CA1067201A - Low frequency electro-acoustic transducer - Google Patents
Low frequency electro-acoustic transducerInfo
- Publication number
- CA1067201A CA1067201A CA240,018A CA240018A CA1067201A CA 1067201 A CA1067201 A CA 1067201A CA 240018 A CA240018 A CA 240018A CA 1067201 A CA1067201 A CA 1067201A
- Authority
- CA
- Canada
- Prior art keywords
- diaphragm
- movable
- diaphragms
- fixed
- acoustic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
- H04R9/06—Loudspeakers
- H04R9/063—Loudspeakers using a plurality of acoustic drivers
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Acoustics & Sound (AREA)
- Signal Processing (AREA)
- Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
- Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
Abstract
ABSTRACT
An electro-acoustic transducer for low frequencies ranging from 0-5000 Hz uses a plurality of parallel spaced apart, alternately disposed, fixed and movable diaphragms, in addition to which the motion inducing forces on the movable diaphragm are distributed over the area of the diaphragm and assembly of the electro-acoustic transducer achieved by the use of modular elements.
An electro-acoustic transducer for low frequencies ranging from 0-5000 Hz uses a plurality of parallel spaced apart, alternately disposed, fixed and movable diaphragms, in addition to which the motion inducing forces on the movable diaphragm are distributed over the area of the diaphragm and assembly of the electro-acoustic transducer achieved by the use of modular elements.
Description
~067201 This invention relates gene-ally to acoustic trans-ducers and in particular to electro-acoustic transducers in the low frequency range.
The basic principle of the present'invention is dis-closed in applicant's prior U.S. patent No. 3,636,278, issued January 18, 1972.
The present invention represents an improvement on the basic concept and a specific configuration and method of construction for such a sound reproduction device in the low frequency range from about 0 to 5000 Hz. The coverage of this range might also be accomplished using two electro-acoustic transducers using the concept.of the present invention with one dimensioned to reproduce sound in the 0-500 Hz range and the other to reproduce sound in the 500-5000 Hz range.
Prior to the invention of the electro-acoustic trans-ducer disclosed and claimed in applicant's prior issued patent, the majority of transducers used to produce sound in 'the low fre-quency range utilized light weight cones driven by a coil attached to a cylinder and suspended in a magnetic field.
In such devices, and for that matter in any vibrating diaphragm driven by a motion inducing force located at one point or at a small area on the diaphragm, all parts of the diaphragm will not be moving in the same direction with the same velocity for the same distance or at the same time due'to the flexibility of the diaphragm material as well as the assymetric forces at the point of attachment of the diaphragm to the surrounding frame and the inertial forces of the air against the diaphragm.
.The prior art methods used to correct the above problems usually resulted in a configuration of foam plastic filled cones .~
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67ZOl in which the base of the cone was used as the air driving sur-face and the apex of the cone as the point of application of the motion inducing force. Such a confi~uration generally required large driving forces to overcome the inertial forces of the large mass of the foam filled cone.
SUL~MARY OF ~HE INVENTION
The present invention relates to a low frequency electro-acoustic transducer comprising a plurality of spaced apart, generally parallel arranged, alternately disposed fixed and movable diaphragms defining a plurality of narrow air spaces having open sides facing in opposite directions. Each of the fixed diaphragms comprises, a first acoustic barrier disposed generally parallel and spaced apart from the movable diaphragm, a second barrier attached to the first acoustic barrier and extending approximately one-half the periphery of the first acoustic barrier and depending upwardly therefrom, a third acous-tic barrier attached to the first acoustic barrier and depending downwardly therefrom oppositely disposed from the second barrier, means for stacking and connecting like fixed diaphragms to each other to define a stack of fixed diaphragms, the stack defining the plurality of narrow air spaces having open sides facing in opposite directions. Each of the movable diaphragms comprises, a sheet member having disposed thereon a plurality of upwardly and downwardly protruding cones arranged in ordered array, each cone having an apex and a base, disposed with the bases adjacent one another, and means connected at the apex of àt least three of the cones for moving the movable diaphragm alter~ately toward and away from the fixed diaphragm.
The basic principle of the present'invention is dis-closed in applicant's prior U.S. patent No. 3,636,278, issued January 18, 1972.
The present invention represents an improvement on the basic concept and a specific configuration and method of construction for such a sound reproduction device in the low frequency range from about 0 to 5000 Hz. The coverage of this range might also be accomplished using two electro-acoustic transducers using the concept.of the present invention with one dimensioned to reproduce sound in the 0-500 Hz range and the other to reproduce sound in the 500-5000 Hz range.
Prior to the invention of the electro-acoustic trans-ducer disclosed and claimed in applicant's prior issued patent, the majority of transducers used to produce sound in 'the low fre-quency range utilized light weight cones driven by a coil attached to a cylinder and suspended in a magnetic field.
In such devices, and for that matter in any vibrating diaphragm driven by a motion inducing force located at one point or at a small area on the diaphragm, all parts of the diaphragm will not be moving in the same direction with the same velocity for the same distance or at the same time due'to the flexibility of the diaphragm material as well as the assymetric forces at the point of attachment of the diaphragm to the surrounding frame and the inertial forces of the air against the diaphragm.
.The prior art methods used to correct the above problems usually resulted in a configuration of foam plastic filled cones .~
~ rm~
67ZOl in which the base of the cone was used as the air driving sur-face and the apex of the cone as the point of application of the motion inducing force. Such a confi~uration generally required large driving forces to overcome the inertial forces of the large mass of the foam filled cone.
SUL~MARY OF ~HE INVENTION
The present invention relates to a low frequency electro-acoustic transducer comprising a plurality of spaced apart, generally parallel arranged, alternately disposed fixed and movable diaphragms defining a plurality of narrow air spaces having open sides facing in opposite directions. Each of the fixed diaphragms comprises, a first acoustic barrier disposed generally parallel and spaced apart from the movable diaphragm, a second barrier attached to the first acoustic barrier and extending approximately one-half the periphery of the first acoustic barrier and depending upwardly therefrom, a third acous-tic barrier attached to the first acoustic barrier and depending downwardly therefrom oppositely disposed from the second barrier, means for stacking and connecting like fixed diaphragms to each other to define a stack of fixed diaphragms, the stack defining the plurality of narrow air spaces having open sides facing in opposite directions. Each of the movable diaphragms comprises, a sheet member having disposed thereon a plurality of upwardly and downwardly protruding cones arranged in ordered array, each cone having an apex and a base, disposed with the bases adjacent one another, and means connected at the apex of àt least three of the cones for moving the movable diaphragm alter~ately toward and away from the fixed diaphragm.
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Figure 10 is an elevational sectional view of a second embodiment of a rigid base diaphragm.
Figure 11 is an elevational sectional view of the movable diaphragm configuration of Figures 7 and 8 showing the beaded edge configuration in greater detail.
Figure 12 is an elevational sectional view of the movable diaphragm configuration of Figures 7 and 8 showing the vertical tip edge configuration in greater detail.
Figure -13 is an isometric overall illustration of a cylindrical configuration of the low frequency electro-acoustic transducer of the present invention.
Figure 14 is an elevational sectional view of the cylindrical speaker of Figure 13 taken at lines 14-14.
Figure 15 is a top view of a typical movable diaphragm as used in the cylindrical low frequency electro-acoustic trans-ducer of Figures 13 and 14.
Figure 16, located on the fifth sheet of drawings, is an elevational sectional view of the movable diaphragm of Figure 15 taken at line 16-16.
Figure 17, located on the fifth sheet of drawings, is an elevational sectional view of the movable diaphragm of Figure 15 taken at line 17-17.
Figure 18 is an isometric view of a typical movable fixed diaphragm unit to achieve a cylindrical low frequency elec-tro-ac~ustic transducer.
