EP0508392A2 - Montage de circuit pour la correcteur des caractéristiques de transfert linéaires et non-linéaires de transducteurs électroacoustiques - Google Patents

Montage de circuit pour la correcteur des caractéristiques de transfert linéaires et non-linéaires de transducteurs électroacoustiques Download PDF

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EP0508392A2
EP0508392A2 EP92106049A EP92106049A EP0508392A2 EP 0508392 A2 EP0508392 A2 EP 0508392A2 EP 92106049 A EP92106049 A EP 92106049A EP 92106049 A EP92106049 A EP 92106049A EP 0508392 A2 EP0508392 A2 EP 0508392A2
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linear
input
port
output
signal
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German (de)
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EP0508392A3 (en
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Wolfgang Dr. Klippel
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Harman Professional Inc
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JBL Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/002—Damping circuit arrangements for transducers, e.g. motional feedback circuits
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/02—Circuits for transducers, loudspeakers or microphones for preventing acoustic reaction, i.e. acoustic oscillatory feedback
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/04—Circuits for transducers, loudspeakers or microphones for correcting frequency response
    • H04R3/08—Circuits for transducers, loudspeakers or microphones for correcting frequency response of electromagnetic transducers

Definitions

  • the invention relates to an arrangement for correcting the linear and non-linear transmission behavior of electroacoustic transducers, consisting of an electroacoustic transducer, an electrical equalizer network coupled to the electrical input terminals and an aid for adapting the equalizer network to the transducer.
  • the electrical network has a non-linear transmission behavior and changes the electrical signal in such a way that the non-linear effects of the network and the coupled converter are compensated for. In this way, an overall system with reduced nonlinear distortion and improved linear transmission behavior can be implemented.
  • the parameters of the electrical network can be changed and independently adapted to the specific transmission behavior of the converter.
  • the negative feedback has the advantage that the exact structure of the nonlinear transmission system does not have to be known and that the functionality is retained when the nonlinearity (aging) changes.
  • the required signal pickups are expensive, susceptible and have a specific transmission behavior that must be compensated for by suitable equalizer networks.
  • the danger of a possible positive feedback requires measures to correct the phase response ([1] Hall, DS: Design Considerations for an Accelerometer-Based Dynamic Loudspeaker Motional Feedback System. 87. Audio Eng. Soc. Conv, New York October 1989 (Preprint 2863)) . All these problems prevent the negative feedback on electroacoustic sound transmitters from becoming widely accepted.
  • the VOLTERRA series development offers a possible starting point for modeling the non-linear converter. It is a very advantageous hand tool for describing second and third order distortions of weakly nonlinear systems with very small input signals. In the case of stronger non-linearities, the system can no longer be described by quadratic and cubic subsystems, and other elements of the VOLTERRA series must be taken into account. In order to achieve convergence, the input signal must always be sufficiently small and limited according to the Weierstrass criterion. This theory was first applied to the converter by ([2] Kaizer, A.J .: Modeling of the Nonlinear Response of an Electrodynamic Loudspeaker by a Volterra Series Expansion. J. Audio Eng. Soc. 35 (1987) 6, p. 421).
  • This arrangement has a consistently additive structure corresponding to the series properties of the VOLTERRA development.
  • the individual branches represent higher order linear, quadratic, cubic or nonlinear networks and compensate for the corresponding distortion products.
  • this concept only insufficiently takes into account the transducer-specific features and, in practical implementation, requires a restriction to square and cubic correction systems.
  • the converter no longer behaves like an ideal quadratic or cubic system with a larger input signal and the inevitable incorrect compensation leads instead to a reduction in an increase in the distortion in the transmission signal.
  • the insertion of higher order compensation elements extends the usable modulation range, but does not fundamentally solve the problem and leads to technically hardly realizable equalization systems.
  • the additive parallel structure of the equalizer network which inevitably results from the VOLTERRA modeling, leads to a universal but complex circuit structure, which has decisive disadvantages in large signal behavior.
