Patent Publication Number: US-9900696-B2

Title: Wide-range, wide-angle loudspeaker driver

Description:
RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 13/888,836, filed on May 7, 2013, which claims priority to U.S. Provisional Application Ser. No. 61/688,244 filed on May 9, 2012. These applications are incorporated herein by reference, in their entireties. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to loudspeaker drivers, and more particularly to loudspeaker drivers of the air motion transformer type, also generally known to those skilled in the art as “AMT” loudspeaker drivers. 
     BACKGROUND 
     In U.S. Pat. No. 3,636,278 inventor Oskar Heil described a number of embodiments of AMT loudspeaker drivers, in which audible sound is produced through the immersion of a thin, flexible, folded diaphragm into a magnetic field, in such a way that when alternating audio-frequency electric current flows through conductors etched onto the folded diaphragm, the adjacent portions of the folded diaphragm will either move away from each other, or toward each other, depending on the relative direction of electric current flow in each diaphragm moving section. 
     This movement of the diaphragm sections results from the Lorentz Force, generally known to those skilled in the art, which is caused by the interaction between the applied magnetic field and the electric current flow in the diaphragm conductors, thus producing an alternating increase or decrease in air pressure in the semi-confined air spaces between the diaphragm layers, which causes sound waves to emanate from the front and rear openings of the semi-confined air spaces which are bound by the adjacent diaphragm portions, the folds between the diaphragm portions, and the various air-sealing surfaces located near the ends of the adjacent diaphragm portions. 
     In related art, the aforementioned rectangular folded diaphragm, with its attached electrical conductors, is typically produced by using a photo-chemical process to etch an electrical signal path into an aluminum foil layer which has been laminated onto a very thin, rectangular plastic sheet, such as that shown in FIG. 1A of U.S. Pat. No. 3,832,499. 
     This rectangular sheet, with its attached and straight, photo-etched conductors, in related art, is then folded into a narrow, rectangular, accordion bellows-like shape, thus producing a plurality of long, narrow, semi-confined air spaces located between the moving, adjacent portions of the folded diaphragm. 
     The resulting relatively long, straight, narrow folded diaphragm, after being placed in the appropriate magnetic field of a completed loudspeaker driver, is then typically mounted into a loudspeaker, with the longer dimension running in the vertical direction, and the shorter dimension running in the horizontal direction. The resulting long, narrow, straight, folded diaphragm shape, in related art, has a number of substantial and heretofore unavoidable drawbacks, including extremely limited vertical dispersion at the higher audio frequencies, especially above 2 Kilohertz, and a practical limit on the maximum length of the longer dimension of the folded diaphragm, which is typically not much longer than eight inches or so due to the handling problems caused by the use of extremely thin diaphragm material, which is typically only about 1/1000 th  of an inch thick. 
     The resulting limitation on the maximum practical length of the long, straight, rectangular folded diaphragm, in related art, also limits the amount of total effective moving surface area available, which in turn limits both the low frequency cut-off of the device to about 800 Hertz, and also limits the maximum power handling capacity of the device because of the limited heat dissipation capability of the relatively small electrical conductor total surface area. 
     The folded diaphragm, in related art, is typically limited in its narrower, horizontal dimension, to about one inch or less, to allow for high-frequency dispersion to exist in the horizontal direction, which is generally about plus-or-minus sixty degrees or less at the higher audio frequencies. 
     In the related art of U.S. Pat. No. 3,636,278 FIG. 12a and FIG. 12b, inventor Oskar Heil described a type of AMT diaphragm configuration in which the angle of the folds between adjacent folded diaphragm sections is varied between the inner and outer folds, which allows for the overall folded diaphragm shape to follow a varying path, even though each individual moving section of diaphragm and conductor only follows a straight path. The resulting overall diaphragm shape, however, has the substantial disadvantage of having adjacent sections of moving diaphragm area which are not always generally parallel to each other, and which vary in their geometry between the inner and outer semi-confined airspaces, which causes substantial audio distortion due to non-linearities in the non-optimally acoustically loaded inner versus outer moving diaphragm surfaces. 