Figure 19 is a partial sectional elevational view of a typical cylindrical low frequency electro-acoustic transducer utilizing the modular fixed diaphragm units of Figure 18 and the movable diaphragm units as illustrated in Figures 15-17.
,.~, ~ - 4 -r~,// ..-.~, DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to Figure 1, the low frequency electro-acoustic transducer device 10 of the present invention comprises, basically, a driver section 11 on which is mounted an acoustic transducer or air motion transformer section 12 comprising a plurality of modular transducer assemblies 14.
With reference to Figure 2, driver section 11 comprises a housing 16 containing permanent magnet assembly 17 having an air gap 18 in which is suspended driving coil 19.
Attached to driving coil 19 are a number of drive rods 21 which are distributed uniformly about the periphery of drive coil 19 and are also connected along their length to movable diaphragms 23a through 23f.
Acoustic transducer or air motion transformer section 12 comprises, basically, a bottom end block 26 and a top end block 27 in between which are disposed modular transducer assemblies 14 which, in turn, comprise diaphragm spacer blocks 28a through 281 which are connected, on one side, to movable diaphragm 23 (one of diaphragms 23a - 23f), and on the other side to fixed diaphragm 30 (one of diaphragms 30a - 30e).
When assembled, modular transducer assemblies 14 thus define a plurality of narrow air spaces having open sides al-ternately.facing in opposite directions.
To maintain movable diaphragms 23a - 23f in spaced apart relation to fixed diaphragms 30a - 30e and inside surfaces 31 and 32, respectively, of bottom and top end blocks 26 and 27, a flexible membrane 33 is connected between spacer blocks 28a - 281 and the periphery of movable diaphragms 23a - 23f.
Drive rods 21 can be fabricated from any light weight ~m /~
rigid material. Satisfactory results have been achieved using narrow paper cylinders similar to "soda straws" which have good compression and tensile strength properties.
To permit interconnection of movable diaphragms 23a -23f, a hole 34 is provided in fixed diaphragms 30a - 30e which are adapted to accommodate and be spaces apart from drive rods 21.
With reference to Figure 3, there is illustrated an exploded view of acoustic transducer section 12 of Figure 2 showing the method of assembly and shape of the parts in greater detail.
In particular, diaphragm spacer blocks 28 generally comprise a top and bottom surface surrounding a section of a circular opening 36 and adapted to receive and be attached to movable diaphragm 23 on one side and fixed diaphragm 30 on the other side. Spacer block 28 is fabricated out of a generally rectangular block in which a major portion of one corner is removed leaving three corners, two of which are provided with alignment and assembly holes 37 which are adapted to receive ten-sion rods 38 to hold the entire transducer device together.
As can be seen from Figure 3, each adjacent spacer block is placed with its open side facing in the opposite direc-tion.
Operation of the electro-acoustic transducer of the present invention can be seen from Figure 2, which operation is basically one of applying an alternating direction force to diaphragms 23a - 23f causing them to move alternately toward and away from fixed diaphragms 30a - 30e to drive air in and out of the space between each fixed diaphragm 30a - 30e and movable diaphragm 23a - 23f, respectively.
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For example, when movable diaphragm 23b moves upward toward ~ixed diaphragm 30b, there is a compression of the air mass between diaphragms 23b and 30b above diaphragm 23b causing a flow of air out of the cavity as indicated by arrow 40, while, at the same time, there is a rarefaction of the air mass between diaphragms 23b and 30a, below diaphragm 23b, causing a flow of air into the cavity as indicated by arrow 41.
Thus, in accordance with applicant's prior patent, a large amount of air is moved with a relatively small amount of kinetic energy of the moving parts of the speaker.
However, to achieve ideal sound reproduction, each moYable diaphragm 23a - 23f, as well as the whole assembly of diaphragms including drive rods 21, must operate as a rigid unit. In addi-tion, any distortion caused by the flapping of the unsupported portion of diaphragms 23a - 23f, longitudinal elastic deformation of drive rods 21 and assymetric forces caused by the flexible membrane connection between the movable diaphragms and the spacer blocks must be corrected or eliminated.
To increase the rigidity of movable diaphragms 23a -23f, they have, for the embodiment shown in Figures 1 - 3~ been fabricated in the form of two concentric conical sections with drive rods 21 attached to each movable diaphragm at the inter-section of the two conical sections.
To dampen longitudinal resonance in rods 21~ a terminator 43, shown in greater detail in Figure 4, is connected between the ends of rods 21, distal driving coil 19, and top end block 27.
Terminator 43 comprises a generally resilient material having some viscous properties sufficient to dampen any reflected _~, I . . .
~067;~01 longitudinal vibrations in rods 21.
It has been found that, of the total energy required to drive the movable diaphragms of the present invention, three-quarters of the energy is transferred to the air mass and one-quarter is used to accelerate and decelerate the mass of the diaphragms, coil and drive rods.
Although not large, there are reaction forces acting upon magnetic assembly 17 and the rigid structure comprising housing 16 and the rigid framework of air motion transformer section 12 which can cause the unit to vibrate.
One technique for counteracting such vibration prob-: lems is to provide a double ended dri~e unit such as that shown in Figure 2A. For example~ by placing two acoustic devices together with either the two driYer units 11 and 11' end-to-end, or the two air motion transformer units 12 and 12' end-to-end, as shown in Figure 2A, and with each drlver unit 11 and 11' connected to operate push-pull, that is~ the movable diaphragms in transformer unit 12 and 12' are caused to move simultaneously toward and away from each other, the vibratory forces in one unit will counteract the vibratory forces in the other unit.
A more complete embodiment of the present invention is illustrated in Figures 5, 6, 7 and 8 which utilizes a rec-tangular movable diaphragm and a fixed diaphragm incorporated into the means ~or spacing apart the movable diaphragms.
With particular reference to Figure 5, there is shown an exploded view of the top portion of double ended drive trans-ducer 50 which is shown as a partial cut-away elevational view in Figure 6.
Transducer 50 comprises an upper and lower drive rm/~
assembly 51a and 51b, respectively, between which are disposed a plurality of modular transducer assemblies 54.
Both upper and lower drive assemblies 51a and 51b are identical and, for the purpose of description, the suffix letters will not be used when referring generally to these drive assemblies.
Drive assemblies 51 comprise, basically~ a housing 55 containing a magnet assembly 56 containing two cylindrical gaps 57 and 58 adapted to receiYe cylindrical drive coils 60 and 61, respectively. A plurality of drive rods 63 and 64 are connected to drive coils 60 and 61, xespectiYely, at one end and : to drive coils 60' and 61~ at their other end.
Between upper drive assembly 51a and lower drive assembly 51b are disposed a plurality of transducer modules 54, each of which comprises a molded spacer and fixed diaphragm unit 66 and a movable diaphragm unit 67.
Spacer-fixed diaphra~m unit 66 comprises a fixed diaphragm 68 defining a plane dividing unit 66 into upper and lower halves 69 and 70, respectively, with each half enclosed by oppositely disposed upper and lower acoustic housing or barriers 71 and 72, respectively, each defining oppositely facing upper and lower openings 73 and 74, respectively, on opposite sides of diaphragm 68.
~ttached to the top surface or edge 76 of upper acous-tic barrier 71 and the bottom surface or edge 77 of lower acoustic barrier 72 between each spacer-fixed diaphragm unit 66, is movable diaphragm unit 67 comprising a generally planar diaphragm 79 that has been rigidized or deformed to achieve a rigid unit. A flexible membrane 80 is connected between diaphragm _ 9 _ rm/l(~
~067201 79 and surfaces 76 and 77 to allow am~le movement of diaphragm 79 toward and away from fixed diaphragm or surface 68 although, provided certain precautions are taken, a narrow space without membrane 80 can also be used as described below. Movable diaphragm unit 67 is shown in greater detail in Figures 7 and 8 with Figure 7 showing a section through a typical diaphragm unit 67 taken at lines 7-7 for the isometric view of diaphragm unit 67 shown in Figure 8.
