US3679833A - Loudspeaker system - Google Patents

Loudspeaker system Download PDF

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Publication number
US3679833A
US3679833A US842161A US3679833DA US3679833A US 3679833 A US3679833 A US 3679833A US 842161 A US842161 A US 842161A US 3679833D A US3679833D A US 3679833DA US 3679833 A US3679833 A US 3679833A
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sound
propagating
axis
loudspeaker
coil
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US842161A
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Kiyoshi Inoue
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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
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/32—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only
    • 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
    • H04R9/06—Loudspeakers
    • H04R9/063—Loudspeakers using a plurality of acoustic drivers
    • 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

  • ABSTRACT A loudspeaker system having an electrooacoustical transducer and a sound-propagating member with at least a principal sound-emitting axis.
  • the sound director is movable to swing the axis through an angle to its normal position and thereby change the sound distribution accordingly.
  • Stereophonic efvfects and changes in the quality of the tone (expression) are audible to the listener.
  • the angle control may be effected independently of the electrical signal source or in dependence thereupon.
  • the present invention relates to a loudspeaker and, more particularly, to loudspeaker systems designed to vary the quality of the audible signal.
  • Stereophonic sound reproduction generally involves the conversion of an electrical signal representing a prerecorded audible signal, a radio-frequency transmission, a currently presented transmission (e.g. from a microphone) or the like, the loudspeakers each being formed with an electroacoustical transducer to convert the electrical signal into a vibratory output which, of course, constitutes a sound signal audible to the listener.
  • the loudspeakers For proper stereophonic effect, a clear demarcation must be maintained between the channels, i.e. the channels of pick-up, recording and amplification, the loudspeaker for the two or more channels must be properly spaced and oriented so that a balanced sound reaches the ear of the listener from distinct, separated sources.
  • loudspeakers are basically static members with limited audible depth of interest. As a result, the loudspeaker may lack expression, in certain instances, thereby rendering the sound produced unpleasant.
  • the quality of the audited sound remains poor in many instances since the stereophonic recording or reproduction is often made from a mechanical recording the signals of which have been discriminated and separated to permit recording to two tracks with, for example, one being dominated by a high frequency, while the other is dominated by the low-frequency portion of the sound spectrum derived from an original recording.
  • the principal object of the present invention to provide an improved loudspeaker system which is of low cost and yet can provide effects close to the stereophonic or, at any rate, improve the quality of the sound, depth, etc., directed at the listener.
  • Another object of the instant invention is to provide a single-speaker system capable of producing stereophonic and depth effects and avoiding the monotony usually prevalent in single-speaker arrangements.
  • Yet another object of this invention is to provide a system for applying expression" to the sound emitted from a loudspeaker.
  • a further object of the instant invention is to provide an improved sound-propagating loudspeaker system capable of responding to signals dependent upon the electroacoustical signals and/or signals independent thereof.
  • a loudspeaker system having an electroacoustical transducer and a sound-directing portion or member defining a sound-propagating axis, and means for displacing this axis, preferably to opposite sides thereof in a controlled manner and, generally, relative to the electroacoustical portion of the loudspeaker.
  • an actual soundpropagating axis which includes an angle with the normal position of the axis and, desirable with another position of the axis so as to principally direct the sound, say, first to one side, then to the other side of the normal position of the axis.
  • Displacement can involve swinging movement of the sounddirecting member, i.e. wherein the axis oscillates back and forth in a single plane in a pendulum type of motion, or oscillatory motion'about a pivot in a given plane or in one of a number of predetermined planes; also the motion may be gyratory or orbital.
  • the displacement of the sound-directing member may also be effected, in accordance with this invention, such that the axis is swept about a closed path along any desired configuration, e.g. a circle, such that the path of the displaced axis defines a conical surface.
  • any desired configuration e.g. a circle
  • Other displacement variations will, of course, be immediately apparent.
  • the sound-directing member is a cone diaphragm, the sound-propagation axis of which normally lies centrally of this cone and preferably coincides therewith.
