PATENT DOCUMENT

Publication Number: US-10959024-B2
Application Number: US-201816144813-A
Country: US
Kind Code: B2

Title: Planar magnetic driver having trace-free radiating region

Abstract:
A planar magnetic driver including a radiating surface having a trace-free central region is described. The driver has a magnet defining an acoustic opening on a central axis. A diaphragm of the planar magnetic driver is held by mounts having a mounting profile around the central axis, and the diaphragm includes a radiating surface facing the acoustic opening. An innermost conductive trace on the diaphragm extends around a central region of the radiating surface within a magnetic flux of the magnet such that no conductive traces are on the central region. A radial distance between the innermost conductive trace and the mounting profile is less than another radial distance between the innermost conductive trace and the central axis. Accordingly, an excursion range of the diaphragm along the central axis is greater than a gap distance between the conductive trace and the magnet. Other aspects are also described and claimed.

Claims:
What is claimed is: 
     
       1. A planar magnetic driver, comprising:
 one or more mounts having a mounting profile extending around a central axis, wherein the mounting profile does not move along the central axis; 
 a magnet extending around the central axis to define an acoustic opening radially inward from the mounting profile; 
 a diaphragm mounted on the one or more mounts and including a flat region extending between the mounting profile and a central region having a radiating surface facing the acoustic opening; and 
 a plurality of conductive traces on the flat region, wherein the plurality of conductive traces include an innermost trace extending around the central region within a magnetic flux of the magnet, and wherein a first radial distance between the innermost trace and the mounting profile is less than a second radial distance between the innermost trace and the central axis. 
 
     
     
       2. The planar magnetic driver of  claim 1  further comprising a second magnet extending around the central axis concentrically with the magnet, wherein the diaphragm is within a magnetic gap between the magnet and the second magnet. 
     
     
       3. The planar magnetic driver of  claim 2 , wherein a gap distance of the magnetic gap is less than an excursion range of the diaphragm along the central axis. 
     
     
       4. The planar magnetic driver of  claim 2 , wherein the innermost trace is on an upper surface of the diaphragm, and wherein the plurality of conductive traces include a second innermost trace on a lower surface of the diaphragm within a second magnetic flux of the second magnet. 
     
     
       5. The planar magnetic driver of  claim 4 , wherein the innermost trace is electrically coupled to the second innermost trace. 
     
     
       6. The planar magnetic driver of  claim 1 , wherein the diaphragm has a second mode of vibration including a first node at the mounting profile, and a second node between the central axis and the magnet. 
     
     
       7. The planar magnetic driver of  claim 1 , wherein the one or more mounts are revolute joints coupling the diaphragm to a carrier. 
     
     
       8. The planar magnetic driver of  claim 7 , wherein the one or more mounts include a first compliant pad and a second compliant pad, and wherein the diaphragm is mounted between the first compliant pad and the second compliant pad. 
     
     
       9. The planar magnetic driver of  claim 1 , wherein the central region has no conductive traces. 
     
     
       10. The planar magnetic driver of  claim 9 , wherein the central region is visually transparent. 
     
     
       11. A device, comprising:
 a planar magnetic driver including one or more mounts having a mounting profile around a central axis, wherein the mounting profile does not move along the central axis, a magnet extending around the central axis to define an acoustic opening radially inward from the mounting profile, a diaphragm mounted on the one or more mounts and including a flat region extending between the mounting profile and a central region having a radiating surface facing the acoustic opening, and a plurality of conductive traces on the flat region, wherein the plurality of conductive traces include an innermost trace extending around the central region within a magnetic flux of the magnet, and wherein a first radial distance between the innermost trace and the mounting profile is less than a second radial distance between the innermost trace and the central axis; and 
 one or more processors configured to drive the planar magnetic driver with an audio signal. 
 
     
     
       12. The device of  claim 11  further comprising a second magnet extending around the central axis concentrically with the magnet, wherein the diaphragm is within a magnetic gap between the magnet and the second magnet, and wherein a gap distance of the magnetic gap is less than an excursion range of the diaphragm along the central axis. 
     
     
       13. The device of  claim 11 , wherein the diaphragm has a second mode of vibration including a first node at the mounting profile, and a second node between the central axis and the magnet. 
     
     
       14. The device of  claim 11 , wherein the one or more mounts are revolute joints coupling the diaphragm to a carrier. 
     
     
       15. The device of  claim 11 , wherein the central region has no conductive traces. 
     
     
       16. A headset, comprising:
 an earcup; and 
 a planar magnetic driver mounted in the earcup, wherein the planar magnetic driver includes one or more mounts having a mounting profile around a central axis, wherein the mounting profile does not move along the central axis, a magnet extending around the central axis to define an acoustic opening radially inward from the mounting profile, a diaphragm mounted on the one or more mounts and including a flat region extending between the mounting profile and a central region having a radiating surface facing the acoustic opening, and a plurality of conductive traces on the flat region, wherein the plurality of conductive traces include an innermost trace extending around the central region within a magnetic flux of the magnet, and wherein a first radial distance between the innermost trace and the mounting profile is less than a second radial distance between the innermost trace and the central axis. 
 
