core magnet design according to some embodiments is schematically shown.

[0009] Figure 4A cross-sectional schematic view of an exemplary embodiment of the core magnet design of a speaker according to some embodiments is shown.

[0010] Figure 5 A cross-sectional schematic view of a magnetic circuit assembly that can be used for a speaker according to some embodiments is shown.

[0011] Figure 6 A cross-sectional schematic view of an exemplary magnetic circuit assembly according to some embodiments is shown.

[0012] Figure 7 A cross-sectional schematic view of another exemplary magnetic circuit assembly and simulated magnetic field lines according to some embodiments is shown.

[0013] Figure 8 The values of magnetic flux (B) and the product BL at a distance from the geometric center of the voice coil for two designs are shown.

[0014] Figure 9 A cross-sectional schematic view of another exemplary embodiment of the ring magnet design of a speaker according to some embodiments is shown.

[0015] Figure 10 A cross-sectional schematic view of an exemplary embodiment of the ring magnet design of a speaker according to some embodiments is shown.

[0016] The foregoing features and other features will now be described with reference to the drawings outlined above. The drawings and the related description are intended to illustrate embodiments and not to limit the scope of any claims. In all the drawings, reference numerals may be reused to indicate the correspondence of the elements being referred to. Additionally, in applicable cases, the first one or two digits of the reference numeral of an element can generally indicate the figure number where the element first appears. Detailed Description

[0017] Although certain embodiments and examples are discussed below, the innovative subject matter is not limited to these specifically disclosed embodiments, but also relates to other alternative embodiments and / or uses and their modifications and equivalents. Accordingly, the scope of the appended claims is not limited by any particular embodiment described below. For example, in any method or process disclosed herein, the acts or operations of the method or process may be performed in any suitable order, and not necessarily limited to any particular disclosed order. Various operations may be described as multiple discrete operations that are performed in turn to aid in understanding certain embodiments; however, the described order should not be construed as indicating that these operations are order-dependent. Additionally, the structures, systems, and / or devices described herein may be embodied as integrated components or separate components. To compare various embodiments, specific aspects and advantages of the embodiments are also described herein. However, not every embodiment necessarily achieves all of these aspects or advantages. Thus, for example, each embodiment may achieve or optimize one or a group of advantages in the manner taught herein, without necessarily achieving other aspects or advantages taught or suggested herein.

[0018] Existing magnetic circuits are sufficient for certain uses. However, there is still a need to improve the magnetic performance achievable with prior designs, even prior double-gap designs. Design goals for magnetic circuits may include reducing distortion and improving control of transducer movement over a large range of voice coil positions. The exemplary designs described herein can improve magnetic circuit performance, for example, by combining multi-gap (e.g., double-gap) technology with multi-magnet (e.g., double-magnet) topologies. Compared to previously known multi-gap designs, the designs described herein can create extremely strong magnetic gaps, thus providing an efficient transducer design. Certain designs can reduce the depth of the motor by employing a specific double-gap design. For example, to achieve the same linear force applied to the voice coil to meet the required maximum displacement (“Xmax”), a standard single-gap design may need to increase its depth by nearly 25 mm to have similar performance. Certain designs described herein can also help reduce the inductance of the voice coil compared to designs using standard single-gap motors. For example, an optimized double-gap design can reduce the tooling required to create the components, since certain components (as described below) can be used multiple times (e.g., twice) within a single component by flipping them 180 degrees.

[0019] A reduced motor depth can achieve a BL gap width that meets the target Xmax while reducing the height of the voice coil (commonly referred to as "winding width" (WW)). This can achieve strong low-frequency (LF) performance and low total harmonic distortion (THD). Additionally or alternatively, this can also reduce the internal inductance of the coil, thereby reducing distortion and improving high-frequency (HF) extension. Some of the loudspeaker embodiments described herein may have an output of up to 117 dB in a wide operating frequency range, such as 70 to 5,000 Hz, with a relatively small form factor. Therefore, the motor topologies described herein can achieve a large motor force with a small form factor, providing a high acoustic output. Additionally or alternatively, the topology can reduce the WW, thereby reducing the mass and inductance, which are the main obstacles to achieving high transducer efficiency.

[0020] Additionally or alternatively, the topologies described herein can provide improved low-frequency performance. The topology can achieve a large Xmax with a small form factor. The saved depth can provide a moving gap for the displacement of the transducer, enabling it to generate the target low-frequency sound output level. Additionally or alternatively, the designs herein have improved heat dissipation performance due to having a clear heat transfer path leading from the motor assembly.

[0021] Systems for loudspeakers and magnetic circuit assemblies are described herein. It should be understood that although the descriptions herein are based on the context of loudspeakers and magnetic circuits, 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 methodologies and related systems disclosed herein can be used with various loudspeaker designs.

[0022] Unless otherwise explicitly stated, the terms used herein should be understood to mean their conventional and ordinary meanings within the technical field.

[0023] Figure 1 A cross-section of a loudspeaker 100 with a ring magnet design is schematically shown. The loudspeaker 100 may include one or more components described herein. However, since not every element of the loudspeaker 100 is required in every embodiment, no single element should be considered indispensable to the loudspeaker 100. Figure 1 The illustrated loudspeaker 100 represents a circular magnet (ring-shaped or toroidal magnet) structure. However, a core magnet design (bar or built-in magnet type) and an oblong or rectangular magnet design can also be achieved with a moderately adjusted magnetic circuit design and configuration that is basically similar to that described herein. Figure 3 An example of such an embodiment is provided. Figure 1 The design of Figure 3The minor differences between the designs are clear to those of ordinary skill in the art, and thus are omitted for clarity and conciseness.

[0024] The illustrated loudspeaker 100 has a central axis A about which the loudspeaker 100 is substantially radially symmetric. Thus, Figure 1 The elements shown may appear to be repetitive, but may actually represent the same element disposed about the axis. However, in some designs, multiple elements may be used for a single function.

[0025] The loudspeaker 100 includes a frame 106. In some embodiments, the frame 106 may be referred to as a basket or a housing. At or near a first end of the frame 106, the frame may be attached to a front plate assembly 154 of a magnetic circuit assembly 150. The front plate assembly 154 may include a receiving portion (not shown) for receiving a connector of the frame 106. The frame 106 may be fixed to the front plate assembly 154 by adhesion (e.g., gluing), bonding (e.g., brazing, welding), or other means. For example, a press-fit configuration may be used in some embodiments. In some designs, one or more screws, rivets, or mechanical fasteners may be used to attach the frame 106 to the front plate assembly 154. In some embodiments, the frame 106 may be attached to a resilient connector 108 at or near a second end of the frame. In some embodiments, the frame 106 may be directly attached to the diaphragm 110.

