Abstract:
A mid and high frequency transducer having a compact magnet system. A first seat has an annular wall that retains a first disk shaped magnet therein and an annular channel is defined therebetween. A second seat rests on top of the first magnet and first seat and is connected thereto but does not occlude the annular opening. The second seat has an annular wall that retains a second disk shaped magnet therein such that a uniform annular gap is defined therebetween. A first voice coil is connected to a first diaphragm and is moveably suspended within annular channel and a second voice coil is connected to a second diaphragm and is moveably suspended within the annular gap. Application of an electric current to the voice coils causes movement of the diaphragms due to the magnetic flux created within the annular channel and gap and thereby produces sound waves.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to transducers and magnets contained therein, and particularly to low and high frequency transducers, such as compound loudspeakers, having a combined magnet system.  
         BACKGROUND OF THE INVENTION  
         [0002]    Conventional speakers utilize standard ferrous magnets in conjunction with a voice coil to control the speaker cone, dome, or other diaphragm. However, such magnets are relatively large and heavy and produce stray magnetic fields which require bulky shielding to contain or increased distance therebetween and unnecessarily. increase both the size and weight of the speaker.  
           [0003]    It is desirable in high fidelity speakers to place the high frequency diaphragm as close to the mid to low frequency diaphragm as possible so that the sound appears to come from a single source. To achieve this result, it is known that a sub-compact assembly is required. It has been found that such a sub-compact design can be achieved by utilizing high energy magnets, such as magnets formed of neodymium-iron-boron in place of the standard ferrous magnets.  
           [0004]    However, even with the use of the neodymium-iron-boron magnets, assemblies of the drive units are still bulky and complicated requiring numerous parts and numerous steps to assemble. For example, U.S. Pat. No. 5,548,657 to Fincham discloses a compound loud speaker drive unit that has a first transducer for producing sounds in the low frequency range and a second transducer for producing sounds in the high frequency range. However, the large magnetic structure and the complicated assembly thereof adds to the overall depth and weight of the drive units in an undesired fashion.  
           [0005]    Therefore, there remains a long standing and continuing need for an advance in the art of compound loud speakers that is simpler in both design and use, is more economical, compact, and efficient in its construction and use, and can quickly be assembled while eliminating the need for larger magnets and drive units.  
         SUMMARY OF THE INVENTION  
         [0006]    Accordingly, it is a general object of the present invention to overcome the disadvantages of the prior art.  
           [0007]    In particular, it is an object of the present invention to provide a compound loud speaker with fewer parts.  
           [0008]    It is another object of the present invention to provide a compound loud speaker wherein the transducers are reduced in size.  
           [0009]    It is another object of the present invention to provide a compound loud speaker wherein the assembly is reduced in weight.  
           [0010]    It is another object of the present invention to provide a compound loud speaker wherein the magnets and their housing is relatively compact.  
           [0011]    It is yet another object of the present invention to provide a compound loud speaker wherein the transducers are reduced in weight.  
           [0012]    It is yet another object of the present invention to provide a compound loud speaker that is easily and quickly assembled and disassembled.  
           [0013]    It is yet another object of the present invention to provide a compound loud speaker wherein the magnet structures can be magnetized in unison after assembly thereof.  
           [0014]    It is yet another object of the present invention to provide a compound loud speaker wherein the high frequency voice coil and the low frequency voice coil are in close proximity to one another.  
           [0015]    In keeping with the principles of the present invention, a unique high frequency loudspeaker is presented which overcomes the shortfall of the prior art. The loudspeaker has a circular first seat that has a peripheral annular wall that extends perpendicularly therefrom. First seat is a magnet pot and is preferably constructed of steel. A first magnet that is preferably disk shaped is received within the wall of first seat to form a uniform channel between the first magnet and the wall. First magnet is preferably the same height as the wall to form an even plane. At least an aperture extends through first seat at a position between first magnet and the wall wherein the channel is defined. First magnet is attached to the floor of the first seat by any adhesive means that is known in the art such as, but not limited to, structural adhesives.  
