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US3345469A - Electrostatic loudspeakers - Google Patents

Electrostatic loudspeakers Download PDF

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Publication number
US3345469A
US3345469A US348668A US34866864A US3345469A US 3345469 A US3345469 A US 3345469A US 348668 A US348668 A US 348668A US 34866864 A US34866864 A US 34866864A US 3345469 A US3345469 A US 3345469A
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diaphragm
eslu
fixed
sound
electrode
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Robert L Rod
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ROD DEV CORP
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ROD DEV CORP
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Priority to BE660447D priority patent/BE660447A/xx
Priority to NL6502604A priority patent/NL6502604A/xx
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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

  • An electrostatic loudspeaker comprised of a flexible wire mesh semi-rigid electrode and a flexible electrode with dielectric foil between them entrapping one or more strata of gas between one or more layers of foil and/ or the flexible electrode.
  • the structure is flexible enough to be rolled into a cylinder'and used as a lampshade.
  • the spacing between electrodes can be specified to provide bays of different spacings, to favor specified audible frequency bands.
  • This invention relates to loudspeakers and, particularly, to the class of sound reproducers operating on electrostatic principles.
  • the forces required to move a sound-producing diaphragm are generated by varying electric charges applied toappropriate electrical conductors.
  • the objects of my invention are m'ultifold in number.
  • One object is to make feasible the construction of electrostatic loudspeakers at acost equal to or less than moving coil loudspeakers of com-parable sound output levels and acoustical quality.
  • Another object is to produce a full-range loudspeaker that faithfully reproduces the entire audio frequency spectrum up to about 20,000 c.p.s.
  • Still another object is to build a loudspeaker that can be flexed or bent, as desired, for applications such as pillow and mattress speakers, collapsible talking movie projection screens, sound generating lamp shades, and others too numerous to list.
  • Another important object of my invention is to simplify the construction of electrostatic loudspeakers by reducing the inordinately high signal and bias voltages heretofore required. In so doing, I have produced electrostatic loudspeakers that may be driven directly from the standardized 70.7 volt signal outputs of public address amplifiers and similar wired sound systems without intervening voltage step up transformers.
  • electrostatic speakers of contemporary design have yet to supplant the universally used moving coil loudspeaker.
  • the reasons for the poor acceptance of full range electrostatic loudspeakers developed up to the present time are many. They include undue mechanical complexity, a need for a comparatively large radiating area, and a dependence upon dangerously high voltages.
  • Virtually all such electrostatic loudspeaker units (abbreviated hereinafter as ESLU for brevity) that have reached the market have made use of a taut, free-moving, electrically conductive diaphragm spaced in air some uniform distance away from one fixed electrically insulated rigid electrode or between two fixed insulated rigid electrodes.
  • the essentially obsolete onefixed-electrode device is commonly called a singleended ESLU, while the more modern double-fixed-electrode unit is known as a push-pull speaker.
  • a typical fullrange push-pull ESLU now commercially offered to the public requires a bias source of 3,500 volts DC, and a driving amplifier with a power capacity of from to 75 Watts, the latter to achieve a sufiiciently high drive voltage across an almost purely reactive load.
  • the unit has a radiating area of over six square feet on each face.
  • an electrostatic sound reproducer of the type having a movable electroded diaphragm and at least one fixed electrode adjacent thereto comprising, an acoustically transparent electrically-conductive semi-rigid fixed electrode, a flexible diaphragm comprising conductive electrode means extending over its active area-confronting said fixed electrode at one side thereof, dielectric means disposed between said electrode means and said fixed electrode, and means holding said diaphragm fixed 3 to said fixed electrode along a line perimetrically bounding said active area.
  • my invention provides an electrostatic sound reproducer of the type having a movable electroded diaphragm and at least one fixed electrode adjacent thereto comprising, an acoustically-transparent electrically conductive fixed electrode, a flexible diaphragm comprising conductive electrode means extending over its active area confronting said fixed electrode at one side thereof, a dielectric film disposed between said diaphragm and said fixed electrode, means substantially hermetically sealing said diaphragm to said film along a line perimetrically bounding said active area whereby to entrap a stratum of gas between said diaphragm and said film, and means holding said diaphragm fixed to said fixed electrode along said line.
