Abstract:
Electro-dynamic loudspeakers typically include a diaphragm having a conductor applied to one of its surfaces. The diaphragm is secured to a frame. The conductor is connected to a power supply for providing electrical current through linear traces of the conductor that interact with magnetic fields generated by magnets that are mounted to the frame. The diaphragm is driven by a motive force created when current passes through the conductor within the magnetic field. The electrical current is varied to create an acoustical output from the electro-dynamic loudspeaker. Different frame structures are provided for simplifying the manufacturing process and defining a reduced cost electro-dynamic loudspeaker.

Description:
1. CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/380,001, filed on May 2, 2002; U.S. Provisional Application No. 60/378,188, filed on May 6, 2002; and U.S. Provisional Application No. 60/391,134, filed on Jun. 24, 2002. The disclosures of the above applications are incorporated herein by reference.  
         [0002]    This application incorporates by reference the disclosures of each of the following co-pending applications which have been filed concurrently with this application: U.S. patent application Ser. No. ______, entitled “Mounting Bracket System,” filed May 2, 2003; U.S. patent application Ser. No. ______, entitled “Film Tensioning System,” filed May 2, 2003; U.S. patent application Ser. No. ______, entitled “Film Attaching System,” filed May 2, 2003; U.S. patent application Ser. No. ______, entitled “Electrical Connectors For Electro-Dynamic Loudspeakers,” filed May 2, 2003; U.S. patent application Ser. No. ______, entitled “Electro-Dynamic Loudspeaker Mounting System,” filed May 2, 2003; U.S. patent application Ser. No. ______, entitled “Conductors For Electro-Dynamic Loudspeakers,” filed May 2, 2003; U.S. patent application Ser. No. ______, entitled “Acoustically Enhanced Electro-Dynamic Loudspeakers,” filed May 2, 2003; U.S. patent application Ser. No. ______, entitled “Directivity Control Of Electro-Dynamic Loudspeakers,” filed May 2, 2003; U.S. patent application Ser. No. ______, entitled “Frequency Response Enhancements For Electro-Dynamic Loudspeakers,” filed May 2, 2003; and U.S. patent application Ser. No. ______, entitled “Magnet Arrangement For Loudspeaker,” filed May 2, 2003. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0003]    1. Field of Invention  
           [0004]    The invention relates to electro-dynamic loudspeakers, and more particularly, to improvements for electro-dynamic loudspeakers and related manufacturing methods.  
           [0005]    2. Related Art  
           [0006]    The general construction of an electro-dynamic loudspeaker includes a diaphragm, in the form of a thin film, attached in tension to a frame. An electrical circuit, in the form of electrically conductive traces, is applied to the surface of the diaphragm. Magnetic sources, typically in the form of permanent magnets, are mounted adjacent to the diaphragm or within the frame, creating a magnetic field. When current is flowing in the electrical circuit, the diaphragm vibrates in response to the interaction between the current and the magnetic field. The vibration of the diaphragm produces the sound generated by the electro-dynamic loudspeaker.  
           [0007]    Many design and manufacturing challenges present themselves in the manufacturing of electro-dynamic loudspeakers. First, the diaphragm, that is formed by a thin film, needs to be permanently attached, in tension, to the frame. Correct tension is required to optimize the resonance frequency of the diaphragm. Optimizing diaphragm resonance extends the bandwidth and reduces sound distortion of the loudspeaker.  
           [0008]    The diaphragm is driven by the motive force created when current passes through the conductor applied to the diaphragm within the magnetic field. The conductor on the electro-dynamic loudspeaker is attached directly to the diaphragm. Because the conductor is placed directly onto the thin diaphragm, the conductor should be constructed of a material having a low mass and should also be securely attached to the film at high power (large current) and high temperatures.  
           [0009]    The frame of the electro-dynamic loudspeaker supports the magnets, the diaphragm, and the terminal. The frame presents its own design challenges. The frame must be capable of being bonded to the diaphragm film. The frame must be rigid enough to maintain the diaphragm film in uniform tension and not be susceptible to deforming during handling, assembly, or over time. A ferrous frame has the advantage of being capable of carrying magnetic energy or flux. The frame also should be capable of withstanding high environmental temperatures, humidity, salt spray, etc.  
           [0010]    Alternatively, a plastic frame has an advantage in that the underlying process and mold tooling can be designed with spring loaded inserts to provide very precise control of the separation distance between the top of the imbedded magnets and the film conductor. This control is effective even for magnet lots with relatively high thickness variation. Such improved control allows wide tolerance and more economic magnet specifications. In addition, because separation distance variation is reduced, and process to design capability is improved, performance may be improved by reducing and minimizing the mean separation distance between driver and magnets. Finally, the plastic frame molding process readily and economically accepts various additional and beneficial features such as locators and mounting tabs that can be incorporated into the part at little added cost. This capability improves application value.  
           [0011]    Designing conductors for electro-dynamic loudspeaker applications presents various challenges such as selecting the speaker with the desired audible output for a given location that will fit within the size and location constraints of the desired applications environment. Electro-dynamic loudspeakers exhibit a defined acoustical directivity pattern relative to each speaker&#39;s physical shape and the frequency of the audible output produced by each loudspeaker. Consequently, when an audio system is designed, loudspeakers possessing a desired directivity pattern over a given frequency range are selected to achieve the intended performance of the system. Different loudspeaker directivity patterns may be desirable for various loudspeaker applications. For example, for use in a consumer audio system for a home listening environment, a wide directivity may be preferred. In the application of a loudspeaker, a narrow directivity may be desirable to direct sound, e.g., voice, in a predetermined direction.  
           [0012]    Often, space limitations in the listening environment prohibit the use of a loudspeaker in an audio system that possesses the preferred directivity pattern for the system&#39;s design. For example, the amount of space and the particular locations available in a listening environment for locating and/or mounting the loudspeakers of the audio system may prohibit the use of a particular loudspeaker that exhibits the intended directivity pattern. Also, due to space and location constraints, it may not be possible to position or oriented the desired loudspeaker in a manner consistent with the loudspeaker&#39;s directivity pattern. Consequently, size and space constraints of a particular environment may make it difficult to achieve the desired performance from the audio system. An example of a listening environment having such constraints is the interior passenger compartment of an automobile or other vehicle.  