[0026] In some embodiments, the front plate assembly 154 may include one or more plates and / or one or more magnets. For example, as Figure 2 shown, the front plate assembly 154 may include a first plate 302, a second plate 304, a second magnet 306, and / or a top cover 308. Additionally or alternatively, the front plate assembly 154 may include a shorting ring 320. The above features will be described in more detail below. Thus, in some embodiments, the frame 106 may be coupled to the second magnet 306, the top cover 308, and / or another element described herein.

[0027] The frame 106 may include a thin sheet of rigid material (e.g., steel, plastic, synthetic resin, wood). In some embodiments, the frame 106 includes a non-magnetic material (e.g., aluminum or an aluminum alloy), but ferromagnetic materials such as steel may also be used. The frame 106 may also be attached to a damper 112. The frame 106 may exhibit radial symmetry or approximate radial symmetry about the central axis A.

[0028] The elastic connecting member 108 may be referred to as a surround, an edge, or an outer suspension. The elastic connecting member 108 may be coupled to the frame 106. The elastic connecting member 108 may be attached to the frame 106 using a connecting device. For example, washers may be used in some designs. In some embodiments, the elastic connecting member 108 includes a sheet of rigid or elastic material. Since it is made of a sufficiently thin material, even if the material is rigid, the elastic connecting member 108 can support minute perturbations between the frame 106 and the diaphragm 110.

[0029] The speaker 100 may further include a damper 112. In some embodiments, the damper 112 may also be referred to as a spider or an inner suspension, but other terms may also be used. The first end of the damper 112 may be connected to the frame 106 at a position closer to the first end than the second end of the frame 106. The second end of the damper 112 may be attached to the bobbin 102. The damper 112 may support the bobbin 102 to allow the bobbin 102 to vibrate while preventing or reducing contact between the bobbin 102 or the coil 104 and components of the magnetic circuit assembly 150 (such as the front plate assembly 154, the pole piece 158). The bobbin 102 may be attached to the damper 112 in a variety of different ways (such as by bonding, adhering). In some embodiments, the damper 112 may include a resin-containing fabric. The damper 112 may include a resin plate forming a ring. As Figure 1 shown, when viewed from the side, the damper 112 may be corrugated radially. The radial corrugations may be formed concentrically with the central axis A.

[0030] The speaker 100 generally may include a diaphragm 110. Sound may be generated and / or amplified when the diaphragm vibrates. The diaphragm 110 may also be referred to as a cone (such as a woofer cone). Generally, the diaphragm 110 includes a hole at its center, thereby forming a ring shape, but a flat shape may also be used. The diaphragm 110 may include an elastic material (such as resin, fabric, plastic, paper, fiber, etc.). In multiple embodiments, the diaphragm 110 is radially symmetric about the central axis A. In such embodiments, the sound may be concentrated in the direction along the central axis A. The diaphragm 110 (such as at the inner circumference of the diaphragm 110) may be attached to the first end of the bobbin 102 or near it. The elastic connecting member 108 may be attached (such as by bonding, adhering) to the outer circumference of the diaphragm 110. Thus, the diaphragm 110 may be engaged with the coil 104.

[0031] A cover 114 may be attached near the inner periphery of the diaphragm 110. In different embodiments, the cover 114 may be referred to as a dome, dust cap, or dust cover. The cover 114 is capable of being centered about a central axis A. In some embodiments, the cover 114 may be coaxial with the pole piece 158 and / or the yoke assembly 160. The cover 114 may "enclose" the skeleton 102. As shown, in some designs, the cover 114 has a dome shape. If its geometry is formed in the diaphragm 110 or is in a flat plate shape, the cover 114 may not be necessary.

[0032] In some embodiments, the loudspeaker 100 includes a skeleton 102. In some embodiments, the skeleton 102 may be referred to as a frame or bobbin. The skeleton 102 may be formed as a ring surrounding the central axis A. In some designs, the skeleton 102 axially extends at least to the axial position of the front plate assembly 154. Thus, the skeleton 102 may be formed in a cylindrical shape. However, as Figure 1 shown, the skeleton 102 may also extend further. Other alternatives are also possible. As shown, the diaphragm 110 and / or the damper 112 may be attached (e.g., bonded, adhered) to or near the first axial end of the skeleton 102. Non-circular skeletons are also possible, and their shapes are typically oval or rectangular, depending on the configuration requirements of the loudspeaker.

[0033] The skeleton 102 may be configured to support the coil 104. In some embodiments, the coil 104 may be referred to as a voice coil. The coil 104 may be composed of a conductor that is wound around the skeleton in one or more complete turns in a closed shape. The coil 104 may be attached or otherwise fixed to the skeleton 102 in various ways (e.g., adhered, bonded). The coil 104 may be configured to accommodate an electric current passing through it. The electric current generates a magnetic field that interacts with the magnetic field generated by the magnet 152. For example, this interaction may cause the coil 104 to translate axially back and forth. This interaction can cause the coil 104 and thus the skeleton 102 to vibrate axially and / or radially along the central axis A. This vibration may be transmitted to, for example, the diaphragm 110 to generate a target sound based on an electrical input.

[0034] The coil 104 may include a series of windings of a conductive material such as metal wound around the skeleton 102. The windings may have a radial thickness extending radially from the skeleton 102. The radial thickness may be less than the gap between the front plate assembly 154 and the pole piece 158 ( Figure 1(not labeled in the figure). For example, the coil 104 can be disposed between the outer radius of the pole piece 158 and the inner radius of the front plate assembly 154. In some designs, the coil 104 has the same number of turns (e.g., number of windings) of conductive material axially along the portion where it is fixed to the bobbin 102. Having such a homogeneous distribution of windings can make the magnetic field more uniform along the height direction of the coil 104 (e.g., measured axially). The height of the coil 104 can be less than the corresponding height of a part of the front plate assembly 154 and / or the pole piece 158.

[0035] The speaker 100 generally includes a magnetic circuit assembly 150. Generally speaking, the magnetic circuit assembly 150 can include a front plate assembly 154, a magnet 152, and a yoke assembly 160. The yoke assembly 160 can include a back plate 156 and / or a pole piece 158. Similar to the other elements described with reference to Figure 1 As with the other elements described, the elements of the magnetic circuit assembly 150 are only schematically shown. For example, the front plate assembly 154 can include one or more elements. For example, as described above, the front plate assembly 154 can include a first plate 302, a second plate 304, a second magnet 306, and / or other elements. Similarly, the magnet 152, the back plate 156, and / or the pole piece 158 can include one or more elements.