MoYable diaphra~m 67~ in particulax~ comprises a plur-ality of alternately upward and downward protruding rigidizingnodes 81 and 82, respectively, arranyed in an ordered array so : that drive rods 63 and 64 are attached thereto at the apex 83 or nadir 84 of each node 81 and 82, respectively.
It has been found that satisfactory rigidity is achieved if nodes 81 and 82 define conical sections with a surface geometry between cones analogous to that of an elastic surface connecting the bases of the cones.
For example, if an elastic surface or sheet were stretched Detween the bases of cones represented by nodes 81 and 82, the curved surface or saddle 86 ~ould result. This elastic sheet could be defined by a'metallic sheet deformed under hydraulic pressure which is used as the mold for a plastic or paper diaphragm.
of co,urse', other surfaces could be used which are de-fined by a mathematical equation such as for hyperbolic para-boloids which may also be used to rigidize diaphragm 67.
To achieve even greater rigidity of the movable diaphragm unit comprising diaphragms 67 and drive rods 63, a rigid base diaphragm 90 can be used as illustrated in Figure 9.
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Base diaphragm 90 comprises an upper rigidized movable diaphragm 92 and a lower rigidized diaphragm 93, each of which is identical in structure and shape to movable diaphragm 67 of Figure 8.
Upper diaphragm 92, similar to diaphragm 67, comprises a plurality of alternately upward and downward protruding nodes 95 and 96, respectively, arranged in ordered array.
Lower diaphragm 93, also similar to diaphragm 67, comprises a plurality of alternately upward and downward pro-truding nodes 98 and 99, respectively, arranged in ordered array with upward protruding nodes 98 of lower diaphragm 93 attached to downward protruding nodes 96 of upper diaphragm 92.
Cylindrical drive coil 60 is attached to drive rods 63 while drive rods 64 are connected to drive coil 61 thus providing a rigid connection with drive rods 63, and 64 attached to the peaks of upward and downward nodes of diaphragms 92 and 93 in order to distribute the forces over the surface of diaphragms 67.
It can be seen that such a construction defines a plurality of cantilevered units offering a very rigid structure.
A second method of achieving greater rigidity is shown in Figure 10 in which a conical section is molded from a light weight foam plastic, common in the art, such as polystyrene, to define a rigid base 105 comprising a top surface 106 having a plurality of upward and downward protruding peaks 107 and valleys 108, respectively, identical in shape to nodes 83 and 84 of diaphragms 67 of Figure 8 and a frusto-conical body portion 101 to which is attached a cylindrical drive coil 110.
It can be seen that the forces transmitted by drive coil 110 are distributed over top surface 106, which are in turn rm/
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distributed equally among drive rods 63 and thus distributed over the surface of diaphragms 67 (Figure 5).
Double ended drive transducer 50 operates in the same - manner as electro-acoustic transducer 10 previously described, however, a number of advantages are achieved, in particular, the use of driving coils at each end of drive rods 63 and 64 permit a greater number of modular transducer assemblies 54 to be utilized in one unit when compared to the number of acoustic transducer sections 12 that can be used in electro-acoustic transducer device 10.
Movable diaphragm unit 67 can be fabricated from any light weight material having good tensile and compressive strength properties such as layered cellulose fibers or paper pulp similar to the material used in speaker cones of the prior art or polyethylene, acrylic or slmilar plastic material well known in the art.
Fixed diaphragm-spacer unit 66 can be fabricated, for example, by injection molding techniques from similar plastic materials well known in the art.
~0 With respect to the use of flexible membrane 80 (Figure 5) and flexible membrane 33 (Figure 2), as mentioned preYiously, the need for such membranes may not be necessary, in fact, the absence of such a membrane is desirable.
. In the case of membrane 33, which is used for a circular diaphragm, the use of a circular membrane intr~duces non-linear forces at the periphery of movable diaphragm 23 causing certain types of harmonic distortion to develop analogous to the distor-tions found in other Yibratory diaphragms such as drum heads, The matter is somewhat improved by the use of rectangular rm~
1067Z(~l -membrane 80 incorporated in the embodiment illustrated in Figure 5.
In Figure 5, the forces caused by the elastic deforma-tion of membrane 80 still cause certain harmonic distortions to develop but on a smaller scale.
Two embodiments illustrating movable di~phragm config-urations without a membrane connecting the movable diaphragm to the fixed portion of the transducer are shown in Figures 11 and 12.
In Figure 11, moYable diaphragm 103 is identical in structure to diaphragm 67 of Figure 5, however, with the excep-tion that a reinforcing bead 115 is connected to or incorporated about the periphery of diaphragm 103 to further rigidize the diaphragm. Further, a lip 116 is provided proximate reinforcing bead 115 which is attached to acoustic barrier 71 and 72.
To avoid too great a loss in sound volume and efficiency, the spacing of bead 115 from lip 116 should be generally no greater than a fraction of a millimeter preferably less than 1 mm.
~ he length of lip 116 is determined by the maximum displacement of movable diaphragm 103 which in turn is determined by the length of the magnetic gap of magnet assembly 56 (Figure 5).
In Figure 12, movable diaphragm 103 is provided with a reinforcing wall or barrier 118 rather than a bead which performs the dual function or further rigidizing the diaphragm and pro-viding a barrier to prevent air from leaking past lip 109 when diaphragm 103 is at its upper or lower limit of travel, which travel is normally greater than the width or thickness of lip 109.
Similar to Figure 11, the spacing of barrier 118 from rm/~
lip 109 should be preferably smaller than one millimeter. The criteria being, in all cases, that the spacing should be small enough to offer a sufficient resistance to the passage of air around the diaphragm to avoid an undesirable loss in efficiency of the transducer.
A third embodiment of the low frequency electxo-acoustic transducer 210 of the present invention is illustrated in Figures 13 through 17.
- With reference to Figure 13, the electro-acoustic trans-ducer 210 comprised, basically, a driver section 211 above which is mounted a cylindrical acoustic transducer or air motion trans-former section 212, the two sections being enclosed in a cylin-drical housing member 214.
With reference to Figure 14, cylindrical housing member 214 comprises a plurality of radially disposed, semi-cylindrical slots 215 facing in opposite directions and alternately disposed at equal intervals along housing 214, with the exception of that portion of housing 214 occupied by driver section 211.
~river section 211 comprises a permanent magnet assembly 217 having an air gap 218 in which is disposed driver coil 219.
Acoustic transducer or air motion transformer section 212 comprises, basically, a plurality of movable diaphragms 223 (one of diaphragms 223a - 230e) connected through drive rods 221 to drive coil 219 with a like plurality of fiXed diaphragms 230(one of diaphragms 230a - 230e) disposed alternately between movab1e diaphragms 223 and attached to housing 214. In particular, fixed diaphragm 230 are attached to housing 214 at the connector portion 231 between each slot 215 to define a cavity or space 240 open at slot 215 and bounded by fixed diaphragm 230, connector portion 231 rm/l~
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and movable diaphragm 223.
Movable diaphragm 223 is shown in greater detail in Figure 15 and comprises a plurality, six in the embodiment illus-trated, of alternately upward and downward protruding rigidized nodes 281 and 282, respectively, arranged in a circular array so that drive rods 221 are attached thereto at ape~ 283 or nadir 284 of each node 281 and 282, respectively.
Typically, nodes 281 and 282 can define 90 degree cones, i.e., the angle at the apex of the cone is a right angle.
