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
  • H04R1/32—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
• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
  • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/18—Methods or devices for transmitting, conducting or directing sound
  • G10K11/26—Sound-focusing or directing, e.g. scanning
  • G10K11/34—Sound-focusing or directing, e.g. scanning using electrical steering of transducer arrays, e.g. beam steering
  • G10K11/341—Circuits therefor
  • G10K11/346—Circuits therefor using phase variation
• • 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
  • H04R1/2815—Enclosures comprising vibrating or resonating arrangements of the bass reflex type
  • H04R1/2823—Vents, i.e. ports, e.g. shape thereof or tuning thereof with damping material
  • H04R1/2826—Vents, i.e. ports, e.g. shape thereof or tuning thereof with damping material 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
  • H04R2430/00—Signal processing covered by H04R, not provided for in its groups
  • H04R2430/20—Processing of the output signals of the acoustic transducers of an array for obtaining a desired directivity characteristic
• • 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

• the present invention relates to a loudspeaker sound reproduction system, commonly referred to as "bass-reflex" type speaker.
• a conventional technique for increasing the directionality is to interfere two opposite omnidirectional sources in phase and spaced by a distance d by introducing a delay ⁇ on one of the sources corresponding to the time taken by the sound to travel the distance d between the sources .
• the acoustic signals emitted by the two sources interfere constructively in the axis of the two sources ahead of the non-delayed source (0 °) but cancel in the axis of the two sources. behind the delayed source (180 °).
• the radiated pressure decreases as the angle formed with the forward direction increases and the polar radiation pattern is therefore cardioid.
• a delay ⁇ less than the time taken by the sound to travel the distance d between the sources causes a hypercardioid-type directivity; in the extreme, a zero delay causes a directivity of bi-directional type.
• a delay ⁇ greater than the time taken by the sound to travel the distance d between the sources leads to an infracardioid-type directivity (a very large delay ⁇ leading even to an omnidirectional directivity).
• Directivity control is, however, only achieved over a limited frequency range. Below a frequency ft determined by the spacing between the sources and the delay applied, the addition of a second source causes a decrease in the radiated pressure in the axis although the directivity function is retained. Beyond a certain frequency f 2 , the addition of a second source causes a decrease in the radiated pressure in the axis and a gradual deformation of the directivity function. In the case of a cardioid directivity function, the difference separating the frequencies et and est is 2.3 octaves, which represents the useful operating range of the device (see curve in dashed lines in FIG. 11).
• speakers speakers or speakers type "bass-reflex".
• the peculiarity of this type of speaker is to use one or more vents to increase the effectiveness of the radiation in the lowest frequencies compared to a closed enclosure.
• the "hass-reflex" type enclosure therefore has at least two radiating surfaces: the one or more vents, which radiate around the tuning frequency f c of the speaker (EV curve), and the speaker whose radiation exceeds that of (the) vents beyond a contribution limit frequency f ⁇ _ (HP curve), as shown in Figure 13.
• These two frequencies f c and fi. are determined by the length of the vent (s), the vent area (s) and the volume of air contained in the enclosure.
• the loudspeaker radiates in phase with the vent; below the tuning frequency f c , the loudspeaker radiates out of phase with the vent.
• the invention is directed to a loudspeaker sound reproduction system in which it is possible in particular to obtain increased directionality and an increase in the pressure in the axis with the addition of a second source over a frequency range. more extensive than previously mentioned and by means of a relatively simple implementation.
• the invention thus proposes a sound reproduction system comprising a speaker provided with a first speaker and a second speaker mounted on one face of the speaker, the first speaker and the second speaker being received respectively in a first volume of the enclosure and in a second volume of the enclosure separated by a partition and opening respectively by a first vent and a second vent, the first vent and the second vent being located on either side of the assembly formed by the first speaker and the second loudspeaker, characterized by processing means adapted to respectively apply to the first speaker and the second speaker a first electrical signal and a second electrical signal obtained from the same signal by differentiated phase processing variable with the frequency such that the first electrical signal and the second electrical signal are offset by a variable time (at least substantially) proportional to the acoustic distance separating the first half-enclosure, including the first volume, the first speaker and the first vent, the second half-speaker, including the second volume, the second speaker and the second vent.
• the differentiated treatment may be such that the first electrical signal and the second electrical signal are opposed in phase and offset by a time corresponding to the acoustic distance separating the first half-enclosure, including the first volume, the first loudspeaker and the first vent, of the second half loudspeaker, including the second loudspeaker, the second loudspeaker and the second vent, over at least one frequency range including the tuning frequency of the vents and the frequency limit of contribution of the loudspeakers.
