EP0339425B1 - Lautsprechersystem - Google Patents

Lautsprechersystem Download PDF

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Publication number
EP0339425B1
EP0339425B1 EP19890106833 EP89106833A EP0339425B1 EP 0339425 B1 EP0339425 B1 EP 0339425B1 EP 19890106833 EP19890106833 EP 19890106833 EP 89106833 A EP89106833 A EP 89106833A EP 0339425 B1 EP0339425 B1 EP 0339425B1
Authority
EP
European Patent Office
Prior art keywords
sound
speaker system
absorbing member
sound absorbing
acoustic path
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
EP19890106833
Other languages
English (en)
French (fr)
Other versions
EP0339425A3 (en
EP0339425A2 (de
Inventor
Tadashi Tamura
Shuji Saiki
Kazue Sato
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.)
Panasonic Holdings Corp
Original Assignee
Matsushita Electric Industrial Co 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
Priority claimed from JP63106355A external-priority patent/JPH0775431B2/ja
Priority claimed from JP63109343A external-priority patent/JPH0775432B2/ja
Application filed by Matsushita Electric Industrial Co Ltd filed Critical Matsushita Electric Industrial Co Ltd
Priority to EP19890106833 priority Critical patent/EP0339425B1/de
Publication of EP0339425A2 publication Critical patent/EP0339425A2/de
Publication of EP0339425A3 publication Critical patent/EP0339425A3/en
Application granted granted Critical
Publication of EP0339425B1 publication Critical patent/EP0339425B1/de
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 
    • H04R1/30—Combinations of transducers with horns, e.g. with mechanical matching means, i.e. front-loaded horns
    • 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

