US3665352A - Permanent magnet system for a loudspeaker - Google Patents

Permanent magnet system for a loudspeaker Download PDF

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Publication number
US3665352A
US3665352A US36594A US3665352DA US3665352A US 3665352 A US3665352 A US 3665352A US 36594 A US36594 A US 36594A US 3665352D A US3665352D A US 3665352DA US 3665352 A US3665352 A US 3665352A
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United States
Prior art keywords
permanent magnet
soft iron
loudspeaker
ferritic steel
air gap
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Expired - Lifetime
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US36594A
Inventor
Hermann Dietrich
Karl Schuler
Heinz Gunter Meese
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Deutsche Edelstahlwerke AG
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Deutsche Edelstahlwerke AG
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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
    • H04R9/00—Transducers of moving-coil, moving-strip, or moving-wire type
    • H04R9/02—Details
    • H04R9/025—Magnetic circuit
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/02—Permanent magnets [PM]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/02—Permanent magnets [PM]
    • H01F7/0273—Magnetic circuits with PM for magnetic field generation
    • H01F7/0289—Transducers, loudspeakers, moving coil arrangements
    • 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
    • H04R2209/022—Aspects regarding the stray flux internal or external to the magnetic circuit, e.g. shielding, shape of magnetic circuit, flux compensation coils

Definitions

  • the invention is concerned with a permanent magnet system for loudspeakers that consists of a bar or ring shaped axial magnetized permanent magnet and soft iron portions such as bottom plates or top, upper plates and ore.
  • Loudspeaker magnet systems are known in various styles. Loudspeaker magnet systems must, as is known, show a high air gap induction. Onthe other hand, it must be considered in thebuilding of a loud speaker magnet system that no overtones are produced in the speech coil which is disposed in the annular clearance of the loud speaker magnet system which lead to sound distortion. The characteristic distortion factor ing of the magnetic induction.
  • the problem of the present invention is the creation of a loudspeaker magnet system by which the distortion factor becomes reduced without injury to or lessening of the air gap induction.
  • German patent 1,280,324 A solution of this problem is known through German patent 1,280,324.
  • This known solution to be sure fulfills the above-named requirement after lowering of the distortion factor with retention of the air gap induction required by the system, however, it exhibits in the manufacture of such loudspeaker magnet systems technical production difficulties.
  • the known system structure requires a high manufacturing costQPrimarily the rings must be produced from the laminated dynamo and be made in a crude manner.
  • the loudspeaker system must be broken in the soft iron parts, especially in the upper plates and the soft iron core grooves, in which the plated rings should beinserted. Subsequently, the rings must be once more overwou'nd or overground in order to form the ring gap in the required tolerance.
  • a loudspeaker system which is simpler and cheaper to produce than known systems and which fulfills the above-named magnetic and acoustical requirements.
  • part of the ferromagnetic circuit in the system from a mechanically workable, dense alloyed ferritic steel with higher electrical and lower magnetic resistance than soft iron and a saturation magnetization equal to or greater than the required air gap induction of the system.
  • the part of ,the ferromagnetic-circuit found in the region of the air gap should consist of alloyed ferritic steel. This can be accomplished for example by production of the upper plate of the system and a-cover plate from alloyed ferritic steel on the soft iron core.
  • ferritic steel which fulfills the above-named provisions there are preferably used one such as C up to 0.15% Si 0.3 to 2.5% A1 0.2 to 2.0% Cr 5 to 25% Mn 0.6 to 0.8% Ni up to 0.5% Mo up to 0.35% Fe balance
  • Mn 0.7% Al 0.9% Ni 0.3% Cr 13.5% M0 0.2% Fe balance shows the advantage that part of the ferromagnetic circuit of the system can be produced from a dense raw material and not be required to be formed by relatively expensive layers of laminations. An especially simple solution results if according to the preferred development of the system the entire upper plate of the system and a cover plate on the soft iron core are produced from alloyed ferritic steel.
  • FIG. 1 is a sectional view illustrating one form of the invention
  • FIG. 2 shows an alternative embodiment
  • FIG. 3 illustrates a sectional view of still another embodiment of the invention.
  • an axial magnetized ring-shaped permanent magnet I of hard ferritic material in which is inserted concentrically the soft iron core 3 while leaving free the annular clearance 2.
  • the core 3 is, for example, combined with the bottom plate 4 as a single piece.
  • the upper plate 5 and a cover plate 6 on the soft iron core 3 can be made of alloyed ferritic steel. This material has first the required high electrical resistance at low magnetic resistance and besides possesses a saturation magnetization which corresponds to the air gap induction required by the system.
  • FIG. 2 employing a stray field poor loudspeaker system by inserting rings 7 and 17 of alloyed ferritic steel in the upper plate 5 and in the soft iron core 3 on both sides of the air gap in the region of the speech coil disposed in the annular clearance.
  • the system of FIG. 2 is distinguished in the additional arrangement of a permanent magnet 8 of hard ferritic material below the intermediate plate 9 of soft iron and a casing of soft iron surrounding the system.
  • FIG. 3 there is shown another known construction for loudspeaker magnet systems.
  • a soft iron casing 10 there is arranged a rod shaped permanent magnet I of preferably Alnico material with a soft iron core 3 erected thereon.
  • the upper plate 5 according to the invention is likewise entirely or partially made of alloyed ferritic steel.
  • Non-illustrated example possibilities include a ring of alloyed ferritic steel disposed in the upper plate 5 and the core 3 entirely of alloyed ferritic steel. Additionally the combination of a cover plate on the soft iron core and in the ring 7 disposedon the upper plate at times can be made of alloyed ferritic steel.
  • a permanent magnet system for a loudspeaker which consists of axial magnetic magnets and soft iron parts forming an air gap therebetween the improvement comprising making a portion of the ferromagnetic circuit in the system from a mechanically machinable, dense, alloyed ferritic steel with higher electrical and lower magnetic resistance than soft iron and a saturation magnetization at least equal to the airgap induction required by the system.
  • a permanent magnet according to claim 2 wherein the soft iron part is located concentric with respect to the magnets including first and second plates for the system which are attached to the longitudinal ends of the magnets and soft iron part, said plates being made of ferritic steel.

