EP0341926B1 - Lautsprecher - Google Patents

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Publication number
EP0341926B1
EP0341926B1 EP89304569A EP89304569A EP0341926B1 EP 0341926 B1 EP0341926 B1 EP 0341926B1 EP 89304569 A EP89304569 A EP 89304569A EP 89304569 A EP89304569 A EP 89304569A EP 0341926 B1 EP0341926 B1 EP 0341926B1
Authority
EP
European Patent Office
Prior art keywords
diaphragm
magnetic
low frequency
high frequency
drive unit
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
EP89304569A
Other languages
English (en)
French (fr)
Other versions
EP0341926B2 (de
EP0341926A1 (de
Inventor
Lawrence Reginald Fincham
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.)
KEF Audio UK Ltd
Original Assignee
KH Technology Corp
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Filing date
Publication date
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Application filed by KH Technology Corp filed Critical KH Technology Corp
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Publication of EP0341926B1 publication Critical patent/EP0341926B1/de
Publication of EP0341926B2 publication Critical patent/EP0341926B2/de
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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
    • 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

Definitions

  • This invention relates to loudspeakers and in particular to compound loudspeaker drive units in which separate diaphragms are provided for reproduction of the low and high audio frequencies.
  • separate loudspeaker drive units are provided for reproduction of bands of audio frequencies, for example a woofer unit for reproduction of sounds in a low frequency band and a tweeter unit for reproduction of sounds in a high frequency band.
  • the voice coils of the loudspeaker drive units are connected to the output of a power amplifier, or other source, through a suitable cross-over filter network which ensures that only electrical signals representing sounds in the appropriate bands are applied to the individual loudspeaker voice coils.
  • the characteristic of the cross-over filter is arranged so that in a mid frequency cross-over band intermediate the low and high frequency bands the outputs of the two loudspeaker drive units tail off; the output of the low frequency loudspeaker drive unit reduces with increase of frequency while the output of the high frequency loudspeaker drive unit reduces with decrease in frequency.
  • the low and high frequency loudspeaker drive units At a so-called crossover frequency the low and high frequency loudspeaker drive units have outputs which are equal but reduced in comparison with their outputs within their respective frequency bands.
  • the electrical energisations of the respective voice coils are adjusted so that the sound outputs of the loudspeaker drive units are relatively matched and together provide a substantially uniform output over the total frequency range of the combination of the two loudspeaker drive units.
  • the sound radiated from each of the drive units may be said to emanate from the apparent sound source or acoustic centre of that unit; the position of the acoustic centre is a function of the design of the particular unit and may be determined by acoustic measurement.
  • the loudspeaker drive units are usually mounted on a common baffle such that they lie in a common plane and are offset in a vertical direction in the plane of the baffle. For a listener positioned approximately in line with the axes of the loudspeaker drive units and approximately equidistant from the acoustic centres of both drive units, a desired balance of output from the two drive units can be obtained.
  • the distances between the listener and the acoustic centres of the two loudspeaker drive units will be different and hence sounds in the mid frequency band produced by both loudspeakers will be received by the listener from the two drive units with a difference in time.
  • This time difference between sounds received from the two drive units results in a change in phase relationship of the sounds received at the listening position from the two drive units.
  • the sounds from the two drive units no longer add together as intended in the cross-over band. Consequently the resultant received sound levels will vary with frequency and the overall sound output of the loudspeaker combination will appear to the listener to be non-uniform.
  • the compound co-axial loudspeaker drive unit consists of a generally conical low frequency diaphragm driven by a voice coil interacting with a magnetic structure having a central pole extending through the voice coil.
  • a high frequency diaphragm is positioned to the rear of the structure and sound output from this diaphragm is directed to the front of the loudspeaker drive unit by means of a horn structure extending co-axially through the centre pole of the magnetic structure which interacts with the low frequency diaphragm.
  • both the low frequency and high frequency sounds are directed in a generally forward direction from the compound loudspeaker drive unit.
  • this co-axial form of loudspeaker construction there is no vertical or horizontal offset of the apparent sound sources for low and high frequencies.
