EP3637792A1 - Device for controlling a speaker and associated sound playback system - Google Patents

Abstract

The present invention relates to a device (22) for controlling a loudspeaker in an enclosure, the device (22) comprising: - a unit (36) for duplicating a desired dynamic signal (S <sub> dyn </ sub>) to obtain two identical dynamic signals (S _dyn1, S _dyn2) - a first processing unit (38) configured to process the first desired dynamic signal ( S _dyn1) to obtain a first processed signal (S _dyn1 ') whose frequencies are less than or equal to a predetermined frequency, - a second configured processing unit (40) to process the second desired dynamic signal (S _dyn2) to obtain a second processed signal (S _dyn2 ') whose frequencies are strictly greater than the predetermined frequency, and- a combination unit (42) of the first and second processed signals (S _dyn1 ', S _dyn2') to obtain a control signal (S _command) of the speaker.

Description

The present invention relates to a device for controlling a loudspeaker in an enclosure. The present invention also relates to a sound reproduction installation comprising such a control device.

Speakers are electromagnetic devices that convert an electrical signal into an acoustic signal.

The loudspeakers introduce a non-linear distortion which can considerably affect the acoustic signal obtained. The distortion comes from various factors, including the non-linearity of the magnetic circuit of the loudspeaker and certain mechanical elements of the loudspeaker.

In addition, the current flowing in a loudspeaker can bring the temperature of the conductors of the loudspeaker to a value liable to deteriorate them. In addition, even without leading to the deterioration of the conductors, the increase in the temperature of the conductors causes an increase in their ohmic resistance. This results in a phenomenon, called "thermal compression", which consists of a decrease in the efficiency of the loudspeaker with the increase in resistance.

Finally, excessive movement of the loudspeaker diaphragm following an improper supply can damage the loudspeaker diaphragm.

Solutions have been proposed for controlling the loudspeakers in order to eliminate distortions in the behavior of the loudspeaker by appropriate control.

However, such solutions can still be improved.

There is therefore a need for a device for controlling a loudspeaker in an enclosure making it possible to reduce the distortion in the signal reproduced by the loudspeaker while improving the protection of the diaphragm of the loudspeaker.

• une entrée pour un signal audio à reproduire,
• une sortie de fourniture d'un signal de commande du haut-parleur,
• une unité de détermination d'un signal dynamique désiré, représentatif d'une grandeur dynamique désirée de la membrane du haut-parleur, en fonction du signal audio à reproduire et de la structure de l'enceinte,
• une unité de duplication du signal dynamique désiré pour obtenir deux signaux dynamiques désirés identiques,
• une première unité de traitement configurée pour traiter le premier signal dynamique désiré pour obtenir un premier signal traité dont les fréquences sont inférieures ou égales à une fréquence prédéterminée,
• une deuxième unité de traitement configurée pour traiter le deuxième signal dynamique désiré pour obtenir un deuxième signal traité dont les fréquences sont strictement supérieures à la fréquence prédéterminée, et
• une unité de combinaison du premier et du deuxième signal traité pour obtenir le signal de commande du haut-parleur.

To this end, the subject of the invention is a device for controlling a loudspeaker in an enclosure, the loudspeaker comprising a membrane, the enclosure having a structure, the device comprising:

• an input for an audio signal to be reproduced,
• an output for supplying a loudspeaker control signal,
• a unit for determining a desired dynamic signal, representative of a desired dynamic magnitude of the speaker membrane, as a function of the audio signal to be reproduced and of the structure of the enclosure,
• a unit for duplicating the desired dynamic signal to obtain two identical desired dynamic signals,
• a first processing unit configured to process the first desired dynamic signal to obtain a first processed signal whose frequencies are less than or equal to a predetermined frequency,
• a second processing unit configured to process the second desired dynamic signal to obtain a second processed signal whose frequencies are strictly greater than the predetermined frequency, and
• a unit for combining the first and second signal processed to obtain the loudspeaker control signal.

• la première unité de traitement comprend un limiteur d'excursion configuré pour :
  • déterminer un signal d'excursion, représentatif de l'excursion de la membrane du haut-parleur, en fonction du premier signal dynamique désiré,
  • déterminer l'excursion maximale du signal d'excursion, et
  • lorsque l'excursion maximale déterminée est strictement supérieure à une excursion maximale acceptable, appliquer un premier gain d'atténuation au signal d'excursion pour obtenir un signal d'excursion atténué,
  le premier signal traité étant obtenu en fonction du signal d'excursion atténué.
• le haut-parleur comprend au moins une bobine, la première unité de traitement comprenant :
  • un module de filtrage des fréquences du signal d'excursion atténué strictement supérieures à la fréquence prédéterminée pour obtenir un signal d'excursion filtré,
  • un module de détermination d'un premier signal en intensité, représentatif de l'intensité du courant destiné à circuler dans la bobine du haut-parleur, en fonction du signal d'excursion filtré et d'une modélisation électromécanique du haut-parleur, et
  • un limiteur en courant configuré pour fixer à une valeur d'intensité prédéterminée, toutes les valeurs du premier signal en intensité strictement supérieures à la valeur d'intensité prédéterminée et obtenir ainsi un premier signal en intensité atténué,
  le premier signal traité étant obtenu en fonction du premier signal en intensité atténué.
• la première unité de traitement comprend :
  • un module de détermination d'un premier signal en tension, représentatif de la tension aux bornes du haut-parleur, en fonction du signal d'excursion filtré, de la modélisation électromécanique du haut-parleur et du premier signal en intensité atténué, et
  • un limiteur en tension configuré pour fixer à une valeur de tension prédéterminée, toutes les valeurs du premier signal en tension strictement supérieures à la valeur de tension prédéterminée et obtenir ainsi un premier signal en tension atténué,
  le premier signal traité étant obtenu en fonction du premier signal en tension atténué.
• la première unité de traitement comprend un module de filtrage additionnel configuré pour filtrer les fréquences du premier signal en tension atténué strictement supérieures à la fréquence prédéterminée, le premier signal traité étant obtenu en fonction du premier signal en tension atténué filtré par le module de filtrage additionnel.
• la deuxième unité de traitement comprend :
  • un module de filtrage des fréquences du deuxième signal dynamique désiré inférieures ou égales à la fréquence prédéterminée pour obtenir un deuxième signal filtré,
  • un module de détermination d'un deuxième signal en tension, représentatif de la tension aux bornes du haut-parleur, en fonction du deuxième signal filtré et d'une modélisation électromécanique du haut-parleur,
  le deuxième signal traité étant obtenu en fonction du deuxième signal en tension.
• la deuxième unité de traitement comprend un limiteur en tension configuré pour :
  • déterminer la tension maximale du deuxième signal en tension,
  • lorsque la tension maximale déterminée est strictement supérieure à une tension maximale acceptable, appliquer un deuxième gain d'atténuation au deuxième signal en tension pour obtenir un deuxième signal en tension atténué,
  le deuxième signal traité étant obtenu en fonction du deuxième signal en tension atténué.
• la deuxième unité de traitement comprend un module de filtrage additionnel configuré pour filtrer les fréquences du deuxième signal en tension atténué inférieures ou égales à la fréquence prédéterminée, le deuxième signal traité étant obtenu en fonction du deuxième signal en tension atténué filtré par le module de filtrage additionnel.
• la fréquence prédéterminée est comprise dans un intervalle de fréquences centré sur la fréquence de résonance du haut-parleur et s'étendant sur au plus 200 Hz.