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

Abstract

A permanent magnet system is made for a loudspeaker consisting of a rod or ring-formed axial magnetic magnets and soft iron parts. A portion of the ferromagnetic circuit in the system is made from a mechanically machinable, dense alloyed ferritic steel with higher electrical and lower magnetic resistance than soft iron and a saturation magnetism at least equal to the air gap induction required by the system.

Description

United 7 States Patent Dietrich et al.
nsl' 3,665, 3 5 2 [451 May 23;, 1972 [541 PERMANENT MAGNET SYSTEM FOR A- LOUDSPEAKER 72 Inventors: Hermann Dietrich, Willich; Karl Schuler,
Donmunddioerde; Heinz Gunter Mme, Dortmund-Aplerbeck, all of Germany FOREIGN PATENTS OR APPLICATIONS 7 Primary 1l1tanu'nerGeorge Harris Attorney-Cushinan, Darby & Cushman [73] Assignee: Deutsche Edelstahlwerke Aktiengesellschalt, Krefeld, Germany [57] i ABSTRACT. Filed: y 1 A permanent magnet system is made for a loudspeaker consisting of a rod or ring-formed axial magnetic magnets and soft [2 I] App! 36594 iron parts. A portion of the ferromagnetic circuit in the system is made from a mechanically machinable, dense alloyed fer- [52] U.S. Cl. .335/231, 179/119 ritic steel with higher electrical and lower magnetic resistance [51 Int-CI. ..H01f 7/00 than soft iron and a saturation magnetism at least equal to the [58] Field of Search ..335/231; 179/1 15.5, 1 17, 1 19 air gap induction required by the system.
' [56 1 References Cited 4 Claim, 3 Drawing Balms UNITED STATES PATENTS 1.976.874 l0/l934 Brzeski 179/1 l5.5
* 3 \\\s H. U
t 1 t H t K/ t\ Q M 8 1 i It PERMANENT MAGNET SYSTEM FOR A LOUDSPEAKER The invention is concerned with a permanent magnet system for loudspeakers that consists of a bar or ring shaped axial magnetized permanent magnet and soft iron portions such as bottom plates or top, upper plates and ore.
Loudspeaker magnet systems are known in various styles. Loudspeaker magnet systems must, as is known, show a high air gap induction. Onthe other hand, it must be considered in thebuilding of a loud speaker magnet system that no overtones are produced in the speech coil which is disposed in the annular clearance of the loud speaker magnet system which lead to sound distortion. The characteristic distortion factor ing of the magnetic induction.
The problem of the present invention is the creation of a loudspeaker magnet system by which the distortion factor becomes reduced without injury to or lessening of the air gap induction.
A solution of this problem is known through German patent 1,280,324. The proposal made there tends to produce poles on both sides of the air gap of the permanent magnet system in the region of motion of the speech coil from concentric dynamo laminations which are formed one on top of the other in the direction of the length of the gap. This known solution to be sure fulfills the above-named requirement after lowering of the distortion factor with retention of the air gap induction required by the system, however, it exhibits in the manufacture of such loudspeaker magnet systems technical production difficulties. The known system structure requires a high manufacturing costQPrimarily the rings must be produced from the laminated dynamo and be made in a crude manner. Then the loudspeaker system must be broken in the soft iron parts, especially in the upper plates and the soft iron core grooves, in which the plated rings should beinserted. Subsequently, the rings must be once more overwou'nd or overground in order to form the ring gap in the required tolerance.
According to the invention a loudspeaker system is proposed which is simpler and cheaper to produce than known systems and which fulfills the above-named magnetic and acoustical requirements.
For the solution of this problem according to the invention it is proposed to produce part of the ferromagnetic circuit in the system from a mechanically workable, dense alloyed ferritic steel with higher electrical and lower magnetic resistance than soft iron and a saturation magnetization equal to or greater than the required air gap induction of the system. Especially the part of ,the ferromagnetic-circuit found in the region of the air gap should consist of alloyed ferritic steel. This can be accomplished for example by production of the upper plate of the system and a-cover plate from alloyed ferritic steel on the soft iron core.
