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EP0335892A1 - Method for correcting the amplitude/frequency response of an electro-acoustic transducing system and corresponding transducer assembly. - Google Patents

Method for correcting the amplitude/frequency response of an electro-acoustic transducing system and corresponding transducer assembly.

Info

Publication number
EP0335892A1
EP0335892A1 EP88900235A EP88900235A EP0335892A1 EP 0335892 A1 EP0335892 A1 EP 0335892A1 EP 88900235 A EP88900235 A EP 88900235A EP 88900235 A EP88900235 A EP 88900235A EP 0335892 A1 EP0335892 A1 EP 0335892A1
Authority
EP
European Patent Office
Prior art keywords
transducers
transducer
frequency
amplitude
electro
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.)
Granted
Application number
EP88900235A
Other languages
German (de)
French (fr)
Other versions
EP0335892B1 (en
Inventor
Clement Eloise-Pillerault
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.)
Individual
Original Assignee
Individual
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 Individual filed Critical Individual
Priority to AT88900235T priority Critical patent/ATE91838T1/en
Publication of EP0335892A1 publication Critical patent/EP0335892A1/en
Application granted granted Critical
Publication of EP0335892B1 publication Critical patent/EP0335892B1/en
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 
    • 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
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/227—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only  using transducers reproducing the same frequency band
    • 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
    • H04R1/2884—Reduction of undesired resonances, i.e. standing waves within enclosure, or of undesired vibrations, i.e. of the enclosure itself by means of the enclosure structure, i.e. strengthening or shape of the enclosure
    • H04R1/2888—Reduction of undesired resonances, i.e. standing waves within enclosure, or of undesired vibrations, i.e. of the enclosure itself by means of the enclosure structure, i.e. strengthening or shape of the enclosure for loudspeaker transducers

Definitions

  • the invention relates to the field of electro-acoustic transducers, in particular transducers consisting of at least one loudspeaker mounted in a resonant acoustic enclosure, intended to be Q connected at the output of an electrical modulation source to restore the sound signal. corresponding.
  • the subject of the invention is a method for equalizing the amplitude / frequency response of this type of transducer. It also provides a - new transducer assembly making it possible to operate according to the invented method, as well as preferred modes of use of the new transducer assembly.
  • equalizers are generally selective networks, most often incorporated in the acoustic enclosure, and intended to correct the electrical input signal from the transducer, to compensate for irregularities in the amplitude / frequency response of the loudspeakers.
  • This equalization method is for example carried out by using passive anti-resonant circuits inserted between the amplifier and the acoustic enclosure, and effecting a selective weakening of the output signal of the amplifier.
  • the filters themselves are a distortion factor of the signal, due to the r unable to give them a perfect linear transfer function in their bandwidth. They are also subject to variations in their response characteristics as a function of the ambient temperature, or even of their aging.
  • equalization circuits brings constraints in this. which relates to the characteristics of the loudspeaker corrected to avoid unfavorable indirect effects, such as for example the damping of the loudspeaker (cf. "Engineering technique”; E 2613-9; paragraphs 2, 32).
  • the equalization of the response curve of the electro-acoustic transducers is also approached by making precise choices on the parameters of the enclosure, in relation to the parameters of the speaker (s) mounted in the enclosure.
  • FIG. 3 represents the uncorrected response curve (curve A) characteristic of known transducers, and the response curve after correction (curve B), using known techniques, such as for example the so-called “Thiele and Small” techniques.
  • this involves acting on the resonance frequency, the overvoltage coefficient, or even the equivalent volume (V as ) of the loudspeaker, in relation to techniques for damping acoustic phenomena. speaker noise, for example by stuffing its internal walls with a "choking" material (glass wool).
  • these known techniques do not have a homogeneous effect on the entire frequency spectrum, owing to the fact that the cyclic weakening phenomena introduced by the transducers are very different in the low frequency domain (less than 300 Hz ) compared to higher frequencies.
  • the known damping techniques then act relatively effectively at low frequencies, owing to the fact that the responsibility of the loudspeaker in the irregularities of the level of restitution of sound signal is preponderant, on the other hand, the correction of the irregularities in the field of mediums. and treble, that is to say where the parameters related to the constitution of the speaker are predominant, is much less well performed.
  • the objective of the present invention is therefore to overcome these various drawbacks of the existing equalization methods.
  • a first object of the invention is to provide a method for correcting the amplitude / frequency response curve of the electro-acoustic transducers, without affecting the efficiency of the electric amplifier + electro-acoustic transducer system.
  • a second object of the invention is to provide such a correction method applicable whatever the specific response curve of the transducers. electro-acoustic used, provided that their amplitude / frequency response curve presents "cyclic" irregularities around an average value of the level of restitution of the sound signal.
  • a complementary object of the invention is to provide an equalization method which operates over the entire spectrum of the audible frequency spectrum, in particular up to the highest fundamental sounds (4000 Hz).
  • electro-acoustic transducer in the form of a succession of alternations of axima and minima levels; in that said electro-acoustic transducer is used in cooperation with at least one second electro-acoustic transducer connected in parallel to the same modulation source, and operating on the same frequency range, said second electro-acoustic transducer
  • D acoustipque being chosen so that it has an amplitude / frequency response curve complementary to that of the first transducer, to form by adding the sound signals of said transducers, a resulting sound signal corrected due to the mutual compensation of the irregularities inherent in each transducer .
  • said transducer will exhibit all the more “exploitable” natural irregularities as its efficiency is high, that is to say that it is devoid of any damping device and is at its maximum sensitivity.
  • the second transducer a transducer identical to the first transducer is used, said second transducer having an adjustable resonant frequency so as to allow an offset of its response curve relative to that of the first transducer, to achieve mutual compensation of their respective irregularities.
  • the response curve of said second transducer is shifted by action on one of the following parameters: value and configuration of the volume of the enclosure; modification of the air flow in one or more vents made in the enclosure; modification of the characteristics of a passive speaker mounted in the enclosure of the adjustable electro-acoustic transducer.
  • the equalization process thus defined can be implemented in particular in a set of twin transducers, consisting of two speakers each provided with at least one speaker, said speakers having a common wall at least a portion of which is movable so as to adjust the volume of each of said speakers.
  • FIG. 1 shows the implementation of the method according to the invention in a set of two Hel holtz cavities, each provided with a loudspeaker, and having a common side wall;
  • FIG. 2 shows the implementation of 1'invention in a set of two paired cavities Helmholtz and J each provided a loudspeaker, and having a common bottom wall;
  • FIG. 3 shows the response curves A and B, before and after correction according to known techniques respectively, for a conventional transducer of the type with enclosure fitted with a loudspeaker;
  • FIG. 4 represents the offset of the amplitude / frequency response curves of two paired electro-acoustic transducers according to the method of the present invention;
  • FIG. 5 represents the resulting curve of equalized amplitude / frequency response for the transducers of FIG. 4 (curve D), in comparison with the curve obtained by using known techniques (curve B).
  • FIG. 4 illustrates the fundamental principle of the production method according to the invention.
  • the response curve A corresponds to a first electro-acoustic transducer intended to operate for example over a range I of frequencies ranging from 60 Hz to 3000 Hz or more.
  • This response curve presents alternating irregularities, which result in a variation in the level of sound reproduction (ordinate axis in dB), around an average level 1 ⁇ located around + 2 dB, in the case shown.
