EP0565369A2 - Lautsprecher - Google Patents

Lautsprecher Download PDF

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Publication number
EP0565369A2
EP0565369A2 EP93302752A EP93302752A EP0565369A2 EP 0565369 A2 EP0565369 A2 EP 0565369A2 EP 93302752 A EP93302752 A EP 93302752A EP 93302752 A EP93302752 A EP 93302752A EP 0565369 A2 EP0565369 A2 EP 0565369A2
Authority
EP
European Patent Office
Prior art keywords
transmission line
loudspeaker
driver
cabinet
cavity
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.)
Withdrawn
Application number
EP93302752A
Other languages
English (en)
French (fr)
Other versions
EP0565369A3 (en
Inventor
Martin Roberts
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.)
CELESTION INTERNATIONAL Ltd
Original Assignee
CELESTION INTERNATIONAL Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by CELESTION INTERNATIONAL Ltd filed Critical CELESTION INTERNATIONAL Ltd
Publication of EP0565369A2 publication Critical patent/EP0565369A2/de
Publication of EP0565369A3 publication Critical patent/EP0565369A3/en
Withdrawn legal-status Critical Current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; ELECTRIC HEARING AIDS; 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
    • H04R1/2853—Enclosures comprising vibrating or resonating arrangements using an acoustic labyrinth or a transmission line
    • H04R1/2857—Enclosures comprising vibrating or resonating arrangements using an acoustic labyrinth or a transmission line for loudspeaker transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers
    • H04R3/04—Circuits for transducers for correcting frequency response

