Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS
  • H04R3/00—Circuits for transducers
  • H04R3/04—Circuits for transducers for correcting frequency response
  • H04R3/08—Circuits for transducers for correcting frequency response of electromagnetic transducers

Definitions

• the present invention relates to a device and a method for filtering the resonant peak in a supply circuit of at least one loudspeaker, the filtering device being disposed upstream of said at least one loudspeaker.
• a conventional loudspeaker comprises an electromagnetic actuator, most often composed of a coil disposed on a moving element within a magnetic field generated by a permanent magnet.
• the audible frequency induced mechanical displacement is transformed into an acoustic field by means of a membrane acting as an emitting surface, also called an acoustic radiator.
• the sound quality of the loudspeaker depends on the frequency response curve, that is to say a mechanical response in acceleration to an electrical stress either current or voltage, which one seeks the most constant possible on the overall bandwidth.
• the sound quality also depends on the linearity of the device marked by the presence of a minimum of harmonic distortions and intermodulations.
• the useful motive force at the origin of the displacement of the moving element results from the interaction of the magnetic induction field, denoted B, with each element of length of the coil traversed by a current noted i ( t) function of a time t.
• B the magnetic induction field
• i ( t) the elementary force applied to a load carrier moving within an induction field
• Lorentz force the elementary force applied to a load carrier moving within an induction field
• a balance sheet within a basic volume carrying charges subject to the phenomenon leads to the expression:
• This force modulated by the intensity, solicits the mobile equipment whose mechanical behavior is dictated by three components: a force of inertia, product of the mass of moving parts noted M m by the imposed acceleration, a force of damping, generally considered proportional to the speed of movement via a constant denoted f m in newton / m / s or kg / s and a restoring force linked to the suspension mechanism with a stiffness denoted k m in N / m.
• the current-voltage relationship across the loudspeaker is governed by its structure characterized by the moving equipment moving within a magnetic field.
• the electrical behavior is dictated by two mechanisms, namely the Joule effect dissipation related to the Ohm's law and the electromagnetic interactions in terms of induced electromotive forces, underpinned by three contributions:
• R e is the pure resistive component of the winding, which can vary with the temperature measured in Ohms and L e is its own inductance function of the displacement measured in Henry when nonlinearities are taken into account.
• L e is its own inductance function of the displacement measured in Henry when nonlinearities are taken into account.
• the current voltage transduction is provided by a specifically arranged signal conditioner, the transducer being biased by the output current of this conditioner.
• This control is comparable to an ideal Norton generator on the transducer: the latter then represents a load solicited under infinite impedance, on which any fluctuation of f.e.m. generated by the charge has no effect on the behavior of the association. More preferably, this voltage can be measured and then used as a correction signal in a servo strategy.
• control by voltage command directly solicits the speakers, given a subject electric behavior the constituent parameters of its impedance. It is only relatively recently that various works have been carried out for the design of specifically-driven loudspeakers, taking into account adequate conditioners.
• the three quantities Bl, R e , L e previously mentioned basically determine the reproduction quality of the conditioning and transducer association.
• the interactions will not be the same depending on the choice made by the designer among the two modes of current and voltage control.
• Equation (2) can be written in the frequency domain by:
• Equations (2) and (3) can be considered in the frequency domain in the harmonic regime and combined with each other in terms of cascaded transfer functions. Noting E 0 and l 0 the decoupled complex quantities of their evolutionary part, the index being significant of a particular angular frequency also called "phasors" in English, one obtains:
• a specific electrical coefficient Q e can therefore be defined by making f m close to zero and a simple relation coupling the resonance factors can then be written:
• Transducer impedance combines an exclusively electrical component with a second component called motional impedance.
• Z HP Z e + Z m with:
• the motional impedance is affected by a characteristic second-order polynomial that marks band-pass behavior.
• the use designates the nominal value of the impedance by a given value, often 4W and 8W for the power transducers, 16W and 32W for the mini and microsystems equipping the helmets, the contribution of the emotional impedance n is in no case negligible, when the transducer must be stressed in tension.
• the inductive reactance component j.L.w gradually attenuates the reproduction of the signals.
• this document proposes to combine a current command and an acceleration servo for the frequency range covering all the mechanical resonances of the loudspeaker. This solution has however never given satisfaction, a servocontrolled acceleration could not compensate for all the mechanical resonances specific to each speaker.
• Document GB-A-2 473 921 discloses in its introductory part that the sound quality of electrodynamic loudspeakers can be significantly improved by supplying a loudspeaker with current control instead of voltage control. frequently adopted.
• the current control is obtained when the impedance of the source seen by the pilot is high compared to the own impedance of the driver.
• This document therefore proposes a control of the loudspeaker with a double coil used together with an impedance which deactivates one of the coils acoustically at high frequencies, which produces the correction of the required response while maintaining a relatively high impedance of the source.
