WO2015075432A1 - Haut-parleurs et circuits de commande de haut-parleurs - Google Patents

Haut-parleurs et circuits de commande de haut-parleurs Download PDF

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Publication number
WO2015075432A1
WO2015075432A1 PCT/GB2014/053404 GB2014053404W WO2015075432A1 WO 2015075432 A1 WO2015075432 A1 WO 2015075432A1 GB 2014053404 W GB2014053404 W GB 2014053404W WO 2015075432 A1 WO2015075432 A1 WO 2015075432A1
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WO
WIPO (PCT)
Prior art keywords
layer
delay line
conductive
cell structure
electrode
Prior art date
Application number
PCT/GB2014/053404
Other languages
English (en)
Inventor
Philip Alistair TREVELYAN
Timothy John MELLOW
Original Assignee
Mellow Acoustics Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB1320407.8A external-priority patent/GB2520352A/en
Priority claimed from GB1320405.2A external-priority patent/GB2520351B/en
Application filed by Mellow Acoustics Limited filed Critical Mellow Acoustics Limited
Publication of WO2015075432A1 publication Critical patent/WO2015075432A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers
    • H04R19/01—Electrostatic transducers characterised by the use of electrets
    • 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 present invention relates to electrostatic loudspeakers.
  • the present invention also relates to electrode assemblies for electrostatic loudspeakers.
  • the present invention also relates to drive circuits for electrostatic loudspeakers.
  • the present invention also relates to systems comprising electrostatic loudspeakers and drive circuits.
  • the present invention also relates to electrical connection arrangements, in particular but not limited to, electrical connection arrangements for electrostatic loudspeakers.
  • electrostatic loudspeakers have a large perforated steel mesh frame that supports two very high voltage perforated steel mesh stators.
  • a thin, for example 3-20pm thick, tensioned membrane also called diaphragm
  • the diaphragm stores electric charge.
  • the membrane is coated with a charge-storing coating.
  • curvature stiffens the diaphragm and therefore attenuates the low- frequency response.
  • Another known approach is to use membrane strips arranged in an arc, but this tends to add mechanical complexity.
  • Another known approach is to feed concentric ring electrodes from a delay line such that sound emanates from the centre of the diaphragm first and the edge last in order to provide a virtual dipole point source.
  • known delay lines are lossy and therefore relatively ineffective at the highest frequencies.
  • WO 84/04865 A1 is relatively complicated to manufacture. Also, the present inventors have realised the arrangement of WO 84/04865 A1 has a number of performance limitations introduced by its mechanical form, for example a relatively high ratio of the closed area of its elements to its total area, which is undesirable.
  • the present inventors have further realised it would be desirable to provide a non-lossy (or less lossy) delay line that is practicable to implement with an electrostatic loudspeaker.
  • the invention provides an electrode assembly for an electrostatic loudspeaker, the electrode assembly comprising: a conductive cell structure layer comprising a layer of a structure comprising an array of hollow cells formed between elongated walls; and a charge storing insulator layer arranged adjacent to the conductive cell structure layer.
  • the conductive cell structure layer comprising a layer of a structure comprising an array of hollow cells formed between elongated walls may be a conductive honeycomb layer.
  • the electrode assembly may further comprise an insulating cell structure layer (the insulating cell structure layer comprising a layer of a structure comprising an array of hollow cells formed between elongated walls) arranged adjacent to the conductive cell structure layer such that the conductive cell structure layer is sandwiched between the charge storing insulator layer and the insulating cell structure layer.
  • the insulating cell structure layer comprising a layer of a structure comprising an array of hollow cells formed between elongated walls may be an insulating honeycomb layer.
  • the conductive cell structure layer may comprise a plurality of annular conducting regions electrically isolated from each other.
  • the annular conducting regions may be circular shaped.
  • the conductive cell structure layer may further comprise a central conducting region electrically isolated from the annular conducting regions.
  • the central conducting region may be a circular disk shaped region.
  • the electrode assembly may be for an electrostatic loudspeaker that comprises a diaphragm that comprises at least one insulating layer and at least one conducting layer.
  • the conductive cell structure layer may comprise insulating cell structure that has been coated with electrically conductive coating.
  • the charge storing insulator layer may be a charge storing insulator mesh.
  • the charge storing insulator mesh may comprise a multi-stranded thread.
  • the charge storing insulator layer may be a charge storing insulator honeycomb layer.
  • the charge storing insulator layer may be made of nylon.
  • the open cells of the conductive cell structure layer may be systematically aligned relative to the openings of the charge storing insulator layer.
  • the open cells of the conductive cell structure layer may be systematically aligned relative to the open cells of the insulating cell structure layer.
  • the electrode assembly may further comprise an electrical connection assembly for connecting to the annular conducting regions of the electrode assembly, wherein the electrical connection assembly comprises at least one electrical contact for each annular conducting region of the conductive cell structure layer.
  • the electrical contact of at least one annular conducting region may be located in a localised cavity within the annular conducting region of the conductive cell structure layer.
  • Non-conductive adhesive may be provided to contribute to the fixing of the location of the electrical contact within the localised cavity within the annular conducting region of the conductive cell structure layer.
  • Conductive adhesive may be provided to contribute to the fixing of the location of the of the electrical contact within the localised cavity within the annular conducting region of the conductive cell structure layer and to contribute to the electrical connection between the electrical contact and the annular conducting region of the conductive cell structure layer.
  • the electrical contact may be a hollow tube
  • the electrical contact may be spring loaded.
  • the electrical contact may be shaped to extend into the inside of an individual cell of the conductive cell structure layer.
  • the electrical connection assembly may further comprise a strip of circuit board comprising a plurality of conducting tracks, each conducting track extending to a respective annular conducting region.
  • the strip of circuit board may be positioned in a localised strip-shaped cavity between the insulating cell structure layer and the conductive cell structure layer. Each electrical contact may be soldered to the respective conducting track of the strip of circuit board.
  • the invention provides an electrostatic loudspeaker, comprising a diaphragm positioned between, and spaced apart from, two electrode assemblies according to any of the above aspects, one of the electrode assemblies being positioned facing one side of the diaphragm and the other of the electrode assemblies positioned facing the other side of the diaphragm, wherein the electrode assemblies each comprise electrodes provided in the form of a conductive cell structure layer.
  • the electrostatic loudspeaker may further comprise a drive circuit comprising constant impedance delay line circuits.
  • the electrostatic loudspeaker may further comprise a drive circuit comprising two delay line circuits, each delay line circuit arranged to drive a respective one of the two electrode assemblies, each delay line circuit comprising a plurality of sections, each section arranged to drive a respective one of the annular conducting regions of the electrode assembly; wherein each section comprising an inductor; and for each section, an output connection with the corresponding respective annular conducting region of the electrode assembly is taken from a tapped point of the inductor of the section of the delay line circuit, the tapped point being at a point on the inductor that is between the two ends of the inductor and that is remote from both ends of the inductor i.e. the tapped point is at a position other than either end of the inductor windings.