  • FIG. 1 is a. vertical section through an electrostatic sound reproducer according to the invention, in which the horizontal scale is expanded or exaggerated to simplify the illustration;
  • FIG. 2 is a front view of a reproducer made according to FIG. 1 and having the additional feature that it is divided into bays or sections which individually favor different frequency ranges;
  • FIG. 3 is a partial vertical sectional illustrating the combination of my loudspeaker and a light-reflective acoustically-transparent material capable of serving the purposes of a picture-projection screen and a loudspeaker simultaneously;
  • FIG. 4 is a side view, partially in vertical section, of a lamp incorporating my loudspeaker as a lampshade;
  • FIG. 5 is a cross-section taken along line 55 in FIG. 4;
  • FIG. 6 is a circuit diagram of the loudspeaker configuration shown in FIG. 4.
  • FIG. 7 is a partial vertical section through another embodiment of my electrostatic sound reproducer.
  • FIG. 1 is shown an elemental (e.g., one foot square) push-pull ESLU bay or unit as used in my invention, the horizontal scale being exaggerated to permit a clear illustration of some of its details.
  • the exact size is not particularly critical and the exemplary size is cited only as an example. Neither is the shape or curvature particularly critical.
  • I show a centrally situated flexible dielectric diaphragm 1, preferably ranging in thickness from 0.25 mil to one mil, which has been coated on both faces with thin flexible electrically conductive layers 2, 3, preferably of evaporated aluminum or other lightweight material.
  • the conductive layer can be limited to one side only, of the diaphragm, if desired.
  • the diaphragm may be a metalized plastic film (as shown), or it may be a flexible film which is itself conductive (not shown).
  • Polyethylene terephthalate, polypropylene or polyvinyl chloride, to name several commercially available materials, are in various degrees suitable as dielectric film materials for this application, since they are extraordinarily strong and lightweight.
  • On either side of the diaphragm 1 are one or more thin plastic dielectric sheets 6, 7, 10, 11 (two pairs of two each being shown), which I call buffers for convenience. The buffers are fastened and sealed around their edges to both the diaphragm l and to each other by narrow bands of double backed pressure sensitive adhesive tape 18, 19, 20, 21.
  • the peripheral seals may be made by heat sealing the sheets at the edges or with the use of appropriate adhesives.
  • Dielectric buffer elements 6, 7, 10, 11 are preferably sheets of extremely thin, high dielectric strength film such as polyethylene terephthalate, which is commonly known by the Du Pont trade name, Mylar, or polyvinyl chloride, known by the Dow trade name, Saran.
  • FIG. 1 which is drawn to an exaggerated horizontal scale for clarity, two socalled fixed electrodes 14, 15 are held a small but relatively uncritical distance away from the outermost buffers 10, 11, respectively, by means of peripheral spacers 22, 23, respectively. Average spacings of from 10 to 40 mils have been employed, but these are not limiting values. These spacers may be made of multiple layers of pressure sensitive adhesive tape or of any typical thin gasket sheeting, including compressed foamed plastic, cork, rubber, and the like. Electrical leads 16, 17 are connected to the electrically conductive fixed electrodes 14, 15, which are made of ordinary semi-rigid metal screening or wire mesh and which may be coated with electrical insulation materials (not shown) as will be described shortly. Another electrical lead 24 comprising the center-tap connection is made to the conductive diaphragm 1.
  • FIG. 1 The entire structure shown in FIG. 1 might at first be thought to resemble the common push-pull ESLU that is old in the art. (See e.g., the United States patents to Vogt 1,881,107 or Kellogg 1,983,377.) Differences which account for the remarkable improvement in the performance of my invention over earlier electrostatic loudspeakers now will be discussed.
  • the contemporary push-pull ESLU invariably makes use of a sandwich arrangement in which a movable diaphragm with its integral conductive coating is suspended to move freely back and forth in the air spaces between two insulated and perforated rigid fixed electrode plates. Spacing is such that contact between the diaphragm and the plates is avoided, even at maximum sound volume. Otherwise, undesirable distortion would occur.
  • the buffers may be omitted by using a pair of thin plastic diaphragms coated with conductive layers on their facing surfaces only, as is illustrated in FIG. 7.
  • the fixed electrodes 14 and 15, which are similar to the corresponding electrodes in FIG. 1, have a flexible diaphragm 51 between them, which comprises two con-fronting sheets 52, 53 of dielectric material having thin flexible electrically conductive electrode layers 54, 55, respectively, on their confronting surfaces. The opposite faces are then adequately insulated in themselves, but additional insulation of the fixed electrodes 14, 15 is a well-taken procedure.
