US3654403A - Electrostatic speaker - Google Patents

Electrostatic speaker Download PDF

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Publication number
US3654403A
US3654403A US820888A US3654403DA US3654403A US 3654403 A US3654403 A US 3654403A US 820888 A US820888 A US 820888A US 3654403D A US3654403D A US 3654403DA US 3654403 A US3654403 A US 3654403A
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membranes
membrane
backing plate
backing
plates
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Expired - Lifetime
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US820888A
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English (en)
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Lloyd J Bobb
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers
    • H04R19/02—Loudspeakers

Definitions

  • the invention is concerned with the type of electrostatic speakers in which a flexible membrane carrying a conductive coating is mounted in spaced position adjacent to a substantially rigid perforated backing plate, the signal voltage being applied to the membrane coating and to the backing plate.
  • the sound is generated by motion of the flexible membrane in relation to the perforated plate and, for fidelity of sound generation, it is desirable that the perforated backing plate be essentially rigid or damped in a manner substantially eliminating motions of the plate in response to the applied signal voltage or in consequence of the sound waves generated by the motion of the membrane.
  • One of the primary objectives of the present invention is to provide improved damping means for the perforated backing plate of a speaker of the kind above referred to.
  • This is achieved according to the present invention by the employment of a highly cellular slab of plastic or resin material, such as polyurethane foam, which is mounted to have pressure engagement with at least a major portion of the surface of the perforated plate.
  • a highly cellular slab of plastic or resin material such as polyurethane foam
  • a further general objective of the present invention is to simplify the construction of speakers of the kind above referred to, this being achieved, in part, by providing a frame structure which is used to clamp and mount a flexible membrane (or a pair of flexible membranes in the case ofa double ended speaker), the membrane or membranes being pretensioned at the time of assembly.
  • the clamping of the membranes is effected with the conductive coatings of the membranes presented toward each other and with a contact element between at least a portion of the margins of the membranes.
  • FIG. 1 is an elevational view of an electrostatic speakerincorporating the features of the present invention
  • FIG. 2 is an enlarged fragmentary sectional view taken as indicated by the section line 2-2 on FIG. 1;
  • FIG. 3 is an isometric fragmentary view illustrating on an enlarged scale on one corner of the sub-assembly of frame structure and membranes, but with the various components of the sub-assembly separated from each other, in the manner of an exploded view;
  • FIG. 4 is a view of the same type as FIG. 3, but illustrating, in the manner of an exploded view, additional parts of the speaker being brought together with the sub-assembly of the parts shown in FIG. 3.
  • the frame structure is made up of two counterpart frames 5.
  • these frames are planar and are square and open in the central area.
  • a series of parts is positioned between the two frames 5-5, including the central perforated contact strips 6, a pair of flexible membranes 7, one located at each side of the contact strips 6.
  • the membranes preferably comprise sheets of resin material such as polyester resin, one form of which is readily available under the Tradename Mylar (E.I. DuPont de Nemours and Co.).
  • the membranes are desirably quite thin, for instance of the order of about one-fourth to one-half mil.
  • the membranes are provided with metallic or conductive coatings applied, for instance, by well known vacuum evaporation techniques.
  • Aluminum is an effective metal for coating purposes and an appropriate aluminum coating will be very thin, having a resistance of the order of 3 to 5 ohms as measured across a square of the coated membrane.
  • the membranes are positioned with their conductive coatings presented toward each other and thus presented so as to engage the contact strips 6.
  • gripping strips or gaskets 8 made, for example, of blotting paper are provided. With the contact strips 6 perforated, as indicated, when the parts are clamped together, the gaskets act to press localized areas of the membranes into perforations of the contact strips in the manner indicated in FIG. 2 and thereby provide an interlocking and tight gripping engagement adapted to maintain the membranes in tension.