According to particular embodiments, the control device comprises one or more of the following characteristics, taken in isolation or in any technically possible combination:

• the first processing unit comprises an excursion limiter configured for:
  • determining an excursion signal, representative of the excursion of the loudspeaker membrane, as a function of the first desired dynamic signal,
  • determine the maximum excursion of the excursion signal, and
  • when the determined maximum excursion is strictly greater than a maximum acceptable excursion, applying a first attenuation gain to the excursion signal to obtain an attenuated excursion signal,
  the first processed signal being obtained as a function of the attenuated excursion signal.
• the loudspeaker comprises at least one coil, the first processing unit comprising:
  • a module for filtering the frequencies of the attenuated excursion signal strictly greater than the predetermined frequency in order to obtain a filtered excursion signal,
  • a module for determining a first signal in intensity, representative of the intensity of the current intended to circulate in the coil of the loudspeaker, as a function of the filtered excursion signal and of an electromechanical modeling of the loudspeaker, and
  • a current limiter configured to fix all the values of the first intensity signal strictly greater than the predetermined intensity value at a predetermined intensity value and thus obtain a first attenuated intensity signal,
  the first processed signal being obtained as a function of the first attenuated intensity signal.
• the first processing unit includes:
  • a module for determining a first voltage signal, representative of the voltage across the loudspeaker, as a function of the filtered excursion signal, of the electromechanical modeling of the loudspeaker and of the first attenuated intensity signal, and
  • a voltage limiter configured to fix all the values of the first voltage signal strictly greater than the predetermined voltage value at a predetermined voltage value and thus obtain a first attenuated voltage signal,
  the first processed signal being obtained as a function of the first attenuated voltage signal.
• the first processing unit comprises an additional filtering module configured to filter the frequencies of the first attenuated voltage signal strictly greater than the predetermined frequency, the first processed signal being obtained as a function of the first attenuated voltage signal filtered by the additional filtering module .
• the second processing unit includes:
  • a module for filtering the frequencies of the second desired dynamic signal less than or equal to the predetermined frequency to obtain a second filtered signal,
  • a module for determining a second voltage signal, representative of the voltage across the loudspeaker, as a function of the second filtered signal and of an electromechanical modeling of the loudspeaker,
  the second processed signal being obtained as a function of the second voltage signal.
• the second processing unit comprises a voltage limiter configured for:
  • determine the maximum voltage of the second voltage signal,
  • when the maximum voltage determined is strictly greater than a maximum acceptable voltage, apply a second attenuation gain to the second voltage signal to obtain a second attenuated voltage signal,
  the second processed signal being obtained as a function of the second attenuated voltage signal.
• the second processing unit comprises an additional filtering module configured to filter the frequencies of the second attenuated voltage signal less than or equal to the predetermined frequency, the second processed signal being obtained as a function of the second attenuated voltage signal filtered by the filtering module additional.
• the predetermined frequency is included in a frequency interval centered on the resonant frequency of the loudspeaker and extending over at most 200 Hz.

The present invention also relates to a sound reproduction installation comprising a loudspeaker in an enclosure and a loudspeaker control device as described above.

• Figure 1, une vue schématique d'une installation de restitution sonore comprenant un haut-parleur dans une enceinte et un dispositif de commande du haut-parleur,
• Figure 2, une vue schématique du dispositif de commande de la figure 1,
• Figure 3, une vue schématique d'une première unité de traitement du dispositif de commande de la figure 2, et
• Figure 4, une vue schématique d'une deuxième unité de traitement du dispositif de commande de la figure 2.

The invention will be better understood on reading the description which follows, given by way of example only and with reference to the drawings which are:

• Figure 1 , a schematic view of a sound reproduction installation comprising a loudspeaker in an enclosure and a loudspeaker control device,
• Figure 2 , a schematic view of the device for controlling the figure 1 ,
• Figure 3 , a schematic view of a first processing unit of the device for controlling the figure 2 , and
• Figure 4 , a schematic view of a second processing unit of the device for controlling the figure 2 .

A sound reproduction installation 10 is illustrated by the figure 1 .

The installation 10 comprises, as known per se, a source 12 for producing an audio signal S _audio , such as a digital disc player connected to a loudspeaker 14 in an enclosure, through an amplifier in voltage 16. Between the audio source 12 and the amplifier 16 are arranged, successively in series, a desired model 20 corresponding to the desired model of behavior of the enclosure, and a control device 22. The desired model 20 is a linear model or a nonlinear model.

According to a particular embodiment, a loop 23 for measuring a physical quantity, such as the temperature of the magnetic circuit of the loudspeaker 14 or the current flowing in the coil of the loudspeaker 14, is provided between the loudspeaker speaker 14 and the control device 22.

