EP3111668A1 - Device for controlling a loudspeaker - Google Patents

Abstract

The invention relates to a device for controlling a loudspeaker (14) in a speaker enclosure, comprising: - an input for an audio signal (Saudio_ref) to be reproduced; - an output for supplying an excitation signal from the loudspeaker. The device comprises a control unit that includes: - means (24, 25) for calculating a single desired dynamic value (Aref) of the loudspeaker diaphragm according to the audio signal (Saudio_ref) to be reproduced and the structure of the enclosure; - means (26) for calculating, at every moment in time, a plurality of desired dynamic values (Aref, dAref/dt, Vref, Xref) of the loudspeaker diaphragm according to the single desired dynamic value (Aref); - a mechanical model (36) of the loudspeaker; and - means (70, 80, 90) for calculating the excitation signal at every moment in time, without feedback loop, from the mechanical model (36) of the loudspeaker and the desired dynamic values (Aref, dAref/dt, Vref, Xref).

Description

 Device for controlling a loudspeaker

The present invention relates to a device for controlling a loudspeaker in an enclosure comprising:

 an input for an audio signal to be reproduced;

 a supply output of an excitation signal of the loudspeaker.

 Speakers are electromagnetic devices that convert an electrical signal into an acoustic signal. They introduce a nonlinear distortion that can significantly affect the acoustic signal obtained.

 Many solutions have been proposed for controlling the loudspeakers in order to make it possible to eliminate the distortions of the behavior of the loudspeaker by an appropriate command.

 A first type of solution uses mechanical sensors, typically a microphone, in order to implement a servocontrol which makes it possible to linearize the operation of the loudspeaker. The major disadvantage of such a technique is the mechanical size and non-standardization of the devices as well as high costs.

 Examples of such solutions are described for example in EP 1 351 543, US 6 684 204, US 2010/017 25 16, and US 5,694,476.

 In order to avoid the use of an undesirable mechanical sensor, open-loop type controls have been envisaged. They do not require expensive sensors. They may only use a measurement of the voltage and / or current applied across the loudspeaker.

 Such solutions are described for example in US 6,058,195 and US 8,023,668.

 However, these solutions have drawbacks in that all the non-linearities of the loudspeaker are not taken into account and these systems are complex to implement and do not offer any freedom for the choice of the corrected behavior obtained from the top. equivalent.

Document US Pat. No. 6,058,195 uses a so-called "mirror filter" technique with current control. This technique makes it possible to eliminate nonlinearities in order to obtain a predetermined model. The estimator E implemented produces an error signal between the measured voltage and the voltage predicted by the model. This error is used by the update circuit of the parameters U. Given the number of estimated parameters, the convergence of the parameters towards their true values is highly unlikely under normal operating conditions. US 8,023,668 provides an open loop control model that compensates for unwanted loudspeaker behaviors relative to a desired behavior. For this, the voltage applied to the loudspeaker is corrected by an additional voltage which cancels the unwanted behaviors of the loudspeaker with respect to the desired behavior. The control algorithm is realized by discretization in discrete time of the loudspeaker model. This makes it possible to predict the position that the membrane will have at the next time and to compare this position with the desired position. The algorithm thus achieves a sort of infinite gain servo between a desired model of the loudspeaker and the loudspeaker model so that the loudspeaker follows the desired behavior.

 As in the previous document, the control implements a correction which is calculated at each instant and added to the input signal, even if this correction in US 8,023,668 does not implement a closed feedback loop.

 The mechanisms for calculating a correction added to the input signal are complex to implement and the result obtained is sometimes unsatisfactory, the correction model proving to be inappropriate or not very effective for certain operating conditions or for certain forms of the signal. input.

 The object of the invention is to provide a satisfactory control of a loudspeaker which does not have the disadvantages of modifying the input signal by adding a correction signal calculated by comparison at each instant between a desired model. and the model of the speaker.

 For this purpose, the subject of the invention is a device for controlling a loudspeaker of the aforementioned type, characterized in that it comprises a command comprising:

 means for calculating a desired dynamic magnitude of the loudspeaker membrane as a function of the audio signal to be reproduced and the structure of the enclosure;

 means for calculating, at each moment, a plurality of desired dynamic magnitudes of the speaker membrane as a function of the only desired dynamic quantity;

 - a mechanical modeling of the loudspeaker; and

 means for calculating, at each instant, the excitation signal, without a feedback loop, from the mechanical modeling of the loudspeaker and the desired dynamic quantities.

 According to particular embodiments, the control device comprises one or more of the following characteristics:

said control furthermore comprises an electrical modeling of the loudspeaker; and the means for calculating, at each instant, the excitation signal, are specific to calculate the excitation signal in addition according to the electrical modeling of the loudspeaker;