  • the tapped point of the inductor may be a centre tapped point.
  • One or more of the sections may further comprise a capacitor.
  • the electrostatic loudspeaker may further comprise a termination impedance.
  • Each section of the delay line circuit may be implemented so as to have an equivalent circuit substantially as shown in Figure 8, where Cn may be zero in at one or more of or the sections.
  • the inductor in at least one of the sections of a first of the two delay line circuits may share a common core with the inductor of its corresponding section in the other of the two delay line circuits.
  • the inductors in all of the sections of the first of the two delay line circuits may each share a common core with the inductors of its corresponding sections in the other of the two delay line circuits.
  • the invention provides an electrostatic loudspeaker, comprising a diaphragm positioned between, and spaced apart from, two electrode assemblies, one of the electrode assemblies being positioned facing one side of the diaphragm and the other of the electrode assemblies positioned facing the other side of the diaphragm, wherein the electrode assemblies each comprise electrodes provided in the form of a conductive cell structure layer.
  • the conductive cell structure layer may comprise a plurality of annular conducting regions electrically isolated from each other.
  • the annular conducting regions may be circular shaped.
  • the conductive cell structure layer may further comprise a central conducting region electrically isolated from the annular conducting regions.
  • the central conducting region may be a circular disk shaped region.
  • the electrostatic loudspeaker may further comprise an electrical connection assembly for connecting to the annular conducting regions of the electrode assembly, wherein the electrical connection assembly comprises at least one electrical contact for each annular conducting region of the conductive cell structure layer.
  • the electrical contact of at least one annular conducting region may be located in a localised cavity within the annular conducting region of the conductive cell structure layer.
  • Non-conductive adhesive may be provided to contribute to the fixing of the location of the electrical contact within the localised cavity within the annular conducting region of the conductive cell structure layer.
  • Conductive adhesive may be provided to contribute to the fixing of the location of the of the electrical contact within the localised cavity within the annular conducting region of the conductive cell structure layer and to contribute to the electrical connection between the electrical contact and the annular conducting region of the conductive cell structure layer.
  • the electrical contact may be a hollow tube
  • the electrical contact may be spring loaded.
  • the electrical contact may be shaped to extend into the inside of an individual cell of the conductive cell structure layer.
  • the electrical connection assembly may further comprise a strip of circuit board comprising a plurality of conducting tracks, each conducting track extending to a respective annular conducting region.
  • the strip of circuit board may be positioned in a localised strip-shaped cavity between the insulating cell structure layer and the conducting honeycomb layer.
  • Each electrical contact may be soldered to the respective conducting track of the strip of circuit board.
  • the invention provides a delay line circuit for driving an electrostatic loudspeaker electrode comprising one or more annular conducting regions electrically isolated from each other; the delay line circuit comprising a plurality of sections, each section arranged to drive a respective one of the annular conducting regions of the electrode; and each section comprising an inductor; wherein for each section, an output connection with the corresponding respective annular conducting region of the electrode is taken from a tapped point of the inductor of the section of the delay line circuit, the tapped point being at a point on the inductor that is between the two ends of the inductor and that is remote from both ends of the inductor i.e. the tapped point is at a position other than either end of the inductor windings.
  • the tapped point of the inductor may be a centre tapped point.
  • One or more of the sections may further comprise a capacitor.
  • the delay line circuit may further comprise a termination impedance.
  • each section of the delay line circuit may be implemented so as to have an equivalent circuit substantially as shown in Figure 8, where C n may be zero in one or more of or the sections.
  • the invention provides a drive circuit for driving an electrostatic loudspeaker, wherein the loudspeaker comprises two electrodes, the two electrodes spaced apart from, and positioned respectively to either side of, a diaphragm, and each electrode comprises one or more annular conducting regions electrically isolated from each other; the drive circuit comprising two delay line circuits according to any of the above aspects, each delay line circuit arranged to drive a respective one of the two electrodes.
  • the inductor in at least one of the sections of a first of the two delay line circuits may share a common core with the inductor of its corresponding section in the other of the two delay line circuits.
  • the inductors in all of the sections of the first of the two delay line circuits may each share a common core with the inductors of its corresponding sections in the other of the two delay line circuits.
  • Each electrode may further comprise a central conducting region electrically isolated from the annular conducting regions.
  • the invention provides an electrostatic loudspeaker comprising a delay line circuit according to any of the above aspects.
  • the invention provides an electrostatic loudspeaker comprising a drive circuit according to any of the above aspects.
  • Some or all of the capacitance used in operation of the delay line circuit or circuits may be provided by the capacitance provided by at least some of the annular conducting regions of the electrode or electrodes.
  • the one or more annular conducting regions of the electrodes may be circular in shape.
  • the central conducting region may be a circular disk shaped region.
  • the electrodes may each comprise: a conductive honeycomb layer; and a charge storing insulator layer arranged adjacent to the conductive honeycomb layer.
  • the electrodes may each further comprise an insulating honeycomb layer arranged adjacent to the conductive honeycomb layer such that the conductive honeycomb layer is sandwiched between the charge storing insulator layer and the insulating honeycomb layer.
  • the conductive honeycomb layer may comprise insulating honeycomb that has been coated with electrically conductive coating.
  • the charge storing insulator layer may be a charge storing insulator mesh.
  • the charge storing insulator mesh may be a nylon mesh.
  • the charge storing insulator mesh may comprise a multi-stranded thread.
  • the open cells of the conductive honeycomb layer may be systematically aligned relative to the openings of the charge storing insulator layer.
  • the open cells of the conductive honeycomb layer may be systematically aligned relative to the open cells of the insulating honeycomb layer.
  • the invention provides a drive circuit for driving an electrostatic loudspeaker, wherein the loudspeaker comprises an electrode positioned to either side of, and spaced apart from, a diaphragm, and each electrode comprises one or more annular conducting regions electrically isolated from each other; the drive circuit comprising two delay line circuits, each delay line circuit arranged to drive a respective one of the two electrodes; wherein one or more inductors comprised by a first of the two delay line circuits shares a common core with its corresponding inductor or inductors as comprised by the other of the two delay line circuits.
  • All the inductors comprised by a first of the two delay line circuits may share a common core with its corresponding inductors as comprised by the other of the two delay line circuits.
  • the invention provides an electrostatic loudspeaker comprising a drive circuit according to any of the above aspects.