  • the object of the invention is, for the first time, to create an equalizer network without constant signal feedback (motional feed back), which completely , automatically (independently) compensates for the nonlinear distortions in the small and large signal range (up to the maximum power loss or in the entire deflection range of the voice coil) allows the specific peculiarities (non-linear causes of distortion) of the respective electroacoustic transducer to be better taken into account and implemented with less effort.
  • the electroacoustic sound transducer is described by an electro-mechano-acoustic equivalent circuit diagram.
  • the structural components of the converter that are essential for signal transmission are functionally combined in concentrated active elements, each of which is characterized by a parameter (for example damping, rigidity of the suspension, electrodynamic coupling factor B1, etc.).
  • a parameter for example damping, rigidity of the suspension, electrodynamic coupling factor B1, etc.
  • all other elements of the transducer system are subject to temporal parameter changes. The changes caused by aging, fatigue and warming prove to be long-term processes that change the linear transmission properties of the converter, but do not cause non-linear signal distortions.
  • the transmission behavior is fully described with a non-linear integro differential equation (IDG), from which the associated equalizer transfer function is derived by conversion and transferred directly into the circuit structure of the equalizer network.
  • IDG non-linear integro differential equation
  • the electromechanical equivalent circuit diagram (FIG. 7a) can be transferred with the aid of the associated nonlinear IDG into an equivalent signal flow diagram (FIG. 7b) which consists of a nonlinear transmission system (152) and a subsequent linear transmission system (153).
  • the linear subsystem (153) is composed of an electro-mechanical system (144) with the transfer function X (s) and a downstream mechano-acoustic system with the transfer function H (s).
  • the non-linear system (152) connected upstream of the linear transmission system (153) causes the disturbing, non-linear signal distortions.
  • the nonlinear system (152) contains nonlinear, dynamic transmission systems (two-port 147-151) and a linear transmission system (two-port 167), which also has the transfer function X (s) and further linking elements (139-143, 145).
  • the linear and non-linear transmission systems have one input and one signal output, the logic elements have two signal inputs and one signal output.
  • the output of each transmission system is connected to the one input of a logic element. Both parts are referred to below as a three port. Each three port represents exactly one non-linear cause of distortion.
  • the three gates which represent the deflection-dependent induction, the deflection-dependent damping, the electromagnetic drive and the deflection-dependent stiffness, contain adders (139, 141, 142, 143) as logic elements.
  • the deflection-dependent, electrodynamic drive leads to a multiplicative one Linking element (140).
  • the three port which describes the Doppler distortions, contains a variable delay element (145) as the link element.
  • All three gates are interconnected in a certain structure.
  • the output of the preceding logic element is linked to an input of the next logic element and leads to a chaining of all three-port gates contained.
  • the three-port (147,139) which describes electrical induction, comes first, followed by the three-port of the electrodynamic force factor (148, 140) and the three-port, which are connected to the electromagnetic drive (150, 142), the non-linear damping (141 , 149) and the stiffness (143, 151) correspond.
  • the last position immediately in front of the linear subsystem (145, 146) is the three port (145, 167), which corresponds to the generation of the Doppler distortions in the acoustic system.
  • the inputs of all non-linear subsystems and of the linear transmission system (167) are connected to the signal input of the delay element (145).
  • the transmission systems (147-151) are thus fed back without feedback via a signal feedback and the three port of the Doppler distortions.
  • the well-known large signal effects (amplitude compression, phase shift of the fundamental oscillation and the distortion products) result from the signal feedback in the electromechanical converter part.
  • the Doppler distortions caused by the Dreitor (145, 167) do not influence the mechanical vibration behavior (deflection of the membrane) and thus the process of creating the nonlinear distortions.
  • the non-linear transmission system (152) Due to the different supply of the transmission systems (retroactive, non-reactive), the non-linear transmission system (152) consists of two non-linear subsystems connected in series.
  • this nonlinear transmission system (152) ie the occurrence of disturbing nonlinear distortions in the output signal, can be completely compensated for by a very specific equalization system, that of the sound transmitter upstream:
  • this goal is achieved in that the equalization system the transmission elements S L (166), S B (165), S D (164), S M (163), S S (162) and X (s) (161 ) contains, which correspond to the nonlinear and linear transmission systems of the converter (147 - 151, 167) in their transmission behavior.