  • Still another advantage inherent in the use of bulfers 6, 7, 10, 11 involves improvements in the magnitude of the electric charge over that achieved in a contemporary ESLU using air alone as the dielectric between the electrodes.
  • Conventional film materials I have used as buffers have a dielectric constant several times that of air.
  • the electric charge created by the bias and signal voltages that exists between electrodes is increased by a factor which bears a relation to the ratio of the dielectric constants of the buffer material employed and air.
  • the net effect of this improvement is that the combination of signal and bias voltages required to move the diaphragm a certain arbitrary distance has been reduced over that required in a conventional ESLU of similar dimensions.
  • the thickness of the buffers 6, 7, 10, 11, or combinations thereof should be kept to a minimum, preferably 0.25 mil each and no greater than several mils in total. Two reasons for this become apparent. The most obvious is that a buffer should be of light mass and have an acoustical impedance as close to air as possible. Otherwise, severe sound damping and loss in efliciency will become evident. The thinnest films thus are most useful.
  • Another feature of my invention is that the need for rigid fixed electrodes of perforated metal and the complex mounting frame has been obviated by my use of selfsupporting, semi-rigid metal screening or wire mesh electrodes 14, 15 that requires no special mounting provisions.
  • this type of material forms an ideal fixed electrode because, (a) it is almost perfectly transparent acoustically Whereas perforated metallic plates are not; (b) it is acoustically dead and thus does not rattle or self-resonate on sound peaks at certain frequencies; (c) it is sufiiciently rigid intrinsically, along with the support given by the opposite fixed electrode in the push pull case, to hold the over-all bay in shape; and, (d) it can, but need not be electrically insulated, as desired, with sprayed, brushed or dipped dielectric coatings, or by anodizing in the case of aluminum wire screening. In most applications, sheathing the fixed electrodes with high dielectric constant coatings is desirable for further increasing the strength and uniformity of the electricfield and
  • the diaphragm 1 is not held particularly taut in a complex and costly frame as in earlier loudspeakers of this type.
  • the over-all rigidity of a bay made in accordance with my principles is such that except for regions near its clamped edges, the diaphragm stiffness is a variable.
  • This feature satisfies another of Hunts requirements, namely a systematic variation in the diaphragm stiffness. Such variation tends to further improve the uniformity of the frequency response.
  • FIG. 2 is shown a typical ESLU of my design having approximate dimensions of 3 feet by 1 /2 feet by less than /2 inch in overall thickness. Such a unit has an adequate radiating area to produce sound levels of the magnitude required in general home entertainment use and in offices, restaurants and other public places.
  • I have illustrated the mechanical construction details of a multi-bay unit, employing the same reference characters as in FIG. 1 for like elements.
  • I have, for illustrative purposes, shown peeled off the various elements comprising the unit.
  • I have omitted from the drawing spacer 23 and the means for sealing the edges of the buffers and the diaphragm as previously described.
  • the major difference between the elemental bay shown in FIG. 1 and the multi-bay unit shown in FIG. 2 is the use of cross-members 30, 31, 32 (shown in solid-lines) to subdivide one larger unit into a number of smaller bays, in this case indicated at 26, 27, 28, 29.
  • the crossmembers are of identical construction to those used in FIG. 1 to seal and separate the various buffered films at their edges. In effect, four bays have been made from one, each bay being sealed from the others.
  • fixed electrodes 14, 15; diaphragm 1 and the buffers 6, 7, 10, 11 are all of identical size equal to the overall dimensions of the unit.
  • My use of a larger unit insures generation of sound at usefully high levels. It further permits me to make slight modifications to the frequency response by altering electrode spacings within the individual bays. Such a step is desirable in achieving a uniform distribution of various sound frequencies throughout the room in which the ESLU is used. As is well known, a large radiator of high frequency sounds will tend to focus the energy in a narrow beam. In the case of a flat ESLU that makes no allowances for this, low frequency sounds are broadly radiated, but the higher frequencies are concentrated in planes perpendicular to the diaphragm. The larger the unit, the more concentrated are the higher frequency sounds.
  • I overcome a problem especially noticeable in a fiat ESLU by varying the overall spacing between the diaphragm 1 and the fixed wire mesh electrodes 14, 15 in a predetermined manner.
  • spacers 22, 23 are thinner than those employed in the remaining bays 27, 28, 29. With less spacing, higher frequency sounds are. radiated more efficiently in bay 26 than in the other three. Thus, with a smaller radiating area for the higher frequencies being employed than that made available for the lower frequencies, the resultant higher frequency sounds are less focused.
