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Publication numberUS3651283 A
Publication typeGrant
Publication dateMar 21, 1972
Filing dateDec 18, 1968
Priority dateDec 18, 1968
Also published asDE1961018A1, DE1961018B2
Publication numberUS 3651283 A, US 3651283A, US-A-3651283, US3651283 A, US3651283A
InventorsDoschek Antony Z
Original AssigneeAudio Arts Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Loudspeaker having elongated rectangular moving coil
US 3651283 A
Abstract
An acoustic transducer of planar shape. Specifically, the electromagnetic driving means for the acoustic transducer may have (i) magnetized means having thin-wall portions for forming pairs of spaced apart elongated gaps containing fixed magnetic fields, preferably by positioning second magnetized elongated substantially U-shaped member about first magnetized elongated substantially U-shaped member, and (ii) driver means consisting of a non-magnetizable conductor forming means for positioning electric conductor means in said gaps. The non-magnetizable, preferably rigid diaphragm for the acoustic transducer is operably attached to the electromagnetic driving means and may be supported by flexible means. The diaphragm may be a self-supporting tubular diaphragm, having a driver part and flexible support parts, which houses the electromagnetic driving means.
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Description  (OCR text may contain errors)

United States Patent Doschek [451 Mar. 21, 1972 [54] LOUDSPEAKER HAVING ELONGATED RECTANGULAR MOVING COIL [72] Inventor: Antony Z. Doschek, Crafton, Pa.

[73] Assignee: Audio Arts Incorporated, Pittsburgh, Pa.

[22] Filed: Dec. 18, I968 [21] App]. No.: 784,669

[52] U.S.C1. ..179/115.5 R, l79/119R [51] Int. Cl .t ..H04r 9/06 [58] Field of Search ..179/l15.5,1l7, 119,180,181, 179/116;181/32, 31

[56] References Cited UNITED STATES PATENTS 3,073,916 1/1963 Williams et a1. ..179/115.5 3,095,942 7/1963 Thibodeau 181/32 3,268,672 8/1966 Roesel et al. 179/1 15.5 3,453,400 7/1969 Coen ..179/119 FOREIGN PATENTS 0R APPLICATIONS 1,126,904 12/1956 France ..179/l 15.5

Primary Examiner-Kathleen H. Claffy Assistant Examiner-Thomas L. Kundert Attorney-Arland T. Stein, Thomas C. Wettach and Robert D.

Yeager [57] ABSTRACT An acoustic transducer of planar shape. Specifically, the electromagnetic driving means for the acoustic transducer may have (i) magnetized means having thin-wall portions for forming pairs of spaced apart elongated gaps containing fixed magnetic fields, preferably by positioning second magnetized elongated substantially U-shaped member about first magnetized elongated substantially U-shaped member, and (ii) driver means consisting of a non-magnetizable conductor forming means for positioning electric conductor means in said gaps. The non-magnetizable, preferably rigid diaphragm for the acoustic transducer is operably attached to the electromagnetic driving means and may be supported by flexible means. The diaphragm may be a self-supporting tubular diaphragm,

' having a driver part and flexible support parts, which houses the electromagnetic driving means.

53 Claims, 10 Drawing Figures 7 L all PATENTEDMARZI r972 I 3,651,283

SHEET 2 BF 4 7 mvimon A/V TON Y Z. DOSCHEK Attorneys PAIENTEBMAR21 1972 SHEET 3 [IF 4 INVEN'IOR ANTONY Z. D0$CHEK Attorneys PAIENTEBMARm I972 SHEET 0F 4 mvewron ANTONY Z. DOSCHE'K Alforncys LOUDSPEAKER HAVING ELONGATED RECTANGULAR MOVING COIL This invention relates to an acoustic transducer of a planar shape. It is particularly useful in providing an inexpensive means of recreating and dispersing acoustic waves with little distortion of frequency over the range of acoustic frequencies.

It is a physical fact that an electric current moving through a conductor means in a magnetic field normal to the direction of the lines of magnetic flux produces a force normal to the directions of the electric current and the magnetic flux lines (in accordance with the well-known right-hand rule). The electromagnetic acoustic transducer applies this principle to convert variations in electric current into corresponding variations in mechanical force and in turn physical displacement variations of a diaphragm, to produce acoustic waves with corresponding variations in frequency and intensity.

(l. The intensity of an acoustic wave is the time average rate at which energy is transported by the acoustic wave per unit area across a surface usually perpendicular, but possibly oblique, to the direction of propagation.)

Acoustic transducers of a planar shape are broadly old and well known. They have been used in multiples to provide a planar loudspeaker which could be hung on a wall or the like. Such acoustic transducers have heretofore had inherent advantages over the standard conical loudspeaker: (i) they essentially eliminated back-wave cancellation effects because of the closed volume behind the diaphragm; and (ii) they eliminated perceptible Doppler effect distortion of middle and high frequencies because of the small displacement amplitude of the diaphragm. But such transducers produced acoustic waves of low intensity, and therefore, required an efficient electromagnetic driving means to drive an efficient diaphragm of large area to thereby produce sufficient acoustic power in a listening room. Such transducers were however very expensive to build and sensitive to operate.