 - the electrical modeling of the loudspeaker takes into account:

 a resistance representative of the magnetic losses of the loudspeaker; an inductance representative of a para-inductance resulting from the effect of the eddy currents in the loudspeaker;

 the electrical modeling of the loudspeaker takes into account the variation of the inductance of the loudspeaker coil as a function of the intensity flowing in the loudspeaker;

 the electrical modeling of the loudspeaker takes into account the variation of the inductance of the loudspeaker coil as a function of the position of the membrane of the coil;

 the electrical modeling of the loudspeaker takes into account the variation of the magnetic flux picked up by the speaker coil as a function of the intensity flowing in the loudspeaker;

 the electrical modeling of the loudspeaker takes into account the variation of the magnetic flux picked up by the speaker coil as a function of the position of the coil membrane;

 the electrical modeling of the loudspeaker takes into account the variation of the derivative of the inductance with respect to the time of the coil of the loudspeaker as a function of the intensity flowing in the loudspeaker;

 the electrical modeling of the loudspeaker takes into account the variation of the derivative of the inductance with respect to the time of the loudspeaker coil as a function of the position of the membrane of the coil;

 the electrical modeling of the loudspeaker takes into account the variation of the resistance of the loudspeaker coil as a function of a measured temperature of the magnetic circuit of the loudspeaker;

 the electrical modeling of the loudspeaker takes into account the variation of the resistance of the loudspeaker coil as a function of an intensity measured in the coil of the loudspeaker;

the means for calculating the desired dynamic quantities as a function of the audio signal to be reproduced comprise at least one bounded integrator characterized by a cut-off frequency limiting the integration in the band of useful bandwidth less than the cut-off frequency; the plurality of desired dynamic magnitudes is the set of values at a given instant of four functions which are derivatives of different orders of the same function;

 the means for calculating desired dynamic quantities are suitable for ensuring calculations of the desired dynamic quantities by integration and / or derivation of the audio signal to be reproduced;

 the means for calculating the excitation signal, without a feedback loop, from the desired dynamic quantities are capable of ensuring algebraic calculations of the intensity of the desired current in the coil and of the derivative with respect to the time of the intensity of the desired current in the coil;

 the mechanical modeling of the loudspeaker takes into account the mechanical friction of the loudspeaker and in that it comprises means for the resistance to depend on at least one of the desired dynamic magnitudes according to a nonlinear increasing function tending towards the infinite when at least one of the desired dynamic magnitudes tends to a predetermined value;

 the plurality of desired dynamic magnitudes comprise the acceleration of the speaker diaphragm and the position of the speaker diaphragm and in that it comprises means for limiting the acceleration in a predetermined interval, in order to limit the excursions of the position of the membrane beyond a predetermined value;

 the means for calculating the dynamic quantity of the loudspeaker membrane are suitable for applying a correction that is different from the identity, and taking into account dynamic structural magnitudes of the enclosure which are different from the dynamic quantities relating to the membrane of the loudspeaker; speaker;

 the enclosure comprises a vent and the dynamic structural magnitudes of the enclosure include at least one derivative of predetermined order of the position of the air displaced by the enclosure;

 the structural dynamic quantities of the enclosure comprise the position of the air displaced by the enclosure;

 the structural dynamic quantities of the enclosure comprise the speed of the air displaced by the enclosure;

 the enclosure is a vent enclosure and the structural dynamic quantities of the enclosure depend on at least one of the following parameters:

 - acoustic leakage coefficient of the enclosure

 - inductance equivalent to the air mass in the vent

- compliance of the air in the enclosure; the enclosure is a passive radiator enclosure and the dynamic structural magnitudes of the enclosure depend on at least one of the following parameters:

 - acoustic leakage coefficient of the enclosure

 - inductance equivalent to the mass of the passive radiator membrane - compliance of the air in the enclosure

 - mechanical losses of the passive radiator

 - mechanical compliance of the membrane.

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

 - Figure 1 is a schematic view of a sound reproduction installation;

 FIG. 2 is a curve illustrating a desired model of sound reproduction for the installation;

 FIG. 3 is a schematic view of the loudspeaker control unit;

FIG. 4 is a detailed schematic view of the unit for calculating reference dynamic quantities;

 FIG. 5 is a view of a circuit representing the mechanical modeling of the loudspeaker with a view to its control in a closed enclosure;

 FIG. 6 is a view of a circuit representing the electrical modeling of the loudspeaker with a view to its control;

 FIG. 7 is a schematic view of a first embodiment of the open loop estimation unit of the loudspeaker resistor;

 FIG. 8 is a view of a circuit of the thermal model of the loudspeaker;

 FIG. 9 is a view identical to that of FIG. 7 of an alternative embodiment of the closed loop estimation unit of the loudspeaker resistor;

 FIG. 10 is a detailed schematic view of the structural adaptation unit;

- Figure 1 1 is a view similar to that of Figure 5 of another modeling mode for an enclosure provided with a vent; and

 - Figure 12 is a view similar to that of Figure 1 1 of another embodiment for an enclosure provided with a passive radiator.

The sound reproduction installation 10 illustrated in FIG. 1 comprises, as known per se, a module 12 for producing an audio signal, such as a digital disk player connected to a loudspeaker 14 of a loudspeaker. 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. This desired model is linear or nonlinear. According to a particular embodiment, a loop 23 for measuring a physical quantity, such that the temperature of the magnetic circuit of the loudspeaker or the current flowing in the HP coil is provided between the loudspeaker 14 and the device. order 22.

 The desired model 20 is independent of the speaker used in the installation and its modeling.

The desired pattern 20 is, as illustrated in Figure 2, a function expressed as a function of the frequency ratio of the amplitude of S _in dio_ref desired signal recorded on the amplitude S _iN dio of the input signal from the module 12 .