           [0013]    While the electric circuitry of electro-dynamic loudspeakers may present design challenges, electro-dynamic loudspeakers are very desirable loudspeakers because they are designed to have a very shallow depth. With this dimensional flexibility, electro-dynamic loudspeakers may be positioned at locations where conventional loudspeakers would not traditionally fit. This dimensional flexibility is particularly advantageous in automotive applications where positioning a loudspeaker at a location that a conventional loudspeaker would not otherwise fit could offer various advantages. Further, because the final loudspeaker assembly may be mounted on a vehicle, it is important that the assembly be rigid during shipping and handling so that the diaphragm or frame does not deform during installation.  
           [0014]    While conventional electro-dynamic loudspeakers are shallow in depth and may therefore be preferred over conventional loudspeakers for use in environments requiring thin loudspeakers, electro-dynamic loudspeakers have a generally rectangular planar radiator that is generally relatively large in height and width to achieve acceptable operating wavelength sensitivity, power handling, maximum sound pressure level capability and low-frequency bandwidth. Unfortunately, the large rectangular size results in a high-frequency beam width angle or coverage that may be too narrow for its intended application. The high-frequency horizontal and vertical coverage of a rectangular planar radiator is directly related to its width and height in an inverse relationship. As such, large radiator dimensions exhibit narrow high-frequency coverage and vice versa.  
         SUMMARY  
         [0015]    The invention provides several frame structures and methods for constructing frames related to electro-dynamic loudspeakers. A bowed frame is elastically deformed and a diaphragm is attached to the frame while positioned in the deformed position. The frame is subsequently released to elongate and tension the diaphragm.  
           [0016]    A method of constructing the bowed frame includes injecting molten resin into a mold having a first die half at a first temperature and a second die half at a temperature other than the first temperature.  
           [0017]    A plurality of magnets are embedded within a molded plastic frame. A diaphragm is coupled to the frame and spaced apart from the magnets.  
           [0018]    An elastomeric member, coupled to a portion of the frame, is elastically deformed prior to installation of a diaphragm. The diaphragm is coupled to the elastomeric member while the elastomeric member is compressed. After the diaphragm and elastomeric member are fixed to one another, the force compressing the elastomeric member is released thereby tensioning the diaphragm.  
           [0019]    A casement is molded about the perimeter of a diaphragm while the diaphragm is tensioned. A plurality of magnets are coupled to a frame. The casement is coupled to the frame to construct an electro-dynamic loudspeaker. Also, a mold for constructing a casement and diaphragm assembly is disclosed.  
           [0020]    Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views.  
         [0022]    [0022]FIG. 1 is a perspective view of an electro-dynamic loudspeaker as it would appear with the grille removed.  
         [0023]    [0023]FIG. 2 is an exploded perspective view of the electro-dynamic loudspeaker shown in FIG. 1 having a grille.  
         [0024]    [0024]FIG. 3 is a cross-sectional view of the electro-dynamic loudspeaker taken along line  3 - 3  of FIG. 1.  
         [0025]    [0025]FIG. 4 is an enlarged cross-sectional view of the encircled area of FIG. 3.  
         [0026]    [0026]FIG. 5 is a plan view showing a conductor on a diaphragm of an electro-dynamic loudspeaker.  
         [0027]    [0027]FIG. 6 is a plan view of a vacuum platen for use in constructing an embodiment of the invention.  
         [0028]    [0028]FIG. 7 is a cross-sectional side view of the vacuum platen shown in FIG. 6.  
         [0029]    [0029]FIG. 8 is a perspective view of a clamp assembly for use in constructing an electro-dynamic loudspeaker.  
         [0030]    [0030]FIG. 9 is a cross-sectional side view of the clamp assembly of FIG. 8.  
         [0031]    [0031]FIG. 10 is a plan view of the clamp assembly in a closed position.  
         [0032]    [0032]FIG. 11 is a cross-sectional side view of the clamp assembly in the closed position.  
         [0033]    [0033]FIG. 12 is a plan view of an assembly fixture for assembling an electro-dynamic loudspeaker.  
         [0034]    [0034]FIG. 13 is a cross-sectional side view of the assembly fixture.  
         [0035]    [0035]FIG. 14 is a plan view of the clamp assembly positioned atop the assembly fixture.  
         [0036]    [0036]FIG. 15 is a cross-sectional side view of the closed clamp assembly positioned atop the assembly fixture.  
         [0037]    [0037]FIG. 16 is cross-sectional side view of a work-in-process electro-dynamic loudspeaker.  
         [0038]    [0038]FIG. 17 is a cross-sectional side view of a finished electro-dynamic loudspeaker.  
         [0039]    [0039]FIG. 18 is a cross-sectional view of a film tensioning device.  
         [0040]    [0040]FIG. 19 is a cross-sectional side view of an alternate film tensioning device.  
         [0041]    [0041]FIG. 20 is a perspective view of an alternate tensioning member.  
         [0042]    [0042]FIG. 21 is a cross-sectional side view depicting use of the alternate tensioning member shown in FIG. 20.  
         [0043]    [0043]FIG. 22 is a cross-sectional side view further depicting diaphragm tensioning using the alternate tensioning member of FIG. 20.  
         [0044]    [0044]FIG. 23 depicts a frame in an undeformed state and a deformed state.  
         [0045]    [0045]FIG. 24 is an exploded perspective view of an alternate electro-dynamic loudspeaker.  
         [0046]    [0046]FIG. 25 is a cross sectional view of an injection mold used to construct the bowed frame of the loudspeaker depicted in FIG. 24.  
         [0047]    [0047]FIG. 26 is a perspective top view of an alternate plastic frame.  
         [0048]    [0048]FIG. 27 is a perspective bottom view of the alternate frame of FIG. 26.  
         [0049]    [0049]FIG. 28 is a cross-sectional view of the frame of FIG. 27 taken along line  28 - 28 .  
         [0050]    [0050]FIG. 29 is an enlarged partial cross-sectional view of a plastic frame and magnet assembly.  
         [0051]    [0051]FIG. 30 is a partial perspective view of a terminal detail of an alternate plastic frame and magnet assembly.  
         [0052]    [0052]FIG. 31 is an exploded perspective view of an alternate electro-dynamic loudspeaker.  
         [0053]    [0053]FIG. 32 is a cross-sectional view of a casement and diaphragm subassembly taken along line  32 - 32 .  
         [0054]    [0054]FIG. 33 is a cross-sectional view of the alternate electro-dynamic loudspeaker of FIG. 31.  
         [0055]    [0055]FIG. 34 is a cross-sectional view of an injection mold.  
         [0056]    [0056]FIG. 35 is a cross-sectional view of an alternate electro-dynamic speaker assembly including a retainer coupling a casement to a frame.  
         [0057]    [0057]FIG. 36 is an exploded cross-sectional view of an alternate electro-dynamic loudspeaker with additional molded in plastic assembly features.  