Unless otherwise indicated all parts are by weight.
As a ferritic steel which fulfills the above-named provisions there are preferably used one such as C up to 0.15% Si 0.3 to 2.5% A1 0.2 to 2.0% Cr 5 to 25% Mn 0.6 to 0.8% Ni up to 0.5% Mo up to 0.35% Fe balance In a specific example there was used C 0.1% Si 1.0% Mn 0.7% A1 0.9% Ni 0.25% Cr 18.0% M0 0.15% Fe balance For anotherexample there was used Mn 0.7% Al 0.9% Ni 0.3% Cr 13.5% M0 0.2% Fe balance shows the advantage that part of the ferromagnetic circuit of the system can be produced from a dense raw material and not be required to be formed by relatively expensive layers of laminations. An especially simple solution results if according to the preferred development of the system the entire upper plate of the system and a cover plate on the soft iron core are produced from alloyed ferritic steel.
In the drawings there are shown non limiting examples of various loudspeaker magnet systems useful in the invention.
FIG. 1 is a sectional view illustrating one form of the invention; 4
FIG. 2 shows an alternative embodiment; and
FIG. 3 illustrates a sectional view of still another embodiment of the invention.
In the drawings like numbers indicate like parts.
Referring more specifically to FIG. 1 of the drawings in the structure of a conventional loudspeaker system there is provided an axial magnetized ring-shaped permanent magnet I of hard ferritic material in which is inserted concentrically the soft iron core 3 while leaving free the annular clearance 2. The core 3 is, for example, combined with the bottom plate 4 as a single piece. According to the invention the upper plate 5 and a cover plate 6 on the soft iron core 3 can be made of alloyed ferritic steel. This material has first the required high electrical resistance at low magnetic resistance and besides possesses a saturation magnetization which corresponds to the air gap induction required by the system.
Instead of the embodiment shown in FIG. I, nearly the same efiect can-be obtained as illustrated by FIG. 2 employing a stray field poor loudspeaker system by inserting rings 7 and 17 of alloyed ferritic steel in the upper plate 5 and in the soft iron core 3 on both sides of the air gap in the region of the speech coil disposed in the annular clearance. In contrast to the magnet system produced in FIG. I, the system of FIG. 2 is distinguished in the additional arrangement of a permanent magnet 8 of hard ferritic material below the intermediate plate 9 of soft iron and a casing of soft iron surrounding the system.
In FIG. 3 there is shown another known construction for loudspeaker magnet systems. In a soft iron casing 10 there is arranged a rod shaped permanent magnet I of preferably Alnico material with a soft iron core 3 erected thereon. The upper plate 5 according to the invention is likewise entirely or partially made of alloyed ferritic steel.
Further non-illustrated example possibilities include a ring of alloyed ferritic steel disposed in the upper plate 5 and the core 3 entirely of alloyed ferritic steel. Additionally the combination of a cover plate on the soft iron core and in the ring 7 disposedon the upper plate at times can be made of alloyed ferritic steel.
WHAT IS CLAIMED IS:
1. In a permanent magnet system for a loudspeaker which consists of axial magnetic magnets and soft iron parts forming an air gap therebetween the improvement comprising making a portion of the ferromagnetic circuit in the system from a mechanically machinable, dense, alloyed ferritic steel with higher electrical and lower magnetic resistance than soft iron and a saturation magnetization at least equal to the airgap induction required by the system. i
2. A permanent magnet system according to claim 1 wherein the portion of the ferromagnetic circuit of the system in the region of the air gap consists of alloyed ferritic steel.
3. A permanent magnet according to claim 2 wherein the soft iron part is located concentric with respect to the magnets including first and second plates for the system which are attached to the longitudinal ends of the magnets and soft iron part, said plates being made of ferritic steel.
4. A permanent magnet according to claim 1 wherein a portion of the ferromagnetic circuit in the system consists of up to 5 0.15% C., 0.3 to 2.5% of Si, 0.2 to 2.0% A], 5 to 25% Cr and balance iron.