  • the low frequency diaphragm is positioned at the front of the loudspeaker unit whereas the high frequency diaphragm is positioned at the rear of the loudspeaker unit and this results in relative displacement of the apparent sound sources in the direction of the axis of the drive unit and an undesirable time difference in the arrival, at the listener, of sounds from the high and low frequency diaphragms.
  • FR A-1 001 734 discloses a compound loudspeaker drive unit comprising a low frequency conical diaphragm flaring outwardly from a neck of the diaphragm with a voice coil secured to the neck of the diaphragm and a high frequency domed diaphragm located in the neck of the low frequency diaphragm.
  • the drive unit includes a common magnetic structure having two concentric air gaps in which the voice coils of the low and high frequency diaphragms respectively extend. The whole of the magnetic flux for the air gap in which the voice coil of the high frequency diaphragm moves also passes through the air gap for the low frequency voice coil.
  • GB A-2 153 628 discloses a construction of compound loudspeaker drive unit including a low frequency diaphragm and a domed high frequency diaphragm located in a central opening in the low frequency diaphragm.
  • the low frequency diaphragm is flat or of conical or domed form extending rearwardly from the central opening thereof to avoid diffraction or tunnel effects upon the high frequency diaphragm so that the high frequency diaphragm is permitted to operate as a direct radiator.
  • An air gap for a voice coil secured to the low frequency diaphragm is formed between an outer pole piece and a central pole piece.
  • a magnet is located in an aperture in the end of the central pole piece and a plate on the magnet forms, with the end of the central pole piece, an air gap for a voice coil secured to the domed high frequency diaphragm.
  • a compound loudspeaker drive unit including a low frequency conical first diaphragm flaring outwardly and forwardly from a neck of said diaphragm to generate sounds in a low frequency range; a first voice coil secured to said neck of said conical diaphragm;
  • a compound loudspeaker drive unit with low frequency and high frequency transducers having co-axial low and high frequency voice coils comprises a chassis 10 in the form of a conical basket having a front annular rim 11 connected to a rear annular member 12 by means of a number of ribs 13.
  • the rear annular member 12 has an annular flange 14 and an annular seat 15.
  • a first magnetic structure 16 for the low frequency loudspeaker drive unit Secured to the flange 14 is a first magnetic structure 16 for the low frequency loudspeaker drive unit.
  • the magnetic structure 16 comprises a magnet ring 17, which may for example be formed of barium ferrite, a front annular plate 18 which forms an outer pole and a member 19 which forms a backplate and inner pole 20.
  • the plate 18, magnet ring 17 and member 19 are held together to provide a magnetic path interrupted by a non-magnetic air gap between the outer pole 18 and the inner pole 20.
  • the poles are circular and form therebetween an annular air gap.
  • the low frequency transducer or loudspeaker drive unit comprises a diaphragm 21 of generally frusto-conical form supported along the front outer edge thereof by a flexible surround 22 secured to the front rim 11 of the chassis 10.
  • a tubular coil former 23 is secured to the rear edge of the diaphragm 21 and is arranged to extend co-axially of the air gap in the magnetic structure 16.
  • the coil former carries a voice coil 24 positioned on the former such that the coil extends through the airgap.
  • the coil is of sufficient axial length as to ensure that for normal excursions of the voice coil, the poles always lie within the length of the voice coil.
  • the backplate and inner pole member 19 has a bore 26 extending co-axially thereof for the purpose of mounting a high frequency drive unit 27.
  • the high frequency transducer or drive unit 27 comprises a second magnetic structure consisting of a pot 28, a disc shaped magnet 29 and a disc shaped inner pole 30.
  • the pot 28 has a cylindrical outer surface so dimensioned as to fit within the interior of the coil former 23 without making physical contact therewith.
  • the pot is formed with a circular recess 31 to receive the magnet 29 and an annular lip 32 to form an outer pole.
  • One circular pole face of the magnet 29 is held in engagement with the bottom wall of the recess 31 and the disc shaped inner pole 30 is held in engagement with the other circular pole face of the magnet such that the circular outer periphery of the inner pole 30 lies co-axially with and within the lip 32 forming the outer pole.
  • a non-magnetic air gap extends between the inner and outer poles.
  • a spacer ring 33 is secured to the front face of the pot 28.
  • the magnet 29 is formed of neodymium iron boron which allows a very substantially enhanced magnetic field strength as compared with other available magnetic materials to be attained in the air gap between the poles.
  • the overall size of the high frequency magnetic structure, for a required flux in the air gap can be smaller than hitherto thereby allowing the high frequency drive unit to be positioned within the coil former of the low frequency drive unit immediately adjacent to the apex of the low frequency diaphragm 21.
  • the magnet 29 may be formed of other materials having magnetic properties substantially similar or superior to that of neodymium iron boron.