  • the principle of the equalization method according to the invention consists in using at least one second electro-acoustic transducer, in cooperation with the first, the second transducer being chosen so as to have a response curve C similar to the response curve A of the first transducer, but offset from it.
  • the offset of the two response curves A and C corresponds substantially to the value of a half-period of the irregularity cycles of the transducers. It follows that the frequency intervals for which the response curve A of the first transducer exhibits a significant relative attenuation substantially correspond to a maximum level of restitution of the response curve C of the second associated transducer.
  • the restored signal corresponding to the addition of the signals coming from each of the transducers is therefore equalized over the entire frequency spectrum, by mutual compensation of the irregular response curves of each transducer.
  • the equalization of the resulting restored signal will be all the more perfect when the following two conditions are met.
  • the mutual compensation of the irregularities of the response curves A and C of the twin electro-acoustic transducers will only be effective if the irregularities in question are of alternating shape, that is to say that they occur under the form of a succession of attenuations and maximum levels, at intervals which coincide with frequency.
  • the irregularities must be in the form of alternation of attenuations and maximum levels, of substantially equal amplitude around an average level of restitution for each pair of neighboring positive and negative alternations, of so that the offset of curves C and A by about half a period makes the positive alternations of one curve coincide with the negative alternations of the other, according to the method, exact coincidence is of course advantageous, but results are extremely satisfactory from the point of view of equalization are obtained even for approximate coincidences.
  • FIG. 4 constitutes an illustration for demonstrative purpose of the basic principle applied in the equalization method according to the invention.
  • it has been found experimentally that a completely satisfactory equalization is obtained even if the succession of positive and negative alternations of the amplitude / frequency response curves of the transducers is not carried out according to regular periods, or if variations in amplitude of these alternations are relatively uneven.
  • Another essential advantage of the invention is shown in FIG.
  • the implementation of the equalization method according to the invention provides an extremely precise method of adjusting the tone, or even the timbre, audio signals reproduced.
  • This extremely advantageous characteristic of the invention adds to the equalization effect.
  • compensation is in the form of a transducer adjustment system, which makes it possible to adapt the same set of transducers to the compensated reproduction of signals recorded using different techniques.
  • Examples include the generation of sound effects on sounds produced by electronic instruments, or the adaptation of transducers to the acoustics of the listening room.
  • Figures 1 and 2 show preferred embodiments, of course not limiting, of sets of electro-acoustic transducers implementing the equalization method according to the invention.
  • transducers of the Helmholtz cavity type each provided with a loudspeaker and a vent.
  • the method according to the invention applies to any type of transducer, provided that the amplitude / frequency response curve which corresponds to it at least partially satisfies the two conditions highlighted above.
  • the implementation of the equalization process is obtained by using two Helmholtz cavities 10 and 20, each provided with a loudspeaker 11-21, and a vent 12-22 .
  • the cavities 10-20 are paired so as to present a common side wall 15.
  • the two cavities have identical, or almost identical, characteristics. This means that they each have a response curve amplitude / frequency of substantially identical configuration, in particular from the point of view of the frequency of succession of the irregularities, and of the amplitude of the half-waves.
  • the adjustment of the offset of the response curves allowing the equalization according to the invention is carried out here by adjusting the resonant frequency of the transducers. More specifically, a coarse adjustment is performed by movement of the wall 15, and a fine adjustment by movement of the lower block 16. These movements are made for example 'through systems threaded-rod nuts 17, 18; 37, 38 controlled by flywheels 19, 39 mounted on an outer wall of the twin cavities.
  • the modification of the resonant frequency of each of the two paired transducers is carried out by modification of the configuration and of the internal volume of the two cavities 10-20 respectively, from the made of the displacement of the wall portion 16.
  • the effect obtained can be illustrated from FIG. 4. It can in fact be considered that the curve A corresponds to the amplitude / frequency response curve of the transducer 1, and that the curve C corresponds to the amplitude / frequency response curve of the second transducer 2.
  • the resonance frequency f 2 of the transducer 2 is around 40 Hz.
  • the resonance frequency corresponds to a point on the weakening slope characteristic of any acoustic resonant system (slope of the order of 18 dB per octave), on the amplitude / frequency response curve.
  • the response curve A of the transducer 1 remains fixed, the effect of the displacement of the articulated portion 16 of the common wall 15 on the offset of the curve C will be illustrated approximately by the curve d f .
  • This curve d f is in fact traversed by the point P of the resonant frequency of the transducer 2, on the response curve C, when the internal volume of the cavity 20 of the transducer 2 is varied.
  • This curve d f illustrates 1 • influence of the variation in the volume of the cavity 20 on two essential parameters:
  • the increase in the volume of the resonant cavity 20 causes the resonance point P to rise towards the first maximum of the response curve C.
  • FIG. 1 allows adjustment of the equalization by varying the volume of the enclosure, thanks to the displacement of a portion of the common wall.
  • the dimensions of the articulated wall portion 16 are not a limiting characteristic of the invention, and must be adapted to the characteristics of the transducer, and to the desired adjustment precision. In particular, it is possible to plan
  • ⁇ D example by action on a shutter (not shown) closing the vent more or less completely, or even by adding a neck of adjustable length or shape.
  • Another technique for adjusting the resonance frequency of at least one of the transducers consists in
  • the adjustment then consists in controlling the resonant frequency of the diaphragm, by acting on its mass, on the elastic return force of the diaphragm, or by any other means.
  • the action on the flow of air through the vent can be considered, in certain applications, as less advantageous than the action on the volume of the cavities: a variation in the volume of the resonant cavity has indeed in general no influence on the transducer efficiency, unlike the action techniques on the vent.
  • the two transducers of the same set can perfectly be completely separate from each other, and therefore not have a common wall.
  • FIG. 2 represents a variant of the embodiment of. FIG. 1, in which two transducers 3, 4, of the Helmholtz cavity type, are paired by presenting a movable common bottom wall. Each of the transducers is provided with a speaker 31-41, and a vent 32-42.
  • the common movable internal partition 35 is inclined, so as to avoid the unfavorable effects of reflection which would be induced by a straight partition, and would imply the use of a damping technique detrimental to performance.
  • a prototype corresponding to this figure was produced by means of a box, the total interior volume of which (covering the cavities of the transducers 3 and 4) was 80 liters.
  • the two speakers are similar, and had an overall diameter of 190 mm.
  • the nominal surface of each of the vents, 2.5 dm 2 is adjusted by a flap.
  • This implementation configuration of the method of the invention has the advantage of combining the equalization phenomenon already described, with a second phenomenon of controlling the directivity of the acoustic radiation of the system.
  • This directivity control is obtained by supplying the two transducers 3, 4 from the same modulation source, but by actuating them simultaneously in phase shift, preferably in phase opposition.
  • Control of the directivity can then be obtained by acting on one or other of the parameters such as: the value of the phase shift (constant or not as a function of the frequency); the orientation of the emission of each transducer; the intensity and the lobe of their radiation; the distances between transmitters; the range of frequencies concerned; among others.
  • the embodiment of FIG. 2 is extremely advantageous when it is desired to have a possibility of adjusting the equalization of the restored sound signal, combined with a directivity effect, and possibly with a possibility of action. on the tone, all this being possible without affecting the performance of the installation.
  • a completely preferential application of this electro-acoustic transducer system is the high power sound system of congress halls, concert halls, or more generally of any public event.