[0036] In some embodiments, the front plate assembly 154 is axially adjacent to the magnet 152 and can have the same central axis as the central axis A of the magnet 152. However, other arrangements are also possible. The front plate assembly 154 can be fixed to the magnet 152. For example, the front plate assembly 154 can be attached using an adhesive (e.g., glue) or a bonding technique. The area where the front plate assembly 154 is attached to the magnet 152 can be referred to as the interface layer. Reducing the distance (e.g., any gap) between the front plate assembly 154 and the magnet 152 can be advantageous, for example, reducing the thickness of the interface layer, which can include glue or other connection materials. Various embodiments of the front plate assembly 154 will be described in more detail below.

[0037] The magnet 152 can be used to generate magnetic flux across the gap between the front plate assembly 154 and the pole piece 158. The magnet 152 can be a permanent magnet, which for example includes neodymium and / or an iron-containing material such as ferrite, or can be a temporary magnet such as an electromagnet. For example, the toroidal magnet design can include ferrite and / or the core magnet design can include neodymium. Other variations are possible, including variations using other types of magnetic materials. In some embodiments, the first magnet 152 can be configured to generate a higher magnetic flux than ferrite. For example, the first magnet 152 can include rare earth materials, such as neodymium and / or other magnetic rare earth materials. In certain embodiments, the magnetic circuit includes one or more magnets having a remanence (Br) that is about two to about eight times higher than that of a ferrite magnet. In some embodiments, the magnetic circuit includes one or more magnets having a maximum energy product (BH max) that is about two to about twenty times higher than that of ferrite. For the same size, the neodymium magnet generates a stronger magnetic field and a higher magnetic flux than the ferrite magnet. The neodymium magnet also has a higher magnetic saturation point compared to the ferrite magnet, thus generating a higher magnetic flux. The neodymium magnet is sometimes also referred to as the NdFeB magnet.

[0038] The magnet 152 can be disposed between the front plate assembly 154 and the back plate 156 of the yoke assembly 160. The magnet 152 can be oriented to generate a magnetic field axially through the first and second surfaces of the magnet, where the first surface is opposite the second surface. For example, the poles of the magnet can 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.

[0039] The yoke assembly 160 (such as the back plate 156) can be fixed (such as adhered) to the surface of the magnet 152 that is opposite the surface to which the front plate assembly 154 is fixed. The yoke assembly 160 can be attached using an adhesive (such as glue), bonding techniques, or any other suitable technique. Reducing the distance (such as the gap and / or interface layer) between the front plate assembly 154 and the magnet 152 can be advantageous, such as any distance caused by gluing or other connection methods. Multiple embodiments of the yoke assembly 160 (including the back plate 156 and / or the pole piece 158) will be described in more detail below.

[0040] Figure 2A cross-sectional schematic view of an exemplary embodiment of the ring magnet design of the loudspeaker 100 is shown. Generally numbered elements may include the numbered functions described elsewhere herein. 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 manufactured separately (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 to a position radially adjacent to the back plate 156 and / or the lower side of the back plate 156. This helps with heat dissipation of the loudspeaker 100. As Figure 2 shown, the coil 104 may be disposed between the bobbin 102 and the front plate assembly. The height (measured axially) of the coil 104 may be less than the height of the front plate assembly. This can place a greater proportion of the coil 104 within the target region of the magnetic flux. Such a region is, for example, a region having a relatively constant magnetic flux (see also below Figure 8 ).

[0041] 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, the distance may be about 0.1 mm. The distance may include the glue seam between the corresponding 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 the same, although their orientations may be different from each other. For example, the first plate 302 and the second plate 304 may be mirror-oriented with respect to each other (e.g., with respect to the horizontal plane). This creates a vertical gap between the first plate 302 and the second plate 304. In some embodiments, the vertical gap is 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 Figure 2 shown, 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., Figure 3 ), the vertical gap may be disposed between the radially outer portions of the first plate 302 and the second plate 304. As Figure 2 shown, 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 having a magnetic permeability higher than that of a metal or metal alloy).

[0042] As Figure 2As shown, at least one of the first plate 302 and / or the second plate 304 may have a first radial portion and a second radial portion, and the first radial portion has a smaller axial dimension than the second radial portion. The first radial portion (having the smaller axial dimension) may be disposed radially inward of the second radial portion with respect to the axis A, for example Figure 2 as shown. However, as Figure 3 shown, in some embodiments, the first radial portion may be disposed radially outward of the second radial portion with respect to the axis A.

[0043] As Figure 2 shown, the distal surface of the second magnet 306 may be disposed more distally than the most distal surface of the yoke 360. "Distal" herein may refer to the surface closest to the sound-emitting elements (such as the elastic connector 108, the diaphragm 110, the cover 114) of the speaker 100. The "distal" end of the speaker may be referred to as the "top" of the speaker. In contrast, the "proximal" end of the speaker generally refers to the side of the speaker where the yoke 360 is located, such as the back plate of the yoke 360. The proximal end of the speaker may correspond to the "bottom" of the speaker. Thus, the surface of the second magnet 306 may be disposed higher or above the highest surface of the yoke 360. Such an arrangement may cause magnetic flux to pass through the open space above the second magnet 306 and / or through various distal elements of the speaker 100 (such as 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 closer (e.g., below) than the most distal surface of the yoke 360. Such an 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 farther (e.g., above) than the most distal surface of the yoke 360. The term "shellpot" may be used interchangeably with "yoke" or may be regarded as a type of yoke. The shellpot may surround the magnet and may form a magnetic structure similar to an enclosure in the shape of a pot or shell, which helps to concentrate the magnetic field in the desired area. The second magnet 306 may include one or more characteristics of the above-described first magnet 152. For example, the second magnet 306 may include a rare earth material, such as neodymium and / or other magnetic rare earth materials. The second magnet 306 may have a proximal surface disposed along the distal surface of the first plate 302.