Advantageously, for frequencies lower than a frequency f _min , this ratio is a function converging towards zero when the frequency tends to zero, to limit the reproduction of excessively low frequencies and thus to avoid displacements of the speaker's membrane out of the ranges. recommended by the manufacturer.

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

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

The control device 22, the detailed structure is illustrated in Figure 3, is arranged in input of the amplifier 16. This device is capable of receiving as input the S audio _signal reproducing dio_ref as defined at the output of model 20 and to output a signal U _re f, forming a speaker excitation signal which is supplied for amplification to the amplifier 16. This signal L is adapted to take account of the non-linearity of the loudspeaker. speaker 14.

 The control device 22 comprises means for calculating different quantities as a function of the values of derivatives or integrals of other quantities defined at the same times.

 For computational requirements, the values of the unknown quantities at the instant n are taken equal to the corresponding values of the instant n-1. The values of the instant n-1 are preferably corrected by a prediction with the order 1 or 2 of their values using the derivatives of higher orders known at time n-1.

According to the invention, the control device 22 implements a control using in part the principle of the differential flatness which makes it possible to define a reference control signal of a differentially flat system from sufficiently smooth reference paths. As illustrated in Figure 3, the control module 22 receives as input the S audio _signal dio_ref to reproduce from the desired model 20. A unit 24 for applying a unit conversion gain, depending on the peak voltage of the amplifier 16 and a variable attenuation between 0 and 1 controlled by the user, ensures the passage of the reference audio signal S _in dio_ref a γ ₀ signal, image of a physical quantity to be reproduced. The signal γ ₀ is, for example, an acceleration of the air opposite the loudspeaker or a speed of the air to be displaced by the loudspeaker 14. In the following, it is assumed that the signal γ ₀ is the acceleration of the air set in motion by the enclosure.

At the output of the amplification unit 24, the control device comprises a unit 25 for structural adaptation of the signal to be reproduced as a function of the structure of the enclosure in which the loudspeaker is used. This unit is able to provide a reference variable A _ref desired at each instant for the speaker membrane from a corresponding quantity, here the signal γ ₀ , for the displacement of the air set in motion by the speaker with the speaker.

Thus, in the example considered, the reference variable A _ref , calculated from the acceleration of the air to be reproduced γ ₀ , is the acceleration to be reproduced for the speaker diaphragm so that the operation of the top -parleur imposes on the air an acceleration γ ₀ .

In the case of a closed enclosure in which the loudspeaker 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.

This reference quantity A _ref is introduced into a calculation unit 26 of dynamic reference quantities capable of supplying, at each instant, the value of the derivative with respect to the time of the reference variable denoted dA _ref / dt as well as the values first and second integrals with respect to the time of this reference quantity noted respectively V _ref and X _re f.

All reference dynamic quantities noted in the following G _ref.

FIG. 4 illustrates a detail of the computing unit 26. The input A _ref is connected to a branching unit 30 on the one hand and to a bounded integration unit 32 on the other hand whose output is itself connected to another bounded integration unit 34.

Thus, at the output of the units 30, 32 and 34 are respectively obtained the derivative of the acceleration dA _{ref /} dt, the first integral V _ref and the second integral X _ref of the acceleration.

The bounded integration units are formed of a first-order low-pass filter and are characterized by a cut-off frequency F _OB F-

The use of bounded integration units allows the quantities used in the control device 22 to be the derivatives or the integrals of each other only in the useful bandwidth, ie for the higher frequencies. to the cutoff frequency F ₀ BF- This makes it possible to control the excursion at low frequency of the quantities considered.

In normal operation, the cut-off frequency F _0BF is chosen so as not to influence the signal at the low frequencies of the useful bandwidth.

The cut-off frequency F ₀ BF is taken less than one tenth of the frequency f _min of the desired model 20.

 The control device 22 comprises, in a memory, a table and / or a set of electromechanical parameter polynomials 36 as well as a table and / or a set of polynomials of the electrical parameters 38.

These tables 36 and 38 are adapted to define, as a function of the dynamic reference variables G _ref received at the input, the electromechanical parameters P _mec and electrical P _e iec respectively. These parameters P _Meca and P _é i _ec are obtained respectively from a mechanical modeling of the loudspeaker as shown in Figure 5 and an electrical model of the speaker as shown in Figure 6.

 In these figures, the loudspeaker is assumed to be installed on a closed housing devoid of vent, the membrane being at the interface between the outside and the inside of the housing.

The electromechanical parameters P _mc a include the magnetic flux picked up by the coil denoted B1 produced by the magnetic circuit of the HP, the stiffness of the loudspeaker denoted K _mt , the viscous mechanical friction of the loudspeaker denoted R _mt , and the moving mass. of the entire speaker noted M _mt .

 The modeling of the mechanical part of the loudspeaker illustrated in FIG. 5 comprises, in a single closed loop circuit, a voltage generator 40 B1 (x, i) i corresponding to the driving force produced by the current flowing in the speaker coil. The magnetic flux B1 (x, i) depends on the position x of the membrane as well as the intensity i flowing in the coil.

This modeling takes into account the viscous mechanical friction R _mt corresponding to a resistor 42 in series with a coil 44 corresponding to the moving mass of set M _mt , the stiffness corresponding to a capacitor 46 of capacitance C _mt (x) equal 1 / K _mt (x). Thus, the stiffness depends on the position x of the membrane.