In addition, loudspeakers generally and planar acoustic transducers particularly have been limited in the quality (2. The quality of sound reproduction is determined by the accuracy with which the frequencies of sound and their respective intensities can be recreated.) of acoustic waves and the range of audible frequencies which they could recreate. Loudspeaker development has been aimed at achieving, as far as possible, instantaneous and uniform response of the diaphragm when driven by a force at any acoustic frequency. But in the common conical loudspeadker, the diaphragm was a flexible thin cone which was restrained at its edges; and in the planar acoustic transducer, the diaphragm usually was a flexible thin plane membrane rigidly restrained at its edges. Such diaphragms (i) could not be displaced uniformly over their area and would produce spurious acoustic waves (i.e., acoustic waves unassnciated with the sound being recreated), and (ii) could not respond with substantially the same intensity at all acoustic frequencies. Further, such diaphragms had to be substantially uniform, thin and flexible, and therefore produced spurious acoustic waves of various intensities at different frequencies corresponding to the natural resonant modes of the structure. These difficulties were particularly pronounced in the common conical loudspeaker because the displacement amplitude was necessarily large (e.g., one thirty-second to as much as one-half inch) and the area ofthe diaphragm was relatively small.

The present invention overcomes these disadvantages and difficulties and makes the use of a relatively inexpensive acoustic transducer of a planar shape commercially feasible, even with sound reproducing apparatus of high fidelity.

I provide an acoustic transducer of planar shape having at least one electromagnetic driving means and at least one diaphragm operably attached thereto. Each electromagnetic driving means is comprised of (i) magnetized means having thin wall portions for forming at least one pair of spaced apart elongated gaps containing fixed magnetic fields, and (ii) driver means consisting of at least one non-magnetizable conductor forming means having portions thereof positioned in said gaps to support electric conductor means in said gaps. Each diaphragm is operably attached to at least one conductor forming means.

Magnetic flux lines are concentrated in said gaps of each said pairs of gaps to form regions of high magnetic flux density which approach substantially constant magnetic flux density. The conductor forming means, conductor means, and diaphragm (sometimes called the mobile assembly) are preferably of small mass, especially when response to a high frequency signal is desired. And the conductor means are moved within said regions of substantially constant magnetic flux density in said gaps. in this way, electric current conducted through said conductor means causes highly responsive and substantially uniform linear forces to be exerted on the driver means positioned in said gaps at any given frequency.

Precautions are taken to have the forces exerted on the driver means in each said gap in the same direction: (i) if the magnetic flux lines in said gaps of a said pair of gaps are in the same direction, the electric current moving through said conductor means in said gaps must be in the same direction; and (ii) if the magnetic flux lines in said gaps of a said pair of gaps are in the opposite direction, the electric current moving through said conductor means in said gaps must be in the opposite direction. Further, the magnetic fields in said gaps should be of substantially like configuration so that the forces exerted on the driver means extending in said gaps are substantially equal, thereby preventing the driver means from yawing; if said magnetic fields in said gaps are not of substantially like configuration, the amount of electric current conducted through the conductor means should be regulated or the support means for the diaphragm must be adjusted so that the diaphragm does not yaw and thereby produce distorted acoustic waves.

I prefer that said magnetic fields in said gaps be of substantially like configuration and have magnetic flux lines in opposite directions. By this arrangement, each electromagnetic driving means provides a highly sensitive and efficient displacement of the diaphragm without causing distorted acoustic waves.

The thickness of the thin-walled portions of the magnetized means should be kept within narrow limits for each material, each particular shape and magnetizing means. These limits can be determined by simple measurement: When the thickness is too large, edge effects become significant and substantial magnetic flux can be measured outside said gaps (i.e., the configurations of the magnetic fields tend to resemble those associated with horseshoe" magnets); and when the thickness is too small, a leakage of magnetic flux can be measured along the base of the magnetized means. For example, I

have measured the limits of the thin-wall portions of a magnetized means of my preferred U-shape (hereinafter described) made of Armco ingot and magnetized with a ceramic sinistered ferrite permanent magnet of 800 total gauss (positioned as hereinafter described) to be about 0.030 to 0.035 inch.

In addition, said gaps containing the magnetic fields should be adjusted within narrow limits. Said gaps should be as narrow as possible to produce magnetic flux of highest density and to approach a substantially constant magnetic flux density in said gaps. Yet, said gaps should be sufficiently broad so that a slight warp of the conductor forming means or the thin-wall portions of the magnetized means does not cause the driver means to bind in said gaps. l have found with my preferred U- shaped magnetized means (hereinbefore mentioned and hereinafter described) made of Armco ingot that the gap should be about 0.010 inch; for optimizing high frequency response I prefer a narrower gap width; e.g., between 0.010 and 0.001 inch.

I prefer, in addition, that said gaps be substantially filled with resilient non-magnetizable material, such as highly compliant rubber or plastic foam, to preserve accurate alignment of the parts, to improve the ruggedness of the electromagnetic driving means during mounting, and to improve the high frequency response of the acoustic transducer. Such resilient non-magnetizable material should be heat conductive to dissipate the small amount of heat which is generated from the passage of electric current through the conductor means. By this arrangement, electromagnetic driving means, as an assembly, could be disposed geometrically or preferably randomly over any mounting surface, and covered with a single sheet or sheet sections of suitable material to form a diaphragm and in turn an acoustic transducer.