• the differentiated treatment may be such that the first electrical signal and the second electrical signal are opposed in phase and offset by a time corresponding to one third of the acoustic distance separating the first half-enclosure, including the first volume, the first speaker and the first vent, of the second half-speaker, including the second volume, the second speaker and the second vent.
• the differentiated treatment may be such that the first electrical signal and the second electrical signal are opposed in phase and offset by a time corresponding to three times the acoustic distance separating the first half-enclosure, including the first volume, the first speaker and the first vent, the second half-speaker, including the second volume, the second speaker and the second vent.
• the differentiated treatment is such that the first electrical signal and the second electrical signal are in phase and offset by a time corresponding to the acoustic distance separating the first half-enclosure, including the first volume, the first speaker and the first vent, the second half-speaker, including the second volume, the second speaker and the second vent.
• the sound level is then increased in the source axis on the delayed source side.
• the delay generated by the offset is introduced between two signals in phase (in which case the noise level is increased in the source axis on the delayed source side), or between two signals in phase opposition, one having a reversed polarity with respect to the other (in which case the noise level is increased in the source axis, on the opposite side to that of the delayed source).
• the phase opposition between the two signals can be obtained by inverting the electrical terminals of one of the two loudspeakers or by introducing on one of the two signals a delay equal to half a period.
• the differentiated treatment is generally such that the direction of maximum efficiency of the radiation is directed along the axis formed by the first speaker and the second speaker. It is generally provided that the axis formed by the first speaker and the second speaker is directed to an audience area to be covered.
• the processing means are able to selectively apply an identical electrical signal to the first loudspeaker and the second loudspeaker in a first operating mode, and the first electrical signal and the second electric signal obtained by treatment. differentiated in a second mode of operation. It is thus possible to alternate between an essentially omnidirectional mode of operation and a directive mode of operation.
• first speaker and the second speaker are identical and that the first volume and the second volume are symmetrical with respect to the partition.
• the first speaker and the second speaker are spaced apart a first distance
• the first vent and the second vent are distant a second distance
• the ratio of the second distance at the first distance is between 2 and 3.
• the ratio can be between 2.2 and 2.5.
• the enclosure comprises a first pair of connection points electrically connected to the first speaker and a second pair of connection points electrically connected to the second speaker and the processing means are capable of respectively applying the first electrical signal to the first pair of connection points and the second electrical signal to the second pair of connection points.
• the processing means comprise, for example, a filter whose phase transfer function is such that it generates a variable delay with frequency and corresponding substantially to the acoustic distance separating the first half-enclosure, including the first volume, the first speaker and the first vent, the second half-speaker, including the second volume, the second speaker and the second vent.
• the invention further proposes a processing circuit adapted to apply a first electrical signal to a first speaker mounted with a second speaker on a wall of an enclosure having a first volume and a second volume separated by a partition, receiving respectively the first speaker and the second speaker, and each opening respectively a first vent and a second vent located on either side of the assembly formed by the first speaker and the second speaker, characterized by processing means adapted to respectively apply to the first speaker and the second speaker a first electrical signal and a second electrical signal obtained from the same signal by differential phase treatment variable with the frequency such as the first electrical signal and the second electrical signal are shifted by a variable time (at least substantially) proportional to the acoustic distance separating the first half-chamber, including the first volume, the first speaker and the first vent, from the second half -encase, including the second volume, the second speaker and the second vent.
• This processing circuit may also include some of the optional features referred to above with respect to the sound reproduction system.
• FIG. 1 shows a front view of an enclosure of a system according to the teachings of the invention
• FIG. 2a shows a view along section H-II of the enclosure of Figure 1;
• FIGS. 2b and 2c illustrate alternative embodiments for the vents of the enclosure of FIG. 2a;
• FIG. 3 represents the acoustic distance between two "bass-reflex" type systems;
• FIG. 4 diagrammatically represents the main elements for processing the electrical signals applied to the loudspeakers of the enclosure of FIG. 1;
• FIG. 5 represents the enclosure of FIG. 1 turned towards the public in an omnidirectional radiation mode;
• - Figure 6 shows the enclosure rotated 90 °, speakers on the side, in a directional radiation mode;
• FIG. 8 is a polar diagram of the radiation of the enclosure in the omnidirectional radiation mode
• FIG. 9 is a polar diagram of the radiation of the enclosure in the directional radiation mode of FIG. 6;
• FIG. 10 is a polar diagram of the radiation of the enclosure in the directional radiation mode of FIG. 7;
• FIG. 11 shows the gain in the axis provided by the presence of a second source in the case of the system according to the invention and in a conventional case;
• FIGS. 12a to 12c represent different types of assembly that can be envisaged for loudspeakers of the type shown in FIG. 1 in directional radiation mode;
• FIG. 12d represents an assembly that can be envisaged for enclosures of the type represented in FIG. 1 in omnidirectional mode
• FIG. 13 shows the amplitude response curve as a function of the frequency of a "bass-reflex" loudspeaker
• FIG. 14 shows the phase response curve as a function of the frequency for this same type of enclosure.
