Abstract:
The present invention includes a variety of magnetic circuit arrangements functioning as acoustic drivers. The circuits include a coil former around which is wrapped a conductive coil and a magnetic gap in which the former is at least partially positioned. Further, an output disk is associated with the former to transfer sound to a substrate. Specifically, each embodiment includes a multi-component suspension system comprising various ways to associate at least one spider suspension with the coil former and integrated mounting apparatus variations that include infrastructure brackets allowing for position adjustments and compensation for torque forces on the bracket.

Description:
[0001]     This application is a continuation in part of U.S. application Ser. No. 10/995,145 filed Nov. 24, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to inertial type voice coil actuators capable of converting energy between electrical and mechanical form and, more particularly, to an inertial type voice coil actuator that utilizes a multicomponent suspension for alignment of the moving coil and having an integrated mounting system.  
         [0004]     2. Description of the Prior Art  
         [0005]     Inertial voice coil actuators have been used in the past to acoustically stimulate semi-rigid structures to radiate sound. In this application, voice coil actuators have been attached to structures that are relatively large to act as a soundboard such as a wall in a room, where the wall of the room, when acoustically driven radiates sound. As is well known in the art, the force generated by an electrodynamic transducer is a product of the current, I, length of coil wire, L and flux density, B so that F=iL{circle around (×)}B. The length of the coil wire that is within the annular magnetic gap is defined as the length, L. This force is what creates the movement of the coil and subsequently generates sound.  
         [0006]     These inertial type voice coil transducers are built upon magnetic circuit designs that have classically been used for conventional cone type loudspeakers and not optimized for driving soundboard type structures. These voice coil actuators often require the use of an external housing to support the heavy magnet assembly relative to the voice coil. The voice coil is in communication with the external housing at a location coincident with an acoustic output system that permits the transducer housing to be mechanically attached to a soundboard.  
         [0007]     Loudspeaker motors such as used in the past comprise a magnet circuit assembly including a permanent annular magnet, polarized in the axial direction, and sandwiched between two magnetizable plates. One of the plates carries a cylindrical post that extends through a central space defined by the annular magnet, generally referred to as a cylindrical pole piece. The other plate has an annular opening, somewhat larger than the diameter of the pole piece, such that an annular magnetic gap is formed between the post and the inner edge of the associated annular plate. The height of the gap is formed by the thickness of the annular plate having the annular opening.  
         [0008]     The basic architecture of the loudspeaker motor design is based upon low magnetic energy magnets, typically comprised of ceramic materials. In order for sufficient magnetic flux to be generated within the annular magnetic gap, the annular magnet must be very large relative to the other components. Some manufacturers have utilized higher energy rare earth based magnets such as Neodymium, but this magnetic architecture is not optimized for the characteristics of these magnets. Integrated mounting systems and multi-component suspension systems have, heretofore been relatively unsuccessful.  
         [0009]     Voice coil actuators have a moveable voice coil disposed within the annular magnetic gap. For speakers that use a large body such as a wall to generate sound, the coil has a suspension system that typically utilizes an external housing to which the annular magnet and magnetizable plates are also attached. The external housing provides radial stiffness and axial compliance to the coil. The moving coil has a first end fixedly secured to a radially central portion of the inner surface of the external housing wall. A mounting screw secured to an exterior well portion of the exterior housing may be attached to the wall.  
         [0010]     Other magnetic circuit configurations referred to as “pot configurations” have been similarly employed. Generally speaking, these arrangements include top and bottom plates and typically employ the magnet or magnets positioned between the plates leaving an annular channel around at least one of the magnets.  
         [0011]     A number of inventions for voice coil actuators have been patented which disclose the aforementioned factors, among them U.S. Pat. No. 2,341,275 to Holland for Sound Reproducing Instrument; U.S. Pat. No. 3,609,253 for Loudspeaker with Improved Voice Coil Suspension; U.S. Pat. No. 3,728,497 to Komatsu for Dynamic Loudspeaker Using Wall as Diaphragm; U.S. Pat. No. 4,297,537 to Babb for Dynamic Loudspeaker; U.S. Pat. No. 4,951,270 for Audio Transducer Apparatus; U.S. Pat. No. 5,335,284 to Lemons for Coneless, No-Moving-Parts Speaker; and U.S. Pat. No. 5,473,700 Fenner, Jr. for High Gain Transducer.  
         [0012]     In practice, the annular magnet, magnetizable plates, external housing and structural attachment point comprise a system that is large and heavy relative to the total dynamic force the actuator is capable of generating. If the external housing is mounted on a vertical facing surface e.g. a wall, large bending moments are placed on the structural attachment point and the housing must accommodate these moments without translating them to the coil.  
         [0013]     The pot configurations also face many of the same challenges.  
         [0014]     These types of electrodynamic transducers are plagued with well known problems of low power handling, limited frequency response, high levels of sound distortion, substantial size and mass, mechanical complexity and high production costs.  
         [0015]     Recent innovations include magnetic materials that have produced magnets with substantially greater magnetic energy than ceramic magnets. These magnets have necessitated the redesign of the magnetic circuit to take advantage of the higher magnetizing flux while reducing the volume of the magnet material consumed, thus reducing its size while simultaneously increasing its force density per unit volume. However, these prior art voice coil actuators are not typically designed with suspension systems adequate for actuators driving relatively large structures such as walls.  
         [0016]     U.S. Pat. No. 4,297,537 to Babb for Dynamic Loudspeaker describes an antifriction bearing which adjoins the voice coil and slidably moves on the cylindrical pole piece providing high radial stiffness and essentially infinite compliance in the axial motion of the voice coil. This patent describes a magnetic circuit with an annular magnet where the voice coil is driving a conventional cone speaker. It does not utilize a large body for sound generation nor is it designed to be vertically mounted.  
         [0017]     U.S. Pat. No. 5,335,287 to Lewis for Loudspeaker Utilizing Magnetic Liquid Suspension of the Voice Coil discloses a method of using a viscous magnetic fluid suspension for the voice coil in lieu of a corrugated disk suspension. However, use of such fluid can result in internal pressure build-ups or subatmospheric conditions within the magnetic gaps. U.S. Pat. No. 5,335,287 solves that problem by including a fairly sophisticated venting system, however, the system is expensive to manufacture and the speaker disclosed is of the traditional cone type without adaptation to large sound bodies. No means is provided to minimize flux leakage.  