  • a high frequency domed diaphragm 34 has an annular support 35 of annular corrugated form and this support is secured at its outer periphery to the spacer ring 33. Secured to the domed diaphragm 34 is a cylindrical coil former carrying a high frequency voice coil 36 such that the voice coil extends through the air gap between the poles 30, 32 of the magnetic structure.
  • a rod 37 is secured centrally to the rear face of the pot 28 and extends through the bore 26 of the low frequency magnetic structure.
  • the high frequency drive unit tends to be held in engagement with the pole 20 of the magnetic structure 16 by magnetic attraction therebetween but is secured to the structure 16 by a threaded end portion 38 of the rod 37 extending through an aperture in a plate 39 positioned at the rear of the backplate 19 and a nut 40 threaded onto the end portion 38.
  • connections to the low frequency voice coil 24 are provided by means of flexible leadout conductors 41 extending from the voice coil 24 to external connectors 42.
  • Connections to the high frequency voice coil 36 are provided by flexible conductors 43 which extend along a recess in the outer wall of the pot 30, between the pot 30 and the inner pole 20 and thence through the bore 26 to external connectors (not shown).
  • the rod 37 In order to allow the conductors to extend through the bore 26, the rod 37 has a diameter smaller than that of the bore 26 so as to leave an annular space through which the conductors 43 extend.
  • Means, not shown, are provided between the pole piece 20 and the pot 28 to ensure that the rod lies co-axially with the bore 26.
  • This means may be a disc secured to the pole piece 20 and having a central aperture of a diameter to receive the rod 37 in a sliding fit.
  • the disc may be grooved to provide a passageway for the conductors 43 between the pole piece 20 and the pot 28.
  • the rod 37 may be of circular, hexagonal or other section and the disc would be provided with a central aperture of matching shape.
  • a rod 37 of diameter smaller than that of the bore 26 if the rod is of hexagonal section its diameter may be of a size such that the rod is a sliding fit in the bore 26 to locate the high frequency drive unit co-axially of the pole piece 20 of the low frequency drive unit. Spaces between the faces of the hexagonal section rod and the wall of the bore 26 provide passageways for the conductors 43.
  • a moulding may be used. The moulding would be located by means of a boss on the moulding entering the bore 26. The moulding may be so formed as to provide a mounting for other components such as the electronic components of a cross-over filter and terminals for electrical drive signals for the compound loudspeaker drive unit.
  • the end 38 of the rod 37 being externally threaded, the end of the rod may be bored and threaded internally to receive a screw.
  • the construction described hereinbefore is particularly convenient in manufacture of the compound loudspeaker drive unit in that the high frequency drive unit is centralised relative to the low frequency drive unit prior to the high frequency drive unit reaching its final rest position on the pole piece 20. As a result the high frequency unit is prevented from engaging the low frequency voice coil during assembly of the compound loudspeaker drive unit. Furthermore this construction facilitates dis-assembly of the high frequency drive unit from the low frequency drive unit if and when any servicing of the units is necessitated without any need to demagnetise either of the magnetic assemblies.
  • annular baffle 44 having a frusto-conical front surface is secured to the front of the high frequency drive unit to provide a continuation of the surface of the low frequency diaphragm 21 towards the domed high frequency diaphragm.
  • the apparent sound source or acoustic centre of the high frequency drive unit is substantially co-incident with the apparent sound source or acoustic centre of the low frequency drive unit.
  • the radiation pattern or directivity of the low frequency drive unit is determined inter alia by the form of the low frequency diaphragm.
  • both drive units have substantially similar patterns of radiation or directivity.
  • the relative sound contributions from the two drive units as perceived by a listener are substantially unaffected by the listener being positioned at off axis positions.
  • the low frequency conical diaphragm is shown in the drawing as being of conical form having an angle of flare which increases from the neck of the diaphragm toward the outer periphery of the diaphragm.
  • the diaphragm may be of conical form having a uniform angle of flare.
  • the low frequency conical diaphragm may be of circular, elliptical or other section as desired.
  • the high frequency diaphragm is shown in the drawing as being of domed form. Such a diaphragm is suitable because its acoustic centre may readily be located in close coincidence with that of the low frequency diaphragm, and because, in the frequency range where both drive units contribute significant sound output, its small size relative to wavelength gives it, by itself, essentially non-directional sound radiation, allowing the effective directivity to be determined by the low frequency diaphragm. It will be appreciated that the high frequency diaphragm may alternatively be of any other form that provides these characteristics.

