PATENT DOCUMENT

Publication Number: US-10129652-B2
Application Number: US-201514726288-A
Country: US
Kind Code: B2

Title: Audio speaker surround geometry for improved pistonic motion

Abstract:
An audio speaker having a suspension system including a surround to support a diaphragm within a frame and to reduce non-pistonic motion of the diaphragm at several resonant frequencies is disclosed. More particularly, embodiments of the surround include a film that undulates in a peripheral direction around the diaphragm and includes several undulations above and below a radial gap between the diaphragm and the frame. Other embodiments are also described and claimed.

Claims:
What is claimed is: 
     
       1. A speaker surround, comprising:
 a ring-shaped film having an inner edge radially separated from an outer edge, wherein a radial plane extends through the inner edge and the outer edge, the film including a film surface undulating in a peripheral direction around the inner edge, wherein the film surface includes a plurality of upper undulations above the radial plane and a plurality of lower undulations below the radial plane, wherein the undulations include respective surface boundaries defined by the inner edge, the outer edge, and respective pairs of radial chords extending along the radial plane from the inner edge to the outer edge, and wherein the undulations include respective smooth surface curvatures extending across the respective surface boundaries. 
 
     
     
       2. The speaker surround of  claim 1 , wherein the plurality of upper undulations comprise an upper undulation having an upper surface curvature defined by an upper peripheral chord intersecting an upper radial chord at an upper apex above the radial plane, and wherein the plurality of lower undulations comprise a lower undulation having a lower surface curvature defined by a lower peripheral chord intersecting a lower radial chord at a lower apex below the radial plane. 
     
     
       3. The speaker surround of  claim 2 , wherein the upper peripheral chord is contiguous with the lower peripheral chord such that the upper undulation and the lower undulation are arranged sequentially in the peripheral direction. 
     
     
       4. The speaker surround of  claim 3 , wherein the respective surface boundaries of the sequentially arranged upper and lower undulations are defined by a shared radial chord such that the sequentially arranged undulations are contiguous in the peripheral direction. 
     
     
       5. The speaker surround of  claim 4 , wherein the shared radial chord is a straight line segment extending along the radial plane. 
     
     
       6. The speaker surround of  claim 4 , wherein the shared radial chord is a curvilinear line segment extending along the radial plane. 
     
     
       7. A speaker surround, comprising:
 a ring-shaped film having an inner edge radially separated from an outer edge, wherein a radial plane extends through the inner edge and the outer edge, an intermediate line extending in a peripheral direction along the radial plane between the inner edge and the outer edge, the film undulating in the peripheral direction around the inner edge, wherein the film includes a repeating surround segment having a surface boundary defined by the inner edge, the outer edge, and a pair of radial chords extending along the radial plane from the inner edge to the outer edge and intersecting the intermediate line, and wherein the repeating surround segment includes an upper undulation above the radial plane and a lower undulation below the radial plane, the upper undulation and the lower undulation having respective smooth surface curvatures extending across the surface boundary. 
 
     
     
       8. The speaker surround of  claim 7 , wherein the repeating surround segment includes the upper undulation and the lower undulation, and wherein the upper undulation and the lower undulation are radially separated by the intermediate line. 
     
     
       9. The speaker surround of  claim 8 , wherein the upper undulation includes an upper surface curvature defined by an upper peripheral chord intersecting an upper radial chord at an upper apex above the radial plane, and wherein the lower undulation includes a lower surface curvature defined by a lower peripheral chord intersecting a lower radial chord at a lower apex below the radial plane. 
     
     
       10. The speaker surround of  claim 9 , wherein the upper peripheral chord of the upper undulation and the lower peripheral chord of the lower undulation are on opposite sides of the intermediate line such that the upper apex of the upper undulation and lower apex of the lower undulation are not aligned along a same peripheral chord. 
     
     
       11. The speaker surround of  claim 10 , wherein the upper surface curvature and the lower surface curvature intersect along the intermediate line such that the upper undulation and the lower undulation provide a contiguous smooth surface curvature extending across the surface boundary of the repeating surround segment. 
     
     
       12. The speaker surround of  claim 11 , further comprising a second repeating surround segment having a second surface boundary around a second upper undulation and a second lower undulation, the second upper undulation having a second upper peripheral chord contiguous with the upper peripheral chord of the upper undulation and the second lower undulation having a second lower peripheral chord contiguous with the lower peripheral chord of the lower undulation such that the repeating surround segment is arranged sequentially with the second repeating surround segment in the peripheral direction. 
     
     
       13. The speaker surround of  claim 12 , wherein the respective surface boundaries of the sequentially arranged repeating surround segment and second repeating surround segment are defined by a shared radial chord such that the repeating surround segments are contiguous in the peripheral direction. 
     
     
       14. The speaker surround of  claim 13 , wherein the shared radial chord is a curvilinear line segment extending from the inner edge to the outer edge. 
     
     
       15. The speaker surround of  claim 14 , wherein the shared radial chord intersects the intermediate line at an inflection point of the shared radial chord. 
     
     
       16. The speaker surround of  claim 15 , wherein the shared radial chord is a sinusoidal line segment extending from the inner edge to the outer edge and having the inflection point at a median point along the radial plane. 
     
     
       17. An audio speaker, comprising:
 a frame having an inner rim; 
 a diaphragm along a central axis, the diaphragm having an outer rim separated from the inner rim by a radial gap around the outer rim; and 
 a surround having a ring-shaped film undulating in a peripheral direction around the outer rim, the film including a plurality of surround segments, each surround segment having a respective surface boundary defined by an inner edge attached to the outer rim, an outer edge attached to the inner rim, and a respective pair of radial chords extending along a radial plane from the inner edge to the outer edge, wherein the plurality of surround segments include one or more upper undulations above the radial gap and one or more lower undulations below the radial gap, the undulations having respective smooth surface curvatures extending across the respective surface boundary. 
 
     
     
       18. The audio speaker of  claim 17 , wherein the audio speaker is a single suspension audio speaker having the surround and no spider, wherein the outer rim of the diaphragm has one or more sides, and wherein the undulations of the surround extend continuously along all of the one or more sides. 
     
     
       19. The audio speaker of  claim 18  further comprising a driving element coupled with the diaphragm to drive the diaphragm at a plurality of resonant frequencies such that the diaphragm and the driving element move within an axial degree of freedom and one or more non-axial degrees of freedom at each resonant frequency, wherein the undulating film of the surround maintains participation in the axial degree of freedom to not less than within one order of magnitude of participation in each non-axial degree of freedom at each resonant frequency. 
     
     
       20. The audio speaker of  claim 19 , wherein the outer rim includes a plurality of corner regions, wherein the undulations of the surround extend continuously between the plurality of corner regions, and wherein the undulating film does not include an upper undulation or a lower undulation along the plurality of corner regions. 
     
     
       21. A speaker surround, comprising:
 a ring-shaped film having an inner edge radially separated from an outer edge, wherein a radial plane extends through the inner edge and the outer edge, wherein the ring-shaped film includes a film surface undulating in a peripheral direction around the inner edge, wherein the film surface includes a plurality of upper undulations and a plurality of lower undulations, each upper undulation including an upper apex above the radial plane when the speaker surround is in a neutral position, each lower undulation including a lower apex below the radial plane when the speaker surround is in the neutral position, and wherein the plurality of upper undulations and the plurality of lower undulations include respective surface boundaries defined by the inner edge, the outer edge, and respective pairs of radial chords extending along the radial plane from the inner edge to the outer edge.

Description:
This application claims the benefit of U.S. Provisional Patent Application No. 62/049,990, filed Sep. 12, 2014, and this application hereby incorporates herein by reference that provisional patent application. 
    