         [0018]     Increasingly, high fidelity audio recordings are being made where the upper frequency range is over one (1) octave higher than normal human hearing at 20 kHz. Accurate reproduction of these frequencies is often not addressed or is only poorly accomplished by earlier speaker systems.  
         [0019]     It is therefore an object of the present invention to provide a novel voice coil actuator with a high force density. It is a second object of the present invention to minimize flux leakage while providing a smaller and more efficient device for driving relatively large structures. A third objective of the invention is to minimize sound distortion by providing a multi component voice coil suspension system. A fourth objective of the invention is to provide an inertial voice coil actuator equipped with a simple mounting system for transducing sound to a soundboard.  
         [0020]     A fifth objective is to provide an inertial voice coil actuator equipped with means to quickly and removably affix the voice coil actuator to various surfaces without the use of adhesive bonding between the output disk and the soundboard and without the need for tools thereby minimizing assembly and repair time.  
         [0021]     A sixth objective is to provide an inertial voice coil actuator that may be installed intra-wall without loss in sound quality.  
         [0022]     It is another object of the present invention to further provide a means to couple the voice coil actuator with a soundboard utilizing controlled pressure where the voice coil actuator is not exposed, but is installed within a wall.  
         [0023]     It is further a feature of the present invention to provide means to supply a signal and current to the voice coil actuator through a retainer where contacts are configured to maintain their electrical connection even with slight axial translation of the voice coil actuator.  
         [0024]     It is a final feature of the present invention to govern the placement of the voice coil actuator between the vertical studs of a wall in order to diminish resonate frequencies of the soundboard and to allow physical adjustment and registration with ease.  
       SUMMARY OF THE INVENTION  
       [0025]     According to one embodiment of the present invention, the novel voice coil actuator includes a magnetic flux conductive material core, a magnet, and an electrical current conductive coil uniquely arranged. The core has a first surface and a continuous channel disposed in said first surface. The channel has a pair of opposing walls. The magnet is radially polarized and disposed in intimate contact with either one of the channel walls and spaced from the opposing channel wall so that a gap remains between the magnet and the opposing wall. The magnet has two faces of opposite magnetic polarities; one faces the gap. The magnet is further spaced from the bottom of the channel so that magnetic flux is substantially normal from the face across said gap to the wall. The electrical current conductive coil is disposed around a coil former and moveably positioned in the gap such that an electrical current in the coil develops a magnetic force on the coil in a direction substantially normal to the magnetic flux to displace the coil in response to the magnetic force.  
         [0026]     A second embodiment comprises a permanent annular magnet polarized in the axial direction and sandwiched between two plates. The bottom plate comprises a cylindrical central post that extends through the annular magnet. The top plate includes an annular opening somewhat larger than the diameter of the post, such that an annular magnetic gap is formed between the post and the inner edge of the associated annular plate.  
         [0027]     Additional magnetic circuits referred to as pot configurations can be employed. For example, a first pot configuration comprises a cylindrical magnet that is magnetically polarized along the axis and axially aligned with a top plate. A bottom plate is cup shaped into which the magnet is placed wherein the gap between the bottom plate and the top plate is the magnetic gap. A second configuration includes a cylindrical magnet in the form of an annular disk. The top is also annular disk shaped with a constant radius distal surface and aligned with the magnet. The bottom plate has one surface normal to the axis upon which magnet is positioned and a second surface at a constant yet larger radius than that of the distal surface of the top plate. An annular groove is formed between the distal surface of the top plate and the second surface of the bottom plate. A final pot configuration employs two magnets, one annular in shape and a second cylindrical. They are arranged in opposite polarity. Two top plates, one annular and one cylindrical each in contact with the magnet of the same shape and a cylindrical bottom plate having radius large enough to support the cylindrical magnet positioned inside said annular magnet and wherein the inner wall of the annular top pole piece and outer wall of the cylindrical top plate form the magnetic gap.  
         [0028]     The magnet circuits disclosed include a “tulip” arrangement wherein a radially polarized annular magnet surrounds a lower portion or a cylindrical center post. The center post includes an upper portion of smaller radius. An annular return pole wherein the opening has an inside radius and surrounds the magnet and a portion of the pole extends upwardly therefrom having an opening with a smaller inside radius. Said post extends upwardly beyond the magnet such that an outside surface of the post and an inner surface of the annular pole are proximal and form the annual gap.  
         [0029]     A feature according to the present invention is a multi-component suspension system that supports the electrical current conductive coil in such a manner that the coil has high radial stiffness along with appropriate axial compliance. The electrical current conductive coil is wound on the coil former that is typically formed of polymeric material to form a cylindrical shaped object. The coil former has a first portion that is external to the magnetic gap and suspended by a disk shaped member known as a spider suspension that provides radial stiffness while providing a restoring force to an axial displacement. The spider suspension of the first embodiment includes a concentric corrugation that provides additional compliance in the axial direction. The compliance of this spider suspension is tuned to first resonant frequency that is below the low pass (f 0 ) frequency of the signal sent to the inertial type voice coil actuator. In addition the suspension provides sufficient stiffness to support the mass of the magnetic circuit in a vertical orientation without displacing the voice coil from neutral position more that 10% of its total axial displacement. A second embodiment includes a second spider suspension spaced vertically from the first, having the same general configuration as the first suspension.  
         [0030]     The spider suspension has an annular opening that is sized to the outer diameter of the voice coil former. The spider has an outer diameter that is mechanically attached to a surface of the core. The spider suspension system in a preferred embodiment is formed of an elastic or visco-elastic material such as polyurethane, polypropylene, or other polymeric material. More than one spider may be used for added suspension control.  
         [0031]     Alternatively, the spider suspension is in a disk configuration such that the outer diameter of the spider is sized to the inner diameter of the voice coil former. The spider has a central attachment mechanically associated with the surface of either a top plate or bottom plate, depending on the magnetic circuit arrangement. Again, a second spider suspension may be used in conjunction with the first.  