The magnetized means having thin-wall portions may be comprised of at least one first magnetized elongated substantially U-shaped member and at least one second magnetized elongated substantially U-shaped member, wherein each said U-shaped member has a base part and flange parts. Each said second U-shaped member is positioned about a said first U- shaped member to form at least a pair of said spaced apart elongated gaps between flange portions thereof, wherein fixed magnetic fields are formed.

I also prefer that said U-shaped members be magnetized and fixed magnetic fields having magnetic flux lines in opposite direction be formed in said gaps by positioning permanently I magnetized material between base portions of said U-shaped members with oppositely polarized faces of said permanently magnetized material in contact with said base portions of said U-shaped members. I prefer in addition that the permanently magnetized material to symmetric in shape and be symmetri cally positioned between said base parts of said U-shaped members so that the fixed magnetic fields formed in said gaps are substantially like in configuration. By this arrangement, magnetized means of high efficiency and sensitivity can be produced and operated relatively inexpensively.

I also prefer that each conductor forming means he a substantially U-shaped member and have flange portions thereof positioned in said gaps to reduce the expense of fabrication and increase the ruggedness of the acoustic transducer.

A non-magnetizable diaphragm is fastened to said conductor forming means so that the electromagnetic driving means displaces the diaphragm when current passes through the conductor means. The diaphragm should be relatively thin and of small mass so that it is very sensitive to displacement by the electromagnetic driving means. The surface portions of the diaphragm may be of any suitable shape and may even conform to the decor of the listening room or sound reproduction system in which the acoustic transducer is used; but where the diaphragm is rigidly supported, the diaphragm should have substantially plane surface portions to avoid distortion of the acoustic waves recreated.

The diaphragm may be supported by any suitable means, either rigid or flexible. If rigid support means are used, the diaphragm is flexible. If flexible support means are used, the diaphragm can be rigid and the flexible support means should have an elastic compliance for returning the diaphragm to its original position when it is displaced by the electromagnetic driving means. Preferably the diaphragm is supported by flexible support means and in addition is substantially rigid so that all parts of it can be displaced substantially uniformly by the electromagnetic driving means. By this arrangement, the quality of sound reproduction is bettered (i) by avoiding the production of spurious acoustic waves associated with nonuniform displacement of the diaphragm (ii) by inhibiting inherent flexural modes of vibration; and (iii) by recreating acoustic waves of substantially the same intensity over the entire area of the diaphragm. In addition, the range of audible frequencies is extended at both the high end and the low end by increasing the acoustic power of the acoustic waves being recreated at such frequencies to the point where they can be heard by a listener.

I also prefer that the diaphragm have a substantially nonuniform cross section and thereby avoid the production of spurious acoustic waves associated with the inherent resonant modes of symmetric structure, Indeed, I prefer that the thickness of the diaphragm he graduated in cross section, or that the diaphragm be randomly perforated with relatively large holes which are covered with a taut film of very thin material to improve the high frequency response of the diaphragm as well as to avoid the production of spurious acoustic waves.

The diaphragm for an acoustic transducer may be a selfsupporting tubular diaphragm for housing an electromagnetic driving means. Said self-supporting tubular diaphragm has a driver part and flexible support parts for supporting said driver part, preferably at its edge portions. And said self-supporting tubular diaphragm is operably attached to the driver means of the electromagnetic driver means so that said driver part and said support parts of said diaphragm displace at the same frequency. I prefer that said support parts have inwardly extending portions which will displace outwardly in phase with the driver part, and thereby increasing the efficiency of the diaphragm by aiding in recreating acoustic waves. Said support parts may have portions outwardly extending or partly flat; but the more inwardly extending portions and the greater their outward displacement amplitude, the greater the efficiency of the sound reproduction. For greatest efficiency of reproduction, I prefer that each said support part consist of one single inward fold or an inwardly extending semi-circle; but for better quality of reproduction, I prefer that the inwardly extending portion or portions of each said support part have an outward displacement amplitude such that the average intensity of the acoustic waves produced thereby is substantially equal to the average intensity of the acoustic waves produced bythe driver part'.

In addition, said tubular shape of the self-supporting diaphragm may be formed with a separate base surface by installation or with an integral base part capable of supporting the electromagnetic driving means and said flexible support parts, so that said tubular diaphragm encloses the electromagnetic driving means. This latter embodiment permits simplicity in fabrication and mounting, and in addition, permits said diaphragm to be mounted so that it can direct acoustic waves in four directions at one time. In any case, the support parts and the driver part may be linear, curvilinear, undulating and/or fluted for decorative or utilitarian purposes.

Such a self-supporting diaphragm will respond substantially uniformly to recreate any acoustic frequency without introducing substantial spurious acoustic waves. I contemplate that the only spurious acoustic waves produced will be by the natural resonant modes of the structure which can be attenuated to negligible audibility by proper design. Further, for simplicity and inexpensive applications, I prefer that the driver part and all other parts of the diaphragm have substantially plane surface portions.

