Patent Application
20140363035
The present disclosure relates to a permanent magnet positioned between a woofer and a tweeter of a multi-way coaxial loudspeaker.
Coaxial loudspeakers (or speakers) arrange two or more drivers/transducers so that the sound produced radiates from the same point or axis. Coaxial speaker designs may be used in various applications where space or packaging constraints are imposed, such as in automotive applications, for example. Multi-way coaxial speakers may include two-way and three-way speakers having a higher frequency band transducer mounted along a common axis with one or more lower frequency band transducers. Two-way speakers typically have a high frequency band tweeter coaxially positioned with a low frequency woofer. Three-way speakers may include a high frequency tweeter in addition to a mid-range tweeter and a woofer with at least two of the transducers coaxially positioned. In various implementations, the tweeter is positioned in the center front of the woofer cone using a plastic support member, spacer, or pole disposed between the back of the tweeter and the top of the woofer center pole.
In addition to space and packaging considerations, automotive applications and various other applications may benefit from reducing weight associated with loudspeakers, particularly where multiple loudspeakers are employed. While ceramic ring magnets are suitable for many applications due to relatively low cost, it is difficult to use ceramic ring magnets for tweeters due to the size of magnet required and low magnetic flux intensity in the air gap, particularly in multi-way coaxial speakers. As such, many coaxial speakers use a more expensive rare-earth magnet for the tweeter to provide the desired magnetic flux in the air gap.
In one embodiment according to the present disclosure, a loudspeaker includes a woofer having a permanent ring magnet positioned around a center pole extending through the permanent ring magnet, a voice coil positioned within an air gap formed between the center pole and a top plate contacting the permanent ring magnet, a frame, a diaphragm coupled to the frame and the voice coil, and a spider coupled between the frame and the voice coil, a tweeter having a center pole generally coaxially aligned with the center pole of the woofer, and a permanent magnet extending between the center pole of the woofer and the center pole of the tweeter. In one embodiment, the permanent ring magnet of the woofer is positioned with opposite magnetic polarity relative to the permanent magnet extending between the center pole of the woofer and the center pole of the tweeter, and the permanent ring magnet of the tweeter is positioned with the same magnetic polarity as the permanent magnet extending between the woofer and the tweeter. An optional support structure, such as a plastic pole or cylinder may be formed around the permanent magnet extending between the woofer and the tweeter.
A method according to one embodiment of the present disclosure includes positioning a first permanent magnet between a center pole of a woofer and a center pole of a tweeter in a loudspeaker having the woofer and the tweeter generally coaxially aligned, the woofer including a motor having a second permanent magnet positioned to generate magnetic flux through the center pole of the woofer and through an air gap, a voice coil positioned within the air gap, a frame, a diaphragm coupled to the frame and the voice coil, and a spider coupled to the frame and the voice coil. The method may include positioning the first permanent magnet such that an associated magnetic polarity is opposite an associated magnetic polarity of the second permanent magnet. In one embodiment, the tweeter includes a third permanent magnet and the method further includes orienting the third permanent magnet such that an associated magnetic polarity is the same as the associated magnetic polarity of the first permanent magnet. The method may also include positioning the second permanent magnet around the outside of the center pole of the woofer or positioning the second permanent magnet substantially within the center pole of the woofer. In the latter case, the method may include positioning the first permanent magnet such that an associated magnetic polarity is the same as an associated magnetic polarity of the second permanent magnet.
Embodiments according to the present disclosure may also include a loudspeaker having a woofer including a motor with a first permanent magnet generating a flux path through an air gap, a voice coil at least partially positioned in the air gap, a frame, a suspension system connecting the voice coil to the frame, and a diaphragm connected between the voice coil and the frame, a tweeter generally coaxially positioned relative to the woofer and having a second permanent magnet, and a third permanent magnet coaxially positioned between the woofer and the tweeter. The first and third permanent magnets may be positioned with opposite magnetic polarity relative to the second permanent magnet. The first, second, and third permanent magnets may be implemented by ceramic magnets. In one embodiment, the first permanent magnet comprises a ceramic ring magnet extending around an exterior of a center pole of the woofer. In another embodiment, the first permanent magnet comprises a rare earth magnet positioned substantially within a center pole of the woofer. In one embodiment, the first permanent magnet has a diameter less than a diameter of the voice coil.
