Patent Publication Number: US-8983112-B2

Title: Planar speaker system

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The invention generally relates loudspeakers for use in audio systems, and more particularly to planar speaker systems. 
     2. Related Art 
     The general construction of an electro-dynamic speakers, sometimes referred to as a planar speakers, includes a diaphragm in the form of a thin film attached intention to a frame. An electrical circuit, in the form of electrically conductive traces, is applied to the surface of the diaphragm. Magnetic sources, typically in the form of permanent magnets, are mounted adjacent to the diaphragm or within the frame, creating a magnetic field. When current is flowing in the electrical circuit, the diaphragm vibrates in response to the interaction between the current and the magnetic field. The vibration of the diaphragm produces the sound generated by the planar speaker. 
     SUMMARY 
     A planar speaker system may include a bottom frame having a cavity. Within this cavity is a plurality of magnets arranged to form a substantially circular pattern. A diaphragm, having a plurality of electrically conductive traces formed is connected to the bottom frame and extends across the cavity of the bottom frame. When current flows through the electrically conductive traces, the diaphragm vibrates in response to the interaction between the current and the magnetic field, thereby producing sound. 
     In another example, the diaphragm and bottom frame both have an inner diameter. A pole piece connects the inner diameter of the bottom frame and the inner diameter of the diaphragm. Generally, the pole piece is located such that the plurality of magnets are arranged around the pole piece in a substantially circular pattern. 
     In yet another example, the planar speaker system and any of the examples described above may also include a top frame connected to the bottom frame, such that the plurality of magnets are located between the bottom frame and the top frame. By so doing, the top frame can act as an aperture for guiding sound generated by the planar speaker system. 
     In still yet another embodiment, the planar speaker system may include both a top frame and a bottom frame, the top frame defines a first cavity and the bottom frame defines a second cavity. A first set of magnets is disposed in the first cavity and arranged in a substantially circular pattern. In like manner, a second set of magnets is disposed in the second cavity and arranged in a substantially circular pattern. The diaphragm is located between the first and second set of magnets and has electrically conductive traces formed which, as explained earlier, vibrates due to the interaction between the current applied thereto and the magnetic fields generated by both sets of magnets. 
     Further objects, features and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification. 
     Other systems, methods, features and advantages will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The system may be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views. 
         FIG. 1  illustrates an example of a planar speaker system having a plurality of magnets disposed in a frame in a substantially circular pattern. 
         FIG. 2  is an exploded view of the planar speaker system of  FIG. 1 . 
         FIG. 3  illustrates a bottom frame of the planar speaker system of  FIG. 1 . 
         FIG. 4  illustrates an example of a set of magnets arranged in a circular pattern within the bottom frame of  FIG. 3 . 
         FIG. 5  illustrates an example of a diaphragm having conductive traces placed thereon. 
         FIG. 6  illustrates an example of a frame, magnets, and a diaphragm of a planar speaker system. 
         FIG. 7  illustrates a top frame of the planar speaker system of  FIG. 6 . 
         FIG. 8  illustrates a cutaway view of the planar speaker system of  FIG. 1 . 
         FIG. 9  illustrates an exploded view of another embodiment of a planar speaker system having a first and second set of magnets arranged in a circular pattern. 
         FIG. 10  illustrates a cutaway view of the planar speaker system of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Often, space limitations in the listening environment prohibit the use of a loudspeaker in an audio system that possesses the preferred directivity pattern for the system&#39;s design. For example, the amount of space and the particular locations available in a listening environment for locating and/or mounting the loudspeakers of the audio system may prohibit the use of a particular loudspeaker that exhibits the intended directivity pattern. Also, due to space and location constraints, it may not be possible to position or oriented the desired loudspeaker in a manner consistent with the loudspeaker&#39;s directivity pattern. Consequently, size and space constraints of a particular environment may make it difficult to achieve the desired performance from the audio system. An example of a listening environment having such constraints is the interior passenger compartment of an automobile or other vehicle. 
