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WO2010049399A1 - Haut-parleur basse fréquence directionnel - Google Patents

Haut-parleur basse fréquence directionnel Download PDF

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Publication number
WO2010049399A1
WO2010049399A1 PCT/EP2009/064100 EP2009064100W WO2010049399A1 WO 2010049399 A1 WO2010049399 A1 WO 2010049399A1 EP 2009064100 W EP2009064100 W EP 2009064100W WO 2010049399 A1 WO2010049399 A1 WO 2010049399A1
Authority
WO
WIPO (PCT)
Prior art keywords
sound reproduction
reproduction means
loudspeaker
enclosure
sound
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.)
Ceased
Application number
PCT/EP2009/064100
Other languages
English (en)
Inventor
Jaakko Suomalainen
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.)
NEVERLAND MUSIC Ltd Oy
Original Assignee
NEVERLAND MUSIC Ltd Oy
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 NEVERLAND MUSIC Ltd Oy filed Critical NEVERLAND MUSIC Ltd Oy
Publication of WO2010049399A1 publication Critical patent/WO2010049399A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

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
    • 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
    • H04R1/40—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers
    • H04R1/403—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only by combining a number of identical transducers loud-speakers
    • 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 
    • H04R1/26—Spatial arrangements of separate transducers responsive to two or more frequency ranges
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • 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
    • H04R1/2869—Reduction of undesired resonances, i.e. standing waves within enclosure, or of undesired vibrations, i.e. of the enclosure itself
    • H04R1/2876—Reduction of undesired resonances, i.e. standing waves within enclosure, or of undesired vibrations, i.e. of the enclosure itself by means of damping material, e.g. as cladding
    • H04R1/288—Reduction of undesired resonances, i.e. standing waves within enclosure, or of undesired vibrations, i.e. of the enclosure itself by means of damping material, e.g. as cladding 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
    • H04R1/323—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired directional characteristic only for loudspeakers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
    • H04R2201/02—Details casings, cabinets or mounting therein for transducers covered by H04R1/02 but not provided for in any of its subgroups
    • H04R2201/028—Structural combinations of loudspeakers with built-in power amplifiers, e.g. in the same acoustic enclosure
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/12—Circuits for transducers, loudspeakers or microphones for distributing signals to two or more loudspeakers