  • Each of these transmission elements is connected to a logic element that has exactly the inverse properties of the logic element in the corresponding converter driver, ie instead of the adders (139, 141-143), subtractors (156-158, 160) result instead of the multiplier (140) Division element (159) and the controllable delay element (145) leads to a delay element with the opposite control characteristic.
  • the connection of the transmission link and associated link element is referred to below as a three port.
  • All three gates in the equalizer network are connected in a chain in exactly the right order (in relation to the input terminals of the converter) using one of their inputs and their outputs.
  • the input of all transmission elements (two-port 161-166), i.e. the other input of the three-port is connected to the output of the delay element.
  • the three-port of the Doppler distortions in the converter signal flow diagram (145, 167) fed without feedback corresponds to an equalizer three-way (155, 161) which has a signal feedback.
  • the other three-port electromechanical gates, which were connected via a signal feedback in the converter signal flow diagram, correspond to three-port gates in the equalizer network that are switched without feedback.
  • the equalizer network thus also consists of two non-linear subsystems connected in series.
  • the equalizer network consists of a chain connection (series connection) of transmission elements, with at least one transmission element (two-port) having a non-linear transmission behavior between its input and output ports.
  • a chain connection of the transmission links of the equalization network means that the links are mutually linked with their input and output and are thus switched on in the transmission chain (sound receiver, signal memory, transmitter, receiver, amplifier, sound transmitter).
  • Each of these nonlinear transmission elements (two-port Z1, Z2, Z3) is a memoryless (frequency-independent) or dynamic (frequency-dependent) system.
  • Each dynamic, non-linear two-port Z contains at least one transmission three (see FIG. 2), which corresponds to a non-linear cause of distortion in the converter and serves to compensate for the corresponding non-linear distortions.
  • Each three-port D is a dynamic, non-linear one Transmission link with two signal inputs E1, E2 and an output A (see. Fig. 3). It consists of a non-linear, dynamic transmission element (two-port U) and a memory-less logic element V, which converts the two input signals into the output signal via an algebraic operation (eg addition, multiplication).
  • One input E1 of the Dreitor D is connected directly to one input of the logic element, the other input E2 of the Dreitor (D) is connected via the two-port U to the second input of the logic element and the output of the logic element is connected to the output of the Dreitor ( D) coupled.
  • the two-port U takes into account the physical properties of the variable converter parameter and its position in the active structure of the converter. If several transmission three gates are arranged between the input and output of the two gates (Z) (Fig. 2), these are connected in a chain connection using the respective input gate E 1 (18) and the output gate A (20) and the remaining input gate E 2 ( 19) of the three gates contained either connected to the input gate of the two-port Z (FIG. 2 a) or to the output port of the two-port Z (FIG. 2 b).
  • All dynamic, non-linear transmission elements are composed of dynamic, linear two-port and / or memoryless, non-linear two-port N and / or logic elements (e.g. adders, multipliers).
  • the free, variable parameters of the dynamic, linear two-port (linear filter parameters) and the memoryless, non-linear two-port (non-linear characteristics) are measured by measuring the resulting transmission behavior (converter with equalization network), with the help of a matching arrangement, which is temporary or permanent to the converter equalizer System is connected, determined and so the equalization system is automatically adapted to the respective converter.
  • the equalizer network will initially be further specified for the electrodynamic sound transmitter, which is operated in a bass reflex or compact box system.
  • the non-linear integro differential equation (IDG) is set up, the equalizer transfer function is determined and implemented in a circuit arrangement.
  • the non-linear equivalent circuit diagram (see FIG. 7 a) differs from the linear one in that current and deflection-dependent parameters or quantities occur.
  • the following nonlinear equation (IDQ) can be set up in the time domain from the equivalent circuit diagram when fed with a constant current source
  • the deflection-equivalent time signal x (t) which acts here as a control variable, can be implemented by a linear transmission element (low pass) with the following transfer function be replicated.