  • bays 27, 28, 29 are more efficient radiators of low and medium range frequencies because of the added spacings being provided between the diaphragm and the two fixed electrodes. These allow for greater diaphragm excursions.
  • the ESLU can be made extremely flexible so that 'it can be rolled up like a window shade.
  • an outer face of one of the fixed wire mesh electrodes 15 can be provided with a suitable acoustically transparent cloth 15.5 to serve a combined motion picture projector screen and loudspeaker cover, as is shown in FIG. 3.
  • outer coverings that are acoustically transparent can be employed for decorative or advertising purposes. on such units.
  • FIGS. 4 and 5 a very simplified sketch of my ESLU as applied to a lamp assembly of the type commonly found in the home.
  • FIG. 5 is drawn to larger scale than FIG. 4, to facilitate illustration of its details.
  • ESLU 33 is mounted as a lampshade in place of the conventional shade on the same mounting framework ordinarily used. Elements similar in function to elements in FIG. 1 bear the same reference characters.
  • the speaker is a circular version of the elemental bay I described in FIG. 1, and only the outer fixed mesh electrode is illustrated 15 in FIG. 4.
  • the shape preferably is covered on the inner and outer surfaces by usual lampshade materials (not shown) that may be held in place by edging tapes 40*, 40. These lampshade materials, of course, should be and frequently are acoustically transparent.
  • Means (not shown) for supporting the ESLU 33 as a lampshade can be provided in a known manner.
  • ESLU ESLU
  • Conductive leads 34 feed bias and signal to the lampshade, while power cable 39 feeds mains voltage to the lamp and to the bias supply.
  • an optional loudspeaker 37 of the conventional electrodynamic type which may be used to augment the production of very low frequency sounds. This speaker is driven simultaneously with the ESLU and is arranged to reproduce only the lowest frequency sounds by means of a conventional cross-over network incorporated within assembly 35 or by virtue of its own construction. Cable 42 connects the sound generating portions of the unit to the radio or phonograph amplifier located elsewhere.
  • the ESLU is capable of faithful reproduction of lower frequency sounds
  • the general public often has a preference for hearing these boosted in amplitude above a natural level.
  • Base 38 is employed to support the entire structure, and to direct the output of the speaker 37 omnidirectionally throughout the room by means of a circular exponential horn comprised of the top surface 43. It will be noted that speaker 37 is arranged for convenience to radiate downwards, but other mounting positions can be employed if desired.
  • FIG. 6 a functional schematic diagram of one circuit I have used to energize the ESLU 33 shown in FIG. 4.
  • Leads 42 comprise the electrical signal input from a conventional amplifier having low output impedance. Since an ESLU is substantially a high impedance reactive load and requires a relatively high driving signal voltage, I employ in this case the usual step-up transformer 46 to develop the signal input voltages for ESLU 33 from signals developed across the low impedance terminals of conventional amplifiers. These signals are applied to the fixed electrodes 14, 15 through conductors 16, 17 about a center tap connection 47 in the secondary of transformer 46. Necessary bias voltage is developed by battery 45.
  • resistor 44 In series with the bias voltage developed by battery 45 is a resistor 44 of very high resistance value which serves a dual purpose of limiting current flow should short circuits develop in the ESLU and of minimizing distortion otherwise developed by the speaker.
  • This resistor for limiting distortion has evolved from the work of Professor Hunt and is described in his aforementioned text.
  • woofer speaker 37 energized via conductors 41.
  • This speaker may be especially built to emphasize low frequencies or it may contain a built-in crossover network of conventional design.
  • Transformer 46 may be eliminated in installations where adequate signal voltages are provided.
  • Battery 45 can be replaced by a conventional rectifier-type power supply energized from the mains voltage. Modifications can be made in the method of applying the signal voltages to the ESLU; such changes do not affect my invention, which concerns itself with my new ESLU per se.
  • the semi-rigid fixed electrodes 14, 15 of my invention can be made of wire mesh or screen, as shown, or, if desired, of an array of wires strung across the reproducer, or of any other suitable configuration of conductors.
  • reproducers according to my invention may employ rigid fixed electrodes according to the prior art, without loss of the low-voltage features of the invention.
  • materials suitable for use as the diaphragm include fiber glass cloth, woven synthetic cloths, and paper, all of which have been treated to close their pores and made electrically conductive on one or both sides, in addition to the materials mentioned hereinabove. No attempt has been made to illustrate all possible embodiments of the invention, but rather only to illustrate its principles and the best manner presently known to practice it.