     The resulting moving diaphragm sections of the related art as shown by FIG. 12a and FIG. 12b of U.S. Pat. No. 3,636,278 are also quite small in their individual effective moving areas, the sum total of which typically comprises much less than one-fourth of the total surface area of the etched diaphragm sheet before being folded. 
     SUMMARY 
     Accordingly, an air motion transformer loudspeaker driver is provided. In accordance with the principles of the present disclosure the air motion transformer loudspeaker driver includes a plurality of diaphragm layers having electric conductors. Each of the diaphragm layers defines a surface having at least one curved portion. Each such curved portion has a corresponding axis of curvature being generally perpendicular to the surface of the diaphragm layer at the location of the curved diaphragm portion, or curved electric conductor portion, or curved diaphragm edge portion. A “perpendicular axis of curvature” to curved lines on a surface, in this case, is defined as an axial line drawn along a vector which is considered mathematically “normal” to, or generally perpendicular to, said lines on a surface at the point or points of said curvature, as conceptually shown in  FIG. 5B . 
     The present invention solves the numerous problems, of related art, which include limited vertical and horizontal dispersion, limited low-frequency cut-off, and limited maximum power handling capacity, through the introduction of a novel and extremely effective curved diaphragm geometry, which allows for several substantial improvements, such as unlimited horizontal dispersion of sound, which is uniform at up to 360 degrees at all audio frequencies, and allows for greatly improved vertical dispersion at high audio frequencies, and which also allows for a much deeper low frequency cut-off, which can be several octaves lower than that in related art, and also allows for much higher maximum power handling capacity, which can be several times higher than the power handling capacity in related art. 
     Unlike related art, in which the diaphragms with electric conductors are created using straight-line configurations, which are then folded into a rectangular, straight, accordion bellows-like shape, the present invention constructs the diaphragm layers and attached electric conductors in a novel, curved configuration, with the axis of curvature being perpendicular to the surfaces of the diaphragm layers at the point or points of curvature. The curved diaphragm layers can then either be stacked or folded over each other to form a diaphragm stack, utilizing curved inner and outer support/sealing members and small pieces of alignment material placed between adjacent diaphragm layers, which allows for proper spacing and partial sealing between each diaphragm layer, and also allows for each diaphragm layer and conductor to follow a non-straight path, which can be a circle, any other closed-loop path such as an oval, etc., or any arbitrary arc-shaped segment, or any other generally non-straight overall path. 
     In addition to solving the numerous problems associated with the typically long, straight, folded rectangular diaphragm shapes as utilized in related art, the novel, curved construction of the present invention also avoids the problems associated with the diaphragm configuration as shown in other related art such as that illustrated by FIG. 12a and FIG. 12b of U.S. Pat. No. 3,636,278. 
     In the present invention, the resulting curved diaphragms and conductors may be built in nearly any overall size or shape desired, up to several feet or more in overall width, which eliminates the aforementioned maximum practical length limitation exhibited by the related art which generally suffers from severe “beaming” of the high audio frequencies in the vertical direction. 
     In the present invention, the curved diaphragm layer construction may also be customized to appropriately cover nearly any audio frequency sub-range desired, without any negative consequences in horizontal or vertical sound dispersion, power handling capacity or low frequency cut-off limits. 