     While the electric circuitry of electro-dynamic speakers may present design challenges, electro-dynamic loudspeakers are very desirable loudspeakers because they are designed to have a very shallow depth. With this dimensional flexibility, electro-dynamic loudspeakers may be positioned at locations where conventional loudspeakers would not traditionally fit. This dimensional flexibility is particularly advantageous in automotive applications where positioning a loudspeaker at a location that a conventional loudspeaker would not otherwise fit could offer various advantages. Further, because the final loudspeaker assembly may be mounted on a vehicle, it is important that the assembly be rigid during shipping and handling so that the diaphragm or frame does not deform during installation. 
     While conventional electro-dynamic loudspeakers are shallow in depth and may therefore be preferred over conventional loudspeakers for use in environments requiring thin loudspeakers, electro-dynamic loudspeakers have a generally rectangular planar radiator that is generally relatively large in height and width to achieve acceptable operating wavelength sensitivity, power handling, maximum sound pressure level capability and low-frequency bandwidth, limiting their applications. 
     In  FIG. 1 , an example of a planar speaker system  10  is shown. The planar speaker system  10  generally includes a top frame  12  having an outer diameter  14  and a bottom frame  16  also having an outer diameter  18 . The outer diameter  14  of the top frame  12  is connected to the outer diameter  18  of the bottom frame  16 . Generally, the frames  12  and  16  are made of steel, but may be made of any suitable material, such as other metals and plastics. 
       FIG. 2  is an exploded view of the planar speaker system  10  of  FIG. 1 . As stated previously, the planar speaker system  10  includes a top frame  12  having an outer diameter  14  and a bottom frame  16  having an outer diameter  18 . The bottom frame  16  defines a cavity  20 . The cavity  20  may be circular in shape. Located within the cavity  20  of the bottom frame  16  are magnets  22   a - 22   l . The magnets are generally arranged in a circular pattern about a central axis  24 . In this embodiment there are twelve magnets  22   a - 22   l , but any suitable number of magnets may be utilized. 
     Each of the plurality of magnets  22   a - 22   l  can each take a variety of different shapes such as a substantially trapezoidal shape, a substantially semi-circular shape, or a substantially triangular shape. The plurality of magnets  22   a - 22   l  may be either ferrite magnets or rare-earth magnets, or any other magnetic material. 
     Located above the plurality of magnets  22  is a diaphragm  26 . The diaphragm  26  includes a group of electrically conductive traces  28   a - 28   l . The electrically conductive traces  28   a - 28   l  may be formed in the diaphragm  26 , or may be coupled to a surface of the diaphragm  26 . In this embodiment, there are twelve electrically conductive traces  28   a - 28   l  that correspond to the twelve magnets  22   a - 22   l . The diaphragm  26  is connected to the outer diameter  18  of the bottom frame  16  and extends across the cavity  20  of the bottom frame  16 . The plurality of magnets  22   a - 22   l  may be enclosed between the diaphragm  26  and the bottom frame  16  in the cavity  20 . 
     Each of the electrically conductive traces  28   a - 28   l  are routed in/on the diaphragm in a predetermined shape to represent a coil having a central region where there are no electrically conductive traces. In one example, the each of the electrically conductive traces  28   a - 28   l  may be routed to form a triangular shaped coil having a generally triangular middle section  30   a - 30   l  around which each respective trace is routed. As shown, there are four turns to each of the traces  28   a - 28   l , however, any number of turns of the traces may be utilized. When a time-varying current is applied to the electrically conductive traces  28   a - 28   l , due to the coil configuration, an electromagnetic field is created by the electrically conductive traces  28   a - 28   l . The interaction of the electromagnetic field induced by the time varying current in the electrically conductive traces  28   a - 28   l  with the magnetic field produced by the magnets  22   a - 22   l  may cause the diaphragm  26  to vibrate, thereby producing a sound. Thus, time-varying current representative of music or a human voice can be applied to the electrically conductive traces  28   a - 28   l  to generate the music or human voice as audible sound. 
     The top frame  12  may have a plurality of openings  32   a - 32   l . The openings  32   a - 32   l  can direct the sound generated by the diaphragm  26  and the electrical traces  28   a - 28   l  have a current applied. The openings  32   a - 32   l  can vary in both number and in shape. The purpose of these openings  32   a - 32   l  may include guiding sound waves generated when the diaphragm  26  vibrates. 