         [0058]    [0058]FIG. 37 is a perspective view of the electro-dynamic loudspeaker of FIG. 36.  
         [0059]    [0059]FIG. 38 is a partial cross-sectional view of an alternate injection mold incorporating a film tensioning feature in the mold tool.  
         [0060]    [0060]FIG. 39 is a cross-sectional view of an alternate electro-dynamic loudspeaker.  
         [0061]    [0061]FIG. 40 is a cross-sectional view of another alternate electro-dynamic loudspeaker. 
     
    
     DETAILED DESCRIPTION  
       [0062]    [0062]FIG. 1 is a perspective view of an electro-dynamic loudspeaker  100  of the invention. As shown in FIG. 1, the electro-dynamic loudspeaker is a generally planar loudspeaker having a frame  102  with a diaphragm  104  attached in tension to the frame  102 . A conductor  106  is positioned on the diaphragm  104 . The conductor  106  is shaped in serpentine fashion having a plurality of substantially linear sections (or traces)  108  longitudinally extending along the diaphragm interconnected by radii  110  to form a single current path. Permanent magnets  202  (shown in FIG. 2) are positioned on the frame  102  underneath the diaphragm  104 , creating a magnetic field.  
         [0063]    Linear sections  108  are positioned within the flux fields generated by permanent magnets  202 . The linear sections  108  carry current in a first direction  112  and are positioned within magnetic flux fields having similar directional polarization. Linear sections  108  of conductor  106  having current flowing in a second direction  114 , that is opposite the first direction  112 , are placed within magnetic flux fields having an opposite directional polarization. Positioning the linear sections  108  in this manner assures that a driving force is generated by the interaction between the magnetic fields developed by magnets  202  and the magnetic fields developed by current flowing in conductor  106 . As such, an electrical input signal traveling through the conductor  106  causes the diaphragm  104  to move, thereby producing an acoustical output.  
         [0064]    [0064]FIG. 2 is an exploded perspective view of the electro-dynamic loudspeaker  100  shown in FIG. 1. As illustrated in FIG. 2, the flat panel loudspeaker  100  includes a frame  102 , a plurality of high energy magnets  202 , a diaphragm  104 , an acoustical dampener  236  and a grille  228 . Frame  102  provides a structure for fixing magnets  202  in a predetermined relationship to one another. In the depicted embodiment, magnets  202  are positioned to define five rows of magnets  202  with three magnets  202  in each row. The rows are arranged with alternating polarity such that fields of magnetic flux are created between each row. Once the flux fields have been defined, diaphragm  104  is fixed to frame  102  along its periphery.  
         [0065]    A conductor  106  is coupled to the diaphragm  104 . The conductor  106  is generally formed as an aluminum foil bonded to the diaphragm  104 . The conductor  106  can, however, be formed from other conductive materials. The conductor  106  has a first end  204  and a second end  206  positioned adjacent to one another at one end of the diaphragm  104 .  
         [0066]    As shown in FIG. 2, frame  102  is a generally dish-shaped member preferably constructed from a substantially planar contiguous steel sheet. The frame  102  includes a base plate  208  surrounded by a wall  210 . The wall  210  terminates at a radially extending flange  212 . The frame  102  further includes apertures  214  and  216  extending through flange  212  to provide clearance and mounting provisions for a conductor assembly  230 .  
         [0067]    Conductor assembly  230  includes a terminal board  218 , a first terminal  220  and a second terminal  222 . Terminal board  218  includes a mounting aperture  224  and is preferably constructed from an electrically insulating material such as plastic, fiberglass or other insulating material. A pair of rivets or other connectors (not shown) pass through apertures  214  to electrically couple first terminal  220  to first end  204  and second terminal  222  to second end  206  of conductor  106 . A fastener such as a rivet  226  extends through apertures  224  and  216  to couple conductor assembly  230  to frame  102 .  
         [0068]    A grille  228  functions to protect diaphragm  104  from contact with objects inside the listening environment while also providing a method for mounting loudspeaker  100 . The grille  228  has a substantially planar body  238  having a plurality of apertures  232  extending through the central portion of the planar body  238 . A rim  234  extends downward, substantially orthogonally from body  238 , along its perimeter and is designed to engage the frame  102  to couple the grille  228  to the frame  102 .  
         [0069]    An acoustical dampener  236  is mounted on the underside of the base plate  208  of the frame  102 . Dampener  236  serves to dissipate acoustical energy generated by diaphragm  104  thereby minimizing undesirable amplitude peaks during operation. The dampener  236  may be made of felt, or a similar gas permeable material.  
         [0070]    [0070]FIG. 3 is a cross-sectional view of the electro-dynamic loudspeaker taken along line  3 - 3  of FIG. 1. FIG. 3 shows the frame  102  having the diaphragm  104  attached in tension to the frame  102  and the permanent magnets  202  positioned on the frame  102  underneath the diaphragm  104 . Linear sections  108  of the conductor  106  are also shown positioned on top of the diaphragm  104 .  
         [0071]    [0071]FIG. 4 is an enlarged cross-sectional view of the encircled area of FIG. 3. As illustrated by FIG. 4, the diaphragm  104  is comprised of a thin film  400  having a first side  402  and a second side  404 . First side  402  is coupled to frame  102 . Generally, the diaphragm  104  is secured to the frame  102  by an adhesive  406  that is curable by exposure to radiation. However, the diaphragm  104  may secured to the frame  102  by other mechanism, such as those known in the art.  
         [0072]    To provide a movable membrane capable of producing sound, the diaphragm  104  is mounted to the frame in a state of tension and spaced apart a predetermined distance from magnets  202 . The magnitude of tension of the diaphragm  104  depends on the speaker&#39;s physical dimensions, materials used to construct the diaphragm  104  and the strength of the magnetic field generated by magnets  202 . Magnets  202  are generally constructed from a highly energizable material such as neodymium iron boron (NdFeB), but may be made of other magnetic materials. The thin diaphragm film  400  is generally a polyethylenenaphthalate sheet having a thickness of approximately 0.001 inches; however, the diaphragm film  400  may be formed from materials such as polyester (e.g., known by the tradename “Mylar”), polyamide (e.g., known by the tradename “Kapton”) and polycarbonate (e.g., known by the tradename “Lexan”), and other materials known by those skilled in the art for forming diaphragms  104 .  
         [0073]    The conductor  106  is coupled to the second side  404  of the diaphragm film  400 . The conductor  106  is generally formed as an aluminum foil bonded to diaphragm film  400 , but may be formed of other conductive material known by those skilled in the art.  