The desired model 20 is independent of the loudspeaker 14 used in the installation and of the modeling of the loudspeaker 14.

The desired model 20 is, for example, a function of the ratio of the amplitude of the desired signal, denoted S _{audio_ref} , to the amplitude S _audio of the input signal from the source 12, expressed as a function of the frequency.

Advantageously, for frequencies lower than a frequency f _min , such a ratio is a function converging towards 0 when the frequency tends towards 0. This makes it possible to limit the reproduction of excessively low frequencies, and thus to avoid displacements of the membrane of the loudspeaker 14 outside the ranges recommended by the manufacturer.

It is the same for the high frequencies where the ratio tends towards 0 beyond a frequency f _max when the frequency of the signal tends towards infinity.

According to another embodiment, the desired model is not specified and the desired model is considered to be unitary.

The control device 22, an example of whose detailed structure is illustrated by the figure 2 , is placed at the input of amplifier 16.

The control device 22 is suitable for receiving the audio signal S _{audio_ref} to be reproduced as _input as defined at the output of the desired model 20 and for outputting a control signal S _controlling the loudspeaker 14, also called excitation signal . In a preferred embodiment, the loudspeaker 14 is voltage-controlled and the command signal S _command is a voltage.

As will be described in the following description, the control signal S _command is adapted to take account of the non-linearity of the loudspeaker 14 and to limit the excessive displacements of the diaphragm of the loudspeaker 14. In general , the controller 22 uses the Thiele and Small model of the speaker 14, in order to obtain a target frequency response (for example flat).

In the example illustrated by figure 2 , the control device 22 comprises an input 30 for the signal S _{audio_ref} to be reproduced and an output 32 for supplying the control signal S _control of the loudspeaker 14. The control device 22 also includes a unit 34 for determining the a desired dynamic signal S _dyn , a unit 36 for duplicating the desired dynamic signal S _dyn , a first processing unit 38, a second processing unit 40 and a combining unit 42.

The determination unit 34 is configured to determine, at each instant, the desired dynamic signal S _dyn , representative of a desired dynamic quantity A _ref of the diaphragm of the speaker 14, as a function of the audio signal S _{audio_ref} to be reproduced and of the enclosure structure. The structure of the enclosure is defined according to the characteristics of the type of enclosure considered (dimensions, electromechanical parameters). For example, a first type of enclosure is a closed enclosure (closed enclosure). A second type of enclosure is a vented enclosure. A third type of enclosure is an enclosure comprising a second passive speaker having a resonator function.

For this, the determination unit 34 is suitable for applying a unit conversion gain, depending on the peak voltage of the amplifier 16 at the output of the control device 22 and of a variable attenuation between 0 and 1 controlled by the user. This ensures the passage of the audio signal to be reproduced S _{audio_ref} to a signal γ ₀ , image of a physical quantity to reproduce. The signal γ ₀ is, for example, an acceleration of the air opposite the loudspeaker 14 or else a speed of the air to be displaced by the loudspeaker 14.

The determination unit 34 is suitable for determining the desired dynamic signal S _dyn , representative of the desired dynamic quantity A _ref , at each instant, as a function of a corresponding quantity, here the signal γ ₀ , for the displacement of the air set in motion by the enclosure comprising the loudspeaker 14.

Thus, when γ ₀ is the acceleration to be reproduced for the membrane of the speaker 14, the reference quantity A _ref is the acceleration to be reproduced for the membrane of the speaker 14 so that the operation of the speaker 14 requires to the air an acceleration γ ₀ .

For example, in the case of a closed enclosure in which the loudspeaker 14 is mounted in a closed housing, the desired reference acceleration for the membrane A _ref is equal to the desired acceleration γ ₀ for the air.

Avec :

• R _m2 : coefficient de fuites acoustiques de l'enceinte ;
• M _m2 : inductance équivalente à la masse d'air dans l'évent ;
• K _m2 : raideur de l'air dans l'enceinte.
• x ₀ : position de l'air total déplacé par la membrane et l'évent
• $v_0=\frac{{\mathit{dx}}_0}{\mathit{dt}}:$
  
  vitesse de l'air total déplacé par la membrane et l'évent
• ${\gamma }_0=\frac{{\mathit{dv}}_0}{\mathit{dt}}:$
  
  accélération de l'air total déplacé.

In the case of a vented enclosure in which the loudspeaker is mounted, the desired reference acceleration for the membrane A _ref is, for example, obtained by the following relation: $${\mathrm{AT}}_{\mathit{ref}}={\gamma }_D={\gamma }_0+\frac{K_{m2}}{R_{m2}}{v}_0+\frac{K_{m2}}{M_{m2}}{x}_0$$

With:

• R _{m 2} : coefficient of acoustic leaks from the enclosure;
• M _{m 2} : inductance equivalent to the air mass in the vent;
• K _{m 2} : stiffness of the air in the enclosure.
• x ₀ : position of the total air displaced by the membrane and the vent
• $v_0=\frac{{\mathit{dx}}_0}{\mathit{dt}}:$
  
  speed of the total air displaced by the membrane and the vent
• ${\gamma }_0=\frac{{\mathit{dv}}_0}{\mathit{dt}}:$
  
  acceleration of the total air displaced.

In this case, the desired reference acceleration for the membrane A _ref is corrected for the structural dynamic quantities x _o , v _o of the enclosure, the latter being different from the dynamic quantities relating to the membrane of the loudspeaker.

Avec :

• x _0R donné par filtrage par un filtre passe-haut de x ₀ : $$x_{0R}=\frac{s^2}{{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">s</figure-callout>}}^2+\frac{R_{m3}}{M_{m2}}s+\frac{K_{m3}}{M_{m2}}}{x}_0$$
  
• K _m3 la constante de raideur mécanique de la membrane du radiateur passif.
• R _m3 la résistance de pertes mécaniques de la membrane du radiateur passif.