         [0032]     A second portion of the coil former is internal to the gap and a viscous magnetic fluid suspension and an antifriction bearing suspend the second portion. The viscous magnetic fluid suspension is a fluid that fills any space between the inner and outer surfaces of the voice coil former, the coil, the face of the magnet, and the wall of the channel. The viscous magnetic fluid prevents the voice coil from rubbing or striking the wall of the channel or the face of the magnet. The suspension system may also comprise an antifriction bearing surface disposed in intimate contact with one wall of the channel to support the surface of voice coil former. The antifriction bearing is sized to provide sufficient clearance for the voice coil former, but in the event of a large radial force, it prevents the voice coil from striking or rubbing the wall of the channel or the face of the magnet. This bearing also provides a spring of infinite compliance along the axial length of the electrical current conductive coil.  
         [0033]     In the preferred embodiment, the magnetic fluid is a low viscosity oil, having microscopic ferrous particles such as magnetite, homogeneously suspended in the fluid. The oil-magnetic emulsion is attracted to and held in the magnetic field within the magnetic gap by reason of the magnetic flux across this gap. The magnetic particles hold the liquid phase of the oil within the gap. The viscous magnetic fluid provides a heat dissipating mechanism and a radial restoring force when the voice coil is radially displaced. The restoring force is a result of an unbalanced magnetic force in the fluid when the fluid is not symmetrically displaced within the magnetic gap and coil former. The radial restoring force is typically sufficient to support the mass of the magnetic circuit when its axis is parallel to a horizontal orientation. In the event of substantially larger radial forces that will overcome the radial restoring force of the viscous magnetic fluid, the antifriction bearing acts as a back-up bearing for the voice coil former.  
         [0034]     A third feature of the present invention includes a unique integrated mounting apparatus providing both quick installation and quick removal features. The mounting apparatus transduces vibrations through the coil to the soundboard through an output disk. In a preferred embodiment the integrating mounting apparatus comprises the output disk acoustically associated with the soundboard and the coil former.  
         [0035]     Another preferred embodiment includes an integrating mounting apparatus comprising the output disk and a receiver designed to interlock one with the other in such a way as to accurately translate the vibrations without attenuation or distortion to a sound body. One way of accomplishing these objectives uses an interlocking mechanism which comprises at least one helically arranged wedge on the output disk and at least one complementary engagement opening on the receiver. In operation, the wedges on the output disk are positioned to be in communication with a base formed in the receiver thereby providing accurate transmission of vibrations. In the preferred embodiment the output disk further registers into the receiver rotationally via pins, tabs or other registration means which assist in placement of the engagement wedge on the wall of the receiver. The output disk can then be rotated and pressured into the receiver. There is a locking means that will hold the output disk in its downward pressured position against the receiver in order to accurately transmit vibrations and forces created by the voice coil actuator to the receiver, and then through the receiver to the substrate or soundboard.  
         [0036]     To evenly distribute the downward pressure forces between the output disk and the receiver exerted by the helical interface, the distal surface of the output disk can be molded with a very slight convexity. When pressured into the receiver by the helical means on the output disk, the output disk would compress downward, flattening the convexity of the outer surface rendering it flat and causing even forces to propagate throughout the surface.  
         [0037]     Adhesive or conventional fixative means are used to acoustically couple the receiver and the soundboard. No adhesives between the output disk and receiver are necessary. This mounting arrangement is particularly useful when the voice coil actuator is to remain exposed and minimizes the need for tools and time for assembly, installation, and repair.  
         [0038]     The unique integrated mounting apparatus in yet another embodiment preferably provides a means to affix the voice coil actuator in a way that will result in an intra-wall sound transducer rather than an exposed sound transducer. Here, means to affix said voice coil actuator must create a controlled contact force between the output disk and the soundboard. This is accomplished by using a retainer that can itself be affixed mechanically, adhered or otherwise in communication with the infrastructure of the wall and providing means to pressure said voice coil actuator into a receiving cavity in the retainer. The retainer is registered and affixed via registering means to one of the vertical stud members of a standard wall construction. The receiving cavity is provided means by which to guide the insertion of the voice actuator. A contact protrusion on the voice coil actuator includes electrical contacts and a contact opening in the retainer includes at least one sprung electrical contact with which the voice coil electrical contact is slidably engaged. The contacts are configured to maintain their electrical connection even with slight axial translation of the voice coil actuator.  
         [0039]     Preferably, a perimeter ring forms part of the receiver. The output disk is seated by the perimeter ring which pushes the output disk out beyond a register with the retainer. When wall cladding, such as drywall, is added, means to associate the output disk with the drywall ensure that the drywall presses the output disk and, in turn, the perimeter ring, producing the desired controlled contact force. The receiving cavity of the retainer holds the voice coil actuator in a precise axial orientation normal to the drywall surface. A small space allowance within the axial orientation of the voice coil actuator between the voice coil actuator and retention means permits small axial movements of the voice coil actuator to be unimpeded. A loose, frictionally triggered snap is the preferred means of retention.  
         [0040]     For intrawall installations, the placement of the voice coil actuator between the studs of a wall can improve sound quality. In order to diminish resonate frequencies, the distance from the center axis of the receiving cavity of the retainer and the stud registering surfaces of the retainer are such that the voice coil actuator is placed inboard of the intra-stud center point to diminish resonate frequencies of the substrate.  
         [0041]     An alternative means for intrawall installation uses a bracket mounted between two studs. The bracket includes a hole through which a threaded nut penetrates and is secured yet rotationally free to move. The transducer is equipped with a threaded element. The transducer&#39;s position relative to the bracket can be adjusted along the length of the element by turning the threaded nut.  
         [0042]     In order to accurately reproduce the extended frequency response of the system, a high frequency speaker element may be mounted in near proximity to the inertial voice coil actuator assembly. These high frequency speaker elements can be comprised of any electro-dynamic, piezo-electric, or magnetostrictive type systems.  