 Finally, the circuit comprises a generator 48 representative of the force resulting from the

1? (XL (χ reluctance of the magnetic circuit denoted by F _R (x, i) and equal to -r ^ where L _e is the inductance of the coil and depends on the position x of the membrane

 Variable v represents the speed of the membrane.

The Pelec electrical parameters include the coil inductance Le, the coil inductance L2 and the loss-iron equivalent R2. The modeling of the electrical part of the loudspeaker of a closed enclosure is illustrated in FIG. 6. It is formed of a closed-loop circuit. It comprises a generator 50 of electromotive force ue connected in series with a resistor 52 representative of the resistor Re of the coil of the loudspeaker. This resistor 52 is connected in series with an inductance Le (x, i) representative of the inductance of the coil of the loudspeaker. This inductance depends on the intensity i flowing in the coil and the position x of the membrane.

To account for magnetic losses and variations in inductance due to the effect of eddy currents, a parallel circuit RL is connected in series at the output of the coil 54. A resistance 56 of value R ₂ (x, i) depending on the position the membrane x and the intensity i flowing in the coil is representative of the loss-iron equivalent. Likewise, a coil 58 of inductance L ₂ (x, i) also depends on the position x of the membrane and the intensity i flowing in the circuit is representative of the para-inductance of the loudspeaker.

 Are also mounted in series in modeling, a voltage generator

60 producing a voltage B1 (x, i) .v representative of the counter-electromotive force of the moving coil in the magnetic field produced by the magnet and a second dL (x 0

generator 62 producing a voltage g (x, i) .v with g (x, i) = i ^ representative of the effect of the dynamic variation of the inductance with the position.

In general, we note that, in this modelization, the flux Bl 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 Bl also depend on the current 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.

From the models explained with reference to FIGS 5 and 6, the following equations are defined: u _e

L ₂ = R (i - i ₂ )

2 dt ² Bl (x, i) i = R _{miV + Mml}

The control module 22 further comprises a unit 70 for calculating the reference current i _re f and its derivative di _re f _/ dt. This unit receives as input the quantities reference dynamics G _re f and the mechanical parameters P _m echa- This calculation of the reference current l _ref and its derivative d _/ dt satisfy both equations:

^G l ( ^X ref> ff = ^R mt ^V ref + ^M mAref + ^K mt ( ^X r, f ef

 d_

{G ₁ (x _ref, i _ref) i _ref) = R _ref + _mt A M I _{ref mt} dA dt + K _mt (x _ref) v ref

dt with G, (x _ref , i _ref ) = B1 (x _ref , i _ref

Thus, the current i _re f and its derivative di _re f _/ dt are obtained by an algebraic calculation from the values of the vectors entered by an exact analytical calculation or a numerical resolution if necessary according to the complexity of Gi (x, i ).

The derivative of the current di _re f _/ dt is thus preferably obtained by an algebraic calculation or otherwise by numerical derivation.

To avoid excessive displacement of the speaker diaphragm, a displacement X _max is imposed on the control module. This is made possible by the use of a separate dynamic reference quantity calculating unit 26 and a structural matching unit.

The limitation of the deflection is carried out by a device of "virtual wall" which prevents the membrane of the loudspeaker to exceed a certain limit related to X _max . To do this, as the position x _ref approaches its threshold, the energy required for the position approaches the virtual wall becomes larger and larger (non-linear behavior) to be infinite on the wall with the possibility of imposing asymmetrical behavior. For this, the viscous mechanical friction R _mt 42 is increased non-linearly as a function of the position x _re f of the membrane.

According to yet an embodiment, for limiting the travel, the acceleration A _ref is dynamically maintained within minimum and maximum limits to ensure that the position X _ref of the membrane does not exceed X _ma x.

In the case where, according to the embodiment, the deflection X _re f of the membrane is limited to X _re f _sa t, and the acceleration of the membrane A _ref to A _{ref sat} , the magnitude x ₀ and v ₀ are recalculated at time n by the following algorithm:

Yo in its _t) = A _{ref sat} (n) - v _{0 sat} (n - I) - - - x _{Q sat} (n - 1)

v _{0 sat} (n) = ₀ bounded integrator γ _sat (n) (identical to 32)

x _{0 sat} (n) = bounded integrator of v _{0 sat} (n) (same as 34)

v _re f _sat (n) = bounded integrator of A _re f _sat (n) (same as 32) Calculation of the reference current U and its derivative dl _{reI /} dt then satisfy the two following equations:

G _{X (ref} _ _sat, ï _ref) ί _ref - R _mt ^V _ref _ ^ mt sat ref ^ _ ^ mt sat ^(X ref sat _ ^ ^X ^ ref _ sat m2 ^X 0 _ sat

- {Gi (x _ref _ _sat, i _ref) i _ref) = R _mt A _r ef _ sat ⁺ M _mt dA _ref _ _sat I dt + K _mt (x _{ref sat} _) v _{ref sat} + K _m2 v ₀ _ n · _\ m _{/ ■} 1 · dL _e (x _sat, I _ref)

with G _l (x _{ref sat} , i _ref ) = B1 (x _{ref sat} , i _ref ) --i _ref ^J - ^J -.