  • the present invention relates to a speaker system having a horn or an acoustic pipe provided in front of the speaker diaphragm and adapted for guiding sonic waves therefrom.
  • a speaker system in which a sound wave generated by a diaphragm is introduced to the second outlet opening of the speaker through a horn or an acoustic pipe provided on the front side of the diaphragm.
  • This type of speaker systems is finding increasingly wide use because it provides a higher level of the output sound pressure and superior directivity as compared with ordinary speaker systems which do not have such a horn or acoustic pipe.
  • a back cavity 2 is provided on the rear side of a speaker unit 1 for the purpose of preventing radiation of reflected sound from the speaker diaphragm.
  • a horn 9 is provided in front of the speaker diaphragm and extends towards the sound outlet opening of the speaker system. The cross-sectional area of the horn 9 is progressively increased from the end adjacent to the speaker diaphragm towards the end adjacent to the sound outlet opening of the speaker system. The horn 9 thus constitutes an acoustic path 5 which introduces the sound wave output from the speaker.
  • the change in the acoustic impedance at the sound outlet opening of the speaker system is made extremely small provided that the horn 9 has a length which is sufficiently greater than the length of the wavelengths of sound wave of the reproduction band.
  • a very good matching is obtained at the sound outlet opening of the speaker system so that a flat reproduction sound pressure frequency characteristic is obtained thus realizing an ideal speaker system.
  • the speaker systems employing such horns usually exhibit a reproduction sound pressure frequency characteristic which contains many peaks and troughs as shown in Figs. 2B and 8B.
  • the British Patent Specification GB-A-402 600 discloses a speaker system in which a speaker unit is mounted with its diaphragm in an opening of the front wall of the speaker unit.
  • the rear side of the diaphragm is disposed at the beginning of an acoustic path of a predetermined, relatively large length and of flaring shape.
  • the acoustic path is defined by a sound absorbing member made of a sound absorbing material filling the space between the surface thereof defining the acoustic path and the sidewalls of the speaker system chamber.
  • the effect of the sound absorbing member is that the length of the path by which the sound waves are guided from the rear side of the diaphragm may be made relatively long without introducing appreciable selective box resonance effects due to reflections from the sidewalls of the chamber.
  • Japanese Patent Unexamined Publication No. 49-134312 discloses a speaker system in which a horn for guiding the sound wave from a diaphragm is made from a material which exhibits a small tendency of generation of reflected waves (noise), i.e., a material which absorbs the noise well. This, however, is irrelevant to the invention of this application which is intended for absorbing reflected waves attributable to a drastic change in the acoustic impedance at the sound outlet opening of the speaker system.
  • an object of the present invention is to provide a speaker system having flat sound pressure frequency characteristics free of resonance peaks and troughs without requiring that the length of the horn or the acoustic pipe is increased.
  • a speaker system comprising: at least one speaker unit having a diaphragm; an acoustic path for guiding sound waves generated on the front surface of said diaphragm; and a sound absorbing member made of a sound absorbing material provided in a predetermined portion of said acoustic path; wherein said acoustic path is defined by said sound absorbing member and wherein a partition member is disposed to separate said sound absorbing member from said acoustic path in such a manner that at least a portion of said sound absorbing member is exposed to said acoustic path.
  • a known speaker system has a speaker unit 1 with a back cavity 2 on the rear side thereof, an acoustic pipe 3 for guiding and introducing sound waves generated on the front side of the diaphragm of the speaker unit 1, and a sound absorbing member 4 disposed in the acoustic pipe 3 and defining an acoustic path 5.
  • this speaker system is as follows.
  • the sound emitted from the rear side of the speaker unit 1 is confined in the back cavity 2 so that it is not transmitted to the outside of the speaker system.
  • the sound emitted from the front side of the diaphragm is introduced through the acoustic pipe 3 to the sound outlet opening of the speaker system so as to be radiated therefrom.
  • a part of the sound wave introduced to the sound outlet opening is reflected due to a drastic change in the acoustic impedance, tending to propagate backward to the diaphragm surface.
  • the reflected sound wave is conveniently absorbed by the sound absorbing material disposed in the acoustic pipe, thus eliminating existence of a standing wave in the acoustic pipe.
  • the sound absorbing member 4 has a smaller thickness in the region near the sound outlet opening and a greater thickness at the region adjacent to the speaker unit 1, so that the impedance of the sound absorbing member 4 to the reflected wave is reduced to ensure a high sound absorbing effect.
  • the amount of the material of the sound absorbing member 4 is increased towards the front side of the diaphragm so that the impedance exhibited by the sound absorbing member 4 to the reflected sound wave is linearly changed, whereby the reflected sound wave from the sound outlet opening is effectively absorbed by the sound absorbing member without any unnecessary reflection.