         [0043]     In one configuration providing extended frequency response, the integrated mounting apparatus includes the output disk which comprises an annular opening. A high frequency speaker element is co-axially located with the output disk of the voice coil actuator opposite the voice coil actuator assembly and mounted in such a manner that the acoustic output of the high frequency speaker element is directed away from the side on which the inertial type voice coil actuator is mounted. The output disk may be mechanically or adhesively affixed to the soundboard.  
         [0044]     The high frequency speaker element is electrically connected with the inertial type voice coil actuator so that the high frequency components of the audio signal are preferentially sent to the high frequency speaker while limiting the low frequency components to the inertial type voice coil actuator.  
         [0045]     Another embodiment of the inertial type voice coil actuator with extended high frequency speaker system uses a plurality of high frequency speaker elements configured in a spatial array. The spatial array can be configured in any single, two or three-dimensional geometry.  
         [0046]     The present invention provides a voice coil actuator with superior suspension system and novel construction, which results in a lighter and smaller package, more accurate sound reproduction, and faster, simpler installation for use with large or small soundboards.  
         [0047]     Other objects, features, and advantages of the present invention will be readily appreciated as the same becomes better understood after reading the subsequent description taken in conjunction with the appendant drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0048]      FIG. 1  is a perspective view of the present invention as installed on a large sound body;  
         [0049]      FIG. 2 . is a fragmentary cross-sectional perspective view along line  2 - 2  on  FIG. 1  of one embodiment of the Inertial Type Voice Coil Actuator of the present invention showing its suspension system and construction;  
         [0050]      FIG. 3  is a cross sectional view along line  3 - 3  of  FIG. 1  of the Inertial Type Voice Coil Actuator of the present invention including an acoustic mechanical interface between the output disk and receiver of the present invention;  
         [0051]      FIG. 4  is an exploded perspective view of a second embodiment showing the output disk and a receiver with interlocking elements of the present invention;  
         [0052]      FIG. 5  is a top view of the locking portions of the receiver and output disk elements of the second embodiment;  
         [0053]      FIG. 6  is a cut away perspective view of the receiver and output disk interlocked, particularly showing the interlocking elements of the second embodiment;  
         [0054]      FIG. 6   a  is a cross section of the output disk along line  6 - 6  showing a convex surface;  
         [0055]      FIG. 7  is a cross sectional view of a third embodiment of the present invention wherein an additional element in the suspension system is shown;  
         [0056]      FIG. 8  is a perspective view of the third embodiment installed on a wall stud member;  
         [0057]      FIG. 9  is an exploded perspective view of the third embodiment showing the retainer element, particularly showing certain features of the receiving cavity of the retainer;  
         [0058]      FIG. 10  is an exploded perspective view of the third embodiment, particularly showing certain other features of the receiving cavity of the retainer;  
         [0059]      FIG. 11  is a cut away view of the retainer element at the height of a retention means on the retainer element of the preferred embodiment;  
         [0060]      FIG. 12  is a cut away view of the retainer element at the height of an electrical contact means on the retainer element of the preferred embodiment;  
         [0061]      FIG. 13  is a perspective view of the rear of the retainer element of the third embodiment;  
         [0062]      FIG. 14  is a cross sectional view of an inertial type voice coil actuator of a fourth embodiment showing a high frequency speaker element co-axially mounted within the output disk;  
         [0063]      FIG. 15  is a cross sectional view of the fourth embodiment of the present invention showing a multi element, hemispherical, high frequency array;  
         [0064]      FIG. 16  is a cross-sectional view of an alternative magnetic circuit having an annular magnet;  
         [0065]      FIG. 17  is a cross-sectional view of a second alternative magnetic circuit having a pot configuration;  
         [0066]      FIG. 18  is a cross-sectional view of a third alternative magnetic circuit having a pot configuration;  
         [0067]      FIG. 19  is a cross-sectional view of a fourth alternative magnetic circuit having a pot configuration;  
         [0068]      FIG. 20  is a cross-sectional view of a fifth alternative magnetic circuit exhibiting a tulip configuration;  
         [0069]      FIG. 21  is a cross-sectional view of an alternative spider suspension in the present invention;  
         [0070]      FIG. 22  is a cross-sectional view of an alternative intrawall integrated mounting system;  
         [0071]      FIG. 23  is a perspective view of a second alternative intrawall integrated mounting system;  
         [0072]      FIG. 24  is a top plan view of the second alternative intrawall integrated mounting system; and  
         [0073]      FIG. 25  is a perspective view of the second alternative showing the hinge of the intrawall integrated mounting system. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0074]     Referring now to  FIGS. 1-2 , there is shown a novel inertial type voice coil actuator constructed according to the principles of the present invention. A voice coil actuator assembly  90  includes a core  101 , a magnet  105 , an electrical current conductive coil  106 , and a multi-component suspension system  92  comprising a coil former  107 , an antifriction bearing  104 , a spider suspension  111 , and a spacer  110 . The core  101  is constructed from magnetic flux conductive material and has a first surface  102  and a continuous channel  103  disposed in the first surface  102  which leaves a center column  120  with a top surface  122 . The channel has a first wall  108 , a second opposing wall  109 , a bottom wall  116  and an anti-fringing groove  121 . An integrated mounting apparatus  94  of a preferred embodiment of the voice coil actuator comprises an output disk  112  (see  FIGS. 1,2  and  3 ). The integrated mounting apparatus of another embodiment includes an output disk  247  and a receiver  114  with means for interlocking said output disk and said receiver (see  FIGS. 4-6   a ). Another embodiment uses an integrated mounting apparatus comprising the output disk  112  and a retainer  200  (see  FIGS. 7-13 ). A final embodiment includes an output disk  112  having an annular hole  310  as the integrated mounting apparatus (see  FIGS. 14 and 15 ).  
