EP0339820A2 - Elektromagnetischer Wandler - Google Patents

Elektromagnetischer Wandler Download PDF

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Publication number
EP0339820A2
EP0339820A2 EP89303509A EP89303509A EP0339820A2 EP 0339820 A2 EP0339820 A2 EP 0339820A2 EP 89303509 A EP89303509 A EP 89303509A EP 89303509 A EP89303509 A EP 89303509A EP 0339820 A2 EP0339820 A2 EP 0339820A2
Authority
EP
European Patent Office
Prior art keywords
moving coil
electromagnetic transducer
transducer according
pole piece
coil electromagnetic
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP89303509A
Other languages
English (en)
French (fr)
Other versions
EP0339820A3 (de
Inventor
Saad Gabr
Yasser Gabr
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
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
Application filed by Individual filed Critical Individual
Publication of EP0339820A2 publication Critical patent/EP0339820A2/de
Publication of EP0339820A3 publication Critical patent/EP0339820A3/de
Withdrawn legal-status Critical Current

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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
    • 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
    • H04R2209/00—Details of transducers of the moving-coil, moving-strip, or moving-wire type covered by H04R9/00 but not provided for in any of its subgroups
    • H04R2209/043—Short circuited voice coils driven by induction

Definitions

  • This invention relates to electromagnetic transducers and in particular, but not exclusively, to moving coil and moving diaphragm types of transducer for loudspeakers, tweeters, headphones and other devices for similar applications.
  • a common construction of conventional dynamic loudspeaker includes an annular top plate of ferromagnetic material, a back plate integrally formed or fitted with a pole piece each of ferromagnetic material, and a ring magnet disposed between the top plate and the back plate. Between the pole piece and the top plate is defined a narrow gap across which the magnetic flux generated by the magnet passes in a generally radial direction.
  • a diaphragm is mounted in front of the pole piece and has attached thereto a voice coil which fits with clearance in the narrow gap between the pole piece and the top plate. Passage of current through the voice coil causes movement of the diaphragm. It is widely accepted that the efficiency of such a loudspeaker can only be as high as approximately 4%.
  • a moving coil electromagnetic transducer wherein at least one of the components of the transducer which in a conventional transducer constitute an electrically conducting closed loop around the moving coil are made electrically discontinuous such that the magnitude of the energy dissipated by induction in said components of the transducer will be reduced thereby increasing the efficiency of the transducer.
  • the efficiency is increased in terms of higher Q, that is to say higher ratio of inductance over resistance, thus providing better control over the frequency response characteristics in terms of band width and steeper fall off. There will be lower distortion and increased intelligibility of the sound reproduced permitting the production of higher quality electro accoustic transducers at lower cost or at no increased manufacturing cost.
  • One arrangement of transducer comprises a ring-shaped magnet and a magnetic yoke generally concentric therewith comprising a top plate, a back plate and a pole piece, each generally defined by a solid of revolution about the axis of the ring-shaped magnet, and at least one of the top plate, back plate and pole piece is provided with a discontinuity interrupting the electrical circuit which exists around said axis.
  • the or each discontinuity comprises a slit radially aligned with respect to said axis.
  • said back plate and said pole piece are integrally formed.
  • said ring-shaped magnet is formed of a material of high electrical resistivity, for example a ceramic material.
  • said magnet is formed of a material of a relatively low electrical resistivity, then it preferably includes a discontinuity, e.g. a slit, interrupting the electrical circuit which exists around said axis.
  • the transducer includes other components which define electrically conducting closed loops within the induction field of the moving coil of the transducer, for example pole tips on the pole piece and/or on the top plate, a heat sink, diaphragm frame, chassis, metal parts of the diaphragm assembly or a support or mounting frame, it is preferred that these components also include a discontinuity arrangement to interrupt any shorted electrical circuit.
  • the pole tips may be integral with the pole piece or top plate or separate and secured thereto.
  • the term "loop” is intended to include components of solid section within the magnetic field.
  • the diaphragm may be a metallic disc of convex form
  • the pole piece may be of solid cylindrical form or tube; both such items constitute “loops” as defined herein.
  • transducers of the invention there may be more than one discontinuity arrangement in one or more of the components.
  • the components making up the magnetic yoke may be laminated in a generally radial direction, that is they may comprise a plurality of sectors electrically insulated from each other.
  • the transducer includes means for supplying an electrical signal to the moving coil for driving the diaphragm.
  • the moving coil comprises a single closed turn.
  • the transducer means includes a fixed primary coil generally surrounding said pole piece, embedded in the top plate or the pole piece immediately around the respective pole tip, and means are provided for supplying an electrical signal to said primary coil.
  • the transducer is a tweeter incorporating a dome diaphragm supporting a voice coil which is supplied with the input signal.
  • the tweeter comprises an annular top plate 12 of ferromagnetic material, a ring-shaped magnet 14 of ceramic material which does not conduct electricity, and an integral component of ferromagnetic material which defines a generally annular back plate 16 and a hollow pole piece 18.
  • the pole piece 18 supports a phasing plug 19 (shown in Figure 2 only) of plastics, non electrically conducting material.
  • Each of the top plate 12, the back plate 16 and the hollow pole piece 18 is a solid of revolution about the axis of the ring-shaped magnet 14, and each includes a radial slit 20 which ensures that the electrically conducting closed loop which would otherwise exist is interrupted.
  • the width of the slit 20 need only be large enough to prevent circulation of electric current - typically 0.5 to 1mm, and is believed to have only a very minor influence on the magnetic field.
  • the gap formed by the slit is preferably filled with a suitable non-conducting resin material.
  • a dome diaphragm 22 is supported on the top plate 12 and carries a multi-turn voice coil 24 of fine wire which is located in the narrow annular gap defined between the inner periphery of the top plate 12 and the outer periphery of the pole piece 18.
  • the terminals of the voice coil 24 are attached to two tags 26 at the edge of the diaphragm 22.
  • the active, central part of the diaphragm 22 is formed of a thin sheet of metallic or non-metallic material. Since a metallic dome may also constitute a closed loop, a non-conducting sector 30 may be introduced into the diaphragm 22 if it is made of metal by replacing the metal material by a non-conducting sheet material of similar mechanical properties. Alternatively, the diaphragm 22 may be made of a material which does not conduct electricity.
  • an input signal is applied to the two tags 26 and the voice coil moves in accordance with the current supplied. Because the top plate 12 and the integral pole piece 18 and back plate 16 include a discontinuity in the form of the slit 20, they cannot act as a single short-circuited coil.
  • the diaphragm is generally cone shaped and supported at its outer edge by a flexible flange attached to one end of a metal support which is connected at its other end to the top plate 12.
  • the metal support frame would ordinarily also define a closed, electrically conducting path which will be within the varying magnetic field generated in use.
  • the metal support frame include a discontinuity such as a slit or a series of slits to break the electrical circuit otherwise defined by the support frame.
  • the top plate may include an annular support plate or heat sink for heat generated in use. Again, the annular support plate should include one or more slits to prevent it defining a short-circuited loop within the influence of the varying magnetic field.
  • FIG. 5 there is shown another example of a transducer incorporating features of this invention.
  • the construction of the top plate 12, the ring-shaped magnet 14, the integral back plate 16 and hollow pole piece 18 are similar to those of the arrangement of Figures 1 to 4 and will not be described in detail again.
  • the dome diaphragm 22 is of generally similar structure except that the voice coil 25 is in the form of a single, closed coil. It may, for example, simply be a cylinder of electrically conducting sheet material.
  • the transducer is energised by means of a fixed coil 32 which surrounds the lower portion of the pole piece 18.
  • a pole tip 18 a of the pole piece 18 and a pole tip 12 a of the front plate 12 are shown integral with the pole piece 18 and the front plate 12 respectively.
  • the pole tip 18 a is shown to be tapered towards the air gap whereas the pole tip 12 a is parallel sided. Either tapered or parallel sided pole tips may be used for the front plate and pole piece as desired.
  • Separate pole tips 18 a , 12 a may be provided and be attached to the pole piece 18 and the front plate 12 respectively if desired and as shown in Figure 6. If separate pole tips 18 a , 12 a are provided then they should be provided with a slit 20 to make them discontinuous.
  • the pole tips if separate may be provided of a different material or of the same material as the pole piece 18 and the front plate 12, they could for example be provided of a material of different magnetic permeability and saturation.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
  • Reciprocating, Oscillating Or Vibrating Motors (AREA)
EP19890303509 1988-04-26 1989-04-10 Elektromagnetischer Wandler Withdrawn EP0339820A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB888809805A GB8809805D0 (en) 1988-04-26 1988-04-26 Electromagnetic transducer
GB8809805 1988-04-26