  • I preferably establish a condition of omni-directional tension in the membranes.
  • bolts 9 are used at two opposite sides of the frame 5 and that bolts 10 are used at the other two opposite sides.
  • the latter (10) are in the form of studs having threads exposed at both ends and thus projecting at both sides of the sub-assembly for cooperation with other parts to be mounted thereon, as described below.
  • FIG. 4 it will be seen that in the central portion of the figure the sub-assembly comprising the parts illustrated in FIG. 3 are shown in assembled relation, instead of the exploded relation illustrated in FIG. 3.
  • the perforated backing plates are indicated at 11 in exploded relation at each side of the central sub-assembly.
  • spacer elements 12 formed for example of blotting paper. These may be distributed in any of a variety of patterns over the area of the backing plates, for instance in the form of strips 12 as illustrated and interconnected in a network or windowed" pattern, and further including pips" or small individual or isolated pieces such as indicated at 15.
  • edges or flanges 13 are provided at the perimeter of the marginal strips 12 (see also FIG. 2), and these flanges extend outwardly to overlie the edges of the perforated plates 11, thereby providing for centering the backing plate assembly in the frame opening.
  • each of the backing plates is divided into five sections or strips positioned in edge-to-edge relation, as clearly appears in FIGS. 1 and 4.
  • the adjacent edges of the backing plates are separated from each other and therefore electrically isolated from each other in order that the backing plates may be separately connected with the signal current feed system.
  • adhesive strips 14 are applied to the plates in the manner clearly shown in FIGS. 1, 2 and 4.
  • the separator strips 12 if desired may also be coated with an adhesive so that when the backing plates and the separator strips are brought together they will adhere to each other.
  • small adhesively coated pieces 15 of separator material such as blotting paper may be applied to the backing plates in the middle of each of the windows" of the separator strip network 12, as is indicated in FIGS. 1,2 and 4.
  • a set of backing plates and separator parts may be assembled together and then placed within the frame at each side of the speaker assembly, with the separator strips in contact with the membrane at that side.
  • Slabs of cellular resin material such as indicated at 16 are then applied to the outer faces of the backing plates, and preferably these slabs extend over the entire area of the speaker within the frames 5.
  • the foam slabs are urged into pressure engagement with the backing plates by the fastening devices here shown in the form of metal strips 17 the main portion of each of which lies in the plane perpendicular to the plane of the speaker but each of which has bent and apertured ends 18 cooperating with the projecting threaded ends of the bolts and secured thereto by means of nuts 19.
  • an insulating ferrule 20 is applied in order to electrically isolate the strips 17 from the bolts 10. This insulation of the strips 17 from the foam is of advantage for the following reasons.
  • the foam is normally an effective insulating material, nevertheless under certain conditions, especially conditions of high relative humidity, the foam may temporarily accumulate sufficient moisture to constitute a leakage path, and as the foam is in contact with the backing plates, and the bolts for mounting the strips 17 are in contact with the conductive surfaces of the membranes, the electrical insulation of the strips with relation to the mounting bolts will avoid leakage between the backing plates and the conductive coatings of the membranes, even under adverse conditions of high relative humidity.
  • the foam slabs 16 have contact throughout the area of the perforated plates.
  • the foam slabs in fact apply some pressure to the plates and thereby urge the separator strips 12 into contact with the outer faces of the membranes.
  • the separator strips or spacers at opposite faces of the two membranes are preferably positioned in registry with each other, so that the effect of the pressure applied by the foam slabs is to clamp the membranes together between the separator strips, as clearly appears in FIG. 2. It is not intended and not necessary that this pressure be a heavy pressure, but only sufficient to provide the desired damping action on the plates themselves. A suitable force would be on the order of about 1% pounds at each retaining nut 19.