  • the electrodynamic converter system with a constant current source does, however, require more effort in the area of the power amplifier by inserting a voltage-current converter and requires additional measures to ensure a balanced sound pressure amplitude frequency response, but simplifies the non-linear equalization.
  • the predistorted input signal is expediently converted into a current signal only at the power amplifier.
  • the deflection-equivalent time signal x (t) can be carried out using a linear system (low pass) with the following transfer function from the undistorted input signal u (t) and the current i L (t) using the linear transfer function be determined.
  • the circuits of the equalizer for current and voltage supply can be derived directly from the non-linear transfer functions (5), (12).
  • the point operations contained correspond to multiplications in the time domain.
  • the convolution with a constant weight function corresponds to a linear system (filter) connected in the transmission path.
  • the nonlinear functions are realized by memoryless, nonlinear two gates.
  • the equalizer network contains a three-port D S (FIG. 9), which consists of a more linear, dynamic network X (100), a memoryless, non-linear two-port N S (101) and an adder (103) consists.
  • the input E2 (22) of the three-way monitor is connected to the input of the two-port X.
  • the output of the two-port X which carries a deflection-equivalent signal, is connected to the input of an adder via the memoryless, non-linear two-port N S.
  • the second input of the adder is connected to the input E1 and the output of the adder and the output A of the Dreitor D S are interconnected.
  • the equalizer network contains a three port D B (FIG. 10), which consists of a more linear, dynamic network X, a memoryless, non-linear two port N B (104) and a multiplier (105).
  • D B consists of a more linear, dynamic network X, a memoryless, non-linear two port N B (104) and a multiplier (105).
  • the input E2 of the Dreitor is connected in series via the linear two-port X and the memoryless, non-linear two-port N B to the input of the multiplier.
  • the second input of the multiplier is connected to the input E 1 and the output of the multiplier is connected to the output A of the Dreitor D S.
  • the equalizer network contains a three-port D D (FIG. 11), which consists of a more linear, dynamic network X, a differentiator (108), a memoryless, non-linear two-port N D (106) and an adder - And multiplier (103, 107).
  • the input E2 of the three-way monitor is connected via the two-port X to both the memoryless, non-linear two-port N D and the input of a differentiator.
  • the outputs of the differentiator and the memoryless, non-linear two-port N D are linked together via a multiplier and connected to the input of an adder.
  • the second input of the adder is connected to the input E 1 and output of the adder and the output A of the three-phase D D.
  • the equalizer network contains a three port D M , which consists of a linear, dynamic network X, a memoryless, non-linear two port N M (110), a square (108), a multiplier (109), and an adder (103) exists.
  • the input E2 of the three-way monitor is connected to sound transmitters that are fed via a constant current source (FIG. 13), both directly to the input of the squaring stage and via the two-port X to the input of the memory-free, non-linear two-port N M.
  • the outputs of the squarer and the two-port N M are linked via a multiplier and fed to the input of an adder.
  • the second input of the adder is connected to the input E 1 and the output of the adder is connected to the output A of the Dreitor D M.
  • the input signal of the squaring stage which corresponds to the input current of the converter, is generated with the aid of a non-linear network (111) according to relationship (13).
  • the deflection-equivalent signal at the output of the two-port X is fed both to a linear two-port with the transfer function I (s) and to the non-linear, non-linear two-port N S , N B.
  • the output of the linear two-port I and the output of the two-port N S are combined in an adder and fed to one input of a multiplier.
  • the other input of the multiplier is connected to the output of the non-linear two-port N B.
  • the output of the multiplier carries the input current equivalent signal.
  • the equalizer network contains a three-port network D L (FIG. 14), which consists of a more linear, dynamic network X, a non-linear network (111), a differentiator (112) and a non-linear two-port N L (110 ) and a multiplier (109) and adder (103).
  • the input E2 of the three-way connector is connected via the linear two-port X to the non-linear two-port N L.
  • the output of the two-port N L and the output of the current simulation (111) described above are connected to the inputs of the multiplier.
  • the output signal is fed to one input of an adder via a differentiator.