     
     
       17. The headset of  claim 16  further comprising a second magnet extending around the central axis concentrically with the magnet, wherein the diaphragm is within a magnetic gap between the magnet and the second magnet, and wherein a gap distance of the magnetic gap is less than an excursion range of the diaphragm along the central axis. 
     
     
       18. The headset of  claim 16 , wherein the diaphragm has a second mode of vibration including a first node at the mounting profile, and a second node between the central axis and the magnet. 
     
     
       19. The headset of  claim 16 , wherein the one or more mounts are revolute joints coupling the diaphragm to a carrier. 
     
     
       20. The headset of  claim 16 , wherein the central region has no conductive traces.

Description:
BACKGROUND 
     Field 
     Aspects related to a speaker driver are disclosed. More particularly, aspects related to a planar magnetic driver having conductive traces around a region of a radiating surface of a diaphragm are disclosed. 
     BACKGROUND INFORMATION 
     A speaker driver is a transducer that converts an electrical input audio signal into an emitted sound. One type of speaker driver is a planar magnetic driver. Planar magnetic drivers typically include a voicecoil on a planar film, which is placed between a pair of magnet assemblies. An audio signal is conducted through the voicecoil to cause the planar film to oscillate within a magnetic field of the magnet assemblies. The oscillating planar film can generate and emit sound. 
     Typically, the voicecoil of planar magnetic drivers includes conductive traces that extend across a radiating surface of the planar film. The radiating surface generates sound by oscillating during driver operation. The conductive traces may start on the radiating surface radially outward from a center of the planar film, and extend along a spiral or serpentine pattern toward the center. The trace pattern extends over the center, or over a central region, of the planar film and covers the radiating surface of the diaphragm. In some cases, a grill or acoustic wave guide is located over the radiating surface of the diaphragm. 
     SUMMARY 
     Existing planar magnetic drivers have several drawbacks. For example, traditional planar magnetic drivers have diaphragms located between a pair of magnet assemblies. The pair of magnet assemblies and corresponding traces on the diaphragm typically extend over a center of the diaphragm. This placement can limit movement of the diaphragm, which forces a tradeoff between acoustic range and driver efficiency. For example, a gap between the magnet and the diaphragm can be increased to allow the diaphragm to deflect more and generate lower frequency sounds, however, widening the gap also separates the magnet from the traces more, which can reduce an efficiency of the magnet-trace system. Furthermore, the magnet assemblies can degrade sound traveling along an acoustic radiation path from the radiating surface of the diaphragm. For example, the magnets can obscure the radiation path and block the sound. Similarly, the sound may pass through openings in the magnet assemblies, and the openings may act like resonator necks, causing standing waves to develop within the openings that further distorts the sound. An additional drawback is that the centrally located windings of existing planar magnetic drivers cover the central region of the radiating surface, which reduces visibility through the diaphragm. The reduced visibility makes existing planar magnetic drivers unsuitable for applications that would benefit from an ability to see through the diaphragm. 
     A speaker driver, and devices incorporating the speaker driver, are described. In an aspect, the speaker driver is a planar magnetic driver. The planar magnetic driver includes a diaphragm mounted on one or more mounts having a mounting profile that extends around a central axis. The driver includes one or more magnets, e.g., a pair of ring magnets, that extend around the central axis to define an acoustic opening that is radially inward from the mounting profile. The diaphragm has a radiating surface that faces the acoustic opening, and a central region of the radiating surface is radially inward of an inner surface of the magnets that define the acoustic opening. More particularly, the driver has conductive traces on the diaphragm, and an innermost trace extends around the central region of the radiating surface adjacent to an inner dimension of the magnet. Accordingly, the central region of the radiating surface is trace-free (no conductive traces are on the radiating surface over the central region) and is radially inward from the magnet. The trace-free central region of the radiating surface is axially aligned with the acoustic opening to generate sound that propagates through the acoustic opening into a surrounding environment when the driver is driven with an audio signal. 
     In an aspect, a magnetic gap is located between the pair of magnets, and a distance across the gap is less than an excursion range of the diaphragm. For example, when the diaphragm is excited, a center of the diaphragm moves between upper and lower limits that are separated by the excursion range. The excursion range can be greater than the gap distance in part because the magnets are located nearer to an outer perimeter of the diaphragm than the center of the diaphragm. More particularly, a radial distance between the center and the innermost trace on the diaphragm (or the inner dimension of the magnet) can be greater than a radial distance between the outer perimeter and the innermost trace (or the inner dimension of the magnet). Exciting the diaphragm from the outer region of the diaphragm, and not covering the acoustic opening with grills or acoustic waveguides, allows the center of the diaphragm to deflect substantially higher than the magnet surfaces facing the magnetic gap. Accordingly, air volume displacement and sound generation is increased. Furthermore, by not covering the acoustic opening with grills or acoustic waveguides, the distortion of the generated sound can be reduced. 
     The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims filed with the application. Such combinations have particular advantages not specifically recited in the above summary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a pictorial view of a user listening to a speaker driver, in accordance with an aspect. 