I contemplate that the displacement amplitude of the diaphragm (or the driver part thereof) is very small (e.g., 0.0005 to 0.2500 inch) so that the frequency and intensity distortion will be small. In application, my acoustic transducer may be assembled in multiples so that a very large area of diaphragm exposed to the ambient air of a listening room may be driven uniformly by the electromagnetic driving means. In this way, the acoustic transducer need not be mounted in a resonance chamber (as a conical loudspeaker often does) to produce high acoustic power in the listening room, even though the average intensity of the acoustic waves recreated by a given area of the acoustic transducer is low. Furthermore, such large areas of diaphragm have a dampening effect due to internal stressing to eliminate certain spurious acoustic waves associated with the natural resonant modes of the structure.

I have found that my acoustic .transducer is particularly adapted for mounting at an intersection of at least two planar surfaces, e.g., a wall and ceiling, or a wall and another wall. It can be so mounted without additional mounting supports; and moreover, a coupling effect is created which increases the efficiency of the acoustic transducer. For optimum acoustic power and uniform sound distribution the precise location of the acoustic transducers within a listening room, as well as the surface area of the diaphragm, can be calculated by determining the geometry and volume of the room, the absorption constant of the room, and the average intensity range of the sound from the acoustic transducer.

Other details, objects and advantages of my invention will become apparent as the following description of the presently preferred embodiments thereof proceeds.

In the accompanying drawings I illustrate presently preferred embodiments of my invention in which:

FIG. 1 is an acoustic transducer with an electromagnetic driving means and a diaphragm;

FIG. 2 is an acoustic transducer with a diaphragm rigidly supported;

FIG. 3 is an acoustic transducer with a diaphragm flexibly supported;

FIG. 4 is a self-supporting diaphragm for an acoustic transducer;

FIG. 5 is an acoustic transducer with an electromagnetic driving means and a self-supporting diaphragm;

FIG. 6 is an acoustic transducer with an electromagnetic driving means, a self-supporting diaphragm and compliance elements;

FIG. 7 is a broken-away enlarged portion of the acoustic transducer shown in FIG. 5 showing the configuration of a magnetic field;

FIG. 8 is an acoustic transducer with an electromagnetic driving means and an alternative self-supporting diaphragm;

FIG. 9 is an acoustic transducer with an electromagnetic driving means and an alternative self-supporting diaphragm with transverse arresting means; and

FIG. 10 is a response curve comparing the operation of an acoustic transducer herein described with an excellent conical loudspeaker.

Referring specifically to the drawings, an acoustic transducer of planar shape has an electromagnetic driving means 2 and a diaphragm 3. The electromagnetic driving means 2 is comprised of a magnetized means 4 and a driver means 5. The magnetized means 4 is comprised of a first elongated substantially U-shaped member 6 and a second elongated substantially U-shaped member 7, wherein each said U-shaped member has a base part 8 and flange parts 9. Said U shaped members 6 and 7 should be of a low reluctance, magnetically permeable material such as a highly magnetically permeable iron or nickel-iron alloy.

Said second U-shaped member 7 is concentrically positioned about said first U-shaped member 6 to form a spaced apart pair of elongated gaps 10 between flange portions thereof to form fixed magnetic fields in said gaps. A symmetric block of permanently magnetized material 12 is symmetrically positioned between the base parts 8 of said first U-shaped member 6 and said second U-shaped member 7 with its oppositely polarized faces in contact with said base parts 8 of said first and second U-shaped members 7 and 8. Said magnetic material may be, for example, a ferromagnetic iron, nickel, or cobalt sinistered ferrite, or an alloy thereof. By this arrangement, said first and second U-shaped members 6 and 7 are magnetized, and in turn fixed magnetic fields ll of high density of substantially like configurations and having mag netic flux lines in opposite directions are formed in said gaps 10.

Said driver means 5 is comprised of a substantially U- shaped conductor forming means 13 having flange portions 14 positioned in said gaps 10, and electric conductor means 15 supported in said gaps 10 by said flange portions 14 of conductor forming means 13. Said conductor forming means 13 can be made of any non-magnetizable material which is light in weight. Said electric conductor means 15 consists of a coil of low resistance wire, such as copper, aluminum or silver, wound around the conductor forming means 13 to form a voice coil. In this way, the conductor means are positioned in a region of highly dense magnetic flux (as shown in FIG. 7) so that variations in electric current produce a highly responsive and sensitive mechanical force, and the heat produced by the electric current passing through said conductor means can be readily dissipated into the gaps.

The diaphragm 3 is attached to the conductor forming means 13 by suitable means so that it can be moved by the driver means 5 when the electric current passing through electric conductor means 15 is varied. The diaphragm 3 may be supported by either rigid support means 16 as shown in FIG. 2 or by flexible support means 17 as shown in FIG. 3. If supported by rigid support means, the diaphragm 3 must be flexible. I prefer, however, that the diaphragm 3 be supported by flexible support means 17 so that the diaphragm 3 can be substantially rigid and moved uniformly by the driver means 5.

As shown in FIG. 3, the flexible support means 17 consists of substantially filling the gaps 10 between the flange parts 9 of said first U-shaped member 6 and said second U-shaped member 7 with a resilient material, such as rubber or plastic foam, so that the parts of electromagnetic driving means 2 remain aligned during mounting of the acoustic transducer. In addition, such flexible support means 17 inhibits transverse displacement of the electromagnetic driving means 2 during operation of the acoustic transducer. By this embodiment, electromagnetic driving means 2 could be disposed geometrically or preferably randomly over a mounting surface and covered with a single sheet or sheet sections of suitable material to form a rigid diaphragm 3 and in turn an acoustic transducer.