It has been found that satisfactory rigidity is achieved if nodes 281 and 282 define conical sections with the transition from upward to downward projecting nodes (cones) arranged so that a straight and level line can be drawn between cones, as for example, along cut lines 17-17 of Figure 15, as also can be seen from Figure 17.
Even with drive rods 221 attached to the apex 283 and nadir 284 of each node 281 and 282, respectively, certain un-desirable resonances and harmonic distortions may be developed within the geometry of movable diaphragm 223 and within conical nodes 281 and 282 similar to the resonances described above for large cone drive speakers of the prior art.
In the present invention, because the conical nodes 281 and 282 are small, the resonance or distortion is small, however, even these harmonic distortions can be eliminated by the use of slots 235 disposed along the straight line section between conical nodes 281 and 282, as can be seen in Figure 15. Each slot 235 is filled with viscous material such as to prevent any vibrational distortion from travelling between conical nodes 281 and 282.
Typically, movable diaphragms 223 are fabricated from a rm/~C~
1067Z~l generally stiff plastic mate~ial such as polystyr~ne or the like.
For a three inch diameter diaphragm, the weight of the diaphragm will be, typically, about 1 gram.
With reference to Figure 16, there is illustrated a sec-tion through both upward and downward projecting nodes 281 and 282, respectively, showing their conical shape and the shape of the transition section between conical sections.
With reference to Figure 17, there is illustrated a sec-tion through movable diaphragm 223 taken at line 17-17 of Figure 15.
The section is taken through slots 235 and illustrates the geometry of movable diaphragm 223 where a straight and level line can be drawn across diaphragm 223 between conical sections.
As can be seen from Figure 14, the diameter of driYe coil 219 is arranged to be coincident with the diameter of the circle defined by the apexes of nodes 281 and 282 so that coil 219 can be attached directly to nodes 282 and the underside of diaphragm 223e including the underside of node 281 and also be coincident at each apex 283 and 284 with the point of attachment of drive or push rods 221.
Operation of electro-acoustic transducer 210 illustrated in Figures 13-17 is basically one of applying an alternating direc-tion force to diaphragms 223a-223e by means of the application of an alternating current to drive coil 219, which causes diaphragms 223a-223e to move alternately toward and away from fixed diaphragms 230a-230e to drive air in and out of cavity or space 240 between each fixed diaphragm 230a-230e and movable diaphragm 223a-223e, respectively.
For example, when mo~able diaphragm 223b is moved upward toward fixed diaphragm 230b, there is a compression of the air mass between diaphragm 223b and 230b causing air to flow out of rm/~
cavity 240c, a~ indicated by arrow 241, while, at the same time, there is a rarefaction of the air mass between diaphragm 223a and 230b, below diaphragm 223a causing a flow of air into cavity 240b, as indicated by arrow 242.
Thus~ a large amount of air is moved with a relatively small amount of kinetic energy.
For the purpose of simplifying the method of manufactur-ing the air motion transformer section 212 of Figures 13 and 14, this section can comprise a pluralit~ of modular fixed diaphragm units 310, as shown in Figure 18, which are adapted to stack as shown in Figure 19. Between each stacked unit 310 is disposed a movable diaphragm 223, the same as shown in Figures 16 and 17.
With reference to Figure 18~ fixed diaphragm unit 310 comprises a generally planar fixed plate portion 312, having deformed therein six equi-angularly spaced alternately upward protruding nodes or cones 314a-c and downwardly protruding nodes or cones 315a-c.
Nodes or cones 314 and 315 are arranged in the same relative location as nodes or cones 281 and 282, respectively, of movable diaphragm 223 so that, when diaphragm 223 is in position, upward protruding nodes or cones 314 of fixed diaphragm 310 and upward protruding nodes or cones 281 of movable diaphragm 223 will tend to nest, that is, be spaced apart but still fit or mate with each other. In a like manner downward protruding nodes or cones 282 of movable diaphragm 223 and downward protruding nodes or cones 315 of the next fixed diaphragm 310 below, will tend to nest.
At the apex of both cones 3I4 and 315 is a hole 316 and 317, respectively, defined by short cylindrical sections 318 1067Z0~
and 319, respectively.
A semi-cylindrical acoustic barrier 320 is disposed on the top surface of planar portion 312 terminating at each end by an upper end spacer 321 whose end surface is coincident with the diameter of circular planar portion 312.
Two intermediate spacer members 322a and 322b are disposed at equal interyals about acoustic barrier 320.
Disposed on the lower or underside of planar portion 312 is an identical configuration as that described above for the upper side, only positioned diametrically opposite the upper configuration.
For example, acoustic barrier 320', end spacer member 321' and inte.mediate spacer 322a' and 323b' (not shown) perform the same function as their counterpart above.
It will be noted that the height of end spacer 321 and intermediate spacers 322a and 322b are greater than the height of acoustic barrier 321 above planar portion 312. This greater height, that is, the difference in height between spacers 321, 322a and 322b and barrier 320, determine the width of the opening of slot 215, (Figure 13) for air motion transformer section 212 (Figures 13 and 14).
It will also be noted from Figure 19, that the top lip 323 of acoustic barrier 320 extends above corresponding lip 323' of acoustic barrier 320' of the next fixed diaphragm unit 310 above. This difference or "overlap" determines the maximum distance the movable diaphragm 223 will move within the assembled fixed diaphragm units 310.
It should also be noted that the outside diameter of movable diaphragm 223 is slightly less than the inside diameter of Xm/~
~067Z01 assembled acoustic barrier 320 and 320' such that diaphragm 223 moves up and down in the manner of a piston without touching or being connected to the walls of acoustic barrier 320 and 320'.
To assemble an air transformer section as shown in Figure 19, fixed diaphragm units 310 and moYable diaphragm 223 are alternately stacked as follows:
Movable diaphrasm drive rods 324 which are attached at one end to drive coil 219 (not shown in Figure 19~ are arranged to pass through holes 316 in cone sections 314 of fixed diaphragm unit 310 and be freely movable therein and extend upward for length corresponding to the number of movable diaphragms 223 being used for an air transformation section 212.
The bottom fixed diaphragm unit 310 is attached by means common in the art to the magnet assembly 217 (Figure 14) by means well known in the art.
Next movable diaphragm 223 is placed so that the drive rods 324 will pass through the apex 283 of nodes 281 and the apex 284 of nodes 282.
Moyable diaphragm 223 is adjusted along drive rods 324 until it is properly spaced from fixed diaphragm 310 at which point it is attached to drive rods 324 by means well known in the art such as an adhesive or glue.
A second fixed diaphragm unit 310 is then placed so that drive rods 324 will pass freely through holes 316 of cones 314 in fixed diaphragm unit 310 while drive rods 324 pass through holes '317. Diaphragm unit 310 is then adjusted along the rods until the top of end spacer 321 and intermediate spacers 322a and 322b of the lower diaphragm unit 310 come in contact with the underside of planar portion 312 of the upper diaphragm unit rm/~
310 and until the bottom of end spacers 321' and intermediate #pacers 322a' and 322b' come in contact with the top surface of planar portion 312 of the lower diaphragm unit 31~.
An adhesive or glue is applied to the surfaces of spacers 321 and 321' and intermediate spacers 322a, 322b, 322a' and 322b' where they contact the next modular section 310 to achieve a unified and ri~id structure.
Thus, it can be seen from Figure 19, a slot 327 is defined between lips 323 and the underside of planar portion 312.
Correspondingly, slot 327' is defined between lips 323' and the upper side of planar portion 312 of the next lowe~ diaphragm unit 310.
Therefore, an upward movement of drive rods 324 will result in air being forced out of slot 327 to the left, as indica-ted by arrows 329, while, at the same time, air is drawn or pulled into slot 327' from the right, as indicated by arrows 330.