  • the second input of the adder is connected to the input E 1 and the output of the adder is connected to the output A of the Dreitor D L.
  • the compensation three-way gates In the case of simultaneous compensation of the electrodynamic drive and other converter parameters, the compensation three-way gates must be connected to one of their two inputs and the output in a chain such that, apart from the three-port D L of inductance compensation, all other three-port sides are connected to the three-port D B on the input side (FIG. 4 ).
  • the output of the compensation third-party D L must always be connected to the transducer inputs of the sound transmitter.
  • This circuitry arrangement of the compensation three-way gate results directly from the analytical structure of the transfer function (large curly brackets in 5 and 12 respectively) and corresponds to the mirror symmetry between Equalizer structure (signal flow diagram in Fig. 20 a) and the active structure (signal flow diagram 7 b) of the nonlinear physical mechanisms in the electrodynamic loudspeaker. Only in this order can the distortions caused by the deflection of the voice coil be fully compensated.
  • the deflection of the membrane changes not only the electrical and mechanical parameters of the transducer, but also the acoustic radiation conditions, i.e. the distance between the current membrane position and a fixed reception point in the main radiation direction (axis) depends on the deflection and leads to a different transit time of the signal in the acoustic system.
  • high-frequency signal components with short wavelengths are impaired by the resulting phase or frequency modulation (known as the Doppler effect) and generate additional intermodulation distortions ([5] GL Beers and H.Belar, "Frequency-Modulation Distortion in Loudspeakers", J. Audio Eng. Soc ., Volume 29, pages 320-326, May 1981).
  • this distortion mechanism is also modeled and the required transfer function of the equalization network is derived and the required circuit structure is determined.
  • the constant acoustic impulse response h o (t) can be separated from the variable transit time, which results from the quotient of deflection x (t) and speed of sound c.
  • the transfer function of the equalizer (24) can be implemented in terms of circuitry with the aid of a transfer element with a variable, controllable transit time.
  • a control-equivalent signal x (t) is required for control.
  • This signal can be obtained from the electrical signal u L (t) using a linear filter with the transfer function X (s).
  • this correction network Considering this correction network as a three-port D T , whose input E1 (21) is fed with the signal u (t) and whose output A (25) to Converters leads, the control input E2 (22) is connected to the output A.
  • the compensation network for Doppler distortions is one of the retroactive, feedback circuit structures (see FIG. 2 b).
  • the resulting overall equalization network thus consists of a chain connection of two nonlinear, dynamic transmission links (see two gates Z1 and Z2 in FIG.
  • the control input E2 (22) of this three port is connected to the input of the linear filter (100), which has the transfer function X (s) and at whose output a deflection-equivalent signal x (t) is produced.
  • the input E1 (21) is connected to the input of a delay element (138), at the output of which the input signal appears after 20 ⁇ s delay without further distortion.
  • a delay element 138
  • the instantaneous signal x (t) is interpolated between the instantaneous and the delayed signal.
  • the sound flow passes through a cross-sectional jump, so that a pressure chamber is created between the vibrating membrane and the funnel entrance.
  • the parameters of the acoustic elements friction in the funnel entrance K and compliance of the pressure chamber D are dependent on acoustic state variables. With a very large sound flow q K , the flow at the funnel entrance is no longer laminar. The formation of turbulence creates, in addition to viscous friction, further losses which lead to an increase in the overall friction parameter (flow resistance).
  • the second non-linear mechanism is caused by the (adiabatic) compression of the air in the pressure chamber.
  • the resilience of the enclosed air volume V decreases with increasing pressure p D in the chamber and can be described by the following relationship If all acoustic and mechanical elements are transformed to the electrical side, an equivalent electrical equivalent circuit (FIG. 8) can be specified.
  • the linear elements of the mechano-acoustic system are in the complex impedance summarized.
  • control signal u K (t) can be carried out by a linear system with the following transfer function be replicated.
  • N A (i D ) N (i D ) ⁇ I D , (39)
  • the non-linear transfer function of the equalizer can be converted directly into a circuit.