         [0074]    The frame  102  includes a base plate  208  surrounded by a wall  210  extending generally orthogonally upward from the plate  208 . The wall  210  terminates at a radially extending flange  212  that defines a substantially planar mounting surface  414 . A lip  416  extends downwardly from flange  212  in a direction substantially parallel to wall  210 . Base plate  208  includes a first surface  418 , a second surface  420  and a plurality of apertures  422  extending through the base plate  208 . The apertures  422  are positioned and sized to provide air passageways between the first side  402  of diaphragm  104  and first surface  418  of frame  102 . An acoustical dampener  236  is mounted to second surface  420  of frame base plate  208 .  
         [0075]    Various systems for assembling an example loudspeaker  100  will now be described. A first example system is depicted in FIGS.  5 - 17 . The first system includes a vacuum platen  600  (FIGS.  6 - 7 ) and a film clamp  800  (FIGS.  8 - 9 ). Vacuum platen  600  and film clamp  800  may be used in conjunction with one another to restrain diaphragm  104  (FIG. 5) in a flat position without tension. Once diaphragm  104  is fixed within clamp  800 , film  400  may be subsequently tensioned as will be described later.  
         [0076]    The initial flattening and clamping of diaphragm  104  may provide the assembler with a known diaphragm state to which tension may be added. Difficulties may arise in attempting to obtain a reproducible tension during subsequent assembly operations when diaphragm  104  is not first placed in a substantially flat, no tension state. This first example system includes vacuum platen  600  and film clamp  800  to achieve a repeatable diaphragm state. In other examples, any other mechanism(s) and/or techniques capable of providing a known diaphragm state to which tension may be added may be used.  
         [0077]    The example vacuum platen  600  includes a base  700  having a body  702  and a pedestal  704  protruding from a first surface  602  of body  702 . Pedestal  704  includes an upper surface  706  positioned substantially parallel to first surface  602 . A vacuum passageway  708  may extend through pedestal  704  and body  702  to couple upper surface  706  with a vacuum source  604 . A cap  710  may be coupled to pedestal  704  along upper surface  706 . Cap  710  may be constructed from a gas permeable material such as porous aluminum. Base  700  may be constructed from a gas impermeable material. Accordingly, a suction force is created along an upper surface  606  of cap  710  when vacuum source  604  draws a vacuum in vacuum passageway  708 .  
         [0078]    The example film clamp  800  includes an upper clamp half  802  and a lower clamp half  804  connected by a hinge  806 . The illustrated upper clamp half  802  includes a generally rectangularly shaped body  808  and an elastomeric gasket  810 . Body  808  includes an aperture  900  (FIG. 9) extending through body  808 . Elastomeric gasket  810  includes a similarly shaped aperture  902  (FIG. 9) extending through the thickness of gasket  810 . Elastomeric gasket  810  may be attached to body  808  to provide a compressible high friction surface  812  for engagement with diaphragm  104 .  
         [0079]    The illustrated lower clamp half  804  is constructed from a generally rectangularly shaped aluminum frame  814  having an aperture  904  extending through the lower clamp half  804 . Lower clamp half  804  includes an upper surface  906  and a lower surface  908 .  
         [0080]    During the loudspeaker assembly process, film clamp  800  may be positioned on vacuum platen  600  such that pedestal  704  enters aperture  904  of lower clamp half  804  as illustrated in FIG. 9. Once seated, upper surface  906  of lower clamp half  804  may be substantially coplanar with upper surface  606  of cap  710 . In order to properly position diaphragm  104 , upper clamp half  802  may be rotated to place film clamp  800  in the open position depicted in FIG. 8.  
         [0081]    With vacuum source  604  turned off, diaphragm  104  may be placed on upper surface  606 . Diaphragm  104  may be aligned relative to lower clamp half  804  using sights  816 . Sights  816  may be visual markings, rods, rings, notches or any other form of alignment mechanism formed on diaphragm  104  to assist in the alignment procedure. The location of sights  816  effectively defines a perimeter portion  818  and a center portion  820  of diaphragm  104 . Center portion  820  may contain most, if not all, of the material which will remain coupled to frame  102  at the completion of the assembly process.  
         [0082]    Once diaphragm  104  has been properly positioned, vacuum may be supplied to cap  710  via vacuum source  604 . Because cap  710  is constructed from a gas permeable material, diaphragm  104  is forced to closely conform to planar upper surface  606 . While the vacuum source is maintained, upper clamp half  802  may be rotated to place film clamp  800  in a closed position as shown in FIGS. 10 and 11. During clamp closure, elastomeric gasket  810  may deform locally to account for the thickness of diaphragm  104 . Latches  822  secure upper clamp half  802  to lower clamp half  804 . It should be appreciated that latches  822  are merely exemplary devices for coupling the clamp halves together and that any number of fastening devices may be implemented. Once upper clamp half  802  is clamped to lower clamp half  804 , vacuum is turned off and film clamp  800  holding diaphragm  104  in an untensioned state is removed from vacuum platen  600 .  
         [0083]    Frame  102  may be fixtured in an example assembly fixture  1200  (FIGS. 12 and 13). Assembly fixture  1200  may be shaped substantially similarly to vacuum platen  600 . However, assembly fixture  1200  may include a recess  1300  for receipt of a portion of frame  102 . Assembly fixture  1200  includes a gage surface  1302  offset a predetermined distance  1304  from planar mounting surface  408  of frame  102 . In order to apply tension to diaphragm  104 , distance  1304  is greater than the thickness of lower clamp half  804 . The magnitude of tension generated is optimized by defining distance  1304  in concert with the physical characteristics of frame  102  and diaphragm  104 .  
         [0084]    Diaphragm  104  may be mechanically coupled with frame  102 . For example, adhesive  406  may be applied to planar mounting surface  408  of frame  102 . Adhesive  406  may alternatively be applied to diaphragm  104 . After application of adhesive  406 , film clamp  800  including clamped diaphragm  104  may be positioned on assembly fixture  1200  such that frame  102  enters aperture  904  of lower clamp half  804  (FIGS. 14 and 15). The diaphragm  104  may contact adhesive  406  and planar mounting surface  408  of frame  102 . Contact may occur prior to lower surface  908  of lower clamp half  804  contacting gage surface  1302  of assembly fixture  1200 . To produce the desired tension in film  400 , film clamp  800  is forced down over assembly fixture  1200  so that lower surface  908  engages gage surface  1302 .  
         [0085]    Depending on the type of adhesive used, a subsequent process may be required. For example, adhesive  406  is curable by exposure to radiation. Accordingly, while film clamp  800  is coupled to assembly fixture  1200 , a radiation source  1500  is energized to cure the adhesive and secure diaphragm  104  to frame  102 . Alternatively, where some other mechanical coupling mechanism is used, appropriate processes may need to be performed.  