In addition, the control device 22 comprises a unit 80 for estimating the resistance R _e of the loudspeaker. This unit 80 receives as input the reference dynamic quantities G _reI , the intensity of the reference currents i _reI and its derivative di _reI / dt and, according to the embodiment envisaged, the temperature measured on the magnetic circuit of the loudspeaker denoted T _{m mY} urea Or the measured intensity through the coil denoted I mesurée-

In the absence of a measurement of the circulating current, the estimation unit 80 is of the form illustrated in FIG. 7. It comprises as input a module 82 for calculating the power and parameters and a thermal model 84.

The thermal model 84 calculates the resistance R _e from the calculated parameters, the determined power P _JB and the measured temperature.

Tm_mesurée-

Figure 8 gives the general diagram used for the thermal model.

In this model, the reference temperature is the internal air temperature of the enclosure T _e .

 The temperatures considered are:

T _b [° C]: winding temperature;

T _m [° C]: temperature of the magnetic circuit; and

T _e [° C]: internal temperature of the enclosure assumed to be constant or, ideally, measured.

 The thermal power considered is:

Pj _b [W]: thermal power supplied to the winding by Joule effect;

 The thermal model comprises, as illustrated in FIG. 8, the following parameters:

 Ctbb [J / K]: thermal capacity of the winding;

 R, hbm [K / W]: equivalent thermal resistance between the winding and the magnetic circuit; and

Rt _hb a [K / W]: equivalent thermal resistance between the winding and the internal temperature of the enclosure; The equivalent thermal resistances take into account the heat dissipation by conduction and convection.

The thermal power P _Jb provided by the current flowing in the winding is given by:

P _Jb {t) = R _e {T _b ) i ² {t)

where R _e (T _b ) is the value of the electrical resistance at temperature T _b :

R _e (T _b ) = R _e (20 ° C) X (1 + 4.10 ^"3 (T _b - 20 ° C))

where R _e (20 ° C) is the value of the electrical resistance at 20 ° C. The thermal model given in FIG. 8 is as follows:

^C thb ~~~ = ~ ΐτ: ( ^T m ~ ^T b) ⁺ ~ \ ( ^T e ~ ^T b) ^{+ P} Jb

^{did K} thbm \ ^A ref I ^K thba V ref I

Its resolution makes it possible to obtain the value of the resistance R _e at each instant.

As a variant, as illustrated in FIG. 9, when the current i flowing in the coil is measured, the estimate of the resistance R _e is provided by a closed-loop estimator, for example of integral proportional type. This makes it possible to have a fast convergence time thanks to the use of an integral proportional corrector.

Finally, the controller 22 comprises a unit 90 for calculating the reference output voltage L, from the dynamic quantities of G _ref reference i _ref reference current and its derivative di _ref / dt, electrical parameters P _e iec and the resistance R _e calculated by the unit 80. This unit for calculating the reference output voltage implements the following two equations:

L ₂ ( ^X _re f 'Kef) of ₂ _ _{J (} . ^ Ref

R ₂ (x _ref, i _ref) dt dt di _ref dL _e (x _ref,,)

U '= ^R = ef + (Xref' Kef) - + '2 + ^Bl ( ^X ref Kef ref + Kef ~ V ref

As a variant, and for an enclosure comprising an enclosure open through a vent, the mechanical-acoustic modeling of the loudspeaker illustrated in FIG. 5 is replaced by the modeling of FIG. 11 and the structural adaptation unit. 25 is suitable for determining the desired acceleration of the speaker diaphragm A _ref from the desired acceleration of the air γ ₀ to take account of the particular structure of the enclosure.

In this embodiment, and as illustrated in FIG. 3, the control module 22 receives as input the audio signal S _aU dio ref to be reproduced from the desired model 20. The unit 24 for applying a unit conversion gain, depending on the peak voltage of the amplifier 10 and a variable attenuation between 0 and 1 controlled by the user, ensures the passage of the signal. audio reference S _in dio_re _f to a signal γ ₀ image of a physical quantity to be reproduced. The signal γ ₀ is, for example, an acceleration of the air opposite the loudspeaker or a speed of the air to be displaced by the loudspeaker 14. In the following, it is assumed that the signal γ ₀ is the acceleration of the air set in motion by the enclosure.

The structural adaptation unit 25 of the signal to be reproduced as a function of the structure of the enclosure in which the loudspeaker is used is able to provide a reference variable A _ref desired at each instant for the speaker diaphragm. from a corresponding quantity for the movement of the air set in motion by the device in which the loudspeaker is placed.

Thus, in the example considered, the reference variable A _ref , calculated from the acceleration of the air to be reproduced γ ₀ is the acceleration to be reproduced for the speaker diaphragm so that the operation of the loudspeaker speaker imposes on the total air an acceleration γ ₀ .

FIG. 10 shows a detail of the structural adaptation unit 25. The input γ ₀ is connected to a bounded integration unit 127 whose output is itself connected to another bounded integration unit 128 .

Thus, at the output of the units 127 and 128 are respectively obtained the first integral v ₀ and the second integral x ₀ of the acceleration γ ₀ .