Definitions

  • This invention relates to loudspeakers and loudspeaker systems and is particularly concerned with transmission line loudspeakers and loudspeaker systems.
  • Transmission line loudspeaker systems have traditionally consisted of a woofer or a combination of drivers mounted at the end of a long tube.
  • the simplest form of tube is a pipe of uniform diameter.
  • a resonance occurs (the "quarter-wave" resonance) such that the sound which is radiated from the open end of the tube reinforces that coming directly from the loudspeaker drive unit itself.
  • Higher up the frequency scale the tube will have more resonances, at roughly odd integer multiples of the quarter-wave resonance frequency, i.e. 3/4, 5/4, etc.
  • these modes are undesirable, because it is only the first mode which provides reinforcement.
  • the higher frequency modes either reinforce or cancel the direct output from the loudspeaker drive unit.
  • the first step is to introduce damping/absorption into the system.
  • the second is to change the shape of the pipe, notably its longitudinal profile.
  • absorbent material such as foam has a frequency-dependent attenuation characteristic, so that higher frequency modes are damped but not completely eliminated. Placing more absorbent material in the pipe does not help, because the first mode can then be damped out so much that the main advantage of using a transmission line is diminished.
  • one proposal is to introduce a taper, so that the diameter of the pipe decreases in the direction from the loudspeaker drive unit towards the open end of the pipe.
  • a tapered pipe has almost the same acoustic characteristics at low frequencies as a pipe of uniform diameter, with the result that the resonant modes are only attenuated to a small extent by this technique.
  • acoustic filter or filters within the transmission line.
  • the inclusion of such acoustic filters makes it possible significantly to reduce the quantity of mid- frequency and high-frequency sounds radiated from the end of the transmission line.
  • These acoustic filters take the form either of an expanded or a restricted zone of the pipe, or a series of expanded or restricted zones.
  • the expansion zone, i.e. acoustic compliance, or restriction zone, i.e. acoustic inertance, in the pipe behaves like a reactive low pass filter, similar to a parallel capacitor (or series inductor) found in electrical engineering.
  • acoustic filter The efficacy of such an acoustic filter is dependent on the relative sizes of the loudspeaker diaphragm, expansion or restriction zone or zones, and cross-sectional area of the pipe. It is important to draw a distinction between this type of device and some transmission lines which are known which use a tapered pipe behind the driver.
  • the acoustic low pass filter works because a compliance (for an expansion zone) or inertance (for a restriction zone) is introduced into the pipe.
  • the theory for these devices is very different from that of a tapered pipe which behaves rather like an acoustic horn, but in reverse.
  • Fig. 1 of the accompanying drawings shows a known transmission line loudspeaker system which comprises the combination of a loudspeaker, a cavity and a pipe arranged "in series".
  • the cavity is formed at the end of the pipe and the loudspeaker is situated immediately opposite the entry to the pipe on the wall of the cavity most remote from the pipe.
  • the cavity performs the role of an expansion-type low pass filter by being situated between the loudspeaker and a pipe which has approximately the same cross-sectional area as the loudspeaker, although pipes having areas substantially different from that of the loudspeaker could be used.
  • the transmission line loudspeaker system of the present invention although it uses a low-pass filter, differs from the system shown in Fig. 1.
  • a cavity For a cavity to have a significant effect on the frequency response it will necessarily be relatively large. Therefore, the acoustic pressure distribution within the cavity will not be uniform across all frequencies.
  • the relative positions of the driver, the cavity and the pipe, and the shape of the cavity, will all have an effect on the response of the system.
  • a transmission line loudspeaker comprising at least one driver, an acoustic filter and a transmission line, in which the driver, or one of the drivers if more than one, is positioned at or adjacent to the entry to the transmission line such that the driver effects a parallel driving of both the filter and the transmission line simultaneously.
  • the acoustic filter comprises a cavity.
  • the positioning of the driver, or one of the drivers if more than one, close to the entry to the transmission line means that the pressures at the driver and at the entry to the pipe are approximately equal over a wide range of frequencies.
  • the pressures at the driver and at the entry to the transmission line are approximately equal for a wide range of frequencies, even when modes inside the cavity mean that there is a non-uniform pressure distribution. In this way the configuration behaves more like an idealised acoustic low pass filter.
  • the driver at or adjacent to the entry to the transmission line is positioned on a side wall of the acoustic filter which is a continuation of a wall of the transmission line.
  • the distance between the entry to the transmission line and the driver at or adjacent to said entry is less than approximately one quarter of the wavelength at the highest frequency at which the transmission line makes a contribution to the output.
  • the frequency is preferably of the order of 500 Hz.
  • the at least one driver, the filter and the transmission line are housed within a cabinet, in which a first portion of the cabinet constitutes a cavity acting as a low pass filter and a second portion of the cabinet constitutes the transmission line defined as a sinuous track from the front to the rear of the cabinet.
  • the driver or drivers are mounted at the upper front of the cabinet and the open end of the transmission line is at the lower rear of the cabinet.
  • Fig. 2 illustrates the concept behind the present invention.
  • the transmission line of the system is constituted by a pipe 10 of constant cross-section.
  • a cavity 12 defined by appropriately shaped walls. This cavity acts as an acoustic filter.
  • the cavity 12 is offset relative to the central longitudinal axis of the transmission line, with one wall 14 of the cavity being an extension of one wall of the pipe 10.
  • Adriver 16 is mounted in the wall 14 adjacent to the entry from the cavity 12 into the pipe 10.
  • the driver 16 could alternatively be positioned just within the pipe, or actually at the junction between cavity and pipe.
  • Fig. 3 shows the system of Fig. 2 in an alternative way.
  • Fig. 3 makes it clearer that, in contrast to the "series" arrangement of acoustic filter and pipe in Fig. 1, the present invention uses a parallel arrangement where the driver 16 drives both the acoustic filter 12 and the transmission line 10 at the same time. It does this by being positioned at or close to the entry to the transmission line.
  • this frequency is a determining factor in deciding the maximum distance that one can place the driver away from the filter/pipe junction and still achieve an advantage from the parallel driving.
  • the distance from the centre of the driver to the junction should not be more than a quarter wavelength ( ⁇ /4) at the maximum frequency appropriate for the transmission line concerned.
  • ⁇ /4 quarter wavelength
  • the transmission line loudspeaker system shown in Fig. 2 can be modified by incorporating additional acoustic filters at strategic points along the pipe 10, for example in the form of expansion zones or restriction zones.
  • Fig. 4 shows schematically the addition of an acoustic filter 17 in series with the transmission line 10.
  • the combination of fitter 17 and pipe 10 could be repeated, in series with the first filter and pipe 17, 10.
  • absorbent filling material can be incorporated within the pipe 10 and/or within the cavity 12 to have a dissipative effect.
  • the loudspeaker shown in Figs. 5 to 7 comprises a multi-component housing, indicated generally at 20.
  • the cabinet includes a front wall 23 and a rearwall 24.
  • Adriver21 is mounted in the front wall of the housing, at the upper part of the housing.
  • the driver 21 is here within the cavity (acoustic filter) i.e. spaced from the entry to the transmission line, but is sufficiently close to perform the parallel driving function.
  • a treble unit with a sealed rear enclosure is indicated at 22. Spaced between the front wall 23 and the rear wall 24 of the housing are a pair of partition walls 25 and 26 which are parallel to the front and rear walls of the housing and which divide the interior of the housing into three approximately equal size parts.
  • dividing wall 27 Between the partition walls 25 and 26 and approximately halfway up the partition walls is provided an obliquely extending dividing wall 27.
  • the inclination of the dividing wall 27 helps to avoid an abrupt change in the acoustic properties.
  • a similar dividing wall 28 is provided between the partition wall 26 and the rear wall 24 of the housing, although with the dividing wall 28 extending horizontally.
  • Both the internal partition walls and the cabinet outer walls are preferably made of a suitable rigid material such as medium density fibreboard or aluminium honeycomb sandwich to give the structure rigidity.
  • the partition walls 25 and 26 are provided with large- size holes 30a, 30b, 30c, 30d and 30e.
  • the volume above the dividing walls 27 and 28 constitutes a cavity 12a, equivalent to the cavity 12 of Fig. 2.
  • the cavity is immediately behind the driver 21.
  • the partition wall 25 is provided with an aperture 31 adjacent to the bottom of the partition wall.
  • the other partition wall 26 is provided with an aperture 32 immediately below the dividing walls 27 and 28.
  • the apertures are all substantially rectangular.
  • the apertures thus define horizontal struts which provide bracing and a rigid structure.
  • the cross-sectional area of the apertures 31 and 32 is equal to the cross-sectional area of the transmission line pipe 19.
  • the rear wall 24 of the housing is provided with a vent 33, here shown as a double vent, towards the bottom of the rear wall.
  • the vent 33 shown here has the same area as the pipe 19, although vents of larger or small- erarea could be used.
  • the volume of the cavity 12a is approximately 18 litres and the length of the pipe 19 from entry to vent is approximately 1.7 metres (5.5 feet).
  • Sound-absorbent filling material which has a dissipative effect is incorporated within the cabinet to enhance the frequency response.
  • the transmission line section of the system is lined with a fibrous or cellular foam material 34, for example with a thickness of 15 mm.
  • the lining 35 is preferably of double thickness.
  • the material of the walls within the cabinet also has a dissipative effect to a greater or lesser extent.
  • lining the pipe 19 it can be filled with a foam or fibreglass material.
  • the cavity 12a at the top of the cabinet is also substantially filled with the same or similar material 36.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
  • Details Of Audible-Bandwidth Transducers (AREA)
EP19930302752 1992-04-10 1993-04-07 Loudspeakers Withdrawn EP0565369A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9207882 1992-04-10
GB929207882A GB9207882D0 (en) 1992-04-10 1992-04-10 Loudspeakers