  • Figure 1 is a schematic cross-sectional illustration (not to scale) of an electrostatic loudspeaker
  • Figure 2 shows a schematic front view (not to scale) of certain features of a conductive honeycomb layer of the electrostatic loudspeaker of Figure 2;
  • Figure 3 is a schematic illustration (not to scale) of two representations both showing the same arrangement of a small area, for illustration purposes, of a charge storing nylon mesh 12 in conjunction with a corresponding small area of a conducting region of a conductive honeycomb layer;
  • Figure 4 is a simplified circuit diagram schematically illustrating a drive circuit and speaker arrangement that may be employed to drive the electrostatic loudspeaker of Figure 1 ;
  • Figure 5 is a schematic illustration (not to scale) showing a geometry of delay path length
  • Figure 6 is a schematic illustration (not to scale) showing partitioning of electrodes into a center disk and N concentric rings, each having its radius ao to aN;
  • Figure 7 is a further illustration of the drive circuit and speaker arrangement of Figure 4, including circuit diagrams of delay line circuits;
  • Figure 8 is an equivalent circuit of a single delay line section
  • Figure 9 is a schematic illustration (not to scale) of a connection arrangement
  • Figure 10 is a schematic illustration (not to scale) showing in cross- section a representative portion of certain layers of the electrostatic loudspeaker of Figure 1 along a radius over which a PCB extends in the arrangement of Figure 9;
  • Figure 1 1 is a schematic illustration (not to scale) showing in cross- section and in more detail a representative portion of certain layers of the electrostatic loudspeaker of Figure 1 along the radius over which the PCB extends in Figure 9 and Figure 10;
  • Figure 12 is a schematic illustration (not to scale) showing a spring contact located under its spring action in a conductive honeycomb layer such that it compresses and locates within or against plural cells of the conductive honeycomb layer thereby making electrical contact with the conductive honeycomb layer;
  • Figure 13 is a schematic illustration (not to scale) showing a spring contact located under its spring action in a conductive honeycomb layer such that it compresses and locates within an individual cell of the conductive honeycomb layer thereby making electrical contact with the inside surface wall of that cell of the conductive honeycomb layer.
  • FIG. 1 is a schematic cross-sectional illustration (not to scale) of a first embodiment of an electrostatic loudspeaker 1 .
  • the electrostatic loudspeaker 1 comprises a diaphragm 2 positioned between, and spaced apart from, two electrode assemblies 4. Between the diaphragm 2 and each electrode assembly 4 is a respective air gap 6.
  • the electrostatic loudspeaker further comprises a support structure 7.
  • the shape of the electrostatic loudspeaker 1 is circular, with the diameter of the active area of the speaker (indicated in Figure 1 by reference numeral 9) approximately 280mm. In other embodiments, other diameters may be employed, for example in the range 30mm to 3m. In further embodiments, shapes other than circular may be employed.
  • the support structure 7 is not included at the top of the Figure and instead its presence is indicated by dotted lines.
  • the separation between the diaphragm 2 and each electrode assembly 4 is approximately 1 mm, i.e. the air gaps 6 are each approximately 1 mm wide. In other embodiments the air gaps 6 may be other sizes, for example in the range 0.1 mm to 10mm.
  • the diaphragm 2 comprises an insulating film 8 coated on one side with a conductive layer 10.
  • the insulating film 8 is a polyester film 8 and the conductive layer 10 is an aluminium layer 10.
  • other film and conductor materials may be used instead.
  • the insulating film 8 may be made of kapton or polyimide
  • the conductive layer 10 may be made of indium tin oxide (ITO), gold or graphite.
  • the insulating film 8 may be coated on both sides with a conductive layer 10, or a conductive layer 10 may be coated on both sides with an insulating film 8, or other combinations of insulating films and conductive layers may be employed.
  • the thickness of the polyester film 8 is 12 m. However this need not be the case, and in other embodiments the film thickness may be other sizes, for example in the range 3 ⁇ to ⁇ ⁇ . In this embodiment the thickness of the aluminium layer 10 is less than 0.5pm. However this need not be the case, and in other embodiments the film thickness may be other sizes, for example in the range of 0.5 ⁇ to 50 ⁇ .
  • the aluminium layer 10 of the diaphragm is electrically coupled to a polarizing voltage supply 21 via a resistor 1 1 .
  • the resistor 1 1 is any appropriate high value resistor.
  • the resistor 1 1 is of resistance 10 ⁇ .
  • each electrode assembly 4 comprises the following layers laminated or otherwise arranged in substantially abutting parallel layers adjacent to each other, in the following order, to each other in the following order, starting with the layer nearest the diaphragm 2: a charge storing insulator layer 12 (which in this embodiment is a charge storing insulating mesh 12), a conductive cell structure layer 14 (which in this embodiment is a conductive honeycomb layer 14, and which may in other embodiments be any other type of conductive cell structure layer 14 comprising a layer of a structure comprising an array of hollow cells formed between elongated walls), an insulating cell structure layer 16 (which in this embodiment is an insulating honeycomb layer 16, and which may in other embodiments be any other type of insulating cell structure layer 16 comprising a layer of a structure comprising an array of hollow cells formed between elongated walls), and a conducting mesh 18.
  • a charge storing insulator layer 12 which in this embodiment is a charge storing insulating mesh 12
  • a conductive cell structure layer 14 which in
  • the layers may be attached or otherwise fixedly located with each other such that the charge storing insulating mesh 12 abuts a first planar side of the conductive honeycomb layer 14 and the insulating honeycomb layer 16 abuts the other side of the conductive honeycomb layer 14. It will be understood that in some embodiments such arrangements may further comprise relatively thin layers of other materials, for example adhesives, or localised air gaps, such that the layers may not literally be in direct touching contact but are nevertheless functionally abutted to each other.
  • the charge storing insulating mesh 12 provides a layer of effective thickness approximately equal to 0.1 mm (this thickness is indicated in Figure 1 by reference numeral 13). Further details of the charge storing insulating mesh 12 are described later below with reference to Figures 2 and 3.
  • the conductive honeycomb layer 14 is of approximate thickness 2mm (this thickness is indicated in Figure 1 by reference numeral 15).
  • the insulating honeycomb layer 16 is of approximate thickness 8mm (this thickness is indicated in Figure 1 by reference numeral 17).
  • the conducting mesh 18 is of approximate thickness
  • the charge storing insulating mesh 12 is a charge storing nylon mesh 12
  • the conductive honeycomb layer 14 comprises polycarbonate honeycomb structure that has been coated with electrically conductive paint
  • the insulating honeycomb layer 16 comprises a polycarbonate honeycomb structure
  • the conducting mesh 18 is a steel mesh 18.