     As an added benefit, the present invention, in addition to utilizing thin, flexible sheets for the diaphragm layers, may also be constructed using rigid or semi-rigid moving sections of diaphragm layers, due to its novel construction methods, with each of said moving diaphragm section able to be completely surrounded by compliant structures to allow for substantial and nearly “pistonic” diaphragm section movement. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is an external side-view of the preferred embodiment of the device; 
         FIG. 1B  shows a cross-section of the device of  FIG. 1A , taken along the view line as shown in  FIG. 1C ; 
         FIG. 1C  shows a top-view of the device of  FIG. 1A ; 
         FIG. 2A  shows a vertical cross-section of the inner pole piece of the device of  FIG. 1A , taken along the view line shown in  FIG. 2B ; 
         FIG. 2B  shows a vertical cross-section of the inner pole piece of the device of  FIG. 1A , taken along the view line shown in  FIG. 2A ; 
         FIG. 3A  is an external side-view of the outer pole pieces of the device of  FIG. 1A ; 
         FIG. 3B  shows a vertical cross-section of the outer pole pieces shown in  FIG. 3A , taken along the view line shown in  FIG. 3A ; 
         FIG. 4A  shows a vertical cross-section of the upper magnet support structure and magnets of the device shown in  FIG. 1A , taken along the view line as shown in  FIG. 4C ; 
         FIG. 4B  is an external side-view of the upper magnet support structure and magnets of the device shown in  FIG. 1A ; 
         FIG. 4C  shows a top-view of the lower magnet support structure as shown in  FIG. 4B , with the location of the internal magnets as shown by the dotted lines; 
         FIG. 5A  shows the top-view of one pre-assembly diaphragm layer of the diaphragm stack as shown in  FIG. 1B , also showing the optional pleated areas using dotted lines.  FIG. 5B  shows a conceptual, perspective view of an “axis of curvature” being generally perpendicular to curved lines on the surface or edge of a diaphragm layer as shown on  FIG. 5A ; 
         FIG. 6  shows a vertical cross-section of an alternative embodiment of the device; 
         FIGS. 7A and 7B  show the outer support/sealing rings of the diaphragm stack of the device as shown in  FIG. 1B ; 
         FIGS. 7C and 7D  show the inner support/sealing rings of the diaphragm stack of the device as shown in  FIG. 1B ; 
         FIG. 8  shows an exploded, conceptual view of the present invention, exhibiting radially-charged magnetic rings; 
         FIG. 9A  shows the external side-view of the diaphragm stack of the device shown in  FIG. 1A ; 
         FIG. 9B  shows a top-view of a single pre-assembly diaphragm layer of the present invention as shown in  FIG. 1A ; 
         FIG. 10  shows one possible pre-assembly layout of a 24-layer diaphragm stack for a circular-loop embodiment of the device; 
         FIG. 11A  shows the external front-view of a semi-circular embodiment of the device; 
         FIG. 11B  shows the external top-view of a semi-circular embodiment of the device; 
         FIG. 12A  shows the external rear-view of a semi-circular embodiment of the device; 
         FIG. 12B  shows the external bottom-view of a semi-circular embodiment of the device; 
         FIG. 13A  shows a rear-view cross-section of the device of  FIG. 12A , with the view line as shown in  FIG. 13B ; 
         FIG. 13B  shows a top-view cross-section of the device of  FIG. 12A , with the view line as shown in  FIG. 13A ; 
         FIG. 14A  shows the external rear view of the inner pole piece of the device of  FIG. 12A ; 
         FIG. 14B  shows the horizontal cross-section of  FIG. 14A , with the view line as shown in  FIG. 14A ; 
         FIG. 15A  shows the external front view of the outer pole pieces of the device of  FIG. 12A ; 
         FIG. 15B  shows the horizontal cross-section of  FIG. 15A , with the view line as shown in  FIG. 15A ; 
         FIG. 16A  shows the front external view of the upper and lower magnet support structures and magnets of the device of  FIG. 12A ; 
         FIG. 16B  shows the top-view of the lower support structure of  FIG. 16A , with the location of the internal magnets as shown by the dotted lines; 
         FIG. 17A  shows the rear external view of the upper and lower magnet support structures and magnets of the device of  FIG. 12A ; 
         FIG. 17B  shows the top-view of the lower support structure of  FIG. 17A , with the location of the internal magnets as shown by the dotted lines; 
         FIG. 18A  shows the vertical rear cross-section of  FIG. 13A , with the view line as shown in  FIG. 13B ; 
         FIG. 18B  shows the external top-view of the outer support/sealing members of the diaphragm stack as shown in  FIG. 20A ; 
