Abstract:
An acoustical transducer such as an audio loudspeaker or a microphone, having a suspension component whose outermost edge extends axially rather than radially and couples with an axial mounting surface in the transducer&#39;s frame rather than with a radial flat surface of the frame. The suspension component may be a surround or a spider. Eliminating the radial portions of the suspension component and the frame enables the use of a larger diaphragm within a transducer of unchanged outer dimensions, increasing the amount of air moved by or moving the diaphragm. It also enables closer on-center packing of multiple transducers onto the same baffle such as the front baffle of a speaker enclosure, or, put another way, it enables a higher percentage of the mounting baffle&#39;s front surface area to be covered with moving diaphragm area. Radial mounting flanges and their mounting holes are limited to portions of the frame which will not increase the gap space between adjacent transducers or other boundaries. The angled corner tabs of a square or hexagonal frame housing a round diaphragm would occupy the baffle surface area that would otherwise be unutilized with circular-frame speakers.

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field of the Invention 
   This invention relates generally to electromagnetic transducers such as audio speakers, and more specifically to an improved frame and surround suspension configuration for such. 
   2. Background Art 
     FIG. 1  illustrates a conventional speaker  10  with an external magnet geometry motor structure  12  driving a diaphragm assembly  14 . The motor structure includes a pole plate  16  style yoke, made of soft magnetic material and including a back plate  18  and a pole piece  20  that are either magnetically coupled or of integral construction. The pole plate may optionally include a ventilation hole  22  for depressurizing the diaphragm assembly. One or more external ring hard magnets  24  are magnetically coupled to the back plate. A top plate  26  of soft magnetic material is magnetically coupled to the hard magnets. A magnetic air gap  28  is formed between the top plate and the pole piece. 
   A frame or basket  30  is mechanically coupled to the motor assembly to support the diaphragm assembly. A diaphragm  32 , sometimes referred to as a cone, is coupled to the basket by a flexible suspension component known as a surround  34 . A voice coil former or bobbin  36  is mechanically coupled to the diaphragm, and is coupled to the basket by a flexible suspension component known as a spider  38 . The surround and spider allow the bobbin and diaphragm to move axially with respect to the motor structure, but prevent, as much as possible, their lateral movement and rocking. An electrically conductive voice coil  40  is wound around and mechanically coupled to the bobbin, and is disposed within the magnetic air gap of the motor structure. A dust cap  42  is coupled to the diaphragm to seal the open end of the bobbin. 
   As illustrated in the detail view  1 A, the surround includes a middle portion  44  such as a half-roll of flexible rubber, which provides the flexible suspension function of the surround. The surround also includes an inner portion  46  which is glued or otherwise coupled to the diaphragm  32 , and an outer portion  48  which is glued or otherwise coupled to the frame  30 . More specifically, the outer portion  48  of the surround extends radially outward, perpendicular to the axis of the speaker&#39;s motor structure, and is coupled to a similarly outward-extending flange  50  of the frame. The flange has a dimension sufficient to not only provide a large gluing surface for the surround, but also to accommodate the various mounting holes  52  which are used to couple the speaker basket to a baffle such as the front of an enclosure or a wall. 
   The suspending middle portion of the surround is not necessarily in the shape of a half-roll, but can be any suitable shape. 
     FIG. 2  illustrates that having these radially-extending components around the entire perimeter of the speaker limits the size of the diaphragm relative to the total outer dimension of the speaker, and limits the designer&#39;s ability to pack the diaphragms of multiple speakers in close proximity to each other on a common baffle. As shown in detail  2 A, there is a considerable distance from the effective outer perimeter of one speaker&#39;s diaphragm  32   a  to the effective outer perimeter of the adjacent speaker&#39;s diaphragm  32   b , because of the radially-extending outer surround components  46   a  and  46   b , and because of the radially-extending frame flanges  50   a  and  50   b , especially as the flanges must be wide enough to encompass the mounting holes. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be understood more fully from the detailed description given below and from the accompanying drawings of embodiments of the invention which, however, should not be taken to limit the invention to the specific embodiments described, but are for explanation and understanding only. 