In the case of an enclosure comprising a passive radiator formed by a membrane, the reference acceleration of the membrane A _ref is, for example, given by: $${\mathrm{AT}}_{\mathit{ref}}={\gamma }_0+\frac{K_{m2}}{R_{m2}}{v}_0+\frac{K_{m2}}{M_{m2}}{x}_{0R}$$

With:

• x _{0 R} given by filtering by a high-pass filter of x ₀ : $$x_{0R}=\frac{s^2}{{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">s</figure-callout>}}^2+\frac{R_{m3}}{M_{m2}}s+\frac{K_{m3}}{M_{m2}}}{x}_0$$
  
• K _{m 3} the mechanical stiffness constant of the membrane of the passive radiator.
• R _{m 3} the resistance of mechanical losses of the membrane of the passive radiator.

Optionally, the determination unit 34 is able to filter the frequencies of the desired dynamic signal S _dyn strictly lower than a frequency f _{min in} order to limit the reproduction of the excessively low frequencies. Filtering is, for example, carried out with one or more successive high-pass filters.

The duplication unit 36 is configured to duplicate, at each instant, the desired dynamic signal S _{dyn in} order to obtain two identical desired dynamic signals S _dyn1 and S _dyn2 .

The first processing unit 38 is configured to process, at each instant, the first desired dynamic signal S _dyn1 to obtain a first processed signal S _dyn1 'whose frequencies are less than or equal to a predetermined frequency.

The predetermined frequency is, for example, included in a frequency interval centered on the resonant frequency of the loudspeaker 14 and extending over at most 200 Hz. The resonant frequency of the loudspeaker 14 is defined as the frequency resonance of the speaker membrane 14.

For example, the predetermined frequency is less than or equal to 200 Hz.

In the example illustrated by figure 3 , the first processing unit 38 comprises, successively arranged in series, an excursion limiter 50, a filtering module 54, a first determination module 56, a current limiter 58, a second determination module 60, a voltage 62 and, optionally, an additional filtering unit 64.

The excursion limiter 50 forms the input of the first processing unit 38 and is configured to receive the first desired dynamic signal S _dyn1 . The excursion limiter 50 is configured to determine, at each instant, an excursion signal S _exc , representative of the excursion of the membrane of the loudspeaker 14, as a function of the first desired dynamic signal S _dyn1 . The excursion of the diaphragm of the loudspeaker 14 is defined as the distance of the diaphragm at an instant t, from its nominal equilibrium position. Typically, when the membrane undergoes an excursion exceeding the maximum acceptable excursion by the membrane, the loudspeaker 14 is in a non-linear operating regime, which can damage the loudspeaker 14. The maximum acceptable excursion is , for example, less than or equal to 10 mm.

The excursion limiter 50 is configured to determine the maximum excursion of the excursion signal S _exc .

When the maximum excursion determined is strictly greater than the maximum acceptable excursion, the excursion limiter 50 is configured to apply a first attenuation gain to the excursion signal S _exc to obtain an attenuated excursion signal S _{exc_att} .

The filter module 54 is configured to filter the frequencies of the attenuated excursion signal S _{exc_att} strictly greater than the predetermined frequency to obtain a filtered excursion signal S _{exc_filt} .

Advantageously, the filter module 54 makes it possible to keep only the very low (very serious) frequencies, typically below 200 Hz, or even below 100 Hz.

The filter module 54 is also configured to determine intermediate dynamic quantities from the attenuated excursion signal S _{exc_att} . These intermediate dynamic quantities, denoted G _ref , are, for example, the excursion of the membrane of the loudspeaker 14, the derivative of the excursion corresponding to a speed and the second derivative of the excursion corresponding to an acceleration.

The first determination module 56 is configured to determine a first signal in intensity S _int1 , representative of the intensity of the current intended to circulate in the coil of the speaker 14 as a function of the filtered excursion signal S _{exc_filt} and of a electromechanical modeling of the loudspeaker 14. More precisely, the intensity of the current is also determined as a function of the intermediate dynamic quantities G _ref .

The electromechanical modeling of the loudspeaker 14 is, for example, a table and or a set of polynomials, stored in a memory of the control device 22. The electromechanical modeling makes it possible to define electromechanical parameters P _mecha and electrical P _elec from the filtered excursion signal S _{exc_filt} and more precisely intermediate dynamic quantities G _ref , The electromechanical parameters P _mechanical and electrical P _elec are used in the calculation of the first signal in intensity S _int1 .

The electromechanical P _mechanical and electrical P _elec parameters are, for example, obtained using the models described in the application. FR 3 018 025 A in the case of a closed enclosure and a vent enclosure.

The electromechanical parameters P _mecha include, for example, the magnetic flux BI picked up by the coil produced by the magnetic circuit of the loudspeaker 14, the stiffness of the loudspeaker 14 denoted K _mt , the viscous mechanical friction of the loudspeaker 14 denoted R _mt , and the moving mass of the whole of the loudspeaker 14 denoted M _mt .

For example, the modeling of the mechanical part of the loudspeaker 14 comprises, in a single closed loop circuit, a voltage generator BI (x, i). I corresponding to the motive force produced by the current i circulating in the coil of the loudspeaker 14. The magnetic flux BI (x, i) depends on the position x of the membrane as well as on the intensity i circulating in the coil.

This modeling takes into account the viscous mechanical friction R _mt corresponding to a resistance in series with a coil corresponding to the overall moving mass M _mt , the stiffness corresponding to a capacitor of capacity C _mt (x) equal 1 / K _mt ( x). Thus, the stiffness depends on the position x of the membrane.

où L_e est l'inductance de la bobine et dépend de la position x de la membrane. La variable v représente la vitesse de la membrane.Finally, the modeling circuit includes a generator representative of the force resulting from the reluctance of the magnetic circuit denoted F _r (x, i) and equal to $\frac{1}{2}{i}^2\frac{{\mathit{d}L}_e\left(x\right)}{\mathit{dx}}$

where L _e is the inductance of the coil and depends on the position x of the membrane. The variable v represents the speed of the membrane.

The electrical parameters P _elec include the inductance Le of the coil of loudspeaker 14, the para-inductance L2 of the coil and the loss-iron equivalent R2.