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  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Transducers For Ultrasonic Waves (AREA)
  • Amplifiers (AREA)
  • Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)

Abstract

The field of the invention is that of electro-acoustic transducers. The aim is to provide an equalization method, and more generally a method for correcting the restored signal, without affecting the output of the transducers. This aim is reached with a method using at least two transducers, the second transducer (2) being so selected as to have a response amplitude/frequency curve (C) which is substantially complementary to that (A) of the first transducer (1) in order to form by adding sound signals from said transducers a resulting corrected sound signal, due to the mutual compensation of irregularities inherent to each curve (A), (C). A preferred application of such electro-acoustic transducer system is the high power sound production in congress and concert halls, or more generally the provision of sounds in any place where a public event is held.

Description

"Procédé d'égalisation de la réponse amplitude/fréquence d'un ensemble transducteur électro- acoustiαue, ensemble transducteur correspondant". "Method for equalizing the amplitude / frequency response of an electro-acoustic transducer assembly, corresponding transducer assembly".
5 DOMAINE DE L'INVENTION5 FIELD OF THE INVENTION
L'invention concerne le domaine des transducteurs électro-acoustiques, notamment les transducteurs constitués d'au moins un haut-parleur monté dans une enceinte acoustique résonnante, destinés à être Q branchés en sortie d'une source électrique de modulation pour restituer le signal sonore correspondant.The invention relates to the field of electro-acoustic transducers, in particular transducers consisting of at least one loudspeaker mounted in a resonant acoustic enclosure, intended to be Q connected at the output of an electrical modulation source to restore the sound signal. corresponding.
Plus précisément, l'invention a pour objet un procédé d'égalisation de la réponse amplitude/fréquence de ce type de, transducteurs. Elle fournit également un - nouvel ensemble transducteur permettant de fonctionner selon le procédé inventé, ainsi que des modes d'utilisation préférentiels de l'ensemble transducteur nouveau.More specifically, the subject of the invention is a method for equalizing the amplitude / frequency response of this type of transducer. It also provides a - new transducer assembly making it possible to operate according to the invented method, as well as preferred modes of use of the new transducer assembly.
ETAT DE LA TECHNIQUESTATE OF THE ART
Jusqu'à présent, le problème de l'égalisation de la réponse amplitude/fréquence des transducteurs électro-acoustiques, autrement dit du niveau de sortie du signal sonore en fonction de la fréquence, était résolu par l'emploi de circuits spécifiques actifs ou passifs, appelés égaliseurs. Il s'agit généralement de réseaux sélectifs, incorporés le plus souvent dans l'enceinte acoustique, et destinés à corriger le signal électrique d'entrée du transducteur, pour compenser les irrégularités de la réponse amplitude/fréquence des haut- parleurs. Cette méthode d'égalisation est par exemple réalisée par utilisation de circuits passifs anti- résonnants insérés entre l'amplificateur et l'enceinte acoustique, et réalisant un affaiblissement sélectif du signal de sortie de l'amplificateur. Du fait que le principe de fonctionnement de ces égaliseurs connus consiste à assurer un affaiblissement dudit signal électrique, il en résulte que ces systèmes présentent 1'inconvénient de diminuer le rendement de l'ensemble amplificateur + enceinte acoustique. L'affaiblissement doit être compensé par un surcroit d'amplification, et implique l'utilisation de composants travaillant à plus grande puissance, avec des exigences accrues de qualité pour éviter la distorsion.Until now, the problem of equalizing the amplitude / frequency response of electro-acoustic transducers, in other words the output level of the sound signal as a function of frequency, was solved by the use of specific active or passive circuits. , called equalizers. These are generally selective networks, most often incorporated in the acoustic enclosure, and intended to correct the electrical input signal from the transducer, to compensate for irregularities in the amplitude / frequency response of the loudspeakers. This equalization method is for example carried out by using passive anti-resonant circuits inserted between the amplifier and the acoustic enclosure, and effecting a selective weakening of the output signal of the amplifier. Because the operating principle of these known equalizers consists in ensuring a weakening of said electrical signal, it follows that these systems have the drawback of reducing the efficiency of the amplifier + speaker assembly. The weakening must be compensated for by an increase in amplification, and involves the use of components working at higher power, with increased quality requirements to avoid distortion.
Les filtres eux-mêmes sont un facteur de distorsion du signal, du fait de lrimpossibilité de leur conférer une fonction de transfert parfaitement linéaire dans leur bande passante. Ils sont en outre sujets à des variations de leurs caractéristiques de réponse en fonction de la température ambiante, ou même de leur vieillissement.The filters themselves are a distortion factor of the signal, due to the r unable to give them a perfect linear transfer function in their bandwidth. They are also subject to variations in their response characteristics as a function of the ambient temperature, or even of their aging.
De plus, l'utilisation de circuits d'égalisation amène des contraintes en ce. qui concerne les caractéristiques du haut-parleur corrigé pour éviter les effets indirects défavorables, comme par exemple le désamortissement du haut-parleur (cf. "Technique de l'Ingénieur" ; E 2613-9 ; paragraphes 2, 32). De façon connue, l'égalisation de la courbe de réponse des transducteurs électro-acoustiques est également approchée en effectuant des choix précis sur les paramètres de l'enceinte, en relation avec les paramètres du ou des haut-parleurs montés dans l'enceinte.In addition, the use of equalization circuits brings constraints in this. which relates to the characteristics of the loudspeaker corrected to avoid unfavorable indirect effects, such as for example the damping of the loudspeaker (cf. "Engineering technique"; E 2613-9; paragraphs 2, 32). In known manner, the equalization of the response curve of the electro-acoustic transducers is also approached by making precise choices on the parameters of the enclosure, in relation to the parameters of the speaker (s) mounted in the enclosure.
La figure 3 représente la courbe de réponse non corrigée (courbe A) caractéristique des transducteurs connus, et la courbe de réponse après correction (courbe B) , en utilisant les techniques connues, comme par exemple les techniques dites de "Thiele et Small". Il s'agit en général d'agir sur la fréquence de résonance, le coefficient de surtension, ou encore le volume équivalent (Vas) du haut-parleur, en relation avec des techniques d'amortissement des phénomènes acoustiques parasites d'enceintes, par exemple par bourrage de ses parois internes à l'aide d'un matériau "d'étouffement" (laine de verre) .FIG. 3 represents the uncorrected response curve (curve A) characteristic of known transducers, and the response curve after correction (curve B), using known techniques, such as for example the so-called "Thiele and Small" techniques. In general, this involves acting on the resonance frequency, the overvoltage coefficient, or even the equivalent volume (V as ) of the loudspeaker, in relation to techniques for damping acoustic phenomena. speaker noise, for example by stuffing its internal walls with a "choking" material (glass wool).
Or, on constate à la lecture de la courbe résultante B après correction, que ces techniques connues abaissent le niveau de la puissance sonore restituée par le transducteur : cet affaiblissement peut atteindre jusqu'à 5 dB et davantage, ce qui est considérable.However, it can be seen from reading the resulting curve B after correction, that these known techniques lower the level of sound power restored by the transducer: this attenuation can reach up to 5 dB and more, which is considerable.
D'autre part, ces techniques connues n'ont pas un effet homogène sur la totalité du spectre de fréquence, du fait que les phénomènes d'affaiblissement cycliques introduits par les transducteurs sont très différents dans le domaine des basses fréquences (inférieures à 300 Hz) par rapport aux fréquences supérieures. Les techniques d'amortissement connues agissent alors de façon relativement efficace aux basses fréquences, du fait que la responsabilité de l'enceinte dans les irrégularités du niveau de restitution de signal sonore est prépondérante, en revanche, la correction des irrégularités dans le domaine des médium et des aigus, c'est-à-dire là où les paramètres liés à la constitution du haut-parleur sont prépondérants, est nettement moins bien réalisée.On the other hand, these known techniques do not have a homogeneous effect on the entire frequency spectrum, owing to the fact that the cyclic weakening phenomena introduced by the transducers are very different in the low frequency domain (less than 300 Hz ) compared to higher frequencies. The known damping techniques then act relatively effectively at low frequencies, owing to the fact that the responsibility of the loudspeaker in the irregularities of the level of restitution of sound signal is preponderant, on the other hand, the correction of the irregularities in the field of mediums. and treble, that is to say where the parameters related to the constitution of the speaker are predominant, is much less well performed.
OBJECTIFS DE L'INVENTION l'objectif de la présente invention est donc de pallier ces différents inconvénients des procédés d'égalisation existants.OBJECTIVES OF THE INVENTION the objective of the present invention is therefore to overcome these various drawbacks of the existing equalization methods.
Plus précisément, un premier objet de 1'invention est de fournir un procédé de correction de la courbe de réponse amplitude/fréquence des transducteurs électro-acoustiques, sans obérer le rendement du système amplificateur électrique + transducteur électro¬ acoustique.More specifically, a first object of the invention is to provide a method for correcting the amplitude / frequency response curve of the electro-acoustic transducers, without affecting the efficiency of the electric amplifier + electro-acoustic transducer system.
