Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
  • H04R9/02—Details
  • H04R9/025—Magnetic circuit
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
  • H04R9/02—Details
  • H04R9/04—Construction, mounting, or centering of coil
  • H04R9/046—Construction
  • H04R9/047—Construction in which the windings of the moving coil lay in the same plane
  • H04R9/048—Construction in which the windings of the moving coil lay in the same plane of the ribbon type

Definitions

• Electro-acoustic transducer with electrically conducting membrane Electro-acoustic transducer with electrically conducting membrane
• the present invention relates to an electro-acoustic transducer, in particular of the type that comprises a source of sound formed from an electrically conducting membrane in a homogenous magnet field with high flux.
• electro-acoustic transducers membranes in the form of narrow bands are inserted in the gap between the pole pieces, which along their length carries a number of magnets for the generation of a magnetic force field across the gap between the pole pieces.
• This type of electro-acoustic transducer can be used for all purposes where a natural sound is desired, such as for use m studios and by orchestras, and are also used outdoors, such as at outdoor concerts.
• An electro-acoustic transducer of this type can comprise two or more gaps with one membrane m each gap.
• the purpose of the present invention therefore has been to provide an improved electro-acoustic transducer having a very distinct acoustic image where the magnetic flux across the gap can be markedly increased by reducing the leak fields in the magnet flux circuit, whereby a higher efficiency for the electro- acoustic transducer can be achieved.
• the present invention relates to an electro-acoustic transducer comprising two or more elongated pole pieces arranged in parallel to each other and at a distance from each other, comprising magnet elements wherein two adjacent pole pieces form an elongated slit in which an elongated membrane of an electrically conducting material is moveably provided, said membrane being electrically coupled such that it can conduct drive current in the longitudinal direction of the membrane, and which is characterized in that a magnetic conductor of a ferro-magnetic material is provided between the outermost located pole pieces, said magnetic conductor closing the magnetic circuit but leaving open the slit or slits m which the membranes are provided, whereby the magnetic field strength increases in the slit or slits.
• FIG. 1 schematically in perspective shows an electro-acoustic transducer according to the invention seen from the back
• Fig. 2 illustrates schematically the electro-acoustic transducer in fig. 1 seen from above and in a larger magnification
• Fig. 3 which is identical with fig. 2 except for sheet metal having been used instead of b ⁇ dg- ing elements to close the magnetic circuit
• Fig. 4 illustrates an embodiment having several parallel pole pieces.
• the electro-acoustic transducer shown in the drawing figures comprises two elongated pole pieces 1 , 2 arranged in parallel, between which there is provided an elongated, thin, ribbon-shaped membrane 3.
• the pole pieces 1 , 2 are made of a ferro-magnetic material, i.e. iron. Furthermore, at the pole pieces there is provided a number of permanent magnets 5 along the gap 4, formed between the pole pieces 1 , 2, said magnets being arranged with a reversed polarisation on both sides of the gap 4.
• the pole pieces 1, 2 may have a substantial length e.g. up to 2 meters or more depending on the purpose.
• the membrane 3 has a somewhat smaller width than the distance between the pole pieces 1, 2, and is provided to be centred between the pole pieces.
• the membrane typically is 2 mm narrower than the width of the gap 4.
• the membrane 3 is at least provided with a surface layer of an electrically conducting material, e.g. aluminium, which could be deposited by evaporation or laminated and which can have a body of some other material, e.g. a plastic material, such as MYLAR® or KAPTON®.
• the thickness of the membrane 3 is very small though, e.g. of the order of 5 - 30 ⁇ m including the surface layer.
• the membrane has a width of the order of 10 - 50 mm, and a length corresponding to the length of the rods 1 , 2.
• the membrane can also be comprised of a homogenous metal band, e.g. of copper, aluminium or silver.
• the membrane 3 could be pleated across its longitudinal direction, or have an imprinted pattern, e.g. of a honeycomb or leather structure.
• the membrane 3 at its both ends is connected to electrical leads (not shown).
• the membrane is clamped in the gap 4 between the pole pieces 1 , 2 without being so stretched in its longitudinal direction that the motion of the membrane 3 caused by a current running in longitudinal direction of the membrane is affected. If in addition the membrane has a large length it can also be required to provide further support attachment means at the pole pieces along its length.
• the pole pieces according to a first embodiment of the invention are mutually connected with each other by means of a magnetic conductor in the form of bridging elements 6, arranged evenly distributed along a length of the pole pieces 1 , 2 and provided on the back side of the pole pieces.
• the bridging elements are made of a ferro-magnetic material and are dimensioned to have a cross sectional area such that magnetic saturation is prevented.
• the number of bridging elements 6 along the pole pieces 1 , 2 can be adapted to give the desired total cross sectional area, such that magnetic saturation will not occur in the bridging elements 6.
• the shape of the bridging elements 6 is furthermore selected such that the surface thereof facing the pole pieces does not reflect the sound waves in the direction back towards the membrane, and for this purpose they may e.g. have a circular cross sectional profile.
• the bridging elements In order to function the bridging elements must be magnetically connected with the pole pieces 1, 2, and may e.g. be fastened to the latter m that the ends of the bridging elements 6 are threaded and tightened to the pole pieces by means of screws running through through-holes from the front of the pole pieces 1 , 2 to the back thereof.
• a magnetic conductor in the form of an arched, thick piece of sheet metal 7 running between the pole pieces along the length thereof.
• the plate is made of a ferro-magnetic material and has a total cross sectional area such that magnetic saturation is prevented.
• the piece of sheet metal should be magnetically coupled to the pole pieces.
• the shape of the cavity 8 formed by the piece of sheet metal 7 should essentially be formed such that parallel surfaces do not occur in order to reduce the risk for standing waves to occur.
• figure 4 there is shown an embodiment with several pole pieces forming three slits 3. Only the magnets are shown except that the outermost pole pieces are indicated.
• the bridging elements 6 or the piece of sheet metal 7 extend from one of the outermost pole pieces 9 to the other outermost pole piece 10.
• the magnetic conductor thus encloses the entire backside of the device. This embodiment is necessary for all those cases where one and the same pole piece delimits a gap 3 on both sides of the pole piece.

Landscapes

• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20411055

Family Applications (1)

Country Status (3)

Cited By (3)

Citations (3)

• 1998
  • 1998-04-22 SE SE9801413A patent/SE9801413L/sv not_active Application Discontinuation
• 1999
  • 1999-04-22 WO PCT/SE1999/000654 patent/WO1999055118A1/en active Application Filing
  • 1999-04-22 AU AU42999/99A patent/AU4299999A/en not_active Abandoned

Patent Citations (3)

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