Definitions

  • This invention relates to the field of sound reproduction. More specifically the present invention relates to directive low frequency loudspeakers and enclosures therein.
  • a room space can not efficiently absorb low frequencies of a spherical acoustic radiator. Reflections cause distortion in frequency response depending on the placement of the loudspeakers, the observation point and the characteristics of the room. The situation is especially difficult in the studio environment, where the listening precision is a main criterion.
  • One solution for this problem could be the use of directive loudspeakers.
  • the used studio loudspeakers are spherical radiators at low frequencies, propagating sound isotropically as a spherical wave.
  • several methods are used to direct sounds in middle and high frequencies, but basically all studio loudspeakers are still spherical radiators at low frequencies.
  • Possible reasons for a lack of a directive bass loudspeaker may be a shortage of technical solutions to accomplish directivity in low frequencies, and the inherent incapability of humans to distinguish the direction of incidence of the sound at low frequencies.
  • the problems can be eliminated with sound checking i.e. by careful tuning and adjusting the amplifiers and loudspeakers.
  • the placement of the loudspeakers is crucial in this process.
  • tuning and adjusting the sound will be perfect only in one small location ("sweet spot") and elsewhere the sound is still distorted because the frequency response varies in every location in the room.
  • the process will have to be started all over again, because different places of walls and planes in different places causes different distortion.
  • WO2004002190A1 discloses a low frequency loudspeaker, which comprises at least a pair of loudspeakers mounted in the same box, facing in opposite directions and powered as separate elements by signals coming from a signal source but having different amplitude and phase (see Fig. 1).
  • the main enclosure encompasses the rear enclosure, wherein the rear element is placed.
  • the represented invention is based on the band-pass or compound solution, where the directivity of the sound is obtained by a combination of the volume of the enclosure and the ports Pl, P2 in it, to which the loudspeaker element feeds energy. Since the sound of the band-pass loudspeaker is produced by the air column the sound of the loudspeaker does necessarily not have particularly good frequency response, i.e. the sound may be more "slack", and the air column may continue to resonate though the energy feeding has been finished. Removing the rear enclosure disables the loudspeaker and of course its directivity.
  • Fig. 2 The other known method is presented in Fig. 2.
  • three similar loudspeakers 202, 204 and 206 One of them (204 in Fig. 2) is turned to face the opposite direction than the other two and it has an inverted phase.
  • Some manufacturers have taken into consideration this sort of solution and have added the required phase shift feature into the devices.
  • This solution can diminish the backward directing sound pressure level about 10-12 dB, but unfortunately, three separate loudspeakers would need a good deal of space.
  • the objective of the present invention is to at least alleviate the aforesaid defects of prior art solutions when it comes to the directivity of loudspeakers at low frequencies.
  • the object of the present invention is to provide a directive loudspeaker for low frequencies, which may preferably attenuate the backwards sound pressure level e.g. over 20 dB and produce more vigorous and/or fast frequency response to the forward direction.
  • a loudspeaker for outputting at least low frequency sound waves in a predetermined forward direction, said loudspeaker comprising: -two sound reproduction means, such as two electro-acoustic transducers,
  • a method for manufacturing a low frequency loudspeaker for outputting low frequency sound waves in a predetermined forward direction comprising:
  • the sound reproduction means may refer to one or more electro-acoustic transducers, sometimes also known as drivers, especially when intended for low frequencies, they may be e.g. sub-woofers and/or woofers implemented in any known way.
  • the enclosure may refer to any known type of loudspeaker enclosure.
  • the processing means may refer to one or more electronic elements such as (micro)processors, microcontrollers, digital signal processors (DSPs), programmable logic chips, or any desired combination thereof.
  • Signal processing is performed preferably in digital form since the techniques of digital signal processing are much more powerful and efficient than analog domain signal processing.
  • the provided directive loudspeaker with its enclosure is simple to use and manufacture, affordable, small in size, light, and versatile.
  • the device is feasible in studio use, but also in home use, such as with stereo devices, home theaters, and with use of speech and audio equipments.
  • a further utility of certain one or more embodiments is that the reflections from the rear and side walls may diminish and almost disappear, which may diminish the standing waves caused by the aforementioned reflections. Further, the reflections from the side walls may be more uniform throughout the used frequency range, which enables the usage of the directive loudspeaker in various environments.
  • Yet another utility of certain one or more embodiments is to improve the impulse and frequency responses of the space.
  • the improved frequency response may thus be more uniform throughout the used frequency range. Without directivity, the frequency response increases when approaching the low frequencies.