Un second objet de l'invention est de fournir un tel procédé de correction applicable quelle que soit la courbe de réponse spécifique des transducteurs électro-acoustiques utilisés, pourvu que leur courbe de réponse amplitude/fréquence présente des irrégularités "cycliques" autour d'une valeur moyenne du niveau de restitution du signal sonore.A second object of the invention is to provide such a correction method applicable whatever the specific response curve of the transducers. electro-acoustic used, provided that their amplitude / frequency response curve presents "cyclic" irregularities around an average value of the level of restitution of the sound signal.
Un objet complémentaire de 1'invention est de fournir un procédé d'égalisation qui fonctionne sur toute l'étendue du spectre des fréquences audibles, notamment jusqu'aux sons fondamentaux les plus élevés (4000 Hz) .A complementary object of the invention is to provide an equalization method which operates over the entire spectrum of the audible frequency spectrum, in particular up to the highest fundamental sounds (4000 Hz).
De plus, comme on le verra ci-après, le procédé suivant 1•invention a également pour avantage deIn addition, as will be seen below, the process according to the invention also has the advantage of
10 permettre d'agir de façon très fine sur la tonalité ou le timbre du signal sonore restitué par les transducteurs. Cette caractéristique assez surprenante permet ainsi par exemple d'obtenir des effets sonores diversifiés par réglage des transducteurs, ou encore de compenser des10 allow very fine action on the tone or timbre of the sound signal reproduced by the transducers. This rather surprising characteristic thus makes it possible for example to obtain diversified sound effects by adjusting the transducers, or even to compensate for
15 défauts affectant le signal sonore émis, ces défauts pouvant par exemple résulter de la technique d'enregistrement du signal, ou encore de l'acoustique de la salle d'écoute.15 faults affecting the sound signal emitted, these faults could for example result from the signal recording technique, or from the acoustics of the listening room.
CARACTERISTIQUES ESSENTIELLES DE L'INVENTIONESSENTIAL CHARACTERISTICS OF THE INVENTION
Ces objectifs et avantages de l'invention,These objectives and advantages of the invention,
20 ainsi que d'autres qui apparaîtront par la suite, sont obtenus à l'aide d'un procédé de correction de la réponse amplitude/fréquence d'un transducteur électro-acoustique, notamment du type formé d'un haut-parleur monté dans une enceinte résonnante, et destiné à être branché en sortie d'une source électrique de modulation pour restituer le signal sonore correspondant, procédé caractérisé en ce qu'on choisit un transducteur dont les irrégularités de la courbe de réponse amplitude/fréquence se présentent20 as well as others which will appear subsequently, are obtained using a method for correcting the amplitude / frequency response of an electro-acoustic transducer, in particular of the type formed by a loudspeaker mounted in a resonant enclosure, and intended to be connected at the output of an electrical modulation source to reproduce the corresponding sound signal, a process characterized in that a transducer is chosen whose irregularities of the amplitude / frequency response curve are present
30 sous la forme d'une succession d'alternances de niveaux axima et minima ; en ce qu'on utilise ledit transducteur électro-acoustique en coopération avec au moins un second transducteur électro-acoustique branché en parallèle sur la même source de modulation, et fonctionnant sur la même gamme de fréquences, ledit second transducteur électro-30 in the form of a succession of alternations of axima and minima levels; in that said electro-acoustic transducer is used in cooperation with at least one second electro-acoustic transducer connected in parallel to the same modulation source, and operating on the same frequency range, said second electro-acoustic transducer
D acoustipque étant choisi de façon qu'il présente une courbe de réponse amplitude/fréquence complémentaire de celle du premier transducteur, pour former par addition des signaux sonores desdits transducteurs, un signal sonore résultant corrigé du fait de la compensation mutuelle des irrégularités inhérentes à chaque transducteur.D acoustipque being chosen so that it has an amplitude / frequency response curve complementary to that of the first transducer, to form by adding the sound signals of said transducers, a resulting sound signal corrected due to the mutual compensation of the irregularities inherent in each transducer .
On notera que ledit transducteur présentera d'autant plus d'irrégularités naturelles "exploitables" que son rendement est élevé, c'est-à-dire qu'il est dépourvu de tout dispositif d'amortissement et se trouve à son maximum de sensibilité.It will be noted that said transducer will exhibit all the more “exploitable” natural irregularities as its efficiency is high, that is to say that it is devoid of any damping device and is at its maximum sensitivity.
De façon préférentielle, on utilise comme second transducteur, un transducteur identique au premier transducteur, ledit second transducteur présentant une fréquence de résonance ajustable de façon à permettre un décalage de sa courbe de réponse par rapport à celle du premier transducteur, pour réaliser la compensation mutuelle de leurs irrégularités respectives.Preferably, as the second transducer, a transducer identical to the first transducer is used, said second transducer having an adjustable resonant frequency so as to allow an offset of its response curve relative to that of the first transducer, to achieve mutual compensation of their respective irregularities.
De façon avantageuse, et lorsque lesdits transducteurs sont du type enceinte + haut-parleur, le décalage de la courbe de réponse dudit second transducteur est réalisé par action sur l'un des paramètres suivants : valeur et configuration du volume de l'enceinte ; modification de l'écoulement de l'air dans un ou plusieurs évents réalisés dans l'enceinte ; modification des caractéristiques d'un haut-parleur passif monté dans l'enceinte du transducteur électro¬ acoustique ajustable. Ces paramètres sont donnés à titre d'exemples non limitatifs, et l'homme du métier est à même d'utiliser tout autre moyen d'ajustement de la fréquence de résonance de l'enceinte du ou des transducteurs ajustables.Advantageously, and when said transducers are of the enclosure + loudspeaker type, the response curve of said second transducer is shifted by action on one of the following parameters: value and configuration of the volume of the enclosure; modification of the air flow in one or more vents made in the enclosure; modification of the characteristics of a passive speaker mounted in the enclosure of the adjustable electro-acoustic transducer. These parameters are given by way of nonlimiting examples, and a person skilled in the art is able to use any other means of adjusting the resonant frequency of the enclosure of the adjustable transducer (s).
Selon l'invention, le procédé d'égalisation ainsi défini peut être notamment mis en oeuvre dans un jeu de transducteurs jumelés, constitués de deux enceintes munies chacune d'au moins un haut-parleur, lesdites enceintes présentant une paroi commune dont au moins une portion est déplaçable de façon à ajuster le volume de chacune desdites enceintes.According to the invention, the equalization process thus defined can be implemented in particular in a set of twin transducers, consisting of two speakers each provided with at least one speaker, said speakers having a common wall at least a portion of which is movable so as to adjust the volume of each of said speakers.
ENONCE DES FIGURESSTATEMENT OF FIGURES
D'autres caractéristiques et avantages de 1'invention apparaîtront à la lecture de la description suivante de quelques modes de réalisation préférentiels de l'invention, donnés à titre d'exemples non limitatifs et des dessins annexés dans lesquels :Other characteristics and advantages of the invention will appear on reading the following description of some preferred embodiments of the invention, given by way of nonlimiting examples and the appended drawings in which:
- la figure 1 représente la mise en oeuvre du procédé selon 1'invention dans un jeu de deux cavités de Hel holtz, munies chacune d'un haut-parleur, et présentant une paroi latérale commune ;- Figure 1 shows the implementation of the method according to the invention in a set of two Hel holtz cavities, each provided with a loudspeaker, and having a common side wall;
- la figure 2 représente la mise en oeuvre de 1'invention dans un jeu de deux cavités de Helmholtz jumelées et munies chacune dJun haut-parleur, et présentant une paroi commune de fond ;- Figure 2 shows the implementation of 1'invention in a set of two paired cavities Helmholtz and J each provided a loudspeaker, and having a common bottom wall;
- la figure 3 représente les courbes de réponse A et B, avant et après correction suivant les techniques connues respectivement, pour un transducteur classique du type à enceinte munie d'un haut-parleur ; la figure 4 représente le décalage des courbes de réponse amplitude/fréquence de deux transducteurs électro-acoustiques jumelés suivant le procédé de la présente invention ;- Figure 3 shows the response curves A and B, before and after correction according to known techniques respectively, for a conventional transducer of the type with enclosure fitted with a loudspeaker; FIG. 4 represents the offset of the amplitude / frequency response curves of two paired electro-acoustic transducers according to the method of the present invention;
- la figure 5 représente la courbe résultante de réponse égalisée amplitude/fréquence pour les transducteurs de la figure 4 (courbe D) , en comparaison avec la courbe obtenue par utilisation des techniques connues (courbe B) .FIG. 5 represents the resulting curve of equalized amplitude / frequency response for the transducers of FIG. 4 (curve D), in comparison with the curve obtained by using known techniques (curve B).
DESCRIPTION DE MODES DE REALISATIONS DETAILLEES DE L'INVENTIONDESCRIPTION OF DETAILED EMBODIMENTS OF THE INVENTION
La figure 4 illustre le principe fondamental du procédé de réalisation suivant l'invention. La courbe de réponse A correspond à un premier transducteur électro-acoustique destiné à fonctionner par exemple sur une plage I de fréquences allant de 60 Hz à 3000 Hz ou davantage. Cette courbe de réponse présente des irrégularités alternées, qui se traduisent par une variation du niveau de restitution sonore (axe des ordonnées en dB) , autour d'un niveau moyen 1^ situé aux alentours de + 2 dB, dans le cas représenté.FIG. 4 illustrates the fundamental principle of the production method according to the invention. The response curve A corresponds to a first electro-acoustic transducer intended to operate for example over a range I of frequencies ranging from 60 Hz to 3000 Hz or more. This response curve presents alternating irregularities, which result in a variation in the level of sound reproduction (ordinate axis in dB), around an average level 1 ^ located around + 2 dB, in the case shown.