• the aim of the present invention is, for any category of loudspeaker, to correct at least the presence of a resonance peak during a driving current of the loudspeaker, this by electronic means and without specific adaptation of the current control of the speaker which remains unchanged from that of the state of the art.
• the invention relates to a circuit for supplying acoustic signals to at least one loudspeaker, this circuit comprising a resonance peak filtering device occurring at a certain frequency of the supply current of the at least one a loudspeaker and at least two non-inverter converters arranged in series upstream of said at least one loudspeaker, each of the two converters having a positive power supply terminal and a negative power supply terminal and an output, the most upstream of the two converters having its positive power supply terminal connected to the input power supply of the circuit while its output is connected by an intermediate circuit to the positive power supply terminal of the second converter, the output of the second converter being connected at least one builder, characterized in that the filtering device of the resonant peak of said at least one builder is incorporated in a first branch bypassing the intermediate circuit between said at least two converters, this filtering device being purely electrical in the form of an impedance connected, on the one hand, to a point of the intermediate circuit and, on the other hand, to an instrument
• the technical effect is to be able to use current control with the aforementioned advantages while obscuring at least the major disadvantage of current steering which is the formation of a resonance peak not compensated by a current control contrary to a voltage control.
• the first inductance is virtual by being formed of. two non-inverting auxiliary converters arranged in series, each of the two auxiliary converters having a positive power supply terminal and a negative power supply terminal and an output, the most upstream of the two auxiliary converters having its connected positive power supply terminal at the output of the first capacitor while the output of this upstream auxiliary converter is connected by a first intermediate auxiliary circuit to the positive supply terminal of the second auxiliary converter, the first intermediate auxiliary circuit having an auxiliary capacitor and being connected in branching to an instrumentation ground auxiliary circuit having a first auxiliary resistor, the output of the second auxiliary converter being connected to the first auxiliary converter by a second auxiliary circuit having a second auxiliary resistor, each auxiliary converter feeling his own feedback loop connecting its output to its negative supply terminal.
• a virtual inductor is particularly advantageous because it can be easily modified without changing the elements that compose it but only in their interaction and / or operation.
• Such a virtual inductor has the great advantage of easy adaptation to the operating conditions of said at least one loudspeaker, in particular but not only for monitoring a variation in the frequency of the resonance peak due for example to a variation of temperature of said at least one loudspeaker or against overheating of said at least one loudspeaker.
• the first virtual inductance is equal to the product of the first and second auxiliary resistors and the auxiliary capacitor.
• the first resistance and the second auxiliary resistance derive from each other a total resistance according to the equation:
• R 3 R 03 - R A
• a second capacitor is disposed in a second branch bypassing the intermediate circuit between the at least two converters, this second capacitor being associated with a second resistor, the parameters of the second resistor and the second capacitor being predetermined for the attenuation of the capacitors. high frequency signals.
• the intermediate circuit between the two non-inverting converters comprises a third resistor disposed between the output of the most upstream non-inverting converter and the first branch branch of the intermediate circuit incorporating the filtering device.
• the value of said at least one first resistor is equal to 0, the values of said at least one first capacitor and said at least one first inductance are equal to 0.29 ⁇ F, respectively. and 2.28 H, the values of the first auxiliary resistor and the second auxiliary resistor being respectively equal to 1200 Ohm and 400 Ohm, the value of the third resistor being equal to 3000 Ohm.
• each non-inverting converter has its own feedback loop connecting its output to its negative power supply terminal, each of the feedback loops being mounted, for the most upstream converter, as a bypass of the intermediate circuit between the two non-inverter converters. and, for the most downstream converter, bypassing an instrumentation ground circuit disposed after said at least one loudspeaker, the instrumentation ground circuit having a fourth resistor.
• the invention also relates to a method for controlling the electrical power supply of acoustic signals of at least one loudspeaker, the power supply incorporating such a resonance peak filtering device, in which method it is carried out step of correcting the resonance peak by the filtering device, this step being upstream of said at least one loudspeaker.
• the overall resonance factor of the loudspeaker and the filtering device takes the value of a Butterworth filter.
• said at least one loudspeaker comprises a diaphragm
• the resonance peak is simultaneously filtered at a reduction in the acoustic level in the highest frequencies in the direction of the perpendicular axis of the diaphragm of said at least one loud speaker.
• the temperature variations of said at least one loudspeaker are taken into account by the filtering device by variation in correspondence of the impedance parameters of said device.
• the filtering device in particular the inductance which can be a virtual inductor.
• the temperature of said at least one loudspeaker that can be measured or estimated is automatically done by respective modification of the various elements that form the virtual inductor, for example but not limited to auxiliary converters.