         [0086]    A second example system used to tension the diaphragm of a loudspeaker  100  is described with reference to FIGS. 16 and 17. In this system, frame  102  includes an elongated radially extending flange  1600  which does not include a downwardly extending lip. The remaining planar loudspeaker components are substantially similar to those previously described. The assembly process may include positioning diaphragm  104  in a substantially flat, no tension state as previously described. However, it should be appreciated that the flattening and clamping steps are not necessarily required to construct planar loudspeaker according to this system. Similarly, alternate tensioning methods that are described are not intended to be limited to include the flattening and clamping process.  
         [0087]    A bead of adhesive  406  may be applied along the periphery of either or both frame  102  and diaphragm  104 . Diaphragm  104  may then be aligned with and bonded to frame  102  via adhesive  406 . As noted earlier, adhesive  406  may be a light curable material or any other suitable bonding agent which may affix the dissimilar materials to one another. Similarly, adhesive  406  may any other coupling mechanism to mechanically couple the diaphragm  104  to the frame  102 .  
         [0088]    Radially extending flange  1600  may be mechanically deformed by bending an outer peripheral region down from line  1700  as shown in FIG. 17 to tension diaphragm  104 . Line  1700  acts as a fulcrum around the perimeter of frame  102  about which diaphragm  104  is stretched. The proper diaphragm tension may be obtained in a variety of ways. For example, if diaphragm  104  was initially coupled to frame  102  in a substantially flat, non-tension state, a deflection distance  1702  may be empirically determined by testing. Once the proper deflection distance is determined, hard tooling may be created to repeatably deform frame  102  and move radially extending flange  1600  the predetermined deflection distance  1702  during the assembly of each loudspeaker  100 .  
         [0089]    Another example system of assuring proper film tension includes a feedback system  1602 . One example feedback system may involve placing a known load at the center of diaphragm  104  and measuring the deflection of the diaphragm at the load application point. The desired deflection per load may be empirically determined by testing where the resonance frequency of diaphragm  104  is plotted against deflection per a given load. Once the desired resonance frequency is determined for a given speaker geometry, a target diaphragm deflection per given load may be determined. The feedback system may operate by measuring the actual diaphragm deflection at a known load with a deflection sensor  1604 . The measured actual deflection may be compared to the target deflection.  
         [0090]    Frame  102  may be deformed until the measured deflection is substantially equal to the target deflection, thereby properly tensioning diaphragm  104  to produce the desired resonance frequency. Logic control systems such as proportional, integral, derivative closed feedback loops, etc. may be implemented to control the mechanical deflection of frame  102  during the tensioning process. Such a control system may provide a high degree of repeatability regarding film tensioning.  
         [0091]    Another example feedback system  1704  may directly measure resonance frequency during film tensioning using a frequency sensor  1706 . In this control scheme, diaphragm  104  may be repeatedly excited and the resonance frequency measured. The measured frequency may be compared to a desired target frequency during film tensioning. Frame  102  may be deformed until the measured resonance frequency matches the target frequency within an acceptable tolerance. It should be appreciated that the feedback systems described may be used with any of the tensioning techniques described.  
         [0092]    Yet another film tensioning system will be described in greater detail with reference to FIG. 18. An example film tensioner  1800  includes an upper plate  1802  and a lower plate  1804 . Plates  1802  and  1804  have matching beveled apertures  1806  and  1808 , respectively. Center portion  820  of diaphragm  104  is positioned within the openings defined by apertures  1806  and  1808 . Apertures  1806  and  1808  may be sized and shaped slightly larger than frame  102  to allow insertion of frame  102  within one of the apertures  1806  and  1808 .  
         [0093]    Upper plate  1802  may include an annular groove  1810  having an asymmetrical cross-section as shown in FIG. 18. Lower plate  1804  may include an annular groove  1812  shaped as the mirror image of groove  1810 . A first elastomeric member  1814  may be positioned within groove  1810  and a second elastomeric member  1816  may be positioned within groove  1812 . Grooves  1810  and  1812  may be shaped to constrain movement of the elastomeric members  1814  and  1816  toward apertures  1806  and  1808 , respectively. In addition, grooves  1810  and  1812  may be shaped to allow movement of elastomeric members  1814  and  1816  away from apertures  1806  and  1808 . Specifically, the annular grooves  1810  and  1812  may be shaped to impart a lateral force to center portion  820  of diaphragm  104  when an axial force is applied to upper plate  1802  and lower plate  1804  drawing them toward one another.  
         [0094]    Upper plate  1802  may also include threaded apertures  1818 . Stepped apertures  1820  extend through lower plate  1804 . Threaded fasteners  1822 , which are illustrated as bolts, may be inserted in apertures  1820  and tightened into threaded apertures  1818  to draw upper plate  1802  and lower plate  1804  together. It should be appreciated that upper plate  1802  and lower plate  1804  may be drawn together using a variety of mechanisms such as toggle clamps, jack screws, hydraulic cylinders or any other known clamping and force producing devices.  
         [0095]    In this example technique, the film may first be tensioned by drawing upper plate  1802  and lower plate  1804  together. Adhesive  406  (or some other coupling mechanism) may be placed on the tensioned portion of diaphragm  104  and/or planar mounting surface  408  of frame  102 . While upper plate  1802  is clamped to lower plate  1804 , frame  102  may be placed into contact with diaphragm  104 . Once the adhesive has cured (or mechanical coupling completed), the threaded fasteners  1822  may be removed and upper plate  1802  may be separated from lower plate  1804 . It should also be appreciated that apertures  1806  and  1808  may be sized to allow entry of light waves to cure adhesive  406 , or to allow manipulation of some other coupling mechanism, if so desired. Depending on the specific configuration of the loudspeaker  100 , perimeter portion  818  of diaphragm  104  may be trimmed to remove any film extending beyond lip  306 .  
         [0096]    With reference to FIG. 19, another example film tensioning technique is depicted. The fixturing used to practice this example technique includes a fixture  1900  having a lower die  1902 , and an upper die  1904 . Fixture  1900  may function to restrain the periphery of diaphragm  104  and define a cavity  1906  between one side of the diaphragm  104  and lower die  1902 . A fluid source  1908  may supply pressurized fluid to cavity  1906 . Because lower die  1902  is constructed from a substantially rigid material, diaphragm  104  may elongate in tension as depicted in FIG. 19. Pressure is maintained within cavity  1906  while frame  102  is mechanically coupled with diaphragm  104 . Diaphragm  104  may be secured to frame  102  using any number of previously discussed bonding techniques including mechanical fasteners, radiation curable adhesives, multi-part epoxies, heat curable adhesives or pressure sensitive compounds.  