  • the convolution operations are carried out by linear filters with the transfer functions Y (s), F (s), Z (s), W (s) and the non-linear functions N A and N R are implemented by memoryless, non-linear transfer systems.
  • the signals are linked in accordance with the algebraic structure of the equalizer function (32) with adders and multipliers.
  • the input E 2 of the three-port D A is via a transmission element (115) connected to the input of a memoryless, non-linear transmission element N A (114).
  • the output of the two-port N A is connected via the linear transfer two-port W (113) to the first input of an adder (103) and the second input of the adder is connected to the input E 1 of the three-way monitor.
  • the output of the adder being connected together to the output A of the D Dreitors A.
  • the input E2 of the Dreitor D R is via a linear, dynamic transmission element Y (118) connected to the input of a memoryless, non-linear transmission element N R (119).
  • the output of the two-port N R is connected via the linear transmission element F (120) to the first input of an adder (103) and the second input of the adder is connected to the input E 1 of the three-way monitor.
  • the output of the adder is connected to the output A of the three-phase D R.
  • the circuit can compromise the accuracy of the compensation be greatly simplified in certain frequency areas.
  • the electrodynamic sound receiver (microphone) also generates non-linear signal distortions when there is high sound pressure in the lower frequency range.
  • the physical background is first explained using a model of the electrodynamic sensor with concentrated electrical and mechanical elements, and then the equalizer network is derived.
  • stiffness of the membrane suspension s T (x) and the stiffness of the coupled air volume s B (x) are summarized in a constant overall stiffness s o and in a deflection-dependent overall stiffness s G (x).
  • s O + s G (X) s T (x) + s B (x) (48)
  • the amplifier connected to the sensor should have a sufficiently high internal resistance so that the resistance and inductance of the voice coil can be neglected.
  • the force F is the input variable of the transducer and the voice coil deflection x acts as a parameter-changing state variable.
  • the nonlinear equalizer network must do the following transfer function in the time domain with the abbreviations and have.
  • the frequency-independent, non-linear functions result from the dependent parameters of the sensor where the auxiliary function N U (x) of the relationship enough.
  • the non-linear transfer function of the equalizer can be converted directly into a circuit.
  • This circuit is a chain connection of two non-linear, dynamic two-port Z2 and Z3.
  • the two-port Z2 which immediately follows the sound receiver, contains the three-port D BE for compensation of the electrodynamic coupling factor.
  • the second two-port connected to the output of the three-way D BE contains the three-way to compensate for the deflection-dependent damping and the rigidity.
  • the three port D BE (FIG. 19) compensates for the coupling parameter which is variable in terms of deflection.
  • the input E2 of the Dreitor is connected in series via an integrating element (129), a serially coupled memoryless, non-linear transmission element N BE (130) to the one input of a multiplier (131).
  • the input E 1 is connected to the second multiplier input and the output of the multiplier is connected to the output A of the rotator D BE .
  • the three-port D SE (FIG. 17) effects a desired change or compensation of the stiffness of the diaphragm suspension which is variable in terms of deflection.
  • the input E2 of the Dreitor D SE is connected via an integrating element (123), a memoryless, non-linear transmission element N SE (122) and a linear two-port Q (121) to the one input of an adder (103).
  • the second input of the adder is connected to the input E 1 and the output of the adder is connected to the output A of the Dreitor D SE .
  • the Dreitor D DE (Fig. 18) effects a desired change or compensation of the stiffness of the diaphragm suspension which is variable in terms of deflection.
  • the input E2 of the Dreitor D DE is connected both directly to the one input of a multiplier (107) and via the chain connection of an integrating element (126) and a memory-free, non-linear transmission element N DE (128) to the second input of the multiplier.
  • the output of the multiplier is connected via a linear two-port Q (121) to the input of an adder, the second input of the adder is connected to the input E 1 and the output of the adder is connected to the output A of the three-phase D DE .
  • the non-linear signal distortion is caused by the action of one constant parallel capacitance C p , through the deflection-dependent electrical attraction between the membrane and counterelectrode and through the deflection-dependent compliance of the air cushion or the membrane.