Various embodiments of a loudspeaker according to the present disclosure may provide one or more advantages. For example, use of a permanent magnet positioned between the center pole or core cap of a woofer and tweeter in a coaxial loudspeaker increases magnetic flux through the woofer motor and the tweeter motor such that the size and weight of the woofer and tweeter magnets may be reduced while providing similar performance to conventional designs. Similarly, the increased magnetic flux provided by the permanent magnet between the woofer and tweeter facilitates a smaller and less costly rare earth magnet for the woofer motor for those applications that incorporate rare earth magnets. The increased magnetic flux provided by the spacer or support magnet also facilitates a more compact woofer motor geometry having an internal rare earth magnet positioned substantially within the center pole of the woofer.
The above advantages and other advantages and features will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings.
As required, detailed embodiments are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary and may be embodied in various alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
As generally understood by those of ordinary skill in the art, different naming conventions may be used to designate which pole of a magnet is the North pole. As used throughout this disclosure, permanent magnets include a magnetic polarity with a North pole defined as the pole of the magnet that, when free to rotate, seeks the North pole of the Earth. Magnets described as having opposite or complementary polarity have a North pole of the first magnet nearer to the South pole of the second magnet. Magnets described as having the same or similar polarity are aligned or positioned such that the North pole of the first magnet is nearer to the North pole of the second magnet. Those of ordinary skill in the art will understand that any reference made in the following description to directions such as top, bottom, up, down, etc. refer to the particular figure being described and may be different in an actual implementation depending on the particular orientation of the speaker as installed in an application.
Similarly, magnet orientation or alignment may be described with reference to positive (+) and negative (−) magnetic poles. A magnetometer may be used to identify magnetic polarity in terms of electromagnetic polarity, which is positive (+) and negative (−), rather than the geographic compass needle identification north and south. A north seeking compass needle, which is magnetic positive, may be used to identify a negative magnetic field of a static field permanent magnet. Positive and negative magnetic poles may be used to describe or designate the direction of flow of magnetic flux.
Woofer 22 includes a permanent ring magnet 26 positioned around a center pole 28, which extends through permanent ring magnet 26. Permanent ring magnet 26 may be implemented by a ceramic magnet. In this embodiment, center pole 28 is integrally formed with bottom (or back) plate 30 in a magnet housing. However, bottom plate 30 may be a separate component secured to center pole 28 as generally understood by those of ordinary skill in the art. Bottom plate 30 or the bottom plate portion of center pole 28 contacts a corresponding bottom surface of permanent ring magnet 26. Similarly, a top (or front) plate 32 contacts a corresponding top surface of permanent ring magnet 26. Bottom plate 30 and top plate 32 may be of similar size and shape depending on the particular woofer motor design. Center pole 28 extends at least partially through the center opening of top plate 32 to form an air gap between center pole 28 and top plate 32.
A voice coil 40 is positioned at least partially within the air gap formed between top plate 32 and center pole 28. Voice coil 40 may be positioned in an overhung configuration extending completely through the air gap as shown, or in an underhung configuration extending only partially into the air gap depending on the particular application and implementation. A frame 42 is secured to top plate 32. Frame 42 may include openings around its perimeter as shown, or may be a solid or sealed construction. A suspension member or spider 44 is coupled to frame 42 and voice coil 40 to suspend voice coil 40 within the air gap. A cone or diaphragm assembly 46 is coupled to voice coil 40 and frame 42. Diaphragm assembly 46 includes cone 48 and surround 50. A seal or gasket 52 may extend around an interior opening of frame 42. An electrical connector or plug 56 may be secured to frame 42 and be electrically coupled to voice coil 40 to provide audio signals for operation of loudspeaker 20.
Tweeter 24 includes a center pole 60 that may be integrally formed with a bottom or back plate portion 62 with a similar construction as described with respect to woofer 22. A permanent magnet 64 is positioned between bottom plate 62 and top or front plate 66. In the exemplary embodiment illustrated, permanent magnet 64 is a ceramic ring magnet positioned around center pole 60 of tweeter 24. A diaphragm 72 suspends an associated voice coil 70 within an associated air gap between top plate 66 and center pole 60. Diaphragm 72 is coupled to a surround 68, which is secured to top plate 66.