         [0097]    After diaphragm  104  has been fixed to frame  102 , upper die  1904  may be removed. If desired, excess diaphragm material extending beyond the perimeter of frame  102  may be removed.  
         [0098]    In this example technique, some of the initial tension generated by the pressurized fluid may relax during subsequent frame attachment process. Accordingly, a tension greater than the final desired tension may be initially induced via fluid source  1908  to assure that the film is properly tensioned during use.  
         [0099]    FIGS.  20 - 22  depict another example of fixturing used to tension diaphragm  104  prior to attaching diaphragm  104  to frame  102 . An example spider  2000  may operate in conjunction with an example base plate  2100  to tension diaphragm  104 . Spider  2000  may be placed on a first side of diaphragm  104  while base plate  2100  may be placed on the opposite side of the diaphragm  104 . Spider  2000  may function by converting an axial force applied in direction  2102  to a lateral tension produced in opposed directions  2200 .  
         [0100]    The illustrated spider  2000  is a generally pyramidal member having a hub  2002  positioned proximate to a truncated portion of the pyramid. A plurality of legs  2004  angularly extend from hub  2002 . Each of the legs  2004  include a body portion  2006  and a foot portion  2008 . Each foot portion  2008  radially extends from the distal end of each leg  2004 . A pad  2010  is coupled (as shown in FIG. 20) to a lower surface of each foot  2008 . Pads  2010  may be constructed from a high friction, elastomeric material that is suitable for gripping diaphragm  104  without causing damage to diaphragm  104 .  
         [0101]    The illustrated base plate  2100  is a generally rectangularly-shaped member having an aperture  2104  extending through the base plate  2100 . Aperture  2104  may be shaped similarly to the perimeter of frame  102  and sized such that frame  102  may be inserted into aperture  2104 . Base plate  2100  includes a low friction surface  2106  upon which diaphragm  104  may freely slide. As best shown in FIG. 21, each pad  2010  is supported by a portion of base plate  2100 .  
         [0102]    During tensioning, diaphragm  104  may be placed between base plate  2100  and spider  2000 . An axial force may be applied to spider  2000  in direction  2102 . Due to the angular orientation of legs  2004  relative to low friction surface  2106 , at least some of the axial force applied in direction  2102  may be converted to opposing forces in opposed directions  2200 . The opposed forces may tension diaphragm  104 . After tensioning, frame  102  is mechanically coupled to diaphragm  104  as previously discussed.  
         [0103]    [0103]FIG. 23, is yet another example system for loudspeaker  100  assembly. In this system, frame  102  may be elastically deformed prior to attachment of diaphragm  104 . The deformed frame  102  is represented in phantom lines at reference numeral  2300 . It should be appreciated that any number of force generating devices or tools such as jack screws, hydraulic rams or other force producing devices may be used to elastically deform frame  102  by inwardly deflecting radially extending flange  304  and lip  306  (FIG. 3) of frame  102 . Frame  102  may be maintained in the deformed state shown as  2300  while diaphragm  104  (FIG. 1) is attached to planar mounting surface  408  (FIG. 4).  
         [0104]    Once diaphragm  104  has been securely attached to frame  102 , the external forces deforming frame  102  may be released. Because frame  102  was elastically deformed, flange  304  and lip  306  have a tendency to spring-back to their originally undeformed state. This tendency is resisted by diaphragm  104 . Diaphragm  104  elongates as the deformed frame attempts to return to its undeformed state until an equilibrium is reached. Frame  102  may be constructed from steel, aluminum or any number of composite materials capable of being deformed. Materials having a modulus of elasticity less than 29,000 KSI are contemplated to provide a relatively large elastic deformation prior to yield. A large frame deformation is beneficial to account for elongation or deformation of adhesive  406  or other mechanical coupling used to bond diaphragm  104  to frame  102 .  
         [0105]    Frames constructed from molded plastic or composite materials offer additional opportunities to incorporate an arc or a bow across the frame as depicted in FIG. 24. In the embodiment shown, a loudspeaker  2400  includes a bowed frame  2402 . Frame  2402  manipulated to function as a spring washer tensioning diaphragm  104 .  
         [0106]    During assembly of loudspeaker  2400 , frame  2402  is forced to a substantially planar condition. Diaphragm  104  is coupled to frame  2402  while the frame is in the substantially flat condition. Once diaphragm  104  has been securely attached to frame  2402 , the external force maintaining frame  2402  in a substantially planar state is released. Because frame  2402  is elastically deformed, the frame has a tendency spring-back to its originally bowed shape. This tendency is resisted by diaphragm  104 . Diaphragm  104  elongates as frame  2402  attempts to return to its bowed shape until an equilibrium is reached. At equilibrium, diaphragm  104  is in a tensioned state and no further movement of diaphragm  104  and frame  2402  occurs.  
         [0107]    The bowed frame may be created using injection molding equipment such as that shown in FIG. 25. An injection mold  2500  includes an upper mold half  2502  and a lower mold half  2504 . A parting line  2506  runs along the length of frame  2402 . The position of parting line  2506  is defined by the interface position of upper mold half  2502  and lower mold half  2504 . The arc or bow is created by imparting a temperature differential between first mold half  2502  and second mold half  2504 . The use of a differential mold temperature to bow the part will conceptually work for all molding resins. However, semi-crystalline resins such as Polybutylene Terephthalate (PBT), Polyethylene Terephthalate (PET), nylons, Polypropylene (PP) and blends incorporating these materials will produce an especially pronounced bow.  
         [0108]    It should be appreciated that bowed frame  2402  may be produced from a mold having curved cavity surfaces machined within it as well. Standard temperature control techniques may then be used. Finally, it is contemplated that both concepts may be used in combination. Specifically, a mold having curved surfaces may be controlled to maintain mold half temperature differentials and obtain the desired bowed frame.  
         [0109]    With reference to FIGS. 26 and 27, an alternate frame  2600  is shown. Frame  2600  is preferably constructed from a reinforced plastic. Frame  2600  is a generally dish-shaped member having a base  2602  surrounded by a wall  2604  extending substantially orthogonally therefrom. Wall  2604  terminates at a radially extending flange  2606  which defines a substantially planar mounting surface  2700 . During assembly, diaphragm  104  is coupled to frame  2600  along planar mounting surface  2700 . Base  2602  includes a first surface  2702 , a second surface  2608  and a plurality of apertures  2610  extending therethrough. Apertures  2610  are positioned and sized to provide the desired passageways for air positioned between first  2702  and diaphragm  104  to flow.  