  • the cone may be composed of flexible material and may form part of the electroacoustical transducer, e.g. by virtue of a coil mounted upon the narrow part of the cone and cooperating with a stationary permanent magnet disposed adjacent the coil.
  • the permanent magnet may be provided on the diaphragm-type cone, while the coil is fixed in place on the housing or yoke of the loudspeaker.
  • the sound-directing member may also be constituted by a horn or like member which is pivotal about an axis located at the intersection point of the normal sound-propagating axis and the offset or displaced axis and the movement of this sound-directing member can be effected by means of an electrical motor or the like with ease. It will be apparent, however, that in all cases the sound-directing member can be moved without displacing the entire assembly in the corresponding direction and that a system in which only the nonhousing portions are displaced is preferred.
  • the means displacing the sound-propagating axis of the loudspeaker may include electroacoustical, electrostatic or electric-motor means. depending upon the availability of such means only.
  • the oscillatory motion of the sound-propagating axis is effected periodically, e.g. by the use of an electric signal from a periodic source, or aperiodically with a random-signal genera tor or a signal depending upon one or more of the parameters ofthe signal feeding the voice coil ofthe unit.
  • the control ofthe swing of the axis may thus result from discrimination of amplitudes in the applied signals. i.e. the oscillation will occur only upon the development of high-amplitude signals.
  • a frequency discrimination may also be used such that, for example, a loudspeaker will be rotated to the right or to the left with respect to its normal axis in response to a predominance of high-frequency and a predominance of lowfrequency signals, respectively.
  • FIG. I is an axial cross-sectional view through a loudspeaker embodying the present invention.
  • FIG. 2 is a similar cross-sectional view showing a modified embodiment thereof
  • FIG. 2A is an enlarged detail view, somewhat exaggerated, showing a different positions of the sound-propagating element
  • FIG. 3 is a cross section taken along the line III III of FIG.
  • FIG. 4 is an axial cross-sectional view through still another loudspeaker in accordance with this invention.
  • FIG. 4A is a cross section taken along the line IV-IV of FIG. 4;
  • FIG. 5 is a circuit diagram in which the oscillation of the sound-propagating axis of the unit is controlled in step with the amplitude of the acoustical signal;
  • FIG. 6 is a circuit diagram of a three-channel arrangement embodying the present invention and wherein the cone diaphragm may have gyratory motion;
  • FIG. 7 is a diagrammatic view of another loudspeaker embodying this invention.
  • FIG. 8 is a circuit diagram, partly in block form, illustrating additional features of the invention.
  • a loudspeaker in accordance with this invention, may be of dynamic type wherein a moving coil is energized to coact with a permanent magnet or a dc energized magnet.
  • the loudspeaker of FIGv 1 has a housing 1, 1a, the latter portion of which frustoconically diverges from the iron magnetically permeable yoke I whose center post lb is coaxially surrounded by a flange Id to which the cone la is affixed and lb.
  • the iron body I thus acts as a magnetic armature or core as represented by the dot-dash line 1e in FIG.
  • the outer periphery 3a of the cone 3 is provided with accordion pleats to lend flexibility to the diaphragm and permit canting between the dot-dash line positions shown in FIG. 1.
  • the free end of the bellows is attached at 3b to the mouth If of the conical housing member Ia.
  • the cylindrical portion 30 of member 3 has a bottom wall 3d lying in a plane perpendicular to the post lb in its normal position, and unitarily running into the cylindrical portion 30 formed with the coil 4. Since the wall member 3a is rigid with the post lb along its inner periphery, the application of normal signal levels may result merely in an axial reciprocation of the diaphragm as represented by the arrows 3e. When, however, very high signals are produced, a canting of the diaphragm 3 occurs as shown in broken lines in FIG. 2A. In practice, it has been found that best results are attainable when the diaphragm is designed so as to be pivotal or swingable through an angle :0 of 30 to 40 as shown in FIG. 1.
  • FIGS. 2 and 3 Show an embodiment of the present invention in which a rolling motion may be imparted to the principal sound-propagating axis so that oscillation is permitted in accordance with a resultant force and may, therefore, be random in nature.