  • the processing means may optionally comprise first and second sensing means for obtaining indications of the frequency response in forward and backward directions and/or third and/or fourth sensing means for obtaining indications of the impedance of the front and/or back elements.
  • the used expression "low frequency” refers herein to the frequency range from about 20 Hz to 250 Hz.
  • Fig. 1 illustrates one prior art solution for directing the low frequency sound waves
  • Fig. 2 shows a top view of another prior art solution provided by some manufacturers
  • Fig. 3 a illustrates a cross section of an embodiment of the present invention
  • Fig. 3b is a bock diagram an embodiment of the processing means according to the present invention.
  • Fig. 4a illustrates an output impedance curve of front and rear elements before corrective actions
  • Fig. 4b illustrates an output impedance curve of front and rear elements after corrective actions
  • Fig. 5 illustrates a dissect view of a dynamic driver
  • Fig. 6 illustrates a cross section of another embodiment of the present invention
  • Fig. 7 illustrates a top view of the invention and the observation points of the sound waves
  • Figs. 8a-8c illustrate the sound wave patterns of the front and the rear elements and the sum of those
  • Fig. 9a is a modeling of a 50 Hz sound distribution in a space of a spherical radiator loudspeaker
  • Fig. 9b is a modeling of a 50 Hz sound distribution in a space of a directive loudspeaker
  • the directive low frequency loudspeaker comprises two sound reproduction means for low frequencies, processing means 308 for signal processing and an enclosure 306.
  • the sound reproduction means i.e. front element 302 and rear element 304, are faced to opposite directions and mounted in the opposite sides of the same enclosure 306.
  • the elements in the enclosure share the united space inside the enclosure 306.
  • the front and the rear elements can be similar or different kind of sound reproduction means without any limitation.
  • the enclosure 306 is a uniform box filled with a damping material 318 and the composition of the damping material remains the same through the enclosure.
  • Other type of drivers (not shown) than the low frequency drivers may have been placed in the same enclosure as well as the processing means.
  • the processing means is preferably disposed into the enclosure, but it can be placed outside of the enclosure as well.
  • the loudspeaker may be a two-way or three-way loudspeaker.
  • processing means 308 the incoming signal 310 is typically divided 322 into two or three frequency ranges.
  • three drivers are used to cover different frequency ranges; sub, mid and high. Mid and high signals are led to their own amplifiers and drivers.
  • Low frequency alias sub signal is duplicated; one signal for the front element 312 and one for the rear element 314.
  • the signal for the rear element 314 is delayed 324 by a phase inversion and a time factor depending on the distance between the front and rear element 316.
  • the amplifier gain level of the rear element signal 314 is set e.g.
  • the stages in the processing means may also be performed in some other order than presented in the Fig. 3b.
  • phase delay it is preferably to apply a phase delay to the signal of the rear element, but it is alternatively possible to provide the required phase difference between the front and rear elements by applying a phase shift to the signal of the front element or to apply suitable phase shifts to the signals of the both front and rear elements.
  • the distance between the elements 316 is essential in the present invention.
  • the delay of the rear element signal 314 is based to the distance 316, so the delay time t d is
  • s is the distance 316 between the elements and v is the speed of sound in air ⁇ 343 m/s.
  • the adjustment of the distance is a compromise; the shorter distance increases the loss of power, but the directivity reaches higher frequencies. The longer distance decreases the loss of power at low frequencies, but also the upper limit of the directivity decreases.
  • the distance is preferably at least e.g. 20-30 cm or more, because with a shorter distance the loss of power increases too much.
  • the loss of power in a short distance is caused by two factors: the phase shift and the sound pressure of the front element.
  • the phase shift is the more imposing factor, because in the short distance it is nearer to 180° due to the long wave length of the very low frequency sound wave and, thus, the loss of power increases.
  • the shorter distance between elements generates a greater sound pressure, which for its part increases the loss of power, because the elements physically interfere in each other stronger.
  • the distance of the elements has also the upper limit. If the distance between the elements is too high, the upper limit frequency of the directivity will sink too low, because the higher frequency sound waves begin to interfere destructively due to the phase shift, which will approach 180° again. Thus, the upper limit of the elements should be at the most e.g. 200 cm.
  • the appropriate distance between the elements also depends on the purpose of use. For example, if the loudspeaker is produced for speech reproduction means, the lowest frequencies are not necessarily needed and, since the attenuation of the lowest frequencies is not harmful the distance between the elements might be smaller. On the other hand, if the size is not an issue and only the lower frequencies are needed, the distance might also be longer, but not longer than 200 cm.
  • the lower amplifier gain level of the rear element signal is explained with a dampening effect caused by the enclosure to the sound pressure in the rear side of the enclosure.