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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)
  • Liquid Crystal (AREA)
  • Piezo-Electric Transducers For Audible Bands (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)
  • Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)

Claims (7)

1. Lautsprecherkombinationseinheit, mit einer konischen ersten Membrane (21) für tiefe Frequenzen, die sich von einem Halsabschnitt der Membrane aus nach aussen und vorn erweitert, zum Erzeugen von Schall in einem tiefen Frequenzbereich; mit einer am Halsabschnitt der konischen Membrane befestigten ersten Schwingspule (24); mit einer kalottenförmigen zweiten Membrane (34) für hohe Frequenzen, zum Erzeugen von Schall in einem hohen Frequenzbereich; mit einer zweiten Schwingspule (36), die an einem Umfangsrand der Membrane für hohe Frequenzen befestigt ist; wobei die Membrane für hohe Frequenzen in oder bei dem Halsabschnitt der konischen Membrane (21) angeordnet ist; und mit Magnetmitteln (17, 18, 19, 20, 28, 29, 30, 32) mit einem ersten und einem zweiten Luftspalt, in welche sich die erste bzw. die zweite Schwingspule erstrecken, welche Magnetmittel im ersten Luftspalt einen ersten, mit der ersten Schwingspule zusammenwirkenden Magnetfluss und im zweiten Luftspalt einen zweiten, mit der zweiten Schwingspule zusammenwirkenden Magnetfluss erzeugen und welche Magnetmittel eine erste Magnetstruktur (17, 18, 19, 20) mit einem ersten Permanentmagnet (17) enthalten, der den ersten Magnetfluss in einem ersten Magnetflussweg durch die erste Magnetstruktur und den ersten Luftspalt erzeugt; dadurch gekennzeichnet, dass die Membrane (21) für tiefe Frequenzen und die Membrane (34) für hohe Frequenzen dazu ausgelegt sind, den tiefen und den hohen Schallfrequenzbereich sich in einem Uebergangsbereich überlappend zu erzeugen, wobei beide Membranen im Uebergangsbereich signifikante Beiträge zum erzeugten Schall liefern; dass die Magnetmittel ferner eine zweite Magnetstruktur (28, 29, 30, 32) mit einem zweiten Permanentmagnet (29) enthalten, der den zweiten Magnetfluss in einem zweiten Magnetflussweg durch die zweite Magnetstruktur und den zweiten Luftspalt erzeugt, wobei der zweite Magnetflussweg vom ersten Magnetflussweg getrennt ist; und dass der zweite Permanentmagnet (29) aus einem Material besteht, dessen magnetische Eigenschaften denjenigen einer Neodym-Eisen-Bor-Verbindung gleichwertig oder überlegen sind, so dass für eine erforderliche Grösse des Magnetflusses im zweiten Luftspalt die zweite Magnetstruktur die gleiche Grösse oder eine kleinere Grösse als eine Magnetstruktur mit einem Neodym-Eisen-Bor-Magnet hat und die zweite Magnetstruktur genügend klein ist, um innerhalb der ersten Schwingspule (24) benachbart zum Halsabschnitt der ersten Membrane (21) in einer solchen Stellung aufgenommen zu werden, dass die effektiven akustischen Zentren der ersten und der zweiten Membrane zusammenfallen und dass im Uebergangsbereich die sich erweiternde Form der konischen ersten Membrane (21) auf die Schallabstrahlung von der zweiten Membrane (34) eine Richtwirkung ausübt, wodurch die Richteigenschaften der ersten und der zweiten Membrane bei Frequenzen im Uebergangsbereich, wo beide Membranen signifikante Beiträge zum von der Kombinationseinheit abgegebenen Schall liefern, aneinander angepasst sind.