         FIG. 2  is a block diagram of a speaker driver incorporated into devices, in accordance with an aspect. 
         FIG. 3  is a perspective view of a planar magnetic driver, in accordance with an aspect. 
         FIG. 4  is a perspective sectional view of a planar magnetic driver, in accordance with an aspect. 
         FIG. 5  is a sectional view of a diaphragm supported between a magnet pair of a planar magnetic driver, in accordance with an aspect. 
         FIG. 6  is a sectional view of conductive traces on a diaphragm located within a magnetic flux of a planar magnetic driver, in accordance with an aspect. 
         FIG. 7  is a schematic view of a diaphragm of a planar magnetic driver being driven in a first mode of vibration, in accordance with an aspect. 
         FIG. 8  is a top view of a voicecoil circuit on a diaphragm of a planar magnetic driver, in accordance with an aspect. 
         FIG. 9  is a pictorial view of a voicecoil-loaded diaphragm being moved by a Lorentz force, in accordance with an aspect. 
         FIG. 10  is a pictorial view of a diaphragm mounted on a revolute joint of a planar magnetic driver, in accordance with an aspect. 
         FIG. 11  is a schematic view of a diaphragm of a planar magnetic driver being driven in a second mode of vibration, in accordance with an aspect. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects describe a speaker driver including a radiating surface having a trace-free region. The speaker driver can be a planar magnetic driver incorporated into a mobile device or a headset. In an aspect, the mobile device can be a smartphone and the headset can be circumaural headphones. The headset can include other types of headphones, such as earbuds or supra-aural headphones, to name only a few possible applications. In other aspects, the mobile device can be another device for rendering media including audio to a user, such as a desktop computer, a laptop computer, augmented reality/virtual reality headset, etc. 
     In various aspects, description is made with reference to the figures. However, certain aspects may be practiced without one or more of these specific details, or in combination with other known methods and configurations. In the following description, numerous specific details are set forth, such as specific configurations, dimensions, and processes, in order to provide a thorough understanding of the aspects. In other instances, well-known processes and manufacturing techniques have not been described in particular detail in order to not unnecessarily obscure the description. Reference throughout this specification to “one aspect,” “an aspect,” or the like, means that a particular feature, structure, configuration, or characteristic described is included in at least one aspect. Thus, the appearance of the phrase “one aspect,” “an aspect,” or the like, in various places throughout this specification are not necessarily referring to the same aspect. Furthermore, the particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more aspects. 
     The use of relative terms throughout the description may denote a relative position or direction. For example, “above” may indicate a location in a first direction away from a reference point. Similarly, “below” may indicate a location in a second direction away from the reference point and opposite to the first direction. Such terms are provided to establish relative frames of reference, however, and are not intended to limit the use or orientation of a speaker driver to a specific configuration described in the various aspects below. 
     In an aspect, a speaker driver includes a diaphragm mounted within a magnetic gap of a pair of magnets. The diaphragm carries conductive traces, and an innermost conductive trace extends around a central region of a radiating surface of the diaphragm, which faces an acoustic opening defined by one or more of the magnets. The central region of the radiating surface is trace-free because it is radially inward from the innermost conductive trace. Furthermore, the traces on the diaphragm can be located toward an outer perimeter of the diaphragm such that the diaphragm is excited from the outer perimeter when the conductive traces are driven. For example, a first radial distance between the innermost conductive trace and mounting locations along the outer perimeter of the diaphragm can be less than a second radial distance between the innermost conductive trace and a center of the diaphragm. Exciting the diaphragm from the outer perimeter allows the center of the diaphragm to deflect through an excursion range that is larger than a distance across the magnetic gap, when the speaker driver is driven with an audio signal. 
     Referring to  FIG. 1 , a pictorial view of a user listening to a speaker driver is shown in accordance with an aspect. A user  100  may listen to sounds generated by a mobile device  102  or a headset  104 . For example, mobile device  102  can be a smartphone, a laptop, a portable speaker, etc., having a speaker driver  106  to play sounds. Similarly, headset  104  can be circumaural headphones, supra-aural headphones, earbuds, etc., having speaker driver  106  to play sounds directly into an ear of user  100 . Speaker driver  106  can be mounted in an earcup  108 , and earbud, etc., of headset  104 . The generated sounds correspond to audio signals driving speaker driver  106 , such as an audio signal representing music, binaural audio reproductions, phone calls, etc. 
     In an aspect, mobile device  102  and/or headset  104  includes circuitry to perform the functions described below. For example, either device includes speaker driver  106 , which can be a planar magnetic driver to generate sounds. Planar magnetic driver  106  can be, for example, a high-quality, broadband speaker capable of emitting predetermined sounds generated based on known audio signals. Mobile device  102  and headset  104  can also include mechanical structures, such as a housing, a headband, or a neck cord to connect several speaker drivers together. 