           [0016]    A second seat, preferably being circular in nature, is positioned upon first magnet and wall of first seat without occluding the uniform channel. Second seat has an annular protrusion that extends in an opposing direction from said first seat and encircles a second disk shaped magnet therein. An annular opening is defined between the protrusion and the second magnet.  
           [0017]    The second seat has an annular flange that extends past the annular protrusion and rests upon the annular wall of the first seat. The flange is provided with a means for binding the second seat to the annular wall of the first seat. At least a void is defined through the flange and the void is in substantial axial alignment with the aperture of the first seat to allow electrical conductors to pass therethrough.  
           [0018]    The second magnet has a disk shaped plate thereon that is preferably of the same radius as the magnet. The plate has a dome shaped diaphragm thereon that is moveably suspended thereon. The dome shaped diaphragm has a voice coil thereon that extends into the annular gap. As a current is applied to the voice coil, the voice coil is forced to move within the gap due to the magnetic flux created by the magnets. Accordingly, the dome moves back and forth and thereby generates audio output.  
           [0019]    An annular chassis is positioned over the flange of the second seat and the chassis moveably maintains a generally conical diaphragm thereon. A second voice coil is maintained on the conical diaphragm and extends into and within the opening defined between the annular wall and the first disk shaped magnet. As current is applied to the second voice coil, the voice coil is forced to move within the annular opening due to the magnetic flux created by the magnets. Accordingly, the conical diaphragm moves back and forth and thereby generates audio output.  
           [0020]    As a result, the disk shaped first and second magnets reduce the number of parts necessary to assemble the compound loud speaker. In addition, the compact nature of the magnets allows the first and second voice coils to be proximal in distance to allow coincidence of the sound source thereby increasing clarity. In addition, the present arrangements of the two magnets allows the option of magnetizing the two magnets simultaneously after they have been assembled.  
           [0021]    Such stated objects and advantages of the invention are only examples and should not be construed as limiting this invention. These and other objects, features, aspects, and advantages of the invention herein will become more apparent from the following detailed description of the embodiments of the invention when taken in conjunction with the accompanying drawings and the claims that follow. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    It is to be understood that the drawings are to be used for the purposes of illustration only and not as a definition of the limits of the invention.  
         [0023]    In the drawings, wherein similar reference characters denote similar elements throughout the several views:  
         [0024]    [0024]FIG. 1 is a top plan view of the high frequency domed diaphragm as connected to the driver portion of the invention.  
         [0025]    [0025]FIG. 2 is a cross-sectional view of a high frequency domed diaphragm and the driver portion taken along line  2 - 2  of FIG. 1.  
         [0026]    [0026]FIG. 3 is a cross sectional view of the loudspeaker also illustrating the chassis and the low frequency diaphragm.  
         [0027]    [0027]FIG. 4 is a top plan view of a compound loud speaker.  
         [0028]    [0028]FIG. 5 is a cross sectional view of an alternate preferred embodiment of the loudspeaker also illustrating the chassis and the low frequency diaphragm.  
         [0029]    [0029]FIG. 6 is a cross sectional view of the driver portion and the high frequency dome of an alternate preferred embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0030]    Referring to FIGS. 1 through 6, therein are illustrated several views of preferred embodiments of a transducer  10  in the form of a compound loudspeaker. Transducer  10  has a first seat  12  having a top surface  14  and a bottom surface  16 . A wall  18  extends perpendicularly from top surface  14  at an outer portion of first seat  12 . First seat  12  is preferably circular and wall  18  is annular. First seat  12  may be a magnet pot and is preferably constructed of steel, but is not limited thereto.  
         [0031]    A first magnet  24 , that is preferably disk shaped, is received within first seat  12  on top surface  14  thereof, such that a substantially uniform channel  26  is maintained between first magnet  24  and wall  18 . First magnet  24  may be attached to top surface  14  of seat  12  by any attaching means that is known in the art such as, but not limited to, structural adhesives. In addition, first magnet  24  is adapted to be substantially even in height with a top end  22  of wall  18 . At least an aperture  28  extends from top surface  14  and out through bottom surface  16  of first seat  12 . Aperture  28  is preferably positioned between first magnet  24  and wall  18  and is generally below channel  26 .  