[0044] The top cover 308 can be disposed along the distal surface of the second magnet 306. The top cover 308 can better couple the second magnet 306, the first plate 302, and the second plate 304 together. For example, coupling elements (such as screws, nails, rivets, or other mechanical fasteners) can pass through these elements, and the top cover 308 can be coupled to the ends of the coupling elements to provide a rigid assembly. In some embodiments, the top cover 308 is the uppermost element of the front plate assembly (such as the front plate assembly 154). Other details related to the front plate assembly shown in Figure 6 will be introduced in connection with Figure 2 the front plate assembly shown.

[0045] The loudspeaker 100 may further include a short-circuit ring 320. The short-circuit ring 320 can be disposed between the bobbin 102 and the yoke 360. Other details regarding the short-circuit ring 320 will be introduced below. The yoke 360 can be gapless along the central axis A. Alternatively, as Figure 2 shown, the yoke 360 may include ventilation holes 356. The ventilation holes 356 can contribute to the cooling of the loudspeaker 100 and / or the magnetic circuit assembly.

[0046] As described above, a core magnet design can be used instead of a ring magnet design. Many of the components used in the core magnet design are similar or identical to the components described with reference to the ring magnet design. Figure 3 A cross-section of the loudspeaker 100 having a core magnet design is schematically shown. As shown, the coil 104 can be disposed between the pole piece 158 and the bobbin 102 and / or the front plate assembly 154. The bobbin 102 can be disposed between the coil 104 and the front plate assembly 154. As shown, the pole piece 158 can be disposed radially outside the magnet 152 and / or the front plate assembly 154. The loudspeaker 100 may include ventilation holes 356. In some embodiments, the loudspeaker 100 having a core magnet design may include a short-circuit ring (not shown). One or more short-circuit rings can 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.

[0047] Figure 4 A cross-sectional schematic view of an exemplary embodiment of the core magnet design of the loudspeaker 100 is shown. The radial orientation of the magnetic circuit assembly is the same as Figure 2The orientations of the components in the middle are substantially opposite 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 can be set 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 can be disposed in 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 (measured axially) of the coil 104 can be less than the height of the second plate 304. More details of the magnetic circuit assembly and other elements of the speaker 100 will be described below (for example, with reference to Figure 1 and 6 ). As Figure 4 shown, the speaker 100 may not include ventilation holes. Additionally or alternatively, one or more coupling elements (such as screws, nails or other mechanical fasteners) can be used to maintain the physical proximity of multiple magnetic circuit elements (such as the front - plate assembly). As shown, the top cover 308, the second magnet 306, the first plate 302, the second plate 304, the first magnet 152 and the yoke 360 are coupled together by a central screw. Other arrangements are possible.

[0048] Figure 5 Fig. shows a cross - sectional schematic view of a part of a magnetic circuit assembly 150 for a speaker, for example. In some embodiments, the pole piece 158 can be used to complete the magnetic circuit within the magnetic circuit assembly 150. In some designs, the pole piece 158 includes one or more ventilation holes (such as a hollow portion axially passing through the pole piece 158), which are not shown in Figure 1 . Such ventilation holes may be beneficial for cooling the magnetic circuit assembly 150 and / or the speaker 100. The one or more ventilation holes can be disposed axially below the coil 104 (for example, between the magnet 152 and the pole piece 158). Thus, the one or more ventilation holes can be disposed radially starting from the axis A. The speaker 100 can include multiple, for example 3, 4, 6 or 8 ventilation holes. When multiple ventilation holes are included, they can be disposed radially symmetrically. The one or more ventilation holes can be used to improve cooling, reduce mechanical resistance and / or reduce air noise. A single ventilation hole disposed around the axis A can more effectively reduce mechanical resistance, while multiple peripheral ventilation holes can more effectively cool the magnetic circuit (such as especially the coil 104). Such peripheral ventilation holes can promote air cooling on the coil.

[0049] The pole piece 158 can be shaped to adapt to the different requirements of various embodiments. In some embodiments, the pole piece 158 can be tapered at one end (such as the front end, the rear end). This can, for example, reduce the manufacturing requirements to meet the appropriate speaker size and weight requirements, or optimize the magnetic flux passing through the pole piece 158. As Figure 5As shown, some embodiments include a T-shaped pole piece 158, which can be used to optimize the target width (e.g., the radial width) of the gap 204. However, in other embodiments, the pole piece 158 is not T-shaped. In some designs, the pole piece 158 can include a surface that is generally smooth and / or flat opposite the magnet 152. The surface can be parallel to the axis A, for example. In some embodiments, the surface represents the radial boundary of the pole piece 158. The pole piece 158 can be composed of a single pole element (as shown in Figure 1 and 2 ), but in some embodiments, the pole piece 158 includes two or more elements.

[0050] 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 different back plates 156 and pole pieces 158. For example, as shown in Figure 10 , the yoke 360 can 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 can be fused together or form an integral element. As shown in Figure 1 , the back plate 156 and the pole piece 158 are an example of an integral yoke assembly 160. However, the yoke assembly 160 can be composed of a single part, where the back plate 156 and the pole piece 158 form a continuous part (such as shown in Figure 1 and Figure 2 ). The yoke assembly 160 can include a surface perpendicular to the axis A.

[0051] The magnetic circuit assembly 150 can be configured to generate a magnetic circuit that passes through the front plate assembly 154, the yoke assembly 160, and across the gap 204. The magnetic circuit assembly 150 can be configured to cause about 80% to 99% of the magnetic flux in the magnetic circuit to cross the gap 204. This is especially true for the core magnet configuration. In some embodiments (e.g., the annular magnet design), the magnetic flux crossing the gap 204 can account for 50% to 80% of the total magnetic flux. In some embodiments, the magnetic flux can account for about 70% of the total magnetic flux. One or more elements of the magnetic circuit assembly 150 can be provided within the gap 204. For example, the bobbin 102 and / or the coil 104 can be provided within the gap 204. When the magnetic flux interacts with the coil 104, the coil 104 vibrates and can generate sound, such as from the speaker 100.