The bounded integration units are formed of a first-order low-pass filter and are characterized by a cut-off frequency F ₀ BF-

The use of bounded integration units allows the quantities used in the control device 22 to be the derivatives or the integrals of each other only in the useful bandwidth, ie for the higher frequencies. at the cut-off frequency F ₀ BF- This makes it possible to control the excursion at low frequency of the quantities considered.

In normal operation, the cut-off frequency F _0BF is chosen so as not to influence the signal at the low frequencies of the useful bandwidth.

The cutoff frequency F _OB F is taken less than one-tenth of the frequency f _min of the desired model 20.

In the case of a vent enclosure in which the loudspeaker is mounted, the unit 25 produces the desired reference acceleration for the membrane A _ref by the following relation:

 With:

R _m2 : coefficient of acoustic leakage of the enclosure;

M _m2 : inductance equivalent to the air mass in the vent;

K _m2 : stiffness of the air in the enclosure.

x ₀ : position of the total air displaced by the membrane and the vent

VQ = ÷: speed of the total air displaced by the membrane and the vent

In this case, the desired reference acceleration for the membrane A _ref is corrected for structural dynamic quantities x ₀ , v ₀ of the enclosure, the latter being different from the dynamic variables relating to the speaker membrane.

This reference quantity A _ref is introduced into a calculation unit 26 of dynamic reference quantities capable of supplying, at each instant, the value of the derivative with respect to the time of the reference variable denoted dA _ref / dt as well as the values first and second integrals with respect to the time of this reference quantity respectively denoted V _ref and X _ref .

The set of reference dynamic quantities is noted in the following G _ref .

The structural adaptation unit 25 also comprises within it a calculation unit identical to 26 in order to determine the reference dynamic variables v ₀ and x ₀ .

 The computing unit 26 is illustrated in FIG. 4 and is that of the previous embodiment.

As before, the tables 36 and 38 are adapted to define, as a function of the dynamic reference values G _ref received at the input, the electromechanical parameters P _mec and electrical P _e i _ec respectively. These parameters P _Meca and P _é i _ec are obtained respectively from a mechanical modeling of the loudspeaker as illustrated in Figure 1 1, where the speaker is assumed installed in a vent enclosure, and of an electrical model of the loudspeaker as shown in FIG.

The electromechanical parameters P _mec include the magnetic flux captured by the coil noted B1 produced by the magnetic circuit of the HP, the stiffness of the speaker noted K _mt (x _D ), the viscous mechanical friction of the speaker noted R _mt , the mobile mass of the entire loudspeaker noted M _mt , the stiffness of the air in the enclosure noted K _m2 , the acoustic leakage of the enclosure rated R _m2 ^and ' ^a mass of air in the vent noted M _m2 .

The last three quantities that are integrated in P _Meca are not shown in Figure 3. The modeling of the mechanico-acoustic part of the loudspeaker placed in a vent enclosure illustrated in FIG. 11 comprises, in a single closed loop circuit, a voltage generator 140 BI (x _D , i) .i corresponding to the driving force produced by the current flowing in the coil of the loudspeaker. The magnetic flux BI (x _D , i) depends on the position x _D of the membrane as well as the intensity i flowing in the coil.

This modeling takes into account the viscous mechanical friction R _mt of the membrane corresponding to a resistor 142 in series with a coil 144 corresponding to the overall moving mass M _mt of the membrane, the stiffness of the membrane corresponding to a capacitor 146 of capacitance C _mt (x _D ) equals 1 / K _mt (x _D ). Thus, the stiffness depends on the position x _D of the membrane.

To account for the vent, the following parameters R _m2 , C _m2 and M _m2 are used:

R _m2 '■ coefficient of acoustic leakage of the enclosure;

M _m2 : inductance equivalent to the air mass in the vent;

cm2 = - ^' ■ compliance of the air in the enclosure.

 In the modeling of FIG. 11, they respectively correspond to a resistor 147, a coil 148 and a capacitor 149 connected in parallel.

 In this model, the force resulting from the reluctance of the magnetic circuit is neglected.

 The variables used are:

v = ^ _D: membrane the speed of the speaker γ ° ^{= _'acc} élération of the loudspeaker membrane

v _L : air speed of air leaks

v _p : speed the air leaving the vent (port)

v ₀ = ^ = v _D + v _L + v _P : speed of the total air displaced by the membrane and the vent γ ₀ = ^: acceleration of the total air displaced.

The total sound pressure at 1 meter is given by: p = - ^ - γ ₀

n _str n.

where S _D : loudspeaker cross-section, n _str = 2: solid emission angle.

 The mechanical-acoustic equation corresponding to FIG. 11 is the following:

Bl (x _D , i) i = M _mt + K _m2 Xo

The following relation links the different quantities: γ ₀ = γ _Ό - v ₀ - - ^ ²² - x ₀

 Rm2 Mm2

The modeling of the electrical part of the loudspeaker is illustrated in FIG. 6 and is identical to that of the first embodiment. From the modelizations explained with regard to FIGS. 1 1 and 6, the following equations are defined: u _e = R + L _e (x _D , i) ^ - + R ₂ (i - i ₂ ) + B 1 (x _D , i) v _D + i ^dLe ^ ^{D, l} _D