         [0075]     The magnet  105  is disposed in intimate contact with the second wall  109  so that a magnetic gap  124  is formed between the magnet and the first wall  108 . (See  FIG. 2 ) The magnet  105  is cylindrical in shape, is of radial polarization, and comprises a first face  126  of a first magnetic polarity and a second face  128  of a second polarity. The first face  126  is adjacent the second wall  109  and the second face  128  is disposed within the gap  124 . The magnet  105  has a lower edge  115  spaced from the bottom wall  116  of the channel  103  forming an anti-fringing groove  125  and an upper edge  117  coextensive with the top surface  122  of the center column  120 . It should be understood that magnet  105  may be disposed on either first wall  108  or second wall  109 . A higher performance design of the present invention will have the magnet  105  disposed on the outer first wall  108  of the channel  103 . This alternative arrangement creates a stronger magnetic flux across the gap, thus improving its force output for a given current.  
         [0076]     Shown best in  FIG. 2 , the coil  106  is moveably suspended in said gap  124  such that an electrical current in the coil  106  develops a magnetic force on the coil  106  in a direction substantially normal to the radial magnetic flux caused by magnet  105  to displace the coil  106  in response to such magnetic force. Of course, when the coil  106  is coaxially suspended in the gap, the force will be axial and linearly proportional to the current, as is well known.  
         [0077]      FIGS. 16-20  show alternative magnetic circuit arrangements. Specifically,  FIG. 16  showa a circuit with a magnetizable bottom plate  401  comprising a center post  405  having an outside surface  407  and a permanent angular magnet  410  comprising a top surface  412 , an inner surface  414 , an outer surface  416 , and a bottom surface  418  and a center opening  419  and further comprising a top plate  420  having an opening  422 . An annular magnetic gap  124  is formed between said top plate  420  and said center post  405 . An annular channel  103  comprising said magnetice gap  124  and the space bounded by said inner surface  414 , the outside surface  407  and the bottom plate  401 .  
         [0078]      FIG. 17  shows the first of three magnetic circuits generally known as pot configurations. The first pot configuration comprises a cup shaped bottom plate  530  including an inner bottom surface  532  and an inner side surface  534 , a cylindrical magnet  520  comprising a top surface  522 , a lower surface  524  and an outer surface  526 . A magnetizable top plate  501  comprises an outer surface  502  wherein a magnetic gap  124  is formed between said inner side surface  534  of said bottom plate  530  and said outer surface  502 . An annular channel  103  comprising said magnetic gap  124  and the space bounded by said magnet  520  and said inner bottom surface  532  and said inner side surface  534  of said bottom plate  530 .  
         [0079]      FIG. 18  shows the second of three pot configurations and comprises an axially polarized cylindrical magnet  720  having a top surface  722 , a bottom surface  724 , and an outer surface  726  and an axially polarized annular magnet  750  having an inner surface  752 , an upper surface  754 , a lower surface  756 , and an outside surface  758 . Cylindrical magnet  720  and annular magnet  750  are aligned with opposite polarity. Said inner surface  752  of the annular magnet  750  comprises a radius greater than and spaced apart from the outer surface  726  of the cylindrical magnet  720 . The circuit further comprises a top plate  710  having a distal surface  712 , an annular top plate  740  having a proximal surface  742 , a bottom plate  730  having a planar surface  732 , a magnetic gap  124  comprising a space bounded by said distal surface  712  and said proximal surface  742 , and an annular channel  103  comprising said magnetic gap and bounded by the outer surface  726  of the cylindrical magnet  720 , the inner surface  752  of the annular magnet  750 , the distal surface  712  of said top plate  710  and the planar surface  732  of the bottom plate  730 .  
         [0080]      FIG. 19  shows the third of the three pot configurations and comprises an axially polarized magnet  620  in the form of an annular disk having an upper surface  622 , a lower surface  624 , an inner surface  626 , and an outer surface  628  and a top annular disk-shaped plate  610  comprising a first surface  618  and a second surface  612  normal to the axis of the magnet. The circuit further comprises a bottom plate  630  with a top surface  631  adjacent the lower surface  624  of the magnet and a proximal surface  638  at a radius from center greater than the position of said second surface  612  of the annular plate such that a mageneitc annular gap  124  is formed therebetween. An annular channel  103  completes the circuit and is formed between said proximal surface  638  of the bottom plate and the outer surface of the magnet  628  and the second surface  612  of the top plate.  
         [0081]      FIG. 20  illustrates the tulip configuration of the magnetic circuit. Here, the circuit comprises a radially polarized annular magnet  1000  having a top surface  1002 , a bottom surface  1004 , an inner surface  1008  and an outer surface  1006 ; a cylindrical center post  1010  coaxially aligned with the radially polarized magnet  1000  and having a top surface  1015 , a bottom surface  1016 , a first distal surface of constant radius  1018  and a second distal surface having a constant radius  1020 ; and an annular return pole  1030  coaxially aligned having a top surface  1032 , bottom surface  1034 , an outer surface  1036 , a first proximal surface  1038  of constant radius and a second proximal surface  1040  of a constant radius. The inner surface  1008  of the radially polarized magnet is associated with the second distal surface  1020  of the cylindrical center pole and the outer surface  1006  of the radially polarized magnet is associated with the second proximal surface  1040  of the annular return pole. A magnetic gap  124  comprising a space bounded by said first distal surface  1018  of the center pole piece and the first proximal surface  1038  of the annular return pole and an annular channel  103  comprising said said magnetic gap  103  and bounded by the second surface  1020  of the center post, the second surface  1040  of the annular return pole, and the upper surface  1002  of the annular magnet completes the circuit.  
         [0082]     The coil  106  is wound on the coil former  107  that is used to mechanically couple the electromagnetic force between the magnetic flux from the permanent magnet to the output disk  112 . The suspension of the coil former  107  in the present invention is designed to maintain radial alignment of the coil  106  within the gap  124  without causing sound distortion. This suspension system  92  prevents the coil  106  from striking or rubbing against the wall  108  of the channel  103  or the second face  128  of the magnet while still allowing axial compliance.  