  • the charge storing insulating mesh 12 may be made of any suitable charge storing insulating material, for example paper or polyester
  • the conducting mesh 18 may be made of any electrically conductive mesh, for example aluminium, steel or carbon fibre etc.
  • honeycomb material is generally available, and is typically produced for use in, amongst others, the space, aerospace and automotive industries.
  • honeycomb material is characterised by having a very open cellular structure, which gives very strong compression strength in the direction of the thickness of the honeycomb structure (but not in the direction across the layer) despite its low weight and material bulk.
  • one advantage of the use of honeycomb structure is that its strength, flatness and openness advantageously allows the membrane to be held under tension whilst allowing air to move with little hindrance.
  • One advantageous reason the air can move with little hindrance is that the honeycomb has a very open structure.
  • one cell structure that may be used is a structure in which cells of the structure tessellate such that the cells do not overlap and there are no gaps between adjacent cells (other than the walls of the cells formed by the material of the structure), with adjacent cells being defined by common walls.
  • different cells may have different cross-sectional shapes and/or cross-sectional areas, and in some other examples all the cells may have the same cross-sectional shapes and/or cross-sectional areas.
  • honeycomb material as such is a preferred option.
  • any appropriate honeycomb materials may be used, including, for example, the following: honeycombs made from a variety of materials such as paper (Nomex), fibreglass (Hexcel), aluminium (for conductive stators), Kevlar, carbon fibre or plastic such as polypropylene or polycarbonate (Coretex PC2.5).
  • honeycombs made from a variety of materials such as paper (Nomex), fibreglass (Hexcel), aluminium (for conductive stators), Kevlar, carbon fibre or plastic such as polypropylene or polycarbonate (Coretex PC2.5).
  • Any appropriate cell structure i.e. cross-sectional shape of each cell of the honeycomb
  • One typical honeycomb cell structure for example, is octagonal.
  • Another typical honeycomb cell structure for example, is one in which circles are abutted to each other. This honeycomb material is typically manufactured by cylindrical extruded tubes being bonded together to form the structure. In the particular embodiments described above, this abutted circles structure is employed, as will be described in more detail later
  • FIG. 1 shows a schematic front view (not to scale) of certain features of the conductive honeycomb layer 14.
  • the same reference numerals are used to indicate the same features as in Figure 1 (this is also the case for other Figures when they use the same reference numerals as each other).
  • the conductive honeycomb layer 14 comprises a central conductive region 20 and a plurality of annular conducting rings 22 arranged concentric to each other and to the central conductive region 20.
  • N For convenience, in Figures 1 and 2 only a first annular conducting ring 22-1 and an Nth annular conducting ring 22-N are shown.
  • any other rings i.e. 2 nd to N-1 , when N>2, are not shown.
  • N 6, i.e. the conductive honeycomb layer 14 comprises a central conducting region (20) and first (22-1 ), second (not shown), third (not shown), fourth (not shown), fifth (not shown) and sixth (22-N) annular conducting rings. Further details of the way in which the number of rings may preferably be selected in some embodiments are described in more detail later below as part of the description accompanying Figures 6 to 9.
  • Respective electrically isolating gaps 26, also in annular form, are provided between the central conducting region 20 and the first annular conducting ring 22-1 , and between each adjacent pair of consecutive annular conducting rings 22-1 to 22-N.
  • the central conductive region 20 and each annular conducting ring 22-1 to 22-N comprises a separate piece of the earlier mentioned polycarbonate honeycomb structure that has been coated with electrically conductive coating, for example with electrically conductive paint.
  • electrically conductive coating for example with electrically conductive paint.
  • other appropriate method other than coating may be used to to render the central conductive region 20 and each annular conducting ring 22-1 to 22-N conductive.
  • the separate pieces have been individually attached, in their respective positions, to the surface of the insulating honeycomb layer 16 that in this embodiment comprises a single block of the earlier mentioned polycarbonate honeycomb structure.
  • the individually attached central conductive region 20 and plural annular conducting rings 22-1 to 22-N have been attached in positions spaced apart so as to provide the electrically isolating gaps 26 there between.
  • the electrically isolating gaps 26 are air gaps. However, this need not be the case, and in other embodiments electrically isolating material other than air may be provided in the gaps. This may include structures that include air gaps within their structures. For example, in other embodiments the electrically isolating gaps 26 may be in the form of regions of insulating honeycomb structure.
  • the central conducting region 20 and/or some or all of the annular conducting rings 22-1 to 22-N with corresponding electrically isolating gaps 26 therebetween may be provided by painting only those regions of a piece of insulating honeycomb structure with conducting paint (or by using any other appropriate method other than painting to rendering those regions conductive) that are to form the conducting regions 20 and 22-1 to 22-N and leaving other regions unpainted to provide the electrically isolating gaps 26.
  • one or more of the annular conducting rings may be formed by two or more segments that are not physically joined but which are nevertheless electrically connected together.
  • FIG. 3 is a schematic illustration (not to scale) of two representations both showing the same arrangement of a small area, for illustration purposes, of the charge storing nylon mesh 12 in conjunction with a corresponding small area of a conducting region (i.e. the central conducting region 20 or one of the annular conducting rings 22-1 to 22-N) of the conductive honeycomb layer 14.
  • the first representation 40 the charge storing nylon mesh 12 is shown in full lines whereas the structure of the conductive honeycomb layer 14 is shown in dotted lines.
  • the structure of the conductive honeycomb layer 14 is shown in full lines whereas the charge storing nylon mesh 12 is shown in dotted lines. It is to be appreciated that both representations are showing the same thing, but for visual clarity the two representations have been provided.
  • the charge storing nylon mesh 12 comprises multi- stranded nylon thread.
  • the charge storing nylon mesh 12 advantageously tends to evenly distribute and store the electrostatic charge whilst reducing/preventing arc between the stators and the conductive membrane.
  • the use of multi- stranded thread tends to provide improved charge storage.
  • single-stranded thread may be employed instead.
  • the ratio of the open area of the nylon 12 grid to its total area is approximately 0.625 i.e. it is very "open".
  • other dimensions and shapes may be used, for example square-shaped grids.
  • the conducting honeycomb layer 14 comprises a honeycomb structure with a uniform abutting-circles cell structure.
  • This honeycomb material is typically manufactured by cylindrical extruded tubes being bonded together (e.g. with an adhesive) to form the structure.
  • each circle i.e. the cross-sectional shape of each cylindrical tube
  • has a diameter 2.5mm (this diameter is indicated in Figure 3 by reference numeral 1 14).
  • the ratio of the open area of the conducting honeycomb layer 14 to its total area is approximately 0.92 i.e. it is very "open".
  • other dimensions may be used, for example honeycomb material of circular cell structure with diameter between 2.5mm and 12mm and openness of approximately 0.8.