  • An electrostatic sound reproducer of the type having a movable electroded diaphragm and at least one fixed electrode adjacent thereto comprising, an acousticallytransparent electrically conductive fixed electrode made of a semi-rigid material capable of being flexed by hand into a desired shape, a flexible diaphragm comprising conductive electrode means extending over its active area confronting said fixed electrode at one side thereof, a dielectric film disposed between said diaphragm and said fixed electrode, means substantially hermetically sealing said diaphragm to said film along a line perimetrically bounding said active area whereby to entrap a stratum of gas between said diaphragm and said film, and means holding said diaphragm fixed to said fixed electrode along said line.
  • An electrostatic sound reproducer of the type having a movable electroded diaphragm and at least one fixed electrode adjacent thereto comprising, a metallic wire mesh fixed electrode, a flexible dielectric diaphragm confronting said fixed electrode at one side of said diaphragm, a dielectric film disposed between said diaphragm and said fixed electrode, means substantially hermetically sealing said diaphragm to said film along a line perirnetrically bounding the active area of said diaphragm whereby to entrap a stratum of gas between said diaphragm and said film, means holding said diaphragm fixed to said fixed electrode along said line, and a flexible electrically conductive electrode aflixed to the other side of said diaphragm over said active area.
  • An electrostatic sound reproducer according to claim Z having a second electrically conductive electrode aflixed to said one side of said diaphragm over said active area.
  • An electrostatic sound reproducer comprising a second metallic wire mesh fixed electrode confronting the other side of said diaphragm, a second dielectric film disposed between said diaphragm and said second fixed electrode, means substantially hermetically sealing said diaphragm to said film along said line whereby to trap a second stratum of gas between said diaphragm and said second film, and means holding said diaphragm fixed to said second fixed electrode along said line.
  • An electrostatic sound reproducer comprising a semi-rigid metallic wire mesh fixed electrode, a dielectric confronting the dielectric film at one side and supported at its edges to the dielectric film and sealed whereby to entrap a stratum of gas between the film and the diaphragm, and a flexible electrically conductive electrode afiixed to the opposite side of the diaphragm.
  • An electrostatic sound reproducer comprising two metallic substantially concentric cylindrical semi-rigid wire mesh fixed electrodes, at least one continuously wound spiral forming a plurality of layers of a dielectric foil sealed at the spiral edges thereof to each of the fixed electrodes to form at least one entrapped stratum of gas therein, said spirals located between said electrodes, a flexible diaphragm located between said spirals of the dielectric foil, and means to entrap a stratum of gas between each of said spirals and said diaphragm, flexible electrically conductive electrode means afiixed to at least one side of the flexible diaphragm, and means to hold the spiral and cylindrical end edges of the complete struc ture in close contact.
  • An electrostatic sound reproducer comprising two metallic substantially concentric cylindrical semi-rigid wire mesh fixed electrodes, at least two assemblies of layers of dielectric foil sealed at their edges to form a plurality of entrapped gas strata therebetween, one located next to each of the fixed electrodes between said fixed electrodes and concentric therewith, two flexible diaphragms located between said foil assemblies with their confronting surfaces covered with flexible electrically con- References Cited UNITED STATES PATENTS 7/1929 De Forest 325---31O 4/ 1942 Crowley 325-3 10 1 2 Curry 179-111 Lindenberg 179-41 1 Stanton 179-111 Gorike 179111 Wright 179--111 Brettel 179-1 11 KATHLEEN H. CLAFFY, Primary Examiner.