• FIGS. 1 and 2a An example of a sound reproduction system according to the teachings of the invention which comprises an enclosure represented in FIGS. 1 and 2a and a processing circuit illustrated in FIG. 4 is described below.
• the chamber shown in FIGS. 1 and 2 is a "bass reflex" type enclosure 2 of parallelepipedal general shape and divided into two half-symmetrical enclosures 3, 5 by means of an internal partition 4 essentially parallel to its lateral external walls. 6.
• Such a speaker 2 is particularly suitable for forming a subwoofer (or "subwoofer” according to the English name). It could be alternatively provided to use two separate enclosures and joined to obtain a structure of the same type as described here.
• the enclosure At the level of a wall of a so-called front face, distinct from the side walls 6, the enclosure carries two loudspeakers 10, 11 situated on either side of the internal partition 4 and which therefore extend each in one of the two half-chambers 3, 5.
• the front face 8 is that defined by the longer side and the smaller side of the parallelepiped that usually form the enclosure 2.
• the speakers 10, 11 are mounted on the front face 8 so that their main direction of emission is substantially perpendicular to the front face 8 and directed towards the outside of the enclosure. This direction is conventionally designated by X.
• the loudspeakers 10, 11 are here identical and aligned along an axis Y situated in the plane of the front face 8 and substantially parallel to the largest side of the enclosure 2.
• the loudspeakers 10, 11 are moreover almost juxtaposed in the direction of their alignment Y so that the distance DHP separating the two loudspeakers 10, 11 (that is to say their respective centers where their membrane) is relatively small, here barely greater than the outside diameter of the loudspeakers taken perpendicular to the X direction.
• the enclosure 2 described here also has a small side (direction Z which forms with the Y direction the plane of the front face 8) whose size is barely greater than the diameter of the speakers.
• Each half-chamber 3, 5 comprises a duct 12, 13 located opposite the internal partition 4 in each half-chamber 3, 5 and each opening into a vent 14, 15 formed in the front face 8 of the enclosure 2.
• the vents could also lead to the sides.
• Each vent 14, 15 extends over the entire height (in the Z direction) of the enclosure and located at the periphery of the front face 8 in the Y direction.
• vents 14, 15 are thus aligned with the loudspeakers 10, 11 but situated on either side of the set of two loudspeakers 10, 11.
• the distance separates the vents 14, 15 D E v is by therefore greater than the distance separating the loudspeakers D H p.
• the ratio between these distances D E V / DHP is generally between 2 and 3, and preferably between 2.2 and 2.5 in order to make the most of the effect presented in the following. (and which optimally takes place in theory for a ratio of 2.3).
• Each duct 12, 13 is in fact formed between the external lateral wall 6 concerned and an internal wall 16, 17 and of general direction parallel to the external lateral walls 6.
• Each inner wall 16, 17 also terminates at its end opposite to the front face 8 in an extension 18, 19 substantially parallel to the rear face of the enclosure 2.
• vents 14, 15 may be made differently, for example by means of plastic tubes 12 ", 13" ( Figure 2c) or profiled panels 16 ', 17' ( Figure 2b). (In FIGS. 2b and 2c, the elements similar to those of FIG. 2a have been repeated with the notation prime and second, respectively.)
• Each half-enclosure 3, 5 thus forms a "bass-reflex" type system whose vent 14, 15 radiates around the tuning frequency fc whose value is determined by the surface of the vent, by the length of the vent, and by the volume of the speaker, and whose speaker radiates mainly above a limit frequency of contribution fi. above the tuning frequency fc.
• the two vents 14, 15 and the two loudspeakers 10, 11 respectively have a common agreement f c frequency and f contribution limit frequency
• the acoustic distance D A (f) between the rear half-chamber 3 and the half-front chamber 5 corresponds to the phase difference between the pressures generated by these two half-speakers in this direction, difference expressed as a distance equivalent to this difference for the acoustic wave. This phase difference is variable depending on the frequency considered.
• the acoustic distance thus accumulates the physical distance between the half-chambers and the effects related to the phase relations between the sources, and thus depends on:
• the acoustic distance between the half-rear speaker and the half-front speaker is equal to the distance between the vents.
• D E v increased by a distance induced by the phase opposition between vents and loudspeakers.