    
     BACKGROUND 
     Field 
     Embodiments related to audio speakers and audio speaker suspension systems are disclosed. More particularly, an embodiment related to an audio speaker surround having a film that undulates in a peripheral direction around a speaker diaphragm, is disclosed. 
     Background Information 
     An audio speaker, such as a loudspeaker, converts an electrical audio input signal into an emitted sound. Audio speakers typically include a moving assembly that is connected to a stationary assembly by a suspension system. The moving assembly may include a diaphragm connected with a driving element, e.g., one of either a voicecoil or a magnet, while the stationary assembly may include a frame and a complementary driving element, e.g., the other of the voicecoil or the magnet. The suspension system typically includes elements that keep the moving assembly centered relative to the stationary assembly. For example, a surround may connect the diaphragm with the frame and/or a spider may connect the driving element with the frame. Thus, when the electrical audio input signal is input to the voicecoil, a mechanical force may be generated that moves the moving assembly from a neutral position in an axial direction relative to the frame. This axial motion is referred to as pistonic motion. The moving assembly may also experience a degree of non-axial motion, i.e., non-pistonic motion. In fact, at certain resonant frequencies, the non-pistonic modes of motion, i.e., the “racing modes,” may tend to dominate pistonic motion. The non-pistonic motion in these racing modes may cause the voicecoil to stretch and/or rub against the magnet, and over time, this can lead to issues with the emitted sound quality or cause failure of the audio speaker. 
     SUMMARY 
     Audio speakers having a suspension system including a surround to support a diaphragm within a frame and to reduce non-pistonic motion of the diaphragm at several resonant frequencies, are disclosed. In an embodiment, an audio speaker includes a frame having an inner rim, a diaphragm having an outer rim separated from the inner rim by a radial gap, and a surround supporting the diaphragm relative to the frame. The audio speaker may be a single-suspension audio speaker, i.e., may include the surround but no spider. The speaker surround may include a film, e.g., an elastic film, which undulates in a peripheral direction along the radial gap around the outer rim. More particularly, the film may include several surround segments with respective surface boundaries surrounding one or more undulations. The respective surface boundaries may be defined by an inner edge of the film attached to the outer rim, an outer edge of the film attached to the inner rim, and respective pairs of radial line segments extending from the inner edge to the outer edge, e.g., across or along the radial gap. The undulation(s) within a respective surface boundary may include an upper undulation disposed above the radial gap and/or a lower undulation disposed below the radial gap. Each undulation may have a respective smooth surface curvature extending across the respective surface boundary. Furthermore, in an example, in addition to portions of the surround having the surround segments, the surround may extend along a corner region of the outer rim, and the undulating film may have no undulations along the corner region. As such, stresses may concentrate in the undulations along the outer rim sides (non-corner regions) to control and limit non-pistonic motion, rather than being concentrated along the corner regions, which could exacerbate non-pistonic motion. Accordingly, the audio speaker may include a driving element coupled with the diaphragm to drive the diaphragm at several resonant frequencies such that the diaphragm and the driving element move within an axial degree of freedom and one or more non-axial degrees of freedom at each resonant frequency, and the undulating film of the surround may maintain participation in the axial degree of freedom to not less than within one order of magnitude of participation in each non-axial degree of freedom at each resonant frequency. 
     In an embodiment, a speaker surround includes a film with an inner edge separated from an outer edge along a radial plane, and the film may have an undulating film surface that includes several upper undulations above the radial gap and several lower undulations below the radial gap. The upper undulations and lower undulations may have respective surface boundaries and the undulations may also include respective smooth surface curvatures extending across the boundaries. For example, the smooth curvatures may be partly defined by respective peripheral chords intersecting respective radial chords at respective curvature apices. The respective peripheral chords of different undulation curvatures may be contiguous with each other, e.g., a peripheral chord of an upper undulation may be contiguous with a peripheral chord of a lower undulation such that the upper undulation and lower undulation are sequentially arranged in the peripheral direction around the outer rim of the diaphragm. Furthermore, in an embodiment, respective surface boundaries of the sequentially arranged upper and lower undulations may share a radial line segment such that the undulations are contiguous, e.g., immediately adjacent to each other, in the peripheral direction. The shared radial line segment may be a straight line extending across the radial gap, or alternatively, the shared radial line segment may be a curvilinear line extending across the radial gap. Thus, the undulations may be side-by-side in a peripheral direction, but not side-by-side in a radial direction. 
     In an embodiment, a speaker surround includes a film with an inner edge separated from an outer edge along a radial plane, and the film may have an undulating film surface that includes a repeating surround segment. The repeating surround segment may be repeated in a peripheral direction along the film. The repeating surround segment may include a surface boundary defined by the inner edge and the outer edge of the speaker surround, as well as a respective pair of radial line segments extending from the inner edge to the outer edge. Furthermore, the repeating surround segment may undulate in the peripheral direction along an intermediate line disposed between the inner edge and the outer edge, and thus, the radial line segments may intersect the intermediate line. The repeating surround segment may include one or more of an upper undulation above the radial gap or a lower undulation below the radial gap, and the upper undulation and lower undulation, if present, may have respective smooth surface curvatures extending across the surface boundary. For example, in an embodiment, the repeating surround segment includes both an upper undulation and a lower undulation. In such a case, the upper undulation and the lower undulation may be radially separated by the intermediate line, e.g., the upper undulation and the lower undulation may have respective smooth surface curvatures that intersect at the intermediate line. As such, the upper undulation may include a respective peripheral chord on an opposite side of the intermediate line relative to a respective peripheral chord of the lower undulation. Thus, an upper apex of the upper undulation may not be aligned along a same peripheral chord with a lower apex of the lower undulation, i.e., the apices may be radially offset. The upper undulation and the lower undulation may nonetheless provide a contiguous surface curvature extending across the surface boundary of the repeating surround segment, i.e., the repeating surround segment may include a continuous smooth surface having portions above and below the radial gap. Thus, the undulations may be side-by-side in a peripheral direction and/or side-by-side in a radial direction. 
     In an embodiment, several repeating surround segments having surface contours with portions above and below a radial plane may be arranged sequentially in the peripheral direction, and may share radial line segments such that the repeating surround segments are contiguous in the peripheral direction. The shared radial line segments of immediately adjacent surround segments may be curvilinear, rather than straight. For example, a shared radial line segment may be a sinusoidal line segment that intersects an intermediate line on the radial plane at a point between an inner edge and an outer edge of the contour. The intersection point of the intermediate line and the radial line segment may be at an inflection point of the radial line segment coinciding with a location where an upper undulation transitions into a lower undulation. 
     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 perspective cutaway view of an audio speaker in accordance with an embodiment. 
         FIG. 2  is a cross-sectional view of a surround in accordance with an embodiment. 
         FIG. 3  is a cross-sectional view of a spider in accordance with an embodiment. 
         FIG. 4  is a schematic view depicting various modes of motion of an audio speaker in accordance with an embodiment. 
         FIG. 5  is a perspective cutaway view of an audio speaker in accordance with an embodiment. 
         FIG. 6  is a cross-sectional view of a portion of an audio speaker having a surround connecting a diaphragm with a frame in accordance with an embodiment. 
         FIG. 7  is a perspective cutaway view, taken from Detail A of  FIG. 5 , of an undulating portion of a surround in accordance with an embodiment. 
         FIGS. 8A-8B  are cross-sectional views, taken about a portion of line A-A of  FIG. 7 , of a surround segment having an upper undulation in accordance with various embodiments. 
         FIG. 9  is a cross-sectional view, taken about a portion of line A-A of  FIG. 7 , of a surround segment having a lower undulation in accordance with an embodiment. 
         FIG. 10  is a cross-sectional view, taken about a portion of line A-A of  FIG. 7 , of a surround segment having an upper undulation in series with a surround segment having a lower undulation in accordance with an embodiment. 
         FIG. 11  is a cross-sectional view, taken about line B-B of  FIG. 7 , of a surround segment having an upper undulation in accordance with an embodiment. 
         FIG. 12  is a perspective cutaway view, taken from Detail A of  FIG. 5 , of an undulating portion of a surround in accordance with an embodiment. 
         FIG. 13  is a cross-sectional view, taken about line C-C of  FIG. 12 , of a surround segment having an upper undulation separated from a surround segment having a lower undulation by an intermediate section in accordance with an embodiment. 
         FIGS. 14A-14B  are perspective cutaway views of a corner region of a surround in accordance with various embodiments. 
         FIG. 15  is a perspective view of an audio speaker surround in accordance with an embodiment. 
         FIG. 16  is a perspective cutaway view, taken from Detail B of  FIG. 15 , of a repeating surround segment having an upper undulation and a lower undulation in accordance with an embodiment. 
         FIGS. 17A-17C  are cross-sectional views, taken about lines D-D, E-E, and F-F of  FIG. 16 , of a repeating surround segment having an upper undulation and a lower undulation in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments describe suspension systems having an undulating film to reduce non-pistonic motion of an oscillating mass at several resonant frequencies, particularly for use in audio speaker applications. While some embodiments are described with specific regard to integration within single-suspension audio speakers, the embodiments are not so limited and certain embodiments may also be applicable to audio speakers having two or more suspenders. Furthermore, a surround as described below may be applicable to other uses, e.g., non-acoustic applications having a moving assembly driven at various resonant frequencies for which non-pistonic motion is undesirable. 
     In various embodiments, description is made with reference to the figures. Certain embodiments, however, 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 embodiments. 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 embodiment,” “an embodiment,” or the like, means that a particular feature, structure, configuration, or characteristic described is included in at least one embodiment. Thus, the appearance of the phrase “one embodiment,” “an embodiment,” or the like, in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more embodiments. 
     The use of relative terms throughout the description, such as “above” and “below” may denote a relative position or direction. For example, an undulation may be described as being “above” a radial gap to indicate that the undulation may be located on one side of a geometric plane extending through the radial gap, while an undulation may be described as being “below” the radial gap to indicate that the undulation may be located on the other side of the geometric plane. Nonetheless, such terms are not intended to limit the use of an audio speaker to a specific configuration described in the various embodiments below. For example, an audio speaker having a surround with an undulation “above” a certain location may nonetheless be directed in any direction with respect to an external environment, including such that the undulation is directed toward the ground. 