Lll ll v y g (x _D, i)

 di

L ₂ ^ 2- = R (i - i ₂ )

 dt

 dv

Bl (x _D , i) i = R _mt v _D + MD

mt D) ^■ ¾

 dt

The control module 22 further comprises a unit 70 for calculating the reference current i _re f and its derivative di _re f _/ dt. This unit receives as input the reference dynamic quantities G _ref, the mechanical parameters P _m ACR and quantities x ₀ and v _0. This calculation of the reference current U and its derivative dU _/ dt satisfy both equations:

G ref ef ^' ^ ref = ^R m _t ^V ref + ^M mAef + ^K' m ( ^X r ₄ ) ^X ref + ^K m2 ^X 0

 d_

fa (x _ref. f) f) = tf + M _mt dA dt I _ref + K _mt (x _ref) v _ref + K v _{0 m2}

dt with G, (x _ref , i _ref ) = B1 (x _ref , i _ref

Thus, the current i _re f and its derivative di _re f _/ dt are obtained by an algebraic calculation from the values of the vectors entered by an exact analytical calculation or a numerical resolution if necessary according to the complexity of Gi (x, i ).

The derivative of the current di _{ref /} dt is thus preferably obtained by an algebraic calculation or else by digital derivation.

To avoid excessive displacement of the speaker diaphragm, a displacement X _max is imposed on the control module as in the previous embodiment.

In addition, the control device 22 comprises a unit 80 for estimating the resistance R _e of the loudspeaker as described in the prior embodiment.

In the case where the amplifier 16 is an amplifier in current and not in voltage as previously described, the units 38, 80 and 90 of the control device are suppressed and the reference output intensity i _re controlling the amplifier is taken out of the unit 70.

In the case of an enclosure comprising a passive radiator formed of a membrane, the mechanical model of FIG. 6 is replaced by that of FIG. 12 in which the elements identical to those of FIG. 6 bear the same reference numerals. This module comprises in series with the coil M _m2 48, corresponding to the mass of the passive radiator membrane, a resistor 202 and a capacitor 204 of value ^c m3 = - respectively corresponding to the mechanical losses R _m2 of the passive radiator and the stiffness mechanical K _m3 of the passive radiator membrane. The reference acceleration of the membrane A _ref is given by:

^A ref - Yo + p ^V 0 M ^X ° ^R

^M m2 km2

With x _0R given by filtering by a high-pass filter of x ₀ :

s ²

2 i "m3, ^Λ τη3

+ M _m2 ^{S +} M _m2

Thus, the structural adaptation structure 25 will comprise in series two bounded integrators for obtaining v ₀ and x ₀ from γ ₀ , then the calculation of x 0 _R starting from x ₀ by high-pass filtering with the parameters additional R _m3 and K _m3 respectively, the mechanical loss resistance and the mechanical stiffness constant of the passive radiator membrane.