         [0083]     Referring now to  FIGS. 1-3 , the suspension system  92  comprises the coil former  107 , a first portion  130  of the coil former  107 , a spider  111  with a concentric corrugation  119 , the spacer  110 , a groove  132  in the output disk  112 , a viscous magnetic fluid  134 , and the antifriction bearing  104 . The first portion  130  of the coil former is radially suspended by the spider  111  which is disk shaped in the preferred embodiment. The spider  111  may contain a concentric corrugation  119  that provides additional compliance by the coil former  107  in the axial direction. The concentric corrugation  119  will also permit additional axial displacement. This additional displacement is required for improving the low frequency response, or alternatively increased sound pressure level. The spacer ring  110  comprises means for attaching a distal portion  138  of the spider suspension  111 . Means for attaching the distal portion  138  of the spider  111  to the spacer  110  can be through overmolding, ultrasonic welding or other bonding or mechanical methods.  
         [0084]      FIG. 21  shows an alternative spider suspension. Here, said spider suspension comprises a spider  810  having a distal portion  812 . Means for mechanically associating said spider  800  and said top plate or center pole  405  or  501  or  610  or  710  and further comprising an association between said distal portion  812  of said spider  810  and an inner surface  815  of said coil former  107 . Alternatively, an association between said distal portion  812  of the spider  810  and an outer surface  816  of said coil former  107  is provided.  
         [0085]     The antifriction bearing  104  has a first face  140  in intimate contact with the second wall  109  of the gap  124 . An upper surface  142  of the bearing  104  is in intimate contact with the lower edge  115  of the permanent magnet  105  and a lower surface  144  is in contact with the bottom wall  116  of the channel  103 . A second face  146  of the bearing  104  is facing a first inner surface  148  of the coil former  107 . The bearing  104  of the preferred embodiment is made from a low friction material such as Teflon® by DuPont or similar material.  
         [0086]     The acoustic output of the present invention is to the output disk  112  and best shown in  FIGS. 2 and 3 . The output disk  112  comprises a groove  132  in which the coil former  107  is bonded. The output disk  112  serves to stabilize the thin wall coil former from transverse radial forces between the coil former  107  and the output disk  112 . The output disk  112  is a lightweight component to preferentially increase the velocity of the output disk  112  relative to the core  101  based on the relative mass. The output disk  112  may be attached mechanically or adhesively to a soundboard.  
         [0087]     As best seen in  FIG. 3 a  second portion  149  of the coil former  107  is radially suspended by the viscous magnetic fluid  134 . The magnetic fluid  134  is held in suspension by the resulting magnetic flux from the permanent magnet  105 . The magnetic fluid will provide a radial restoring force if the coil former  107  is radially displaced in the magnetic gap  124 . The antifriction bearing  104  is provided for the coil  106  to land upon if a large radial force is imparted to the coil former  107  causing large radial displacements. The bearing  104  will prevent the coil former  107  from striking or rubbing the magnet  105  or the outer wall  108  of the channel  103 .  
         [0088]      FIGS. 4, 5  and  6  depict an integrated mounting apparatus of another embodiment. The output disk  247  and its receiver  114  and means for interlocking them are shown. In the preferred embodiment, there is a distal surface  150  of the output disk  247  on which are at least one and preferably a plurality of segmented helical wedges  152  and  152   a . Each of said plurality of segmented helical wedges  152  tapers from a first leading edge  154  to a second trailing edge  156 . In the preferred embodiment, each segmented wedge  152  is generally spaced equidistant from other segmented wedges.  
         [0089]     The receiver  114  of this preferred embodiment has an annular hole  160  with a depth  162  and a base  164 . A protruding segmented wall  250  is characterized by at least one and preferably a plurality of openings  251 . The openings  251  are flanked by angled receiving surfaces  252  which ease accurate placement of said segmented helical wedges  152 . Each of said plurality of openings  251  comprises an adjacent helicoidal opening  253  with a surface  170  complementarily shaped to the segmented helical wedges  152 .  
         [0090]     For installation, the receiver  114  is mounted on a soundboard by conventional means. The wedges on the output disk  247  on the voice coil actuator  90  are then aligned with the openings  251  on the receiver. The voice coil actuator is moved toward the receiver  114  such that the engagement wedges are in a position to rotationally engage helicoidal openings  253  and the surfaces  170 . Next, the voice coil actuator assembly  90  is rotated a partial turn which frictionally engages the receiver  114  and the output disk  247  and serves to transmit sound vibrations as well as mount the unit on the sound body. To evenly distribute the downward pressure forces between the output disk  247  and the receiver  114 , the distal surface  400  of the output disk can be convex as shown in  FIG. 6   a . As the output disk is compressed downward during installation, the convexity will flatten and disperse the downward forces more evenly.  
         [0091]     In this preferred embodiment the output disk is removably engaged to the receiver  114  using the wedges  152 . As shown in  FIGS. 5 and 6  in order to secure the position of the voice coil actuator and to maintain positive contact between the output disk  247  and the receiver  114 , a locking means comprising a locking snap wedge  184  which forms part of distal surface  150  is employed to prevent the output disk from counter rotating and diminishing contact pressure between the output disk  247  and said receiver  114 . The locking snap wedge  184  bears a curved sloped wedge surface  183  which when engagably rotated into receiver  114  will deflect inward until said locking snap wedge  184  attains a recess  185  in the protruding segmented wall  250  At this point the locking snap wedge  184  finds relief to the inward deflection and springs into the recess  185  where a locking surface  186  engages said wall  250  which prevents the output disk from counter rotating. As shown in  FIG. 6  and  FIG. 4 , at least one wedge  152   a  and preferably two wedges  152   a  arranged in opposition, are hinged by way of dedicated flexural hinges  182  associated with said distal surface  150  and openings  181  in said distal surface  150  of said output disk which permit inward deflection of the locking snap wedge  184 . To facilitate disengaging the voice coil actuator assembly  90 , release tabs  187  are provided in an opposed position. Compressing release tabs  187  deflect the portion of the distal surface  150  between the openings  181  and cause the locking snap wedges  184  to deflect inward disengaging the locking snap wedges  184  and permitting counter rotation of the voice coil actuator  90  for easy removal.  