  • the two membranes of the double ended or pushpull speaker illustrated and described are thus clamped together under the action of the foam slabs on the backing plates and separator means, when the speaker is in use, the membranes separate from each other in substantially all of the area thereof lying between the opposed separator elements 12 and 15. This separation occurs in consequence of the biasing field, provided, for example, by a biasing voltage which is applied across the perforated plates and the conductive coatings on the membranes. The action of the biasing voltage is to draw the adjacent membrane toward the backing plate. This separation of the various membrane areas is indicated in FIG. 2.
  • the separator strips 12 Since the pressure of engagement of the membranes by the separator strips 12 is not great, and since the separator strips 12 are advantageously formed of a fibrous type of material such as blotting paper, leakage of air between the membranes even in the areas where they are engaged by the separator strips readily occurs. If desired, in order to assure this venting action of the intermembrane space, the separator strips may be provided with embossed grooves such as indicated at 22 in FIG. 4.
  • the arrangement described is also of importance because it enables maintenance of a closer spacing between the membranes of a double ended electrostatic speaker than has been practicable heretofore and this reduces the total volume of the air film between the membranes thereby increasing the acoustic coupling between the membranes.
  • the system of foam slab damping for the backing plates, with the slabs in contact over virtually the entire area of the backing plates, is also highly advantageous for the following reasons. Not only does the foam damping prevent unwanted resonances in the backing plates, but in addition the arrangement of the damping elements with the means for clamping the membranes between the damping slabs at opposite sides of the speaker assembly provides for establishing a more uniform spacing between each membrane and its associated backing plate or plates. This uniformity is of importance because it provides uniform power output over the entire area of the speaker, at the low end of the frequency response range. Nonuniform spacing between the backing plates and the active area of the membranes tends to limit the low frequency power handling ability of the speaker.
  • the two speakers incorporated in and acoustically coupled with each other in the assembly be fed with signal voltages in push-pull fashion.
  • the signal voltage is of course superimposed upon the bias voltage, as is known in the art of electrostatic speakers.
  • the sectionalizing of the backing plates provides for separate feed of the signal voltage, for instance through a network as described in the copending application above referred to.
  • an electrical connection 23 is extended from each of the backing plates, and the network employed in association with the backing plates may be arranged either in the manner shown in the copending application above referred to or in some other desired manner, the signal bias voltage being connected across the network and the connection 25 which is made to one of the contact strips lying between the coated surfaces of the membranes 7.
  • this entire windowed separator structure may be stamped out of the central area of the same sheet from which the gaskets 8 are formed.
  • the gaskets 8 are the elements positioned at the outer face of the margins of the membranes in order to provide clamping action against the contact strips 6.
  • holes 26 are provided in the corners of the speaker frames 5 and also in various of the intervening parts which are clamped in the frames, these holes being provided as an aid to mounting the speaker, for instance in a speaker cabinet.
  • the corners of the membranes 7, as seen in FIG. 3, do not have holes aligned with the frame holes 26, but it is to be understood that when the parts are assembled and mounting bolts or screws are inserted into the holes 26, the membranes are readily punctured to pass the bolts or screws.
  • the holes provided in the corners for mounting bolts may desirably be provided with insulating sleeves, so that the mounting bolts will not have contact either with the membranes or with the contact strips.
  • polyurethane foam is suitable, although it is preferred that the foam employed be of open cell or pore structure, preferably of rather large pore size, with extensive intercommunication between the open pores, so that the foam structure represents substantially nothing more than a skeleton or loose network of relatively thin and fragmentary skeletal strands without intervening membranes or cell walls.
  • the pore count averages 25 pores per linear inch.
  • a typical polyurethane foam employed in accordance with the invention weighs only about 31 ounces per cubic foot.