[0052] As shown in the figure, in some embodiments (e.g., in the annular magnet design), the windings of the coil 104 are provided on the side of the bobbin 102 opposite the pole piece 158. However, in other embodiments (e.g., the core magnet design), the windings of the coil 104 can be located on the side of the bobbin 102 opposite the magnet 152, or on both sides of the bobbin. The height 208 of the coil 104 can be defined along the axis A (e.g., Figure 5as shown). In some embodiments, the height 208 of the coil 104 can be approximately equal to the height of the T-shaped portion of the front panel assembly 154 and / or the yoke assembly 160 (if applicable). In some designs, the height 208 of the coil 104 is less than or greater than the height of the front panel assembly 154. For example, the height 208 of the coil 104 can be approximately half of the height of the front panel assembly 154. In some embodiments, the height 208 can be between about 0.1 mm and 150 mm. For example, in some embodiments, the height 208 can be between about 10 mm and 30 mm. This range can provide a sufficiently small form factor while achieving a relatively large volume. In some examples, the height 208 of the coil 104 is about 12 mm. This can be about half of the voice coil height of other speaker models that can produce the same volume output. For larger speakers, a larger height 208 is possible. The height 208 of the coil 104 can be referred to as the "winding width" or WW. The width of the coil 104 (e.g., radial) can be between about 55% and 90% of the width of the gap 204. In some embodiments, the width of the coil 104 is about 71% or about 75% of the width of the gap 204. It is advantageous to reduce the width of the gap 204. For example, reducing the width of the gap 204 can improve the performance of the speaker 100 by, for example, improving the integrity of the sound with respect to the electrical input. The width of the gap 204 can be between about 1 mm and 12 mm. In some embodiments, the width of the gap 204 is about 3.5 mm. In some embodiments, the width is about 2 mm. In some embodiments, in order to produce a specific range of linear displacements of the speaker within a certain tolerance of the BL product during the voice coil stroke, other combinations of gap height and winding width may be considered necessary. The BL product is the force factor of the speaker, which roughly corresponds to the product of the length (L) of the conductor in the magnetic field and the magnetic field strength (B) around the conductor, and also roughly corresponds to the driving force generated by the conductor when a certain current passes through the conductor.

[0053] For example, the magnetic circuit assembly in a speaker can take various forms. For example, embodiments of the magnetic circuit assembly can include one or more of the features generally described above. In some cases, it may be advantageous to increase the magnetic flux through a gap (such as gap 204) by reducing the magnetic resistance in other regions of the magnetic circuit. This can be achieved in a variety of ways. One method can include reducing or eliminating the gaps (such as glue gaps or other interface layers) between the individual components of the magnetic circuit, such as the gaps between the magnet 152 components, the front plate assembly 154 components, the back plate 156 components, the pole piece 158 components, and / or any of the above components. For example, it may be advantageous to provide separate first and second plates in the front plate assembly 154, where each plate is directly fixed (such as by glue) to the magnet 152. In some embodiments, the separate first and second front plates are forged and adhered to the magnet without machining, thus saving a significant amount of manufacturing cost while eliminating the gap between the front plate components and reducing magnetic losses.

[0054] Figure 6 A cross-sectional schematic view of an exemplary magnetic circuit assembly 350 is shown. The magnetic circuit assembly 350 can include a first magnet 152; a front plate assembly 154 including a first plate 302, a second plate 304, a second magnet 306, and a top cover 308; and a yoke 360. The magnetic circuit assembly 350 can include other elements not shown and / or described elsewhere herein. The yoke 360 can be coupled to the first magnet 152 along the proximal surface of the magnet 152. The second plate 304 can be coupled to the first magnet 152 along the distal surface of the first magnet 152 and the proximal surface of the second plate 304. The first plate 302 can be coupled to the second plate 304 along the distal surface of the second plate 304 and the proximal surface of the first plate 302. The second magnet 306 can be coupled to the first plate 302 along the distal surface of the first plate 302 and the proximal surface of the second magnet 306. The top cover 308 can be coupled to the second magnet 306 along the distal surface of the second magnet 306 and the proximal surface of the top cover 308. The first plate 302 and / or the second plate 304 can be manufactured separately (such as forged) and attached as shown. The first plate 302 and the second plate 304 can be manufactured as interchangeable parts. The first plate 302 and the second plate 304 can exhibit planar symmetry only in one rotational direction along a plane. For example, as shown, rotating the first plate 302 180 degrees about a vertical axis will cause it to no longer be in planar symmetry with the second plate 304. As an additional example, rotating the first plate 302 180 degrees about a horizontal axis will break the planar symmetry between the first plate 302 and the second plate 304, as shown.

[0055] As shown, in some embodiments, each of the first plate 302 and the second plate 304 may have respective first and second radial portions, and the respective first radial portions have a smaller axial dimension than the respective second radial portions. As shown, the second plate 304 has a first radial portion 304a and a second radial portion 304b. The first plate 302 may have similar radial portions (not labeled). In some embodiments, the first radial portion 304a may be an inner radial portion relative to the second radial portion 304b (e.g., Figure 2 ). Alternatively, the first radial portion 304a may be an outer radial portion relative to the second radial portion 304b (e.g., Figure 4 ). The distance between the first plate 302 and the magnet 152 may be less than 0.5 millimeters. In some embodiments, the distance is about 0.1 millimeter and may be the location where the adhesive is applied. The first plate 302 may be fixed to the magnet 152 along the proximal surface of the first plate 302 (e.g., adjacent to the first region). The first plate 302 may be fixed to the magnet 152 using attachment means known in the art (e.g., adhesives, bonding, etc.). In some designs, the side surface 302c of the first plate 302 coincides radially with the side surface 304c of the second plate 304 (e.g., at an equal distance 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 may form an L shape. The first plate 302 and / or the second plate 304 may exhibit asymmetry along a horizontal axis. Additionally or alternatively, the first plate 302 and / or the second plate 304 may exhibit asymmetry along a vertical axis. The first plate 302 may include a material having a high magnetic permeability, such as steel (e.g., low-carbon steel) and / or iron. Other materials with higher magnetic permeability are also possible, such as composite materials.

[0056] The (e.g., axially defined) height of the side surface of the first plate 302 can be determined at least in part by the material used in the first plate 302. For example, it may be advantageous to avoid magnetic saturation of the material in the first plate 302. However, it may also be preferred to have a certain minimum saturation level. For example, in some embodiments, the saturation level of one or more components of the magnetic circuit (e.g., coil 104, front plate assembly 154, etc.) can be between about 85% and 99% of the saturation point of the material of the one or more components. For example, certain types of steel (e.g., low-carbon steel) can have a magnetic saturation point of about 2T. In this example, it may be preferred to have a saturation level greater than about 90% (e.g., 1.8T) and / or between about 92.5% (e.g., 1.7T) and 97.5% (e.g., 1.95T). Saturation levels within these ranges help reduce the effects of the current passing through the coil and / or the movement of the coil 104 in a fixed magnetic field, thereby reducing flux modulation. This can also reduce the resulting distortion. Additionally, this can also reduce the effect of materials such as steel on the inductance of the coil, thereby further reducing distortion.