  • adjusting the amplifier gain level influences strongly to the impedance of the element, because the elements share the same space and therefore are acting as an integral system.
  • the increase of the power in one element can be seen in the impedance of the other element.
  • the lower amplifier gain level of the rear element causes an unbalance between the impedances of the elements, as can be seen in Fig. 4a.
  • the impedance curve of the rear element 404 is on a higher level through the whole frequency range than the impedance curve of the front element 402.
  • the impedance difference causes also the difference between the signal responses of the elements.
  • the directivity varies according to the frequency.
  • Fig. 4b is shown the impedance curve of the elements after the corrective actions.
  • the differences between the impedances can be leveled out by increasing the mass of the diaphragm and/or the dust cap of the rear element.
  • the diaphragm 502 and the dust cap 504 are shown in a cut-away view of a driver in Fig. 5.
  • the amount of an extra mass is adjusted in compliance with the driver. Effective factors of the extra mass are the difference between the amplifier gain level for the elements, the delay i.e. the distance of the elements, the size of the enclosure and the used damping material in the enclosure.
  • the increase of the extra mass can be implemented by adding glue to the dust cap 504, for example latex-based adhesive, or by gluing a disc made of, for example, wood composite or wood-plastic composite or some other appropriate material.
  • the elements with different impedances can preferably be chosen and mounted in the first place so as to eliminate the impedance difference caused by the aforementioned difference between the amplifier gain levels for the elements.
  • the amplifier gain level lowering and the distance between the elements is set to suit to the selected elements.
  • the damping material used in the enclosure 306 also has some influence to the impedances.
  • the purpose of the heavily damped enclosure is to prevent the elements to interfere with each other. Especially, without damping material in the integral system the front element interferes with the rear element more efficiently.
  • the enclosure includes also an aperiodic reflex tube 320 filled with damping material (See Fig. 6). The tube is adjusted at the resonance frequency of the system. Using of the aperiodic reflex tube in the enclosure further improves the adjustment of the impedances by decreasing the impedance peak at low frequencies. This way the amplifier has a better control on the elements.
  • the processing means may perform the system checking for optimizing the directivity e.g. after being powered on.
  • the user may be informed about, for example, the needed extra weight.
  • the information of the user may be performed by the processing means and/or the processing means may be configured to adjust the amplifier gain level of front and/or rear element(s).
  • the processing means may be configured to obtain the information from the sensing means and it may be configured to adjust e.g. the amplifier level and/or the delay of certain frequencies.
  • the processing means may be configured to inform the user about the need of a service of a component or components since the fatigue of the elements can be seen in the impedance measuring.
  • the loudspeaker achieves even 80-92% absorption of the backward directed sound pressure as demonstrated in more detail below.
  • Figure 7 illustrates a top view of the invention and the observation points for the sound waves.
  • the directivity can be explained with the phase shift.
  • the phase shift of the elements In the backward of the loudspeaker (observation point A) the phase shift of the elements is 180° constantly.
  • the phase shift grows over 180°, because of the distance dependent delay added to the rear element signal 314 and the distance itself.
  • the middle axis of the elements While approaching the middle axis of the elements the bigger the phase shift is growing and it is approaching 360°.
  • the sound pressure level is growing because of the sound waves are interfering constructively.
  • the sound pressures caused by individual elements and their sum wave are illustrated in the observation point A (see Fig. 8a), which is 180° from the front element.
  • A is the amplitude
  • ⁇ is the angular frequency
  • t is the time
  • ⁇ is the phase of the wave.
  • a sine wave is chosen to represent a sound wave since it is the simplest kind of sound wave.
  • the amplitude of a wave signifies the sound pressure in Pascals (Pa) and frequency /is the pitch of the sound in Hertz (Hz).
  • the function of the superposition of the waves is a product of two cosine functions
  • ⁇ r and ⁇ / are the phases of the rear and front elements, respectively.
  • t d is the time that the wave propagates and/or is delayed before the observation point
  • ⁇ 0 is the initial phase of the wave.
  • the observation is also made in the 90° direction beside of the loudspeaker, i.e. in the observation point C (see Fig. 7).
  • the equation 4 the equation of the superposition of the rear and front waves in the observation point B is
  • the amplitude of the sum wave is
  • Figures 9a and 9b illustrates the modeling of a 50 Hz sound distribution in a space.
  • the inner circle in the figures illustrates the 100 dB line and the outer about 95 dB.
  • Fig. 9a can be seen that the sound of a spherical radiator is almost equally distributed both forward and backward from the loudspeaker.
  • the difference between the Figures 9a and 9b is obvious; the sound is almost totally directed to forward.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
  • Fittings On The Vehicle Exterior For Carrying Loads, And Devices For Holding Or Mounting Articles (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)