• FIG. 1 illustrates a schematic representation of an acoustic signal supply circuit of at least one loudspeaker, this circuit being provided with a resonance peak filtering device according to one embodiment of the present invention.
• FIG. 2 illustrates an embodiment of the filtering device of the acoustic signal supply circuit shown in FIG. 1, for which the inductance of the filtering device is in the form of a virtual inductor, the virtual inductor. being shown enlarged in this figure with respect to FIG.
• FIG. 3 illustrates for the embodiment shown in FIG. 2, the impedance comprising a virtual inductor
• FIG. 4 illustrates the acceleration modules during a current control with or without resonance peak filtering as well as during a voltage control of a loudspeaker, the filtering being carried out with a device of FIG. filtering according to the embodiment of the invention
• FIG. 5 illustrates curves of degrees of angle as a function of frequencies, the filtering taking place with a filtering device according to the embodiment of the invention shown in FIG. 1.
• an ideal current control solution would seek to find a filtering mode for filtering the two previously mentioned effects, namely the resonance peak and the directivity effect of the speaker without altering the index.
• current control also known as CDI.
• the present invention proposes a passive correction solution upstream of said at least one loudspeaker.
• the invention therefore relates to a method for controlling the current of the electrical power supply with acoustic signals from at least one loudspeaker, the power supply incorporating a resonance peak filtering device, in which a step is performed. resonant peak correction by the filtering device, this step being upstream of said at least one speaker.
• the resonance peak is simultaneously filtered at a reduction in the acoustic level in the highest frequencies in the direction of the perpendicular axis of the diaphragm of said at least one speaker.
• this reduction is ensured by a resistance and capacitor system branched into the main circuit as will be developed later.
• the overall resonance factor of the loudspeaker and the filtering device takes the value of a Butterworth filter, which will also be developed later.
• the acoustic signal supply circuit of at least one HP loudspeaker has a resonance peak filtering device.
• the circuit also comprises at least two non-inverting converters A, A 0 arranged in series upstream of said at least one HP loudspeaker, each of the two converters A, A 0 having a positive power supply terminal and a negative power supply terminal. as well as an exit.
• the upstream A of the two converters A, A 0 has its positive supply terminal connected to the input power supply of the circuit while its output is connected by an intermediate circuit to the positive supply terminal of the second converter A 0 .
• the output of the second converter A 0 is connected to said at least one speaker HP, a resonance peak occurring at a certain frequency of the supply current of said at least one speaker HP.
• the essential characteristic of the circuit is that the resonant peak filtering device of said at least one speaker HP is incorporated in a first branch branch of the intermediate circuit between said at least two converters A, A0.
• This filtering device is purely electric and is in the form of an impedance Z 3 connected, on the one hand, to a point of the intermediate circuit and, on the other hand, to an instrumentation mass.
• the impedance Z 3 is called RLC comprising at least a first resistor R 3 , at least a first capacitor C 3 and at least a first inductance L 3 arranged in series.
• the parameters of the first resistor R3, the first capacitor C3 and the first inductor L 3 are predetermined according to the resonance peak filtering from said at least one loudspeaker HP.
• the first inductance L 3 is virtual, that is to say that the first inductance L 3 may for example be formed of a system of active circuits acting as inductance.
• a correction envisaged is predefined to the first order and a filtering solution upstream of said at least one HP loudspeaker, also called under the English name of "feedforward correction", can therefore be developed with medium power components, the currents remaining below 50mA, replacing the inductance by the system of active circuits.
• the fundamental advantage of the filtering arrangement upstream of the voltage current converter appears in the low values of the intensity involved in the filtering operation, thus allowing the use of numerous references. of very low noise operational amplifier components to form the virtual inductor. High-performance filtering devices with low noise and no copper winding can therefore be developed.
• this embodiment with a virtual inductance can make it possible to self-adapt the filtering device during operation to correct any drift related to. a possible change in the environment of the HP speaker. This may result in particular automatic compensation of the offset of the resonant frequency due to heating of the speaker HP.
• the approach then participates in a feedback loop coupling with the electrical control upstream of the filtering device.
• the active circuit system is formed of two auxiliary converters ⁇ 1/2 , A 2/2 non inverters arranged in series.
• Each of the two auxiliary converters A 1/2 , A2 / 2 has a positive power supply terminal and a negative power supply terminal and an output.
• the upstream A 1/2 of the two auxiliary converters A 1/2 , A 2/2 has its positive supply terminal connected to the output of the first capacitor C 3 while the output of this auxiliary converter upstream A 1/2 is connected by a first intermediate auxiliary circuit to the positive supply terminal of the second auxiliary converter A 2/2 .
• the first intermediate auxiliary circuit comprises an auxiliary capacitor C A and is connected in shunt to an auxiliary instrumentation ground circuit having a first auxiliary resistor R B.
