EP0155266B1 - Lautsprecherstruktur - Google Patents

Lautsprecherstruktur Download PDF

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Publication number
EP0155266B1
EP0155266B1 EP19830903131 EP83903131A EP0155266B1 EP 0155266 B1 EP0155266 B1 EP 0155266B1 EP 19830903131 EP19830903131 EP 19830903131 EP 83903131 A EP83903131 A EP 83903131A EP 0155266 B1 EP0155266 B1 EP 0155266B1
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EP
European Patent Office
Prior art keywords
sphere
tweeter
structure according
transducer structure
woofer
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
Application number
EP19830903131
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English (en)
French (fr)
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EP0155266A1 (de
EP0155266A4 (de
Inventor
Henry Oliver Wolcott
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Individual
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Individual
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Publication date
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Publication of EP0155266A1 publication Critical patent/EP0155266A1/de
Publication of EP0155266A4 publication Critical patent/EP0155266A4/de
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Expired legal-status Critical Current

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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
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/28—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means
    • H04R1/2807—Enclosures comprising vibrating or resonating arrangements
    • H04R1/2861—Enclosures comprising vibrating or resonating arrangements using a back-loaded horn
    • H04R1/2865—Enclosures comprising vibrating or resonating arrangements using a back-loaded horn for loudspeaker transducers
    • 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
    • H04R1/34—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by using a single transducer with sound reflecting, diffracting, directing or guiding means
    • H04R1/345—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by using a single transducer with sound reflecting, diffracting, directing or guiding means for loudspeakers