I prefer that sections of my acoustic transducer or the diaphragm thereof be joined at joints or corners with flexible cylindrical elements. Such flexible cylindrical elements should be cemented along the joints and in the corners between the diaphragm and the mounting surface. Such flexible cylindrical elements aid in restoring the diaphragm to the neutral position upon displacement, and inhibit transverse displacement of the diaphragm 3.

A diaphragm 18 for an acoustic transducer (shown in FIG. 4) may consist of a self-supporting tubular diaphragm 18 capable of housing any suitable electromagnetic driving means. Said tubular diaphragm 18 has (i) a driver part 20 that is capable of being moved by an electromagnetic driving means, wherein said driver part 20 is preferably substantially rigid and is preferably nonuniform in thickness, and (ii) flexible support parts 21 having inwardly extending portions that are capable of supporting said driver part 20 at its edge portions 22. In addition,.the fold 23 has a displacement amplitude substantially equal to about one and one-third times the displacement amplitude of the driver part 20 so that average intensity of the acoustic waves produced by the support parts 21 is substantially the same as the driver part 20. Said tubular diaphragm 18 also has a base part 24 capable of supporting an electromagnetic driving means and said support parts 21, so that said tubular diaphragm 18 encloses suitable electromagnetic driving means. Said diaphragm 18 should be made of any non-magnetizable foldable material such as paper, plastic, metal foil, plasticized paper, metallized paper or stiffened cambric cloth.

As shown in FIG. 5, I prefer that the electromagnetic driving means 2 (shown in FIGS. 2 and 3) be used in combination with the self-supporting diaphragm 18 (shown in FIG. 4) to form an efficient acoustic transducer for reproducing acoustic waves of good quality over the entire range of acoustic frequencies. As a further refinement (shown in FIG. 6) compliance elements 25 may be positioned between the support parts 21" and the flange parts 9" of said second U-shaped member 7" to aid in restoring the self-supporting diaphragm 18" to the neutral position.

In an alternative embodiment (shown in FIG. 8) an acoustic transducer is the same save for its composition and the configuration of the self supporting tubular diaphragm 18'. Each support parts 21' is an inwardly extending substantially semicircular part. In this embodiment, I prefer that the driver part 20 be made of polycarbonate, the flexible support parts 21 be made of cambric cloth, and the base part 24' be made of Masonite. In addition, said driver part 20' has holes 28 therein which are covered with a film 29 so that diaphragm 18' has substantially nonuniform thickness. I have found that this embodiment inhibits transverse displacement of the driver part 20 and thereby certain distortions in recreation of acoustic waves.

In addition (as shown in FIG. 9) flexible inward semicylindrical arresting means 26 can be cemented transverse the ends 27 of lengths of self-supporting tubular diaphragm 18'. In this way, the diaphragm 18' can be more rapidly restored to the neutral position upon displacement and the diaphragm 18' can be inhibited from displacing transversely.

To illustrate the advantages of my acoustic transducer (as shown in FIG. 9), I have compared it over the entire range of acoustic frequencies with the best conical loudspeaker I could obtain with comparative parameters. In particular, I compared the performance of an 8 inch conical loudspeaker having a whizzer, a mobile assembly weight of 10.0 grams, an Alnico magnet of 6.5 ounces, and a voice coil of 244 feet in length with my acoustic transducer with a 6 inch diaphragm and a inch electromagnetic driving means, having a mobile assembly weight of 18 grams, a ferrite magnet of 1 ounce, a voice coil of 200 feet in length, and gap widths of 0.134 inch. The performance of both were measured with a substantially constant 280 milli-watts to the voice coil and the same microphone placement. The resulting frequency response curves, adjusted by a plus l9.l dbm for my acoustic transducer to compensate for differences in the significant parameters, are shown in FIG. 10: (i) The intensity level (3. The intensity level 8 ofa sound wave is defined by the equation:

where I, is the intensity and I is an arbitrary reference intensity which is taken as l0 watt/cm corresponding roughly to the faintest sound which can be heard. Intensity levels are expressed in decibels, abbreviated db.) of the conical loudspeaker falls off greatly below 100 cycles per second while the intensity level of my acoustic transducer remains at a comparatively linear slope at these low frequencies; and (ii) the drop in the frequency response curve for my acoustic transducer is only about 6 decibels per octave compared to the practical design limit for a conical loudspeaker of 12 decibels per octave. 1 further note that the intensity level for my acoustic transducer becomes unstable at about 3,000 cycles per second due to the design cutoff of the particular acoustic transducer 1 used in this comparison. To design my acoustic transducer for high frequency response (above 3,000 cycles per second), I would reduce the mobile assembly weight to as little as 1.5 grams and reduce the gap widths to about 0.001 inch.