Publications (2)

Publication Number Publication Date
EP0565369A2 true EP0565369A2 (de) 1993-10-13
EP0565369A3 EP0565369A3 (en) 1994-05-11

Family

ID=10713796

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19930302752 Withdrawn EP0565369A3 (en) 1992-04-10 1993-04-07 Loudspeakers

Country Status (5)

Country Link
EP (1) EP0565369A3 (de)
JP (1) JPH0654392A (de)
CN (1) CN1081057A (de)
CA (1) CA2093705A1 (de)
GB (1) GB9207882D0 (de)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0641142A1 (de) * 1993-08-27 1995-03-01 British Broadcasting Corporation Lautsprechergehäuse mit Lüftungsöffnung
WO1995028064A1 (en) * 1994-04-12 1995-10-19 Indrek Hilpus A loudspeaker
GB2376833A (en) * 2001-04-23 2002-12-24 Nec Corp Speaker system for handheld device
US6896096B2 (en) 2000-07-21 2005-05-24 B&W Loudspeakers Limited Acoustic structures
FR2889021A1 (fr) * 2005-07-22 2007-01-26 Menuiserie Georges Girault Enceinte acoustique a haut rendement
WO2014108373A1 (en) * 2013-01-09 2014-07-17 Pss Belgium N.V. Audio output devices
EP2737721A4 (de) * 2011-07-25 2015-06-03 G Licensing Llc Dr Lautsprecher mit ultraflachem profil
US12542988B2 (en) 2021-04-06 2026-02-03 Samsung Electronics Co., Ltd. Electronic device comprising speaker module

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7207413B2 (en) * 2003-06-02 2007-04-24 Tbi Audio Systems Llc Closed loop embedded audio transmission line technology for loudspeaker enclosures and systems
CN103220608B (zh) 2013-04-16 2016-08-24 歌尔声学股份有限公司 扬声器模组

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3687220A (en) * 1970-07-06 1972-08-29 Admiral Corp Multiple speaker enclosure with single tuning
US4224469A (en) * 1979-01-02 1980-09-23 Karson Theodore R Stereo speaker system
US4301889A (en) * 1979-07-27 1981-11-24 Tralonga David V Speaker enclosure
JP2653377B2 (ja) * 1987-06-16 1997-09-17 松下電器産業株式会社 スピーカシステム
US4942939A (en) * 1989-05-18 1990-07-24 Harrison Stanley N Speaker system with folded audio transmission passage

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0641142A1 (de) * 1993-08-27 1995-03-01 British Broadcasting Corporation Lautsprechergehäuse mit Lüftungsöffnung
WO1995028064A1 (en) * 1994-04-12 1995-10-19 Indrek Hilpus A loudspeaker
US6896096B2 (en) 2000-07-21 2005-05-24 B&W Loudspeakers Limited Acoustic structures
GB2376833A (en) * 2001-04-23 2002-12-24 Nec Corp Speaker system for handheld device
GB2376833B (en) * 2001-04-23 2004-12-15 Nec Corp Speaker system
US6834744B2 (en) 2001-04-23 2004-12-28 Nec Corporation Speaker system
FR2889021A1 (fr) * 2005-07-22 2007-01-26 Menuiserie Georges Girault Enceinte acoustique a haut rendement
EP2737721A4 (de) * 2011-07-25 2015-06-03 G Licensing Llc Dr Lautsprecher mit ultraflachem profil
WO2014108373A1 (en) * 2013-01-09 2014-07-17 Pss Belgium N.V. Audio output devices
US12542988B2 (en) 2021-04-06 2026-02-03 Samsung Electronics Co., Ltd. Electronic device comprising speaker module

Also Published As

Publication number Publication date
CN1081057A (zh) 1994-01-19
JPH0654392A (ja) 1994-02-25
EP0565369A3 (en) 1994-05-11
GB9207882D0 (en) 1992-05-27
CA2093705A1 (en) 1993-10-11

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