         [0032]    A second seat  30  having a top side  32  and a bottom side  34  is positioned upon first magnet  24  such that bottom side  34 ; contacts magnet  24  at an end opposing said first seat  12 . Second seat  30  may be attached to magnet  24  by any attaching means that is known in the art such as, but not limited to, structural adhesives. Second seat  30  may be a magnet pot and is preferably constructed of steel, but is not limited thereto and may be made of any suitable material that is known in the art. Second seat  30  is preferably circular in nature and has a protrusion  36  extending perpendicularly from top side  32  and forming an annular wall. At an upper end  38  of protrusion  36 , an annular lip  40  extends perpendicularly inward from protrusion  36  and is substantially parallel to top side  32 .  
         [0033]    An annular flange  42  extends outwardly from second seat  30  at an even plane with bottom side  34  and rests on top end  22  of wall  18 . Flange  42  defines at least a cavity  44  therein, and preferably four equidistantly spaced cavities  44  on said flange  42 , such that the cavity  44  rests on top end  22 . Cavity  44  can accommodate a binding means such as, but not limited to, a threaded element so that second seat  30  may be removably attached to first seat  12 . At least an opening  46  is preferably annular and is also defined by flange  42 , and opening  46  is more medially positioned in relation to cavity  44 . At least a void  48  is also defined through flange  42  and void  48  is more medially positioned than opening  46 . In addition, void  48  is in substantial axial alignment with aperture  28 . In a preferred embodiment, two voids  48  are located opposing each other on a central line that equally bisects second seat  30 .  
         [0034]    A second magnet  50  having a substantially disc shape is placed on top of top side  32  of second seat  30  such that it is equidistantly spaced from protrusion  36  whereby an annular groove is created therebetween. A plate  54  is positioned upon said second magnet  50  such that plate  54  is in a congruent plane with lip  40  of protrusion  36 . Second magnet  50  may be attached to second seat  30  and plate  54  by any attaching means that is known in the art such as, but not limited to, a structural adhesive. An annular gap  56  is defined between an outer edge  34  of plate  30  and flange  26  of wall  24 . In a preferred embodiment, annular gap  56  may be injected with a metallic fluid, preferably a ferrofluid, or with some other substance that has good heat transfer characteristics but does not interfere with movements of components therein.  
         [0035]    A spacer  58 , having an annular shape, is positioned over an outer surface of protrusion  36  of second seat  30 . Spacer  58  has a vertical portion  60  that connects to an outer surface of protrusion  36 , and a horizontal portion  62  that connects to an upper region of lip  40 . Vertical portion  60  is preferably in axial alignment with void  48  and aperture  28  and is adapted to receive an electrical conducting element  64  that passes through void  48  and aperture  28 . Horizontal portion  62  is also adapted to accommodate element  64  therethrough. Element  64  is an electrical conductor that is electrically insulated from first seat  12 , second seat  30 , and channel  26  as it passes therethrough.  
         [0036]    A high frequency domed diaphragm  66  has an annular support  68  at an outer periphery thereof that is of annular corrugated form and support  68  is connected to spacer  58  in a movable fashion. Secured to diaphragm  66  is a cylindrical coil former carrying a high frequency voice coil  70  such that the voice coil extends through the gap  56 . Diaphragm  66  may be constructed of a variety of rigid materials, and in a preferred embodiment, diaphragm  66  is constructed from metals such as, but not limited to, titanium or aluminum. Diaphragm  66  may also be constructed from a plurality of alloys containing metals such as, but not limited to, aluminum and boron. In addition, diaphragm  66  may also be made of a soft material such as, but not limited to, sealed cloth, flexible materials such as plastics, or other suitable material that is known in the art. In operation, as current is applied to conducting element  64  and in turn to voice coil  70 , voice coil  70  is forced to move in gap  56  due to the magnetic flux created by first magnet  24  and second magnet  50 , lip  40 , second seat  30 , and plate  54 . In turn the domed diaphragm  66  is caused to move back and forth axially. As the dome moves forward, it compresses the air in front of it and as the dome moves backward it rarefies the air in front of it, and thus the desired audio output is produced by the numerous compressions and rarefactions.  