  • the mounting of the perforated plates and the spacers l2, and also of the foam slabs independently of the gripping or clamping of the membranes between the frames 5 is of considerable advantage from the standpoint of production or manufacturing techniques. Since the membranes are initially placed in tension and then clamped between the frames in that condition, the sub-assembly of the frames and membranes may be immediately removed from the equipment and jigs employed for this operation and then the sub-assembly may be brought together with other parts at another work station. In this way the production capacity of the equipment for tensioning and mounting the membranes is increased, because it is not necessary to perform other operations in the equipment for tensioning the membranes and clamping them between the frames.
  • a further advantage of the frame and membrane assembly is that vibrational modes of the membrane may be examined prior to final assembly, thereby enabling improved quality control.
  • damping means for each side of the speaker assembly comprises a single slab of cellular material overlying substantially the entire area of the backing plates at that side, but also in arrangements in which damping means comprises elements of lesser extent, i.e., strips or the like which may engage edge portions only of the backing plates.
  • the arrangement of the invention has the further advantage of providing for ready combining of frame member assemblies which may have different tensioning or which may incorporate membranes of different thicknesses, together with various back plate configurations and spacings, to meet a variety of acoustic requirements.
  • Still another advantage of the arrangement described incorporating the slabs of foamed material at opposite sides of the speaker is the fact that the foam slabs, although acoustically transparent, in effect, constitute filters which prevent atmospheric dust from reaching the backing plates or the membranes, which are highly charged and therefore tend to attract dust particles.
  • An electrostatic speaker comprising a pair of planar frames, a pair of membranes having conductive coatings presented face to face and having an inter-membrane space, electrical contact means between the membranes, the outer faces of the membranes being exposed within the frames and the membranes being clamped between the frames with the membranes under tension and with the inter-membrane space vented to atmosphere, a pair of electrically conductive perforated planar backing plates overlying the outer faces of the membranes, the membranes and the backing plates being spaced from each other throughout the entire area of the backing plates, spacing elements between each backing plate and the adjacent membrane for maintaining the spacing therebetween, and porous foam slabs at the outer faces of the plates mounted to apply pressure against the plates and thus urge them against each other with the membranes and the spacing elements therebetween.
  • An electrostatic speaker comprising a tensioned flexible membrane having a conductive coating on at least one face, an electrically conductive substantially rigid and perforated backing plate spaced at one face of the membrane, means for establishing electrical circuit connections with the conductive coating on the membrane and with said plate to provide for connection with a signal source adapted to effect sound generating motion of the membrane with respect to the backing plate, and means for imposing a damping action on the backing plate comprising an acoustically transparent foam slab in engagement with the face of the backing plate presented away from the membrane and spaced elements overlying the foam slab and acting against the slab in a direction perpendicular to and toward the backing plate to establish and maintain pressure engagement of the slab with the backing plate.
  • An electrostatic speaker comprising a tensioned flexible membrane having a conductive coating on at least one face, an electrically conductive substantially rigid perforated backing plate at one face of the membrane, the membrane and the backing plate being spaced from each other throughout the entire area of the backing plate, means for establishing electrical circuit connections with the conductive coating on the membrane and with said plate to provide for connection with a signal source adapted to effect sound generating motion
  • the damping means at one side face of the backing plate comprises separator strips between limited areas of the backing plate and the membrane, and in which the damping means at the other side of the plate comprises a slab of cellular resin material in contact with at least most of the area of the backing plate.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)
US820888A 1969-05-01 1969-05-01 Electrostatic speaker Expired - Lifetime US3654403A (en)