Claims

1. - Device for controlling a loudspeaker (14) in an enclosure comprising: - an input for an audio signal (S _aU dio_ref) to reproduce; - an output for supplying a loudspeaker excitation signal; characterized in that it includes a command comprising: - means (24, 25) for calculating a desired dynamic quantity (A _ref ) of the loudspeaker membrane as a function of the audio signal (S _aU dio_ref) to be reproduced and the structure of the enclosure; - means (26) for calculating, at each instant, a plurality of desired dynamic quantities (A _ref , dA _ref/ dt, V _ref , X _re f) of the loudspeaker membrane as a function of the single quantity desired dynamic (A _ref ); - a mechanical modeling (36) of the speaker; And - means (70, 80, 90) for calculating, at each instant, the excitation signal, without feedback loop, from the mechanical modeling (36) of the loudspeaker and the desired dynamic quantities (A _ref , dA _ref/ dt, V _ref , X _re f) - 2. - Device for controlling a loudspeaker (14) according to claim 1, characterized in that said control further comprises an electrical modeling (38) of the loudspeaker, and the means (70, 80, 90) to calculate, at each moment, the excitation signal, are able to calculate the excitation signal in addition as a function of the electrical modeling (38) of the loudspeaker. 3. - Device for controlling a loudspeaker (14) according to claim 2, characterized in that the electrical modeling (38) of the loudspeaker takes into account: - a resistance (R ₂ ) representative of the magnetic losses of the loudspeaker; - an inductance (L ₂ ) representative of a para-inductance resulting from the effect of eddy currents in the loudspeaker. 4. - Device for controlling a loudspeaker (14) according to claim 2 or 3, characterized in that the electrical modeling (38) of the loudspeaker takes into account the variation of the inductance (L _e ) of the loudspeaker coil as a function of the intensity (i) flowing through the loudspeaker. 5. - Device for controlling a loudspeaker (14) according to any one of claims 2 to 4, characterized in that the electrical modeling (38) of the loudspeaker takes into account the variation of the inductance ( The _e ) of the speaker coil as a function of the position (x) of the coil diaphragm. 6.- Device for controlling a loudspeaker (14) according to any one of claims 2 to 5, characterized in that the electrical modeling (38) of the loudspeaker loudspeaker takes into account the variation of the magnetic flux captured (Bl) by the loudspeaker coil as a function of the intensity (i) circulating in the loudspeaker. 7. - Device for controlling a loudspeaker (14) according to any one of claims 2 to 6, characterized in that the electrical modeling (38) of the loudspeaker takes into account the variation of the magnetic flux captured ( Bl) by the speaker coil as a function of the position (x) of the coil membrane. 8. - Device for controlling a loudspeaker (14) according to any one of claims 2 to 7, characterized in that the electrical modeling (38) of the loudspeaker takes into account the variation of the derivative of the 'inductance versus time of the loudspeaker coil (g(x,i)) as a function of the intensity (i) flowing through the loudspeaker. 9. - Device for controlling a loudspeaker (14) according to any one of claims 2 to 8, characterized in that the electrical modeling (38) of the loudspeaker takes into account the variation of the derivative of the The inductance versus time of the speaker coil (g(x,i)) as a function of the position (x) of the coil diaphragm. 10. - Device for controlling a loudspeaker (14) according to any one of claims 2 to 9, characterized in that the electrical modeling (38) of the loudspeaker takes into account the variation of the resistance (R _e ) of the loudspeaker coil as a function of a temperature (T _m measured) measured from the magnetic circuit of the loudspeaker. 1 1.- Device for controlling a loudspeaker (14) according to any one of claims 2 to 9, characterized in that the electrical modeling (38) of the loudspeaker takes into account the variation of the resistance ( R _e ) of the loudspeaker coil as a function of an intensity (I measured) measured in the loudspeaker coil. 12.- Device for controlling a loudspeaker (14) according to any one of the preceding claims, characterized in that the means (26) for calculating the desired dynamic quantities (A _ref , dA _ref/ dt, V _{ref , _ OB} F) - 13.- Device for controlling a loudspeaker (14) according to any one of the preceding claims, characterized in that the plurality of desired dynamic quantities (A _ref , dA _ref/ dt, V _ref , X _re f) is the set of values at a given time of four functions which are derivatives of different orders of the same function. 14.- Device for controlling a loudspeaker (14) according to any one of the preceding claims, characterized in that the means (26) for calculating desired dynamic quantities (A _ref , dA _ref/ dt, V _ref , X _re f) are suitable for ensuring calculations desired dynamic quantities by integration and/or derivation of the audio signal to be reproduced (A _ref ). 15. - Device for controlling a loudspeaker (14) according to any one of the preceding claims, characterized in that the means (70, 80, 90) for calculating the excitation signal, without feedback loop, from the desired _dynamic quantities (A _ref , dA _{ref/ dt} , V _ref , relation to time of the desired current intensity in the coil. 16. - Device for controlling a loudspeaker (14) according to any one of the preceding claims, characterized in that the mechanical modeling (36) of the loudspeaker takes into account the mechanical friction (R _mt ) of the top -speaker and in that it includes means so that the resistance (R _mt ) depends on at least one of the desired dynamic quantities (A _ref , dA _ref/ dt, V _ref , X _re following a non-linear increasing function tending towards infinity when at least one of the desired dynamic quantities (A _ref , dA _ref/ dt, V _ref , X _ref ) tends towards a predetermined value (X _max ). 17. - Device for controlling a loudspeaker (14) according to any one of the preceding claims, characterized in that the plurality of desired dynamic quantities (A _ref , dA _ref/ dt, V _ref , X _ref ) comprise the acceleration of the loudspeaker membrane (A _ref ) and the position (X _ref ) of the loudspeaker membrane and in that it comprises means for limiting the acceleration (A _ref ) in a predetermined interval , to limit excursions of the position (X _ref ) of the membrane beyond a predetermined value 18. - Device for controlling a loudspeaker (14) according to any one of the preceding claims, characterized in that the means (25) for calculating the dynamic quantity (A _ref ) of the loudspeaker membrane are suitable for applying a different correction of the identity, and taking into account structural dynamic quantities (x ₀ , v ₀ ) of the enclosure different from the dynamic quantities relating to the loudspeaker membrane. 19. - Device according to claim 18, characterized in that the enclosure comprises a vent and the structural dynamic quantities (x ₀ , v ₀ ) of the enclosure comprise at least one derivative of predetermined order of the position of the air displaced by the enclosure. 20. - Device according to claim 18 or 19, characterized in that the structural dynamic quantities (x ₀ , v ₀ ) of the enclosure include the position of the air (x ₀ ) displaced by the enclosure. 21. - Device according to any one of claims 1 8 to 20, characterized in that the structural dynamic quantities (x ₀ , v ₀ ) of the enclosure include the speed (v ₀ ) of the air displaced by the enclosure. 22. - Device according to any one of the preceding claims, characterized in that the enclosure is a vent enclosure and the structural dynamic quantities (x ₀ , v ₀ ) of the enclosure depend on at least one of the following parameters : - acoustic leakage coefficient of the enclosure (R _m2 ) - inductance equivalent to the mass of air in the vent (M _m2 ) - compliance of the air in the enclosure {C _m2 =— ). 23. - Device according to any one of the preceding claims, characterized in that the enclosure is an enclosure with a passive radiator and the structural dynamic quantities (x ₀ , v ₀ ) of the enclosure depend on at least one of the parameters following: - acoustic leakage coefficient of the enclosure (R _m2 ) - inductance equivalent to the mass of the membrane of the passive radiator (M _m2 ) - compliance of the air in the enclosure {C _m2 =—) - mechanical losses of the passive radiator (ff _m3 ) - mechanical compliance of the membrane (C _m3 =—).