     Referring to  FIG. 2 , a block diagram of a speaker driver incorporated into devices is shown in accordance with an aspect. Mobile device  102  can include one or more device processors  202  to execute instructions to carry out the different functions and capabilities described below. Instructions executed by device processor(s)  202  may be retrieved from a device memory  204 , which may include a non-transitory machine readable medium. The instructions may be in the form of an operating system program having device drivers and/or an audio rendering engine for rendering music playback, binaural audio playback, etc. The instructions can also pertain to telephony applications, email applications, browser applications, etc., running on mobile device  102 . Audio from the running applications can be played by speaker driver  106  of mobile device  102 . More particularly, device processor(s)  202  can be configured to drive speaker driver  106  with an audio signal. 
     To perform the various functions, device processor(s)  202  may directly or indirectly implement control loops and receive input signals from, and/or provide output signals to, other electronic components. For example, device processor(s)  202  may receive input signals from microphone(s) or menu buttons of mobile device  102 , including through input selections of user interface elements displayed on a display. 
     In an aspect, headset  104  includes one or more headset processors  202  to execute instructions to carry out the different functions and capabilities described below. Instructions executed by headset processor(s)  202  may be retrieved from a headset memory  204 , which may include a non-transitory machine readable medium. The instructions may be in the form of an operating system program having device drivers and/or an audio rendering engine for rendering music playback, binaural audio playback, etc., according to the methods described below. In an aspect, headset memory  204  stores audio data, e.g., a cached portion of audio data received from mobile device  102  via respective RF circuitry. Headset processor  202  can receive the cached portion and render the audio through speaker driver  106 . More particularly, headset processor(s)  202  can be configured to drive audio speaker with an audio signal. 
     To perform the various functions, headset processor(s)  202  may directly or indirectly implement control loops and receive input signals from, and/or provide output signals to, other electronic components. For example, headset processor(s)  202  may receive input signals from microphone(s) or inertial measurement unit(s) (IMU) of headset  104 . 
     Referring to  FIG. 3 , a perspective view of a planar magnetic driver is shown in accordance with an aspect. Speaker driver  106  incorporated in mobile device  102 , headset  104 , or any other device or apparatus, can be a planar magnetic driver  106 . Planar magnetic driver  106  can include a carrier  302  that allows speaker driver  106  to be mounted on another component of a device (e.g., a device housing of mobile device  102  or earcup  108  of headset  104 . Carrier  302  can hold other components of the driver  106 . For example, a diaphragm  304 , which can be a planar diaphragm, of speaker driver  106  may be mounted on one or more mounts ( FIG. 4 ). The mounts can that connect diaphragm  304  to carrier  302  along a mounting profile  306 . Mounting profile  306  can be a reference geometry (shown by dashed lines) along which diaphragm  304  is attached to carrier  302 . Mounting profile  306  can extend around a central axis  308 , and thus, diaphragm  304  can be secured at mounting locations surrounding central axis  308 . Diaphragm  304  can extend across central axis  308  between the mounting locations. More particularly, central axis  308  may intersect an upper or lower surface of diaphragm  304 . For example, the upper or lower surface can be a radiating surface  310 . Radiating surface  310  can be a region of diaphragm that is in motion when an electrical signal is applied to the transducer, as described below. Radiating surface  310  can have several sections or regions. In an aspect, a central region  311  is a portion of radiating surface  310  that is trace-free. Central axis  308  may extend orthogonal to a center  312  of diaphragm  304  on central region  311  of radiating surface  310 . 
     In an aspect, planar magnetic driver  106  includes one or more magnets  314  extending around central axis  308 . Speaker driver  106  can have a magnet pair including an upper magnet and a lower magnet. The magnets can be ring magnets  314 . For example, a shape of magnet(s)  314  when viewed in a direction of central axis  308  can be annular. The annular shape can have an outer dimension  318  adjacent to carrier  302 , and an inner dimension  320  nearer to central axis  308  than outer dimension  318 . Inner dimension  320  can surround and define an acoustic opening  316 . More particularly, an inner surface of magnet  314  facing central axis  308  can define a channel extending along the axis, which provides a port for sound to propagate from diaphragm  304  to a surrounding environment. Outer dimension  318  and inner dimension  320  of magnet  314  can be radially inward from carrier  302 , and thus, magnet(s)  314  and acoustic opening  316  can be radially inward from mounting profile  306 . Acoustic opening  316  can be located over central region  311  of radiating surface  310  on central axis  308 . Accordingly, radiating surface  310  can face acoustic opening  316  to generate sound that propagates through acoustic opening  316  toward a surrounding environment or an ear of user  100  when planar magnetic driver  106  is driven with an audio signal. 
     In an aspect, diaphragm  304  carries several conductive traces  322 . More particularly, conductive traces  322  can be formed or mounted on an upper or lower surface of diaphragm  304 . Alternatively, traces  322  can be embedded within a wall of diaphragm  304 . Conductive traces  322  can be located within a magnetic flux generated by the magnet(s)  314  of speaker driver  106 . For example, as described below, conductive traces  322  can be positioned in a flux of opposing ring magnets. Accordingly, when an audio signal is transmitted through conductive traces  322 , a combination of the magnetic flux and the electrical signal can generate a Lorentz force that acts on conductive traces  322 . The Lorentz force can move diaphragm  304  to generate sound. 