Definitions

  • This invention pertains to electro-acoustical transducer structures, particularly the acoustic aspects thereof.
  • SoundSpan Speaker Systems of B.I.C/AVNET, Westbury, N.Y., employ three transducers; a woofer pointing ("firing") downward, a mid-range transducer employing a horn, and a treble transducer also employing a horn. These transducers are positioned coaxially one above the other in the order recited; the latter two transducers firing upward.
  • the sound-emitting elements being stacked coaxially vertically, an away-from-the-wall placement of the loudspeaker would be required to give the intended omnidirectional lateral sound fidelity. However, if placed against a wall the backwardly-directed sound conflicts with the direct sound, and an irregular amplitude vs. frequency characteristic occurs.
  • An alternate embodiment merely doubles the structure vertically and employs two identical cone loudspeakers.
  • a further alternate embodiment assembles two of the initial structures, with one of them inverted, so that two cone loudspeakers are employed, one up-firing and one down-firing.
  • the four-sided pyramid causes a four-leaf clover horizontal dispersion of sound.
  • the vertical pattern of the loudspeaker is not enhanced.
  • tweeters are not employed at all, save for a further embodiment in which a tweeter is disposed off-axis but "- in alignment with a ridge -" of a pyramid. This causes a two-only (opposed) cloverleaf for the high frequencies involved.
  • the art has been wont to combine plural loudspeakers, up to six per unit of a stereo pair of loudspeakers, typically by merely firing the sound outward from the cabinet that supports the loudspeakers, but does not shape the sound pattern thereof.
  • loudspeaker units in an enclosure that "colors" the sound by having a predominant resonant frequency. This causes the sound to have the characteristic of a particular musical instrument, rather than a uniform characteristic of amplitude vs. frequency that is suited to reproduce all musical instruments and voice with fidelity.
  • US-A-3500953 discloses a loudspeaker structure in which a cone loudspeaker in an enclosure is directed upwardly at a curved surface, whose orientation affects the distribution of radiated sound.
  • FR-A-2163600 discloses a loudspeaker structure having a fixed sphere whose vertical axis is colinear with a speaker axis, and whose loudspeakers are of the cone type.
  • At least one up-firing woofer is surmounted by a sound-reflecting sphere, which, in turn, is surmounted by a down-firing tweeter having a dome radiator, with the sound waves thereof impinging upon the same sphere.
  • This configuration provides omni-directional sound, both horizontally and vertically.
  • a hemispherical horizontal and vertical pattern is obtained, such as is desirable if the loudspeaker structure is to be placed against the wall of a room.
  • One embodiment includes a downwardly extending horn within the structure housing the woofer.
  • the horn is front-firing. It is folded.
  • a truncated plural-sided pyramid is employed to house the woofer. No two sides thereof are parallel. The sides are stiffened to prevent acoustic vibration.
  • Fig. 1 is a perspective view of the loudspeaker structure showing the disposition of the principal components.
  • Fig. 2 is a perspective view of an alternate embodiment of the loudspeaker structure in which a base horn is utilized.
  • Fig. 3 is a vertical sectional view of the structure of Fig. 2 along lines 3 - 3, showing the construction of the folded base horn, in section.
  • Fig. 4 is a fragmentary perspective view of the base of Fig. 1, in which an auxiliary baffle radiator (ABR) is employed.
  • ABR auxiliary baffle radiator
  • the slant of all of the sides of truncated pyramid 1 is typically 1 in 6, i.e., for each 6 centimeters (cm) of height the surface is inwardly inclined 1 cm.
  • the structure of this invention can be embodied in different sizes.
  • the criterion is determined by the acoustic parameters, which must be properly inter-related. This is further set forth below.
  • a typical size for the base pyramid is 70 cm high, with a width at the bottom of 54 cm and at the top of 40 cm.
  • the base pyramid is supported incrementally above the floor on four feet, elements 2, each having a height of approximately 9 cm.
  • the bottom of the base is closed by a rigid surface 10 that is inclined with respect to the horizontal truncated surface top, typically with a slant of 2 in 6.
  • Acoustic ports preferably three ducted ports 3, are provided. These are hollow cylinders extending into the interior volume of the base, typically being 9 cm in diameter by 15 cm in length.
  • edges of the top of the base pyramid are rounded with an approximately 2 cm radius to prevent sharp-edge acoustic diffraction.