       FIG. 1  shows, in perspective view with a partial cutaway and a detail view, a conventional external magnet geometry speaker according to the prior art. 
       FIG. 2  shows, in perspective view, a multi-speaker baffle assembly according to the prior art. 
       FIG. 3  shows, in perspective view with a partial cutaway and a detail view, one embodiment of a speaker having the improved surround and frame of this invention. 
       FIG. 4  shows, in axial view with a detail view, the speaker of  FIG. 3 . 
       FIG. 5  shows, in perspective view, a multi-speaker baffle assembly according to this invention, using the speaker of  FIGS. 3 and 4 . 
       FIG. 6  shows, in perspective view with a partial cutaway, another embodiment of a speaker having the improved surround and another embodiment of a frame according to this invention. 
       FIG. 7  shows, in perspective view, another multi-speaker cabinet assembly according to this invention, using the speaker of  FIG. 6 . 
       FIG. 8  shows, in perspective with a detail view, another speaker according to this invention with a hold-down ring for the surround. 
       FIGS. 9 and 10  show alternative embodiments of the frame, surround, and hold-down ring of the invention. 
   

   DETAILED DESCRIPTION 
     FIG. 3  illustrates one embodiment of a speaker  100  according to this invention. The speaker includes an improved frame or basket  102  coupling a diaphragm assembly to a motor structure. The frame includes a base  104  for coupling to the motor structure, a mounting flange  108 , and a connecting structure  106  extending generally outward and upward from the base to support the mounting flange. The base may comprise a flat plate, as shown, or it may have any other suitable shape, according to the needs of the application at hand, such as a cylinder for coupling to the outside of an internal magnet motor structure cup. The connecting structure  106  may be in the form of ribs or legs, for ventilation, or they may be an unvented cup-like structure. 
   The mounting flange includes tab portions  110  which extend outward to provide support for mounting the speaker and to provide adequate clearance for the mounting holes  112 . The mounting flange also includes non-tab portions  114  which do not extend outward any significant distance, only enough to form a seal with the baffle to which it is mounted and to have sufficient thickness of frame material to provide structural integrity. The outer perimeter of the diaphragm is suspended from the mounting flange of the frame by an improved surround  120 . 
   As seen in the detail view  3 A, the mounting flange includes a generally axially-aligned groove  128  which mates with a generally axially-aligned outer portion  126  of the surround  120 . The surround thus is lacking a conventional outer glue-joint flat portion which would need to extend a significant distance outward beyond where the groove  128  is. The surround is shown as including a conventional glue-joint inner flat portion  124  which mates with the conventional diaphragm, however it could alternatively use a coupling mechanism similar to the groove  128  if desired. The non-coupled middle portion  122  of the surround provides the suspension action of the surround. 
   In some embodiments, a complete groove  128  is not necessary, and the mounting flange includes only a raised lip  129 . The surround is overlapped over the lip, and glued or otherwise coupled in place. Whether in the form of a groove, a lip, or other geometric configuration, these may be collectively termed mounting surfaces which are substantially radially aligned. 
   The radial fins on the outer surface of the frame&#39;s mounting flange are for aesthetic purposes and to improve thermal transfer by increasing the surface area of the basket, and are not necessary, but gives an added benefit from the use of the non-circular frame of this invention. 
     FIG. 4  illustrates the speaker  100  as viewed axially from the top. The diaphragm  32  and dust cap  42  are visible, as are the suspension portion  120  and inner glue joint portion  124  of the surround. The frame&#39;s tabbed  110  and non-tabbed  114  portions are visible, as are the mounting holes  112  which extend through the tabs  110 . The detail view  4 A illustrates that the outermost face  130  of the axially-aligned outer lip  126  of the suspension can be in extremely close proximity to the outermost edge  132  of the non-tabbed portions of the frame. 
   This dimension may be on the order of ¼ or less than that which would be required in the prior art to accommodate a radially-extending outer glue joint flat portion of the surround. This allows multiple drivers with a given effective piston radiating area (SD) to be packed much closer together, or, stated another way, drivers with a given overall width to have a significantly larger SD, without sacrificing the maximum excursion capability of the suspension. 