     Referring to  FIG. 4 , a perspective sectional view of a planar magnetic driver is shown in accordance with an aspect. An upper magnet  314  of planar magnetic driver  106  is omitted to reveal a second (lower) magnet  314  of the driver  106 . The revealed structure shows that, when viewed in cross-section, diaphragm  304  extends radially across acoustic opening  316  from a first mount  402  on mounting profile  306  to a second mount  402  on mounting profile  306 . Diaphragm  304  can be clamped by the mount(s)  402  along an outer perimeter. The outer perimeter may or may not be an outer edge of diaphragm  304 . For example, the outer perimeter can be a reference geometry on diaphragm  304 . The outer perimeter includes the locations on diaphragm  304  that are mounted on mounts  402 , and thus, the outer perimeter of diaphragm  304  is congruent with mounting profile  306  of mounts  402 . 
     In an aspect, the first mount  402  and the second mount  402  can be diametrically opposed across mounting profile  306 . Furthermore, the first mount  402  and the second mount  402  may be different locations on a same mounting structure. For example, the mounting structure can be a pair of annular pads, e.g., rubber or felt rings, that are concentrically located about central axis  308 . The annular pads can extend along mounting profile  306  and can be squeezed toward each other to exert a clamping force on the outer perimeter of diaphragm  304 . 
     When diaphragm  304  is supported by mount(s)  402 , a portion of diaphragm  304  that is radially inward of mounting profile  306  can be positioned between the opposing ring magnets  314 . In an aspect, magnetic flux from the opposing ring magnets  314  is directed into a magnetic gap between the magnets to interact with conductive traces  322 . For example, an innermost trace  404  of conductive traces  322  can extend within the magnetic flux of one or more of the upper magnet  314  or the lower magnet  314 . 
     In an aspect, innermost trace  404  is a trace having a radial spacing from center  312  of diaphragm  304  that is less than the radial spacings of other traces on diaphragm  304 . For example, innermost trace  404  can define an inner diameter or an inner dimension (in the case of a non-circular voicecoil) of the voicecoil circuit carried on diaphragm  304 . Innermost trace  404  can extend around central region  311  of radiating surface  310 , e.g., innermost trace  404  can surround central region  311 . Given that innermost trace  404  is the trace nearest to center  312  of diaphragm  304  and that innermost trace  404  surrounds central region  311 , in an aspect, central region  311  of radiating surface  310  has no conductive traces  322 . That is, no conductive traces  322  are mounted on or within diaphragm  304  over the section of radiating surface  310  corresponding to central region  311 . Accordingly, central region  311  is trace-free. A moving mass of the trace-free region of diaphragm  304  can be less than a trace-carrying region of diaphragm  304 , and thus, radiating surface  310  can move faster and more efficiently than a planar film having conductive traces over a central region. 
     By reference to the description above, it is apparent that magnet  314  defines an acoustic opening  316  through which sound propagates and innermost trace  404  defines a size of central region  311  of radiating surface  310  that generates the sound. By locating one or more of innermost trace  404  or the inner dimension  320  of magnet  314  nearer to the outer perimeter of diaphragm  304 , both the acoustic opening  316  through which sound propagates and the trace-free region of diaphragm  304  can be increased. 
     In an aspect, innermost trace  404  and/or the inner dimension  320  of magnet  314  is located nearer to mounting profile  306  than central axis  308 . For example, a first radial distance  406  between innermost trace  404  and mounting profile  306  can be less than a second radial distance  408  between innermost trace  404  and central axis  308 . Similarly, a radial distance between inner dimension  320  of magnet  314  and mounting profile  306  is less than a radial distance between inner dimension  320  and central axis  308 . 
     A ratio between first radial distance  406  and second radial distance  408  can be varied to control the size of central region  311 . As the ratio decreases (as second radial distance  408  is increased), a radial dimension, e.g., a diameter, of central region  311  increases. Furthermore, as the radial dimension of central region  311  increases, so does the region of diaphragm  304  having no traces. 
     The ratio between first radial distance  406  and second radial distance  408  can also be varied to control the size of acoustic opening  316 . As the ratio decreases, a radial dimension, e.g., a diameter, of acoustic opening  316  increases. Furthermore, as the radial dimension of acoustic opening  316  increases, the port is more open to the passage of sound generated by diaphragm  304 . Accordingly, an area of sound emission can increase. 
     In an aspect, no acoustically opaque structures are located over acoustic opening  316 . For example, an acoustically transparent mesh may extend over acoustic opening  316  (not shown), however, no magnet structures or other acoustically opaque structures are located over the opening. The acoustic radiation path through acoustic opening  316  to the surrounding environment or the ear of user  100  is not disturbed by magnets  314  or structures that carry magnets, and thus, there is less acoustic loading above or below diaphragm  304 . Similarly, the direct radiating design does not have cavities in the radiation path, and thus, no unwanted resonances are generated by planar magnetic driver  106 . Accordingly, planar magnetic driver  106  can emit undistorted and/or undegraded sound to the listener. 
     Referring to  FIG. 5 , a sectional view of a diaphragm supported between a magnet pair of a planar magnetic driver is shown in accordance with an aspect. In cross-section, it can be seen that the upper magnet  314  and the lower magnet  314  are congruent with each other about central axis  308 . In an aspect, the lower magnet  314  extends around central axis  308  concentrically with the upper magnet  314 . Accordingly, the upper magnet  314  can be a ring magnet that is superposed over a lower ring magnet. 