  • the membrane with the area S M converts the sound pressure signal p m (t) into a force signal F (t), which acts on the overall compliance in the frequency range of interest.
  • a polarization voltage U o is built up between the membrane and the counter electrode of the electrostatic sensor and the input resistance of the coupled amplifier is so high that no charges can flow off at the signal frequencies of interest.
  • a second constant parallel capacitance C p acts in addition to the capacitance C o between the membrane and counterelectrode, which is controlled by the deflection of the membrane.
  • the entire system should be linearized and the following linear Transfer function be fulfilled.
  • the nonlinear equalizer network must have the following transfer function in the time domain.
  • the equalizer network is frequency-independent and corresponds to a simple, memory-free, non-linear two-port.
  • the equalizer network has changeable properties, ie the parameters of the equalizer network, in particular the non-linear, memoryless two-ports, can be changed via at least one control input.
  • the control lines of the parameter control there are aids for storing the set control value (holding circuits) in order to retain the determined parameter setting even after the adjustment process has ended.
  • a further circuit-technical aid is activated to adapt the network. It consists of a generation part for generating an excitation signal and an analysis part for recording and evaluating a measurement signal and for generating control signals for setting the equalizer parameters.
  • the adapter arrangement can be designed as a control circuit or as a control circuit.
  • a separate adaptation is possible in the control circuit, in which the converter is initially connected to the measuring arrangement to form a measuring chain without an equalizer network, and the nonlinear converter parameters are determined and stored in the holding circuits. After measuring the converter parameters, the equalizer network is coupled to the converter again and the outputs of the holding circuits are connected to the control inputs of the equalizer network.
  • a simultaneous adaptation appears to be more advantageous, in which the generation part is connected to the transducer-equalizer system and the analysis part to form an electrode.
  • the output of the analysis section is connected to the control input of the equalization network, so that the control signals generated in the analysis section change the parameters of the equalization network and adapt the system to the converter.
  • a main control system takes over the control and control of the subsystems during the adjustment process.
  • the generation part is connected to the input terminals of the converter via the equalizer network.
  • the measurement signal can be derived via an impedance measurement or via an acoustic measurement.
  • the acoustic measurement requires an additional sound receiver, but reduces the technical effort in the subsequent analysis section.
  • the overall arrangement can be adapted to the transmission behavior of the two-port X by means of the three-port damping and stiffness compensation. As a result, the adaptation effort can be reduced and, at the same time, a desired linear overall transmission behavior can be realized.
  • the individual distortion components are separated from the recorded measurement signal (microphone signal) with a spectral or correlation analysis and the control signals are derived.
  • the excitation signal is conducted via non-linear, dynamic two-ports, which synthetically simulate the non-linear causes of distortion of the converter and separate individual distortion components.
  • the frequency and phase position of the reference signals, but not their amplitude, is important for the correlation analysis.
  • the measurement signal and a reference signal are fed to the two inputs of the correlator.
  • the correlator consists of a multiplier and a downstream low-pass filter.
  • the correlation signal is used directly to control the equalizer network.
  • the adaptation process is carried out with various signal modulations in order to achieve the best possible match and ultimately compensation in the small and large signal range.
  • the optimal equalizer parameters intended for lower modulation can be adopted and only the curve sections relevant for the extended modulation range can be changed.
  • the converter equalizer system In the event that the converter equalizer system has reached its modulation limits and, for example, the deflection of the voice coil or the power supplied and converted into heat can destroy the converter, it is advisable to arrange a non-linear, dynamic two-port Z SS in the equalizer network.
  • the two-port Z SS has the same structure as the other non-linear equalizer blocks. It contains non-linear, dynamic three-port D SS for modulation limitation and for power limitation.
  • a controllable, non-linear network H switched which has, for example, a high-pass characteristic.
  • the input E2 is connected via a linear network O, via a memoryless, non-linear two-port N O and via a further linear two-port B to the control input of the two-port H.
  • the linear two-port O has the transfer function X (s) and generates a deflection-equivalent signal.
  • the non-linear two-port N O is a rectifier and the downstream two-port has a low-pass characteristic.