   In one embodiment, the outer perimeter of the frame&#39;s mounting flange may be substantially square, to facilitate an advantageous adjacent packing of speakers. 
     FIG. 5  illustrates one embodiment of a multi-speaker assembly  150  taking advantage of this invention. The assembly includes a speaker cabinet or baffle  152  to which are coupled a plurality of speakers  100   a–n  such as those of  FIG. 4 . In some embodiments, the speakers may be placed into extremely close proximity, or even butted against each other&#39;s outer edges, as shown. As can be seen, the lack of the surrounds&#39; outer radial glue joint portions allows a significantly closer center-to-center spacing of the speakers, as two such portions are eliminated between each adjacent pair of speakers. As can further be seen, the non-tabbed portions of the frame further enable tight packing, as the mounting holes are moved to positions which are not in the critical adjacent dimensions. 
   In some embodiments, the distance between the suspending middle portions of the surrounds of an adjacent speaker pair, as measured over the non-tabbed portions of their respective frames, is less than half the radial dimension of one of the suspending middle portions. From surround OD to surround OD of adjacent drivers, it is possible to achieve a spacing as low as 4–6 mm, although, at such a tight spacing, it would be advisable to provide additional structural support to the baffle in the region directly below this spacing. 
     FIG. 6  illustrates another embodiment of a speaker  160  according to this invention. The speaker is similar to that described above, except that the mounting flange of its frame  162  has a hexagonal shape rather than square. The hexagonal shape includes six non-tabbed portions  164  where the surround extends very nearly to the perimeter of the speaker, and six tabbed portions  166  which provide mounting surface and clearance for the mounting holes. 
     FIG. 7  illustrates one embodiment of a multi-speaker assembly  170  including a cabinet or baffle  172  and a plurality of speakers  160   a–n , and demonstrates the maximally effective packing enabled by the hexagonal shape. Regions  174   a–m  can advantageously be used for port openings (not shown) in a vented box configuration. 
   Other speaker basket shapes may certainly be used, but may provide less effective packing than hexagonal or square speakers. Other shapes which provide tight packing factors include triangular, rectangular, and trapezoidal. 
   The invention enables a speaker to be placed in closer radial proximity to any other object, not only to other similar speakers. For example, a single speaker may be put into a radially smaller front baffle of an enclosure than would be possible if clearance were needed for a radially-extending outer surround glue joint flat portion, and/or for a complete perimeter flange, as in the prior art. 
   The diaphragm is not necessarily round or axisymmetric, and could be, for example, oval shaped, square, hexagonal, octagonal, or the like. For instance, a 12-sided polygon diaphragm would be particularly well-suited to be combined with a hexagonal frame. It is not necessarily the case that the surround have an identical cross-sectional shape at all radial sections. In some embodiments, the surround may not even use the same outer attachment mechanism (e.g. the groove illustrated above) at all radial locations. 
     FIG. 8  and its detail view  8 A illustrate another embodiment of a speaker  180  according to this invention. The speaker includes a diaphragm  120  which is coupled to the outer mounting flange  182  of the frame by a hold-down ring  184 . The hold-down ring may, in one embodiment, have a shape which is generally a sideways T, as shown. The frame includes a groove  186  which may, optionally, have a slightly beveled shape such that it is wider at its external opening than at its floor. The generally axially-aligned outer portion  126  of the surround extends into the groove. 
   The hold-down ring includes a generally axially-aligned pinch wedge  188  which extends into the groove to pinch the surround against the side wall of the groove. The pinch flange may optionally have a beveled shape such that it is narrower at its end than at its base, as shown. The hold-down ring may further include a radially-extending mounting portion  190  by which the hold-down ring is coupled to the frame (as shown) or, alternatively, to the baffle (not shown). The mounting portion may include tabbed regions  192  which extend outward to provide clearance for mounting bolts or the like. The hold-down ring may optionally include a generally axially-aligned extension  194  which provides additional axial height to the hold-down ring. This stiffens the hold-down ring by providing a lengthened bending moment, in order to distribute the hold-down force more evenly, especially in the non-tabbed regions of the frame and hold-down ring where there is no room for hold-down bolts. 