  • Physical support for sphere 4 and tweeter 5 is provided by typically four vertical members, as metal angles 6. These extend from the bottom of base pyramid 1 to a four-arm spider 7 at the top of the structure. Part way up two horizontal members 8 are individually fastened to an adjacent pair of vertical angles 6 to support sphere 4 at the extremities of a horizontal diameter thereof. Preferably two hollow rods that are internally threaded at each end pass through holes in the sphere and receive screws that slide in slot 9 in the horizontal member for the support of the sphere. This allows a forward and back adjustment of the position of the sphere.
  • Angles 6 each have a quarter-round wood inner surface to provide a rounded surface for preventing acoustic diffraction.
  • rounded metal tubes may be substituted for angles 6 to prevent acoustic diffraction.
  • the embodiment of Fig. 1 has four woofers, 12, 12', 12", 12'", symmetrically disposed in the upper surface of the truncated base structure 1. These are electrically connected in parallel and are the equivalent of one large woofer. Each of the four may have a diameter of approximately 15 cm, and be the long-throw type TP165F, of which Peerless Audio Manufacturing Corp. is a manufacturer. The acoustic range is from approximately 30 hertz to 5,000 hertz.
  • Tweeter 5 has a 3 cm dome radiator and an external diameter of approximately 12 cm with a vertical cylindrical length of 3 cm.
  • the central circular portion of spider 7 is also approximately 12 cm so that edge acoustic diffraction is minimal.
  • the four arms of the spider are each approximately 3 cm high by 1.5 cm thick.
  • the inventive effort is to minimize any structure around the tweeter, so that it approaches the effect of being suspended in vacant space.
  • the tweeter range is from 1 kilohertz to 20 kilohertz, and may be the soft dome type of Audax, of France,, type HD13D34H.
  • the relative placements of the woofer, sphere and tweeter are determined by acoustic considerations.
  • the structure of this invention allows a large advance in acoustic fidelity by maintaining coherency in amplitude and phase of the sound over the whole range of sound reproduced, and in all directions from the loudspeaker.
  • the inertia of the larger moving system of the woofer is greater than that of the smaller moving system of the tweeter. Accordingly, when a step function waveform, such as from tap dancing, is impressed upon both loudspeakers the sound is emitted first from the tweeter and second from the woofer. Although the interval between the two sounds may be only a fraction of a millisecond, the effect is discernible. The effect can be eliminated by spacing the tweeter farther from the sphere than the woofer, in the present novel structure.
  • the difference in the spacing is determined by the dynamic characteristics of the two speakers involved. It is constant for those speakers.
  • the vertical position of the sphere can be fixed for a given pair of speakers. For the speakers previously identified, the vertical position is 29 cm from the diaphram of the tweeter to the center of the sphere and 25 cm from the woofers to the center of the sphere. Considering the reflection areas on the sphere for the tweeter and the woofer, this amounts to 2.58 cm difference in path length. If this was not taken into consideration, at the cross-over frequency of 2000 hertz a phase difference of 54° would exist. This is undesirable for impulse sounds.
  • Loudspeakers are invariably operated in a room, such as the living room of a family residence. Under such conditions the sound heard by a listener is that directly from the loudspeaker, and that reflected from the walls, ceiling and floor of the room.
  • acoustic testing carried on by the inventor prior to the invention of the present loudspeaker structure revealed that although the direct sound from the usual loudspeaker might have a smooth amplitude response characteristic as a function of frequency, that characteristic from the sides of the loudspeaker had numerous "hills and valleys" and was the very opposite to a smooth response. The same was true for the characteristic from the rear of the loudspeaker, usually with a different set of hills and valleys.
  • a uniform spherical pattern in both horizontal and vertical planes is desired and is secured by locating the sphere coaxially with respect to both the tweeter and the woofer.
  • a stereophonic (“stereo") signal sound source is provided and two of the present loudspeaker structures are used, spaced one from the other by a few meters.
  • the loudspeaker structure(s) When the loudspeaker structure(s) are to be placed against a wall of a room it is desirable to limit the horizontal sound directional pattern to a hemisphere; i.e., to the free space in front of the wall.
  • the upper audio frequencies in the woofer range such as at the crossover frequencies, typically from 1,000 to 3,000 hertz, are given some directivity by the position of the sphere, similar to the tweeter frequencies.
  • low audio frequencies such as 100 hertz and below, are notoriously non-directional, but this does not affect the performance of the loudspeaker structure of this invention.
  • the positions of the woofer and tweeter may not be interchanged.