[0057] The second plate 304 of the front plate assembly 154 can be arranged adjacent to the distal surface of the magnet 152. The distance between the second plate 304 and the magnet 152 can be less than 0.5 mm. In some embodiments, the first radial portion 304a and the second radial portion 304b may not overlap.

[0058] In some embodiments, the first plate 302 and the second plate 304 are axially separated by a space (e.g., not in contact with each other). The second plate 304 can be fixed to the magnet 152 using attachment means known in the art (e.g., adhesives, bonding, etc.). The short-circuit ring 320 can be disposed in the space axially separating the first plate 302 and the second plate 304. Additionally or alternatively, the first plate 302 and the second plate 304 can be arranged adjacent to each other along respective portions (e.g., radial portions) of each plate. This enables the short-circuit ring to be placed in a more advantageous position within the assembly than other positions of the voice coil winding.

[0059] As Figure 6 shown, in some embodiments, at least a portion of each of the first plate 302 and the second plate 304 can 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 the axis A. The first plate 302 and the second plate 304 can be generally composed of a ferromagnetic metal such as iron or steel. The (e.g., axially defined) height of the side surface 304c can be determined at least in part by the material used in the second plate 304. For example, it may be advantageous to avoid magnetic saturation of the material in the second plate 304. However, as described herein, some degree of magnetic saturation may also be preferred.

[0060] The yoke 360 can have the same as described aboveFigure 1 and 2 features common to the yoke assembly 160 in 2 . The yoke 360 can be formed in a U - shape. For example, the first leg of the yoke 360 forming the first section of the "U - shape" can be fixed to the proximal surface of the magnet 152. The second leg of the yoke 360 forming the second section of the "U - shape" can extend a greater axial distance than the first leg. As Figure 6 shown, the first part 330 of the second leg of the yoke 360 can be disposed opposite the magnet 152. The second part 332 of the second leg of the yoke 360 can be disposed opposite the side surface 304c of the second plate 304, thereby forming the first gap 312. The third part 334 of the second leg of the yoke 360 can be disposed opposite the side surface 302c of the first plate 302, thereby forming the second gap 314. The second leg of the yoke 360 can be axially tapered as Figure 6 shown. For example, the third part 334 of the yoke 360 can be narrower than the first part 330 of the yoke 360. The extending surface 340 of the yoke 360 can be coplanar and / or parallel with the axis A. The height of the most distal part of the third part 334 of the yoke 360 can be close to (e.g., below) the most distal surface of the top cover 308 and / or the most distal surface of the second magnet 306. As described above, such an arrangement can enhance the magnetic flux through the air and / or through one or more components of the frame (e.g., of a speaker).

[0061] The coil 104 (not shown) can be included in the magnetic circuit assembly 350. The coil 104 can be wound around the bobbin 102. Other features of the coil 104 and / or the bobbin 102 of the magnetic circuit assembly 350 can be as described above with reference to Figure 1 and 2 described. The coil 104 can have a height 208 extending within the first gap 312 and / or the second gap 314. The coil 104 can be configured to be modulated within the first gap 312 and / or the second gap 314 during use, depending on the needs of the magnetic circuit (e.g., to produce altered sound). In some designs, the coil 104 extends horizontally from the distal surface of the first plate 302 to the proximal surface level of the second plate 304. However, the coil 104 can also be shorter (e.g., having a smaller height 208).

[0062] As described below, the radially tapered portions of the first plate 302 and the second plate 304 can enhance the magnetic flux passing through the respective first gap 312 and second gap 314. Thereby, the strength of the magnetic circuit can be enhanced. This can achieve performance thresholds that were previously unattainable with similar form factors. For example, if a magnetic circuit assembly 150 as described herein is included in a speaker assembly, the volume can be increased.

[0063] 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 ring or a short - circuited turn. The short - circuit ring 320 may include a metal such as copper, aluminum, or other conductive materials. The short - circuit ring 320 may be configured as a magnetic - flux insulator such that it does not conduct magnetic flux well. It may be advantageous to include one or more short - circuit rings (such as the short - circuit ring 320) to improve the function of the magnetic circuit assembly 350, for example, 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 passing through the gap (such as the gap 204) in the permanent magnetic field. Additionally or alternatively, the short - circuit ring 320 may reduce the effective inductance of the coil 104 (not shown) within one or more frequency ranges (such as higher frequencies). The effective frequency range may be affected by the degree to which the short - circuit ring reduces the inductance. For example, without being limited by theory, the more the inductance is reduced, the lower the frequency range in which the short - circuit ring is effective. In some designs, the short - circuit ring (such as the short - circuit ring 320) is adjacent to the yoke 360. However, one or more short - circuit rings may be arranged in a variety of configurations. For example, the short - circuit ring 320 may be disposed between the first plate 302 and the magnet 152, between the first plate 302 and the second plate 304 (as shown in the figure), and / or adjacent to or near a portion of the yoke 360. For example, the short - circuit ring 320 may be disposed opposite the second plate 304, opposite the first plate 302, opposite the magnet 152 adjacent to or near the yoke 360, and / or disposed in a slot of the yoke 360. In certain configurations (such as magnetic - core designs), the short - circuit ring is disposed radially inside the coil 104. In some embodiments, the short - circuit ring may be replaced by an electrical short - circuit ring of a wire that occupies the same space, or by a wire ring connected to a selected or variable resistor placed inside or outside the motor assembly and electrically in series with the wire ring, thereby providing an adjustable or variable effect of the short - circuit structure.

[0064] Figure 7 Another exemplary magnetic circuit assembly 350 and simulated magnetic field lines are shown. As shown, the magnet 152 may be oriented such that the magnetic field lines emanating from it are parallel to the central axis A. The arrangement and shape of the first plate 302, the second plate 304, and the yoke 360 may generate compact magnetic field lines passing through the first gap 312 and the second gap 314 (not shown here). The coil 104 may be configured to translate within these gaps. Such compact magnetic field lines may prevent a large amount of magnetic field leakage from the magnetic circuit assembly. As Figure 7 shown, compared to other designs, the design using multiple plates in the front - plate assembly may make the magnetic - field intensity in the region where the coil 104 is located more uniform. Figure 7A short - circuit ring 320 disposed between a first plate 302 and a second plate 304 is shown. The short - circuit ring 320 can be adjacent to one or both of the first plate 302 and / or the second plate 304. For example, the short - circuit ring 320 can be adhered to one or both of them, or mechanically fixed between the two. Providing separate plates 302, 304 can enable the short - circuit ring 320 to be better placed between the plates, thus providing more benefits of the designs described herein.