Thus, air motion transformation is achieved whereby a small movement of diaphragm of 223 causes a large moyement of air in and out of slots 327 and 327'.
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` 1067Z01 l'HE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINE~D A~; FOLLOWS:
1. A low frequency electro-acoustic transducer com-prising a plurality of spaced apart, generally parallel ar-ranged, alternately disposed fixed and movable diaphragms defining a plurality of narrow air spaces having open sides facing in opposite directions, each of said fixed diaphragms comprising!
a first acoustic barrier disposed generally parallel and spaced apart from said movable diaphragm, a second barrier attached to said first acoustic barrier and extending approximately one-half the periphery of said first acoustic barrier and depending upwardly therefrom, a third acoustic barrier attached to said first acous-tic barrier and depending downwardly therefrom oppositely disposed from said second barrier, means for stacking and connecting like fixed diaphragms tc each other to define a stack of fixed diaphragms, said stack defining said plurality of narrow air spaces having open sides facing in opposite directions, each of said movable diaphragms comprising, a sheet member having disposed thereon a plurality of upwardly and downwardly protruding cones arranged in ordered array, each cone having an apex and a base, disposed with said bases adjacent one another, and means connected at the apex of at least three of said cones for moving said movable diaphragm alternately toward and ~way from said fixed diaphragm.
i~'f~' 21 ~
, -.;i~ ....
Figure 10 is an elevational sectional view of a second embodiment of a rigid base diaphragm.
Figure 11 is an elevational sectional view of the movable diaphragm configuration of Figures 7 and 8 showing the beaded edge configuration in greater detail.
Figure 12 is an elevational sectional view of the movable diaphragm configuration of Figures 7 and 8 showing the vertical tip edge configuration in greater detail.
Figure -13 is an isometric overall illustration of a cylindrical configuration of the low frequency electro-acoustic transducer of the present invention.
Figure 14 is an elevational sectional view of the cylindrical speaker of Figure 13 taken at lines 14-14.
Figure 15 is a top view of a typical movable diaphragm as used in the cylindrical low frequency electro-acoustic trans-ducer of Figures 13 and 14.
Figure 16, located on the fifth sheet of drawings, is an elevational sectional view of the movable diaphragm of Figure 15 taken at line 16-16.
Figure 17, located on the fifth sheet of drawings, is an elevational sectional view of the movable diaphragm of Figure 15 taken at line 17-17.
Figure 18 is an isometric view of a typical movable fixed diaphragm unit to achieve a cylindrical low frequency elec-tro-ac~ustic transducer.
Figure 19 is a partial sectional elevational view of a typical cylindrical low frequency electro-acoustic transducer utilizing the modular fixed diaphragm units of Figure 18 and the movable diaphragm units as illustrated in Figures 15-17.
,.~, ~ - 4 -r~,// ..-.~, DESCRIPTION OF THE PREFERRED EMBODIMENT
With reference to Figure 1, the low frequency electro-acoustic transducer device 10 of the present invention comprises, basically, a driver section 11 on which is mounted an acoustic transducer or air motion transformer section 12 comprising a plurality of modular transducer assemblies 14.
With reference to Figure 2, driver section 11 comprises a housing 16 containing permanent magnet assembly 17 having an air gap 18 in which is suspended driving coil 19.
Attached to driving coil 19 are a number of drive rods 21 which are distributed uniformly about the periphery of drive coil 19 and are also connected along their length to movable diaphragms 23a through 23f.
Acoustic transducer or air motion transformer section 12 comprises, basically, a bottom end block 26 and a top end block 27 in between which are disposed modular transducer assemblies 14 which, in turn, comprise diaphragm spacer blocks 28a through 281 which are connected, on one side, to movable diaphragm 23 (one of diaphragms 23a - 23f), and on the other side to fixed diaphragm 30 (one of diaphragms 30a - 30e).
When assembled, modular transducer assemblies 14 thus define a plurality of narrow air spaces having open sides al-ternately.facing in opposite directions.
To maintain movable diaphragms 23a - 23f in spaced apart relation to fixed diaphragms 30a - 30e and inside surfaces 31 and 32, respectively, of bottom and top end blocks 26 and 27, a flexible membrane 33 is connected between spacer blocks 28a - 281 and the periphery of movable diaphragms 23a - 23f.
Drive rods 21 can be fabricated from any light weight ~m /~
rigid material. Satisfactory results have been achieved using narrow paper cylinders similar to "soda straws" which have good compression and tensile strength properties.
To permit interconnection of movable diaphragms 23a -23f, a hole 34 is provided in fixed diaphragms 30a - 30e which are adapted to accommodate and be spaces apart from drive rods 21.
With reference to Figure 3, there is illustrated an exploded view of acoustic transducer section 12 of Figure 2 showing the method of assembly and shape of the parts in greater detail.
In particular, diaphragm spacer blocks 28 generally comprise a top and bottom surface surrounding a section of a circular opening 36 and adapted to receive and be attached to movable diaphragm 23 on one side and fixed diaphragm 30 on the other side. Spacer block 28 is fabricated out of a generally rectangular block in which a major portion of one corner is removed leaving three corners, two of which are provided with alignment and assembly holes 37 which are adapted to receive ten-sion rods 38 to hold the entire transducer device together.
As can be seen from Figure 3, each adjacent spacer block is placed with its open side facing in the opposite direc-tion.
Operation of the electro-acoustic transducer of the present invention can be seen from Figure 2, which operation is basically one of applying an alternating direction force to diaphragms 23a - 23f causing them to move alternately toward and away from fixed diaphragms 30a - 30e to drive air in and out of the space between each fixed diaphragm 30a - 30e and movable diaphragm 23a - 23f, respectively.
rm/~
For example, when movable diaphragm 23b moves upward toward ~ixed diaphragm 30b, there is a compression of the air mass between diaphragms 23b and 30b above diaphragm 23b causing a flow of air out of the cavity as indicated by arrow 40, while, at the same time, there is a rarefaction of the air mass between diaphragms 23b and 30a, below diaphragm 23b, causing a flow of air into the cavity as indicated by arrow 41.
Thus, in accordance with applicant's prior patent, a large amount of air is moved with a relatively small amount of kinetic energy of the moving parts of the speaker.
However, to achieve ideal sound reproduction, each moYable diaphragm 23a - 23f, as well as the whole assembly of diaphragms including drive rods 21, must operate as a rigid unit. In addi-tion, any distortion caused by the flapping of the unsupported portion of diaphragms 23a - 23f, longitudinal elastic deformation of drive rods 21 and assymetric forces caused by the flexible membrane connection between the movable diaphragms and the spacer blocks must be corrected or eliminated.
To increase the rigidity of movable diaphragms 23a -23f, they have, for the embodiment shown in Figures 1 - 3~ been fabricated in the form of two concentric conical sections with drive rods 21 attached to each movable diaphragm at the inter-section of the two conical sections.
To dampen longitudinal resonance in rods 21~ a terminator 43, shown in greater detail in Figure 4, is connected between the ends of rods 21, distal driving coil 19, and top end block 27.
Terminator 43 comprises a generally resilient material having some viscous properties sufficient to dampen any reflected _~, I . . .
~067;~01 longitudinal vibrations in rods 21.
It has been found that, of the total energy required to drive the movable diaphragms of the present invention, three-quarters of the energy is transferred to the air mass and one-quarter is used to accelerate and decelerate the mass of the diaphragms, coil and drive rods.
Although not large, there are reaction forces acting upon magnetic assembly 17 and the rigid structure comprising housing 16 and the rigid framework of air motion transformer section 12 which can cause the unit to vibrate.