Publications (2)

Publication Number Publication Date
EP0339820A2 true EP0339820A2 (de) 1989-11-02
EP0339820A3 EP0339820A3 (de) 1991-03-20

Family

ID=10635840

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19890303509 Withdrawn EP0339820A3 (de) 1988-04-26 1989-04-10 Elektromagnetischer Wandler

Country Status (4)

Country Link
EP (1) EP0339820A3 (de)
JP (1) JPH01318399A (de)
AU (1) AU3301289A (de)
GB (1) GB8809805D0 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0537705A3 (de) * 1991-10-16 1994-03-23 Lux Corp

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04103796U (ja) * 1991-01-24 1992-09-07 株式会社ケンウツド スピーカ用磁気回路およびそれに用いられるボイスコイル
JP4630319B2 (ja) * 2007-09-10 2011-02-09 宏一 平岡 ホーンスピーカ

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL61472C (de) * 1938-05-04
DE2131035A1 (de) * 1971-06-23 1973-01-11 Magnetfab Bonn Gmbh Ringspalt-magnetsystem mit polen verminderter elektrischer leitfaehigkeit
US4293741A (en) * 1979-06-21 1981-10-06 Digre Clifford B Magnet assembly
JPS5627600A (en) * 1979-08-10 1981-03-17 Kanenori Kishi Magnetic circuit of moving coil type transducer
US4295011A (en) * 1979-09-11 1981-10-13 Epicure Products Inc. Linear excursion-constant inductance loudspeaker
US5062140A (en) * 1988-04-27 1991-10-29 Sony Corporation Induction speaker

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0537705A3 (de) * 1991-10-16 1994-03-23 Lux Corp

Also Published As

Publication number Publication date
JPH01318399A (ja) 1989-12-22
EP0339820A3 (de) 1991-03-20
AU3301289A (en) 1989-11-02
GB8809805D0 (en) 1988-06-02

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