     The pair of magnets are separated by a magnetic gap  502 . Magnetic gap  502  is between the upper magnet and the lower magnet to provide a space through which diaphragm  304  extends. More particularly, diaphragm  304  is within magnetic gap  502  between the upper magnet and the lower magnet, and a cross-section of diaphragm  304  extends radially from central axis  308  to mount  402 . In an aspect, the flat surfaces of diaphragm  304  are parallel to opposing magnet surfaces. For example, an upper surface of diaphragm  304  can be parallel to a lower surface of the upper magnet  314  facing diaphragm  304 , and a lower surface of diaphragm  304  can be parallel to an upper surface of the lower magnet  314  facing diaphragm  304 . Diaphragm  304  can be located midway between the lower surface of the upper magnet  314  and the upper surface of the lower magnet  314 . More particularly, conductive traces  322  on the upper surface and the lower surface of diaphragm  304  can be spaced equidistantly from an opposing magnet face. The equal spacing can improve efficiency of the system by maintaining an equal force between each magnet  314  and respective conductive traces  322  during driver operation. 
     Referring to  FIG. 6 , a sectional view of conductive traces on a diaphragm located within a magnetic flux of a planar magnetic driver is shown in accordance with an aspect. The magnet pair can be poled such that a magnetic flux  602  of each magnet  314  opposes the magnetic flux  602  of the other magnet  314 . For example, magnetic flux  602  of the upper magnet  314  can be directed downward toward diaphragm  304 , and magnetic flux  602  of the lower magnet  314  can be directed upward toward diaphragm  304 . 
     In an aspect, diaphragm  304  is positioned within magnetic gap  502  such that conductive traces  322  on an upper surface  650  and a lower surface  652  extend within a stray flux of the opposing magnets  314 . More particularly, flux lines of magnetic flux  602  can be parallel to upper surface  650  or lower surface  652  of diaphragm  304  when passing through conductive traces  322 . Conductive traces  322  may be concentrated near inner dimension  320  and outer dimension  318  of magnets  314  where the flux lines extend parallel to the diaphragm surface(s). For example, innermost trace  404  on the upper surface  650  may be adjacent to inner dimension  320  of the upper magnet  314 , and conductive traces  322  can include an outermost trace  604  on the upper surface  650  that is adjacent to outer dimension  318  of the upper magnet  314 . Similarly, innermost trace  404  on the lower surface  652  may be adjacent to inner dimension  320  of the lower magnet  314 , and conductive traces  322  can include outermost trace  604  on the lower surface  652  that is adjacent to outer dimension  318  of the lower magnet  314 . Innermost traces  404  on the upper and lower surfaces  650 ,  652  of diaphragm  304  can be congruent, e.g., vertically aligned with each other. Accordingly, innermost trace  404  on the upper surface  650  of diaphragm  304  may be within magnetic flux  602  of the upper magnet  314 , and innermost trace  404  on the lower surface  652  of diaphragm  304  may be within magnetic flux  602  of the lower magnet  314 . 
     Referring to  FIG. 7 , a schematic view of a diaphragm of a planar magnetic driver being driven in a first mode of vibration is shown in accordance with an aspect. When an audio signal is transmitted through conductive traces  322 , the electrical signal current combines with magnetic flux  602  to generate Lorentz forces that drive diaphragm  304 . The driven diaphragm  304  can oscillate in an upward and downward direction to create one or more waves across the diaphragm. For example, when diaphragm  304  is excited in a first mode  702 , a cross-section of diaphragm  304  takes a single, half-sinusoid, wave shape. In three dimensions, diaphragm  304  takes a dome shape having an apex at center  312 . The dome shape may be concentrated in the central region  311  of the diaphragm, e.g., in the non-trace loaded region. The first mode shape of diaphragm  304  includes a first node  704  at the mounting location on mount  402 . In any modal shape of diaphragm  304 , a node point is a point over the cross-section of diaphragm  304  that resides at the rest position, e.g., along a radial plane  750  that extends between the mounting locations and parallel to the diaphragm surfaces when diaphragm  304  is at rest. The half-wave shape of diaphragm  304  in first mode  702  has a single node at mount  402 , and first node  704  does not experience movement relative to the resting plane during diaphragm excitation. 
     In an aspect, mount(s)  402  of speaker driver  106  are revolute joints  706 , and thus, mounts  402  impart a single degree of freedom between diaphragm  304  and carrier  302  at first node  704 . For example, diaphragm  304  can rotate about mount  402  at first node  704 , e.g., about an axis extending into the page in  FIG. 7 . First node  704  can be at mounting profile  306  along the outer perimeter of diaphragm  304  (near an outer dimension or circumference of diaphragm  304 ). Accordingly, as diaphragm  304  rotates about revolute joint  706 , center  312  of diaphragm  304  can move upward and downward along the central axis  308 . 
     Movement of center  312  along central axis  308  during diaphragm excitation is between an upper limit  708  and a lower limit  710 . The distance between the limits is an excursion range  712  of diaphragm  304  along central axis  308 . Given that only a surround region of diaphragm  304  is constrained between magnets  314  (not radiating surface  310  that is radially inward from the surround region), radiating surface  310  can oscillate along a range of motion having peaks higher and lower than the magnet surfaces facing diaphragm  304 . That is, since magnets  314  are spaced substantially apart from central axis  308  in the radial direction, and near mounts  402 , center  312  of diaphragm  304  can extend higher than the lower face of upper magnet  314  (or the upper face of lower magnet  314 ). Vertical movement of the region of diaphragm  304  having conductive traces  322  is constrained by magnets  314 , but center  312  of diaphragm  304  is not. Accordingly, excursion range  712  of the trace-free region of radiating surface  310  can be greater than magnetic gap  502 . More particularly, a gap distance  714  of magnetic gap  502  is less than an excursion range  712  of diaphragm  304  along central axis  308 . 