  • the sound from the tweeter reaches the ceiling of the room and destroys the otherwise "point source" of the loudspeaker structure as previously described.
  • the base truncated pyramid must then be inconlicly above the sphere, and floor loading of the base frequency ports is absent.
  • Another undesirable modification is to position the ducted ports 3 on a side of the truncated enclosure 1, rather than at the bottom. Measurements show that a loss of low frequency response occurs, amounting to over 30% of the lower limit response over that obtained with the ports in the bottom of the truncated enclosure. The greater phase lag of the low frequencies out of the bottom ports because of the greater distance from the woofer is believed responsible for the improvement.
  • auxiliary baffle radiator (ABR) may be made in the bottom of the truncated enclosure with results approaching those obtained with the ducted ports 3.
  • the ABR is a flat resiliently mounted stiff diaphram, in this instance about 30 cm in diameter, 11.
  • the sphere is typically hollow and of glass, or an equivalent very hard substance, such as ceramic or a glass-like plastic. Wood and similar soft substances are not satisfactory. With translucent glass or equivalent, a light-emitting element,such as light bulb 30, can be contained within the sphere and the same thereby illuminated. Music-controlled lamps may also be utilized.
  • While the true sphere is a preferred shape, this may be modified to an elongated "sphere", having the major axis vertical. This accomplishes functioning according to this invention by reason of providing increased extreme side projection when in the recessed position with the loudspeaker structure against a wall due, to the acoustic geometry involved.
  • FIG. 2 An example of another preferred embodiment of the subject invention is shown in Fig. 2.
  • a distinguishing feature is an internal folded horn in the base truncated pyramid 21, having a forward-opening mouth 20.
  • a single large woofer 22 such as the type LR1280C of Professional Audio Systems, a California corporation, is disposed in the top horizontal surface of the truncated pyramid base.
  • the downward emission of sound therefrom passes through horn 20, while the upward emission of sound passes to sphere 24, which typically is the same as prior sphere 4.
  • the woofer-sphere-tweeter relationship is as before. To illustrate the two prime positions that the sphere can occupy, forward and back; sphere 4 is shown in the back position, while sphere 24 is shown in the forward, or vertically coaxial position.
  • top edges of truncated pyramid 21 are rounded with a 3 cm radius to prevent sound diffraction, as has been previously explained.
  • Typical dimensions for the embodiment of Fig. 2 are; for the truncated pyramid, 77 cm high, 69 cm on a side at the bottom, and 43 cm on a side at the top.
  • the tweeter is 53 cm above the top surface of the truncated pyramid, and is 30 cm above the center of the sphere, which is again 36 cm in diameter.
  • spider arms 27 are of minimal cross-section and the diameter of that structure around the tweeter is not greater than that of the tweeter itself.
  • the opening of horn 20 extends totally across the bottom of truncated pyramid 21 and is 30 cm high by 65 cm wide in the embodiment of Fig. 2.
  • the horn is formed of baffles within the truncated pyramid, as shown in Fig. 3. When thus formed the length of the horn is approximately 215 cm.
  • First baffle 35 is disposed at a downward slant of approximately 12° to the horizontal closely below the frame of woofer 22.
  • the baffle extends 75% of the distance from the front surface of the truncated pyramid base.
  • Second baffle 36 is disposed horizontally and extends 70% of the distance from the rear surface of the base.
  • Third baffle 37 is disposed at a downward slant of approximately 15° to the horizontal and extends 65% of the distance from the front surface of the base.
  • baffles extend completely from side to side of the base and are securely fastened thereto by glue or equivalent means.
  • stiffeners 41, 42, 43 extend from the rear corners at an approximate angle of 30° from the vertical and are fastened to horizontal stiffeners 38, 39, 40 respectively.
  • the latter are centrally located, side to side, and are individually rigidly attached to baffles 35, 36, 37, respectively.
  • the baffle and stiffener structure is typically fabricated of dense particleboard 1.2 cm thick, while the truncated pyramid base is 2 cm thick.
  • truncated pyramids illustrated herein have square bases. These are typical, but not essential, to the acoustic functioning of the invention.
  • geometrical definition a pyramid may have a triangular, square or polygonal base, and these variants may be herein employed.
  • An electro-acoustical transducer structure is, of course, a definitive term for a loudspeaker structure.
  • the input is electrical
  • the output is acoustical
  • the transducer is the device that accomplishes the transformation of energy from one form to the other.
  • Hardwood cross-braces 47 and 48 may be employed to give acoustic stiffness to base 1.