  • the grid structure of the charge storing nylon mesh 12 is randomly overlaid relative to the hexagonal cell structure of the conducting honeycomb layer 14.
  • the mesh and cell sizes and/or their relative positions may be arranged to overlap in a systematically aligned or partially aligned manner, thereby giving a larger degree of preservation of the overall extent of openness.
  • the insulating honeycomb layer 16 comprises a honeycomb structure with a uniform abutting-circles cell structure that is the same as that of the conducting honeycomb layer 14.
  • the two honeycomb layers may have different respective cell structures, including different cell shapes and/or dimensions.
  • the abutting-circles cell structure of the conducting honeycomb layer 14 is randomly overlaid relative to the abutting-circles cell structure of the insulating honeycomb layer 16.
  • the cell structures may be arranged to overlap in a systematically aligned or partially aligned manner, thereby giving a larger degree of preservation of the overall extent of openness.
  • the use of a honeycomb structure tends to advantageously provide a very lightweight design. This is also the case for the use of the nylon mesh or other insulating mesh. Furthermore, these benefits are even more significant when considered in combination for the honeycomb and the mesh.
  • the aluminium mesh 18 comprises aluminium mesh or grill provided in the form of an aluminium sheet having circular perforations of approximately 1.5mm diameter in it.
  • the ratio of the open area of the aluminium mesh grid to its total area is approximately 0.8 i.e. it is very "open".
  • aluminium mesh 18 mechanically strengthens and protects the electrostatic loudspeaker 1 , for example from impacts.
  • materials such as the aluminium mesh 18 are used as a connection to earth as a safety function or alternatively non- conductive layers may be used thereby providing a double electrical insulation safety function instead of earth connection.
  • the aluminium mesh 18 may be omitted.
  • the aluminium mesh 18 may be omitted and replaced with other elements for providing some or all of the safety and/or protection functions.
  • the diaphragm 2 acts as an electrical conductor and is connected to the polarizing voltage supply 21 via the high value resistor 1 1 .
  • the conductive honeycomb layers 14 act as electrodes or "stators". High voltage driving signals are applied to the conductive honeycomb layers 14. This alters the high voltage electric fields between the conductive honeycomb layers 14 and the diaphragm 2.
  • the alteration of the high voltage fields causes the diaphragm to move and displace air according to the driving signals producing sound waves.
  • the overall structure of the electrostatic loudspeaker 1 allows air to move freely within its structure and hence the moving air forming the sound waves is transmitted out of the electrostatic loudspeaker 1 .
  • the nylon mesh layer 12 serves as a charge storing insulator layer, and more particularly in this embodiment as a charge storing insulator mesh.
  • the charge storing insulating mesh 12 may be made of any suitable charge storing insulating material, for example paper or polyester.
  • the charge storing insulator layer may be provided in forms other than a mesh as such, including preferably arrangements that nevertheless have large degrees of openness.
  • the charge storing insulator layer 12 may be provided in the form of a charge storing insulating honeycomb layer, where the charge storing insulating honeycomb layer is made of a suitable charge storing insulator material, for example nylon, paper or polyester.
  • the charge storing insulating honeycomb layer may advantageously, in terms of construction efficiency and/or improving extent of openness to airflow, have the same cell shape and/or cell shape dimensions as either or both of the conducting honeycomb layer 14 and the insulating honeycomb layer 16, and/or have the same thickness as the conductive honeycomb layer 14.
  • the open cells of the charge storing insulating honeycomb layer may advantageously be systematically aligned relative to the cells of the conducting honeycomb layer 14 and/or the cells of the insulating honeycomb layer 16.
  • FIG. 4 is a simplified circuit diagram schematically illustrating an embodiment of a drive circuit and speaker arrangement 50 that may be employed to drive the above described electrostatic loudspeaker 1 . It will be appreciated that in other embodiments any other appropriate type of drive circuits and apparatus may be used instead.
  • the drive circuit comprises a pair of delay line circuits 60. Each of the two delay line circuits 60 drives a respective one of the two electrode assemblies 4 of the electrostatic loudspeaker 1 .
  • the central conducting region 20 and the annular conducting rings 22-1 to 22-N of the conductive honeycomb layer 14 are fed separately, and in particular the annular conducting rings 22-1 to 22-N are fed from separate output points of a delay line in order to provide that sound emanates from the centre of the diaphragm first and from the edge last in order to provide a virtual dipole point source, thereby tending to reduce directional non-uniformity at high frequencies where the wavelength of sound is small compared to the diameter of the diaphragm 2.
  • the delay line circuits 60 are of a design that that the present inventors have termed a "constant-impedance delay line". Further details of the delay line circuits 60 are described later below with reference to Figures 5 to 8. However, in other embodiments, other conventional delay lines may be used.
  • the inductors in the two delay line circuits 60 share the same cores, thereby advantageously reducing by half the number of wound components that are used.
  • the some or all of the cores need not be shared.
  • the drive circuit and speaker arrangement 50 comprises two delay lines 60, each driven by a voltage source e m in conjunction with the polarizing voltage supply 21 (via the high value resistor 1 1 ).
  • the polarizing supply provides gain.
  • the optimum voltage is approximately that of the peak signal voltage. Note that these sources are in opposite phase in order to balance out even-order harmonic distortion in the loudspeaker.
  • the junction of the two sources is connected to the conducting layer 10 of the diaphragm 2 via the polarizing voltage supply 21 and the resistor 1 1 .
  • the two anti-phase voltages are taken from the centre- tapped secondary winding of a stepping-up transformer, where the centre tap is connected to the polarizing supply.
  • the tapped point need not be at the centre winding of the windings of the inductor, instead the tap point may be at any point along any of the windings of the inductor other than the at the end of the end winding, i.e. the tap point may be at any winding of the windings of the inductor as long as it is not also at the end of the inductor, i.e.
  • the tapped point may be at any point on the inductor that is between the two ends of the inductor and that is remote from both ends of the inductor i.e. in other embodiments the tapped point may be at any point other than either end of the inductor windings.
  • the anti-phase voltages could be provided by the outputs from a high-voltage bridge amplifier in which case the polarizing supply could be created automatically by connecting the conducting layer 10 of the diaphragm 2 (via the resistor 1 1 ) to either the positive or negative rail of the amplifier power supply.
  • the polarizing voltage would be half the supply voltage.
  • the central conducting region 20 is fed directly from the voltage source without any delay so that sound emanates from that region first.
  • the annular conducting rings 22-1 to 22-N are fed from tappings along the delay lines 60 so that the delay increases progressively from the first ring 22-1 to the outermost ring 22-N.