  • a cone-shaped nonmovable member may be provided as is shown at la in FIG. 1 to hold the outer edge of the diaphragm cone 203 by its bellowspleated periphery 2031:.
  • the yoke has a central post 2011: cooperating with an axially positioned permanent magnet 202a closely surrounded by the axially extending cylindrical portion 203: of the conical member 203.
  • the cylindrical portion 2030 carries the voice or sound coil as previously noted.
  • a cylindrical wall 201d accommodating the cylindrical portion 203 with clearancev Outwardly of this cylindrical wall 201d, I provide the massive body of the yoke with bores 251a, 252a, 253a and 25411 receiving respective posts 201b' cooperating with coil sleeves 251-254.
  • the coil sleeves 251-254 are each connected with a corresponding point of diaphragm 203 as represented by the connecting rods 251a and 25lb.
  • coil 203c will cause the latter and the diaphragm 203 to oscillate in the usual manner, i.e. generally axially, along the path of sound propagation and, of course, in the direction in which such propagation is desired.
  • FIG. 5 shows a system which makes use of the amplitude of intensity of the sound-generating signal to cant, tilt or swing the diaphragm and, in general, to change the orientation of its major sound-propagating axis.
  • the control circuit in FIG. 5. which may be connected to the coils 251-254 of FIG. 2 (these coils being represented at 51-54 in FIG. 5), comprises input terminals 7 to which an electric signal, e.g. derived from a radio receiver, a tape recorder, a microphone or the like. is connected; an amplifier 8 is fed by terminals 7.
  • the amplified output may be a much lower frequency or the same frequency of amplified intensity in the frequency-response range of the speaker 300.
  • the speaker 300 has a cone 303 which is pivotally mounted or is swingable relative to the yoke 401 as described in connection with FIG. 4.
  • Each of the coils 5l-54 has an armature 51' and 54' (FIG. 5) coupled with the sound emitting diaphragm 303.
  • the signals appearing at the output terminals of the amplifier 8 are applied to the sound coil 304 directly or via an output transformer; whereas the same terminals are bridged across a rectifying network 9, the output of which feeds the amplifier 10 a frequency-modulation unit with an internally generated carrier is connected to amplifier 10, the latter providing the modulating signal.
  • a phase circuit 12 (phase discriminator) breaks the mudulated signal down into components associated with the respective amplitude levels and applies these signals to these respective coils 51-54.
  • the rectifying network 9 comprises a pair of oppositely poled rectifying diodes 9a, 912, respectively in series with breakdown devices such as the Zener diodes 9c and 9d.
  • the rest of the bridge is formed by a pair of resistors 9e and 9f so that only the signals remaining after clipping by the Zeners are amplified at 10 and passed along the circuit chain.
  • the microphone when the circuit of FIG. 7 is used in a microphone arrangement, for example, the microphone is connected to the terminals 7 and its acoustoelectrical transducer produces an electric output proportional to the sound input, the output being delivered to the coils 304 and the rectifying network 9. Below a predetermined amplitude level established by the Zener diodes 9c and 9d, there is no output across the bridge 9a 9f and thus no modulation in the axial orientation of the sound-directing member of the loudspeaker.
  • the signal appearing across the bridge is amplified at 10, used as the modulating wave at 11, is subjected to phase discrimination at 12 with the individual output being applied to the coils 51-54 to swing the axis in one direction or another and thereby reduce any raucous phenomenon and lend greater depth and expression to the sound.
  • FIGS. 4 and 4A show still another embodiment of my invention.
  • This embodiment comprises a housing whose rigid frustoconical housing member 401a is provided with an axially extending rim 401g and with a ledge 40111 to which the periphery 403b of diaphragm 403 is secured.
  • the cone 403 is coupled via rods 4510 with armatures 451b along the exterior of which lie the coils 404.
  • the coils 404 cooperate with the permanent magnets 402 in the posts 401d and are shifted axially as represented by the arrows upon energization of these coils.