  • the linear and progressive change in the impedance provided by the sound absorbing member may be controlled in various ways. For instance, it is possible to control the manner of change in the impedance by suitably varying the amount of the material of the sound absorbing member 4 along the length thereof, or by adjusting the flow resistance per unit area such that it is small in the region near the sound outlet opening and large in the region near the surface of the diaphragm.
  • the sound wave produced by the diaphragm can be introduced to the sound outlet opening through the acoustic path defined by the sound absorbing member 4 without being impeded by the sound absorbing member 4.
  • Fig. 2 illustrates the reproduction sound pressure frequency characteristics exhibited by a speaker system with the horn or acoustic pipe of Fig. 1, in comparison with the characteristics exhibited by another conventional arrangement. From this Figure, it will be understood that the other conventional speaker system exhibits characteristics B which includes peaks and troughs due to existence of a standing wave, while the known speaker system of Fig. 1 exhibits flat reproduction sound pressure frequency characteristics A up to high pitch region of the tone.
  • the cross-sectional area of the acoustic path is increased from the end adjacent to the surface of the diaphragm towards the sound outlet opening.
  • Such an acoustic path 5 may be defined solely by the sound absorbing member 4 as shown in Fig. 3(a) or, alternatively, the arrangement may be such that the sound absorbing member 4 and the wall of the acoustic pipe 3 in cooperation define the acoustic path 5, as shown in Fig. 3(b).
  • the acoustic path 5 may have a tubular form of a constant cross-sectional area, or it may have, as in Fig. 3(c), an arrangement in which the sound absorbing member 4 has a horn-like form, while the acoustic pipe 3 is constructed to decrease its cross-sectional area towards the sound outlet opening, thus providing a constant cross-sectional area of the acoustic path 5, as shown in Fig. 3(c).
  • Fig. 4 is a sectional view of a first embodiment of the speaker system in accordance with the present invention.
  • the first embodiment of the speaker system has a speaker unit 1, a back cavity 2, an acoustic pipe for introducing acoustic waves generated on the front side of the diaphragm, a partition member 6 disposed in the acoustic pipe 3 so as to define an acoustic path 5, and a sound absorbing member 4 a part of which is disposed between the partition member 6 and the wall of the acoustic pipe 3 while the other part is exposed so as to define the acoustic path 5.
  • the operation of the first embodiment is as follows.
  • the sound wave emitted from the rear side of the diaphragm in the speaker unit 1 is confined in the back cavity 2 so that it does not radiate to the outside.
  • the sound wave emitted from the front side of the diaphragm is guided by the acoustic pipe 3 to reach the sound outlet opening so as to be radiated therefrom.
  • a drastic change in the acoustic impedance is generated in the sound outlet opening, a portion of the sound wave introduced to the opening is reflected so as to be propagated backward towards the front surface of the diaphragm.
  • the reflected wave is absorbed by the sound absorbing member 4 disposed in the acoustic pipe 3, so that no standing wave exists in the acoustic pipe 3.
  • the partition member 6 is so sized as to extend over about 1/3 of the acoustic pipe 3 as measured from the surface of the diaphragm, and is intended to effectively guide the high-pitch components of the sound which tend to be absorbed by the sound absorbing member 4.
  • the portion of the acoustic pipe 3 which is about 1/3 the whole length of the acoustic pipe 3 as measured from the surface of the diaphragm substantially coincides with the region where the particle velocity is high. It is therefore possible to suppress the peaks of the sound pressure in the frequency region in which the standing wave is generated.
  • the sound wave components of other frequencies are introduced efficiently to the sound outlet opening without being impeded by the sound absorbing member, because the sound absorbing member is designed in the form of a horn.
  • the first embodiment can be carried out with various forms of the acoustic path 5 as illustrated in Figs. 3(a) to 3(c), without impairing the advantages derived therefrom.
  • Fig. 5 shows a second embodiment of the speaker system of the present invention.
  • the second embodiment has a speaker unit 1, a back cavity 2, an acoustic pipe 3 for guiding sound wave generated on the front side of the diaphragm in the speaker unit 1, a partition member 6 disposed in the acoustic pipe 3 so as to define an acoustic path 5 and having slits one of which is located near the sound outlet opening of the acoustic pipe 3 while the other is in the region which is about 1/3 of the full length of the acoustic pipe 3 as measured from the surface of the speaker diaphragm, and a sound absorbing material received in the space between the acoustic pipe 3 and the partition member 6.
  • the operation of the speaker system in accordance with the second embodiment is as follows.
  • the sound wave emitted from the rear side of the speaker unit 1 is confined in the back cavity 2 so that it does not radiate outside.
  • the sound from the front side of the diaphragm in the speaker unit 1 is guided by the acoustic pipe 3 to reach the sound outlet opening so as to be radiated therefrom.
  • a portion of the sound wave reaching the sound outlet opening is reflected because the acoustic impedance is drastically changed at the sound outlet opening.
  • the reflected wave tends to propagate backward towards the surface of the diaphragm.
  • the reflected wave is effectively absorbed by the sound absorbing member 4 in the acoustic pipe 3 so that no standing wave is generated in the acoustic pipe.