         [0092]     An alternative coil former suspension is shown in  FIG. 7 . The electrical current conductive coil  106  is wound on a coil former  107  that mechanically couples the electro-dynamic force into the desired acoustic structure. The coil former  107  in this configuration uses multiple spider suspension  111  and  111   a  elements to radially align the coil former  107  with the magnetic gap  124 . The spider elements permit axial displacement of the coil former  107  while restricting rocking motion or other out of plane motions that will cause the coil former  107  to strike or rub the permanent magnet  105  or the outer wall  108  of the channel  103 .  
         [0093]     The inertial type voice coil actuator of the present invention will often be used in conjunction with a drywall type soundboard. Typical wall construction technology is considered in a modification of the preferred embodiment wherein said integrated mounting apparatus comprises a voice coil actuator retainer  200  and said output disk  112  as shown in  FIG. 8 . The retainer  200  is used to affix the voice coil actuator to wall cladding. In order to affix the voice coil actuator to a soundboard where standard wall construction methods are considered, the voice coil actuator assembly  90  with its output disk  112  is coupled with retainer  200  which, in turn, is provided means for affixing to a wall stud  202 . Said means for affixing comprises a front depth registration means  203  referencing the surface of the stud  202  to which wall cladding will be applied, a brace  206 , at least one securing tab  204 , and at least one hole  205 . Once registered using these surfaces, the retainer  200  is secured using screws or other mechanical means and as shown in the preferred embodiment by way of said at least one securement tab  204  which is used in conjunction with said at least one hole  205  to screw or otherwise firmly affix retainer  200  to the wall stud  202 . It should be noted that each said at least one hole  205  is in a position where it is easily accessed in order to facilitate the installation of the retainer  200 .  
         [0094]     This third embodiment as shown in  FIGS. 8-13  gives full consideration to the sequencing used in standard wall construction, whereby the retainer  200  is mounted to stud member  202  after the wall framing is fabricated. Once retainer  200  is affixed, voice coil actuator assembly  90  is inserted into retainer  200  following the center axis of the voice coil actuator assembly  90  as shown in  FIG. 9  and  FIG. 10 . Receiving means  210  is included to secure said voice coil actuator assembly. Said means  210  may be as simple as a “c” opening in which said actuator is placed. Receiving means  210  as shown in  FIGS. 8-13  comprises a receiving cavity, a plurality of horizontal rib guides  209  and  211 , as well as vertical ribs  208 . Said voice coil actuator further comprises at least one electrical contact  214 . Said retainer  200  further comprises at least one sprung electrical contact  215 . As the voice coil actuator is inserted into receiving cavity  210 , it is slidably guided by horizontal rib guides  209  and  211 , as well as vertical ribs  208  which are essentially concentric with the external surface of voice coil actuator assembly  90 . The rotational orientation of the voice coil actuator assembly  90  is governed by co-locating registration means such that said contacts  214  and  215  are in electrical communication. Preferably, said co-locating means comprises a contact protrusion  212  on said voice coil actuator, which nests with a contact protrusion opening  213  on the retainer  200 . Voice coil electrical contacts  214  are guided in place to come in contact with said at least one sprung electrical contacts  215 . The semi circular form of the sprung contacts  215  provides a brushing contact means with voice coil actuator contacts  214 .  
         [0095]     The voice coil actuator may be affixed to the wall using an adhesive on the output disk  112 . The voice coil structure must be free to move axially so as to generate fore aft energy impulses. The electrical contact means  214  and  215  as described, permits free fore aft movement of the voice coil actuator while maintaining constant electrical contact. The voice coil actuator assembly  90  acts as a cassette when inserted into the receiving cavity  210  providing ease of installation and removal. Electrical contact is made automatically and independently of the installer. It should be noted that the illustrated depiction of this electrical contact means is specific to the preferred embodiment, as there are many other obvious means of making electrical contact with the voice coil actuator.  
         [0096]     To further describe the installing of voice coil actuator with retainer  200 , the voice coil actuator assembly  90  is slidably joined along its center axis that is coaxial with said receiving cavity  210 . As the output disk  112  of the voice coil actuator is inserted in said cavity  210 , the output disk  112  makes contact with a perimeter ring  216  which is semi-compressible and whose return forces diminish with time and will eventually set in the compressed, deformed position. The perimeter ring  216  acts to push the output disk  112  in front of the front surface of the retainer  200 . In doing so, the front surface of the output disk  112  is projected into a position in front of registration means  203  which will interface with the wall cladding material once installed. With output disk  112  in such an outward position, when drywall or other wall cladding material is affixed to the wall studs it will push on the output disk  112  creating compressive forces and as a result compress the perimeter rings  216 . An adhesive may be applied to the output disk prior to affixing the wall cladding material so as to create a bond between the output disk  112  and the wall cladding material. The perimeter ring  216  acts to ensure that positive pressure is applied to the interface between the output disk and the wall cladding material. Due to the deformation set properties of the perimeter rings  216 , after a period of time the return forces of the perimeter ring will diminish to negligible values, leaving the voice coil actuator supported axially by the support ribs  208  of the retainer  200 .  
         [0097]     Means for retention  217  are provided to ensure the voice coil actuator does not fall to the ground after insertion into the retainer cavity  210 , and before the wall cladding material is applied. Said means for retention are preferably a snap  217  on retainer  200  used in conjunction with a mating protrusion  218  on voice coil actuator assembly  90  and is more specifically shown in  FIG. 11 . The nature of the snap  217  is only to provide a means of stopping the voice coil actuator from dislodging from cavity  210 . As previously described, the voice coil actuator must be able to move axially fore and aft along its central axis to effectively transmit energy to the soundboard represented as drywall in this preferred embodiment. The space  219  between the snap  217  and the mating protrusion  218  demonstrates a positive retention of the voice coil actuator, while permitting small axial movement.  