         FIG. 19A  shows the vertical rear cross-section of  FIG. 13A , with the view line as shown in  FIG. 13B ; 
         FIG. 19B  shows the external top-view of the inner support/sealing members of the diaphragm stack as shown in  FIG. 20A ; 
         FIG. 20A  shows the external front-view of the diaphragm stack of the device shown in  FIG. 11A ; 
         FIG. 20B  shows the top-view of one pre-assembly diaphragm layer of the diaphragm stack as shown in  FIG. 20A ; 
         FIG. 21  shows one possible pre-assembly layout of a section of a diaphragm stack for a semi-circular embodiment of the device; 
         FIG. 22  shows a partial section of a vertical stack of alternating sections of diaphragm stacks and magnet sections of a semi-circular embodiment of the device; 
         FIG. 23  shows a vertical cross-section of an alternative embodiment of the present invention, using rigid or semi-rigid sections of diaphragm layers with flexible surround elements, and using an alternative magnet support structure; 
         FIG. 24A  shows an external top-view of an alternative, closed-loop diaphragm layer shape; and 
         FIG. 24B  shows an external top-view of an alternative, arc-shaped diaphragm layer section shape. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present disclosure may be understood more readily by reference to the following detailed description of the disclosure taken in connection with the accompanying drawing figures, which form a part of this disclosure. It is to be understood that this disclosure is not limited to the specific devices, methods, conditions or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only and is not intended to be limiting of the claimed disclosure. Also, as used in the specification and including the appended claims, the singular forms “a,” “an,” and “the” include the plural, and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It is also understood that all spatial references, such as, for example, horizontal, vertical, top, upper, lower, bottom, left and right, are for illustrative purposes only and can be varied within the scope of the disclosure. For example, the references “upper” and “lower” are relative and used only in the context to the other, and are not necessarily “superior” and “inferior”. 
     The following disclosure includes a description of a loudspeaker driver device which can be used to produce wide-range, wide-angle, high-quality audible sound, of the type generally known to those skilled in the art as an “Air Motion Transformer”, or “AMT” type of device. The disclosure also includes a description of related methods of employing the disclosed loudspeaker device. Alternate embodiments are also disclosed. Reference will now be made in detail to the exemplary embodiments of the present disclosure, which are illustrated in the accompanying figures. Turning now to  FIGS. 1-24 , there are illustrated components of a loudspeaker device and embodiments in accordance with the principles of the present disclosure. 
     The present invention relates to a loudspeaker driver device which can be used to produce wide-range, wide-angle, high-quality audible sound, of the type generally known to those skilled in the art as an “Air Motion Transformer”, or “AMT” type of device, in which an alternating electrical audio signal is sent to a number of generally parallel diaphragm surfaces, with semi-confined air spaces located between the diaphragm surfaces, said airspaces being open at alternating inner and outer edges between the adjacent diaphragm layers. 
     The adjacent diaphragm portions have conductors on their surfaces, or embedded in or under their surfaces, or the diaphragm layers can themselves be made of electrically conductive materials. 
     A magnetic field originates from permanent magnets, or electro-magnets, which are arranged to produce an appropriate magnetic field in the area in which the diaphragm moving surfaces are located, in such a way that the magnetic field flux lines intersect the current flow of the diaphragm conductors at essentially right angles, causing adjacent diaphragm layers to move toward each other, or away from each other, due to the Lorentz Force exerted on the electrons moving in the conductors, depending on the direction of current flow for each diaphragm layer. 
     A positive signal voltage applied to the electric leads of the device causes air to move radially outward from the front, or outer, surface of the device, while an applied negative signal voltage causes air to move radially inward toward the rear, or center, of the device. The front or rear, or outer or inner, sound-producing areas of the device may be sealed, stuffed, ported, horn-loaded or otherwise vented, or completely or partially sealed. 