  • the partition member 6 has slits in the region near the sound outlet opening and in the region which is 1/3 of the full length of the acoustic pipe 3 as measured from the surface of the speaker diaphragm, i.e., in the regions where the particle velocity is high. It is therefore possible to selectively absorb the sound wave components of frequency regions having peaks of sound pressure. Other components of the sound wave can be guided to the sound outlet opening without being impeded by the sound absorbing member 4.
  • the second embodiment also provides flat sound pressure frequency characteristics, by suppressing the peaks of sound pressure which are inevitably high in the known horn or acoustic pipe due to the presence of a standing wave.
  • Figs. 6(a) and 6(b) show a third embodiment of the speaker system in accordance with the present invention.
  • the third embodiment has a speaker unit 1, a back cavity 2, an acoustic pipe 3 which guides the sound wave generated on the front side of the diaphragm of the speaker unit 1, a partition member 6 disposed in the acoustic pipe 3 so as to define an acoustic path 5 and having a plurality of apertures, and a sound absorbing member 4 filling the space between the wall of the acoustic pipe 3 and the partition member 6.
  • the apertures 10 formed in the partition member 6 have a diameter of 8 mm and are arranged at a pitch of 30 mm.
  • the operation of the third embodiment of the speaker system will be described hereinunder.
  • the sound emitted from the rear side of the diaphragm of the speaker unit 1 is confined in the back cavity 2 so that it does not radiate to the outside.
  • the sound wave emitted from the front side of the diaphragm is guided to the sound outlet opening through the acoustic pipe 3 so as to be radiated therefrom.
  • a portion of the sound wave reaching the sound outlet opening of the acoustic pipe 3, however, is reflected to propagate backward towards the front surface of the diaphragm, because a drastic change in the acoustic impedance takes place at the sound outlet opening.
  • the reflected sound wave is absorbed by the sound absorbing member 4 which continuously extends over the entire area of the inner surface of the acoustic pipe 3 so that establishment of standing wave in the acoustic pipe 3 is prevented.
  • the partition member 6 has apertures 10 of 8 mm diameter arranged at a pitch of 30 mm.
  • the reflected sound wave causes a resonation with the air in the apertures so that a large sound absorption rate is obtained in the region near 1 KHz, thus enabling absorption of the second peak of the sound pressure in the acoustic pipe 3 which has a length of 40 cm.
  • Other peaks are directly absorbed by the sound absorbing member 4 rather than by resonance with the air in the apertures.
  • the diameter and the pitch of the apertures 10 can be varied as desired to enable absorption of the peak of a variety of frequency regions.
  • the configuration of the acoustic path 5 may be varied as illustrated in Figs. 3(a) to 3(c), without imparing the advantages.
  • Fig. 7 shows a fourth embodiment of the speaker system in accordance with the present invention.
  • This embodiment has a high-pitch tone speaker unit 7, a low-pitch tone speaker 8, a back cavity 2, an acoustic pipe 3 for guiding the sound waves generated on the front surfaces of both speaker units 7 and 8, a partition member 6 disposed in the acoustic pipe 3 so as to define an acoustic path 5 and having slits one of which is located near the sound outlet opening of the acoustic pipe 3 while the other is in a region which is about 1/3 of the full length of the acoustic pipe as measured from the end surface of the diaphragm in the speaker unit, and a sound absorbing member 4 disposed in the space defined between the wall of the acoustic pipe 3 and the partition member 6.
  • the operation of the speaker system in accordance with the fourth embodiment is as follows.
  • the sound waves emitted from the rear side of the high-pitch and low-pitch tone speaker units 7 and 8 are confined in the back cavity 2 so that it does not radiate outside.
  • the sound waves from the front side of the diaphragm in the speaker units 7 and 8 are guided by the acoustic pipe 3 to reach the sound outlet opening so as to be radiated therefrom.
  • a portion of the sound waves reaching the sound outlet opening is reflected because the acoustic impedance is drastically changed at the sound outlet opening.
  • the reflected wave tends to propagage backward towards the surface of the diaphragm.
  • the reflected wave is effectively absorbed by the sound absorbing member 4 in the acoustic pipe 3 so that no standing wave is generated in the acoustic pipe.
  • the partition member 6 has slits in the region near the sound outlet opening and in the region which is 1/3 of the full length of the acoustic pipe 3 as measured from the surface of the speaker diaphragm, i.e., in the regions where the particle velocity is high. It is therefore possible to selectively absorb the sound wave components of frequency regions having peaks of sound pressure. Other components of the sound wave can be guided to the sound outlet opening without being impeded by the sound absorbing member 4.
  • Fig. 8 illustrates the reproduction sound pressure frequency characteristics exhibited by a speaker system with the horn or acoustic pipe in accordance with the fourth embodiment, in comparison with the characteristics exhibited by the conventional arrangement. From this Figure, it will be understood that the conventional speaker system exhibits characteristics B which includes peaks and troughs due to existence of a standing wave, while the speaker system of the fourth embodiment exhibits flat reproduction sound pressure frequency characteristics A up to high pitch region of the tone.
  • the fourth embodiment also provides flat sound pressure frequency characteristics, by suppressing the peaks of sound pressure which are inevitably high in the known horn or acoustic pipe due to the presence of a standing wave.