     It will be appreciated that, by increasing a radial distance between central axis  308  and inner dimension  320  of magnet  314 , excursion range  712  can be further increased for a same conductor movement. This can be understood, for example, with general reference to the law of similar triangles that would provide for a larger vertical leg of a triangle when a horizontal leg of the triangle is increased. Accordingly, locating innermost trace  404  and/or magnet  314  nearer to the outer perimeter of diaphragm  304  will cause a corresponding increase in excursion range  712 . In any case, the deflection of center  312  of diaphragm  304  can exceed the distance between magnets  314 . By maximizing the diaphragm deflection in the axial direction per unit area of diaphragm  304  in the radial direction, diaphragm  304  can displace more air volume in a smaller speaker package, and thus, sound generation of planar magnetic driver  106  can be increased. 
     Referring to  FIG. 8 , a top view of a voicecoil circuit on a diaphragm of a planar magnetic driver is shown in accordance with an aspect. The voice coil circuit on diaphragm  304  can include a continuous electrical trace extending across one or more of the upper surface  650  or the lower surface  652  (not shown) of diaphragm  304  from an input terminal  802  to an output terminal  804 . Upper surface  650  of diaphragm  304  is shown in  FIG. 8 , but it will be appreciated that the voicecoil circuit on upper surface  650  may be replicated on lower surface  652  of diaphragm  304 . For example, a circuit on upper surface  650  may be congruent with a circuit on a lower surface  652  of diaphragm  304 . An audio signal  805  can be applied to input terminal  802  and be transmitted through the voice coil circuit in the direction of the arrows over the diaphragm surfaces to output terminal  804 . 
     The voice coil circuit can include a first winding  806  having outermost trace  604 , and a second winding  808  having innermost trace  404 . The winding can spiral about central axis  308  to carry electrical current in a circular fashion as shown by arrows in  FIG. 8 . The windings can be radially outward of central region  311  of radiating surface  310  such that central region  311  is trace-free. For example, an outer profile  850  of central region  311  can be adjacent to and radially inward of (or defined by) innermost trace  404 . The windings may be electrically connected by one or more winding bridge  809  that extends across an annular gap between the first winding  806  and second winding  808 . Alternatively, the windings may be combined in a single winding spiraling around central axis  308  between outermost trace  604  and innermost trace  404 . As described above, both windings can be farther from center  312  of diaphragm  304  than they are from an outer edge  810  of diaphragm  304  and/or mounting profile  306  of mounts  402 . For example, first winding  806  can overlap in a vertical direction with outer dimension  318  of magnet  314 , and second winding  808  can overlap in the vertical direction with inner dimension  320  of magnet  314 . Accordingly, outermost trace  604  can be located within magnetic flux  602  of magnet  314  near outer dimension  318 , and innermost trace  404  can be located within magnetic flux  602  of magnet  314  near inner dimension  320 . 
     Referring to  FIG. 9 , a pictorial view of a voicecoil-loaded diaphragm being moved by a Lorentz force is shown in accordance with an aspect. Audio signal  805  can include electrical current passing through conductive traces  322  on upper surface  650  and lower surface  652  of diaphragm  304 . In an aspect, conductive traces  322  on upper surface  650  can be electrically coupled to conductive traces  322  on lower surface  652 . For example, both conductive traces  322  can connect to input terminal  802  and extend to output terminal  804  electrically in parallel. Alternatively, conductive traces  322  on upper surface  650  can be electrically in series with conductive traces  322  on lower surface  652 . For example, the voice coil circuit can include one or more vias  904  extending through diaphragm  304  from the conductive trace  322  on upper surface  650  to the conductive trace  322  on lower surface  652 . In either case, innermost trace  404  on upper surface  650  can be electrically coupled to innermost trace  404  on lower surface  652 . 
     Conductive traces  322  are shown having audio signal  805  running into the page through second winding  808  having innermost traces  404  and out of the page through first winding  806  having outermost traces  604 . The direction of current flow can be combined with a direction of magnetic flux  602  of magnets  314  to determine a direction of a Lorentz force  906 . For example, the illustrated direction of current flow in both innermost trace  404  and outermost trace  604  will generate a downward force  906  on diaphragm  304  according to the right-hand rule. Conversely, when the direction of current flow is reversed relative to the illustration, an upward force  906  on diaphragm  304  is generated to move diaphragm  304  upward. Accordingly, audio signal  805  can be controlled to move radiating surface  310  upward and downward to generate sound. 
     Diaphragm  304  is shown having a uniform thickness, however, it will be appreciated that a thickness of diaphragm  304  may be nonuniform. For example, a thickness of diaphragm  304  across central region  311  of radiating surface  310  may be greater or less than a thickness of diaphragm  304  between the outer profile of central region  311  and outer edge  810 . The thicknesses can be controlled to tune movement of diaphragm  304 . For example, by thinning central region  311 , the surface may deflect more than the outer region of diaphragm  304  during speaker operation, which may result in central region  311  taking on a larger dome shape and displacing more air volume as compared to a uniform thickness diaphragm  304 . Other tuning features can be implemented in diaphragm  304 . For example, one or more weights can be mounted on diaphragm  304  at predetermined locations, e.g., at center  312  or along the outer profile of central region  311 . The weights can be more dense than the diaphragm material to affect the displacement of the loaded region. The tuning features can alter the movement of diaphragm  304  during speaker operation to achieve a desired speaker output. 