     In such a way, a very high-quality loudspeaker driver can be achieved in the present invention, exhibiting an extremely wide frequency range, extremely wide vertical and horizontal dispersion angles, and high efficiency, using very simple construction methods and at reasonable manufacturing costs. 
     In the present invention, the generally curved diaphragm layers  10  of the preferred 360-degree embodiment as shown in  FIGS. 1A-C , and as also shown in the alternative embodiment of the 180-degree version of  FIGS. 11A &amp;B, with an axis of curvature  29  as conceptually shown in  FIG. 5B , are arranged in a plurality of generally parallel layers  10 , including the semi-confined airspaces bound between each diaphragm layer  10 , with each diaphragm layer having a current flow direction which is generally perpendicular to the radial magnetic field direction, and opposite to that of the layers adjacent to it, as shown by the curved arrows marked with the letter “I” in the exploded, conceptual view of  FIG. 8 . The structure of diaphragm layers  10  may range from 1 degree to 360 degrees. 
     The width of each diaphragm layer  10  across one set of electric conductors  13  is typically about one-half inch, but can be greater or lesser to accommodate various audio frequency sub-ranges. The thickness of the diaphragm substrate is typically about 1/1000 th  of an inch or less. The thickness of the typically aluminum electrical conductor traces  13  is typically about 1/1000 th  of an inch or less. It is contemplated that aluminum electrical conductor traces  13  can be of varied thickness depending on a particular application. 
     As shown in  FIGS. 1A-C , and conceptually illustrated in the exploded view of  FIG. 8 , the preferred embodiment may be assembled by combining the required individual components including the magnets  4 , the magnet support structures  1 , the inner sealing/support rings  16 , the outer sealing/support rings  15 , the diaphragm layers  10 , the small pieces of alignment material  17 , the inner pole pieces  7  and the outer pole pieces  2  as shown in  FIG. 1B , using adhesives, screws, magnetic attraction or by any other suitable means generally known to those skilled in the art. An alternative embodiment of the device may also be assembled as shown in  FIG. 23 . 
     A user-replaceable diaphragm stack  5  can be first and separately be constructed, as shown in the 360-degree, preferred embodiment of  FIG. 9A , and in the alternative 180-degree embodiment of  FIG. 20A , and in the conceptual exploded view of  FIG. 8 , and in the alternative embodiment as shown in  FIG. 23 , by placing an inner support/sealing ring  16  along with spaced, small pieces of alignment material  17  near the diaphragm layer edge opposite from the inner support/sealing ring  16  in a semi-confined air space between adjacent diaphragm layers, and then placing an outer support/sealing ring  15  along with spaced, small pieces of alignment material  17  near the diaphragm layer edge opposite from the outer support/sealing ring  15  in the semi-confined airspace between the subsequent adjacent diaphragm layer, and so on, until the desired number of layers has been built up, typically to about a total of twenty-four diaphragm layers or so, keeping the overall diaphragm stack  5  height to typically around one inch or less. 
     The overall width of the diaphragm stack  5  can be designed to be of nearly any size desired, and it can be made larger or smaller in overall width or height to accommodate various audio frequency ranges. As shown in  FIG. 5 , electrical connections can be made at connection points  11  for each diaphragm layer, taking care to ensure that current flows in opposite directions for adjacent diaphragm layers, as shown by the curved arrows in the exploded view of  FIG. 8 . 
     Alternatively, electrical connections between diaphragm layers can also consist of simple folds made between continuous diaphragm layers which have been constructed from a single sheet of laminated and subsequently photo-etched diaphragm/conductor material, as shown in  FIG. 10 . 
     As shown in  FIGS. 7A-D , and in the alternative embodiments of  FIG. 18B  and  FIG. 19B , the inner and outer sealing/support rings  16  and  15  respectively can be made from a wide variety of suitable materials, such as 3-D printed or injection molded thermoplastic. 