[0065] Figure 8 The figure shows the product of the magnetic - field strength (B, in T) and the distance (L, in m) (BL product, in Tm) along an exemplary voice coil of various magnetic circuits described with reference to Figure 7 the values (in mm). The voice coil can be, for example, the coil 104. Generally, it is advantageous to make the BL value approximately constant (or "flat") over a relatively large length with respect to the rest position of the voice coil. As shown, for example, between - 5.0 mm and 10.0 mm, the BL value is flat. Compared with a loudspeaker having a relatively large slope in the range from - 5.0 mm to 10.0 mm, this can improve the sound quality and increase the linearity of the response of the coil 104 to the input signal. For example, this can also reduce harmonic distortion. Figure 8 Also shown are the values (in mm) of the magnetic - field strength (B, in T) along an exemplary voice coil of various magnetic circuits described with reference to Figure 7 . Generally, it is advantageous to make the distribution of the B value approximately symmetric with respect to the center of the voice coil. As shown, Figure 7 the B values of the design shown are quite symmetric over the distances shown. This can improve the predictability and consistency of the sound produced by a given input.

[0066] Figure 9 A cross - sectional schematic view of another exemplary embodiment of a ring - magnet design of a loudspeaker according to some embodiments is shown. As Figure 9As shown, the magnetic circuit assembly may include a first plate 302 and a second plate 304 located below (e.g., proximal to) the ferromagnetic metal frame of the speaker. As shown, the first magnet 152 may be disposed along the surface of the yoke 360, and the second plate 304 may 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 farther than the most distal surface of the first plate 302, so as to generate 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, forming a part of the magnetic circuit. The second magnet 306 interfaces with the ferromagnetic frame of the speaker on its proximal side and with air on its distal side, thereby forming an air circuit for the second magnet 306. Thus, in some embodiments, the ferromagnetic member of the frame may be "clamped" between the second magnet 306 and the first plate 302. In some embodiments, a top cover 308 is included along the distal surface of the second magnet 306. However, there may be no top cover in certain embodiments.

[0067] Figure 10 A cross-sectional schematic view of an exemplary embodiment of an annular magnet design of a speaker according to some embodiments is shown. Figure 10 The illustrated embodiment may include Figure 9 many features in Figure 10 including a second magnet 306 that is adjacent (e.g., below) a portion of the magnetic yoke 360 and located above another portion of the magnetic 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 formed in a U shape. The second magnetic yoke 359 may serve as a magnetic path around one or more other elements in the magnetic circuit assembly. For example, as shown, the second magnetic yoke 359 may be coupled to the first plate 302 and / or the second magnet 306. The second magnetic yoke 359 may serve as a barrier to capture lost magnetic flux, thereby improving magnetic efficiency. This barrier effect can reduce the interaction between the magnetic field and certain types of sensitive devices. The first magnet 152 helps to provide additional magnetic flux to the front plate assembly in the strengthening direction, thereby increasing the available magnetic flux in the magnetic circuit. The second magnet 306 may include one or more features of the second magnet 306 in the above-described other embodiments.

[0068] Exemplary Embodiment

[0069] Feature 1. A magnetic circuit included in a speaker, the magnetic circuit 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, the distal surface of the second plate being disposed along the proximal surface of the first plate, at least one of the first plate or the second plate having a first radial portion and a second radial portion, the first radial portion having a smaller axial dimension than the second radial portion; a magnet having a distal surface and a proximal surface, the distal surface of the magnet being disposed along the proximal surface of the second plate; and a yoke disposed along the proximal surface of the magnet, the shape of the yoke being designed to radially form a first magnetic circuit gap and a second magnetic circuit gap between the yoke and the first plate and the second plate, respectively.

[0070] Feature 2. The magnetic circuit according to Feature 1, wherein the yoke is formed in a U shape.

[0071] Feature 3. The magnetic circuit according to Feature 1, wherein the sizes of the first magnetic circuit gap and the second magnetic circuit gap are designed to accommodate a voice coil therein.

[0072] Feature 4. The magnetic circuit according to Feature 3, wherein the first radial portion forms an axial gap between it and the other of the first plate or the second plate.

[0073] Feature 5. The magnetic circuit according to Feature 4, wherein the axial gap is configured to accommodate a short-circuit ring therein.

[0074] Feature 6. The magnetic circuit according to Feature 1, wherein the magnet includes an annular magnet.

[0075] Feature 7. The magnetic circuit according to Feature 1, wherein the magnet is configured to generate a higher magnetic flux than ferrite.

[0076] Feature 8. The magnetic circuit according to Feature 1, wherein the magnet includes neodymium.

[0077] Feature 9. The magnetic circuit according to Feature 1, further comprising a second magnet, the proximal surface of the second magnet being disposed along the distal surface of the first plate.

[0078] Feature 10. The magnetic circuit according to Feature 9, further comprising a second magnet, the distal surface of the second magnet being disposed more distally than the most distal surface of the yoke.

[0079] Feature 11. The magnetic circuit according to Feature 1, further comprising a frame coupled to the distal end of the yoke, wherein the first magnet is disposed relative to the yoke such that the magnetic flux from the magnet is configured to substantially pass through the frame.

[0080] Feature 12. The magnetic circuit according to Feature 1, wherein each of the first plate and the second plate has respective first and second radial portions, and the respective first radial portions have a smaller axial dimension than the respective second radial portions.

[0081] Feature 13. The magnetic circuit according to Feature 1, wherein the first radial portion is closer to the first magnetic circuit gap than the second radial portion.

[0082] Feature 14. A loudspeaker, comprising: a magnetic circuit including: a first magnet having a distal surface and a proximal surface; a first plate having a distal surface and a proximal surface, the distal surface of the first plate being disposed along the proximal surface of the first magnet; a second plate having a distal surface and a proximal surface, the distal surface of the second plate being disposed along the proximal surface of the first plate; a second magnet having a distal surface and a proximal surface, the distal surface of the second magnet being disposed along the proximal surface of the second plate; and a yoke disposed along the proximal surface of the second magnet, the shape of the yoke being designed to radially form a first magnetic circuit gap and a second magnetic circuit gap between the yoke and the first plate and the second plate respectively; wherein the distal surface of the first magnet is disposed more distally than the most distal surface of the yoke; a voice coil configured to be disposed at least between the first magnetic circuit gap and the second magnetic circuit gap; a diaphragm coupled to the voice coil; and a frame configured to support the diaphragm and operatively coupled to the yoke.