     FIG. 9  and its detail views  9 A and  9 B illustrate a frame and suspension assembly  200  according to another embodiment of this invention. The mounting flange  202  of the frame has a lip  204  with a generally axial outer face. The generally axial outer rim of the surround  210  is pinched against the lip by an L-shaped hold-down ring  208  which includes a radially-extending portion  209  and an axially-extending portion  211 . The axially-extending portion  211  comprises the pinch wedge and may extend around the entire hold-down ring, while the radially-extending portion may extend all the way around or, as illustrated, it may be truncated or non-existent in the non-tabbed regions of the frame, to minimize the distance from the diaphragm to the outer dimension of the speaker. 
   In the  9 B detail view, the hold-down ring has been cross-sectioned with a different cutaway angle than the other components, for better visibility of an optional radial segment  212  of the surround which fits into a channel  206  formed into the surface of the mounting flange of the frame. 
     FIG. 10  illustrates the surround  210  in further detail. The surround includes radial segments  212  which correspond to the radially-aligned glue-joint flat outer portions of a conventional surround, except that these segments do not extend around the entire circumference of the surround. Rather, the radial segments are interrupted by portions of the surround whose outer edge comprises only the generally axially-aligned outer rim  214  of the surround. As seen in  FIG. 9 , the radial segments  212  may be employed in the tabbed regions of the frame&#39;s mounting flange, while the axial sections  214  may be employed in the non-tabbed regions of the frame&#39;s mounting flange. This configuration provides some measure of the surround attachment mechanism of the prior art, without sacrificing the spacing and diaphragm size advantages of the present invention. 
   CONCLUSION 
   The various features illustrated in the figures may be combined in many ways, and should not be interpreted as though limited to the specific embodiments in which they were explained and shown. 
   While the invention has been described with reference to embodiments of an audio loudspeaker, those skilled in the art will readily appreciate that the invention may be embodied as a microphone, or any other transducer which has an oscillating diaphragm. While the invention has been described with reference to a motor structure which provides motive force to a diaphragm assembly, those skilled in the art will readily appreciate that when the diaphragm is externally driven by acoustic energy, the motor structure functions as a generator, producing electrical signals representative of the received acoustic waves. And, while the invention has been described in terms of an electromagnetic motor structure, those skilled in the art will readily recognize that alternative motor or generator means may be employed in conjunction with the invention, such as piezo electric structures or electrostatic structures. Furthermore, while the invention has been described with reference to transducers which include motor structures, it may also be used in e.g. a passive radiator which includes a diaphragm, a frame, and a suspension, but no motor structure. 
   While the invention has been described with reference to a particular suspension component in the form of a flexible rubber surround which is the outermost suspension component in the speaker, the skilled reader will readily appreciate that the same principles may be applied to other suspension components, such as a spider. A spider may have an axial outer perimeter coupled to an axial mounting surface, to reduce the overall dimension of the frame at that location, or to facilitate the use of a larger spider within a given outer frame dimension. In the case of a spider or other suspension component which is not the outermost, and which may typically be coupled not directly to the diaphragm but to another diaphragm assembly component such as the bobbin, the mounting flange in question will be the frame structure at which the suspension component is mounted, rather than the outermost mounting flange at which the diaphragm&#39;s surround is coupled. The suspension component has been illustrated as having a half-roll shape, but could, in other embodiments, have any other suitable suspension shape, such as the accordion shape which is commonly used in spiders. The suspension component has been illustrated as having a generally radially-extending inner portion for flat gluing to the front surface of the diaphragm, but could, in other embodiments, have any other suitable configuration or attachment means. For example, it may have a generally axial orientation. 
   Those skilled in the art having the benefit of this disclosure will appreciate that many other variations from the foregoing description and drawings may be made within the scope of the present invention. Indeed, the invention is not limited to the details described above. Rather, it is the following claims including any amendments thereto that define the scope of the invention.