  • Figures 5 to 8 provide more details of the "constant- impedance delay line” design of the delay line circuits 60. Also, in the following account accompanying Figures 5 to 8, further details will be described of how the component values of the delay line circuits 60, and related thereto the number N of conducting annular rings 22-1 to 22-N, and the dimensions of the annular conducting rings 22-1 to 22-N and the dimensions of the central conducting region 20, may be determined or selected.
  • FIG. 5 is a schematic illustration (not to scale) showing geometry of delay path length.
  • the electrostatic loudspeaker has a flat circular diaphragm of radius a. If the whole diaphragm were driven in unison, it would produce a narrow polar pattern at frequencies where the wavelength is smaller than the diaphragm (in other words all frequencies above 1 kHz in the case of a 15 cm radius).
  • a delay line has been employed in order to simulate a point source at some distance behind the diaphragm.
  • the diaphragm is finite in size and would therefore produce irregularities in the on-axis and polar responses.
  • the delay line is intentionally lossy, rather like the windowing function in fast Fourier transforms.
  • the directivity pattern is limited to the angle of the cone whose base is the diaphragm and apex is the "ghost" point source behind the diaphragm.
  • the present inventors have realised that ideally one would wish the flat diaphragm to behave like a sphere oscillating back and forth, in which case it would produce the same "figure-of-8" pattern at all frequencies.
  • the present inventors have realised this can be achieved by applying a delay to each point along its radius which increases with distance from the centre. Imagine a sphere of radius a behind the circular diaphragm which touches it at the centre.
  • the ideal amount of delay at each point on the diaphragm is the time taken for sound to travel axially from the each point on the nearest side of the sphere to the corres onding point on the back of the diaphragm. It is the distance d— in Figure 5.
  • FIG. 6 is a schematic illustration (not to scale) showing the partitioning of the electrodes into a centre disk and N concentric rings, each having its radius ao to aN.
  • FIG. 7 is a further illustration of the drive circuit and speaker arrangement 50, including circuit diagrams of the delay line circuits 60 of this embodiment.
  • Each delay line circuit 60 has been implemented by the present inventors in the form of a "constant-impedance" type made up of cascaded sections of all-pass filters, each comprising an inductor Li, I_2. . . LN with a respective capacitor Cci, CC2, ... CCN.
  • the output is taken from the tapped point of the respective inductor Li, l_2. . . LN (i.e. a tapped point that is somewhere along the inductor, i.e.
  • the delay line circuit 60 further comprises a termination impedance RT. Hence, the consecutive sections do not attenuate the signal but instead simply provide an increasing phase shift.
  • the capacitors CEI , ... CE/V are the native capacitances of the rings and
  • the CEO is the capacitance of the centre disk.
  • the capacitors Cci, CC2, ... CCN are added shunt capacitors.
  • the added shunt capacitors Cci, CC2, ... CCN may preferably be set to zero except in the case of the outermost rings where the delay increases rapidly.
  • the termination impedance RT is the characteristic impedance of the delay line and is seen at the input (in parallel with the small capacitance of the centre ring CEO).
  • Each respective section output is coupled to its respective annular conducting ring 22-1 , ...22-N.
  • the present inventors have surprisingly provided a design of a delay line circuit in which some of the capacitance in the delay line circuit is provided by the capacitance provided by some of the annular conducting rings. This tends to advantageously provide that the energy is used to drive the stator ring capacitance and hence move the diaphragm to produce sound, rather than to drive a component capacitor.
  • the present inventors have realised it would be desirable to employ a constant-impedance type circuit.
  • the outputs would be taken from the junctions between each of the inductors, i.e. from points at the end of the inductors.
  • the capacitive load of the electrode rings would then prevent it from being a constant (resistive) impedance line.
  • the present inventors have designed the circuit such that the electrode rings provide the capacitance needed for the delay line except in the case of the outermost rings where the widths of the rings would need to be overly large in order to provide the rapidly increasing delay.
  • extra “shunt" capacitors are added.
  • a disadvantage of this configuration is that at some frequency the output of each ring will roll-off with a 1 st -order slope. However, this will still typically be less of a disadvantage than is experienced with conventional approaches for example with known lossy delay lines where the first ring has a 1 st -order roll-off, the second ring 2 nd -order, the third ring 3 rd -order and so on.
  • the patterns of such conventional arrangements are typically very narrow above 4 kHz.
  • simulations show that the arrangement of the present embodiment tends to produce a wide pattern up to the highest frequencies with a moderately flat on-axis response.
  • the starting values for the calculation are the termination resistance RT, the shunt capacitor values and the radius ao of the centre disk. From these, the radii of the rings and the inductor values are calculated to give the desired delay to each ring. If we arrive at impractical values (e.g. the diameter of the outer ring is greater than that of the diaphragm) we have to re-run the calculation with different starting values. In order to increase or maximize efficiency, we increase or maximize Rrwhile decreasing or minimizing the shunt capacitor values.
  • the capacitors CEH are the native capacitances of the electrostatic rings (between the diaphragm 2 and each annular conducting ring 22).
  • the capacitance of the n th ring is given by r S ' (1 )
  • n th path-length z n is related to the time delay T n of n th section by
  • the time delay T n per section is defined by
  • Equation (4 ) and (9 ) we solve numerically for a n .
  • Ccn In order to increase or maximize efficiency, we preferably set Ccn as close to zero as possible so as not to bypass the rings. However, the delay per section increases towards the rim which tends to increase Cn (and Ln) for a given RT value which would in turn tend to increase the widths of the rings whereas we preferably keep the rings as narrow as possible in order to resolve the rapid increase in delay towards the rim. Hence we will preferably make all of Ccn zero except for CC(N - I> and CCN. When solving for a n it is preferable to ensure that
  • each section will have a 6dB/octave roll-off starting at the frequency
  • the tapped coil is shown as an inductor across the primary of an ideal transformer. At low frequencies, the capacitor is open circuit and the inductor shorts the primary of the transformer. Hence the circuit looks like a direct connection between the input and output and there is little phase shift. At high frequencies the opposite is true.
  • the capacitor shorts the lower end of the transformer primary to ground and the inductor is open circuit. Hence the transformer inverts the signal so that there is a 180° phase shift. In between the low and high frequencies, the phase shift is negative and varies between 0 and -180°. At the natural frequency ⁇ ⁇ it is -90°.
  • Each delay section is described by the transmission matrix
  • the first section has no inductor and is simply given by
  • the radiated sound pressure is simply the sum of the sound radiated from each ring source.
  • each ring we treat each ring as a pure pressure source.
  • the membrane we assume the membrane to have zero mass and to be perfectly flexible. Also it is assumed to be freely suspended instead of clamped at the rim.
  • the following equation for the far-field pressure is derived in the same way as that for a resilient disk in free space on page 563 of "Acoustics: Sound Fields and Transducers" by Leo Beranek and Tim Mellow.