Applications Claiming Priority (1)

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US82088869A 1969-05-01 1969-05-01

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US820888A Expired - Lifetime US3654403A (en) 1969-05-01 1969-05-01 Electrostatic speaker

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US (1) US3654403A (enrdf_load_stackoverflow)
JP (1) JPS5224405B1 (enrdf_load_stackoverflow)
DE (1) DE2021656B2 (enrdf_load_stackoverflow)
GB (1) GB1273476A (enrdf_load_stackoverflow)

Cited By (32)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3892927A (en) * 1973-09-04 1975-07-01 Theodore Lindenberg Full range electrostatic loudspeaker for audio frequencies
WO1999056498A1 (en) * 1998-04-27 1999-11-04 Panphonics Oy Acoustic element
US6175636B1 (en) 1998-06-26 2001-01-16 American Technology Corporation Electrostatic speaker with moveable diaphragm edges
US6188772B1 (en) 1998-01-07 2001-02-13 American Technology Corporation Electrostatic speaker with foam stator
US6304662B1 (en) 1998-01-07 2001-10-16 American Technology Corporation Sonic emitter with foam stator
US20020076069A1 (en) * 1998-01-07 2002-06-20 American Technology Corporation Sonic emitter with foam stator
US20020191808A1 (en) * 2001-01-22 2002-12-19 American Technology Corporation Single-ended planar-magnetic speaker
US20040009716A1 (en) * 2002-05-02 2004-01-15 Steere John F. Electrical connectors for electro-dynamic loudspeakers
US20040022408A1 (en) * 2002-05-02 2004-02-05 Mango Louis A. Frame structure
US20040022409A1 (en) * 2002-05-02 2004-02-05 Hutt Steven W. Film attaching system
US20040022406A1 (en) * 2002-05-02 2004-02-05 Hutt Steven W. Magnet arrangement for loudspeaker
US20040022407A1 (en) * 2002-05-02 2004-02-05 Steere John F. Film tensioning system
US20040042632A1 (en) * 2002-05-02 2004-03-04 Hutt Steven W. Directivity control of electro-dynamic loudspeakers
US20040182642A1 (en) * 2003-01-30 2004-09-23 Hutt Steven W. Acoustic lens system
US20050089176A1 (en) * 1999-10-29 2005-04-28 American Technology Corporation Parametric loudspeaker with improved phase characteristics
US20050100181A1 (en) * 1998-09-24 2005-05-12 Particle Measuring Systems, Inc. Parametric transducer having an emitter film
US20050195985A1 (en) * 1999-10-29 2005-09-08 American Technology Corporation Focused parametric array
US7035425B2 (en) 2002-05-02 2006-04-25 Harman International Industries, Incorporated Frequency response enhancements for electro-dynamic loudspeakers
US7149321B2 (en) 2002-05-02 2006-12-12 Harman International Industries, Incorporated Electro-dynamic loudspeaker mounting system
US20060280315A1 (en) * 2003-06-09 2006-12-14 American Technology Corporation System and method for delivering audio-visual content along a customer waiting line
US7155026B2 (en) 2002-05-02 2006-12-26 Harman International Industries, Incorporated Mounting bracket system
US7236608B2 (en) 2002-05-02 2007-06-26 Harman International Industries, Incorporated Conductors for electro-dynamic loudspeakers
US20070189548A1 (en) * 2003-10-23 2007-08-16 Croft Jams J Iii Method of adjusting linear parameters of a parametric ultrasonic signal to reduce non-linearities in decoupled audio output waves and system including same
US7627134B2 (en) 2002-05-02 2009-12-01 Harman International Industries, Incorporated Magnet retention system in planar loudspeakers
US8275137B1 (en) 2007-03-22 2012-09-25 Parametric Sound Corporation Audio distortion correction for a parametric reproduction system
US8767979B2 (en) 2010-06-14 2014-07-01 Parametric Sound Corporation Parametric transducer system and related methods
US8903104B2 (en) 2013-04-16 2014-12-02 Turtle Beach Corporation Video gaming system with ultrasonic speakers
US8934650B1 (en) 2012-07-03 2015-01-13 Turtle Beach Corporation Low profile parametric transducers and related methods
US8958580B2 (en) 2012-04-18 2015-02-17 Turtle Beach Corporation Parametric transducers and related methods
US8988911B2 (en) 2013-06-13 2015-03-24 Turtle Beach Corporation Self-bias emitter circuit
US9036831B2 (en) 2012-01-10 2015-05-19 Turtle Beach Corporation Amplification system, carrier tracking systems and related methods for use in parametric sound systems
US9332344B2 (en) 2013-06-13 2016-05-03 Turtle Beach Corporation Self-bias emitter circuit

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE505752C2 (sv) * 1995-12-22 1997-10-06 Tore Fors Högtalare

Citations (9)