En l'absence de correction, le signal sonore perçu par 1•auditeur est donc altéré par les affaiblissements relatifs du signal sur de faibles intervalles de fréquence répartis sur tout le spectre du signal restitué.In the absence of correction, the audible signal perceived by the listener is therefore altered by the relative attenuations of the signal over small frequency intervals distributed over the whole spectrum of the restored signal.
Le principe du procédé d'égalisation suivant l'invention consiste à utiliser au moins un second transducteur électro-acoustique, en coopération avec le premier, le second transducteur étant choisi de façon à présenter une courbe de réponse C similaire à la courbe de réponse A du premier transducteur, mais décalé par rapport à celle-ci.The principle of the equalization method according to the invention consists in using at least one second electro-acoustic transducer, in cooperation with the first, the second transducer being chosen so as to have a response curve C similar to the response curve A of the first transducer, but offset from it.
Le décalage des deux courbes de réponse A et C correspond sensiblement à la valeur d'une demi-période des cycles d'irrégularité des transducteurs. Il en résulte que les intervalles de fréquence pour lesquels la courbe de réponse A du premier transducteur présente un affaiblissement relatif important correspondent sensiblement à un niveau de restitution maximal de la courbe de réponse C du second transducteur associé.The offset of the two response curves A and C corresponds substantially to the value of a half-period of the irregularity cycles of the transducers. It follows that the frequency intervals for which the response curve A of the first transducer exhibits a significant relative attenuation substantially correspond to a maximum level of restitution of the response curve C of the second associated transducer.
Le signal restitué correspondant à l'addition des signaux provenant de chacun des transducteurs est donc égalisé sur tout le spectre de fréquence, par la compensation mutuelle des courbes de réponse irrégulières de chaque transducteur. l'égalisation du signal résultant restitué sera d'autant plus parfaite que les deux conditions suivantes seront réunies. Tout d'abord, la compensation mutuelle des irrégularités des courbes de réponse A et C des transducteurs électro-acoustiques jumelés ne sera effective que si les irrégularités en question sont de forme alternée, c'est-à-dire qu'elles se présentent sous la forme d'une succession d'affaiblissements et de niveaux maximaux, à des intervalles qui coïncident en fonction de la fréquence. En d'autres termes, il faut que les irrégularités soient sous forme d'alternance d'affaiblissements et de niveaux maxima, d'amplitude sensiblement égale autour d'un niveau moyen de restitution pour chaque paire d'alternances positive et négative voisines, de façon que le décalage des courbes C et A d'une demi-période environ fasse coïncider les alternances positives d'une courbe avec les alternances négatives de l'autre, selon le procédé, la coïncidence exacte est bien entendu avantageuse, mais des résultats extrêmement satisfaisants du point de vue de l'égalisation sont obtenus même pour des coïncidences approximatives.The restored signal corresponding to the addition of the signals coming from each of the transducers is therefore equalized over the entire frequency spectrum, by mutual compensation of the irregular response curves of each transducer. the equalization of the resulting restored signal will be all the more perfect when the following two conditions are met. First of all, the mutual compensation of the irregularities of the response curves A and C of the twin electro-acoustic transducers will only be effective if the irregularities in question are of alternating shape, that is to say that they occur under the form of a succession of attenuations and maximum levels, at intervals which coincide with frequency. In other words, the irregularities must be in the form of alternation of attenuations and maximum levels, of substantially equal amplitude around an average level of restitution for each pair of neighboring positive and negative alternations, of so that the offset of curves C and A by about half a period makes the positive alternations of one curve coincide with the negative alternations of the other, according to the method, exact coincidence is of course advantageous, but results are extremely satisfactory from the point of view of equalization are obtained even for approximate coincidences.
La seconde condition qui doit être remplie au moins partiellement pour obtenir une égalisation satisfaisante est, comme déjà suggéré ci-dessus, la complémentarité des amplitudes de chaque demi-alternance adjacente, considérées par rapport au niveau moyen de restitution, de façon que la somme algébrique des courbes de réponse A et C des transducteurs jumelés fournisse un niveau résultant égalisé. A cet égard, il n'est pas nécessaire que les irrégularités de chaque courbe de réponse amplitude/fréquence présentent des écarts de niveau constants sur tout le spectre des fréquences. On obtiendra une compensation satisfaisante par décalage des courbes pourvu que la variation de l'écart de niveau d'une alternance à la suivante soit progressive. Cette caractéristique avantageuse de 1»invention est illustrée en figure 4, où l'on peut constater que les amplitudes des alternances représentées diffèrent notablement, par exemple entre les gammes 50-100 Hz (environ 8 dB) et la gamme 1600-3200 Hz (1 dB) .The second condition which must be fulfilled at least partially to obtain a satisfactory equalization is, as already suggested above, the complementarity of the amplitudes of each adjacent half-wave, considered with respect to the average level of restitution, so that the algebraic sum response curves A and C of the twin transducers provide an equalized resulting level. In this respect, it is not necessary that the irregularities of each amplitude / frequency response curve exhibit constant level deviations over the entire frequency spectrum. Satisfactory compensation will be obtained by shifting the curves provided that the variation in the level difference from one alternation to the next is gradual. This advantageous characteristic of 1 »invention is illustrated in Figure 4, where it can be seen that the amplitudes alternations shown differ significantly, for example between the ranges 50-100 Hz (about 8 dB) and the range 1600-3200 Hz (1 dB).
Il est important de noter que la figure 4 constitue une illustration à but démonstratif du principe de base appliqué dans le procédé d'égalisation suivant l'invention. En fait, il faut noter que l'on a pu constater expérimentalement qu'une égalisation tout à fait satisfaisante est obtenue même si la succession des alternances positives et négatives des courbes de réponse d'amplitude/fréquence des transducteurs ne s'effectue pas selon des périodes régulières, ou si des variations d'amplitude de ces alternances sont relativement accidentées. Cela signifie que, même si le procédé suivant 1'invention ne fournit pas un effet de réalisation parfait du point de vue arithmétique, il est tout à fait satisfaisant du point de vue phsycho-auditif. Un autre avantage essentiel de 1'invention est représenté en figure 5, où sont portées sur un diagramme de rendement par rapport à la fréquence les courbes de réponse B et D correspondant à la réponse amplitude/fréquence pour des transducteurs corrigés suivant les techniques connues (courbe B) , et selon le procédé d'égalisation suivant l'invention (courbe D) . Cette comparaison des courbes met en évidence le gain de rendement "g" considérable que permet d'obtenir le procédé d'égalisation suivant l'invention. Cette caractéristique essentielle de 1'invention est obtenue car chaque haut-parleur des transducteurs jumelés peut fonctionner dans des conditions de rendement optimal, sans qu'il soit nécessaire de faire appel à des techniques d'amortissement des transducteurs.It is important to note that FIG. 4 constitutes an illustration for demonstrative purpose of the basic principle applied in the equalization method according to the invention. In fact, it should be noted that it has been found experimentally that a completely satisfactory equalization is obtained even if the succession of positive and negative alternations of the amplitude / frequency response curves of the transducers is not carried out according to regular periods, or if variations in amplitude of these alternations are relatively uneven. This means that, even if the method according to the invention does not provide an effect of perfect achievement from the arithmetic point of view, it is completely satisfactory from the psycho-auditory point of view. Another essential advantage of the invention is shown in FIG. 5, where the response curves B and D corresponding to the amplitude / frequency response for transducers corrected according to known techniques are plotted on a performance diagram with respect to frequency. curve B), and according to the equalization method according to the invention (curve D). This comparison of the curves highlights the considerable gain in yield "g" which the equalization process according to the invention makes it possible to obtain. This essential characteristic of the invention is obtained since each loudspeaker of the paired transducers can operate under conditions of optimum efficiency, without the need to use damping techniques for the transducers.
De façon surprenante, on s'est également aperçu que la mise en oeuvre du procédé d'égalisation suivant 1'invention fournit un procédé extrêmement précis d'ajustement de la tonalité, ou encore du timbre, des signaux sonores restitués. Cette caractéristique extrêmement avantageuse de l'invention s'ajoute à l'effet d'égalisation.Surprisingly, it has also been found that the implementation of the equalization method according to the invention provides an extremely precise method of adjusting the tone, or even the timbre, audio signals reproduced. This extremely advantageous characteristic of the invention adds to the equalization effect.
L'origine de ce phénomène est probablement à trouver dans les effets de génération d'harmonique produits par la superposition des sons provenant de chacun des transducteurs jumelés. Or, une égalisation satisfaisante, suivant le procédé de l'invention, ne peut être obtenue que si on munit les transducteurs, ou à tout le moins l'un d'entre eux, d'un moyen d'ajustement fin deThe origin of this phenomenon is probably to be found in the harmonic generation effects produced by the superposition of the sounds coming from each of the paired transducers. However, a satisfactory equalization, according to the method of the invention, can only be obtained if the transducers, or at least one of them, are provided with a means of fine adjustment of