     In an aspect, a speaker surround includes a film that undulates around a perimeter of a speaker diaphragm such that a combination of upper undulations above a radial gap and lower undulations below the radial gap support the diaphragm within a speaker frame. For example, a sequence of repeating upper undulations spaced apart by repeating lower undulations may support the diaphragm within the speaker frame. Thus, loads applied by the moving diaphragm may be distributed within the undulations in a complementary manner, i.e., upper undulations may be placed in tension while lower undulations are placed in compression, and vice versa. Such complementary stress distribution can control and/or limit non-pistonic motion, e.g., racing modes, of a moving assembly of the audio speaker at certain resonant frequencies. For example, participation of the moving assembly in the non-pistonic modes may be reduced as compared to participation by the moving assembly in those modes when supported by a traditional half-arc, non-undulating speaker surround. Therefore, an undulating surround film as described below may prevent rub and buzz, sound distortion, and speaker failure issues that can arise with traditional speaker surrounds. 
     In an aspect, an undulating speaker surround provides a low-cost solution to the racing mode issues described above. Since racing modes typically occur at only a few resonant frequencies within the range of frequencies used during sound reproduction, the frequency response of an audio speaker may be electronically adjusted around those frequencies to mitigate rub and buzz issues. Such electronic compensation, however, may be relatively complex and costly to implement in a media player used to control the audio speaker. Furthermore, since the racing mode frequencies may change based on thermal considerations and speaker aging, electronic compensation may be ineffective as temperatures change or the audio speaker is used over time. By contrast, an undulating speaker surround as described below may be manufactured using low-cost manufacturing techniques, such as thermoforming, and once fabricated, may limit rocking of the diaphragm within racing modes at any resonant frequency, regardless of whether the resonant frequency shifts due to time or temperature changes. 
     Referring to  FIG. 1 , a perspective cutaway view of an audio speaker is shown in accordance with an embodiment. An audio speaker  100 , such as a micro speaker or loudspeaker, may include a frame  102 , such as a stationary and/or rigid chassis or basket. Frame  102  may be connected to a stationary portion of a motor assembly, such as magnet  104 . Thus, the rigidity of frame  102  may maintain the stationary portion in a fixed location, to avoid deformation or movement that can cause rubbing with a moving portion of the motor assembly. Magnet  104  may have an annular shape with a central opening to receive and surround the moving portion of the motor assembly. More particularly, a voicecoil  106  may be suspended within the annulus of magnet  104  and be movable relative to magnet  104  within a magnetic gap between the magnet  104  and voicecoil  106 . When an electrical audio signal is input to voicecoil  106 , e.g., from a media player or other audio equipment, a magnetic field may be created by an electric current in a wire winding, e.g., copper, aluminum, or silver wire, of the voicecoil  106 . The magnetic field may interact with magnet  104  across the magnetic gap to generate a mechanical force that moves the voicecoil  106  back and forth. More particularly, voicecoil  106  may be connected to a lower region of a diaphragm  108 , and thus, the electrical audio signal may generate a mechanical force that moves the diaphragm  108  back and forth along an axis that passes through the center of voicecoil  106  and/or magnet  104 . This rapid pistonic movement can create pressure waves that are heard as sounds. To maximize magnetic energy in the magnetic gap, the voicecoil  106  and magnet  104  may be located as close to one another as possible, without touching. More particularly, contact between voicecoil  106  and magnet  104  may be avoided during sound reproduction to avoid speaker failure and/or sound distortion. Accordingly, maximizing pistonic motion and minimizing non-pistonic motion of voicecoil  106  and/or magnet  104  across the range of drive frequencies may be desirable in audio speaker  100 . 
     Diaphragm  108  may have a concave upper profile, such as a cone or dome, and be formed from a rigid, low-mass material, e.g., plastic or metal. Diaphragm  108  may be concentrically supported within frame  102  with a gap between an outer rim of diaphragm  108  and an inner rim of frame  102 . The outer rim of diaphragm  108  may be any of several shapes, including circular, as shown in  FIG. 1 , or rectangular, as is described below and may be commonly found in micro speakers. In an embodiment, the outer rim of diaphragm  108  and the inner rim of frame  102  may include conforming shapes, e.g., both may be circular or both may be rectangular. In other embodiments, the profiles may differ, e.g., a circular diaphragm rim may be coaxially arranged with a rectangular frame rim. Thus, audio speaker  100  may have a moving assembly that includes diaphragm  108  connected with voicecoil  106 , and a stationary assembly that includes frame  102  connected with magnet  104 . Furthermore, the moving assembly may be concentrically supported and/or suspended relative to the stationary assembly by a suspension system that facilitates pistonic movement of the moving assembly. 
     In an embodiment, the suspension system centers voicecoil  106  within the magnetic annulus of magnet  104  and may also provide a restoring force that biases diaphragm  108  toward a neutral position in a direction opposite to the mechanical force that moves the diaphragm  108  back and forth. The suspension system may be a single-suspension system or a double-suspension system. For example, in an embodiment, the suspension system is a single-suspension system having a surround  110  to support diaphragm  108  within frame  102  without the aid of a spider  112 . Alternatively, the suspension system may be a double-suspension system having spider  112 , in addition to surround  110 , to support voicecoil  106  relative to frame  102  and/or magnet  104 , as shown in  FIG. 1 . 
     Referring to  FIG. 2 , a cross-sectional view of a surround is shown in accordance with an embodiment. Surround  110  may include an inner edge  202  that may be connected and/or attached to an outer rim of diaphragm  108 , as well as an outer edge  204  that may be connected and/or attached to an inner rim of frame  102 . For example, the respective edges of surround  110  may be bonded to a respective bonding site using, e.g., chemical adhesives such as glues, thermal welding, or mechanical fasteners. In an embodiment, surround  110  includes a thin membrane or film extending between inner edge  202  and outer edge  204 . The film may be shaped to facilitate relative movement between inner edge  202  and outer edge  204 . For example, in an embodiment, at least some portion of the film may have a half-arc  206 . That is, surround  110  may include a cross-sectional profile having a curvilinear shape extending between inner edge  202  and outer edge  204  in an arched manner. The arc may be above a plane extending through inner edge  202  and outer edge  204 , the plane being normal to a direction of pistonic motion of diaphragm  108 . Furthermore, the arc may be uniform in a peripheral direction around diaphragm  108 , i.e., may have no undulations in the peripheral direction. Accordingly, the half-arc  206  of surround  110  may allow free pistonic motion of diaphragm  108 . 
     Referring to  FIG. 3 , a cross-sectional view of a spider is shown in accordance with an embodiment. Spider  112  may include inner edge  302  and outer edge  304 , which may be bonded to respective bonding sites on, e.g., voicecoil  106  or diaphragm  108  at inner edge  302  and frame  102  or magnet  104  at outer edge  304 . In an embodiment, spider  112  includes a thin membrane or film extending between inner edge  302  and outer edge  304 . For example, in an embodiment, at least some portion of the film may have one or more corrugations  306 . That is, spider  112  may include a cross-sectional profile having several wrinkles or folds alternating between peaks and valleys from inner edge  302  to outer edge  304 . The wrinkles may be above a plane extending through inner edge  302  and outer edge  304 , the plane being normal to a direction of pistonic motion of diaphragm  108 . Furthermore, the wrinkles may be uniform in a peripheral direction, i.e., may have no undulations in the peripheral direction. The corrugations  306  of spider  112  may provide a restoring force to return diaphragm  108  to the neutral position in the axial direction. 
     Any suspension element of the suspension system may include portions having half-arc  206  or corrugation  306  profiles. For example, surround  110  may support a perimeter of diaphragm  108 , and thus, some portions of surround  110  in the peripheral direction, i.e., along the perimeter, may incorporate a half-arc profile  206  while other portions of surround  110  in the peripheral direction may incorporate a corrugated profile  306 . Accordingly, surround  110  or spider  112  may incorporate a combination of segments having different film structures that respond differently to various modes of motion of the moving assembly of audio speaker  100 . 
     Referring to  FIG. 4 , a schematic view depicting various modes of motion of an audio speaker is shown in accordance with an embodiment. Audio speaker  100  may include a driven mass  402 , which may be the total mass of diaphragm  108 , voicecoil  106 , and any other portion of the moving assembly of audio speaker  100 . For example, moving assembly may include a bobbin that voicecoil  106  windings are wound around, a mechanical coupling or fastener that connects voicecoil  106  with diaphragm  108 , or other moving parts that contribute to driven mass  402 . When acted upon by the mechanical force generated by magnet  104  and voicecoil  106 , the driven mass  402  may oscillate along a central axis  404  within an axial degree of freedom, i.e., with pistonic motion  406 . Driven mass  402 , however, may also participate within other degrees of freedom, e.g., may move in non-pistonic modes, such as rocking about central axis  404  with a tipping motion  408  about an axis orthogonal to central axis  404 , or rocking about central axis  404  with a tilting motion  410  about another axis orthogonal to central axis  404 . Participation in any of these pistonic and non-pistonic modes may be influenced by the suspension system response at various resonant frequencies. For example, portions of surround  110  having half-arc  206  profile may suspend driven mass  402  such that, at a first eigenfrequency, driven mass  402  may have a participation factor in the pistonic motion  406  mode that is at least four orders of magnitude higher than a participation factor in either of the tipping motion  408  or tilting motion  410  non-pistonic modes. The half-arc  206  profile sections, however, may have a tendency to dissipate vibration energy with out-of-plane motions at higher eigenfrequencies. For example, in the case of a single-suspension system with surround  110  having half-arc  206  profile around the entire perimeter of diaphragm  108 , at subsequent eigenfrequencies, non-pistonic motion may dominate, with the participation factor in the pistonic mode being at least two orders of magnitude lower than the participation factors in the non-pistonic modes. Thus, rubbing between voicecoil  106  and magnet  104  may become an issue at these higher eigenfrequencies. Accordingly, it may be advantageous to reduce the tendency of driven mass  402  toward non-pistonic motion at these frequencies, or across the entire driving frequency range. 
     Referring to  FIG. 5 , a perspective cutaway view of an audio speaker is shown in accordance with an embodiment. In an embodiment, audio speaker  100  includes a suspension system, e.g., a single-suspension system, having surround  110  connecting diaphragm  108  with frame  102 . As described above, diaphragm  108  may include a rigid member having circular, rectangular, or any other shaped outer rim  502 . Furthermore, frame  102  may include an inner rim  504  shaped similar to outer rim  502 . Inner rim  504  and outer rim  502  may be radially separated. Thus, surround  110  may be connected to both outer rim  502  and inner rim  504  to provide a suspension between diaphragm  108  and frame  102 . Accordingly, surround  110  may be an essentially circular, rectangular, or other ring-shaped structure filling a gap between outer rim  502  and inner rim  504 . 