     Referring to  FIG. 10 , a pictorial view of a diaphragm mounted on a revolute joint of a planar magnetic driver is shown in accordance with an aspect. As described above, diaphragm  304  can be mounted on carrier  302  by revolute joints  706 . The revolute joints  706  can provide more compliance to diaphragm  304  at the mounting locations as compared to other modes of joining diaphragm  304  to carrier  302 , e.g., a glue joint. More particularly, whereas a glue joint would fix diaphragm  304  to carrier  302 , revolute joints  706  provide a degree of freedom between diaphragm  304  and carrier  302 . Accordingly, revolute joints  706  can lower the resonance frequency of diaphragm  304 . 
     In an aspect, diaphragm  304  is clamped around mounting profile  306 . For example, diaphragm  304  can be clamped between two compliant elements of mount  402 . More particularly, Mount  402  may include a first compliant element and a second compliant element having respective faces that contact diaphragm  304 . The elements can be pads. Diaphragm  304  can be mounted between first compliant pad  1002  and second compliant pad  1004 , and pressure may be applied to diaphragm  304  by the pads to squeeze and clamp diaphragm  304  at the mounting location. The pressure may be applied by upper and lower portions of carrier  302  that are bolted together to press the compliant pads against diaphragm  304 . The compliant pads can be formed from a compliant material, such as an elastomer or a felt material. Accordingly, when diaphragm  304  is excited to move center  312  along central axis  308 , diaphragm  304  can rock back and forth within mount  402  and outer edge  810  of diaphragm  304  can move upward and downward. The rocking motion of diaphragm  304  at the mounting location is substantially rotational movement, e.g., tilting, and represents a degree of freedom between diaphragm  304  and carrier  302 . Accordingly, the resonance frequency of diaphragm  304  is lowered, and diaphragm  304  can be more easily excited into first mode  702 , and higher modes of resonance. 
     Referring to  FIG. 11 , a schematic view of a diaphragm of a planar magnetic driver being driven in a second mode of vibration is shown in accordance with an aspect. Diaphragm  304  can be excited in a second mode  1102 , which is different than first mode  702 . Second mode  1102  can have two nodes, one being first node  704  at mount  402  and a second node  1104  radially inward from first node  704 . Like first node  704 , second node  1104  is a point along the cross-section of diaphragm  304  that resides at the rest plane when diaphragm  304  has the second mode of vibration. In an aspect, second node  1104  is located between central axis  308  and magnet  314  of speaker driver  106 . More particularly, inner dimension  320  of magnets  314  will reside outside of a radius of second node  1104  of diaphragm  304 . Similarly, second node  1104  may be radially between innermost trace  404  on diaphragm  304  and central axis  308 . 
     One or more regions of diaphragm  304  may be visually transparent. In an aspect, central region  311  of radiating surface  310  is visually transparent. For example, diaphragm  304  can be formed from a sheet of transparent polymer material. Given that central region  311  is trace-free, and that no magnetic structures are located above or below central region  311 , forming all or a portion of radiating surface  310 , e.g., central region  311 , from a transparent material can allow user  100  to see through diaphragm  304 . Carrier  302  or other components of planar magnetic driver  106  may also be transparent. Accordingly, speaker driver  106  can be substantially transparent and allow user  100 , for example, to view a display or another object on an opposite side of speaker driver  106  from user  100 . The transparency of diaphragm  304  may also provide a cosmetic benefit when used in certain products, such as when planar driver  106  is mounted in the earcup  108  of headset  104 . 
     To aid the Patent Office and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims or claim elements to invoke 35 U.S.C. 112(f) unless the words “means for” or “step for” are explicitly used in the particular claim. 
     In the foregoing specification, the invention has been described with reference to specific exemplary aspects thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of the invention as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.

Metadata:
Filing Date: 20180927
Publication Date: 20210323
Grant Date: 20210323
Priority Date: 20180927
Inventors: ILKORUR, ONUR I
TIKANDER, MIIKKA O.
WILK, CHRISTOPHER
TOM, BONNIE W.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04R2499/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2209/026", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R9/063", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R9/047", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R7/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/1091", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R7/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R9/06", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R2209/026", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2209/026", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R9/025", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R2499/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R9/047", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2400/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R7/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R1/1091", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R9/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2499/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R7/04", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R9/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R9/063", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R7/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R9/025", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R2209/026", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2499/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R9/063", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 69946796