Abstract

L'invention concerne un haut-parleur permettant d'émettre au moins des ondes sonores basse fréquence dans une direction avant prédéterminée, lequel haut-parleur comprend : deux moyens de reproduction de sons, comme deux transducteurs électro-acoustiques, un moyen de traitement pour le traitement de signaux, et une enceinte pour monter les moyens de reproduction de sons, les deux moyens de reproduction de sons étant agencés de manière à être orientés dans des directions opposées et étant montés de manière à se situer sur les côtés opposés de la même enceinte afin de former au moins partiellement un moyen de reproduction sonore avant et arrière lors de l'utilisation, respectivement. Il existe un volume acoustique efficace commun dans l'enceinte pour les deux moyens de reproduction sonore, et le signal d'entrée du moyen de reproduction sonore arrière et/ou le signal d'entrée du moyen de reproduction sonore avant sont conçus pour être convertis par le moyen de traitement de sorte que la sortie du moyen de reproduction sonore arrière possède une différence de phase par rapport à la sortie du moyen de reproduction sonore avant, telle que la sortie du moyen de reproduction sonore arrière assure une atténuation du niveau sonore de sortie du moyen de reproduction sonore avant lorsque ledit niveau sonore est mesuré à l'arrière du haut-parleur.
PCT/EP2009/064100 2008-10-30 2009-10-27 Haut-parleur basse fréquence directionnel Ceased WO2010049399A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20086026 2008-10-30
FI20086026A FI20086026L (fi) 2008-10-30 2008-10-30 Suuntaava matalataajuuskaiutin ja menetelmä sen valmistamiseksi

Publications (1)

Publication Number Publication Date
WO2010049399A1 true WO2010049399A1 (fr) 2010-05-06

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PCT/EP2009/064100 Ceased WO2010049399A1 (fr) 2008-10-30 2009-10-27 Haut-parleur basse fréquence directionnel

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WO (1) WO2010049399A1 (fr)

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001022787A1 (fr) * 1999-09-23 2001-03-29 Budge Tierry R Haut-parleur a chambre acoustique a amortissement progressif
WO2004002190A1 (fr) * 2002-06-24 2003-12-31 Outline Di Noselli G. & C. S.N.C. Enceinte de haut-parleur grave a directivite configurable
JP2004140712A (ja) * 2002-10-21 2004-05-13 Sanyo Electric Co Ltd スピーカ装置
WO2007021861A2 (fr) * 2005-08-16 2007-02-22 Honeywell International, Inc. Systeme de haut-parleur directionnel
EP1887687A1 (fr) * 2006-08-01 2008-02-13 Vestel Elektronik Sanayi ve Ticaret A.S. Dispositif et procédé de compensation pour des systèmes acoustiques
DE102006058009B3 (de) * 2006-12-08 2008-02-14 D & B Audiotechnik Ag Lautsprechersystem mit reduzierter rückseitiger Schallabstrahlung
US20080159583A1 (en) * 2006-12-28 2008-07-03 Matsushita Electric Industrial Co., Ltd. Speaker

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001022787A1 (fr) * 1999-09-23 2001-03-29 Budge Tierry R Haut-parleur a chambre acoustique a amortissement progressif
WO2004002190A1 (fr) * 2002-06-24 2003-12-31 Outline Di Noselli G. & C. S.N.C. Enceinte de haut-parleur grave a directivite configurable
JP2004140712A (ja) * 2002-10-21 2004-05-13 Sanyo Electric Co Ltd スピーカ装置
WO2007021861A2 (fr) * 2005-08-16 2007-02-22 Honeywell International, Inc. Systeme de haut-parleur directionnel
EP1887687A1 (fr) * 2006-08-01 2008-02-13 Vestel Elektronik Sanayi ve Ticaret A.S. Dispositif et procédé de compensation pour des systèmes acoustiques
DE102006058009B3 (de) * 2006-12-08 2008-02-14 D & B Audiotechnik Ag Lautsprechersystem mit reduzierter rückseitiger Schallabstrahlung
US20080159583A1 (en) * 2006-12-28 2008-07-03 Matsushita Electric Industrial Co., Ltd. Speaker

Also Published As

Publication number Publication date
FI20086026A7 (fi) 2010-05-01
FI20086026L (fi) 2010-05-01
FI20086026A0 (fi) 2008-10-30

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