     As described above, surround  110  may have a film  506  including a thin flexible sheet formed between outer rim  502  and inner rim  504 . For example, film  506  may extend between inner edge  202  and outer edge  204  across the gap between diaphragm  108  and frame  102  and have a cross-sectional profile of half-arc  206  or corrugated profile  306 . The half-arc or corrugated profile, as well as any other cross-sectional profile, may be uniform in a peripheral direction over a portion of surround  110 . For example, as shown in  FIG. 1 , surround  110  may have a half-arc  206  cross-sectional profile that is uniform along an entire perimeter of diaphragm  108 , e.g., in a circumferential direction around a circular diaphragm  108 . Alternatively, as shown in  FIG. 5 , only a portion of surround  110 , e.g., a corner  507  section of a rectangular surround, may include a uniform cross-sectional profile in the peripheral direction. Thus, all or part of film  506  may have a uniform and non-undulating cross-sectional profile in the peripheral direction. 
     In an embodiment, at least a portion of surround  110  does not have a uniform cross-sectional profile in the peripheral direction. Film  506  may undulate in the peripheral direction such that cross-sections of film  506  taken immediately adjacent to one another are not identical. Accordingly, film  506  may include several undulating surround segments  508  that are periodically and/or sequentially arranged in the peripheral direction around at least a portion of outer rim  502 . 
     Film  506  portions, including those with uniform cross-sectional profiles and non-uniform cross-sectional profiles in the peripheral direction, may be thin and flexible. For example, film  506  may be formed from a thin elastic material, such as soft rubber or another elastomeric material. Film  506  may be single-layered or multi-layered, e.g., film  506  may include laminated layers of one or more flexible materials. Furthermore, film  506  may be fabricated from such materials using a variety of manufacturing techniques. In an embodiment, surround  110  and/or film  506  are thermoformed using thermoplastic polyurethane. Given that film  506  may be formed from a thin elastic material, in an embodiment, surround  110  may provide minimal resistance to movement of diaphragm  108  in the axial direction. 
     Referring to  FIG. 6 , a cross-sectional view of a portion of an audio speaker having a surround connecting a diaphragm with a frame is shown in accordance with an embodiment. Diaphragm  108  may be symmetric about central axis  404  such that the concave surface extends from central axis  404  to outer rim  502  in all radial directions. The term “radial direction” is used here to describe a direction radiating from central axis  404  toward outer rim  502  of diaphragm  108  and/or inner rim  504  of frame  102 . Thus, a radial direction may apply equally to circular and non-circular, e.g., rectangular, diaphragm  108  configurations. Furthermore, the radial direction may, but need not, be along an axis orthogonal to central axis  404 . For example, a radial plane  602  may intersect central axis  404  and pass in a radial direction along an angled axis passing through outer rim  502  and inner rim  504 , even when outer rim  502  and inner rim  504  are not at the same longitudinal position, or height, along central axis  404 . As such, film  506  of surround  110  may have a cross-sectional profile that extends between inner edge  202 , which may be connected to outer rim  502 , and outer edge  204 , which may be connected to inner rim  504 , in the radial direction. More particularly, film  506  may extend across a radial gap  604  between outer rim  502  and inner rim  504 , and radial gap  604  may have a distance along radial plane  602  in the radial direction. Accordingly, film  506  may provide a hermetic barrier between a space above radial plane  602  and a space below radial plane  602  across radial gap  604 . The hermetic barrier may be provided by hermetically sealing inner edge  202  to outer rim  502  and outer edge  204  to inner rim  504  using adhesive or welding, as is known in the art. 
     As described above, surround  110  may include several surround segments  508 , and in an embodiment, these surround segments  508  may be further described as including one or more upper undulation  606  and/or one or more lower undulation  608 . Upper undulations  606  may be formed in film  506  above radial gap  604 , e.g., on a front side of radial plane  602  along which radial gap  604  lies between outer rim  502  and inner rim  504 . Similarly, lower undulations  608  may be formed in film  506  below radial gap  604 , e.g., on a rear side of radial plane  602 . Thus, regardless of a location in the peripheral direction (into the page through radial gap  604  in  FIG. 6 ) at which a cross-sectional view is taken, upper undulation  606  and lower undulation  608  may have cross-sectional profiles that extend between inner edge  202  and outer edge  204  on a respective side of radial gap  604 . In an embodiment, surround segments  508  of surround  110  may be formed on opposite sides of radial gap  604 , may be separated in the peripheral direction, and may meet at an intermediate location that extends radially between outer rim  502  and inner rim  504 . For example, as shown in  FIG. 6 , at least one cross-sectional profile of film  506  may be aligned radially along radial plane  602  across radial gap  604 . That is, as described below, film  506  may have a cross-section at one or more locations that includes a radially disposed film segment, e.g., a straight line segment within a thickness, across radial gap  604 . This straight line segment may lie between and/or be a merger point between a surround segment  508  having upper undulation  606  and another surround segment  508  having lower undulation  608 . 
     Referring to  FIG. 7 , a perspective cutaway view, taken from Detail A of  FIG. 5 , of an undulating portion of a surround is shown in accordance with an embodiment. Upper undulation  606  of surround  110  may extend across radial gap  604  and project upward above radial gap  604 . More particularly, a surround segment having a single upper undulation  606  may include a surface boundary that is defined between one or more lines that lie on or above radial gap  604  between outer rim  502  and inner rim  504 . For example, a surface boundary of upper undulation  606  may include inner edge  202 , outer edge  204 , and a pair of lines that are separated from each other in the peripheral direction and extend between inner edge  202  and outer edge  204 . Such lines may be, for example, a pair of radial line segments  702  that extend straightly between inner edge  202  and outer edge  204 . Thus, as in the case where inner edge  202  and outer edge  204  extend along straight sides of a rectangular diaphragm  108  and frame  102 , upper undulation  606  may have a surface boundary that is substantially rectangular. Alternatively, as in the case of a circular diaphragm  108  and frame  102 , when inner edge  202  and outer edge  204  are curved with radii matching those of outer rim  502  and inner rim  504 , upper undulation  606  may have a surface boundary that is a segment of an annulus. In any case, the surface boundary may include a straight line extending across radial gap  604 , and thus, may be aligned or coplanar with radial plane  602 . For example, in the case of an audio speaker  100  having a circular diaphragm  108  and a circular frame  102 , the surface boundary lines of surround segments  508  may be coplanar within radial plane  602  and may be defined in part by a pair of radial line segments  702  that intersect at central axis  404 . 
     In an embodiment, with the undulation surface boundary forming a base of a surround segment  508 , upper undulation  606  may project upward above radial gap  604 . Upper undulation  606  may have an upper surface curvature extending across the boundary. For example, the upper surface curvature may be partly defined by a peripheral chord  704  extending between the pair of radial line segments  702  in the peripheral direction, as well as by a radial chord  706  extending between inner edge  202  and outer edge  204  in the radial direction. The chords may partly define a contour of a concave downward surface curvature extending above radial gap  604 . 
     Surround  110  may include a surround segment  508  having a single lower undulation  608  disposed adjacent to the surround segment  508  having upper undulation  606 . More particularly, lower undulation  608  may be immediately adjacent and contiguous with upper undulation  606 , or spaced apart from upper undulation  606  in the peripheral direction. Similar to upper undulation  606 , lower undulation  608  may include a surface boundary that is defined between one or more lines that lie on or below radial gap  604  between outer rim  502  and inner rim  504 . For example, a surface boundary of lower undulation  608  may include inner edge  202 , outer edge  204 , and a pair of lines extending between inner edge  202  and outer edge  204 , e.g., radial line segments  702 . With such a surface boundary forming a base of the surround segment  508  having lower undulation  608 , lower undulation  608  may have a lower surface curvature extending across the boundary. For example, the lower surface may be partly defined by a peripheral chord  704  extending between the pair of radial line segments  702  in the peripheral direction, and a radial chord  706  extending between inner edge  202  and outer edge  204  in the radial direction. The chords may partly define a contour of a concave upward surface extending below radial gap  604 . 
     Peripheral chords  704  and radial chords  706  of upper undulation  606  and lower undulation  608  may be variously shaped, and thus, the contour of upper or lower surfaces of respective undulations may also have a variety of forms. For example, in an embodiment, each of peripheral chord  704  and radial chord  706  may be multi-segmented line segments, e.g., v-shaped, with apices that meet at a common vertex at the center of the projected boundary area. Accordingly, an upper surface of upper undulation  606  or a lower surface of lower undulation  608  may be pyramidal rather than curved. Alternatively, the upper surface of upper undulation  606  and/or lower surface of lower undulation  608  may include a smooth curvature, defined by peripheral chord  704  and radial chord  706  that are smooth curved lines. Thus, the upper surface and/or the lower surface may include contours that are bulbous or cup-like, as shown in  FIG. 7  and described further below. 
     Referring to  FIG. 8A , a cross-sectional view, taken about a portion of line A-A of  FIG. 7 , of a surround segment having an upper undulation is shown in accordance with an embodiment. In an embodiment, a smooth surface curvature of upper undulation  606  includes a smooth curved peripheral chord  704  extending across the boundary between radial line segments  702  spaced apart in the peripheral direction. The peripheral chord  704 , and thus upper undulation  606  along the cross-section, may be located entirely above radial gap  604 . Accordingly, the surround segment  508  having upper undulation  606  may have a concave downward shape with an upper apex  802  located at a peak of the upper surface curvature. More particularly, peripheral chord  704  may have a continuous, arcuate shape that progresses smoothly from either end at radial line segments  702  toward upper apex  802  without any bends, angles, or folds along the path. 
     Referring to  FIG. 8B , a cross-sectional view, taken about a portion of line A-A of  FIG. 7 , of a surround segment having an upper undulation is shown in accordance with an embodiment. In an alternative embodiment, peripheral chord  704  of upper undulation  606  may progress in a stepped manner between radial line segment  702  and upper apex  802 . For example, peripheral chord  704  may have one or more step  804  between radial line segment  702  and upper apex  802 . The peripheral chord  704  may be continuous and smooth along the stepped path, e.g., the path may be curvilinear with discrete bends between steps, or alternatively, the steps  804  may be continuous and non-smooth, i.e., there may be local angulations along a zig-zag path at which points the surface contour of upper undulation  606  may have a corner or fold. Accordingly, the surface contour of the surround segment  508  having upper undulation  606  may be smooth or non-smooth. 