For example, the modeling of the electrical part of the loudspeaker 14 of a closed enclosure is formed of a closed loop circuit. It comprises an electromotive force generator eu connected in series with a resistance representative of the resistance Re of the coil of the loudspeaker 14. This resistance is connected in series with an inductance Le (x, i) representative of the inductance of the loudspeaker coil 14. This inductance depends on the intensity i flowing in the coil and the position x of the membrane.

To take account of magnetic losses and inductance variations by the effect of eddy currents, a parallel circuit RL is connected in series at the output of the coil. A resistance of value R ₂ (x, i) depending on the position of the membrane x and the intensity i flowing in the coil is representative of the loss-iron equivalent. Likewise, an inductance coil L ₂ (x, i) also depending on the position x of the membrane and the intensity i flowing in the circuit is representative of the para-inductance of the loudspeaker 14.

représentative de l'effet de la variation dynamique de l'inductance avec la position.Are also connected in series in the modeling, a voltage generator producing a voltage BI (x, i) .v representative of the counterelectromotive force of the moving coil in the magnetic field produced by the magnet and a second generator producing a voltage g (x, i) .v with $\mathrm{g}\left(\mathrm{x},\mathrm{i}\right)=\mathrm{i}\frac{{\mathit{dL}}_e\left(x,i\right)}{\mathit{dx}}$

representative of the effect of the dynamic variation of the inductance with the position.

In general, we note that, in this modeling, the flux BI captured by the coil, the stiffness K _mt and the inductance of the coil L _e depend on the position x of the membrane, the inductance L _e and the flux BI also depend on the current i flowing in the coil.

Preferably, the inductance of the coil L _e , the inductance L ₂ and the term g depend on the intensity i, in addition to depending on the displacement x of the membrane.

$$L_2\frac{{\mathit{di}}_2}{\mathit{dt}}=R_2\left(i-i_2\right)$$

$$\mathit{Bl}\left(x,i\right)i=R_{\mathit{mt}}v+M_{\mathit{mt}}\frac{\mathit{dv}}{\mathit{dt}}+K_{\mathit{mt}}\left(x\right)x+\frac{1}{2}{i}^2\frac{{\mathit{dL}}_e\left(x,i\right)}{\mathit{dx}}$$

From the models of the mechanical part and the electric part of the loudspeaker 14, the following equations are defined: $$u_e={\mathrm{R}}_{e}i+L_e\left(x,i\right)\frac{\mathit{di}}{\mathrm{dt}}+R_2\left(i-{\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">i</figure-callout>}}_2\right)+\mathit{Bl}\left(x,i\right)\mathit{v}+i\underset{g\left(\mathrm{<figure-callout\; id="2"\; label="x\; i\; L"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">x\; </figure-callout>},i\right)}{\underbrace{\frac{{\mathit{dL}}_e\left(x,i\right)}{\mathit{dx}}v}}$$

$$L_{}$$$${}_2\frac{{\mathit{di}}_2}{\mathit{dt}}=R_2\left(i-{\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">i</figure-callout>}}_2\right)$$

$$\mathit{Bl}\left(x,i\right)i=R_{\mathit{mt}}v+M_{\mathit{mt}}\frac{\mathit{dv}}{\mathit{dt}}+K_{\mathit{mt}}\left(x\right)x+\frac{1}{2}{\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">i</figure-callout>}}^2\frac{{\mathit{dL}}_e\left(x,i\right)}{\mathit{dx}}$$

$$\frac{d}{\mathit{dt}}\left(G_1\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)i_{\mathit{ref}}\right)=R_{\mathit{mt}}{A}_{\mathit{ref}}+M_{\mathit{mt}}{\mathit{dA}}_{\mathit{ref}}/\mathit{dt}+K_{\mathit{mt}}\left(x_{\mathit{ref}}\right)v_{\mathit{ref}}$$

avec $$G_1\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)=\mathit{Bl}\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)-\frac{1}{2}{i}_{\mathit{ref}}\frac{{\mathit{dL}}_e\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)}{\mathit{dx}}\mathrm{.}$$

For example, the intensity i _ref of the first signal in intensity S _int1 and the derivative di _{ref /} dt of such an intensity satisfy the following two equations: $$G_1\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)i_{\mathit{ref}}=R_{\mathit{mt}}{v}_{\mathit{ref}}+M_{\mathit{mt}}{\mathrm{AT}}_{\mathit{ref}}+K_{\mathit{mt}}\left(x_{\mathit{ref}}\right)x_{\mathit{ref}}$$

$$\frac{d}{\mathit{dt}}\left(G_1\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)i_{\mathit{ref}}\right)=R_{\mathit{mt}}{\mathrm{AT}}_{\mathit{ref}}+M_{\mathit{mt}}{\mathit{dA}}_{\mathit{ref}}/\mathit{dt}+K_{\mathit{mt}}\left(x_{\mathit{ref}}\right)v_{\mathit{ref}}$$

with $$G_1\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)=\mathit{Bl}\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)-\frac{1}{2}{i}_{\mathit{ref}}\frac{{\mathit{dL}}_e\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)}{\mathit{dx}}\mathrm{.}$$

As a variant, the intensity i _ref of the first signal of intensity S _int1 is obtained by means of one of the embodiments described in the application FR 3 018 025 A .

The current limiter 58 is configured to fix at a predetermined intensity value all the values of the first signal in intensity S _int1 strictly greater than a predetermined intensity value and thus obtain a first signal in attenuated intensity S _{int1_att} . This makes it possible to avoid exceeding the acceptable current limit of the amplifier 16. For example, the predetermined intensity value is less than or equal to 15 amperes (A).

The second determination module 60 is configured to determine a first voltage signal S _tens1 , representative of the voltage across the loudspeaker 14, as a function of the filtered excursion signal S _{exc_filt} , of the electromechanical modeling of the loudspeaker 14 and the first attenuated intensity signal S _{int1_att} .