One technique for counteracting such vibration prob-: lems is to provide a double ended dri~e unit such as that shown in Figure 2A. For example~ by placing two acoustic devices together with either the two driYer units 11 and 11' end-to-end, or the two air motion transformer units 12 and 12' end-to-end, as shown in Figure 2A, and with each drlver unit 11 and 11' connected to operate push-pull, that is~ the movable diaphragms in transformer unit 12 and 12' are caused to move simultaneously toward and away from each other, the vibratory forces in one unit will counteract the vibratory forces in the other unit.
A more complete embodiment of the present invention is illustrated in Figures 5, 6, 7 and 8 which utilizes a rec-tangular movable diaphragm and a fixed diaphragm incorporated into the means ~or spacing apart the movable diaphragms.
With particular reference to Figure 5, there is shown an exploded view of the top portion of double ended drive trans-ducer 50 which is shown as a partial cut-away elevational view in Figure 6.
Transducer 50 comprises an upper and lower drive rm/~
assembly 51a and 51b, respectively, between which are disposed a plurality of modular transducer assemblies 54.
Both upper and lower drive assemblies 51a and 51b are identical and, for the purpose of description, the suffix letters will not be used when referring generally to these drive assemblies.
Drive assemblies 51 comprise, basically~ a housing 55 containing a magnet assembly 56 containing two cylindrical gaps 57 and 58 adapted to receiYe cylindrical drive coils 60 and 61, respectively. A plurality of drive rods 63 and 64 are connected to drive coils 60 and 61, xespectiYely, at one end and : to drive coils 60' and 61~ at their other end.
Between upper drive assembly 51a and lower drive assembly 51b are disposed a plurality of transducer modules 54, each of which comprises a molded spacer and fixed diaphragm unit 66 and a movable diaphragm unit 67.
Spacer-fixed diaphra~m unit 66 comprises a fixed diaphragm 68 defining a plane dividing unit 66 into upper and lower halves 69 and 70, respectively, with each half enclosed by oppositely disposed upper and lower acoustic housing or barriers 71 and 72, respectively, each defining oppositely facing upper and lower openings 73 and 74, respectively, on opposite sides of diaphragm 68.
~ttached to the top surface or edge 76 of upper acous-tic barrier 71 and the bottom surface or edge 77 of lower acoustic barrier 72 between each spacer-fixed diaphragm unit 66, is movable diaphragm unit 67 comprising a generally planar diaphragm 79 that has been rigidized or deformed to achieve a rigid unit. A flexible membrane 80 is connected between diaphragm _ 9 _ rm/l(~
~067201 79 and surfaces 76 and 77 to allow am~le movement of diaphragm 79 toward and away from fixed diaphragm or surface 68 although, provided certain precautions are taken, a narrow space without membrane 80 can also be used as described below. Movable diaphragm unit 67 is shown in greater detail in Figures 7 and 8 with Figure 7 showing a section through a typical diaphragm unit 67 taken at lines 7-7 for the isometric view of diaphragm unit 67 shown in Figure 8.
MoYable diaphra~m 67~ in particulax~ comprises a plur-ality of alternately upward and downward protruding rigidizingnodes 81 and 82, respectively, arranyed in an ordered array so : that drive rods 63 and 64 are attached thereto at the apex 83 or nadir 84 of each node 81 and 82, respectively.
It has been found that satisfactory rigidity is achieved if nodes 81 and 82 define conical sections with a surface geometry between cones analogous to that of an elastic surface connecting the bases of the cones.
For example, if an elastic surface or sheet were stretched Detween the bases of cones represented by nodes 81 and 82, the curved surface or saddle 86 ~ould result. This elastic sheet could be defined by a'metallic sheet deformed under hydraulic pressure which is used as the mold for a plastic or paper diaphragm.
of co,urse', other surfaces could be used which are de-fined by a mathematical equation such as for hyperbolic para-boloids which may also be used to rigidize diaphragm 67.
To achieve even greater rigidity of the movable diaphragm unit comprising diaphragms 67 and drive rods 63, a rigid base diaphragm 90 can be used as illustrated in Figure 9.
rm J < ~ ~'~
Base diaphragm 90 comprises an upper rigidized movable diaphragm 92 and a lower rigidized diaphragm 93, each of which is identical in structure and shape to movable diaphragm 67 of Figure 8.
Upper diaphragm 92, similar to diaphragm 67, comprises a plurality of alternately upward and downward protruding nodes 95 and 96, respectively, arranged in ordered array.
Lower diaphragm 93, also similar to diaphragm 67, comprises a plurality of alternately upward and downward pro-truding nodes 98 and 99, respectively, arranged in ordered array with upward protruding nodes 98 of lower diaphragm 93 attached to downward protruding nodes 96 of upper diaphragm 92.
Cylindrical drive coil 60 is attached to drive rods 63 while drive rods 64 are connected to drive coil 61 thus providing a rigid connection with drive rods 63, and 64 attached to the peaks of upward and downward nodes of diaphragms 92 and 93 in order to distribute the forces over the surface of diaphragms 67.
It can be seen that such a construction defines a plurality of cantilevered units offering a very rigid structure.
A second method of achieving greater rigidity is shown in Figure 10 in which a conical section is molded from a light weight foam plastic, common in the art, such as polystyrene, to define a rigid base 105 comprising a top surface 106 having a plurality of upward and downward protruding peaks 107 and valleys 108, respectively, identical in shape to nodes 83 and 84 of diaphragms 67 of Figure 8 and a frusto-conical body portion 101 to which is attached a cylindrical drive coil 110.
It can be seen that the forces transmitted by drive coil 110 are distributed over top surface 106, which are in turn rm/
1067Z0~
distributed equally among drive rods 63 and thus distributed over the surface of diaphragms 67 (Figure 5).
Double ended drive transducer 50 operates in the same - manner as electro-acoustic transducer 10 previously described, however, a number of advantages are achieved, in particular, the use of driving coils at each end of drive rods 63 and 64 permit a greater number of modular transducer assemblies 54 to be utilized in one unit when compared to the number of acoustic transducer sections 12 that can be used in electro-acoustic transducer device 10.
Movable diaphragm unit 67 can be fabricated from any light weight material having good tensile and compressive strength properties such as layered cellulose fibers or paper pulp similar to the material used in speaker cones of the prior art or polyethylene, acrylic or slmilar plastic material well known in the art.
Fixed diaphragm-spacer unit 66 can be fabricated, for example, by injection molding techniques from similar plastic materials well known in the art.
~0 With respect to the use of flexible membrane 80 (Figure 5) and flexible membrane 33 (Figure 2), as mentioned preYiously, the need for such membranes may not be necessary, in fact, the absence of such a membrane is desirable.
. In the case of membrane 33, which is used for a circular diaphragm, the use of a circular membrane intr~duces non-linear forces at the periphery of movable diaphragm 23 causing certain types of harmonic distortion to develop analogous to the distor-tions found in other Yibratory diaphragms such as drum heads, The matter is somewhat improved by the use of rectangular rm~
1067Z(~l -membrane 80 incorporated in the embodiment illustrated in Figure 5.
In Figure 5, the forces caused by the elastic deforma-tion of membrane 80 still cause certain harmonic distortions to develop but on a smaller scale.
Two embodiments illustrating movable di~phragm config-urations without a membrane connecting the movable diaphragm to the fixed portion of the transducer are shown in Figures 11 and 12.
In Figure 11, moYable diaphragm 103 is identical in structure to diaphragm 67 of Figure 5, however, with the excep-tion that a reinforcing bead 115 is connected to or incorporated about the periphery of diaphragm 103 to further rigidize the diaphragm. Further, a lip 116 is provided proximate reinforcing bead 115 which is attached to acoustic barrier 71 and 72.