• the output of the second auxiliary converter A 2/2 is connected to the first auxiliary converter A 1/2 by a second auxiliary circuit having a second auxiliary resistor R A , each auxiliary converter A 1/2 , A 2/2 having its own loop. back connecting its output to its negative power terminal.
• the elements of the impedance Z 3 satisfy a compromise between a minimum noise and currents maintained at low values, for example a current intensity in the impedance Z 3 of less than 5 mA.
• the first virtual inductance L 3 may advantageously be equal to the product of the first R B and second R A auxiliary resistors and the auxiliary capacitor C A.
• a second capacitor C h may be disposed in a second branch in branch of the intermediate circuit between the at least two converters A, A 0 .
• This second capacitor C h is associated with a second resistor R h, the parameters of the second resistor R h and the second capacitor C h being predetermined to reduce the high-frequency signals with an own actual time R p .C h.
• the second resistor R h and the capacitance of the second capacitor C h may be respectively R h ⁇ 1 ⁇ and C h ⁇ 4.7 nF. This is however purely indicative.
• the intermediate circuit between the two non-inverting converters A, A 0 comprises a third resistor R p disposed between the output of the non-inverter converter A most upstream and the first branch branch of the intermediate circuit incorporating the filtering device.
• each non-inverting converter A, A 0 has its own feedback loop connecting its output to its negative power supply terminal, each of the feedback loops being mounted, for the most upstream converter A, in shunt of the intermediate circuit between the two non-inverting converters A, A 0 and, for the most downstream converter A 0 , in derivation of an instrumentation earth circuit arranged after the loudspeaker HP, the instrumentation mass circuit comprising a fourth resistance R B1
• V 3 and V 1 be the voltages as indicated in FIG. 1, V 3 being the voltage between the branch point of the first branch of the resonant peak filtering device with respect to the intermediate circuit and a ground of instrumentation and V 1 being the voltage between the output of the first auxiliary converter A upstream and an instrumentation mass, a conventional calculation makes it possible to obtain the transfer function V 3 / V 1 of the filter constituted by the series connection of R p and the network R 3 L 3 C 3 series is:
• the filtering performed possibly combined with the high-frequency attenuation by the filter R h , C h, makes it possible to retain only the current voltage conditioner function assigned to the power amplifier and outputting on said at least one high-wagerer.
• HP The specificity of this conformation lies in the virtual constitution of the inductance L 3 using two active components. In fact, considering the impedance presented by the assembly R A , R B. C a , A, A 0 , the following two relationships can be combined:
• the arrangement of the chosen parameters makes it possible not to have to mount this component, the series value of R A having almost the required value to ensure the desired attenuation, 1 / Q m , as mentioned in equations (9) and (10). ). Indeed, if:
• FIG. 4 illustrates the modulus curves of the acceleration for current control with or without resonance peak filtering as well as the acceleration module for voltage control of the at least one speaker, the filtering performing with a filtering device according to the embodiment of the invention illustrated in Figures 1 to 3.
• the uncontrolled current control curve is that with rectangles, the current control curve with filtering is with circles and the voltage control curve is that with lozenges.
• the intermediate curve with rectangles is the curve with current control and filtering with a filtering device according to the first embodiment and shows the absence of a resonance peak unlike the upper curve with current control without filtering.
• this intermediate curve has a substantially constant acceleration modulus range wider than that of the lower curve which is the curve with voltage control with diamonds.
• FIG. 5 illustrates the angle degree curves as a function of the frequencies, the filtering taking place with a filtering device according to the embodiment of the invention shown in FIGS. 1 to 3, for the speaker phase or HP defined by the curve bearing rectangles and for phase V 3 ./V 1 defined by the curve bearing circles.
• the curves of FIG. 5 show that the phase shift angle remains in a range of perfectly acceptable values over the frequency domain considered.
• moderate capacitance values of the order of the microfarad permit the implementation of polypropylene MKP capacitors, which capacitors are well suited to transient conditions.
• At least one non-inverting converter has been used in the circuit, in order to simplify the calculations. This is not limiting and the present invention can however also apply for a circuit comprising one or more inverters.

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• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Circuit For Audible Band Transducer (AREA)

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• 2014
  • 2014-03-05 FR FR1400581A patent/FR3018419B1/fr active Active
• 2015
  • 2015-03-03 JP JP2016554730A patent/JP6452207B2/ja not_active Expired - Fee Related
  • 2015-03-03 WO PCT/FR2015/000049 patent/WO2015140421A1/fr not_active Ceased
  • 2015-03-03 EP EP15714246.4A patent/EP3114856A1/de not_active Withdrawn
  • 2015-03-03 US US15/127,851 patent/US10271139B2/en not_active Expired - Fee Related
  • 2015-03-03 CN CN201580011366.1A patent/CN106063294A/zh active Pending

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