In an exemplary embodiment, the second determination module 60 is suitable for estimating the resistance R _e of the loudspeaker 14 as a function of the intermediate dynamic quantities G _ref , the intensity of the reference current i _ref and its derivative di _ref / dt and, depending on the embodiment envisaged, the temperature measured on the magnetic circuit of the loudspeaker 14 denoted T _{m_measured} or the intensity measured at across the coil marked I _{_measured} . An example of estimation of the resistance R _e is described in the request. FR 3 018 025 A .

$$u_{\mathit{ref}}={\mathrm{R}}_e{i}_{\mathit{ref}}+L_e\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)\frac{{\mathit{di}}_{\mathit{ref}}}{\mathit{dt}}+\mathit{Bl}\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)v_{\mathit{ref}}+\underset{g\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)}{\underbrace{i_{\mathit{ref}}\frac{{\mathit{dL}}_e\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)}{\mathit{dt}}{v}_{\mathit{ref}}}}$$

In the same exemplary embodiment, the second determination module 60 is able to calculate the voltage across the loudspeaker 14 as a function of intermediate dynamic quantities G _ref , of the reference current i _ref and of its derivative di _ref / dt, electrical parameters P _elec and resistance R _e . For this, the second determination module 60 implements the following two equations: $${\mathrm{<figure-callout\; id="2"\; label="u"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">u</figure-callout>}}_2+\frac{L_2\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)}{R_2\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)}\frac{{\mathit{of}}_2}{\mathit{dt}}=L_2\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)\frac{{\mathit{di}}_{\mathit{ref}}}{\mathit{dt}}$$

$$u_{\mathit{ref}}={\mathrm{R}}_e{i}_{\mathit{ref}}+L_e\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)\frac{{\mathit{di}}_{\mathit{ref}}}{\mathit{dt}}+\mathit{Bl}\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)v_{\mathit{ref}}+\underset{g\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)}{\underbrace{i_{\mathit{ref}}\frac{{\mathit{dL}}_e\left(x_{\mathit{ref}},i_{\mathit{ref}}\right)}{\mathit{dt}}{v}_{\mathit{ref}}}}$$

As a variant, the voltage of the first voltage signal S _tens1 is obtained by means of one of the embodiments described in the application FR 3 018 025 A .

The voltage limiter 62 is configured to fix, at a predetermined voltage value, all the values of the first voltage signal S _tens1 strictly greater than a predetermined voltage value and thus obtain a first attenuated voltage signal S _{tens1_att} .

The predetermined voltage value is, for example, greater than or equal to 30 Volts (V).

The additional filtering module 64 is configured to filter the frequencies of the first attenuated voltage signal S _{tens1_att} strictly greater than the predetermined frequency. This makes it possible to remove any noise brought by the current limiter 58 and the voltage limiter 62.

Optionally, the additional filtering module 64 is also configured to filter all the frequencies which are less than or equal to a frequency called low frequency, for example equal to the frequency f _min defined previously. This again makes it possible to eliminate any noise resulting from the various processing operations carried out on the signal when passing through the various limiters and modules of the first processing unit 38.

The output of the additional filter module 64 is the first processed signal S _dyn1 '.

As a variant, when the first processing unit 38 does not include an additional filtering module 64, the first processed signal S _dyn1 'is the first attenuated voltage signal S _{tens1_att} .

An example of a second processing unit 40 is illustrated by the figure 4 .

The second processing unit 40 is configured to process, at each instant, the second desired dynamic signal S _dyn2 to obtain a second processed signal S _dyn2 'whose frequencies are strictly greater than the predetermined frequency.

The second processing unit 40 comprises a filtering module 70, a first determination module 72, a second determination module 74, a voltage limiter 76 and, optionally, an additional filtering module 80.

The filter module 70 is configured to filter the frequencies of the second desired dynamic signal S _dyn2 less than or equal to the predetermined frequency to obtain a second filtered signal S _{dyn2_filt} .

Advantageously, the filtering module 70 makes it possible to keep only the mid low frequencies, typically above 100 Hz, or even above 200 Hz.

The filtering module 70 is also configured to determine intermediate dynamic quantities as a function of the second desired dynamic signal S _dyn2 . These intermediate dynamic quantities, denoted G _ref , are, for example, the excursion of the membrane of the loudspeaker 14, the derivative of the excursion corresponding to a speed and the second derivative of the excursion corresponding to an acceleration.

The first determination module 72 is configured to determine a second signal in intensity S _int2 , representative of the intensity of the current intended to circulate in the coil of the loudspeaker 14, as a function of the second filtered signal S _dyn2-filt and of electromechanical modeling of the loudspeaker 14. The electromechanical modeling of the loudspeaker 14 is for example identical to the electromechanical modeling used for the first processing unit 38.

For example, the first determination module 72 of the second processing unit 40 operates in the same way as the first determination module 56 of the first processing unit 38.

The second determination module 74 is configured to determine a second voltage signal S _tens2 , representative of the voltage of the loudspeaker 14, as a function of the second filtered signal S _{dyn2_filt} , the second intensity signal S _int2 and the electromechanical modeling of the speaker 14.

For example, the second determination module 74 of the second processing unit 40 operates in the same way as the second determination module 60 of the first processing unit 38.

The voltage limiter 76 is configured to determine the maximum voltage of the second voltage signal S _tens2 .

When the determined maximum voltage is strictly greater than a maximum acceptable voltage, the voltage limiter 76 is configured to apply a second attenuation gain to the second voltage signal S _tens2 to obtain a second attenuated voltage signal S _{tens2_att} . The maximum acceptable voltage is, for example, identical to the predetermined voltage value of the voltage limiter 62 of the first processing unit 38. The second attenuation gain is advantageously different from the first attenuation gain.

As a variant or in addition, the voltage limiter 76 is configured to fix at a predetermined voltage value all the values of the second voltage signal St _ens2 greater than the predetermined voltage value and thus obtain the second attenuated voltage signal S _{tens2_att} .

The additional filtering module 80 is configured to filter the frequencies of the attenuated voltage signal less than or equal to the predetermined frequency. This makes it possible to remove any noise brought by the voltage limiter 76 and the modules of the second processing unit 40.