10 sa courbe de réponse, essentiellement par ajustement de sa fréquence de résonance. L'objectif est en effet de pouvoir imprimer au(x) transducteur(s) ajustable(s) un décalage de la courbe de réponse permettant une compensation des alternances. En procédant à de tels10 its response curve, essentially by adjusting its resonant frequency. The objective is in fact to be able to print on the adjustable transducer (s) an offset of the response curve allowing compensation of the half-waves. By carrying out such
15 ajustements sur des prototypes, on a constaté qu'une égalisation acceptable est obtenue sur une certaine plage de réglages, ce qui donne une latitude d'ajustement. Cette latitude d'ajustement peut alors être mise à profit pour régler la tonalité ou le timbre du signal restitué, qui varie sur ces plages.15 adjustments on prototypes, it was found that an acceptable equalization is obtained over a certain range of settings, which gives a latitude of adjustment. This latitude of adjustment can then be used to adjust the tone or timbre of the restored signal, which varies over these ranges.
2020
Les applications pratiques de ce phénomène sont extrêmement intéressantes. En effet, on sait que les techniques d'enregistrement des sons (bande magnétique, disque à microsillon, disque laser, ...) comportent chacune des défauts, et introduisent des modifications, notamment des modifications de tonalité ou de timbre du signal original. L'invention procure donc un moyen de compensation de ces altérations du signal enregistré par rapport au signal original. De plus, ce moyen deThe practical applications of this phenomenon are extremely interesting. In fact, it is known that the techniques for recording sounds (magnetic tape, microgroove disc, laser disc, etc.) each have faults, and introduce modifications, in particular modifications of tone or timbre of the original signal. The invention therefore provides a means of compensating for these alterations of the recorded signal with respect to the original signal. In addition, this means of
30 compensation se présente sous la forme d'un système de réglage des transducteurs, qui permet d'adapter un même jeu de transducteurs à la restitution compensée de signaux enregistrés suivant des techniques différentes.30 compensation is in the form of a transducer adjustment system, which makes it possible to adapt the same set of transducers to the compensated reproduction of signals recorded using different techniques.
Bien entendu, de nombreuses autres applications de ce phénomène sont envisageables, et apparaîtront auxOf course, many other applications of this phenomenon are possible, and will appear in the
-. yeux des spécialistes. On peut citer à titre d'exemple la génération d'effets sonores sur les sons produits par des instruments électroniques, ou encore l'adaptation des transducteurs à l'acoustique de la salle d'écoute.-. eyes of specialists. Examples include the generation of sound effects on sounds produced by electronic instruments, or the adaptation of transducers to the acoustics of the listening room.
On a également constaté que le phénomène de modification de la tonalité du signal restitué joue sur l'ensemble du spectre des fréquences audibles, mais s'exerce de façon tout à fait remarquable pour les fréquences supérieures à 300 Hz, c'est-à-dire dans le domaine des médium et des aigus.It was also noted that the phenomenon of modification of the tone of the restored signal plays on the whole spectrum of the audible frequencies, but is exerted in a quite remarkable way for the frequencies higher than 300 Hz, that is to say say in the field of mid and treble.
Lors des essais sur prototypes, on a constaté que les effets sonores obtenus, par exemple sur un enregistrement de voix, permettaient d'obtenir à volonté, à côté de la tonalité normale et fidèle, une tonalité nasale, ou encore caverneuse. Les figures 1 et 2 représentent des modes de réalisation préférentiels, bien entendu non limitatifs, de jeux de transducteurs électro- acoustiques mettant en oeuvre le procédé d'égalisation suivant l'invention.During tests on prototypes, it was found that the sound effects obtained, for example on a voice recording, made it possible to obtain at will, alongside the normal and faithful tone, a nasal, or even cavernous tone. Figures 1 and 2 show preferred embodiments, of course not limiting, of sets of electro-acoustic transducers implementing the equalization method according to the invention.
Il s'agit dans les deux cas de transducteurs du type des cavités de Helmholtz munies chacune d'un haut- parleur et d'un évent. Mais on comprendra aisément que le procédé selon l'invention s'applique à tout type de transducteur, pourvu que la courbe de réponse amplitude/fréquence qui lui correspond vérifie au moins partiellement les deux conditions mises en évidence plus haut.In both cases, these are transducers of the Helmholtz cavity type, each provided with a loudspeaker and a vent. However, it will be readily understood that the method according to the invention applies to any type of transducer, provided that the amplitude / frequency response curve which corresponds to it at least partially satisfies the two conditions highlighted above.
Comme on peut le voir en figure 1, la mise en oeuvre du procédé d'égalisation est obtenue en utilisant deux cavités de Helmholtz 10 et 20, munies chacune d'un haut-parleur 11-21, et d'un évent 12-22. Les cavités 10- 20 sont jumelées de façon à présenter une paroi latérale commune 15.As can be seen in Figure 1, the implementation of the equalization process is obtained by using two Helmholtz cavities 10 and 20, each provided with a loudspeaker 11-21, and a vent 12-22 . The cavities 10-20 are paired so as to present a common side wall 15.
Les deux cavités sont de caractéristiques identiques, ou quasi-identiques. Ceci signifie qu'elles présentent chacune une courbe de réponse amplitude/fréquence de configuration sensiblement identique, notamment du point de vue de la fréquence de succession des irrégularités, et de l'amplitude des alternances.The two cavities have identical, or almost identical, characteristics. This means that they each have a response curve amplitude / frequency of substantially identical configuration, in particular from the point of view of the frequency of succession of the irregularities, and of the amplitude of the half-waves.
L'ajustement du décalage des courbes de réponse permettant l'égalisation suivant l'invention est réalisé ici par ajustement de la fréquence de résonance des transducteurs. Plus précisément, un ajustement grossier est réalisé par déplacement de la paroi 15, et un ajustement fin par déplacement du bloc inférieur 16. Ces déplacements sont par exemple réalises' par l'intermédiaire de systèmes tige filetée-noix 17, 18 ; 37, 38 commandés par volants 19, 39 montés sur une paroi extérieure des cavités jumelées.The adjustment of the offset of the response curves allowing the equalization according to the invention is carried out here by adjusting the resonant frequency of the transducers. More specifically, a coarse adjustment is performed by movement of the wall 15, and a fine adjustment by movement of the lower block 16. These movements are made for example 'through systems threaded-rod nuts 17, 18; 37, 38 controlled by flywheels 19, 39 mounted on an outer wall of the twin cavities.
Bien entendu, tout autre système permettant un réglage fin du déplacement de la "portion 16 articulée de la paroi commune 15 des cavités 10-20 convient tout aussi bien pour la mise en oeuvre de l'invention.Of course, any other system allowing fine adjustment of the movement of the " articulated portion 16 of the common wall 15 of the cavities 10-20 is just as suitable for the implementation of the invention.
Comme on l'a compris, dans le mode de réalisation de la figure 1, la modification de la fréquence de résonance de chacun des deux transducteurs jumelés est réalisée par modification de la configuration et du volume intérieur des deux cavités 10-20 respectivement, du fait du déplacement de la portion de paroi 16. L'effet obtenu peut être illustré à partir de la figure 4. On peut en effet considérer que la courbe A correspond à la courbe de réponse amplitude/fréquence du transducteur 1, et que la courbe C correspond à la courbe de réponse amplitude/fréquence du second transducteur 2. La fréquence de résonance f2 du transducteur 2 se situe aux environs de 40 Hz. De façon connue, la fréquence de résonance correspond à un point de la pente d'affaiblissement caractéristique de tout système résonnant acoustique (pente de l'ordre de 18 dB par octave) , sur la courbe de réponse amplitude/fréquence. Si l'on considère fictivement que la courbe de réponse A du transducteur 1 reste fixe, l'effet du déplacement de la portion articulée 16 de la paroi commune 15 sur le décalage de la courbe C sera illustré approximativement par la courbe df. Cette courbe df est en effet parcourue par le point P de la fréquence de résonance du transducteur 2, sur la courbe de réponse C, lorsqu'on fait varier le volume intérieur de la cavité 20 du transducteur 2. Cette courbe df illustre 1•influence de la variation du volume de la cavité 20 sur deux paramètres essentiels :As has been understood, in the embodiment of FIG. 1, the modification of the resonant frequency of each of the two paired transducers is carried out by modification of the configuration and of the internal volume of the two cavities 10-20 respectively, from the made of the displacement of the wall portion 16. The effect obtained can be illustrated from FIG. 4. It can in fact be considered that the curve A corresponds to the amplitude / frequency response curve of the transducer 1, and that the curve C corresponds to the amplitude / frequency response curve of the second transducer 2. The resonance frequency f 2 of the transducer 2 is around 40 Hz. In known manner, the resonance frequency corresponds to a point on the weakening slope characteristic of any acoustic resonant system (slope of the order of 18 dB per octave), on the amplitude / frequency response curve. If one fictitiously considers that the response curve A of the transducer 1 remains fixed, the effect of the displacement of the articulated portion 16 of the common wall 15 on the offset of the curve C will be illustrated approximately by the curve d f . This curve d f is in fact traversed by the point P of the resonant frequency of the transducer 2, on the response curve C, when the internal volume of the cavity 20 of the transducer 2 is varied. This curve d f illustrates 1 • influence of the variation in the volume of the cavity 20 on two essential parameters:
- d'une part, le décalage de l'origine de la courbe de réponse C vers la gauche, lorsque le volume de la cavité 20 augmente. En d'autres termes, l'augmentation du volume de la cavité 20 diminue la fréquence de résonance du transducteur, et par conséquent étend le spectre sonore restituable par le transducteur dans les fréquences ;- On the one hand, the offset of the origin of the response curve C to the left, when the volume of the cavity 20 increases. In other words, increasing the volume of the cavity 20 decreases the resonant frequency of the transducer, and consequently expands the sound spectrum reproducible by the transducer in the frequencies;