Embodiments according to the present disclosure include a permanent magnet 78 extending between center pole 28 of woofer 22 and center pole 60 of tweeter 24. As generally shown in
As illustrated in the embodiments of
In the exemplary embodiment illustrated in
As generally illustrated in
The representative embodiment of a multi-way loudspeaker 220 illustrated in
In this embodiment, woofer 222 includes a first permanent magnet 226 positioned substantially within a center pole 228. Permanent magnet 226 may be implemented by a rare earth magnet, such as a neodymium or samarium-cobalt permanent magnet, for example. In this embodiment, the lower portion of center pole 228 is integrally formed with bottom (or back) plate 230 in a magnet housing or shellpot. However, bottom plate 230 may be a separate component secured to the bottom portion of center pole 228 as generally understood by those of ordinary skill in the art. The bottom portion of center pole 228 is in contact with the bottom surface of rare earth magnet 226. The top portion of center pole 228 is implemented by top or core cap 232, which includes a bottom surface in contacting a corresponding top surface of permanent rare earth magnet 226. Bottom plate 230 and core cap 232 may be of similar size and shape depending on the particular woofer motor design. The top portion of center pole 228, which is implemented by core cap 232 in this embodiment, forms an air gap between core cap 232 and the shellpot of woofer 222.
As generally illustrated in
A voice coil 240 is positioned at least partially within the air gap. A frame 242 is secured to shellpot 230. Frame 242 may include openings around its perimeter or may be a solid or closed construction. A suspension member or spider 244 is coupled to frame 242 and voice coil 240 to suspend voice coil 240 within the air gap. A cone or diaphragm assembly 246 is coupled to voice coil 240 and frame 242. Diaphragm assembly 246 includes cone 248 and surround 250.
Tweeter 224 includes a center pole 260 that may be integrally formed with a bottom or back plate portion 262. Back plate 262 may be integrally formed with center pole 260, or may be a separate component. A second permanent magnet 264 is positioned between bottom plate 262 and top or front plate 266. In the exemplary embodiment illustrated, permanent magnet 264 is a ceramic ring magnet positioned around center pole 260 of tweeter 224. A diaphragm 272 suspends an associated voice coil 270 within an associated air gap between top plate 266 and center pole 260. Diaphragm 272 is coupled to a surround 268, which is secured to top plate 266.
Embodiments according to the present disclosure include a third permanent magnet 278 coaxially positioned between the woofer 222 and tweeter 224. Permanent magnet 278 extends between core cap 232 of woofer 222 and center pole 260 of tweeter 224. As generally shown in
As illustrated in the embodiments of
In the exemplary embodiment having both an internal magnet woofer motor and magnetic spacer between the woofer and tweeter, the south magnetic pole of permanent magnet 226 contacts core cap 232 and the north pole contacts shellpot or bottom plate 230. Permanent magnet 278 is positioned so its south pole contacts core cap 232 of woofer 222 and its north pole contacts center pole 260 of tweeter 224. Permanent magnet 264 of tweeter 224 has its south pole in contact with the bottom plate 262 and its north pole in contact with top plate 266. A stainless steel screw (non-magnetic) 294 is used to fasten the woofer motor and tweeter motor through center hole of woofer's motor (226, 228 and 232), magnet cylinder 278 and tweeter back plate 262.
In the embodiment illustrated in
As such, various embodiments according to the present disclosure provide one or more advantages associated with a permanent magnet positioned between a woofer and a tweeter in a multi-way coaxial speaker. For example, use of a permanent magnet positioned between the center pole or core cap of the woofer and tweeter in a coaxial loudspeaker to increase magnetic flux through the woofer motor and the tweeter motor facilitates reduction of size and weight of the woofer and tweeter magnets while providing similar performance to conventional designs. Similarly, the increased magnetic flux provided by the permanent magnet between the woofer and tweeter facilitates a smaller and less costly rare earth magnet for the woofer motor for those applications that incorporate rare earth magnets. The increased magnetic flux provided by the spacer or support or center pole permanent magnet also facilitates a more compact woofer motor geometry having an internal rare earth magnet positioned substantially within the center pole of the woofer.
While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention. While various embodiments may have been described as providing advantages or being preferred over other embodiments with respect to one or more desired characteristics, as one skilled in the art is aware, one or more characteristics may be compromised to achieve desired system attributes, which depend on the specific application and implementation. These attributes include, but are not limited to: cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. The embodiments discussed herein that are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.