     The top frame  12  may further include an inner diameter  34 . In like manner, the diaphragm  26  may include an inner diameter  36  and the bottom frame  16  may also include an inner diameter  38 . A pole piece  40  may be connected to the inner diameters  34 ,  36 , and  38  of the top frame  14 , diaphragm  26 , and bottom frame  16  respectively. A fastener, such as a screw  42  may extend within the inner diameters  34 ,  36 , and  38  of the top frame  12 , diaphragm  26 , respectively, and engage the cone  40  thereby holding the pole piece  40  in place and in connection with the top frame  12 , diaphragm  26 , and bottom frame  16 . In other examples, other forms of fastener, an adhesive, or any other retention device may be used. 
       FIG. 3  is a more detailed view of an example of the bottom frame  16 . As stated previously, the bottom frame  16  includes an outer diameter  18  and an inner diameter  38 . The bottom frame  16  may be shaped such that the cavity  20  is defined. Generally, the cavity  20  may be circular in shape as is the outer diameter  18  of the bottom frame  16 . 
       FIG. 4  is an example of the bottom frame  16  that includes magnets  22   a - 22   l  disposed within the cavity  20  defined by the bottom frame  16 . The magnets  22   a - 22   l  are arranged in a circular pattern about a central axis  24 . The magnets  22   a - 22   l  may take any of a variety of different shapes suitable for the application. In some examples, the magnets  22   a - 22   l  may be rectangular, trapezoidal, or semi-circular in shape. 
       FIG. 5 , a more detailed view of an example of the diaphragm  26 . As stated previously, diaphragm  26  includes an inner diameter  36  and an outer diameter  27 . The diaphragm  26  may be substantially circular in shape. The diaphragm  26  may be formed with a flexible substantially planar sheet material, such as a thin film, that may be attached, in tension, to the bottom frame  16 . Typically, the diaphragm  26  is constructed of a pre-expanded cellular plastic material, such as polystyrene or polyimide. The frequency response of a diaphragm  26  generally is determined by the type and density of its material, and the area, thickness and contour of its sound producing region. A predetermined tension may be used to optimize the resonance frequency of the diaphragm. Optimizing diaphragm resonance may extend the bandwidth and reduce sound distortion of the speaker. 
     Placed on the diaphragm  26  are conductive traces  28   a - 28   l . Each of the conductive traces  28   a - 28   l  generally defines an area  30   a - 30   l  that does not have any conductive traces. In one example, the areas  30   a - 30   l  that do not have conductive traces  30   a - 30   l  are generally rectangular and/or trapezoidal in shape. The conductive traces  28   a - 28   l  may be made of aluminum. Each of the conductive traces  28   a - 281  has first terminals  29   a - 29   l  and second terminal  31   a - 31   l . A voltage is applied across the first terminals  29   a - 29   l  and second terminal  31   a - 31   l , so as to provide a current thought the conductive traces  28   a - 28   l.    
     In  FIG. 6 , a more detailed view of an example of the diaphragm  26  having the conductive traces  28   a - 28   l  as well as the first set of the plurality of magnets  22   a - 22   l  is shown. Generally, the magnets  22   a - 22   l  are placed adjacent to the diaphragm such that the magnets  22   a - 22   l  have borders that generally define the open space  30   a - 30   l  and are aligned with of each of the respective conductive traces  28   a - 28   l . The traces  28   a - 28   l  are around the outside edge of magnets,  22   a - 22   l  but the inner circle of trace may overlap with edge of a magnet due to the strong magnetic flux intensity field. Each of the magnets  22   a - 22   l  may be aligned to have a polarity (north(N) or south(S)) facing the diaphragm  26  that is opposite an adjacently positioned magnet. Thus, a magnet has a reversed polarity when compared to the magnets positioned on either side. During operation, the alternating polarity of the magnets around the diaphragm  26  causes opposing attraction and repulsion of the traces by adjacently positioned magnets. 
       FIG. 7  is a more detailed view of an example of the top frame  12 . The top frame  12  has a plurality of openings  32   a - 32   l . The number of openings  32   a - 32   l  may vary significantly based on the application. As such, the openings  32   a - 32   l  may include fewer or more openings based on a variety of different shapes that are formed and configured to transmit sounds generated by the planar speaker system. In  FIG. 7 , the openings  32   a - 32   l  are formed to be axially aligned with the inner diameter  34  of the top frame  12  and to be substantially evenly spaced. The openings  32   a - 32   l  may be formed in a predetermined shape, such as a tapered shape such that each of the openings  32   a - 32   l  become increasingly larger with distance from the inner diameter  34 . In some examples, the openings  32   a - 32   l  may be formed to cooperatively operate as a waveguide or lens to provide directivity, dispersion, or any other effect on the sound waves emitted by the planar speaker system. The top frame  12  may also include passageways to eliminate restrictive airflow in front of the diaphragm. 