         [0098]      FIG. 12 ,  FIG. 13  and  FIG. 8  show the prolongation of each said at least one sprung contact  215 . Each said sprung contact  215  is formed in such a way as to extend from its contact point with each of said at least one voice coil actuator contacts  214  to attach electrical wires which feed the voice coil actuator. The sprung contacts  215  of the preferred embodiment are formed of flat strip type conductive material, which registers in a raceway  222 . Each contact  215  comprises at least one surface  223  formed to extend past a retainer wall  224 , at least one threaded hole  220  to receive a binding post to affix electrical wires which send power and signal to drive voice coil actuator, and at least one opening  221  to allow electrical wires to be threaded through to access the wire contact surfaces  223  of contacts  215 . A cavity  225  is recessed in said retainer  200  to provide clearance for wire binding posts and ensures the length of the wire binding posts are less than the depth of the cavity  225  so as not to interfere with the wall cladding material&#39;s installation. Reinforcing ribs  207  are shown, and prevent reward torque or bending of the retainer part  200  when wall cladding material such as drywall is installed and exerts torque forces through the voice coil actuator and the retainer  200 . A combination of structural elements forming part of retainer  200  further assist with preventing bending or displacement of retainer  200  when the wall cladding material is applied as demonstrated by perimeter wall  226 .  
         [0099]     It should be noted that the preferred embodiment may be retrofitted to an existing wall by cutting a hole in the wall cladding material within the proximity of a wall stud reinforcing member and affixing the retainer  200  and voice coil actuator assembly  90  to any wall stud member. As the retainer  200  is cantilevered from a singular wall stud, and is of a distance less than one half of the distance between wall studs to the center axis of the voice coil actuator  200  in order to reduce resonant frequencies, the hole size required for the retrofitting would be small thus reducing the impact of retrofitting. Once installed, the wall surface is closed using standard construction practices.  
         [0100]     An additional integrated mounting system is shown in  FIG. 22  for intrawall installations. This integrated mounting system comprises the output disk  112  in acoustic communication with said coil former  107 , means to adjustably associate said inertial type voice coil actuator  920  with an infrastructure  950  comprising a first stud  900 , and a second stud  902 , and a threaded post element  930  extending outwardly from said bottom plate. The system further comprises a bracket  910  extending essentially from said first stud  900  to said second stud  902  and having an opening  905  complementarily sized to accommodate the threaded pole element  930  in which a threaded nut  940  is rotatably secured. When the threaded pole element  930  is inserted and the nut  940  is rotated, the relative distance between the bracket  910  and the actuator  920  can be adjusted substantially along the length of the threaded pole element  930 .  
         [0101]      FIGS. 23-26  show an alternative intrawall mounting system employing means to associate said actuator assembly  1119  with an infrastructure  1100 . Said means  1100  comprises a bracket having a structural web  1104  having an upper edge  1104   a  and a first surface  1118  with about a 90 degree angle  1107  therebetween, and a second surface  1105  generally perpendicular to said web  1104 . A retention means  1116  for said assembly  1119  is associated with said second surface  1105  such that the output disk  1106  is positioned adjacent a substrate. Said bracket further comprises at least one stabilizing wall  1103  for mechanically associating the first surface  1118  and the web  1104  relative to each other. Said wall  1103  extends generally perpendicular to and in contact with both said first surface  1118  and a portion of said upper edge  1104   a . In the preferred embodiment, said first surface  1118  comprises an opening through which a screw or other fastening means may be inserted for fastening said bracket to the infrastructure and the center of gravity of said actuator assembly  1119  is positioned such that torque forces on the bracket are minimized. In the preferred embodiment, the center of gravity of said actuator assembly  1119  is generally centered on the web  1104 .  
         [0102]     Further, the preferred embodiment contains a portion  1112  of the web  1104  which is not in contact with the wall  1103 . This portion acts as a controlled hinge and allows the retainer and actuator to flex relative to the infrastructure. The hinge can be of U, C, S or other suitable configuration. Finally, the output disk can be positioned relative to the substrate to allow for a variety of adhesive means for attaching it thereto.  
         [0103]     An alternate embodiment is shown in  FIG. 26 . Here, the angle  1107  between the structural web  1104  and the first surface  1118  is oriented in the opposite direction. This orientation allows the bracket to be used to appropriately mount the bracket such that a ceiling serves as the substrate.  
         [0104]     Another embodiment is shown best in  FIGS. 14 and 15 . In  FIG. 14  the integrated mounting apparatus includes output disk  112  comprising an annular hole  310 . Said output disk  112  is attached to a soundboard member  306  by means of a clamping mechanism  302 . Co-axially located with and generally covering the annular hole  310  of the output disk  112  is at least one high frequency speaker element  301 . Said at least one high frequency speaker element  301  is mounted in such a manner that the acoustic output side  312  of each said speaker element  301  is facing the preferred direction for transmitting the acoustic response of the high frequency element of the system. A vibration isolation pad  304  may be positioned to be in communication with said output disk  112  and with each said high frequency element  301 . The pad  304  will reduce the dynamic mass experienced by the voice coil actuator and minimize the structural vibration each high frequency speaker element  301 .  
         [0105]     Each said at least one high frequency speaker element  301  is positioned relative to the output disk  112  such that it penetrates through the soundboard  306  to minimize the protrusion of the high frequency speaker element  301  from the face of the soundboard  306 . The speaker element  301  may be mechanically fixated through conventional means to either the soundboard  306  or the output disk  112 .  
         [0106]     This embodiment may also include the co-location of a plurality of high frequency speaker elements  301  mounted on a fixture  305  to fixedly position the high frequency speaker elements in relationship to each other. Acoustic radiation from a speaker element typically shows a focusing of the energy as the excitation frequency of the speaker element is increased. In an effort to reduce the focusing of the acoustic radiation with increasing frequency the elements are arranged generally so that the main response axes of the elements are not parallel. This may be accomplished through many orientations. A hemi-spherical arrangement drives the high frequency elements  301  in phase so that it behaves in similitude with a pulsating sphere. The acoustic soundboard  306  in this instance acts as a baffle, increasing the overall efficiency of the system.  
         [0107]     The inertial type voice coil actuator illustrated in the drawings is to be viewed as having some important advantages, including improved force density, power rating and relatively constant sound quality, due to the radially polarized permanent magnets, uniform magnetic field, and heat dissipating characteristics of the magnetic viscous fluid and linear bearing system. In addition, advantages of simplified installation elements and high frequency response capability have been incorporated.  
         [0108]     The present invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described.