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US1776112A (en) * 1929-04-08 1930-09-16 Ephraim Banning Loud-speaker condenser
US1816992A (en) * 1928-05-16 1931-08-04 Vogt Hans Sounding condenser
GB881584A (en) * 1958-12-02 1961-11-08 Standard Telephones Cables Ltd Improvements in or relating to electro-acoustic transducers
US3084229A (en) * 1960-03-11 1963-04-02 Ampex Electrostatic earphone
US3136867A (en) * 1961-09-25 1964-06-09 Ampex Electrostatic transducer
GB1059307A (en) * 1965-02-12 1967-02-15 Alexander Shackman Improvements in electrostatic loudspeakers
US3389226A (en) * 1964-12-29 1968-06-18 Gen Electric Electrostatic loudspeaker
US3393764A (en) * 1966-12-27 1968-07-23 Curtiss R. Schafer Loudspeaker systems
US3496307A (en) * 1967-12-30 1970-02-17 Nippon Musical Instruments Mfg Loudspeaker

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1816992A (en) * 1928-05-16 1931-08-04 Vogt Hans Sounding condenser
US1776112A (en) * 1929-04-08 1930-09-16 Ephraim Banning Loud-speaker condenser
GB881584A (en) * 1958-12-02 1961-11-08 Standard Telephones Cables Ltd Improvements in or relating to electro-acoustic transducers
US3084229A (en) * 1960-03-11 1963-04-02 Ampex Electrostatic earphone
US3136867A (en) * 1961-09-25 1964-06-09 Ampex Electrostatic transducer
US3389226A (en) * 1964-12-29 1968-06-18 Gen Electric Electrostatic loudspeaker
GB1059307A (en) * 1965-02-12 1967-02-15 Alexander Shackman Improvements in electrostatic loudspeakers
US3393764A (en) * 1966-12-27 1968-07-23 Curtiss R. Schafer Loudspeaker systems
US3496307A (en) * 1967-12-30 1970-02-17 Nippon Musical Instruments Mfg Loudspeaker