         [0110]    A plurality of magnets  2704  are integrally molded within frame  2600 . As best shown in FIG. 28, each of magnets  2704  includes a slot  2800  extending transversely across each end of magnet  2704 . FIG. 29 depicts slots  2800  filled with the composite material of frame  2600  after an over-molding process has been completed. Accordingly, slots  2800  perform a retention function to fix each of magnets  2704  within frame  2600 . Each magnet  2704  includes an upper surface  2802  positioned coplanar with surface  2702  of frame  2600 . Because magnets  2704  are recessed within body  2602 , the overall height of frame  2600  may be reduced to provide a low-profile frame and loudspeaker assembly.  
         [0111]    Additionally, the embedded magnet design provides a cost savings in relation to magnets  2704 . Magnets mounted to a steel frame must have closely controlled thicknesses to assure that the upper surface of each magnet is positioned at a proper distance from diaphragm  104 . Surfaces  2802  of magnets  2704  are designed to be substantially co-planar with surface  2702  of frame  2600  in the molding machine. During molding, the magnets are placed on a spring loaded tool  2900  (shown in phantom line in FIG. 29) to align each upper surface  2802  of magnets  2704  with each other in a single plane. Because injected resin flows around the magnets and the spring loaded tool, the thicknesses of magnets  2704  need not be closely controlled. For example, FIG. 29 depicts magnet  2704  having a first thickness  2902 . A magnet  2904  has a different thickness  2906 . The variation in magnet thickness is accommodated within the body of frame  2600 . A cost savings results by using magnets having a greater tolerance on the thickness dimension.  
         [0112]    As best shown in FIG. 26, a pair of electrical terminals  2612  are over-molded within frame  2600 . Each electrical terminal  2612  includes a male prong  2614  and a plate portion  2616 . A socket  2618  is integrally molded with frame  2600 . Socket  2618  includes a wall  2620  extending from surface  2608 . Wall  2620  surrounds male prongs  2614  and is shaped to mate with a female plug (not shown) used to electrically couple the loudspeaker to a power source.  
         [0113]    Each plate portion  2616  includes an aperture  2622  extending therethrough. Apertures  2622  extend through flange  2606  as well. After diaphragm  104  is coupled to mounting surface  2700 , an electrical connection is made between plate portions  2616  and conductor  106  of diaphragm  104 .  
         [0114]    With reference to FIG. 30, an alternate embodiment frame  3000  is depicted. Frame  3000  includes a pair of electrical terminals  3002  molded within a frame  3004 . Each electrical terminal  3002  includes male prong portions  3006  and inwardly extending portions  3008 . Inwardly extending portions  3008  are soldered to conductor  106  of diaphragm  104  after the diaphragm has been coupled to frame  3004 . In this manner, no additional fasteners or electrical interconnections need be made.  
         [0115]    To construct frame  2600  having the integrally molded metallic components as previously discussed, an over-molding technique is preferably used. Magnets  2704  and electrical terminals  2612  are first placed within an open injection mold cavity. Magnets  2704  and electrical terminals  2612  are positioned within the mold to assure that molten plastic resin covers at least a portion of each metallic component to retain it within frame  2600 . The injection mold also includes features to mask off portions of the metallic components so selected portions are not contacted by the molten resin. The mold is closed and resin is injected to fill the cavity. Upon completion of this process, magnets  2704  and electrical terminals  2612  are fixed within frame  2600 . Magnets  2704  and electrical terminals  2612  include exposed surfaces for the purpose previously described.  
         [0116]    With reference to FIGS.  31 - 33 , an alternate embodiment loudspeaker is depicted at reference numeral  3100 . Loudspeaker  3100  includes a casement  3102  having a diaphragm  3104  coupled thereto. Loudspeaker  3100  also includes a frame  3106  having a plurality of magnets  3108  coupled to a body portion  3110  of frame  3106 .  
         [0117]    Casement  3102  includes a pair of generally parallel side rails  3112  orthogonally intersected by a pair of generally parallel end rails  3114 . Diaphragm  3104  is embedded within a portion of each of side rail  3112  and end rail  3114 . Casement  3102  is coupled to frame  3106  to position diaphragm  3104  a predetermined distance from magnets  3108 . One skilled in the art will appreciate that casement  3102  may be coupled to frame  3106  using a variety of techniques such as ultrasonic welding, snap fit connections, mechanical fasteners, adhesive bonding or any other suitable connection method.  
         [0118]    One type of securing device is shown in FIG. 35. An alternate loudspeaker  3500  includes a retainer  3502 , a casement  3504  and a frame  3506 . Casement  3504  includes a flange  3508  radially protruding from the perimeter of casement  3504 . Similarly, frame  3506  includes a flange  3510  radially extending from a body portion  3512  of frame  3506 . Retainer  3502  has a generally c-shaped cross section engaging flanges  3508  and  3510  to interconnect casement  3504  and frame  3506 .  
         [0119]    As shown on the right side of FIG. 35, retainer  3502  may also include loudspeaker mounting provisions such as a flange  3514  having an aperture  3516  extending therethrough. The use of the loudspeaker mounting provision on retainer  3502  improves design flexibility. For example, a generic frame and magnet assembly may be designed for use with a variety of differently shaped retainers configured to mount loudspeakers within certain vehicles or enclosures. Preferably, use of the common or generic components will reduce cost and product proliferation.  
         [0120]    To assemble a loudspeaker equipped with retainer  3502 , frame  3506  and casement  3504  are placed within an injection mold cavity. Molten resin is injected within the cavity to form retainer  3502 . After solidification of the resin, completed loudspeaker  3500  is ejected from the mold cavity.  
         [0121]    With specific reference to FIGS. 36 and 37, an alternate loudspeaker  3600  includes a casement and diaphragm subassembly  3602  and a frame and magnet assembly  3604 . Casement and diaphragm subassembly  3602  includes a casement  3606  and diaphragm  3608 . Casement  3606  includes a pair of side rails  3610  and a pair of end rails  3612  interconnected to one another to define an aperture  3614 . Side rails  3610  and end rails  3612  include apertures  3615  extending therethrough.  
         [0122]    Frame and magnet subassembly  3604  includes a frame  3616  having a body  3617  with a plurality of stakes  3618  protruding therefrom. The frame  3616  also includes a plurality of catches  3620  extending from body  3617 . Catch  3620  includes a barb  3622 . During assembly of casement and diaphragm subassembly  3602  to frame and magnet subassembly  3604 , barb  3622  engages casement  3606 . Also, stakes  3618  protrude through apertures  3615 . A subsequent heat staking or melting process deforms the ends of stakes  3618  to form a cap  3700  and further couple casement and diaphragm subassembly  3602  to frame and magnet subassembly  3604 .  