  • D(9) is the directivity function given by
  • the polarizing voltage Ep should also be as large as possible without causing spark-over in accordance with Paschen's law. In order to avoid the diaphragm being attracted towards one or other of the electrodes, there needs to be sufficient tension within the diaphragm. However, too much tension will attenuate the bass response. Furthermore, the membrane must be thick enough to withstand this tension but not so thick as to produce a premature high-frequency roll-off due to excessive moving mass. In preferred designs, the moving mass due to the radiation load should be considerably greater than that due to the membrane.
  • the number of rings is preferably chosen such as to keep the width of each ring smaller than the wavelength of sound over the working frequency range of the loudspeaker. Otherwise a poor directivity pattern with excessive lobing will be produced.
  • the average width of each ring will be 15.5mm (after allowing for a 2mm gap between adjacent rings), which should be fine up to 20kHz where the
  • wavelength is 17.2mm.
  • the widths of the individual rings are determined according the procedure described in the paragraph following Eq. (9 ).
  • the capacitance of each ring is given by Eq. (1 ) and the inductance of each delay section by Eq. (11 ).
  • Center disk 70 mm diameter.
  • the calculated component values for each section of the delay line are shown in Table 1 .
  • the total delay of the line is 250 ⁇ .
  • Table 1 Component values, time delays and cut-off frequencies for each section.
  • the physical electric connections between the delay line circuits 60 and the central conducting region 20 and annular conducting rings 22 of the conductive honeycomb layer 14 may be implemented in any appropriate manner. In some embodiments (i.e. any of the above described embodiments may be implemented with the following connection arrangement) they are implemented as will now be described with reference to Figures 9 to 1 1 .
  • FIG 9 is a schematic illustration (not to scale) of the connection arrangement 148 of these embodiments.
  • the electrostatic loudspeaker further includes a printed circuit board (PCB) 150, in the form of a strip that radially extends over the central conducting region 20 and annular conducting rings 22-1 to 22-N of the conductive honeycomb layer 14.
  • PCB 150 has a width (indicated in Figure 9 by reference numeral 152) of only 10mm, thereby limiting the extent to which the PCB 150 interferes with air flow. In other embodiments other widths may be used.
  • the PCB strip may extends over the central conducting region 20 and annular conducting rings 22-1 to 22-N of the conductive honeycomb layer 14 in directions other than radially, including other straight direction or even other direction that are not straight.
  • a respective electrical contact 160 is provided on the PCB 150 for each respective central conducting region 20/annular conducting ring 22-1 to 22-N.
  • additional contacts may be provided at each respective central conducting region 20/annular conducting ring 22-1 to 22-N to provide redundancy. These may be provided along the same radius as each first respective contact, or may alternatively or additionally be provided on a different radius extension of the PCB 150 or a separate PCB 150.
  • the outputs from the delay line circuits are electrically connected to tracks on the PCB 150 in conventional fashion. Also in conventional fashion respective electrical connections to the contact 160 located at the corresponding conductive region/ring of the conductive honeycomb layer 14 are provided by patterned conducting tracks on the PCB 150. Accordingly, a simple and efficient arrangement for locating connections at the appropriate conductive region/rings is provided.
  • the contacts 160 are made of brass and are in the form of hollow tubes.
  • hollow tubes By the use of hollow tubes, the use of adhesives as will described later below results in particularly effective bonding and electrical connection, especially bearing in mind the conventional difficulties of electrically connecting to a honeycomb structure.
  • any other appropriate conducting material and/or shape may be used.
  • the contacts 160 may be physically and electrically connected to the conductive region/ring of the conductive honeycomb layer 14 in any appropriate manner. In these embodiments, a preferred technique is used, as will now be described with reference to Figures 10 and 1 1.
  • Figure 10 is a schematic illustration (not to scale) showing in cross- section a representative portion of certain layers of the electrostatic loudspeaker 1 extending along the radial direction over which the PCB 150 extends in Figure 9. Shown in Figure 10 in cross-section are the insulating honeycomb layer 16, the PCB 150, two (by way of example) of the contacts 160, and the conducting honeycomb layer 14. It is noted that for convenience the cross-section is drawn at right angles on the page relative to the corresponding orientation that was employed in Figure 1 . Also shown in Figure 10 are localised gaps 165 that are provided in the conducting honeycomb layer 14, i.e. localised regions which only extend circumferentially a small extent contained within the width of the strip of the PCB 150.
  • these localised gaps need only be of sufficient size to accommodate the contacts 160, and the contacts should not protrude above the top surface line of the conducting honeycomb, otherwise they may cause the membrane to short (arc) against the stator preventing the loudspeaker from reproducing sound. It is noted these localised gaps 165 should not be confused with the previously described isolating gaps 26 also shown in Figure 10 and that were also shown previously in Figure 2 and as described earlier extend around the whole circumference of a respective annular ring for the purpose of defining and electrically separating adjacent annular conducting rings. As shown schematically in Figure 10, the PCB 150 is sandwiched between the insulating honeycomb layer 16 and the conducting honeycomb layer 14. This provides a structurally sound, accurately aligned, and easy to manufacture arrangement. The contacts are furthermore conveniently and safely located within the localised gaps 165 of the conducting honeycomb layer 14.
  • a structurally strong and flat combined physical layer consisting of the insulating honeycomb layer 16 and the PCB 150 is provided.
  • One way in which this may be implemented is that a top part of the insulating honeycomb layer 16 is cut away to provide a void or groove in which the PCB 150 may be positioned.
  • the void or groove only needs to be wide enough and long enough to accommodate the PCB 150, i.e. the void or groove is preferably approximately the same width and length as the extent to which the PCB 150 extends over the insulating honeycomb layer 16, and also has a depth of approximately the same size as the thickness of the PCB 150. This then provides a structurally strong and flat combined physical layer consisting of the insulating honeycomb layer 16 and the PCB 150.
  • FIG. 1 1 is a schematic illustration (not to scale) showing in cross- section and in more detail a representative portion of certain layers of the electrostatic loudspeaker 1 along the radial direction along which the PCB 150 extends in Figure 9 and that was shown in Figure 10.
  • Figure 1 1 shows again the PCB 150 and the conductive honeycomb layer 14, but for convenience does not show the insulating honeycomb layer 16.
  • the contact 160 is physically and electrically connected to the PCB 150 in conventional fashion by virtue of being soldered to the PCB 150 at solder joints 170.
  • the contact 160 is surface mounted to the PCB 150, but this need not be the case and in other embodiments through-hole connection may be employed.
  • a non-conductive adhesive 180 is applied between the contact 160 and PCB 150 to further physically secure their connection.