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  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)

Claims (13)

  1. Elektroakustische Wandlerstruktur, die umfaßt
    (a) mindestens einen Tieftonlautsprecher (12,22), der zum Abstrahlen des Schalles senkrecht nach oben ausgerichtet ist;
    (b) eine über dem Tieftonlautsprecher (12,22) angeordnete Schallreflexionskugel (4,24),
    (c) einen über der Kugel angeordneten Hochtonlautsprecher (5,25), der zum Abstrahlen des Schalles senkrecht nach unten ausgerichtet ist,
    (d) ein Grundgehäuse (1,21) mit näherungsweise pyramidenstumpfartiger Gestalt, bei der keine zwei Seiten parallel sind,
    (e) worin die Kugel (4,24) mit ihrer vertikalen Achse eine Lage einnimmt, die kolinear zur Achse zumindest des Hochtonlautsprechers oder in horizontaler Richtung von der Achse zumindest des Hochtonlautsprechers versetzt ist oder in solch eine versetzte Lage verstellbar ist, und
    (f) der Hochtonlautsprecher (5,25) einen Kalotten
    strahler aufweist.
  2. Wandlerstruktur nach Anspruch 1, bei der der Tieftonlautsprecher (22) und der Hochtonlautsprecher (25) koaxial angeordnet sind.
  3. Wandlerstruktur nach Anspruch 1 mit einer Vielzahl von Tieftonlautsprechern (12), die symmetrisch um eine vertikale Achse angeordnet sind, die koaxial zur Achse des Hochtonlautsprechers ist.
  4. Wandlerstruktur nach einem der Ansprüche 1 bis 3, bei der die Kugel (4,24) um etwa 30 % ihres Durchmessers in bezug zur Achse des Hochtonlautsprechers nach hinten versetzt ist.
  5. Wandlerstruktur nach einem der Ansprüche 1 bis 4, die zusätzlich innerhalb des Grundgehäuses (21) einen gefalteten Trichter (20) enthält, der seine Ausgangsöffnung auf der Vorderseite des Gehäuses hat.
  6. Wandlerstruktur nach Anspruch 5, in der der gefaltete Trichter (20) aus mehreren Schallwänden (35,36,37) gebildet ist, die abwechselnd je an entgegengesetzt liegenden Seiten des Grundgehäuses (21) angeordnet sind und sich quer über etwa 70 % des Innenraums des Grundgehäuses erstrecken, und wobei jede Schallwand eine zentral plazierte Versteifung (38,39,40) enthält, die sich quer durch den gesamten Innenraum des Grundgehäuses erstreckt.
  7. Wandlerstruktur nach Anspruch 6, die zusätzlich Bogenelemente (45) enthält, die in jeder durch eine Schallwand und eine Seite des Grundgehäuses, an der die Schallwand angeordnet ist, gebildeten Ecke montiert sind, um für den gefalteten Trichter an jeder dieser Ecken einen abgerundeten inneren Weg zu bilden.
  8. Wandlerstruktur nach einem der vorangegangenen Ansprüche, die zusätzlich Mittel (2) enthält, um stufenweise den Boden des Grundgehäuses über einem Fußboden zu erhöhen, sowie mehrere rohrförmige Akustikkörper (3), die im Boden des Grundgehäuses angeordnet sind.
  9. Wandlerstruktur nach Anspruch 8, bei der der Boden (10) zu einer mindestens einen Tieftonlautsprecher (12) tragenden Fläche in einem Winkel geneigt ist.
  10. Wandlerstruktur nach Anspruch 8 oder 9, bei der drei Akustikkörper vorgesehen sind.
  11. Wandlerstruktur nach einem der Ansprüche 1 bis 7, die einen zusätzlichen im Boden (10) des Grundgehäuses angeordneten Schallwandstrahler (11) enthält.
  12. Wandlerstruktur nach einem der vorangegangenen Ansprüche, die zusätzlich mehrere senkrechte, jeweils eine abgerundete Oberfläche aufweisende Elemente (6,26) enthält, Mittel um diese senkrechten Elemente am Grundgehäuse zu befestigen, Mittel (8,28), um die Kugel an den senkrechten Elementen zu befestigen, und Mittel (7,27), um den Hochtonlautsprecher an den senkrechten Elementen zu befestigen.
  13. Wandlerstruktur nach einem der vorangegangenen Ansprüche, bei der die Kugel (4,24) aus lichtdurchlässigem Material besteht und ein lichtaussendendes Element (30) innerhalb der Kugel angeordnet ist, um dessen äußere Oberfläche zu beleuchten.
EP19830903131 1983-09-06 1983-09-06 Lautsprecherstruktur Expired EP0155266B1 (de)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1983/001355 WO1985001176A1 (en) 1983-09-06 1983-09-06 Loudspeaker structure

Publications (3)

Publication Number Publication Date
EP0155266A1 EP0155266A1 (de) 1985-09-25
EP0155266A4 EP0155266A4 (de) 1988-01-28
EP0155266B1 true EP0155266B1 (de) 1991-03-20