Claims (4)

1. In a permanent magnet system for a loudspeaker which consists of axial magnetic magnets and sofT iron parts forming an air gap therebetween the improvement comprising making a portion of the ferromagnetic circuit in the system from a mechanically machinable, dense, alloyed ferritic steel with higher electrical and lower magnetic resistance than soft iron and a saturation magnetization at least equal to the airgap induction required by the system.
2. A permanent magnet system according to claim 1 wherein the portion of the ferromagnetic circuit of the system in the region of the air gap consists of alloyed ferritic steel.
3. A permanent magnet according to claim 2 wherein the soft iron part is located concentric with respect to the magnets including first and second plates for the system which are attached to the longitudinal ends of the magnets and soft iron part, said plates being made of ferritic steel.
4. A permanent magnet according to claim 1 wherein a portion of the ferromagnetic circuit in the system consists of up to 0.15% C., 0.3 to 2.5% of Si, 0.2 to 2.0% Al, 5 to 25% Cr and balance iron.
US36594A 1970-05-12 1970-05-12 Permanent magnet system for a loudspeaker Expired - Lifetime US3665352A (en)

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Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3830986A (en) * 1971-12-17 1974-08-20 Pioneer Electronic Corp Magnetic circuit for an electro-acoustic converter
US3867587A (en) * 1971-12-17 1975-02-18 Pioneer Electronic Corp Magnetic circuit for an electro-acoustic converter
US3922501A (en) * 1971-12-17 1975-11-25 Pioneer Electronic Corp Moving voice coil electro-acoustic converter with laminated magnetically anisotropic poles
JPS54128729A (en) * 1978-03-29 1979-10-05 Mitsubishi Electric Corp Magnetic circuit for speaker
JPS54159218A (en) * 1978-06-07 1979-12-15 Mitsubishi Electric Corp Speaker
US4289937A (en) * 1978-05-30 1981-09-15 Mitsubishi Denki Kabushiki Kaisha Speaker with fine grain ferromagnetic material on center pole or ring
US4465906A (en) * 1981-12-17 1984-08-14 Magnetfabrik Bonn Gmbh Vormals Gewerkschaft Windhorst Low-leakage pot magnet system for moving-coil loudspeakers
US5070530A (en) * 1987-04-01 1991-12-03 Grodinsky Robert M Electroacoustic transducers with increased magnetic stability for distortion reduction
EP0632676A1 (en) * 1993-06-30 1995-01-04 Kabushiki Kaisha Kenwood Loudspeaker and manufacturing method
US6359997B2 (en) * 1996-04-26 2002-03-19 Harman Audio Electronic Systems Gmbh Loudspeaker having radially magnetized magnetic ring
US20030190051A1 (en) * 1998-07-21 2003-10-09 Williamson Clayton C. Full range loudspeaker