• the acoustic distance is equal to the physical distance separating the between the tuning frequency fc and the contribution limiting frequency ft of the loudspeaker.
• the acoustic distance decreases from the physical distance between the DEV vents and the physical distance separating the DHP loudspeakers.
• the acoustic distance tends to an asymptote equal to the physical distance DHP separating the loudspeakers.
• the enclosure 2 finally comprises two connectors (which constitute pairs of connection points) 20, 21, each connector being electrically connected to a single loudspeaker 10, 11.
• the sound reproduction system also comprises a circuit T treatment whose main elements are shown in Figure 4.
• the processing circuit T receives an electrical signal defining the acoustic signal to be emitted from a source S on a connector 22.
• the processing circuit T directly connects the connector
• the processing circuit T connects, via an electrical circuit hereafter, also the connector 22 at the input to a second output connector intended to be connected to the connector 21 of the second loudspeaker 11.
• the aforementioned electrical circuit comprises a controlled switch K which receives as input the electrical signal coming from the source S via the input connector 22, and which is able selectively, as a function of information M designating the mode of operation, to apply this signal at a first output of the switch K connected directly to the second output connector or to a second output of the switch K connected to the second output connector via a filter F whose characteristics will be described below.
• the switch K is controlled by means of the information M (for example by a command manual, or alternatively logic control) so as to electrically connect the input connector 22 of the processing circuit T to the second output connector of the processing circuit T.
• the two loudspeakers 10, 11 receive an identical signal (namely here the signal emitted by the source).
• the two loudspeakers and the two vents therefore emit each of the same acoustic waves reproducing the signals generated by the source S, in particular above the contribution limit frequency f 1. speakers, respectively around the tuning frequency fc of the enclosure, generally towards the front of the enclosure (X direction defined above), but without particular directivity control, as shown schematically in FIG. 8.
• the enclosure is therefore generally arranged with respect to the audience as represented in FIG.
• the switch K connects the input connector 22 to the second output connector 21 via the filter F.
• ⁇ (f) D A / C
• C is the propagation velocity sound.
• the frequency range in which the directivity along the Y axis is obtained with an increased efficiency in the axis is therefore much greater than that obtained by conventional techniques.
• a distance ratio D E V / DHP between the distance D EV separating the vents 14, 15 and the distance D H p separating the loudspeakers 10, 11 having a maximum value of the order of 2, 3 (the ratio is precisely 2.3 in the embodiment described here) so that there is no interruption between the good directivity range around the tuning frequency fc and the range of good directivity above the contribution limit frequency fi.
• a positive gain is obtained by the addition of a second source over a particularly wide frequency range as clearly visible in FIG. 11, where the solid line curve represents the gain induced by the addition. of the second source as a function of frequency in the case of the system which has just been described (the dotted line representing the gain induced by the addition of a second source in the conventional case described in the introduction).
• vents on either side of the loudspeakers are particularly interesting since the intervent distance makes it possible to gain by adding the second source over a low frequency range, while the inter-loudness distance speakers makes it possible to gain and control directivity without distortion by adding a second source over a relatively higher frequency range, in correspondence with the conventional frequency positioning of these elements.
• the invention is of course not limited to the embodiment which has just been described.
• FIG. 12a shows two speakers back to back (that is to say each arranged as in Figure 6, the speakers of each speaker facing away from the other speaker), in Figure 12b two speakers facing each other (c ' that is to say each arranged as in Figure 6, the speakers of each speaker directed to the other speaker, with here a spacing of a half speaker depth between the speakers), and in Figure 12c two side speakers against side (that is to say each arranged as in Figure 7, and in contact at a side wall).
• Figure 12d shows the assembly of two speakers in omnidirectional mode.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Health & Medical Sciences (AREA)
• Otolaryngology (AREA)
• Signal Processing (AREA)
• Multimedia (AREA)
• Circuit For Audible Band Transducer (AREA)
• Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
• Details Of Audible-Bandwidth Transducers (AREA)

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• 2007
  • 2007-07-26 FR FR0756759A patent/FR2919454B1/fr not_active Expired - Fee Related
• 2008
  • 2008-07-21 JP JP2010517446A patent/JP5405461B2/ja not_active Expired - Fee Related
  • 2008-07-21 CN CN2008801003029A patent/CN101816189B/zh not_active Expired - Fee Related
  • 2008-07-21 WO PCT/FR2008/001076 patent/WO2009043994A1/fr active Application Filing
  • 2008-07-21 EP EP08835842A patent/EP2172057A1/fr not_active Withdrawn
  • 2008-07-21 US US12/670,214 patent/US8391510B2/en not_active Expired - Fee Related

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