     Referring to  FIG. 9 , a cross-sectional view, taken about a portion of line A-A of  FIG. 7 , of a surround segment having a lower undulation is shown in accordance with an embodiment. In an embodiment, a smooth surface curvature of lower undulation  608  includes a smooth curved peripheral chord  704  extending across the boundary between radial line segments  702  spaced apart in the peripheral direction. The peripheral chord  704 , and thus lower undulation  608  along the cross-section, may be located below radial gap  604 . Accordingly, the surround segment  508  having lower undulation  608  may have a concave upward shape with a lower apex  902  located at a peak (or valley) of the lower surface curvature. More particularly, peripheral chord  704  may have a continuous, arcuate shape that progresses smoothly from either end at radial line segments  702  toward lower apex  902 . 
     Lower undulation  608  may have other contour shapes, such as the curvilinear and/or stepped contour described with respect to upper undulation  606  in  FIG. 8B . Thus, upper undulations  606  and lower undulations  608  may be similarly shaped, but oppositely disposed about radial gap  604 . For example, upper undulations  606 , or chords defining a surface contour of upper undulation  606 , may be symmetric with lower undulation  608 , or chords defining a surface contour of lower undulation  608 , across radial gap  604 . 
     Referring to  FIG. 10 , a cross-sectional view, taken about a portion of line A-A of  FIG. 7 , of a surround segment having an upper undulation in series with a surround segment having a lower undulation is shown in accordance with an embodiment. In an embodiment, upper undulation  606  and lower undulation  608  may not be symmetric across radial gap  604 . Peripheral chord  704  may extend contiguously between radial line segments  702  defining a surface boundary of a surround segment  508  having upper undulation  606 , and may extend further between radial line segments  702  defining a surface boundary of a surround segment  508  having lower undulation  608 . Furthermore, peripheral chord  704  may curve smoothly to upper apex  802  of upper undulation  606  and lower apex  902  of lower undulation  608 . However, in an embodiment, upper apex  802  may be above radial gap  604  by an apical distance, i.e., a height between an undulation apex and radial gap  604 , which is different than an apical distance of lower apex  902  below radial gap  604 . Accordingly, since the apices of upper undulation  606  and lower undulation  608  differ in height relative to radial gap  604 , the undulations include different radii and are asymmetric across radial gap  604 . For example, a bulbous surface contour of upper undulation  606  may be larger, e.g., have a greater average radius, than a bulbous surface contour of lower undulation  608 . 
     Shaping upper undulations  606  and lower undulations  608  to have asymmetric surface contours across radial gap  604  may allow for surround  110  stiffness to be tuned. For example, creating upper undulations  606  with larger radii, e.g., as in the case where upper apical distances are greater than lower apical distances, may result in upper undulations  606  that are less stiff with respect to loading in a particular direction. More particularly, forming surround segments  508  that are asymmetric across radial gap  604  can allow for surround  110  to be tuned to be more resistant to tilting motion  410  in one direction as compared to tilting motion  410  in another direction. Similarly, creating surround segments  508  that differ in geometry in a peripheral direction, e.g., locating surround segments  508  having upper undulations  606  near corners  507  of surround  110  that include larger radii than upper undulations  606  of surround segments  508  farther from corners  507 , may provide for surround  110  that is more or less resistant to tipping or tilting in a particular radial direction, e.g., resists tilting toward diaphragm  108  sides more than tilting toward diaphragm  108  corners. Thus, undulation geometry may vary between upper undulations  606  and lower undulations  608  of different surround segments  508 , as well as between undulations of the same class within surround segments  508 . For example, some surround segments  508  having upper undulations  606  may have apical distances that differ from other upper undulations  606  of other surround segments  508 , and/or respective lower undulations  608  of different surround segments  508  may vary similarly. More particularly, film  506  undulations may be shaped to alter participation of driven mass  402  in a range of different modes of motion. Furthermore, altering contour geometry may alter resonant frequencies of audio speaker  100 . For example, surround  110  having surround segments  508  that include upper undulations  606  with larger average radii than other surround segments  508  that include lower undulations  608  may shift the resonant frequencies of audio speaker  100 , i.e., the eigenfrequencies, upward. Accordingly, undulation geometry may be altered to tune eigenfrequencies such that modes that dissipate vibrational energy in non-pistonic directions tend to occur within frequency ranges that are less commonly generated during popular music reproduction. 
     Referring to  FIG. 11 , a cross-sectional view, taken about line B-B of  FIG. 7 , of a surround segment having an upper undulation of a surround is shown in accordance with an embodiment. In addition to peripheral chord  704  extending between radial line segments  702  in the peripheral direction, a surface contour of upper undulation  606  may be defined by one or more radial chord  706  extending between inner edge  202  and outer edge  204  in a radial direction. Furthermore, radial chord  706  may have a smooth curved geometry, similar to certain embodiments of peripheral chord  704 . Accordingly, in an embodiment, radial chord  706  and peripheral chord  704  may both have smooth curves defining a surface contour with a smooth curvature and upper apex  802  at a location where the peaks of radial chord  706  and peripheral chord  704  meet. Of course, upper undulation  606  may be segmented into numerous radial chords  706  and peripheral chords  704  by taking cross-sections at different locations along the perimeter of outer rim  502  or between inner edge  202  and outer edge  204 , and thus, some radial chords  706  and peripheral chords  704  of upper undulation  606  may not meet at upper apex  802 . Nonetheless, in an embodiment, every radial chord  706  and peripheral chord  704  of a surround segment  508  may meet at a point that is continuous and smooth on each chord, i.e., there may be no point of intersection between chords that is a vertex of an angle in any direction along the upper surface contour of undulation  606 . Alternatively, some regions of the contour may be smooth, e.g., bulbous, while other portions may have folds, e.g., angles or vertices at intersecting surfaces or chords as in the case of a pyramidal surface. 
     It will be appreciated that the description related to the contour geometry of upper undulation  606  may be equally applied to lower undulation  608  of surround  110 . For example, the geometry of upper undulation  606  illustrated in  FIG. 11  may be mirrored across radial gap  604  to illustrate a similar geometry of lower undulation  608 , and thus, upper undulation  606  and lower undulation  608  may be symmetric in a radial direction across radial gap  604 . Alternatively, lower undulation  608  geometry may include radial chord  706  that differs from the radial chord  706  geometry of upper undulation  606 , just as peripheral chord  704  geometry was illustrated as being asymmetric along radial gap  604  in the example of  FIG. 10 . Thus, upper undulation  606  and lower undulation  608  may have some chords that are symmetric across radial gap  604  and other chords that are asymmetric across radial gap  604 . A person of ordinary skill in the art may extrapolate from the surround segment  508  geometries described above to arrive at a variety of different undulation surface contours, shapes, and sizes within the scope of this description. Accordingly, a description of every permutation of surround segment  508  geometry is omitted here for conciseness. Certain embodiments, however, are described below beginning at  FIG. 15  that fit within the general framework described above. Those embodiments are address after  FIGS. 12-14B  to avoid unnecessarily obscuring the additional aspects that are described next. 
     In an embodiment, surround segments  508  of film  506  do not overlap with one another around outer rim  502 . For example, although a surround segment  508  having upper undulation  606  and another surround segment  508  having lower undulation  608  may be adjacent, and in some cases immediately adjacent as shown in  FIG. 7 , the surface boundaries that define upper undulation  606  and lower undulation  608  may not overlap along the peripheral direction. Since the surface boundaries of each surround segment  508  may be defined by those lines around the respective undulation that forms a base of surround segment  508  lying within radial plane  602 , the surface boundaries of nonoverlapping upper undulation  606  and lower undulation  608  may not both be intersected by the same straight radial line segment extending between inner edge  202  and outer edge  204 . More particularly, whereas the radial line segments  702  defining upper undulation  606  and lower undulation  608  may include a same radial line segment  702 , such as the middle radial line segment  702  shown between immediately adjacent upper undulation  606  and lower undulation  608  in  FIG. 7 , no portion of upper undulation  606  lies on the lower undulation  608  side of the middle radial line segment  702  and no portion of lower undulation  608  lies on the upper undulation  606  side of the middle radial line segment  702 . Furthermore, upper undulation  606  and lower undulation  608  may be nonoverlapping in an embodiment in which at least one straight radial line segment  702  extends between inner edge  202  and outer edge  204  at a peripheral location between adjacent surround segments  508 . Accordingly, upper undulation  606  and lower undulation  608  of  FIG. 7  may be considered to be nonoverlapping, since a single straight radial line segment is located between adjacent undulations. 
     It will be apparent then from the description above that surround segments  508  having upper undulations  606  and surround segments  508  having lower undulations  608  may be arranged sequentially in the peripheral direction around outer rim  502 . More particularly, around the perimeter of diaphragm  108 , film  506  may periodically rise and fall in a wave-like, up and down, undulating manner. Thus, in an embodiment, each surround segment  508  having an upper undulation  606  of film  506  may be separated from other surround segments  508  having other upper undulations  606  by one or more surround segment  508  having a lower undulation  608 . For example, at least one lower undulation  608  may be disposed between each pair of upper undulations  606  of film  506 . Similarly, each lower undulation  608  of film  506  may be separated from other lower undulations  608  by one or more upper undulations  606 . For example, at least one upper undulation  606  may be disposed between each pair of lower undulations  608 . Accordingly, surround segments  508  of film  506  may be arranged in a series in the peripheral direction such that each upper undulation  606  is followed by a lower undulation  608 , each lower undulation  608  is followed by an upper undulation  606 , and so on. 
     In an embodiment, sequentially arranged surround segments  508  may have respective chords that are contiguous with one another. For example, a peripheral chord  704  of an upper undulation  606  may meet a peripheral chord  704  of a lower undulation  608  at a radial line segment  702  shared by the sequential surround segments  508 . That is, the peripheral chord  704  of the upper undulation  606  may intersect radial gap  604  on the radial plane  602  at the same location that the peripheral chord  704  of the lower undulation  608  intersects the radial gap  604 . Accordingly, the immediately adjacent surround segments  508  may be contiguous in the peripheral direction, since the surround segments  508  meet along the same radial line segment  702 . In an embodiment, the surround segments  508  may be contiguous along the entire length of the shared radial line segment  702 . Alternatively, the surround segments  508  may be contiguous, i.e., share a surface boundary line over a portion of the length between inner edge  202  and outer edge  204 , and the undulation boundaries may be separated from each other over another portion of the length between inner edge  202  and outer edge  204 . 