  • FIG. 6 there is shown a control circuit which may be used for the reproduction of sterophonic music and other audio signals.
  • three pickup coils are provided and induce or generate a driving potential across the pickup coils which are respectively connected to the drive coil 61-63 with or without intervening modulation or amplification.
  • the amplifiers 141 143, shown in FIG. 6, merely represent any of a number of effective amplifier arrangements which may be employed ifdesired.
  • FIG. 7 there is shown a modification in which a horntype loudspeaker 503, provided with an electroacoustical transducer at 504 is pivotally mounted at 565 so as to swing clockwise or counterclockwise under the control of a gear sector 566 whose teeth 566a mesh with the teeth 566b at the rear end of the speaker.
  • a motor 567 is coupled with the gear sector 566 to rotate same.
  • FIG. 8 there is shown a system which makes use of some of the principles previously described.
  • a speaker 601 and a speaker 701 the former being of the dynamic type and having an oscillatory and cantable sound-emitting cone 603 whose normal axis is shown at A in H0. 8.
  • the member 603 is, for the sake of clarity in this diaphragm, shown to be suspended between a pair of restoring springs 670 and to cooperate with a voice or sound introduction coil 671.
  • the latter may be energized by a switch 672 from a conventional amplifier 673 and the terminal 674.
  • the coils 604 are mechanically connected to the speaker cones 603 as represented by the dot-dash lines, may be energized by any ofthree systems as set out below.
  • switch 772 When switch 672 is open, switch 772 is closed, the switch 772 connecting the amplifier 673 with the speaker 701 whose voice coil is represented at 704 and whose swingable horn 703 is driven by a motor 704a.
  • the motor 7040 has a pair of oppositely effective coils which are energized when switches 772 and 672 are respectively closed and opened.
  • switch 675 When switch 675 is closed, it connects an adjustable AC source 677 to the coil 604 or the coil 704, depending upon which of the ganged switches 678, 679, 680 and 681 are open or closed. These switches may also be ganged when only one-speaker operation is desired. Source 677 applies a low-frequency periodic shift of the axis of the loudspeakers.
  • An amplitude-sensitive circuit as shown at 690 in FIG. 8 and as described in greater detail in connection with FIG. 5, may be brought into play when switch 691 is closed and switches 75 and 692 are open.
  • Another circuit which may be used with the present invention is that illustrated in a block diagram at 695.
  • the amplified output signal (from amplifier 673) is fed via switch 692 to a pair of filters such as the high pass and low pass filters shown at 696 and 697 respectively.
  • the cone swings in response to frequency rather than amplitude.
  • the system described above is an improved loudspeaker arrangement which achieves a stereophonic effect with a single speaker unit.
  • a loudspeaker system comprising electroacoustical transducer means including a housing and at least one soundgenerating coil in said housing energizable with an electrical signal to produce acoustical vibrations. and means including a cone vibrated by said coil for propagating said acoustical vibrations along the axis of said cone, said coil being anchored at one end to said housing; and a mechanism including an oscillation-producing coil in said housing in addition to said sound-generating coil for oscillating said cone relative to said housing without displacement of said housing whereby the sound-propagating axis is swung out of a normal position during the course of sound transmission by the loudspeaker.
  • a loudspeaker system comprising electroacoustical transducer means energizable with an electrical signal to produce acoustical vibration, and means for propagating said acoustical vibration in a predetermined direction; and an arrangement for oscillating said means whereby the sound-propagating axis is swung out of a normal position during the course of sound transmission by the loudspeaker, said transducer means including a sound-generating coil energizable with said electrical signal to produce said acoustical vibration, a plurality of electromagnetic coils independent of said sound-generating coil and angularly equispaced about the axis of propagation of the system and armature means axially displaceable by said electromagnetic coils and operatively connected with said means for propagating said acoustical vibration.