The output of the additional filter module 80 is the second processed signal S _dyn2 '. As a variant, when the second processing unit 40 does not include an additional filtering module 80, the second processed signal S _dyn2 'is the second attenuated voltage signal S _{tens2_att} .

The combination unit 42 is configured to perform, at each instant, the linear combination of the first and the second processed signal S _dyn2 'to obtain the control signal S _control of the loudspeaker 14.

Advantageously, the coefficients of the linear combination are all equal to one so that the combination unit 42 performs the sum of the first and the second processed signal S _dyn2 'to obtain the command signal S _command of the loudspeaker 14.

An example of operation of the control device 22 will now be described.

Initially, the control device 22 receives as input the audio signal S _{audio_ref} to be reproduced.

The determination unit 34 of the control device 22 determines, at each instant, the desired dynamic signal S _dyn , representative of a desired dynamic quantity A _ref of the diaphragm of the speaker 14, as a function of the audio signal S _{audio_ref} à reproduce and structure the enclosure.

Optionally, the determination unit 34 filters the frequencies of the desired dynamic signal S _dyn strictly lower than the frequency f _{min in} order to limit the reproduction of the excessively low frequencies.

The duplication unit 36 then duplicates the desired dynamic signal S _{dyn in} order to obtain two identical dynamic signals S _dyn1 and S _dyn2 .

The first processing unit 38 processes the first desired dynamic signal S _dyn1 to obtain a first processed signal S _dyn1 'whose frequencies are less than or equal to a predetermined frequency.

For this, the excursion limiter 50 determines, at each instant, an excursion signal S _exe , representative of the excursion of the diaphragm of the loudspeaker 14, as a function of the first desired dynamic signal S _dyn1 . Then, the excursion limiter 50 determines the maximum excursion of the excursion signal. When the maximum excursion determined is strictly greater than a maximum acceptable excursion, the excursion limiter 50 applies a first attenuation gain to the excursion signal S _exc to obtain an attenuated excursion signal S _{exc_att} ,

The filter module 54 then filters the frequencies of the attenuated excursion signal S _{exc_att} strictly greater than the predetermined frequency to obtain a filtered excursion signal S _{exc_filt} .

Then, the first determination module 56 determines a first signal in intensity S _int1 , representative of the intensity of the current intended to circulate in the coil of the loudspeaker 14 as a function of the filtered excursion signal S _{exc_filt} and of the electromechanical modeling. speaker 14.

The current limiter 58 then fixes, at a predetermined intensity value, all the values of the first intensity signal S _int1 strictly greater than the predetermined intensity value in order to obtain a first attenuated intensity signal S _{int1_att} .

The second determination module 60 then determines a first voltage signal S _tens1 , representative of the voltage across the loudspeaker 14, as a function of the filtered excursion signal S _{exc_filt} , of the electromechanical modeling of the loudspeaker 14 and the first attenuated intensity signal S _{int1_att} .

The voltage limiter 62 then sets, at a predetermined voltage value, all the values of the first voltage signal S _tens1 strictly greater than a predetermined voltage value to obtain a first attenuated voltage signal S _{tens1_att} .

Optionally, the additional filtering module 64 filters the frequencies of the first attenuated voltage signal S _{tens1_att} strictly greater than the predetermined frequency. Optionally, the additional filtering module 64 filters all the frequencies which are less than or equal to a frequency called low frequency. The output of the additional filter module 64 is the first processed signal S _dyn1 '.

In parallel with the first processing unit 38, the second processing unit 40 processes the second desired dynamic signal S _dyn2 to obtain a second processed signal S _dyn2 'whose frequencies are strictly higher than the predetermined frequency.

For this, the filter module 70 filters the frequencies of the second desired dynamic signal S _dyn2 less than or equal to the predetermined frequency to obtain a second filtered signal S _{dyn2_filt} .

The first determination module 72 then determines a second signal in intensity S _int2 , representative of the intensity of the current intended to flow in the coil of the speaker 14, as a function of the second filtered signal S _{dyn2_filt} and of the electromechanical modeling. speaker 14.

The second determination module 74 then determines a second voltage signal S _tens2 , representative of the loudspeaker voltage 14, as a function of the second filtered signal S _{dyn2_filt} , of the second intensity signal S _int2 and of the electromechanical modeling of the speaker 14.

Then, the voltage limiter 76 determines the maximum voltage of the second voltage signal S _tens2 . When the determined maximum voltage is strictly greater than the maximum acceptable voltage, the voltage limiter 76 applies a second attenuation gain to the second voltage signal S _tens2 to obtain a second attenuated voltage signal S _{tens2_att} ,

The additional filtering module 80 filters the frequencies of the attenuated voltage signal less than or equal to the predetermined frequency to obtain the second processed signal S _dyn2 '.

Finally, the combination unit 42 performs the linear combination of the first and second processed signals S _dyn1 'and S _dyn2 ' to obtain the command signal S _command of the loudspeaker 14.

Thus, the control device 22 makes it possible to carry out different processing on two frequency bands which are disjoint from an input signal. This is of particular interest for processing the bass (bass frequencies) of a speaker. One of the limiting factors for very low frequencies (for example below 150 Hz) is the excursion of the diaphragm of the speaker 14, as well as the voltage sent to the speaker 14. Also, the control device 22 makes it possible to apply a specific processing on the very low frequencies of the signal in order to limit, on the one hand, the excursion of the membrane above a predetermined value and to limit, on the other hand , the voltage sent to loudspeaker 14. Conversely for intermediate low frequencies (for example, bass above 150 Hz) the excursion limitation is optional. On the other hand, the limiting factor is the voltage which is applied to the loudspeaker 14, hence the addition of a specific treatment for such intermediate frequencies.

Thus, the control device 22 makes it possible to optimize the reproduction of the low frequencies, taking into account the various constraints of the system (excursion, voltage), in particular for woofers with extended frequency band (typically greater than 200 Hz).