     Referring to  FIG. 12 , a perspective cutaway view, taken from Detail A of  FIG. 5 , of an undulating portion of a surround is shown in accordance with an embodiment. In an embodiment, surround segment  508  having upper undulation  606  and surround segment  508  having lower undulation  608  may be nonoverlapping with each other and spaced apart in the peripheral direction. For example, similar to the embodiment illustrated in  FIG. 7 , upper undulation  606  and lower undulation  608  may include surface boundaries defined between inner edge  202 , outer edge  204 , and a respective pair of radial line segments  702 . Unlike  FIG. 7 , however, rather than upper undulation  606  and lower undulation  608  being immediately adjacent such that each surface boundary shares a middle radial line segment  702 , respective radial line segments  702  may be separated by an intermediate section  1202 . Intermediate section  1202  may include a surface boundary having a radial width defined between inner edge  202  and outer edge  204 . The boundary may further include respective radial line segments  702  of adjacent surround segments  508 . In an embodiment, intermediate section  1202  may be flat. For example, peripheral chords  704  and radial chords  706  through intermediate section  1202  may be straight line segments, i.e., straight peripheral line segments or straight radial line segments, such that intermediate section  1202  does not rise above or below radial gap  604 , but rather, is a flat film portion extending across radial plane  602  in the peripheral direction along radial gap  604 . 
     Still referring to  FIG. 12 , in an embodiment, with surround segments  508  separated from each other in the peripheral direction by intermediate sections  1202 , radial line segments  702  may not extend straightly between inner edge  202  and outer edge  204 , but rather, radial line segments  702  may include curvilinear line segments  1204  extending between inner edge  202  and outer edge  204 . More particularly, curvilinear line segments  1204  may include arcuate line segments that curve from inner edge  202  to outer edge  204  in a generally radial direction to define an hourglass-shaped intermediate section  1202 . Curvilinear line segments  1204  may bow outward toward an adjacent undulation, e.g., reaching a curve peak at peripheral chord  704 . Alternatively, curvilinear line segment  1204  may bow inward, e.g., toward a radial chord  706  passing through upper apex  802  or lower apex  902  of the respective surround segment  508 . Thus, radial line segments  702  bounding surround segments  508  need not be straight, but may be curved such that adjacent surround segments  508  do not overlap. That is, nonoverlapping surface boundaries of adjacent surround segments  508  may not be intersected by a straight radial line extending from inner edge  202  to outer edge  204 . Even more particularly, any cross-section taken about a radial line through film  506  may include a profile that is above or below radial gap  604 , but not both above and below radial gap  604 . As such, in an embodiment, no radial cross-section may show both a portion of upper undulation  606  and a portion of lower undulation  608 . Furthermore, such profiles may include either a straight line segment or a smooth curvilinear chord between inner edge  202  and outer edge  204 , but in an embodiment, the profiles do not include a multi-segmented line with one or more angles between segments extending between inner edge  202  and outer edge  204 . 
     Referring to  FIG. 13 , a cross-sectional view, taken about line C-C of  FIG. 12 , of a surround segment having an upper undulation separated from a surround segment having a lower undulation by an intermediate section is shown in accordance with an embodiment. Surround segment  508  having upper undulation  606  and surround segment  508  having lower undulation  608  may be arranged sequentially in the peripheral direction along radial gap  604 , but may be separated from each other along at least one peripheral chord  704  by intermediate section  1202 . As shown, intermediate section  1202  may be flat in the peripheral direction, i.e., the cross-section along peripheral chord  704  may be straight between curvilinear line segments  1204  lying on radial gap  604 . Thus, while a surface curvature of upper undulation  606  may be entirely above radial gap  604  and a surface curvature of lower undulation  608  may be entirely below radial gap  604 , intermediate section  1202  between surround segments  508  may have a length in the peripheral direction, i.e., a peripheral line segment between radial line segments  702 , along radial gap  604 . Lengths of peripheral line segments may vary across intermediate section  1202 , as in the case of an hourglass-shaped intermediate section  1202  having adjacent curvilinear line segments  1204  that are nearer to each other at the middle of the hourglass than at inner edge  202  and outer edge  204 . In at least one location, the curvilinear line segments  1204  may touch, making the peripheral length zero at that point where the immediately adjacent surround segments  508  are contiguous and nonoverlapping. In an embodiment, a maximum length of any peripheral line segment of intermediate section  1202  may be less than 20 mm, and in some cases less than 15 mm. For example, intermediate section  1202  may have a maximum length between radial line segments  702  defining its boundary, e.g., curvilinear line segments  1204 , of less than 10 mm. 
     Referring to  FIG. 14A , a perspective cutaway view of a corner region of a surround is shown in accordance with an embodiment. Surround  110  may include film  506  that does not have surround segments  508  along a corner  507  region around a corner of diaphragm  108 . More particularly, surround segments  508  on either side of corner  507  region of film  506  may be bounded by respective radial line segments  702  and those radial line segments  702 , as well as inner edge  202  and outer edge  204  between diaphragm  108  and frame  102 , may define a surface boundary of a flat section  1402  around corner  507  region. Flat section  1402  of film  506  may have a same thickness of surround segments  508 , or in an alternative embodiment, may be thinner or thicker than surround segments  508 . Thus, flat section  1402  may be more or less prone to deformation under different modes of motion, based on the differences in cross-section profiles between flat section  1402  and, e.g., an adjacent surround segment  508 . 
     Referring to  FIG. 14B , a perspective cutaway view of a corner region of a surround is shown in accordance with an embodiment. In an embodiment, surround  110  includes film  506  having corner  507  region that includes a half-arc section  1404 . For example, a length of film  506  between radial line segments  702  on either side of corner  507  region may have a cross-sectional profile similar to half-arc  206  profile shown in  FIG. 2 . The half-arc profile may extend below or above radial gap  604 . As with flat section  1402 , half-arc section  1404  may influence how stress is distributed throughout film  506 . More particularly, including half-arc section  1404  along corner  507  region may cause stress to distribute throughout the portions of film  506  having surround segments  508 . For example, in the case of a rectangular diaphragm  108 , stress generated by various rocking modes may distribute primarily along the straight sides of film  506  having sequential surround segments  508  that include upper undulations  606  and lower undulations  608 . Minimal stress may be distributed through film  506  around corner  507  region within half-arc section  1404  in such a case. More particularly, in an embodiment, film  506  having no undulations in the corner  507  regions may promote balanced motion at all resonant frequencies of audio speaker  100  by shifting control of motion-induced stresses to the surround segments  508  along the sides instead of to the half-arc  206  profiles in the corner  507 . Accordingly, surround  110  having film  506  with surround segments  508  as described above may cause driven mass  402  of audio speaker  100  to behave quite differently with respect to rocking modes. 
     In an embodiment, film  506  may have no corner region. For example, an outer rim of diaphragm  108  and an inner rim of frame  102  may both be circular, and thus, film  506  may have an annular structure with an inner and outer radius. Nonetheless, stresses may distribute in surround segments  508  along the annular structure of surround  110  to promote balanced motion at all resonant frequencies. 
     Just as the cross-sectional profiles of surround segments  508  may vary, so may the cross-sectional profiles of corner segments vary, too. For example, a cross-sectional profile of a radial cross-section taken through a corner segment of surround  110  may be sinusoidal. In an embodiment, the surface morphology of the corner segments is smooth and continuous. That is, cross-sectional profiles taken through the corner segments may include a radial chord that is continuous and progresses smoothly from inner edge  202  to outer edge  204 , without any bends, angles, or folds along the path. 
     Referring to  FIG. 15 , a perspective view of an audio speaker surround is shown in accordance with an embodiment. In an embodiment, audio speaker  100  includes a suspension system, e.g., a single-suspension system, having surround  110  connecting a diaphragm with a frame (not shown). As described above, the diaphragm, e.g., diaphragm  108 , may include a rigid member having circular, rectangular, or any other shaped outer rim. Furthermore, the frame, e.g., frame  102 , may include an inner rim shaped similar to the diaphragm outer rim, and the inner rim may be separated from the outer rim by a radial gap. Thus, surround  110  may be connected to the outer rim at an inner edge and may be connected to the inner rim at an outer edge  204  that is separated from the inner edge  202  along a radial plane to provide a suspension between the diaphragm and the frame across the radial gap. Accordingly, surround  110  may be an essentially circular, rectangular, or otherwise-shaped ring having an inner edge  202  with an inner perimeter and an outer edge  204  with an outer perimeter, and having a film thickness along a peripheral path between the edges. The film thickness may be constant or may vary in the peripheral or radial direction. For example, the film may be thicker at the inner and outer perimeters than at a location between inner edge  202  and outer edge  204 , or vice versa. 
     As described above, the radial gap may extend across a radial plane  602  that is intersected by a central axis of diaphragm  108  and passes in a radial direction between the outer rim  204  of diaphragm  108  and the inner rim  202  of frame  102 . As such, film  506  may extend across the radial gap, e.g., radial gap  604 , to provide a hermetic barrier between a space above radial plane  602  and a space below radial plane  602  across radial gap  604 . The hermetic barrier may be provided by hermetically sealing inner edge  202  to the outer rim of diaphragm  108  and outer edge  204  to the inner rim of frame  102  using adhesive or welding, as is known in the art. 
     Surround  110  may include a film  506  formed in part from a thin flexible sheet extending along the radial gap  604  between the inner edge  202  and the outer edge  204  and having a radial width along radial plane  602 . At least a portion of film  506  may undulate in the peripheral direction such that cross-sections of film  506  taken immediately adjacent to one another are not identical. Accordingly, film  506  may include several surround segments  508  that are periodically and/or sequentially arranged in the peripheral direction around at least a portion of the outer rim of diaphragm  108 . 
     Film  506  may be formed from a thin, single-layered or multi-layered material. Furthermore, film  506  may be formed from a flexible material, such as soft rubber or another elastomeric material. In another embodiment, film  506  may be formed from more rigid materials. For example, film  506  may include several laminated layers of an inelastic material. More particularly, by way of example, film  506  may include a lamination foil of polyether ether ketone (PEEK) capable of elastically deforming in a range of 3-5%. 
     In an embodiment, the surround segments  508  may include several repeating surround segments that include essentially identical surface morphologies. For example, the surround segments  508  may include a repeating surround segment  1502  with an essentially identical surface contour compared to one or more other repeating surround segments  1502  of film  506 . The surface contour of repeating surround segment  1502  may extend across a surface boundary defined between inner edge  202  and outer edge  204  that are spaced apart from each other in a radial direction along radial plane  602  across radial gap  604 , as well as a pair of radial line segments  702  that are spaced apart from each other in the peripheral direction. In an embodiment, every surround segment  508  along surround length  1504  between adjacent corners  507  may be one of several repeating surround segments  1502 , i.e., may have the same surface contour of repeating surround segments  1502 . In an embodiment, the entire length of film  506  may include repeating surround segments  1502 , e.g., as in the case of an annular film  506  having circular inner edge  202  and outer edge  204  without discrete corners. In  FIG. 15 , detailed contour lines are only shown for the repeating surround segments  1502  along surround length  1504 , to avoid obscuring the drawing, and one or more of the surround segments  508  not on surround length  1504  may have the same surface morphology of repeating surround segment  1502 . In another embodiment, surround segments  508  along surround length  1504  or around the entire length of film  506  may have surface contours that vary, or are asymmetric, as described above. 