While I have shown and described certain presently preferred embodiments of my invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied within the scope of the following claims.

lclaim:

1. An acoustic transducer comprising: at least magnetized means having therein at least one pair of spaced apart elongated gaps containing fixed magnetic fields, each elongated gap formed by non-leaking portions of said magnetized means having no substantial edge conductance of magnetic flux; at least one nonmagnetizable conductor forming means having portions thereof positioned in said gaps; electric conductor means supported by said portions of each said conductor forming means in said gaps; and at least one non-magnetizable diaphragm operably attached to at least one said conductor forming means.

2. An acoustic transducer as claimed in claim 1 wherein: each magnetized means is capable of producing magnetic fields in each said pair of gaps having substantially like configurations and having magnetic flux lines in opposite directions.

3. An acoustic transducer as claimed in claim 1 wherein: each said diaphragm is supported by flexible means.

4. An acoustic transducer as claimed in claim 3 wherein: each said diaphragm is substantially rigid.

5. An acoustic transducer as claimed in claim 1 wherein: each said diaphragm has substantially plane surface portions.

6. An acoustic transducer as claimed in claim 1 wherein: each said diaphragm has substantially nonuniform thickness.

7. An acoustic transducer comprising: at least one magnetized means having therein at least one pair of spaced apart elongated gaps containing fixed magnetic fields, each elongated gap formed by non-leaking portions of said magnetized means having no substantial edge conductance of magnetic flux; said gaps being substantially filled with resilient non-magnetizable material; at least one nonsmagnetizable conductor forming means having portions thereof positioned in said gaps;

electric conductor means supported by said portions of each said conductor forming means in said gaps; and at least one non-magnetizable diaphragm operably attached to at least one said conductor forming means.

8. An acoustic transducer comprising: at least one magnetized means having thin-wall portions for forming at least one pair of spaced apart elongated gaps containing fixed magnetic fields; at least one non-magnetizable conductor forming means having portions thereof positioned in said gaps; electric conductor means supported by said portions of each said conductor forming means in said gaps; and at least one non-magnetizable self-supporting diaphragm for housing at least one said magnetized means and at least one said conductor forming means, having a driver part operably attached to at least one said conductor forming means and having flexible support parts for supporting said driver part, and capable of forming a tubular shape with a base surface.

9. An acoustic transducer as claimed in claim 8 wherein: each said self-supporting diaphragm has a base part for supporting at least one said magnetized means and said flexible support parts of said diaphragm and forming said tubular shape wherein said diaphragm encloses at least one said magnetized means and at least one said conductor forming means.

10. An acoustic transducer as claimed in claim 8 wherein: each said support part has inwardly extending portions.

11. An acoustic transducer as claimed in claim 10 wherein: each said support part consists of a single inward fold.

12. An acoustic transducer as claimed in claim 10 wherein: each said support part consists of an inward substantially semicircular part.

13. An acoustic transducer as claimed in claim 8 comprising in addition: flexible arresting means positioned in end portions of said self-supporting diaphragm and attached to said driver part of said self-supporting diaphragm.

14. An acoustic transducer as claimed in claim 9 comprising in addition: a mounting base consisting of an intersection of at least two planar surfaces for mounting said base part thereon.

15. An acoustic transducer comprising: at least one first magnetized elongated substantially U-shaped member; at least one second magnetized elongated substantially U-shaped member positioned about at least one said first magnetized U- shaped member for forming a pair of spaced apart elongated gaps between flange portions of said magnetized U-shaped members containing fixed magnetic fields; at least one nonmagnetizable conductor forming means having portions thereof positioned in said gaps; at least one conductor means supported by said portions of each said conductor forming means in said gaps; and at least one non-magnetizable diaphragm operably attached to each said conductor forming means.

16. An acoustic transducer as claimed in claim 15 wherein: each said conductor forming means is a substantially U- shaped member.

17. An acoustic transducer as claimed in claim 15 wherein: each said first and second U-shaped members are magnetized by positioning permanently magnetized material between base parts thereof with oppositely polarized faces in contact with said base parts, whereby said magnetized U-shaped members will produce magnetic flux lines in opposite directions in said gaps of said pair of gaps.

18. An acoustic transducer as claimed in claim 15 wherein: each magnetized means is capable of producing magnetic fields in said pair of gaps having substantially like configuration and having magnetic flux lines in opposite directions.

19. An acoustic transducer as claimed in claim 15 wherein: said diaphragm is supported by flexible means.

20. An acoustic transducer as claimed in claim 19 wherein: the diaphragm is substantially rigid.

21. An acoustic transducer as claimed in claim 15 wherein: the diaphragm has substantially plane surface portions.

22. An acoustic transducer as claimed in claim 15 wherein: the diaphragm has substantially nonuniform thickness.

23. An acoustic transducer as claimed in claim wherein: said gaps are substantially filled with resilient non-magnetizable material.

24. An acoustic transducer comprising: at least one first magnetized elongated substantially U-shaped member; at least one second magnetized elongated substantially U-shaped member positioned about at least one said first magnetized U- shaped member for forming a pair of spaced apart elongated gaps between flange portions of said magnetized U-shaped members containing fixed magnetic fields; at least one nonmagnetizable conductor forming means having portions thereof positioned in said gaps; at least one conductor means supported by said portions of each said conductor forming means in said gaps; and at least one non-magnetizable selfsupporting diaphragm for housing at least one said first and second magnetized U-shaped members and at least one said conductor forming means, having a driver part operably attached to at least one said conductor forming means and having flexible support parts for supporting said driver part, and capable of forming a tubular shape with a base surface.