Cited By (45)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3892927A (en) * 1973-09-04 1975-07-01 Theodore Lindenberg Full range electrostatic loudspeaker for audio frequencies
US6188772B1 (en) 1998-01-07 2001-02-13 American Technology Corporation Electrostatic speaker with foam stator
US6304662B1 (en) 1998-01-07 2001-10-16 American Technology Corporation Sonic emitter with foam stator
US20020076069A1 (en) * 1998-01-07 2002-06-20 American Technology Corporation Sonic emitter with foam stator
WO1999056498A1 (en) * 1998-04-27 1999-11-04 Panphonics Oy Acoustic element
US6175636B1 (en) 1998-06-26 2001-01-16 American Technology Corporation Electrostatic speaker with moveable diaphragm edges
US20050100181A1 (en) * 1998-09-24 2005-05-12 Particle Measuring Systems, Inc. Parametric transducer having an emitter film
US20050089176A1 (en) * 1999-10-29 2005-04-28 American Technology Corporation Parametric loudspeaker with improved phase characteristics
US8199931B1 (en) 1999-10-29 2012-06-12 American Technology Corporation Parametric loudspeaker with improved phase characteristics
US20050195985A1 (en) * 1999-10-29 2005-09-08 American Technology Corporation Focused parametric array
US20020191808A1 (en) * 2001-01-22 2002-12-19 American Technology Corporation Single-ended planar-magnetic speaker
US20070127767A1 (en) * 2001-01-22 2007-06-07 American Technology Corporation Single-ended planar-magnetic speaker
US7142688B2 (en) 2001-01-22 2006-11-28 American Technology Corporation Single-ended planar-magnetic speaker
US7155026B2 (en) 2002-05-02 2006-12-26 Harman International Industries, Incorporated Mounting bracket system
US20040022409A1 (en) * 2002-05-02 2004-02-05 Hutt Steven W. Film attaching system
US20040042632A1 (en) * 2002-05-02 2004-03-04 Hutt Steven W. Directivity control of electro-dynamic loudspeakers
US20040022407A1 (en) * 2002-05-02 2004-02-05 Steere John F. Film tensioning system
US7035425B2 (en) 2002-05-02 2006-04-25 Harman International Industries, Incorporated Frequency response enhancements for electro-dynamic loudspeakers
US20040022406A1 (en) * 2002-05-02 2004-02-05 Hutt Steven W. Magnet arrangement for loudspeaker
US7146017B2 (en) 2002-05-02 2006-12-05 Harman International Industries, Incorporated Electrical connectors for electro-dynamic loudspeakers
US7149321B2 (en) 2002-05-02 2006-12-12 Harman International Industries, Incorporated Electro-dynamic loudspeaker mounting system
US7716808B2 (en) 2002-05-02 2010-05-18 Harman International Industries, Incorporated Method of attaching a diaphragm to a frame for a planar loudspeaker
US7627134B2 (en) 2002-05-02 2009-12-01 Harman International Industries, Incorporated Magnet retention system in planar loudspeakers
US7152299B2 (en) 2002-05-02 2006-12-26 Harman International Industries, Incorporated Method of assembling a loudspeaker
US7203332B2 (en) 2002-05-02 2007-04-10 Harman International Industries, Incorporated Magnet arrangement for loudspeaker
US20040022408A1 (en) * 2002-05-02 2004-02-05 Mango Louis A. Frame structure
US7236608B2 (en) 2002-05-02 2007-06-26 Harman International Industries, Incorporated Conductors for electro-dynamic loudspeakers
US20040009716A1 (en) * 2002-05-02 2004-01-15 Steere John F. Electrical connectors for electro-dynamic loudspeakers
US7278200B2 (en) 2002-05-02 2007-10-09 Harman International Industries, Incorporated Method of tensioning a diaphragm for an electro-dynamic loudspeaker
US20080172859A1 (en) * 2002-05-02 2008-07-24 Hutt Steven W Method of attaching a diaphragm to a frame for a planar loudspeaker
US7316290B2 (en) 2003-01-30 2008-01-08 Harman International Industries, Incorporated Acoustic lens system
US20040182642A1 (en) * 2003-01-30 2004-09-23 Hutt Steven W. Acoustic lens system
US20060280315A1 (en) * 2003-06-09 2006-12-14 American Technology Corporation System and method for delivering audio-visual content along a customer waiting line
US7564981B2 (en) 2003-10-23 2009-07-21 American Technology Corporation Method of adjusting linear parameters of a parametric ultrasonic signal to reduce non-linearities in decoupled audio output waves and system including same
US20070189548A1 (en) * 2003-10-23 2007-08-16 Croft Jams J Iii Method of adjusting linear parameters of a parametric ultrasonic signal to reduce non-linearities in decoupled audio output waves and system including same
US8275137B1 (en) 2007-03-22 2012-09-25 Parametric Sound Corporation Audio distortion correction for a parametric reproduction system
US8767979B2 (en) 2010-06-14 2014-07-01 Parametric Sound Corporation Parametric transducer system and related methods
US8903116B2 (en) 2010-06-14 2014-12-02 Turtle Beach Corporation Parametric transducers and related methods
US9002032B2 (en) 2010-06-14 2015-04-07 Turtle Beach Corporation Parametric signal processing systems and methods
US9036831B2 (en) 2012-01-10 2015-05-19 Turtle Beach Corporation Amplification system, carrier tracking systems and related methods for use in parametric sound systems
US8958580B2 (en) 2012-04-18 2015-02-17 Turtle Beach Corporation Parametric transducers and related methods
US8934650B1 (en) 2012-07-03 2015-01-13 Turtle Beach Corporation Low profile parametric transducers and related methods
US8903104B2 (en) 2013-04-16 2014-12-02 Turtle Beach Corporation Video gaming system with ultrasonic speakers
US8988911B2 (en) 2013-06-13 2015-03-24 Turtle Beach Corporation Self-bias emitter circuit
US9332344B2 (en) 2013-06-13 2016-05-03 Turtle Beach Corporation Self-bias emitter circuit

Also Published As

Publication number Publication date
DE2021656C3 (enrdf_load_stackoverflow) 1979-08-16
GB1273476A (en) 1972-05-10
JPS5224405B1 (enrdf_load_stackoverflow) 1977-07-01
DE2021656A1 (de) 1970-11-05
DE2021656B2 (de) 1978-12-14

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