- d'autre part, l'augmentation du volume de la cavité résonnante 20 entraîne une remontée du point de résonance P vers le premier maximum de la courbe de réponse C.- on the other hand, the increase in the volume of the resonant cavity 20 causes the resonance point P to rise towards the first maximum of the response curve C.
L'effet combiné de ces deux phénomènes, et la prépondérance relative du second conduit à un déplacement du point P vers la gauche de la courbe df, qui croît en tendant plus ou moins asymptotiquement vers la valeur maximale du rendement de la première alternance de la courbe C.The combined effect of these two phenomena, and the relative preponderance of the second leads to a displacement of the point P to the left of the curve d f , which increases by tending more or less asymptotically towards the maximum value of the efficiency of the first alternation of curve C.
Le décalage de la courbe C par rapport à la courbe A peut alors être dosé de façon très précise, pour que le déplacement du point P sur la courbe d^ corresponde à une valeur d'une demi-période des irrégularités alternées de la courbe de réponse.The offset of curve C with respect to curve A can then be very precisely measured, so that the displacement of point P on curve d corresponds to a value of half a period of the alternating irregularities of the curve reply.
Bien entendu, l'ajustement des volumes respectifs des cavités 10-20 des transducteurs jumelés représentés sur la figure 1, par déplacement de la portion de paroi 16 articulée, agit sur les courbes de réponse des transducteurs, puisque le volume de l'une des cavités 10 ; 20 augmente, lorsque le volume de l'autre cavité 20 ; 10 décroît. Le décalage des deux courbes de réponse A et C résulte donc du déplacement de chacune d'elles en sens opposés par rapport à l'échelle des fréquences.Of course, the adjustment of the respective volumes of the cavities 10-20 of the twin transducers shown in FIG. 1, by displacement of the hinged wall portion 16 acts on the response curves of the transducers, since the volume of one of the cavities 10; 20 increases when the volume of the other cavity 20; 10 decreases. The offset of the two response curves A and C therefore results from the displacement of each of them in opposite directions with respect to the frequency scale.
L'installation de la figure 1 permet un réglage de l'égalisation par variation du volume de l'enceinte, grâce au déplacement d'une portion de la paroi communeThe installation of FIG. 1 allows adjustment of the equalization by varying the volume of the enclosure, thanks to the displacement of a portion of the common wall.
1 0 16. Bien entendu, les dimensions de la portion de paroi 16 articulée ne sont pas une caractéristique limitative de l'invention, et doivent être adaptées aux caractéristiques du transducteur, et à la précision de réglage recherchée. Il est notamment possible de prévoir1 0 16. Of course, the dimensions of the articulated wall portion 16 are not a limiting characteristic of the invention, and must be adapted to the characteristics of the transducer, and to the desired adjustment precision. In particular, it is possible to plan
1 5 un système dans lequel l'ensemble de la paroi commune 15 est articulé.1 5 a system in which the entire common wall 15 is articulated.
Les spécialistes envisageront aisément que l'ajustement de la fréquence de résonance des transducteurs peut s'effectuer par action sur de nombreux autres paramètres des transducteurs, que celui du volumeSpecialists will readily imagine that the adjustment of the resonant frequency of the transducers can be effected by action on many other parameters of the transducers, than that of the volume.
20 des cavités résonnantes.20 resonant cavities.
Parmi les paramètres ajustables, on peut mentionner la modification de l'écoulement de l'air à travers les évents 12, 22 des cavités de Helmholtz. Cette modification de l'écoulement de l'air s'effectue parAmong the adjustable parameters, one can mention the modification of the air flow through the vents 12, 22 of the Helmholtz cavities. This modification of the air flow is effected by
ΔD exemple par action sur un volet (non représenté) obturant plus ou moins complètement l'évent, ou encore par adjonction, d'un col de longueur ou de forme ajustable. Une autre technique d'ajustement de la fréquence de résonance d'au moins un des transducteurs consiste àΔD example by action on a shutter (not shown) closing the vent more or less completely, or even by adding a neck of adjustable length or shape. Another technique for adjusting the resonance frequency of at least one of the transducers consists in
30 prévoir un diaphragme suspendu élastiguement et obturant hermétiquement l'évent (du type d'un haut-parleur passif) . L'ajustement consiste alors à contrôler la fréquence de résonance du diaphragme, en agissant sur sa masse, sur la force élastique de rappel du diaphragme, ou par tout autre moyen.30 provide a diaphragm suspended elastically and hermetically sealing the vent (of the type of a passive speaker). The adjustment then consists in controlling the resonant frequency of the diaphragm, by acting on its mass, on the elastic return force of the diaphragm, or by any other means.
L'action sur l'écoulement de l'air à travers l'évent peut être considérée, dans certaines applications, comme moins avantageuse que l'action sur le volume des cavités : une variation du volume de la cavité résonnante n'a en effet en général pas d'influence sur le rendement du transducteur, à la différence des techniques d'action sur 1*évent.The action on the flow of air through the vent can be considered, in certain applications, as less advantageous than the action on the volume of the cavities: a variation in the volume of the resonant cavity has indeed in general no influence on the transducer efficiency, unlike the action techniques on the vent.
Bien entendu, lorsque l'on souhaite ajuster l'égalisation d'un jeu de transducteurs selon l'invention, par modification du volume intérieur de la cavité résonnante de l'un d'entre eux, les deux transducteurs d'un même jeu peuvent parfaitement être tout à fait distincts l'un de l'autre, et ne pas présenter donc de paroi commune.Of course, when it is desired to adjust the equalization of a set of transducers according to the invention, by modifying the interior volume of the resonant cavity of one of them, the two transducers of the same set can perfectly be completely separate from each other, and therefore not have a common wall.
La figure 2 représente une variante du mode de réalisation de . la figure 1, dans laquelle deux transducteurs 3, 4, du type à cavités de Helmholtz, sont jumelés en présentant une paroi de fond 35 commune mobile. Chacun des transducteurs est muni d'un haut- parleur 31-41, et d'un évent 32-42.FIG. 2 represents a variant of the embodiment of. FIG. 1, in which two transducers 3, 4, of the Helmholtz cavity type, are paired by presenting a movable common bottom wall. Each of the transducers is provided with a speaker 31-41, and a vent 32-42.
De façon avantageuse, la cloison intérieure mobile commune 35 est inclinée, de façon à éviter les effets défavorables de réflexion qui seraient induits par une cloison droite, et impliqueraient l'utilisation d'une technique d'amortissement dommageable au rendement.Advantageously, the common movable internal partition 35 is inclined, so as to avoid the unfavorable effects of reflection which would be induced by a straight partition, and would imply the use of a damping technique detrimental to performance.
Un prototype correspondant à cette figure a été réalisé, au moyen d'un caisson, dont le volume intérieur total (couvrant les cavités des transducteurs 3 et 4) était de 80 litres. Les deux haut-parleurs sont semblables, et présentaient un diamètre hors-tout de 190 mm. La surface nominale de chacun des évents, de 2,5 dm2, est ajustée par un volet.A prototype corresponding to this figure was produced by means of a box, the total interior volume of which (covering the cavities of the transducers 3 and 4) was 80 liters. The two speakers are similar, and had an overall diameter of 190 mm. The nominal surface of each of the vents, 2.5 dm 2 , is adjusted by a flap.
Cette configuration de mise en oeuvre du procédé de l'invention présente l'avantage de combiner le phénomène d'égalisation déjà décrit, avec un second phénomène de contrôle de la directivité du rayonnement acoustique du système.This implementation configuration of the method of the invention has the advantage of combining the equalization phenomenon already described, with a second phenomenon of controlling the directivity of the acoustic radiation of the system.
Ce contrôle de directivité est obtenu en alimentant les deux transducteurs 3, 4 à partir de la même source de modulation, mais en les actionnant simultanément en décalage de phase, préférentiellement en opposition de phase.This directivity control is obtained by supplying the two transducers 3, 4 from the same modulation source, but by actuating them simultaneously in phase shift, preferably in phase opposition.
Le contrôle de la directivité peut alors être obtenu en agissant sur l'un ou l'autre des paramètres tels que : la valeur du déphasage (constante ou non en fonction de la fréquence) ; l'orientation de l'émission de chaque transducteur ; l'intensité et le lobe de leur rayonnement ; les distances entre émetteurs ; l'étendue de fréquences concernées ; entre autres. On conçoit donc que le mode de la réalisation de la figure 2 est extrêmement avantageux lorsque l'on souhaite avoir une possibilité de réglage de l'égalisation du signal sonore restitué, combinée à un effet de directivité, et éventuellement à une possibilité d'action sur la tonalité, tout ceci étant possible sans nuire au rendement de l'installation. Une application tout à fait préférentielle de ce système de transducteur électro-acoustique est la sonorisation à grande puissance des salles de congrès, de concert, ou plus généralement de toute manifestation publique. Control of the directivity can then be obtained by acting on one or other of the parameters such as: the value of the phase shift (constant or not as a function of the frequency); the orientation of the emission of each transducer; the intensity and the lobe of their radiation; the distances between transmitters; the range of frequencies concerned; among others. It can therefore be seen that the embodiment of FIG. 2 is extremely advantageous when it is desired to have a possibility of adjusting the equalization of the restored sound signal, combined with a directivity effect, and possibly with a possibility of action. on the tone, all this being possible without affecting the performance of the installation. A completely preferential application of this electro-acoustic transducer system is the high power sound system of congress halls, concert halls, or more generally of any public event.