  • a loudspeaker system comprising electroacoustical transducer means including sound-generating coil means energizable with an electrical signal to produce acoustical vibration. and means for propagating said acoustical vibrations in a predetermined direction; an arrangement for oscillating said means whereby the sound-propagating axis is swung out of a normal position during the course of sound transmission by the loudspeaker; and a housing enclosing said electroacoustical transducer means, said arrangement including electromagnetic coil means for oscillating said means for propagating said acoustical vibrations without shifting of said housing, said electromagnetic coil means being independent of said soundgenerating coil means.
  • a loudspeaker system comprising electroacoustical transducer means energizable with an electrical signal to produce acoustical vibration; means for propagating said acoustical vibrations in a predetermined direction; an arrangement for oscillating said means whereby the sound-propagating axis is swung out of a normal position during the course of sound transmission by the loudspeaker; a housing formed with an iron yoke and a frustoconical housing portion extending from said yoke; at least one permanent magnet mounted in said yoke and forming part of said transducer means; a voice coil received in said yoke and cooperating with said permanent magnet, said means for propagating said acoustical vibrations including a diaphragm cone anchored to said voice coil and formed with an accordion-pleated peripherally affixed to said housing portion; and an array of angularly equispaced direction-changing coils received in said yoke and provided with respective
  • a loudspeaker system comprising electroacoustical transducer means energizable with an electrical signal to produce acoustical vibration; means for propagating said acoustical vibrations in a predetermined direction; an arrangement for oscillating said means whereby the sound-propagating axis is swung out of a normal position during the course of sound transmission by the loudspeaker; a housing having a yoke and a rigid housing portion of frustoconical configuration extending outwardly from said yoke; an angularly equispaced array of direction-changing coils received in said yoke and each having an armature; and a diaphragm forming said means for propagating said acoustical vibrations and connected to said armatures for displacement thereby, not all of said directionchanging coils being energized simultaneously.
  • a loudspeaker system comprising electroacoustic transducer means energizable with an electrical signal to produce acoustical vibration; directing means including at least one coil for propagating said acoustical vibration in a predetermined direction; and an arrangement coupled with said directing means for controlledly varying the direction of said acoustic vibration with the axis of said propagation shified from a normal position during the course of sound transmission by the loudspeaker, said arrangement including directioncontrol means with another coil in addition to said one coil, said direction-control means being coupled with said directing means for oscillating said axis of sound propagation in a single plane past said normal position in a direction generally orthogonal to said predetermined direction and with an amplitude as a function of a parameter of said electrical signal.
  • a loudspeaker system comprising electroacoustic transducer means energizable with an electrical signal to produce acoustical vibration; direction means for propagating said acoustical vibration in a predetermined direction; and an arrangement coupled with said directing means for controlledly varying the direction of said acoustic vibration with the axis of such propagation shifted from a normal position during the course of sound transmission by the loudspeaker, said ar rangement including direction-control means coupled with said directing means for oscillating said axis of sound propagation past said normal position in a direction generally orthogonal to said predetermined direction and with an amplitude as a function of a parameter of said electrical signal, second direction-control means coupled with said directing means for oscillating said axis of sound propagation past said normal position and in a second direction generally orthogonal both to said predetermined and first directions, and actuator means for actuating said first and second direction-control means whereby the pattern of sound propagation follows a given trajectory related to the