     Repeating surround segments  1502  of surround  110  may include several undulations, and in an embodiment, these undulations may be further described as including one or more upper undulation  606  and one or more lower undulation  608 . Upper undulations  606  may be formed in film  506  above radial gap  604 , e.g., on a front side of radial plane  602  along which radial gap  604  lies between inner edge  202  and outer edge  204 . Similarly, lower undulations  608  may be formed in film  506  below radial gap  604 , e.g., on a rear side of radial plane  602 . Thus, upper undulations  606  and lower undulations  608  may have respective heights on opposite sides of radial gap  604 . Accordingly, in an embodiment, undulations of repeating surround segments  1502  may include all of the same aspects as described above with respect to surround segments  508 . For example, in some cases immediately adjacent repeating surround segments  1502  may include respective undulations (either upper or lower undulations) that do not overlap along the peripheral direction. That is, in an embodiment, no portion of an upper undulation of a repeating surround segment  1502  lies on the same side of a radial line segment as a lower undulation. Accordingly, one skilled in the art will recognize that the description pertaining to  FIGS. 15-17C  below mesh conceptually with the description above. One skilled in the art, however, will recognize certain differences between the following embodiments and some of the embodiments described above. For example, as described below, in some embodiments, a surround  110  may include surround segments  508  having cross-sections taken about a radial line through film  506  that may include a profile that is both above and below radial gap  604 , i.e., a surround segment  508  may include both an upper undulation  606  and a lower undulation  608  radially beside each other. 
     Referring to  FIG. 16 , a perspective cutaway view, taken from Detail B of  FIG. 15 , of a repeating surround segment having an upper undulation and a lower undulation is shown in accordance with an embodiment. Repeating surround segment  1502  may include a surface boundary defined by inner edge  202 , outer edge  204 , and a pair of radial line segments  702  extending across radial gap  604  from inner edge  202  to outer edge  204 . Radial line segments  702  are separated in the peripheral direction. In an embodiment, the radial line segments  702  intersect an intermediate line  1602  that is disposed between inner edge  202  and outer edge  204  and extends over a surface of repeating surround segment  1502 . For example, intermediate line  1602  may extend over the surface along radial plane  602 . More particularly, intermediate line  1602  may run generally in the peripheral direction to define a contour line where radial plane  602  intersects the undulating surface of film  506 . Thus, at any point, intermediate line  1602  may have a peripheral and/or radial component. 
     Repeating surround segment  1502  may include one or more upper undulations above radial gap  604  and one or more lower undulations below radial gap  604 . The undulations may be arranged beside each other. For example, in an embodiment, repeating surround segment  1502  includes upper undulation  606  above radial gap  604  on a first side of intermediate line  1602 , e.g., upper undulation  606  may extend between intermediate line  1602  and outer edge  204  and have a height above radial gap  604 . Furthermore, in an embodiment, repeating surround segment  1502  includes lower undulation  608  below radial gap  604  on a second side of intermediate line  1602 , e.g., lower undulation  608  may extend between intermediate line  1602  and inner edge  202  and have a height below radial gap  604 . Thus, upper undulation  606  may be radially separated from lower undulation  608  by intermediate line  1602 . Alternatively, upper undulation  606  may extend between intermediate line  1602  and inner edge  202 , and lower undulation  608  may extend between intermediate line  1602  and outer edge  204 . In any case, upper undulation  606  and lower undulation  608  of a same repeating surround segment  1502  may be arranged side-by-side. 
     Upper undulation  606  and lower undulation  608  may have respective surface contours extending across the surface boundary of repeating surround segment  1502 , and in an embodiment, the respective surface contours may be smooth. That is, as described above, the surface contours of respective undulations may include smooth curvatures extending smoothly across the surface boundary between a respective inner edge  202  or outer edge  204 , and intermediate line  1602 . Smoothly extending surface contours may be contrasted with non-smooth contours that include local angulations, corners, or folds. 
     In an embodiment, upper undulation  606  may include an upper peripheral chord  1604  extending continuously and smoothly in the peripheral direction along the surface of repeating surround segment  1502 . Upper peripheral chord  1604  may define a surface contour between intermediate line  1602  and outer edge  204 , i.e., on the surface curvature of upper undulation  606 . Upper peripheral chord  1604  may intersect an upper radial chord  1606  at an upper apex  1608  of upper undulation  606 . Upper apex  1608  may have an upper apical distance, i.e., a height above radial plane  602 , that is greater than a distance between radial plane  602  and any other point along the surface of upper undulation  606  on repeating surround segment  1502 . 
     In an embodiment, lower undulation  608  may include a lower peripheral chord  1610  extending smoothly in the peripheral direction along the surface of repeating surround segment  1502 . Lower peripheral chord  1610  may define a surface contour between intermediate line  1602  and inner edge  202 , i.e., on the surface curvature of lower undulation  608 . Lower peripheral chord  1610  may intersect a lower radial chord  1612  at a lower apex  1614  of lower undulation  608 . Lower apex  1614  may have a lower apical distance, i.e., a height below radial plane  602 , that is greater than a distance between radial plane  602  and any other point along the surface of lower undulation  608  on repeating surround segment  1502 . 
     In an embodiment, upper peripheral chord  1604  and lower peripheral chord  1610  extend over the surface of repeating surround segment  1502  on opposite sides of intermediate line  1602 . Thus, upper apex  1608  and lower apex  1614  may be radially offset from one another on opposite sides of intermediate line  1602 . More specifically, upper apex  1608  and lower apex  1614  may not be at a same radial distance from central axis  404 , and thus, may not be aligned along a same peripheral chord running in a peripheral direction along repeating surround segment  1502  or surround  110 . In addition to being radially offset, upper apex  1608  and lower apex  1614  of a same repeating surround segment  1502  may be offset in a peripheral direction as shown (no radial chord runs through both upper apex  1608  and lower apex  1614 ). Alternatively, the apices may be peripherally aligned, i.e., a radial chord may run through both upper apex  1608  and lower apex  1614 . 
     The surface curvature of upper undulation  606  and the surface curvature of lower undulation  608  may intersect along intermediate line  1602 . In an embodiment, the curvatures meet at a same distance from inner edge  202  and outer edge  204  around the entire length of surround  110 . The intersection of the upper surface curvature of upper undulation  606  and the lower surface curvature of lower undulation  608  may provide a contiguous surface curvature extending across the surface boundary of repeating surround segment  1502 . Furthermore, in an embodiment, the contiguous surface curvature may be continuous and smooth, e.g., any radial or peripheral chord along the contiguous surface curvature may be either straight or curvilinear, i.e., there may be no local angulations, corners, or folds along the surface where upper undulation  606  and lower undulation  608  meet at intermediate line  1602 . A surface curvature with continuous and smooth peripheral and radial chords, i.e., without a zig-zag or angulated transition between undulation regions may reduce stress in surround  110  materials, as compared to a surround that includes folds or corners between undulation transitions. Thus, surround  110  having a contiguous and smooth surface contour may experience improved fatigue life. 
     Referring to  FIG. 17A , a cross-sectional view, taken about line D-D of  FIG. 16 , of a repeating surround segment having an upper undulation and a lower undulation is shown in accordance with an embodiment. Upper apex  1608  is located at a maximum apical distance from radial gap  604  on an outer edge  204  side of a medial plane  1702 . In an embodiment, medial plane  1702  is a plane that is normal to radial gap  604 , i.e., normal to radial plane  602 , and extends in a peripheral direction at a consistent distance between inner edge  202  and outer edge  204  around an entire length of surround  110 . For example, medial plane  1702  may intersect radial plane  602  half way between inner edge  202  and outer edge  204 . A medial line  1704  define a surface contour of repeating surround segment  1502  at a location where the surface of  1502  intersects medial plane  1702 . For example, medial line  1704  may extend in a peripheral direction from a point on the surface that is radially equidistant from inner edge  202  and outer edge  204 . 
     In an embodiment, intermediate line  1602  runs along the surface of repeating surround segment  1502  at a location where upper undulation  606  and lower undulation  608  meet at radial gap  604 . That is, intermediate line  1602  may be a contour line that separates upper undulation  606  from lower undulation  608  at radial plane  602 . A cross-section taken through surround  110  through upper apex  1608  may coincide with a portion of surround  110  where the radial width of upper undulation  606  is greater than the radial width of lower undulation  608 , and thus, intermediate line  1602  may be located between medial plane  1702  and inner edge  202 . Furthermore, when viewed from above, intermediate line  1602  may follow a curvilinear, e.g., a sinusoidal, path along radial plane  602 . Thus, a radial slice through upper apex  1608  may intersect intermediate line  1602  at a point of inflection, meaning that the radial direction of a follower moving along intermediate line  1602  in a peripheral direction may change from moving toward inner edge  202  to moving toward outer edge  204 . That is, a tangent of intermediate line  1602  along radial plane  602  may extend in the peripheral direction with no slope in the radial direction. In any case, repeating surround segment  1502  includes both an upper undulation  606  above radial gap  604  and a lower undulation  608  below radial gap  604 , and the upper and lower undulations may be radially arranged on opposite sides of intermediate line  1602 . 
     Referring to  FIG. 17B , a cross-sectional view, taken about line E-E of  FIG. 16 , of a repeating surround segment having an upper undulation and a lower undulation is shown in accordance with an embodiment. A radial cross-section taken through a portion of repeating surround segment  1502  at which medial line  1704  and intermediate line  1602  coincide may include upper undulation  606  and lower undulation  608  having equivalent radial widths. For example, upper undulation  606  may extend from outer edge  204  to intermediate line  1602  at medial plane  1702 , lower undulation  608  may extend from inner edge  202  to intermediate line  1602  at medial plane  1702 , and the radial distances between medial plane  1702  and both edges may be equal. Furthermore, at such a location, the apical distances, i.e., the heights relative to radial gap  604 , of both upper undulation  606  and lower undulation  608  may be equal. Thus, in an embodiment, a radial cross-section through a location of repeating surround segment  1502  includes upper undulation  606  that is symmetric with lower undulation  608  across radial gap and radially offset from lower undulation  608  across medial plane  1702  where the undulation contours meet. In an embodiment, the distance along a surface contour between inner edge  202  and outer edge  204  (a radial chord length) at all peripheral locations along the surface contour of repeating surround segment  1502  may be equal. For example, the lengths of the surface contours shown in  FIGS. 17A-17C  may be the same. 