         [0037]    Now referring specifically to FIGS. 3, 4,  5 , and  6  a chassis  72  has a front annular projection  74  and a rear annular member  76  that are interconnected by a plurality of ribs  78 . Rear annular member  76  has a medially projecting annular brim  80 . Annular brim  80  is connected to flange  42  of second seat  30  in a secure yet removable fashion and is fitted thereon in such a fashion as not to occlude opening  46 .  
         [0038]    A second diaphragm  82  comprises the mid to low frequency diaphragm and is of generally frusto-conical form. At an outer edge  84 , the second diaphragm  82  is connected to projection  74  via a flexible surround  86 . At an inner edge  88 , the second diaphragm  82  is connected to a tubular coil former  90  and coil former  90  is adapted to extend into the opening  46  defined by flange  42 . Coil former  90  carries the mid to low frequency voice coil thereon such that the coil extends through opening  46 .  
         [0039]    A suspension member  92 , that is annular and flexible in nature is secured between annular member  76  of chassis  72 , and the coil former  90  in order to ensure that coil former  90  and the voice coil carried thereon are maintained concentric with and within opening  46  and out of physical contact with the surrounding elements during sound producing movements of second diaphragm  82 . The length of the coil former  90  may be extended or shortened as desired to control the distance of second diaphragm  82  from domed diaphragm  66 . Connections to the mid to low frequency voice coil are provided by means of flexible leadout conductors  94  extending from the voice coil to external connectors  96 .  
         [0040]    It will be appreciated that with the high frequency drive unit positioned at or adjacent to the neck of the second diaphragm  82  of the mid to low frequency drive unit, as above described, the apparent sound source or acoustic center of the high frequency drive unit is substantially co-incident with the apparent sound source or acoustic center of the mid to low frequency drive unit.  
         [0041]    The radiation pattern or directivity of the low frequency drive unit is determined inter alia by the form of the low frequency second diaphragm  82  and an annular wave guide  98  surrounding said domed diaphragm  66 . With the high frequency drive unit positioned adjacent to the neck of the mid to low frequency second diaphragm  82 , the form of the mid to low frequency cover imposes its directivity upon the radiation pattern or directivity of the high frequency unit. Consequently, at frequencies at which both drive units contribute significant sound output both drive units have substantially similar patterns of radiation or directivity. As a result, the relative sound contributions from the two drive units as perceived by a listener are substantially unaffected by the listener being positioned at off axis positions.  
         [0042]    The mid to low frequency diaphragm is shown to be a cover of conical form having an angle of flare which increases from inner edge  88  to outer edge  84 . However, it will be appreciated that the cover may be of conical form having a uniform angle of flare. Also, the mid to low frequency cover may be of circular, elliptical, square, rectangular, or other section as desired.  
         [0043]    The high frequency diaphragm  66  is shown in the drawing as being of domed form. Such a diaphragm is suitable because its acoustic center may be readily located in close coincidence with that of the mid to low frequency diaphragm, and because, in the frequency range where both units contribute significant sound output, its small size relative to wavelength gives it, by itself, essentially non-directional sound radiation, allowing the effective directivity to be determined by the mid to low frequency diaphragm. It will be appreciated that the high frequency diaphragm  66  may alternatively be of any other form that provides these characteristics.  
         [0044]    It will also be appreciated that the arrangement of the first magnet  24  and second magnet  50  of the present invention reduces the number of parts necessary to assemble the two drive units. In addition, the present arrangement of the two magnets allows the magnetization thereof as an assembly, whereas, in the prior art, each magnet had to be magnetized individually and then assembled. Furthermore, the present magnets may either have similar polarity, thereby allowing magnetization as an assembly, or may have opposite polarities, wherein the magnets are individually magnetized and then assembled.  
         [0045]    While the above description contains many specificities, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. Many other variations are possible without departing from the essential spirit of this invention. Accordingly, the scope of the invention should be determined not by the embodiment illustrated, but by the appended claims and their legal equivalents.