[0083] Feature 15. The loudspeaker according to Feature 14, wherein an outer radial portion of the first plate has a smaller axial dimension than an inner radial portion of the first plate, and wherein an outer radial portion of the second plate has a smaller axial dimension than an inner radial portion of the second plate.

[0084] Feature 16. The loudspeaker according to Feature 15, wherein inner radial portions of the first plate and the second plate form an axial gap.

[0085] Feature 17. The loudspeaker according to Feature 16, wherein the axial gap is configured to accommodate a shorting ring therein.

[0086] Feature 18. The loudspeaker according to Feature 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.

[0087] Feature 19. A loudspeaker, comprising: a magnetic circuit, including: a first plate and a second plate, each plate being disposed between a first magnet and a second magnet, at least one of the first plate or the second plate presenting an asymmetry about a horizontal axis; and a yoke disposed along the second magnet, the shape of the yoke being designed to radially form a first magnetic circuit gap and a second magnetic circuit gap respectively between the yoke and the first plate and the second plate; a voice coil configured to be disposed at least between the first magnetic circuit gaps and between the second magnetic circuit gaps; a diaphragm joined to the voice coil; and 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.

[0088] Feature 20. The loudspeaker according to Feature 19, wherein an outer radial portion of the first plate has a smaller axial dimension than an inner radial portion of the first plate, and wherein an outer radial portion of the second plate has a smaller axial dimension than an inner radial portion of the second plate.

[0089] Feature 21. The loudspeaker according to Feature 20, wherein inner radial portions of the first plate and the second plate form an axial gap.

[0090] Feature 22. The loudspeaker according to Feature 21, wherein the axial gap is configured to accommodate a short-circuit ring therein.

[0091] Feature 23. The loudspeaker according to Feature 21, wherein at least one of the first magnet or the second magnet includes neodymium.

[0092] Conclusion

[0093] References in this specification to "some embodiments" or "an embodiment" mean that a particular feature, structure, or characteristic associated with the embodiment is included at least in some embodiments. Thus, the appearances of "in some embodiments" or "in an embodiment" throughout this specification are not necessarily referring to the same embodiment, but may refer to one or more identical or different embodiments. Furthermore, it will be apparent to those of ordinary skill in the art based on this disclosure that the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0094] As used in this application, the terms "comprising", "including", "having", etc. are synonyms and are used in an open and inclusive manner, which does not exclude other elements, features, actions, operations, etc. Furthermore, the term "or" is used in its inclusive sense (rather than its exclusive sense), so for example when it is used to connect a series of elements, the term "or" means one, some, or all of the elements in the series.

[0095] Similarly, it should be understood that in the description of the above embodiments, various features are sometimes combined in a single embodiment, drawing, or description thereof for the purpose of streamlining the disclosure and aiding in a better understanding of one or more of the various inventive aspects. However, this method of disclosure should not be interpreted as reflecting an intention that any claim requires more features than are expressly recited in that claim. Rather, the inventive aspects lie in combinations fewer than all of the features of any of the foregoing disclosed embodiments. Thus, no single feature or group of features is necessary or indispensable for every embodiment.

[0096] Numerous applications, publications, and external documents may be incorporated herein by reference. Any conflict or contradiction between the statements in the body of this specification and those of any incorporated document shall be resolved in favor of the statements in the body of this specification.

[0097] Although described in an illustrative context based on certain preferred embodiments and examples, those skilled in the art will understand that the present disclosure extends beyond these specifically described embodiments to other alternative embodiments and / or uses and to obvious modifications and equivalents. Accordingly, the scope of the appended claims should not be limited by the specific embodiments described above.

Claims

1. A magnetic circuit included in a loudspeaker, the magnetic circuit 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, the distal surface of the second plate being disposed along the proximal surface of the first plate, at least one of the first plate or the second plate having a first radial portion and a second radial portion, the first radial portion having a smaller axial dimension than the second radial portion; A magnet having a distal surface and a proximal surface, the distal surface of the magnet being disposed along the proximal surface of the second plate; A second magnet configured to increase the magnetic flux within the magnetic circuit; A yoke disposed along the proximal surface of the magnet, the shape of the yoke being designed to radially form a first magnetic circuit gap and a second magnetic circuit gap respectively between the yoke and the first plate and the second plate.

2. The magnetic circuit according to claim 1, wherein the yoke is formed in a U shape.

3. The magnetic circuit according to claim 1, wherein the sizes of the first magnetic circuit gap and the second magnetic circuit gap are designed to accommodate 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 accommodate a short-circuit ring therein.

6. The magnetic circuit according to claim 1, wherein the magnet includes an annular magnet.

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

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

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

10. The magnetic circuit according to claim 9, wherein the second magnet includes a distal surface disposed more distally than 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, wherein the first magnet is disposed relative to the yoke such that the magnetic flux from the magnet is configured to substantially pass through the frame.

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

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 loudspeaker, comprising: A magnetic circuit, comprising: A first magnet having a distal surface and a proximal surface; A first plate having a distal surface and a proximal surface, the distal surface of the first plate being disposed along the proximal surface of the first magnet; A second plate having a distal surface and a proximal surface, the distal surface of the second plate being disposed along the proximal surface of the first plate; A second magnet having a distal surface and a proximal surface, the distal surface of the second magnet being disposed along the proximal surface of the second plate; and A yoke disposed along the proximal surface of the second magnet, the yoke being shaped to radially form a first magnetic path gap and a second magnetic path gap between the yoke and the first plate and the second plate, respectively; Wherein the distal surface of the first magnet is disposed more distally than the most distal surface of the yoke; A voice coil configured to be disposed at least between the first magnetic path gaps and between the second magnetic path gaps; A diaphragm engaged with the voice coil; and A frame configured to support the diaphragm and operably coupled to the yoke.

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

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

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

18. The loudspeaker 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 loudspeaker, comprising: A magnetic circuit, comprising: A first plate and a second plate, wherein each plate is disposed between a first magnet and a second magnet, and at least one of the first plate or the second plate exhibits asymmetry about a horizontal axis; and A yoke disposed along the second magnet, the yoke being shaped to radially form a first magnetic path gap and a second magnetic path gap between the yoke and the first plate and the second plate, respectively; A voice coil configured to be disposed at least between the first magnetic path gaps and between the second magnetic path gaps; A diaphragm engaged with the voice coil; and 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.

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

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