     The inner and outer sealing/support rings  16  and  15  each may include cone-shaped cross-section elements  23 , the purpose of which are to minimize any acoustic standing waves that might otherwise exist inside the semi-confined air spaces between each diaphragm layer  10 . 
     The inner and outer support/sealing rings  16  and  15  of the alternative 180-degree embodiments of  FIG. 18B  and  FIG. 19B  may also include generally short, flat extensions  24  which seal the air spaces near the ends of the diaphragms in the arc-shaped embodiments as shown in  FIGS. 13A &amp;B. 
     The completed diaphragm stack  5  of  FIG. 9A , is a self-supporting structure which can then be placed in the magnetic field of the preferred embodiment of  FIG. 1A  by first inserting the lower end of the inner pole piece  7  shown in  FIG. 2A  into the center hole in the lower magnet support structure  1  shown in  FIG. 4B , then inserting the magnets  4  into the holes in the lower magnet support structure  1  as shown in  FIG. 4B , allowing the south poles of the magnets to be attracted toward the center pole piece  7 , and taking care to align the north and south poles of the magnets  4  as shown in  FIGS. 4B &amp;C. 
     The completed diaphragm stack  5  can then be slid down over the inner pole piece  7 , taking care to align any inner diaphragm leads  11  with the slot  9  in the inner pole piece  7 . The upper magnet support structure  1  shown in  FIG. 4A  can then be slid down over the inner pole piece  7 , using the smooth, flat, upper surface of  FIG. 4B  and the smooth, flat, lower surface of  FIG. 4A  to form an air-tight seal between the inner and outer surfaces of the diaphragm stack  5 . 
     Magnets  4  can then be inserted into the holes in the upper magnet support structure  1  shown in  FIG. 4A , allowing the south poles of the magnets to be attracted toward the inner pole piece  7 , and taking care to align the north and south poles of the magnets  4  as shown in  FIG. 4A . Alternatively, the magnets  4  may also be magnetized after being inserted into the magnet support structures  1 . 
     The outer pole pieces  2  shown in  FIGS. 3A &amp;B can then be placed onto the exposed north poles of the magnets  4  of both the upper and lower magnet support structures  1  shown in  FIGS. 1A &amp;B, using magnetic attraction to keep the outer pole pieces  2  in place, as well as using any appropriate additional fixing means, generally known to those skilled in the art, that might be necessary. 
     As shown in  FIG. 1C , the upper and lower surfaces of the magnet support structures  1  of the assembled preferred embodiment shown in  FIG. 1A  can be left open, sealed, ported, dampened, horn-loaded or otherwise vented by any suitable means, such as by a simple plate  26  as shown in the alternative embodiment of  FIG. 23 , or by any other desired combination of ports, vents, horn flares, surfaces or other wave-guiding, sealing or dampening materials, etc., generally known to those skilled in the art. 
     The construction method for the alternative, 180-degree embodiment as shown in  FIGS. 11A &amp;B is very similar to the above construction method for the preferred embodiment of  FIG. 1A . 
     The alternative, 180-degree embodiment of  FIG. 11A  can be assembled by first and separately constructing the diaphragm stack  5  of  FIG. 20A , either through the stacking of individual diaphragm layers  10  of  FIG. 20B , or through the alternative method of diaphragm stack folding shown in  FIG. 21 . 
     The completed diaphragm stack  5  of  FIG. 20A , is a self-supporting structure which can then be placed in the magnetic field of the 180-degree alternative embodiment of  FIG. 11A  by first inserting the lower end of the inner pole piece  7  shown in  FIGS. 14A &amp;B and  FIG. 12A  into the guide channels  28  of the lower magnet support structure  1  as shown in  FIG. 16B  and  FIG. 17B , then inserting the magnets  4  into the holes in the lower magnet support structure  1  as shown in  FIG. 16B  and  FIG. 17B , allowing the south poles of the magnets to be attracted toward the center pole piece  7 , and taking care to align the north and south poles of the magnets  4  as shown in  FIGS. 16A &amp;B and  FIGS. 17A &amp;B. 