  • a conductive adhesive 185 is applied between the contact 160 and the conductive honeycomb layer 14 to further physically secure the contact in the localised gap 165 and additionally to improve or provide electrical connection between the contact 160 and the conductive honeycomb layer 14.
  • non-conductive adhesive 180 and a conductive adhesive 185 a particular effective combination of electrical connection and strength is achieved (non-conducting adhesives are typically stronger than conductive adhesives). However, in other embodiments only conductive adhesive may be used. In yet further embodiments, if sufficient direct electrical connection is provided between the contact 160 and the conductive honeycomb layer 14 by virtue of physical contact between the contact 160 and the conductive honeycomb layer 14 (i.e. the contact 160 fits snugly into the localised gap 165 such that it touches the side walls of the localised gap 165), then only non-conductive adhesive may be used, or indeed no adhesives. For example, the contacts 160 may be spring loaded.
  • the contacts may be spring loaded and of a shape that allows them to extend into the inside of individual cells of the conductive honeycomb layer 14, or otherwise into the body of the conductive honeycomb layer 14, thereby providing efficient electrical contact.
  • such contacts are employed in arrangements other than ones where they are located on a PCB strip.
  • such contacts offer embodiments of ways in which electrical contact can be made to the conductive honeycomb layer 14 irrespective of how the electrical connections are made to those contacts from the delay line circuits 60.
  • Figure 12 is a schematic illustration (not to scale) showing a spring contact (made, for example, of brass) located under its spring torsion in the conductive honeycomb layer 14, in particular the dimensions and location of the spring contact 260 being such that it compresses and locates within or against plural cells of the conductive honeycomb layer 14.
  • a spring contact made, for example, of brass
  • Figure 13 is a schematic illustration (not to scale) showing a spring contact 260 (made, for example, of brass) located under its spring torsion in the conductive honeycomb layer 14, in particular the dimensions and location of the spring contact 260 being such that it compresses and locates within an individual cell of the conductive honeycomb layer 14 and thereby makes electrical contact with the inside surface wall of that cell of the conductive honeycomb layer 14 .
  • a spring contact 260 made, for example, of brass
  • the diaphragm and other active elements are circular in shape. However, this need not be the case, and in other embodiments other shapes may be employed.
  • a central (circular) conducting region and concentric annular conducting rings are used.
  • the central conducting region may be omitted with the only conducting regions being annular rings or other shapes of annular regions.
  • the electrodes are divided into the central region and concentric annular regions for the purpose of implementing a delay line approach.
  • no delay line approach is implemented, and in such embodiments there may be no division of the electrodes into a central region and conducting annular rings.
  • mechanical and other advantages of the above described mechanical design for example the use of honeycomb and/or a charge storing insulating mesh such as the nylon mesh will still tend to be realised and of benefit.
  • the above described delay line circuits and approaches may be employed but with conventional electrostatic loudspeakers rather than ones of the particular mechanical components and arrangements described above. This may even include, for example, conventional electrostatic loudspeakers of the type in which the diaphragm is arranged to store charge.
  • some or all of the inductors in the two delay line circuits share the same cores, thereby advantageously reducing by up to half the number of wound components that are used.
  • This aspect may be employed in other embodiments in which conventional delay line circuits are employed, for example in conventional lossy delay line circuits.
  • some or all of the inductors in the two delay line circuits of a given electrostatic loudspeaker share the same cores, thereby reducing by up to half the number of wound components that are used.
  • honeycomb alternatives to honeycomb that tend to present similar advantages, for example low weight and good airflow therethrough, may be used instead of honeycomb as such.
  • honeycomb or the above mentioned alternatives to honeycomb that tend to present similar advantages, for example low weight and good airflow therethrough, may be used as elements in electrostatic loudspeakers of otherwise conventional design, for example even conventional electrostatic loudspeakers of the type in which the diaphragm is arranged to store charge.

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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)

Abstract

Un ensemble d'électrodes (4) pour un haut-parleur électrostatique (1) comprend : une couche conductrice en nid d'abeille (14), qui peut comprendre une pluralité de régions conductrices annulaires (22-1...22-N) et une région conductrice centrale (20) électriquement isolées les unes des autres, et une couche isolante de stockage de charges (12), comprenant par exemple un treillis en nylon (12), disposée adjacente à la couche conductrice en nid d'abeille (14). L'ensemble d'électrodes (4) peut comprendre en outre une couche isolante en nid d'abeille (16) agencée adjacente à la couche conductrice en nid d'abeille (14) de sorte que ladite couche conductrice en nid d'abeille (14) soit prise en sandwich entre la couche isolante de stockage de charges (12) et la couche isolante en nid d'abeille (16). La présente invention concerne également un haut-parleur électrostatique (1) comprenant un diaphragme (2) positionné entre deux ensembles d'électrode (4) et écartés de ces derniers.
PCT/GB2014/053404 2013-11-19 2014-11-18 Haut-parleurs et circuits de commande de haut-parleurs WO2015075432A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB1320407.8A GB2520352A (en) 2013-11-19 2013-11-19 Loudspeakers and loudspeaker drive circuits
GB1320405.2A GB2520351B (en) 2013-11-19 2013-11-19 Loudspeakers and loudspeaker drive circuits
GB1320405.2 2013-11-19
GB1320407.8 2013-11-19

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0549200A1 (fr) * 1991-12-23 1993-06-30 AT&T Corp. Dispositif de transducteurs d'électrètes
JPH07184297A (ja) * 1993-12-22 1995-07-21 Canon Inc 音声入出力装置
US20070124620A1 (en) * 2005-11-29 2007-05-31 Seiko Epson Corporation Capacitive load driving circuit, electrostatic transducer, method of setting circuit constant, ultrasonic speaker, display device, and directional acoustic system
JP2009302744A (ja) * 2008-06-11 2009-12-24 Yamaha Corp 静電型スピーカ
US20100260370A1 (en) * 2009-04-09 2010-10-14 Industrial Technology Research Institute Flat speaker structure

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0549200A1 (fr) * 1991-12-23 1993-06-30 AT&T Corp. Dispositif de transducteurs d'électrètes
JPH07184297A (ja) * 1993-12-22 1995-07-21 Canon Inc 音声入出力装置
US20070124620A1 (en) * 2005-11-29 2007-05-31 Seiko Epson Corporation Capacitive load driving circuit, electrostatic transducer, method of setting circuit constant, ultrasonic speaker, display device, and directional acoustic system
JP2009302744A (ja) * 2008-06-11 2009-12-24 Yamaha Corp 静電型スピーカ
US20100260370A1 (en) * 2009-04-09 2010-10-14 Industrial Technology Research Institute Flat speaker structure

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