25. An acoustic transducer as claimed in claim 24 wherein: each said self-supporting diaphragm has a base part for supporting at least one said second U-shaped member and said flexible support parts of said tubular diaphragm and forming said tubular shape, whereby the diaphragm encloses at least one said first and second U-shaped member and at least one said conductor forming means.

26. An acoustic transducer as claimed in claim 24 wherein: each said support part has inwardly extending portions.

27. An acoustic transducer as claimed in claim 26 wherein: each said support part consists of a single inward fold.

28. An acoustic transducer as claimed in claim 26 wherein: each said support part consists of an inward substantially semicircular part.

29. An acoustic transducer as claimed in claim 24 comprisin g in addition: flexible arresting means positioned in end positions of said self-supporting diaphragm and attached to said driver part of said self-supporting diaphragm.

30. An acoustic transducer as claimed in claim comprising in addition: a mounting base consisting of an intersection of at least two planar surfaces for mounting said base part thereon.

31. An acoustic transducer comprising: a first magnetized elongated substantially U-shaped member; a second magnetizable elongated substantially U-shaped member positioned about said first magnetizable U-shaped member for forming a pair of spaced apart elongated gaps between flange portions of said magnetizable U-shaped members; permanently magnetized material positioned between base parts of said magnetizable U-shaped members with oppositely polarized faces in contact with said base parts for magnetizing said magnetizable U-shaped members and for producing magnetic fields having magnetic flux lines in opposite directions in said gaps of said pair of gaps; a non-magnetizable conductor forming U-shaped member having flange portions thereof positioned in said gaps; a conductor means supported by said flange portions of said conductor forming U-shaped member in said gaps; and a non-magnetizable self-supporting diaphragm for housing said first and second magnetizable U- shaped members and said conductor forming U-shaped member, having a driver part operably attached to said conductor forming U-shaped member and having flexible inwardly extending support parts for supporting said driver part at end portions thereof, and capable of forming a tubular shape with a base surface.

32. An acoustic transducer as claimed in claim 31 wherein said self-supporting diaphragm has a base part for supporting at least one said second U-shaped member and said flexible support parts of said diaphragm and forming said tubular shape; and comprising in addition a mounting base consisting of an intersection of at least two planar surfaces for mounting said base part thereon.

33. An acoustic transducer comprising: a first magnetized elongated substantially U-shaped member; a second magnetized elongated substantially U-s'haped member positioned about said first magnetized U-shaped member for forming a pair of spaced apart elongated gaps between flange portions of said magnetized U-shaped members; a non-magnetizable conductor forming U-shaped member having flange portions thereof positioned in said gaps; a conductor means supported by said flange portions of said conductor forming Ushaped member in said gaps; and a non-magnetizable self-supporting diaphragm for housing said first and second magnetizable U- shaped members and said conductor forming U-shaped members, having a driver part operably attached to said conductor forming U-shaped member and having flexible inward substantially inwardly-folded support parts for supporting said driver part, and capable of forming a tubular shape with a base surface.

34. An acoustic transducer as claimed in claim 33 comprising in addition: inwardly extending flexible arresting means positioned in end positions of said self-supporting diaphragm and attached to said driver part of said selfsupporting diaphragm.

35. An acoustic transducer comprising: a first magnetizable elongated substantially U-shaped member; a second magnetizable elongated substantially U-shaped member positioned about said first magnetizable U-shaped member for forming a pair of spaced apart elongated gaps between flange portions of said magnetizable U-shaped members, permanently magnetized material positioned between base parts of said magnetizable U-shaped members with oppositely polarized faces in contact with said base parts for magnetizing said magnetizable U-shaped members and for producing magnetic fields having magnetic flux lines in opposite directions in said gaps of said pair of gaps; a non-magnetizable conductor forming U-shaped member having flange portions thereof positioned in said gaps; a conductor means supported by said flange portions of said conductor forming U-shaped member in said gaps; and a non-magnetizable self-supporting diaphragm for housing said first and second magnetizable U- shaped members and said conductor forming U-sl aped members, having a driver part operably attached to said conductor forming U-shaped member and having flexible inward substantially semicircular support parts for supporting said driver part, and capable of forming a tubular shape with a base surface.

36. An acoustic transducer as claimed in claim 35 comprising in addition: flexible inward substantially semicircular arresting means positioned in end positions of said self-supporting diaphragm and attached to said driver part of said self-supporting diaphragm.

37. An acoustic transducer as claimed in claim 35 wherein: said self-supporting diaphragm has a base part for supporting at least one said second U-shaped member and forming said tubular shape; and comprising in addition a mounting base consisting of an intersection of at least two planar surfaces for mounting said base part thereon.

38. A self-supporting diaphragm for acoustic transducers adapted to form with a base surface a tubular structure comprising: a non-magnetizable self-supporting diaphragm for housing at least one electromagnetic driving means; said diaphragm having a driver part being substantially rigid and capable of being moved by at least one electromagnetic driving means, and having flexible support parts for supporting said driver part and capable of being moved by at least one electromagnetic driving means; said driver part and said support parts capable of creating acoustic waves and capable of forming a tubular shape with a base surface.