To avoid too great a loss in sound volume and efficiency, the spacing of bead 115 from lip 116 should be generally no greater than a fraction of a millimeter preferably less than 1 mm.
~ he length of lip 116 is determined by the maximum displacement of movable diaphragm 103 which in turn is determined by the length of the magnetic gap of magnet assembly 56 (Figure 5).
In Figure 12, movable diaphragm 103 is provided with a reinforcing wall or barrier 118 rather than a bead which performs the dual function or further rigidizing the diaphragm and pro-viding a barrier to prevent air from leaking past lip 109 when diaphragm 103 is at its upper or lower limit of travel, which travel is normally greater than the width or thickness of lip 109.
Similar to Figure 11, the spacing of barrier 118 from rm/~
lip 109 should be preferably smaller than one millimeter. The criteria being, in all cases, that the spacing should be small enough to offer a sufficient resistance to the passage of air around the diaphragm to avoid an undesirable loss in efficiency of the transducer.
A third embodiment of the low frequency electxo-acoustic transducer 210 of the present invention is illustrated in Figures 13 through 17.
- With reference to Figure 13, the electro-acoustic trans-ducer 210 comprised, basically, a driver section 211 above which is mounted a cylindrical acoustic transducer or air motion trans-former section 212, the two sections being enclosed in a cylin-drical housing member 214.
With reference to Figure 14, cylindrical housing member 214 comprises a plurality of radially disposed, semi-cylindrical slots 215 facing in opposite directions and alternately disposed at equal intervals along housing 214, with the exception of that portion of housing 214 occupied by driver section 211.
~river section 211 comprises a permanent magnet assembly 217 having an air gap 218 in which is disposed driver coil 219.
Acoustic transducer or air motion transformer section 212 comprises, basically, a plurality of movable diaphragms 223 (one of diaphragms 223a - 230e) connected through drive rods 221 to drive coil 219 with a like plurality of fiXed diaphragms 230(one of diaphragms 230a - 230e) disposed alternately between movab1e diaphragms 223 and attached to housing 214. In particular, fixed diaphragm 230 are attached to housing 214 at the connector portion 231 between each slot 215 to define a cavity or space 240 open at slot 215 and bounded by fixed diaphragm 230, connector portion 231 rm/l~
. ~
and movable diaphragm 223.
Movable diaphragm 223 is shown in greater detail in Figure 15 and comprises a plurality, six in the embodiment illus-trated, of alternately upward and downward protruding rigidized nodes 281 and 282, respectively, arranged in a circular array so that drive rods 221 are attached thereto at ape~ 283 or nadir 284 of each node 281 and 282, respectively.
Typically, nodes 281 and 282 can define 90 degree cones, i.e., the angle at the apex of the cone is a right angle.
It has been found that satisfactory rigidity is achieved if nodes 281 and 282 define conical sections with the transition from upward to downward projecting nodes (cones) arranged so that a straight and level line can be drawn between cones, as for example, along cut lines 17-17 of Figure 15, as also can be seen from Figure 17.
Even with drive rods 221 attached to the apex 283 and nadir 284 of each node 281 and 282, respectively, certain un-desirable resonances and harmonic distortions may be developed within the geometry of movable diaphragm 223 and within conical nodes 281 and 282 similar to the resonances described above for large cone drive speakers of the prior art.
In the present invention, because the conical nodes 281 and 282 are small, the resonance or distortion is small, however, even these harmonic distortions can be eliminated by the use of slots 235 disposed along the straight line section between conical nodes 281 and 282, as can be seen in Figure 15. Each slot 235 is filled with viscous material such as to prevent any vibrational distortion from travelling between conical nodes 281 and 282.
Typically, movable diaphragms 223 are fabricated from a rm/~C~
1067Z~l generally stiff plastic mate~ial such as polystyr~ne or the like.
For a three inch diameter diaphragm, the weight of the diaphragm will be, typically, about 1 gram.
With reference to Figure 16, there is illustrated a sec-tion through both upward and downward projecting nodes 281 and 282, respectively, showing their conical shape and the shape of the transition section between conical sections.
With reference to Figure 17, there is illustrated a sec-tion through movable diaphragm 223 taken at line 17-17 of Figure 15.
The section is taken through slots 235 and illustrates the geometry of movable diaphragm 223 where a straight and level line can be drawn across diaphragm 223 between conical sections.
As can be seen from Figure 14, the diameter of driYe coil 219 is arranged to be coincident with the diameter of the circle defined by the apexes of nodes 281 and 282 so that coil 219 can be attached directly to nodes 282 and the underside of diaphragm 223e including the underside of node 281 and also be coincident at each apex 283 and 284 with the point of attachment of drive or push rods 221.
Operation of electro-acoustic transducer 210 illustrated in Figures 13-17 is basically one of applying an alternating direc-tion force to diaphragms 223a-223e by means of the application of an alternating current to drive coil 219, which causes diaphragms 223a-223e to move alternately toward and away from fixed diaphragms 230a-230e to drive air in and out of cavity or space 240 between each fixed diaphragm 230a-230e and movable diaphragm 223a-223e, respectively.
For example, when mo~able diaphragm 223b is moved upward toward fixed diaphragm 230b, there is a compression of the air mass between diaphragm 223b and 230b causing air to flow out of rm/~
cavity 240c, a~ indicated by arrow 241, while, at the same time, there is a rarefaction of the air mass between diaphragm 223a and 230b, below diaphragm 223a causing a flow of air into cavity 240b, as indicated by arrow 242.
Thus~ a large amount of air is moved with a relatively small amount of kinetic energy.
For the purpose of simplifying the method of manufactur-ing the air motion transformer section 212 of Figures 13 and 14, this section can comprise a pluralit~ of modular fixed diaphragm units 310, as shown in Figure 18, which are adapted to stack as shown in Figure 19. Between each stacked unit 310 is disposed a movable diaphragm 223, the same as shown in Figures 16 and 17.
With reference to Figure 18~ fixed diaphragm unit 310 comprises a generally planar fixed plate portion 312, having deformed therein six equi-angularly spaced alternately upward protruding nodes or cones 314a-c and downwardly protruding nodes or cones 315a-c.
Nodes or cones 314 and 315 are arranged in the same relative location as nodes or cones 281 and 282, respectively, of movable diaphragm 223 so that, when diaphragm 223 is in position, upward protruding nodes or cones 314 of fixed diaphragm 310 and upward protruding nodes or cones 281 of movable diaphragm 223 will tend to nest, that is, be spaced apart but still fit or mate with each other. In a like manner downward protruding nodes or cones 282 of movable diaphragm 223 and downward protruding nodes or cones 315 of the next fixed diaphragm 310 below, will tend to nest.
At the apex of both cones 3I4 and 315 is a hole 316 and 317, respectively, defined by short cylindrical sections 318 1067Z0~
and 319, respectively.
A semi-cylindrical acoustic barrier 320 is disposed on the top surface of planar portion 312 terminating at each end by an upper end spacer 321 whose end surface is coincident with the diameter of circular planar portion 312.
Two intermediate spacer members 322a and 322b are disposed at equal interyals about acoustic barrier 320.
Disposed on the lower or underside of planar portion 312 is an identical configuration as that described above for the upper side, only positioned diametrically opposite the upper configuration.
For example, acoustic barrier 320', end spacer member 321' and inte.mediate spacer 322a' and 323b' (not shown) perform the same function as their counterpart above.
It will be noted that the height of end spacer 321 and intermediate spacers 322a and 322b are greater than the height of acoustic barrier 321 above planar portion 312. This greater height, that is, the difference in height between spacers 321, 322a and 322b and barrier 320, determine the width of the opening of slot 215, (Figure 13) for air motion transformer section 212 (Figures 13 and 14).