2. Lautsprecherkombinationseinheit nach Anspruch 1, dadurch gekennzeichnet, dass der zweite Permanentmagnet (29) aus Neodym-Eisen-Bor besteht.
3. Lautsprecherkombinationseinheit nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die erste Membrane (21) sich mit einem vom Halsabschnitt zu einem vorderen Umfangsrand der Membrane progressiv grösser werdenden Erweiterungswinkel nach aussen erweitert.
4. Lautsprecherkombinationseinheit nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass die Schwingspule (24) für tiefe Frequenzen auf einem Spulenformer (23) getragen ist, der am Halsabschnitt der konischen Membrane (21) für tiefe Frequenzen befestigt ist, dass die Schwingspule (24) für tiefe Frequenzen in einem Abstand hinter dem Halsabschnitt der konischen Membrane (21) für tiefe Frequenzen liegt und dass die zweite Magnetstruktur (28, 29, 30, 32) innerhalb des Spulenformers (23) zwischen dem Halsabschnitt und der Schwingspule für tiefe Frequenzen angeordnet ist.
5. Lautsprecherkombinationseinheit nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, dass die erste Magnetstruktur (17, 18, 19, 20) und die erste Membrane (21) eine erste vorgefertigte Einheit bilden; dass die zweite Magnetstruktur (28,29, 30, 32) und die zweite Membrane (27) eine von der ersten vorgefertigten Einheit getrennte zweite vorgefertigte Einheit bilden; dass die erste Magnetstruktur ein zentrales Polstück (20) mit einer zentralen Bohrung (26) enthält, die sich axial durch das Polstück erstreckt, und dass die zweite Magnetstruktur (28, 29, 30, 32) einen Stab (37) aus nichtmagnetischem Material enthält, der sich nach hinten in die genannte Bohrung (26) erstreckt und die zweite Magnetstruktur bezüglich der ersten Magnetstruktur zentriert.
6. Lautsprecherkombinationseinheit nach Anspruch 5, dadurch gekennzeichnet, dass die zweite Magnetstruktur (28, 29, 30, 32) an einer vorderen Stirnfläche des zentralen Polstücks (20) der ersten Magnetstruktur befestigt ist.
7. Lautsprecherkombinationseinheit nach Anspruch 5 oder 6, dadurch gekennzeichnet, dass Leiter (43), welche elektrische Verbindungen mit der zweiten Schwingspule (36) herstellen, sich zwischen einer Wand der zentralen Bohrung (26) und dem Stab (37) durch die zentrale Bohrung erstrekken.
EP89304569A 1988-05-09 1989-05-05 Lautsprecher Expired - Lifetime EP0341926B2 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8810943 1988-05-09
GB888810943A GB8810943D0 (en) 1988-05-09 1988-05-09 Loudspeaker

Publications (3)