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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 (12)

  1. Lautsprechersystem, das aufweist: Mindestens eine Lautsprechereinheit (1) mit einem Diaphragma; einen akustischen Kanal (5) zum Leiten von auf der Vorderseite des Diaphragmas erzeugten Schallwellen; und ein schallabsorbierendes Element (4) aus einem schallabsorbierenden Material in einem vorbestimmten Abschnitt des akustischen Kanals; wobei der akustische Kanal (5) von dem schallaborbierenden Element (4) definiert ist, dadurch gekennzeichnet, daß ein Abteilelement (6) derart zum Trennen des schallabsorbierenden Elements (4) von dem akustischen Kanal angeordnet ist, daß zumindest ein Teil des schallabsorbierenden Elements (4) zu dem akustischen Kanal (5) hin freiliegt.
  2. Lautsprechersystem nach Anspruch 1, dadurch gekennzeichnet, daß der freiliegende Teil des schallabsorbierenden Elements (4) nahe den Resonanzpunkten stehender Wellen in dem akustischen Kanal (5) liegt.
  3. Lautsprechersystem nach Anspruch 1, dadurch gekennzeichnet, daß sich das Abteilelement (6) von der Vorderseite des Diaphragmas zu einer Stelle hin erstreckt, die von der Vorderseite des Diaphragmas um etwa 1/3 der Gesamtlänge des akustischen Kanals (5) beabstandet ist.
  4. Lautsprechersystem nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß derjenige Bereich, wo das schallabsorbierende Element (4) freiliegt, ein Bereich ist, wo die Partikelgeschwindigkeitsverteilung stehender Wellen in dem akustischen Kanal groß ist.
  5. Lautsprechersystem nach Anspruch 4, dadurch gekennzeichnet, daß schallabsorbierende Element (4) in einem Bereich freiliegt, der von der Vorderseite des Diaphragmas um etwa 1/3 der Gesamtlänge des akustischen Kanals beabstandet ist, und in einem Bereich, der nahe der Schallauslaßöffnung des akustischen Kanals (5) liegt.
  6. Lautsprechersystem nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die Querschnittsfläche des akustischen Kanals (5) progressiv von dem Ende nahe dem Diaphragma zu dem Ende nahe der Schallauslaßöffnung hin zunimmt.
  7. Lautsprechersystem nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß der akustische Kanal (5) eine konstante Querschnittsfläche über seine gesamte Länge hat.
  8. Lautsprechersystem nach einem der Ansprüche 6 und 7, dadurch gekennzeichnet, daß der akustische Kanal (5) durch die Wand des schallabsorbierenden Elements (4) und die Wand einer akustischen Röhre (3) definiert ist.
  9. Lautsprechersystem nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, daß der akustische Kanal (5) gemeinsam auf der Vorderseite einer Vielzahl Lautsprechereinheiten (7, 8) vorgesehen ist.
  10. Lautsprechersystem nach einem der Ansprüche 1 bis 9, dadurch gekennzeichnet, daß das schallabsorbierende Element (4) in einer akustischen Röhre (3) vorgesehen ist.
  11. Lautsprechersystem nach einem der Ansprüche 1 bis 10, dadurch gekennzeichnet, daß die Menge des Materials des schallabsorbierenden Elements (4) progressiv von dem Ende nahe dem Diaphragma zu dem Ende nahe der Schallauslaßöffnung hin abnimmt.
  12. Lauptsprechersystem nach einem der Ansprüche 1 bis 11, dadurch gekennzeichnet, daß der Strömungswiderstand pro Einheitsfläche des schallabsorbierenden Elements (4) progressiv von dem Ende nahe dem Diaphragma zu dem Ende nahe der Schallauslaßöffnung hin abnimmt.
EP19890106833 1988-04-28 1989-04-17 Lautsprechersystem Expired - Lifetime EP0339425B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP19890106833 EP0339425B1 (de) 1988-04-28 1989-04-17 Lautsprechersystem