  • a loudspeaker system comprising electroacoustic transducer means energizable with an electrical signal to produce acoustical vibration; directing means for propagating said acoustical vibration in a predetermined range of direction; and an arrangement coupled with said directing means for controlledly varying the direction of said acoustical vibration with the axis of sound propagation shifted generally randomly within said range during the course of sound transmission by said loudspeaker, said arrangement including a plurality of direction-control means selectively actuat able by the respective actuation signals to selectively shift and sweep the axis of sound propagation in accordance therewith.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Electrophonic Musical Instruments (AREA)
  • Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
US842161A 1968-07-18 1969-07-16 Loudspeaker system Expired - Lifetime US3679833A (en)

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JP43050692A JPS4811888B1 (enrdf_load_stackoverflow) 1968-07-18 1968-07-18

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2408239A1 (fr) * 1977-11-07 1979-06-01 Ibm Moteur a bobines mobiles multiples et independantes et son application dans une memoire a disques
US4438297A (en) 1980-11-28 1984-03-20 Hitachi, Ltd. Dynamic speaker
US4464785A (en) * 1983-04-08 1984-08-07 Charles N. K. Cluxton Loudspeaker system
EP0804048A3 (de) * 1996-04-26 2004-07-14 Harman Audio Electronic Systems GmbH Lautsprecher
US20060188120A1 (en) * 2005-02-23 2006-08-24 Michael Fisher Multiple active coil speaker
US20060204028A1 (en) * 2005-03-11 2006-09-14 Samsung Electronics Co., Ltd. Speaker apparatus
US20110255717A1 (en) * 2010-04-14 2011-10-20 Beijing Funate Innovation Technology Co., Ltd. Digital sound projector
WO2014072299A1 (en) * 2012-11-08 2014-05-15 Ask Industries Societa' Per Azioni Electro-magnetic transducer and vibration control system
US20160127839A1 (en) * 2007-09-26 2016-05-05 Harman Becker Gepkocsirendszer Gyarto Korlatolt Felelossegu Tarsasag Acoustic transducer
CN105578361A (zh) * 2016-03-01 2016-05-11 广东欧珀移动通信有限公司 一种用于扬声器的磁路结构及扬声器

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5586265U (enrdf_load_stackoverflow) * 1978-12-06 1980-06-14
JPH02126258U (enrdf_load_stackoverflow) * 1989-03-29 1990-10-17

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2551556A (en) * 1945-09-12 1951-05-01 E D Mccurdy Acoustic diaphragm with plural voice coil supports
US3022853A (en) * 1958-07-14 1962-02-27 Rototone Inc Swiveling acoustical apparatus

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2551556A (en) * 1945-09-12 1951-05-01 E D Mccurdy Acoustic diaphragm with plural voice coil supports
US3022853A (en) * 1958-07-14 1962-02-27 Rototone Inc Swiveling acoustical apparatus

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2408239A1 (fr) * 1977-11-07 1979-06-01 Ibm Moteur a bobines mobiles multiples et independantes et son application dans une memoire a disques
US4438297A (en) 1980-11-28 1984-03-20 Hitachi, Ltd. Dynamic speaker
US4464785A (en) * 1983-04-08 1984-08-07 Charles N. K. Cluxton Loudspeaker system
EP0804048A3 (de) * 1996-04-26 2004-07-14 Harman Audio Electronic Systems GmbH Lautsprecher
US20060188120A1 (en) * 2005-02-23 2006-08-24 Michael Fisher Multiple active coil speaker
US7813521B2 (en) * 2005-03-11 2010-10-12 Samsung Electronics Co., Ltd. Speaker apparatus
US20060204028A1 (en) * 2005-03-11 2006-09-14 Samsung Electronics Co., Ltd. Speaker apparatus
CN1832635B (zh) * 2005-03-11 2011-12-28 三星电子株式会社 扬声器装置
US20160127839A1 (en) * 2007-09-26 2016-05-05 Harman Becker Gepkocsirendszer Gyarto Korlatolt Felelossegu Tarsasag Acoustic transducer
US9807518B2 (en) * 2007-09-26 2017-10-31 Harman Becker Gepkocsirendszer Gyarto Korlatolt Felelossegu Tarsasag Acoustic transducer
US20110255717A1 (en) * 2010-04-14 2011-10-20 Beijing Funate Innovation Technology Co., Ltd. Digital sound projector
US8538047B2 (en) * 2010-04-14 2013-09-17 Beijing Funate Innovation Technology Co., Ltd. Digital sound projector
WO2014072299A1 (en) * 2012-11-08 2014-05-15 Ask Industries Societa' Per Azioni Electro-magnetic transducer and vibration control system
CN105578361A (zh) * 2016-03-01 2016-05-11 广东欧珀移动通信有限公司 一种用于扬声器的磁路结构及扬声器

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