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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)
US348668A 1964-03-02 1964-03-02 Electrostatic loudspeakers Expired - Lifetime US3345469A (en)

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Cited By (34)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3668336A (en) * 1969-12-08 1972-06-06 Dayton Wright Associates Ltd Audio system including electrostatic loudspeaker
US3895193A (en) * 1968-04-29 1975-07-15 Pond Chester C Cross-over network and bias voltage supply for dynamic-electrostatic speaker system
US4160882A (en) * 1978-03-13 1979-07-10 Driver Michael L Double diaphragm electrostatic transducer each diaphragm comprising two plastic sheets having different charge carrying characteristics
US4190746A (en) * 1976-03-19 1980-02-26 Harwood Hugh D Diaphragm material for moving coil loudspeaker, may be laminated or integral with surround
US4383139A (en) * 1981-02-21 1983-05-10 Bulgarsko Radio Electrostatic acoustic converter
WO1993001691A1 (en) * 1991-07-11 1993-01-21 Driver Michael L Electrolytic loudspeaker assembly
US5206557A (en) * 1990-11-27 1993-04-27 Mcnc Microelectromechanical transducer and fabrication method
US5479061A (en) * 1992-12-31 1995-12-26 University Of North Carolina Pleated sheet microelectromechanical transducer
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
US20020118856A1 (en) * 2001-01-26 2002-08-29 American Technology Corporation Planar-magnetic speakers with secondary magnetic structure
US20020191808A1 (en) * 2001-01-22 2002-12-19 American Technology Corporation Single-ended planar-magnetic speaker
US20050100181A1 (en) * 1998-09-24 2005-05-12 Particle Measuring Systems, Inc. Parametric transducer having an emitter film
US20070242844A1 (en) * 2006-04-14 2007-10-18 Murray R. Harman Electrostatic loudspeaker capable of dispersing sound both horizontally and vertically
DE102007007957A1 (de) * 2007-02-17 2008-08-21 Lyttron Technology Gmbh Lautsprecher aufgebaut aus Folien
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
DE102008047796A1 (de) 2008-09-17 2010-04-15 Siemens Aktiengesellschaft Vorrichtung zur Erzeugung von breitbandigem Schall im Hörbereich des Menschen
US8199931B1 (en) 1999-10-29 2012-06-12 American Technology Corporation Parametric loudspeaker with improved phase characteristics
US8275137B1 (en) 2007-03-22 2012-09-25 Parametric Sound Corporation Audio distortion correction for a parametric reproduction system
US8670581B2 (en) 2006-04-14 2014-03-11 Murray R. Harman Electrostatic loudspeaker capable of dispersing sound both horizontally and vertically
US8767979B2 (en) 2010-06-14 2014-07-01 Parametric Sound Corporation Parametric transducer system and related methods
US20140321675A1 (en) * 2012-03-30 2014-10-30 Tokai Rubber Industries, Ltd. Speaker
WO2014189862A1 (en) * 2013-05-20 2014-11-27 Aliphcom Combination speaker and light source responsive to state(s) of an environment based on sensor data
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
US20170118562A1 (en) * 2013-12-23 2017-04-27 Disney Enterprises, Inc. Flexible, shapeable free-form electrostatic speakers
DE102017107958A1 (de) * 2017-04-12 2018-10-18 AIFC Unternehmensförderungsgesellschaft mbH & Co. KG Lautsprecher mit aufrollbarer Membrane
US20190306631A1 (en) * 2018-03-27 2019-10-03 Sony Corporation Loudspeaker system

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US2278835A (en) * 1940-06-24 1942-04-07 Daniel J Crowley Combined lamp and radio receiving set
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US3030457A (en) * 1958-08-07 1962-04-17 Gorike Rudolf Electrostatic microphone
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US3136867A (en) * 1961-09-25 1964-06-09 Ampex Electrostatic transducer

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US1720544A (en) * 1923-04-28 1929-07-09 Forest Radio Telephone & Teleg Radio receiving apparatus
US2278835A (en) * 1940-06-24 1942-04-07 Daniel J Crowley Combined lamp and radio receiving set
US2855467A (en) * 1953-12-11 1958-10-07 Curry Electronics Inc Loud speakers
US2934611A (en) * 1955-11-09 1960-04-26 Pickering Associates Inc Electrostatic speaker
US2934612A (en) * 1957-10-24 1960-04-26 Walter O Stanton Electrostatic speaker
US3030457A (en) * 1958-08-07 1962-04-17 Gorike Rudolf Electrostatic microphone
US3135838A (en) * 1958-12-10 1964-06-02 Wright St George Lab Inc Electrostatic loudspeaker
US3136867A (en) * 1961-09-25 1964-06-09 Ampex Electrostatic transducer

Cited By (50)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3895193A (en) * 1968-04-29 1975-07-15 Pond Chester C Cross-over network and bias voltage supply for dynamic-electrostatic speaker system
US3668336A (en) * 1969-12-08 1972-06-06 Dayton Wright Associates Ltd Audio system including electrostatic loudspeaker
US4190746A (en) * 1976-03-19 1980-02-26 Harwood Hugh D Diaphragm material for moving coil loudspeaker, may be laminated or integral with surround
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BE660447A (xx) 1965-07-01
NL6502604A (xx) 1965-09-03

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