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
JP106355/88 1988-04-28
JP63106355A JPH0775431B2 (ja) 1988-04-28 1988-04-28 スピーカシステム
JP63109343A JPH0775432B2 (ja) 1988-05-02 1988-05-02 スピーカシステム
JP109343/88 1988-05-02
EP19890106833 EP0339425B1 (de) 1988-04-28 1989-04-17 Lautsprechersystem

Publications (3)

Publication Number Publication Date
EP0339425A2 EP0339425A2 (de) 1989-11-02
EP0339425A3 EP0339425A3 (en) 1990-01-24
EP0339425B1 true EP0339425B1 (de) 1994-03-23

Family

ID=26446466

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19890106833 Expired - Lifetime EP0339425B1 (de) 1988-04-28 1989-04-17 Lautsprechersystem

Country Status (5)

Country Link
EP (1) EP0339425B1 (de)
BR (1) BR8901979A (de)
DK (1) DK170195B1 (de)
ES (1) ES2050178T3 (de)
MX (1) MX171080B (de)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2325586B (en) * 1995-03-14 1999-01-13 Matsushita Electric Ind Co Ltd Speaker system
GB2302231B (en) * 1995-03-14 1999-01-13 Matsushita Electric Ind Co Ltd Speaker system
DE19611999C1 (de) * 1996-03-27 1997-07-17 Henkel Kgaa Verfahren zur Herstellung alkoxylierter Fettsäurealkylester
US6008391A (en) * 1997-03-17 1999-12-28 Henkel Kommanditgesellschaft Auf Aktien Process for preparing alkoxylated fatty acid alkyl esters
DE19909272A1 (de) 1999-03-03 2000-09-07 Cognis Deutschland Gmbh Verfahren zur Herstellung alkoxylierter nichtionischer Tenside
GB2464512B (en) * 2008-10-16 2012-11-28 Instigate Media Ltd A sound source
US11310587B2 (en) 2019-10-08 2022-04-19 Bose Corporation Horn loudspeakers

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB402600A (en) * 1931-11-27 1933-12-07 Harold Lister Kirke Improvements in or relating to loudspeakers
GB496504A (en) * 1937-06-25 1938-12-01 Murphy Radio Ltd Improvements in loud speakers
GB963853A (en) * 1961-12-29 1964-07-15 Wharfedale Wireless Works Ltd Loudspeakers
DE1537620A1 (de) * 1967-11-14 1969-12-18 Isophon Werke Gmbh Trichterlautsprecheraggregat
NZ225001A (en) * 1987-06-16 1990-09-26 Matsushita Electric Ind Co Ltd Loudspeaker: reflected sound waves absorbed

Also Published As

Publication number Publication date
DK170195B1 (da) 1995-06-06
BR8901979A (pt) 1989-12-05
EP0339425A3 (en) 1990-01-24
DK204589D0 (da) 1989-04-27
ES2050178T3 (es) 1994-05-16
EP0339425A2 (de) 1989-11-02
MX171080B (es) 1993-09-29
DK204589A (da) 1989-10-29

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