       FIG. 8  is a cutaway view of an example of the planar speaker system  10  of  FIG. 1 . As stated previously, the planar speaker system may include both a top frame  12  having an outer diameter  14  and a bottom frame  16  having an outer diameter  18 . The bottom frame  16  may define a cavity  20 , and within the cavity  20  magnets  22   a - 22   l  may be arranged in a substantially circular formation about a central axis  24 . The top and bottom frames each include outer diameters  14  and  18  respectively. 
     Additionally, the diaphragm  26  may be a predetermined shape, such as a circular diaphragm, that has an outer diameter  27  and an inner diameter  36 . In this example, there is also a first circular ring  44  and a second circular ring  46 . The first circular ring  44  is connected to the outer diameter  18  of the bottom frame  16 , while the second circular ring  46  is connected to the outer diameter  14  of the top frame  12 . The outer diameter of the diaphragm may be sandwiched between the first ring  44  and the second ring  46  to fixedly maintain the position of the diaphragm  27  with respect to the magnets  22 . 
     Further, the pole piece  40  has a top section  40   a  and a bottom section  40   b , with a fastener, such as a screw holding the pole piece sections together. The outer diameter of the pole piece  40  may be connected to the inner diameter  36  of the diaphragm. The fastener may connect the portions  40   a  and  40   b  of the pole piece  40  such that the inner diameter  36  of the diaphragm  26  is connected to the pole piece  40 .  FIG. 9  is another example of the speaker system  110 . In this embodiment, similar reference numerals will be used to refer to similar items, with the difference that numerals will be incremented by  100 . Like before, this embodiment may include a top frame  112  and a bottom frame  116 . In this example, the speaker system  110  is substantially circular, in other examples, the speaker system  110  may be formed in other shapes, such as an ellipse. In  FIG. 9 , the top frame  112  has an outer diameter  114 , while the bottom frame  116  has an outer diameter of  118 . Like before, the bottom frame  116  may define a cavity  120 . However, the top frame  112  may also define a top cavity  121 . 
     Magnets  122  may be disposed within the cavity  120  of the bottom frame  116  in a circular pattern. Additionally, a diaphragm  126  may be connected to the outer diameter  118  of the bottom frame  116  or the outer diameter  114  of the top frame  112 . The diaphragm  126  may include electrically conductive traces  128   a - 128   l . These electrically conductive traces  128   a - 128   l  are similar to those previously described regarding electrically conductive traces  28   a - 28   l , in the paragraphs and figures above. The speaker system  110  also includes magnets  123  disposed in the cavity  121  in a circular fashion about a central axis. The upper magnets may be lined up exactly like a mirror 3-D image of bottom magnet matrix based on the diaphragm, the bottom polarity of upper magnet should be the same polarity as the top of bottom magnet. 
       FIG. 10  is a cutaway view of the speaker system  110  of  FIG. 9 . Here, the speaker system  110  includes the top frame  112  having an outer diameter  114  and a bottom frame having an outer diameter  118 . The top frame  112  defines a cavity  121  while the bottom frame  116  defines a cavity  120 . Located within the cavity  121  is the plurality of magnets  123   a - 123   l . In like manner, located within the bottom cavity  120  is a plurality of magnets  122   a - 122   l . As mentioned before, the magnets  122   a - 122   l  are arranged in a circular pattern about a central axis  124 . The speaker system  110  may also include annular ring  144  connected to outer diameter  118  and annular ring  146  connected to outer diameter  114 . The diaphragm  126  has an outer diameter  127  connected to the annular rings  144  and  146 . Further, the annular ring  126  also has an outer diameter  136  connected to a pole piece  140  that may have a top portion  140   a  and a bottom portion  140   b . Connecting the two portions  140   a  and  140   b  of the pole piece  140  is a fastener  142   
     While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.