     Referring to  FIG. 17C , a cross-sectional view, taken about line F-F of  FIG. 16 , of a repeating surround segment having an upper undulation and a lower undulation is shown in accordance with an embodiment. The cross-sectional view may essentially mirror the contour of  FIG. 17A  across medial plane  1702  and radial plane  602 , i.e., it may be the contour of  FIG. 17A  rotated 180 degrees. As such, lower apex  1614  is located at a maximum apical distance from radial gap  604  on an inner edge  202  side of medial plane  1702 . Medial line  1704  may define a surface contour of repeating surround segment  1502  that extends in a peripheral direction from a point where repeating surround segment  1502  (and in this case lower undulation  608  of repeating surround segment) intersects medial plane  1702 . 
     In an embodiment, intermediate line  1602  defines a surface contour of repeating surround segment  1502  at a location where upper undulation  606  and lower undulation  608  meet at radial plane  602 . A radial cross-section taken through surround  110  through lower apex  1614  may coincide with a portion of surround  110  where the radial width of lower undulation  608  is greater than the radial width of upper undulation  606 , and thus, intermediate line  1602  may be located between medial plane  1702  and outer edge  204 . Furthermore, when viewed from above, intermediate line  1602  at the radial cross-section through lower apex  1614  may be at a point of inflection, meaning that the radial direction of a follower moving along intermediate line  1602  may change from moving toward outer edge  204  to moving toward inner edge  202 . In any case, repeating surround segment  1502  includes both an upper undulation  606  above radial gap  604  and a lower undulation  608  below radial gap  604 , and the upper and lower undulations may be radially arranged on opposite sides of intermediate line  1602 . 
     In an embodiment, the distance in the radial direction along the contour of repeating surround segment  1502  may vary based on a peripheral location along surround  110 . That is, rather than each radial cross-section having the same spline length along the contour surface (length along a radial chord), the spline lengths may vary from slice to slice. As a result, in an embodiment, upper undulation  606  and lower undulation  608  may always meet at medial line  1704 , even though the apical distances of the undulations may vary in the peripheral direction. Thus, every radial slice of surround  110  may resemble  FIG. 17B , with the height of upper undulation  606  and lower undulation  608  varying from slice to slice. 
     In an embodiment, every radial chord of repeating surround segment  1502 , including radial chords of radial cross-sections that correspond to the pair of radial line segments  702  bounding the peripheral ends of repeating surround segment  1502 , may include curvilinear line segments. For example, radial chords, e.g., radial line segment  702  that provides a transition between adjacent repeating surround segments  1502 , may be sinusoidal line segments to provide for both upper undulation  606  above radial gap  604  and lower undulation  608  below radial gap  604 . This contrasts with some of the above-described embodiments that include straight radial line segment  702  across radial gap  604  in that the curvilinear radial line segments  702  are not aligned or coplanar with radial plane  602 . 
     Repeating surround segment  1502  may be repeated along a portion or all of surround  110 , e.g., along surround length  1504  as shown in  FIG. 15 . Thus, repeating surround segment  1502  may be located adjacent to another repeating surround segment  1502  with the same characteristics of repeating surround segment  1502 . For example, the adjacent repeating surround segment  1502  may have a second boundary around a second upper undulation and a second lower undulation. The second upper undulation may include a second upper peripheral chord, which may actually be an extension of upper peripheral chord  1604  as it traverses the surface of surround  110  in the peripheral direction. Similarly, the second lower undulation may include a second lower peripheral chord, which may actually be an extension of lower peripheral chord  1610  as it traverses the surface of surround  110  in the peripheral direction. Accordingly, upper peripheral chord  1604  may be contiguous with the second upper peripheral chord and lower peripheral chord  1610  may be contiguous with the second lower peripheral chord such that the repeating surround segments  1502  are arranged sequentially with each other in the peripheral direction. 
     Based on the above description, a person of ordinary skill in the art will appreciate that surround  110  may include a series of sequential upper undulations  608  on one side of a dividing line, e.g., intermediate line  1602 , and a series of sequential lower undulations  606  on another side of the dividing line. The isolation of surround  110  surface contours to one side or the other of radial gap  604  on respective sides of a dividing line, however, is not intended to be limiting. For example, in an embodiment, surround  110  surface on an inner side of a dividing line may have lower undulations  606  and upper undulations  608  in sequence (pairs of lower undulations  606  separated by an upper undulation  608  and pairs of upper undulations  608  separated by a lower undulation). Similarly, surround  110  surface on an outer side of a dividing line may also have lower undulations  606  and upper undulations  608  in sequence. The undulations on opposite sides of the dividing line may be staggered. That is, a lower undulation  606  on an inner side of the dividing line may be radially beside an upper undulation  608  on the other side of the dividing line, and an upper undulation on the inner side of the dividing line may be radially beside a lower undulation  606  on the other side of the dividing line. Thus, a portion of surround  110  inward of the dividing line may include a surface that is both above and below radial gap  604 , and a portion of the surround  110  outward of the dividing line may also include a surface that is both above and below radial gap  604 . 
     It will be appreciated then that in an embodiment where surround segments  508  are repeating surround segments  1502  with identical surface morphologies, the pairs of radial line segments  702  that define the ends of repeating surround segment  1502  may correspond to any radial slices that are separated from each other in the peripheral direction along surround  110  and share a common surface contour. For example, radial lines segments  702  defining the surface boundary of a repeating surround segment  1502  may include radial slices through portions of surround  110  have matching profiles of cross-sections D-D, E-E, or F-F of  FIGS. 17A-17C , by way of example. Accordingly, respective boundaries of sequentially arranged repeating surround segments  1502  may include a shared radial line segment  702  such that the repeating surround segments  1502  are contiguous in the peripheral direction. Additionally, the contiguous surface contours of the adjacent repeating surround segments  1502  may be continuous and smooth without angles, corners, or folds at the radial line segments  702  at which they intersect. For example, adjacent repeating surround segments  1502  may meet at a radial line segment  702  corresponding to the sinusoidal line segment of cross-section E-E of  FIG. 17B . Thus, radial line segment  702  shared by the immediately adjacent repeating surround segments  1502  may intersect intermediate line  1602  at an inflection point of the radial line segment  702 . The inflection point of radial line segment  702  may be the location where the surface curvature changes from concave upward along lower undulation  608  to concave downward along upper undulation  606 , i.e., at the transition between undulations. In an embodiment, the inflection point of radial line segment  702  coincides with the intersection between radial line segment  702  and medial plane  1702 , as shown in  FIG. 17B . 
     The description of  FIGS. 15-17C  are provided above by way of example and not limitation, and it will be appreciated by one skilled in the art that the embodiments of those figures may also be combined with the embodiments described earlier. For example, peripheral chords and/or radial chords of repeating surround segment  1502  may have stepped contour profiles along respective lower undulations  606  and upper undulations  608 , similar to those described with respect to  FIG. 8B . Furthermore, repeating surround segments  1502  having several undulations may be separated in the peripheral direction by intermediate sections or corner sections as described with respect to  FIGS. 12-14B . Additionally, surround  110  having repeating surround segments  1502  may not be shaped as a rectangular ring, as shown in  FIG. 15 , but may instead be annular such that perimeters of inner edge  202  and outer edge  204  are circular with respective radii. Thus, one skilled in the art will understand that the above description provides a comprehensive framework that may be used to extrapolate to other embodiments not directly described, but which are nonetheless contemplated within the scope of the description. 
     Referring back to  FIG. 4 , driven mass  402  of audio speaker  100  may oscillate along central axis  404  in the pistonic motion mode, and may also participate in non-pistonic modes. The pistonic mode may dominate the non-pistonic modes over most frequencies within the range of driving frequencies generated by an audio player during sound reproduction. Non-pistonic modes, however, may dominate the pistonic mode at some resonant frequencies, e.g., at higher order eigenfrequencies. Surround segments  508 , e.g., repeating surround segments  1502 , of surround  110  may be flexible in the axial direction to allow driven mass  402  to participate, i.e., move, freely in the pistonic mode within all frequencies. Surround segments  508 , however, may be stiff in out-of-plane directions, e.g., in non-pistonic directions, to limit participation in non-pistonic modes. For example, the curvature of undulation surface contours may resist lateral loads and/or bending moments applied by tilting motion  410  of driven mass  402 . In particular, the arrangements of upper undulations  606  and lower undulations  608  described above may create a surround  110  structure with adjacent elements that correspondingly expand/contract or stretch/compress to resist transverse loading, but which flex together under axial loading. Finite element analysis has indicated that this complementary structure may result in pistonic participation at higher order eigenfrequencies that is not less than within one order of magnitude of non-pistonic participation. This represents a decrease in non-pistonic participation at those frequencies by a factor of 55, as compared to an analysis of surround  110  having half-arc profile  206  around the entire perimeter of diaphragm  108 . It follows that audio speaker  100  having surround  110  with film  506  that includes surround segments having upper undulations  606  and lower undulations  608  can reduce the tendency of surround  110  to dissipate energy in out-of-plane rocking modes and thereby diminish the likelihood of rubbing between voicecoil  106  and magnet  104  that can cause reliability and audio quality issues. 
     In the foregoing specification, the invention has been described with reference to specific exemplary embodiments 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: 20150529
Publication Date: 20181113
Grant Date: 20181113
Priority Date: 20140912
Inventors: VIEITES, PABLO SEOANE
WILK, CHRISTOPHER
HARDY, SUZANNE
SALVATTI, ALEXANDER V.
LEONHARDT, Oliver
Porter, Scott P.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04R2307/207", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R7/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R7/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R2307/207", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R7/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R7/16", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R2307/207", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R7/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R7/26", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R7/16", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R7/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04R7/26", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R2307/207", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R7/16", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 55456154