US20030190052A1 (en) * 1998-03-19 2003-10-09 Jbl Incorporated Shorting rings in dual-coil dual-gap loudspeaker drivers
CN102045626A (en) * 2011-01-18 2011-05-04 吴宗汉 Moving-magnetic type ultrathin telephone receiver
CN107948802A (en) * 2017-12-25 2018-04-20 厦门东声电子有限公司 A kind of receiver

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3830986A (en) * 1971-12-17 1974-08-20 Pioneer Electronic Corp Magnetic circuit for an electro-acoustic converter
US3867587A (en) * 1971-12-17 1975-02-18 Pioneer Electronic Corp Magnetic circuit for an electro-acoustic converter
US3922501A (en) * 1971-12-17 1975-11-25 Pioneer Electronic Corp Moving voice coil electro-acoustic converter with laminated magnetically anisotropic poles
JPS54128729A (en) * 1978-03-29 1979-10-05 Mitsubishi Electric Corp Magnetic circuit for speaker
US4289937A (en) * 1978-05-30 1981-09-15 Mitsubishi Denki Kabushiki Kaisha Speaker with fine grain ferromagnetic material on center pole or ring
JPS54159218A (en) * 1978-06-07 1979-12-15 Mitsubishi Electric Corp Speaker
JPS58234B2 (en) * 1978-06-07 1983-01-05 三菱電機株式会社 Speaker magnetic circuit
US4465906A (en) * 1981-12-17 1984-08-14 Magnetfabrik Bonn Gmbh Vormals Gewerkschaft Windhorst Low-leakage pot magnet system for moving-coil loudspeakers
US5070530A (en) * 1987-04-01 1991-12-03 Grodinsky Robert M Electroacoustic transducers with increased magnetic stability for distortion reduction
US5701657A (en) * 1993-06-30 1997-12-30 Kabushiki Kaisha Kenwood Method of manufacturing a repulsion magnetic circuit type loudspeaker
EP0632676A1 (en) * 1993-06-30 1995-01-04 Kabushiki Kaisha Kenwood Loudspeaker and manufacturing method
US6359997B2 (en) * 1996-04-26 2002-03-19 Harman Audio Electronic Systems Gmbh Loudspeaker having radially magnetized magnetic ring
US20030190052A1 (en) * 1998-03-19 2003-10-09 Jbl Incorporated Shorting rings in dual-coil dual-gap loudspeaker drivers
US6768806B1 (en) * 1998-03-19 2004-07-27 Harman International Industries, Incorporated Shorting rings in dual-coil dual-gap loudspeaker drivers
US6847726B2 (en) * 1998-03-19 2005-01-25 Harman International Industries, Incorporated Shorting rings in dual-coil dual-gap loudspeaker drivers
US20030190051A1 (en) * 1998-07-21 2003-10-09 Williamson Clayton C. Full range loudspeaker
US7167573B2 (en) 1998-07-21 2007-01-23 Harman International Industries, Incorporated Full range loudspeaker
CN102045626A (en) * 2011-01-18 2011-05-04 吴宗汉 Moving-magnetic type ultrathin telephone receiver
CN102045626B (en) * 2011-01-18 2014-08-20 吴宗汉 Moving-magnetic type ultrathin telephone receiver
CN107948802A (en) * 2017-12-25 2018-04-20 厦门东声电子有限公司 A kind of receiver
CN107948802B (en) * 2017-12-25 2024-04-23 厦门东声电子有限公司 Telephone receiver

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