US2818471A - Moving coil type loudspeakers - Google Patents

Moving coil type loudspeakers Download PDF

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Publication number
US2818471A
US2818471A US491145A US49114555A US2818471A US 2818471 A US2818471 A US 2818471A US 491145 A US491145 A US 491145A US 49114555 A US49114555 A US 49114555A US 2818471 A US2818471 A US 2818471A
Authority
US
United States
Prior art keywords
pole
auxiliary
moving coil
air gap
coil type
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.)
Expired - Lifetime
Application number
US491145A
Other languages
English (en)
Inventor
Carter John George
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.)
GOODMANS IND Ltd
GOODMANS INDUSTRIES Ltd
Original Assignee
GOODMANS IND Ltd
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 GOODMANS IND Ltd filed Critical GOODMANS IND Ltd
Application granted granted Critical
Publication of US2818471A publication Critical patent/US2818471A/en
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/24—Structural combinations of separate transducers or of two parts of the same transducer and responsive respectively to two or more frequency ranges
    • 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

Definitions

  • This invention relates to moving coil type loudspeakers and more particularly to coaxial loudspeakers of the kind embodying two separate moving coil systems, one for high frequency and the other for low frequency reproduction, filters being used to limit the frequency range of each system to the desired frequency band.
  • the magnet assembly comprises a centrepole member co-operating with a front plate or the equivalent to form a first air gap, said pole member being formed or provided at its front end with an auxiliary pole element of smaller diameter which co-operates with a supplementary pole plate to define a second air gap concentric with the first and located in the same magnetic circuit.
  • Fig. 1 is an axial cross section through the improved loudspeaker unit and Fig. 2 is a similar view to a larger scale of the auxiliary magnet system.
  • the unit shown comprises a basic magnet structure of known type consisting of a pot-like casing 1 formed of for example mild steel, a centre pole member 2 and a front pole plate 3 secured to the rim portion of the easing and co-operating with the member 2 to form a first annular air gap 4, the centre pole member in this instance consisting of a magnet 2a and a pole tip 2b which are clamped together and to the casing by a central bolt 5.
  • annular groove or recess 6 is cut in the peripheral portion of the front end of the pole tip 2b in such a manner as to remove a portion of the peripheral face and a portion of the front end face of said pole tip so leaving a short auxiliary centre pole element upstanding from the body portion of the pole tip and of smaller diameter than said body portion.
  • a supplementary ring-shaped pole plate 8 mounted within the annular groove 6 upon a non-ferrous locating ring 7 seated in the groove is a supplementary ring-shaped pole plate 8 formed of mild steel or of a high permeability alloy, said plate being of less thickness than the front pole plate 3 and being so disposed that its front face lies approximately flush with the front faces of the pole plate 3 and of the auxiliary centre pole element 20.
  • the outer or peripheral edge of the plate 8 is aligned with the peripheral face of the pole tip 2b but is slightly spaced therefrom whilst its inner edge co-operates with the auxiliary centre pole element 2c to define a second and smaller annular air gap 9 concentric with the main or outer air gap 4.
  • the supplementary pole plate 8 in conjunction with said auxiliary centre pole element 20 forms an auxiliary magnet system, a portion of the magnetic flux in the main or outer air gap being conducted along the plate 8 to the inner or auxiliary air gap 9, and the proportion of flux thus deflected can be predetermined by the axial location of the supplementary pole plate relative to the main pole tip 2b.
  • the driving coil 10 of a low frequency, cone type diaphragm 11 which may be supported in the usual manner within a chassis 12 to the rear side of which is attached the magnet unit.
  • the driving coil 13 of a high frequency diaphragm 14 which preferably and as shown consists of a dome-like structure enclosing the tip of the auxiliary centre pole element 20 and itself enclosed by a perforated guard or cover 15.
  • the high frequency system is attached to the front end of the centre pole member, the preferred arrangement being as follows:
  • the high frequency diaphragm is supported by a centering device 16 which is clamped between a pair of Washers 17 seated in a recess formed in the upper side of the supplementary pole plate 8, said Washers, the supplementary pole plate and the locating ring 7 being secured in position by a number of non-ferrous bolts, one of which is shown at 18, extending through the assembly and into the pole tip 2b.
  • said bolts also serve to clamp the cover 15 in position, a suitable spacer ring 19 being interposed between said cover and the washer 17 as shown.
  • the high frequency unit may include a small acoustic horn 20 which is then also secured in position by the clamping bolts, whilst if desired the centering device 21 of the low frequency diaphragm may be clamped between the bolting fianges of the cover 15 and the born 20.
  • the embodiment illustrated is given by way of example only and is capable of several modifications.
  • the locating ring 7 may be relieved to meet acoustic requirements or it could be replaced by non-ferrous distance pieces.
  • the groove or recess 6 could be of different shape or the auxiliary centre pole element 20 could be made separately and be bolted in position in which case it could be made of high permeability alloy.
  • the invention is equally applicable to a ring-type permanent magnet assembly or to a mains energised magnet assembly.
  • the invention provides a very simple, effective and economical magnet assembly for a coaxial loudspeaker.
  • a loudspeaker comprising a main center pole member, a main annular pole piece cooperative with said center pole member and defining a first air gap, an auxiliary center pole member of smaller diameter than the main pole member and situated at the end of the latter, an auxiliary annular pole plate cooperative with said auxiliary pole member and defining a second air gap coaxial with the first air gap, a non-magnetic spacing member surrounding the auxiliary pole member and adapted to hold said auxiliary pole plate away from the main pole member, a first moving coil system located in the first air gap, and a second moving coil system located in the second air gap.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
  • Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
US491145A 1954-03-05 1955-02-28 Moving coil type loudspeakers Expired - Lifetime US2818471A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB6547/54A GB767309A (en) 1954-03-05 1954-03-05 Improvements in or relating to moving coil type loudspeakers

Publications (1)

Publication Number Publication Date
US2818471A true US2818471A (en) 1957-12-31

Family

ID=9816486

Family Applications (1)

Application Number Title Priority Date Filing Date
US491145A Expired - Lifetime US2818471A (en) 1954-03-05 1955-02-28 Moving coil type loudspeakers

Country Status (6)

Country Link
US (1) US2818471A (cs)
BE (1) BE536113A (cs)
DE (1) DE1002396B (cs)
FR (1) FR1119908A (cs)
GB (1) GB767309A (cs)
NL (2) NL102625C (cs)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB8402229D0 (en) * 1984-01-27 1984-02-29 Tannoy Ltd Moving coil loudspeaker
GB2261135A (en) * 1991-11-02 1993-05-05 Meir Mordechai A loudspeaker

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2699472A (en) * 1950-07-21 1955-01-11 Rca Corp Coaxial, dual unit, electrodynamic loud-speaker

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB445935A (en) * 1934-10-17 1936-04-17 Alfred Sidney Evans An improved sound reproducing device

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2699472A (en) * 1950-07-21 1955-01-11 Rca Corp Coaxial, dual unit, electrodynamic loud-speaker

Also Published As

Publication number Publication date
NL102625C (cs)
FR1119908A (fr) 1956-06-27
DE1002396B (de) 1957-02-14
NL195295A (cs)
BE536113A (cs)
GB767309A (en) 1957-01-30

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