The control device 22 therefore makes it possible to reduce the distortion in the signal reproduced by the loudspeaker 14 while improving the protection of the diaphragm of the loudspeaker 14. This makes it possible to improve the restitution of the signal by the loudspeaker 14 .

Those skilled in the art will understand that the control device 22 described is not limited to the examples of figures 2 to 4 , nor to the particular examples of the description. A variant consists, for example, of combining one or more of the examples or variants described above when the combination is compatible.

Claims (10)

Control device (22) of a loudspeaker (14) in an enclosure, the loudspeaker (14) comprising a membrane, the enclosure having a structure, the device (22) comprising: - an input (30) for an audio signal (S _{audi_ref} ) to be reproduced, - an output (32) for supplying a control signal (S _control ) to the loudspeaker (14), - a unit (34) for determining a desired dynamic signal (S _dyn ), representative of a desired dynamic quantity (A _ref ) of the diaphragm of the loudspeaker (14), as a function of the audio signal (S _{audio_ref} ) to reproduce and the structure of the enclosure, a unit (36) for duplicating the desired dynamic signal (S _dyn ) to obtain two identical desired dynamic signals (S _dyn1 , S _dyn2 ), a first processing unit (38) configured to process the first desired dynamic signal (S _dyn1 ) to obtain a first processed signal (S _dyn1 ') whose frequencies are less than or equal to a predetermined frequency, a second processing unit (40) configured to process the second desired dynamic signal (S _dyn2 ) to obtain a second processed signal (S _dyn2 ') whose frequencies are strictly greater than the predetermined frequency, and - a combination unit (42) of the first and second processed signal (S _dyn1 ', S _dyn2 ') to obtain the control signal (S _command ) from the loudspeaker (14). Device (22) according to claim 1, in which the first processing unit (38) comprises an excursion limiter (50) configured to: - determining an excursion signal (S _exc ), representative of the excursion of the loudspeaker membrane (14), as a function of the first desired dynamic signal (S _dyn1 ), - determine the maximum excursion of the excursion signal (S _exc ), and - when the maximum excursion determined is strictly greater than a maximum acceptable excursion, apply a first attenuation gain to the excursion signal (S _exc ) to obtain an attenuated excursion signal (S _{exc_att} ), the first processed signal (S _dyn1 ') being obtained as a function of the attenuated excursion signal (S _{exc_att} ). Device (22) according to claim 2, in which the loudspeaker (14) comprises at least one coil, the first processing unit (38) comprising: a module (54) for filtering the frequencies of the attenuated excursion signal (S _{exc_att} ) strictly greater than the predetermined frequency in order to obtain a filtered excursion signal (S _{exc_filt} ), - a module (56) for determining a first intensity signal (S _int1 ), representative of the intensity of the current intended to flow in the coil of the loudspeaker (14), as a function of the filtered excursion signal ( S _{exc_filt} ) and an electromechanical model of the loudspeaker (14), and - a current limiter (58) configured to fix all the values of the first intensity signal (S _int1 ) strictly greater than the predetermined intensity value at a predetermined intensity value and thus obtain a first attenuated intensity signal ( S _{int1_att} ), the first processed signal (S _dyn1 ') being obtained as a function of the first attenuated intensity signal (S _{int1_att} ). Device (22) according to claim 3, in which the first processing unit (38) comprises: a module (60) for determining a first voltage signal (S _tens1 ), representative of the voltage across the loudspeaker (14), as a function of dynamic quantities (G _ref ) obtained by the filtering module ( 54) from the attenuated excursion signal (S _{exc_att} ), from the electromechanical modeling of the loudspeaker (14) and from the first attenuated intensity signal (S _{int1_att} ), and - a voltage limiter (62) configured to fix all the values of the first voltage signal (S _tens1 ) strictly greater than the predetermined voltage value at a predetermined voltage value and thus obtain a first attenuated voltage signal (S _{tens1_att} ), the first processed signal (S _dyn1 ') being obtained as a function of the first attenuated voltage signal (S _{tens1_att} ). Device (22) according to claim 4, in which the first processing unit (38) comprises an additional filtering module (64) configured to filter the frequencies of the first attenuated voltage signal (S _{tens1_att} ) strictly greater than the predetermined frequency, the first processed signal (S _dyn1 ') being obtained as a function of the first attenuated voltage signal (S _{tens1_att} ) filtered by the additional filtering module (64). Device (22) according to any one of Claims 1 to 5, in which the second processing unit (40) comprises: a module (70) for filtering the frequencies of the second desired dynamic signal (S _dyn2 ) less than or equal to the predetermined frequency to obtain a second filtered signal (S _{dyn2_filt} ), - a module (74) for determining a second voltage signal (S _tens2 ), representative of the voltage across the loudspeaker (14), as a function of the second filtered signal (S _{dyn2_filt} ) and an electromechanical modeling the speaker (14), the second processed signal (S _dyn2 ') being obtained as a function of the second voltage signal (S _tens2 ). Device (22) according to claim 6, in which the second processing unit (40) comprises a voltage limiter (76) configured to: - determine the maximum voltage of the second voltage signal (S _tens2 ), - when the maximum voltage determined is strictly greater than a maximum acceptable voltage, apply a second attenuation gain to the second voltage signal (S _tens2 ) to obtain a second attenuated voltage signal (S _{tens2_att} ), the second processed signal (S _dyn2 ') being obtained as a function of the second attenuated voltage signal (S _{tens2_att} ). Device (22) according to claim 7, in which the second processing unit (40) comprises an additional filtering module (80) configured to filter the frequencies of the second attenuated voltage signal (S _{tens2_att} ) less than or equal to the predetermined frequency , the second processed signal (S _dyn2 ') being obtained as a function of the second attenuated voltage signal (S _{tens2_att} ) filtered by the additional filtering module (80). Device (22) according to any one of Claims 1 to 8, in which the predetermined frequency is included in a frequency interval centered on the resonant frequency of the loudspeaker (14) and extending over at most 200 Hz. Sound reproduction installation comprising a loudspeaker (14) in an enclosure and a control device (22) for the loudspeaker (14) according to any one of claims 1 to 9.

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