Publication Number Publication Date
EP0341926A1 EP0341926A1 (de) 1989-11-15
EP0341926B1 true EP0341926B1 (de) 1994-12-07
EP0341926B2 EP0341926B2 (de) 2001-02-07

Family

ID=10636585

Family Applications (1)

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EP89304569A Expired - Lifetime EP0341926B2 (de) 1988-05-09 1989-05-05 Lautsprecher

Country Status (12)

Country Link
EP (1) EP0341926B2 (de)
JP (1) JP2766862B2 (de)
KR (1) KR0171567B1 (de)
AT (1) ATE115352T1 (de)
AU (1) AU3558189A (de)
CA (1) CA1339519C (de)
DE (1) DE68919746T3 (de)
ES (1) ES2065988T3 (de)
GB (2) GB8810943D0 (de)
HK (1) HK71893A (de)
NZ (1) NZ229054A (de)
WO (1) WO1989011201A1 (de)

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CA2352732A1 (en) * 2000-07-11 2002-01-11 Philip Jeffrey Anthony Compound loudspeaker drive unit having a magnet system
GB2364847B (en) * 2000-07-11 2004-10-13 Kef Audio Compound loudspeaker having a magnet system
GB2368484B (en) * 2000-10-25 2004-06-16 B & W Loudspeakers Distributed mode panel type loudspeakers
AU2002216597B2 (en) * 2000-12-26 2007-05-10 Anders Sagren Concentric co-planar multiband electro-acoustic converter
ITVI20030041A1 (it) * 2003-03-03 2004-09-04 Alessandro Riccobono Diffusore acustico a colonna.
WO2009109228A1 (en) * 2008-03-05 2009-09-11 Genelec Oy Nested compound loudspeaker drive unit
DE102008049560B3 (de) * 2008-09-30 2010-07-01 Kuhnke Automotive Gmbh & Co. Kg Elektrischer Schwingungserreger
GB2471884A (en) 2009-07-17 2011-01-19 Gp Acoustics Loudspeaker driver surround with at least one stiffening tab
EP2457382B1 (de) * 2009-07-24 2013-09-11 TP Vision Holding B.V. Tonwiedergabesystem
GB2474853B (en) 2009-10-27 2014-01-01 Gp Acoustics Uk Ltd Loudspeakers
FR2955444B1 (fr) * 2010-01-15 2012-08-03 Phl Audio Systeme de haut-parleur coaxial a chambre de compression
FR2955447B1 (fr) * 2010-01-15 2012-08-03 Phl Audio Transducteur electrodynamique comprenant un guide d'ondes acoustiques assurant une dissipation thermique
FR2955446B1 (fr) * 2010-01-15 2015-06-05 Phl Audio Transducteur electrodynamique a dome et suspension flottante
FR2955445B1 (fr) 2010-01-15 2013-06-07 Phl Audio Transducteur electrodynamique a dome et suspension interne
CN110830891B (zh) * 2018-08-07 2021-05-07 深圳市宝业恒实业股份有限公司 一种大功率自分频全频扬声器

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Also Published As

Publication number Publication date
DE68919746T2 (de) 1995-04-20
ES2065988T3 (es) 1995-03-01
WO1989011201A1 (en) 1989-11-16
CA1339519C (en) 1997-10-28
GB2236929A (en) 1991-04-17
ATE115352T1 (de) 1994-12-15
NZ229054A (en) 1992-03-26
GB2236929B (en) 1992-11-04
AU3558189A (en) 1989-11-29
EP0341926B2 (de) 2001-02-07
KR0171567B1 (ko) 1999-03-30
EP0341926A1 (de) 1989-11-15
GB8810943D0 (en) 1988-06-15
JP2766862B2 (ja) 1998-06-18
KR900702744A (ko) 1990-12-08
JPH03504310A (ja) 1991-09-19
DE68919746D1 (de) 1995-01-19
DE68919746T3 (de) 2001-06-13
GB9023490D0 (en) 1991-01-09
HK71893A (en) 1993-07-30

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