     The completed diaphragm stack  5  can then be slid down over the inner pole piece  7 . The upper magnet support structure  1  shown in  FIG. 16A  and  FIG. 17A  can then be slid down over the inner pole piece  7 , using the smooth, flat, upward and downward-facing surfaces shown in  FIG. 16A  and  FIG. 17A  to form an air-tight seal between the front and rear surfaces of the diaphragm stack  5  of  FIG. 20A . 
     In addition, the short extensions  24  on the inner and outer support/sealing rings  16  and  15  respectively of  FIG. 14B  and  FIG. 15B , also help to form an air-tight seal between the front and rear surfaces of the diaphragm stack  5  of  FIG. 20A . 
     Magnets  4  can then be inserted into the holes in the upper magnet support structure  1  shown in  FIG. 16A  and  FIG. 17A , allowing the south poles of the magnets to be attracted toward the inner pole piece  7 , and taking care to align the north and south poles of the magnets  4  as shown in  FIGS. 16A &amp;B and  FIGS. 17A &amp;B. 
     The outer pole pieces  2  shown in  FIG. 11A  and  FIGS. 15A &amp;B can then be placed onto the exposed north poles of the magnets  4  of both the upper and lower magnet support structures  1  shown in  FIGS. 11A &amp;B and  FIG. 13A , using magnetic attraction to keep the outer pole pieces  2  in place, as well as using any appropriate additional fixing means, generally known to those skilled in the art, that might be necessary. 
     As shown in  FIG. 12A  and  FIG. 12B , the front or rear, or upper or lower, smooth surfaces of the magnet support structures  1  of the assembled alternative 180-degree embodiment shown in  FIG. 11A  can be left open, sealed, ported, dampened, horn-loaded or otherwise vented by any suitable means by any desired combination of ports, vents, horn flares, surfaces or other wave-guiding, sealing or dampening materials, etc., generally known to those skilled in the art. 
     For all of the embodiments of the present invention, the magnets  4  as shown in  FIGS. 4A-C ,  FIGS. 16A &amp;B,  FIGS. 17A &amp;B, and  FIG. 23 , can be made of any suitable permanent magnet material such as ceramic, ferrite, neodymium-iron-boron, alnico, samarium cobalt, or can be comprised of electro-magnets, or any suitable combination of permanent magnet material, magnetic flux-directing material, or electro-magnetic components, and may be shaped as cubes, rectangles, wedges, tubes, rings or any other suitable shape which results in the required magnetic field shape. 
     There may exist, in all embodiments of the present invention, a number of alternative means employed for directing, shielding or otherwise influencing the direction of the magnetic field flux lines within or around the device, as illustrated by  FIGS. 1A &amp;B,  FIG. 11A ,  FIG. 13A ,  FIG. 14A  and  FIG. 23 , as well as many other possible variations generally known to those skilled in the art, all of such variations falling within the scope of the spirit of the present invention. 
     As shown in  FIGS. 2A &amp;B,  FIGS. 3A &amp;B,  FIGS. 14A &amp;B and  FIGS. 15A &amp;B, the inner and outer pole pieces  2  and  7  for all embodiments can be made of steel or any other suitable material with the proper magnetic characteristics known to those skilled in the art. The outer pole pieces  2  have openings in them  3  which allow for sound waves to pass through, while also concentrating the magnetic field flux lines toward the diaphragm stack  5 . Likewise, the inner pole pieces  7  have openings  8  in them to allow for sound waves to pass through, and can also concentrate the magnetic flux lines toward the diaphragm stack  5 . 
     As an alternative embodiment, such as that shown in  FIG. 23 , the device may also be constructed without the use of inner or outer pole pieces if desired, in some instances using magnetic flux-return plates  26  made of steel or any other appropriate material or configuration generally known to those skilled in the art, to help direct an appropriate amount of magnetic flux through the diaphragm stack  5 . 