Claims

REVENDICATIONS
1) Procédé de correction de la réponse amplitude/fréquence d'un transducteur électro-acoustique, notamment du type formé d'un haut-parleur (11) monté dans une enceinte résonnante (10) et destiné à être branché en sortie d'une source électrique de modulation pour restituer le signal sonore associé, caractérisé en ce qu'on choisit un transducteur1) Method for correcting the amplitude / frequency response of an electro-acoustic transducer, in particular of the type formed by a loudspeaker (11) mounted in a resonant enclosure (10) and intended to be connected at the output of a electric modulation source to reproduce the associated sound signal, characterized in that a transducer is chosen
(1) dont les irrégularités de la courbe de réponse(1) including irregularities in the response curve
10 amplitude/fréquence A se présentent sensiblement sous la forme d'une succession d'alternances de niveaux axima et minima sur la gamme de fréquence restituée, en ce qu'on utilise ledit transducteur électro¬ acoustique (1) en coopération avec au moins un second10 amplitude / frequency A are substantially in the form of a succession of alternations of axima and minima levels over the restored frequency range, in that said electro¬ acoustic transducer (1) is used in cooperation with at least one second
15 transducteur électro-acoustique (2) branché en parallèle sur la même source de modulation, et fonctionnant sur la même gamme de fréquences, et en ce que ledit second transducteur est choisi de façon qu'il présente une courbe de réponse (C) amplitude/fréquence sensiblement complémentaire de celle 20 (A) dudit premier transducteur (1) , pour former par addition des signaux sonores desdits transducteurs, un signal sonore résultant corrigé, du fait de la compensation mutuelle des irrégularités inhérentes à chaque courbe A, C. •-515 electro-acoustic transducer (2) connected in parallel to the same modulation source, and operating on the same frequency range, and in that said second transducer is chosen so that it has an amplitude response curve (C) / frequency substantially complementary to that 20 (A) of said first transducer (1), to form by adding sound signals from said transducers, a resulting sound signal corrected, due to mutual compensation for the irregularities inherent in each curve A, C. • -5
2) Procédé selon la revendication 1, caractérisé en ce qu'on choisit le transducteur (2) de façon qu'il présente une courbe de réponse C amplitude/fréquence sensiblement identique à celle A du premier transducteur, et en ce qu'on agit sur la 0 fréquence de résonance d'au moins l'un des deux transducteurs de façon à provoquer un décalage relatif de leurs courbes de réponse A, C assurant l'effet de correction par compensation mutuelle des irrégularités des courbes A, C. 5 3) Procédé selon la revendication 2, caractérisé en ce que l'ajustement de la fréquence de résonance d'au moins l'un des transducteurs électro¬ acoustiques (1, 2) est réalisé par action sur au moins l'un des paramètres suivants : modification de la configuration et/ou du volume du transducteur ; modification de l'écoulement de l'air à travers au moins un évent (12) réalisé dans l'enceinte résonnante (10) du transducteur r modification des caractéristiques d'un diaphragme passif monté dans 1'enceinte. 4) Procédé suivant l'une quelconque des revendications 1 à 3, caractérisé en ce que les courbes de réponse amplitude/fréquence (A, C) des transducteurs (1, 2) sont ajustées l'une par rapport à l'autre de façon à obtenir un effet d'égalisation du signal sonore résultant.2) Method according to claim 1, characterized in that the transducer (2) is chosen so that it has a response curve C amplitude / frequency substantially identical to that A of the first transducer, and in that one acts on the 0 resonant frequency of at least one of the two transducers so as to cause a relative offset of their response curves A, C ensuring the effect of correction by mutual compensation of the irregularities of the curves A, C. 5 3) Method according to claim 2, characterized in that the adjustment of the resonance frequency of at least one of the electro¬ acoustic transducers (1, 2) is carried out by action on at least one of the following parameters : modification of the configuration and / or volume of the transducer; modification of the air flow through at least one vent (12) produced in the resonant enclosure (10) of the transducer r modification of the characteristics of a passive diaphragm mounted in the enclosure. 4) Method according to any one of claims 1 to 3, characterized in that the amplitude / frequency response curves (A, C) of the transducers (1, 2) are adjusted relative to each other so to obtain an equalizing effect of the resulting sound signal.
5) Procédé suivant l'une quelconque 'des revendications 1 à 4, caractérisé en ce que l'ajustement relatif des courbes de réponse amplitude/fréquence (A, C) des transducteurs (1, 2) est réalisé de façon à obtenir un effet de modification de la tonalité du signal sonore résultant.5) A method according to any one 'of claims 1 to 4, characterized in that the relative adjustment of the response curves amplitude / frequency (A, C) of the transducers (1, 2) is designed so as to obtain an effect modification of the tone of the resulting sound signal.
6) Ensemble de transducteurs (1, 2) permettant la mise en oeuvre du procédé de correction suivant l'une quelconque des revendications 1 à 5.6) set of transducers (1, 2) allowing the implementation of the correction method according to any one of claims 1 to 5.
7) Ensemble de transducteurs suivant la revendication 6, caractérisé en ce que lesdits transducteurs (1, 2) sont du type d'une cavité résonnante de Helmholtz (10, 20) munies d'un haut-parleur (11, 21) respectivement, lesdites cavités résonnantes (20) présentant une paroi (15) commune.7) set of transducers according to claim 6, characterized in that said transducers (1, 2) are of the type of a resonant Helmholtz cavity (10, 20) provided with a loudspeaker (11, 21) respectively, said resonant cavities (20) having a common wall (15).
8) Ensemble de transducteurs suivant la revendication 7, caractérisé en ce qu'au moins une portion de ladite paroi commune (15) est mobile, de façon à permettre un ajustement du volume intérieur desdites cavités (10, 20) . 9) Ensemble de transducteurs suivant l'une quelconque des revendications 6 à 8, caractérisé en ce que lesdits transducteurs (3, 4) sont montés en opposition l'un par rapport à l'autre, et en ce que ladite paroi commune (25, 35) constitue la paroi de fond de chacun desdits transducteurs (3, 4) .8) set of transducers according to claim 7, characterized in that at least a portion of said common wall (15) is movable, so as to allow an adjustment of the interior volume of said cavities (10, 20). 9) set of transducers according to any one of claims 6 to 8, characterized in that said transducers (3, 4) are mounted in opposition relative to each other, and in that said common wall (25 , 35) constitutes the bottom wall of each of said transducers (3, 4).
10) Ensemble de transducteurs suivant la revendication 9, caractérisé en ce que lesdits transducteurs (3, 4) sont alimentés en opposition de phase à partir d'une même source de modulation. 11) Procédé de correction de la courbe de réponse amplitude/fréquence d'un transducteur (3) , selon le procédé de l'une quelconque des revendications 1 à 5, caractérisé en ce qu'on agit sur la directivité de l'émission sonore des transducteurs (3, 4) par action sur 1'un des paramètres suivants : déphasage du rayonnement des transducteurs (3, 4) ; orientation de leur émission sonore ; intensité et lobe de leur rayonnement ; distance entre les transducteurs. 10) set of transducers according to claim 9, characterized in that said transducers (3, 4) are supplied in phase opposition from the same modulation source. 11) Method for correcting the amplitude / frequency response curve of a transducer (3), according to the method of any one of claims 1 to 5, characterized in that one acts on the directivity of the sound emission transducers (3, 4) by acting on one of the following parameters: phase shift of the radiation from the transducers (3, 4); orientation of their sound emission; intensity and lobe of their radiation; distance between transducers.
EP88900235A 1986-12-12 1987-12-11 Method for correcting the amplitude/frequency response of an electro-acoustic transducing system and corresponding transducer assembly Expired - Lifetime EP0335892B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT88900235T ATE91838T1 (en) 1986-12-12 1987-12-11 METHOD OF CORRECTING THE AMPLITUDE FREQUENCY CHARACTERISTICS OF AN ELECTROACOUSTIC TRANSDUCER ARRANGEMENT AND RELATIVE TRANSDUCER DEVICE.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8617423 1986-12-12
FR8617423A FR2608343B1 (en) 1986-12-12 1986-12-12 METHOD FOR EQUALIZING THE AMPLITUDE / FREQUENCY RESPONSE OF AN ELECTROACOUSTIC TRANSDUCER ASSEMBLY, CORRESPONDING TRANSDUCER ASSEMBLY

Publications (2)

Publication Number Publication Date
EP0335892A1 true EP0335892A1 (en) 1989-10-11
EP0335892B1 EP0335892B1 (en) 1993-07-21

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP88900235A Expired - Lifetime EP0335892B1 (en) 1986-12-12 1987-12-11 Method for correcting the amplitude/frequency response of an electro-acoustic transducing system and corresponding transducer assembly

Country Status (7)

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EP (1) EP0335892B1 (en)
KR (1) KR890700298A (en)
AT (1) ATE91838T1 (en)
AU (1) AU1051588A (en)
DE (1) DE3786672D1 (en)
FR (1) FR2608343B1 (en)
WO (1) WO1988004513A1 (en)

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US6272446B1 (en) 1995-12-22 2001-08-07 Bruel & Kjaer Sound & Vibration Measurement A/S System and a method for measuring a continuous signal

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US6272446B1 (en) 1995-12-22 2001-08-07 Bruel & Kjaer Sound & Vibration Measurement A/S System and a method for measuring a continuous signal

Also Published As

Publication number Publication date
AU1051588A (en) 1988-06-30
ATE91838T1 (en) 1993-08-15
EP0335892B1 (en) 1993-07-21
FR2608343A1 (en) 1988-06-17
DE3786672D1 (en) 1993-08-26
WO1988004513A1 (en) 1988-06-16
FR2608343B1 (en) 1989-06-16
KR890700298A (en) 1989-03-11

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