         [0123]    To manufacture loudspeaker  3600 , an injection mold  3400  as shown in FIG. 34 is used. Injection mold  3400  includes a stationary plate  3402  and a movable plate  3404 . Stationary plate  3402  and movable plate  3404  define a cavity  3406  in communication with a gate  3408 . Gate  3408  serves as an inlet for a molten resin material  3410 . Movable plate  3404  includes a gas permeable plate  3412  inserted within a gas impermeable die body  3414 . A vacuum channel  3416  is positioned along a back surface  3418  of plate  3412 . Vacuum channel  3416  is coupled to a vacuum source (not shown). Movable plate  3404  includes a plurality of pins  3420  extending upwardly from a substantially planar surface  3421 . Each pin  3420  includes an upper surface  3422  that engages a lower surface  3424  of stationary plate  3402  when injection mold  3400  is closed.  
         [0124]    An oversized, work-in-progress, diaphragm  3425  is inserted within injection mold  3400 . Oversized diaphragm  3425  includes a center portion  3426  surrounded by a perimeter portion  3428 . Perimeter portion  3428  includes an offage portion  3430  extending beyond the edge of cavity  3406 . Finished diaphragm  3608 , shown in FIGS. 36 and 37, is created by trimming offage portion  3430  from oversized diaphragm  3425 . Diaphragm  3608  includes a plurality of apertures  3432 . Upon insertion of diaphragm  3425 , the plurality of pins  3420  extend through apertures  3432  and diaphragm  3425  rests on planar surface  3421 . During manufacture of the casement and diaphragm subassembly, perimeter portion  3428  of diaphragm  3425 , specifically offage portion  3430 , is clamped between stationary plate  3402  and movable plate  3404  of injection mold  3400 . After perimeter portion  3428  is clamped, center portion  3426  is displaced to introduce a tension to diaphragm  3425 . While the diaphragm is under tension, molten plastic is injected into cavity  3406  to form side rails  3610  and end rails  3612 . During the injection process, perimeter portion  3428  partially melts and bonds with the material forming casement  3606 . The casement material is then cooled and solidified. The tensioned diaphragm  3608  molded to casement  3606  is now removed from the injection mold. Offage portion  3430  is trimmed to produce the final casement and diaphragm assembly  3602  as shown in FIG. 36. The casement and diaphragm subassembly may be utilized as a component within many different speaker designs including loudspeakers having metal frames as previously described or molded frames similar to frame  3616 .  
         [0125]    It should be appreciated that a number of different devices such as pins, clamps, notches or stops may be used to temporarily fix offage portion  3430  while center portion  3426  is tensioned. One specific retention device is shown in FIG. 38. A pin  3800  extends through an aperture  3802  extending through diaphragm  3425  located in offage portion  3430 .  
         [0126]    With continued reference to FIG. 38, a portion of an alternate injection mold is depicted at reference numeral  3804 . Mold  3804  includes a stationary half  3806  having a ridge  3808  protruding downwardly therefrom. Mold  3804  also includes a movable half  3810  having a trough  3812  extending about the periphery of the mold. During mold closure, ridge  3808  contacts diaphragm  3425  and forces diaphragm  3425  to enter trough  3812 . During this process, diaphragm  3425  is tensioned and retained under tension. To assure a sufficient amount of tension is generated in diaphragm  3425 , optional locating pins  3800  may be positioned outboard of the ridge and trough to retain the perimeter portion of diaphragm  3425  during tensioning. One skilled in the art will appreciate that a variety of devices such as clamps, pins or stops may be used to locate and retain the perimeter portion of the diaphragm  3425  during mold closure and tensioning. As previously mentioned, molten resin is then injected to form casement  3606 .  
         [0127]    With reference to FIG. 39, an alternate embodiment loudspeaker is depicted at reference numeral  3900 . Loudspeaker  3900  includes a frame  3902  having a plurality of magnets  3904  coupled to a body portion  3906  of frame  3902 . An elastomeric bumper  3908  is coupled to frame  3902 . Elastomeric bumper  3908  extends substantially about the perimeter of frame  3902 . Elastomeric bumper  3908  is depicted as a solid elastomeric member coupled to the perimeter portion of the frame. It should be appreciated that bumper  3908  may also be constructed from a closed cell foam or other resilient material.  
         [0128]    Elastomeric bumper  3908  may be conventionally attached to frame  3902  using adhesives or mechanical fasteners. Elastomeric bumper  3908  may also be molded to frame  3902  using an injection mold. In one embodiment, the frame is constructed from injection molded plastic. Frame  3902  is formed first in the mold. A second elastomeric material is injected to mold bumper  3908  to frame  3902 . Alternatively, bumper  3908  may be formed in a different mold if economically beneficial.  
         [0129]    During assembly of loudspeaker  3900 , bumper  3908  is compressed by applying an external force in the direction of a line  3910 . The compression force is maintained while a diaphragm  3912  is coupled to bumper  3908 . Once diaphragm  3912  is fixed to bumper  3908 , the external force compressing bumper  3908  is removed. Because bumper  3908  is an elastomeric member, bumper  3908  tends to return to its originally undeformed shape but is resisted by diaphragm  3912 . An equilibrium condition is reached resulting in tensioning diaphragm  3912 . One skilled in the art will appreciate that bumpers  3908  may extend about the entire periphery of frame  3902  or may also be represented by plurality of small elastomeric portions positioned along to opposite sides of frame  3902 .  
         [0130]    [0130]FIG. 40 shows an alternate embodiment loudspeaker  4000  including hollow elastomeric bumpers  4002  coupled to a perimeter portion of frame  3902 .  
         [0131]    During assembly of loudspeaker  4000 , bumpers  4002  are compressed by applying an external force in the direction of a line  4004 . The compression force is maintained while diaphragm  3912  is coupled to bumpers  4002 . Once diaphragm  3912  is fixed to bumpers  4002 , the external force compressing bumpers  4002  is removed. Because bumpers  4002  are elastomeric members, bumpers  4002  tend to return to their originally undeformed shape. This tendency is resisted by diaphragm  3912 . An equilibrium condition is reached resulting in tensioning diaphragm  3912 .  
         [0132]    While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that other embodiments and implementations are possible that are within the scope of this invention. Accordingly, the invention is not restricted except in light of the attached claims and their equivalents.