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP19830903131 Expired EP0155266B1 (de) 1983-09-06 1983-09-06 Lautsprecherstruktur

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EP (1) EP0155266B1 (de)
DE (1) DE3382223D1 (de)
WO (1) WO1985001176A1 (de)

Families Citing this family (13)

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JPH0724439B2 (ja) * 1986-09-13 1995-03-15 シャープ株式会社 オ−デイオ装置
US5173942A (en) * 1986-09-13 1992-12-22 Sharp Kabushiki Kaisha Audio system operable in directional and non-directional modes
GB2213677A (en) * 1987-12-09 1989-08-16 Canon Kk Sound output system
FR2637147B1 (fr) * 1988-09-29 1990-12-28 Mutek Sarl Enceinte electro-acoustique omnidirectionnelle
DE3923126A1 (de) * 1989-07-13 1991-01-17 Stark Henric Lautsprecherbox
FR2673800B1 (fr) * 1991-03-07 1993-12-31 Lan Yan Fock Alain Dispositif electro-acoustique de reproduction sonore, asservi electroniquement, utilisant un haut-parleur a pavillon muni de microphones.
GB2256773A (en) * 1991-06-12 1992-12-16 Canon Res Ct Europe Ltd Loudspeaker uinit
DE9205731U1 (de) * 1992-04-29 1992-08-20 Schoor, Bodo, 3404 Adelebsen Lautsprecheranordnung
GB2310969B (en) * 1996-03-08 2000-05-03 Martin Audio Ltd Bass sound projection system
FR2829658B1 (fr) * 2001-09-07 2004-01-02 Franck Tchang Dispositif d'amplification et de purification du son
JP2004072140A (ja) * 2002-08-01 2004-03-04 Hiroshi China 全指向性バックロードホーン型スピーカー
US9930469B2 (en) 2015-09-09 2018-03-27 Gibson Innovations Belgium N.V. System and method for enhancing virtual audio height perception
JP6925234B2 (ja) * 2017-09-11 2021-08-25 シャープ株式会社 スピーカシステム、表示装置、テレビジョン装置

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US2108846A (en) * 1934-08-29 1938-02-22 Walter O Brown Radio cabinet
DE718134C (de) * 1938-05-22 1942-03-04 Lorenz C Ag Lautsprecheranordnung mit zwei Lautsprechern und pilzfoermiger Schallfuehrung
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US3477540A (en) * 1966-01-03 1969-11-11 Patron Alfonso R Speaker system
US3500953A (en) * 1968-12-04 1970-03-17 Uolevi L Lahti Loudspeaker system
US3816672A (en) * 1970-07-06 1974-06-11 K Peter Sound reproduction system
DE2162347A1 (de) * 1971-12-16 1973-06-20 Luebeck Fa Otto Vorrichtung zur wiedergabeverbesserten schallabstrahlung von lautsprechern
DE2325603A1 (de) * 1973-05-19 1974-12-05 Heger Harry Stand-box mit rundstrahlcharakteristik durch einen zerteiler-kegel
SE387512B (sv) * 1973-08-24 1976-09-06 S Carlsson Hogtalare for sterofonisk ljudatergivningsanleggning, samt av tva sadana hogtalare bestaende hogtalarpar
US4348549A (en) * 1978-02-06 1982-09-07 Emmanuel Berlant Loudspeaker system
US4249037A (en) * 1978-11-08 1981-02-03 Dexter John L Pyramid loudspeakers with twin cross-phased mid-range speakers
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US4365114A (en) * 1979-09-14 1982-12-21 Pioneer Electronic Corporation Automotive loudspeaker having variable speaker orientation and particular electrical connections
US4357490A (en) * 1980-07-18 1982-11-02 Dickey Baron C High fidelity loudspeaker system for aurally simulating wide frequency range point source of sound

Also Published As

Publication number Publication date
WO1985001176A1 (en) 1985-03-14
EP0155266A1 (de) 1985-09-25
EP0155266A4 (de) 1988-01-28
DE3382223D1 (de) 1991-04-25

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