     As shown in  FIG. 5 ,  FIG. 20B ,  FIG. 10  and  FIG. 21 , the electric conductors  13  for all embodiments can be made of any suitable electrically conductive material such as metal, conductive plastic, carbon-based materials, conductive paint, or aluminum foil which has been bonded onto any suitable diaphragm substrate material such as polyimide, polyethylene naphthalate, Mylar, etc., which are generally known to those skilled in the art. 
     The electrically conductive elements  13  can be sized in thickness, width, location and quantity in order to provide any needed electrical impedance and electro-motive force, as generally known to those skilled in the art. 
     The electrically conductive elements  13  may be terminated by any of the means generally known to those skilled in the art, to provide for an appropriate electrical and mechanical connection, such as the lead wires  20  and electrical connectors  21  as shown in  FIG. 11B  and in  FIG. 12B . Alternatively, the diaphragm layer substrate material may also be itself made of a conductive material. 
     As shown in  FIG. 4A-C ,  FIGS. 16A &amp;B and  FIGS. 17A &amp;B, the magnet support structures  1  for all embodiments can be made of any suitable, relatively rigid material such as plastic, metal, ceramic, wood, carbon-based materials or any other suitable material, and can be attached to the magnets  4  and/or pole pieces  2  and  7  with adhesives, screws, magnetic attraction or through any other suitable means. 
     As shown in the exploded, conceptual view of  FIG. 8 ,  FIG. 9A  and  FIG. 20A  the small pieces of alignment material  17 , which are spaced apart from each other and placed between the diaphragm layers  10 , can be made of a wide variety of either rigid or flexible materials, such as plastic foam tape, for example, for all embodiments. 
     In addition to being constructed with diaphragm layers  10  and electric conductors  13  shaped in a circular or any other overall loop shape, and also in the alternative embodiment semi-circular shape of  FIGS. 11A &amp;B, the device can also be constructed with an overall arc-shaped section of any arbitrary angle of less than 360 degrees. 
     The resulting arc-shaped device can be mounted in an appropriate baffle  18  using the screw holes  22  shown in  FIGS. 11A &amp;B and  FIGS. 12A &amp;B. The baffle  18  may also be part of an enclosed, vented, ported or partially open cabinet or other structure such as an in-wall mounted device or an open-rear baffle device, all generally known to those skilled in the art. The front or rear of the resulting arc-shaped device may also be horn-loaded as well. 
     As shown by  FIG. 22 , a stacked, “line-source” version of the driver can be built, exhibiting extremely high efficiency, extremely wide frequency range, extremely wide horizontal dispersion, extremely uniform frequency coverage in the vertical direction, and extremely high maximum power handling. 
     The “stacked” loudspeaker embodiment as shown in  FIG. 22  may consist of a plurality of either the closed-loop configured embodiments as shown by  FIG. 1A , or may consist of a plurality of arc-segment configured embodiments as shown in  FIG. 11A , which can then be electrically connected in series, parallel, or a number of possible series/parallel combinations to achieve the desired total electrical impedance. 
     In addition to the continuously-curved diaphragm layers and electrical conductors of the present invention previously discussed herein, it is also possible to configure the device in discretely-curved types of configurations, such as those shown in  FIGS. 24A &amp;B, in which there exist one or more discrete areas of curvature of the diaphragm layers  10 . These discreetly-curved areas will cumulatively accomplish an overall curvature of the diaphragm stack  5 , with an axis of curvature  29  which is generally perpendicular to the diaphragm surface and/or electric conductors at the point, or points, of curvature. 
     The foregoing description of embodiments has been presented for purposes of illustration and description. It is not exhaustive, and it does not limit the claimed inventions to the exact forms disclosed. Additional modifications and variations are possible, in light of the above description, or may be acquired from development of the invention.