39. A self-supporting diaphragm for an acoustic transducer as claimed in claim 38 wherein: each said support part has inwardly extending portions.

40. A self-supporting diaphragm for acoustic transducers as claimed in claim 39 wherein: each said support part consists of a single inward fold.

41. A self-supporting diaphragm for an acoustic transducer as claimed in claim 39 wherein: each said support part consists of an inward substantially semicircular part.

42. A self-supporting diaphragm for an acoustic transducer as claimed in claim 38 wherein: each said self-supporting diaphragm has a base part for supporting at least one elec' tromagnetic driving means and said flexible support parts of said and forming said tubular shape, whereby said diaphragm encloses at least one electromagnetic driving means.

43. A self-supporting diaphragm for an acoustic transducer as claimed in claim 38 wherein: the driver part has substantially plane surface portions.

44. A self-supporting diaphragm for an acoustic transducer as claimed in claim 38 wherein: the diaphragm has substantially nonuniform thickness.

45. An electromagnetic driving means for an acoustic transducer comprising: a first magnetized elongated substantially U-shaped member; a second magnetized elongated substantially U-shaped member positioned about said first magnetized elongated U-shaped member for forming a pair of spaced apart elongated gaps between flange portions of said magnetized U-shaped members containing fixed magnetic fields; at least one non-magnetizable conductor forming means having portions thereof positioned in said gaps; and at least one conductor means supported by said portions of each said conductor means in said gaps.

46. An electromagnetic driving means for an acoustic transducer as claimed in claim 45 wherein: said first and second magnetized U-shaped members are capable ofproducing magnetic fields in said gaps substantially like in configuration and having magnetic flux lines opposite in directions.

47. An electromagnetic driving means for an acoustic transducer comprising: a first magnetized elongated substantially U-shaped member; a second magnetized elongated substantially U-shaped member positioned about said first magnetized elongated U-shaped member for forming a pair of spaced apart elongated gaps between flange portions of said magnetized U-shaped members containing fixed magnetic fields; at least one non-magnetizable conductor forming substantially U-shaped member having flange portions thereof positioned in said gaps; and at least one conductor means supported by said portions of each said conductor means in said gaps.

48. An electromagnetic driving means for an acoustic transducer as claimed in claim 45 wherein: said first and second U- shaped members are magnetized by positioning permanently magnetized material between base parts thereof with oppositely polarized faces in contact with said base parts, whereby said magnetized U-shaped members will produce magnetic flux lines in opposite directions in said gaps of said pair of gaps.

49. An electromagnetic driving means for an acoustic trans ducer as claimed in claim 45 wherein: said gaps are substantially filled with resilient non-magnetizable material.

50. An electromagnetic driving means for an acoustic transducer comprising: at least magnetized means having therein at least one pair of spaced apart elongated gaps containing fixed magnetic fields, each elongated gap formed by non-leaking portions of said magnetized means having no substantial edge conductance of magnetic flux; at least one non-magnetizable conductor forming means having portions thereof positioned in said gaps; and at least one conductor means supported by said portions of each said conductor forming means in said gaps.

51. An electromagnetic driving means for an acoustic transducer as claimed in claim 50 wherein: said magnetized means is capable of producing in each said pair of gaps magnetic fields of substantially like configuration and having magnetic flux lines in opposite directions.

52. Electromagnetic driving means for an acoustic transducer as claimed in claim 50 wherein: each said conductor forming means is a substantially U-shaped member.

53. Electromagnetic driving means for an acoustic transducer com rising: magnetized means having tl' |erein at least one pair 0 spaced apart elongated gaps containing fixed magnetic fields, each elongated gap formed by non-leaking portions of said magnetized means having no substantial edge conductance of magnetic flux; said gaps being substantially filled with resilient non-magnetizable material; at least one non-magnetizable conductor forming means having portions thereof positioned in said gaps; and at least one conductor means supported by said portions of each said conductor forming means in said gaps.

' UNITED STATES PATENT @FHQE @ERTIFEQATE @F CQRREQTWN Patent No. 306510283 Dated March 5' 1 Inventor s) ANTONY Z. DOSCHEK It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

" Column 1, lines; @0-53 appearing in small type after 2 lines parenthesis, should be in regular text, ww-

60-61, "0.010 and M60]. inchm should reao 0.100 and line 64, "structure fl should? read str uctureo 9 Column 6, line 58, "parts shoals read part Column 7, lines 17-22, the material appearing iu parentheses shou lfi all be in small type; line 44, after "at least, insert one Column 11, lines 7 hind 8, after support parts", cancel "of said" r I i sighed aaa sealed this 2 as of November 1973.

0.010 inch. Cefrlmnn 3, line 17, to" should read be 1 EAL) Attest EDWARD M FLETCHER JR RENE D o TEGTMEYER Attesting Officer Acting Commissioner of Patents PO-lOSO '10-69) USCOMM'DC 60376-P69 Us. GOVERNMENT PRINTING OFFICE: I969 O366-334.

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Classifications
U.S. Classification381/419, 381/417, 381/413
International ClassificationH04R9/00, H04R9/02
Cooperative ClassificationH04R9/022
European ClassificationH04R9/02B