It will also be noted from Figure 19, that the top lip 323 of acoustic barrier 320 extends above corresponding lip 323' of acoustic barrier 320' of the next fixed diaphragm unit 310 above. This difference or "overlap" determines the maximum distance the movable diaphragm 223 will move within the assembled fixed diaphragm units 310.
It should also be noted that the outside diameter of movable diaphragm 223 is slightly less than the inside diameter of Xm/~
~067Z01 assembled acoustic barrier 320 and 320' such that diaphragm 223 moves up and down in the manner of a piston without touching or being connected to the walls of acoustic barrier 320 and 320'.
To assemble an air transformer section as shown in Figure 19, fixed diaphragm units 310 and moYable diaphragm 223 are alternately stacked as follows:
Movable diaphrasm drive rods 324 which are attached at one end to drive coil 219 (not shown in Figure 19~ are arranged to pass through holes 316 in cone sections 314 of fixed diaphragm unit 310 and be freely movable therein and extend upward for length corresponding to the number of movable diaphragms 223 being used for an air transformation section 212.
The bottom fixed diaphragm unit 310 is attached by means common in the art to the magnet assembly 217 (Figure 14) by means well known in the art.
Next movable diaphragm 223 is placed so that the drive rods 324 will pass through the apex 283 of nodes 281 and the apex 284 of nodes 282.
Moyable diaphragm 223 is adjusted along drive rods 324 until it is properly spaced from fixed diaphragm 310 at which point it is attached to drive rods 324 by means well known in the art such as an adhesive or glue.
A second fixed diaphragm unit 310 is then placed so that drive rods 324 will pass freely through holes 316 of cones 314 in fixed diaphragm unit 310 while drive rods 324 pass through holes '317. Diaphragm unit 310 is then adjusted along the rods until the top of end spacer 321 and intermediate spacers 322a and 322b of the lower diaphragm unit 310 come in contact with the underside of planar portion 312 of the upper diaphragm unit rm/~
310 and until the bottom of end spacers 321' and intermediate #pacers 322a' and 322b' come in contact with the top surface of planar portion 312 of the lower diaphragm unit 31~.
An adhesive or glue is applied to the surfaces of spacers 321 and 321' and intermediate spacers 322a, 322b, 322a' and 322b' where they contact the next modular section 310 to achieve a unified and ri~id structure.
Thus, it can be seen from Figure 19, a slot 327 is defined between lips 323 and the underside of planar portion 312.
Correspondingly, slot 327' is defined between lips 323' and the upper side of planar portion 312 of the next lowe~ diaphragm unit 310.
Therefore, an upward movement of drive rods 324 will result in air being forced out of slot 327 to the left, as indica-ted by arrows 329, while, at the same time, air is drawn or pulled into slot 327' from the right, as indicated by arrows 330.
Thus, air motion transformation is achieved whereby a small movement of diaphragm of 223 causes a large moyement of air in and out of slots 327 and 327'.
rm ~ ~< ~
` 1067Z01 l'HE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINE~D A~; FOLLOWS:
1. A low frequency electro-acoustic transducer com-prising a plurality of spaced apart, generally parallel ar-ranged, alternately disposed fixed and movable diaphragms defining a plurality of narrow air spaces having open sides facing in opposite directions, each of said fixed diaphragms comprising!
a first acoustic barrier disposed generally parallel and spaced apart from said movable diaphragm, a second barrier attached to said first acoustic barrier and extending approximately one-half the periphery of said first acoustic barrier and depending upwardly therefrom, a third acoustic barrier attached to said first acous-tic barrier and depending downwardly therefrom oppositely disposed from said second barrier, means for stacking and connecting like fixed diaphragms tc each other to define a stack of fixed diaphragms, said stack defining said plurality of narrow air spaces having open sides facing in opposite directions, each of said movable diaphragms comprising, a sheet member having disposed thereon a plurality of upwardly and downwardly protruding cones arranged in ordered array, each cone having an apex and a base, disposed with said bases adjacent one another, and means connected at the apex of at least three of said cones for moving said movable diaphragm alternately toward and ~way from said fixed diaphragm.
i~'f~' 21 ~
, -.;i~ ....
Claims
FIG. 1 FIG. 2A FIG. 4
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US52666774A | 1974-11-25 | 1974-11-25 |
Publications (1)
Publication Number | Publication Date |
---|---|
CA1067201A true CA1067201A (en) | 1979-11-27 |
Family
ID=24098275
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA240,018A Expired CA1067201A (en) | 1974-11-25 | 1975-11-19 | Low frequency electro-acoustic transducer |
Country Status (10)
Country | Link |
---|---|
JP (1) | JPS5175430A (en) |
AU (1) | AU499523B2 (en) |
CA (1) | CA1067201A (en) |
CH (1) | CH607524A5 (en) |
DE (1) | DE2553070A1 (en) |
DK (1) | DK529475A (en) |
FR (1) | FR2292393A1 (en) |
GB (1) | GB1522710A (en) |
IT (1) | IT1052385B (en) |
SE (1) | SE406409B (en) |
Families Citing this family (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3929266C1 (en) * | 1989-09-02 | 1991-01-03 | Mercedes-Benz Aktiengesellschaft, 7000 Stuttgart, De | |
SE503180C2 (en) * | 1994-08-29 | 1996-04-15 | Centara Patent Ab | Electroacoustic converter |
DE19605130A1 (en) * | 1996-02-13 | 1997-08-14 | Kurt Schubert | Omnidirectional electroacoustic radiator |
WO2007075674A2 (en) * | 2005-12-21 | 2007-07-05 | Tymphany Corporation | Linear array transducer and methods of manufacture |
JP2008042618A (en) * | 2006-08-08 | 2008-02-21 | Sharp Corp | Speaker system |
JP2008042614A (en) * | 2006-08-08 | 2008-02-21 | Sharp Corp | Speaker system |
JP2008042615A (en) * | 2006-08-08 | 2008-02-21 | Sharp Corp | Speaker system |
DE102007040062A1 (en) * | 2007-08-24 | 2009-02-26 | Heinen, Annegret | Broadband Exciter |
DE102014218427B4 (en) * | 2014-09-15 | 2016-06-02 | Kendrion Kuhnke Automotive GmbH | Loudspeaker, in particular electrodynamic loudspeaker |
-
1975
- 1975-11-19 CA CA240,018A patent/CA1067201A/en not_active Expired
- 1975-11-19 GB GB47691/75A patent/GB1522710A/en not_active Expired
- 1975-11-21 AU AU86834/75A patent/AU499523B2/en not_active Expired
- 1975-11-24 FR FR7535762A patent/FR2292393A1/en not_active Withdrawn
- 1975-11-24 IT IT52370/75A patent/IT1052385B/en active
- 1975-11-24 DK DK529475A patent/DK529475A/en not_active Application Discontinuation
- 1975-11-24 SE SE7513196A patent/SE406409B/en unknown
- 1975-11-24 CH CH1521875A patent/CH607524A5/xx not_active IP Right Cessation
- 1975-11-25 JP JP50140322A patent/JPS5175430A/en active Pending
- 1975-11-26 DE DE19752553070 patent/DE2553070A1/en not_active Withdrawn
Also Published As
Publication number | Publication date |
---|---|
GB1522710A (en) | 1978-08-23 |
AU499523B2 (en) | 1979-04-26 |
FR2292393A1 (en) | 1976-06-18 |
DE2553070A1 (en) | 1976-05-26 |
SE406409B (en) | 1979-02-05 |
SE7513196L (en) | 1976-05-26 |
JPS5175430A (en) | 1976-06-30 |
AU8683475A (en) | 1977-05-26 |
DK529475A (en) | 1976-05-26 |
CH607524A5 (en) | 1978-12-29 |
IT1052385B (en) | 1981-06-20 |
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