  • the linear two-port O has a transfer function derived from the electrical input impedance.
  • the non-linear two-port N O contains a squarer and the subsequent linear two-port B is an integrator, the integration time of which corresponds to the heating-up time (determined by thermal capacity and thermal conductivity) of the converter.
  • a change in the linear transmission properties of the two-port H prevents the converter from being destroyed or the generation of non-linear distortions when the modulation limit (max. Deflection, max. Power loss) is reached.
  • the network contains a linear low-pass filter (34) of second order X (s), a differentiator s (36), three memoryless, non-linear two-ports N S (35), N B (38), N D (37) and three multipliers (33 , 28, 95) and two adding stages (29, 30).
  • the input of the adder (30) and the input of the low pass X (34) are connected to the input (31) of the equalizer network.
  • the output of the low-pass filter X (34) which carries a deflection-equivalent signal, is connected both to all inputs of the memoryless, non-linear two-ports (35, 37, 38) and the differentiating element (36) and to one input of the multiplier (95) .
  • the second The input of the multiplier (95) is linked to the output of the non-linear two-port N S (35).
  • the output of the multiplier (95) is superimposed in the adder (30) with the undistorted signal.
  • the output of the differentiating element (36) and the output of the non-linear two-port N D (37) are connected to the inputs of the multiplier (33).
  • the output of the multiplier is linked to the predistorted signal via the adder (29) and is fed to one input of the multiplier (28).
  • the second input of the multiplier (28) is connected to the output of the memoryless two-port N B (38).
  • the output of the multiplier (28) is connected to the loudspeaker via an amplifier (7) with constant current supply.
  • the linear network is constructed as an active RC filter.
  • the quality and the resonance frequency of the second order low-pass filter X (s) is determined in accordance with the desired linear transmission behavior.
  • the overall system can be corrected for the required linear properties for any loudspeaker with different resonance frequency and quality.
  • the correspondence between the low-pass function X (s) and the linear transmission behavior of the overall arrangement is a necessary prerequisite for the functionality of the nonlinear equalizer.
  • the loudspeaker Since in the present example the loudspeaker has no stiffness and damping non-linearities, only constant values are stored in the two gates N S (35) and N D (37).
  • the non-linear characteristic of the memoryless two-port N B (38) must, however, be adapted to the converter.
  • a hold circuit (48, 49, 50, 51, 42) is connected to the control inputs of the amplifiers and stores the optimally set control voltage after the adaptation process.
  • the control voltage of the linear (49, 60) and cubic branches (51, 58, 62) change the asymmetry of the characteristic. If the gain in the even-order potentiometers (61, 63) is increased, the symmetrical changes in the characteristic curve increase.
  • the control lines of the even and odd systems are each connected to a changeover switch (44, 45, 46) which are switched simultaneously by the main control unit (89) via the relay (43).
  • the rotors of the changeover switches lead to the constant (39), symmetrical (41) and asymmetrical (40) correction inputs.
  • the changeable non-linear "two-port" also contains a control line (42) with which the changeover switch can be switched and various operating points can be selected in the characteristic curves.
  • the coefficients of the linear (49) and quadratic (50) elements are optimized in the lowest operating point.
  • the order of the Taylor series approach or the number of parallel branches in the memoryless, non-linear two-port determines the number of additional operating points. They are appropriately distributed over the further modulation range of the converter.
  • the generating part (75) consists of two signal generators (65, 66) which generate a sinusoidal tone near the resonance frequency and a second higher-frequency tone. Both signals are added in an adder stage (67) and output to the equalizer network (1) via the switch (87) via a voltage-controlled amplifier (91).
  • the main control unit (89) establishes this connection via the relay (88) during the adaptation process and switches back to the normal signal input (93) after adaptation.
  • the equalizer network (1) is connected to the converter via a DC voltage-transmitting amplifier (7) (2) connected.
  • a microphone (3) is used to measure the sound pressure in the vicinity of the loudspeaker during the adjustment process and the electrical microphone signal is fed to the analysis part (76).
  • the analysis part contains a correlator for each parameter to be adjusted, which was implemented with the aid of a multiplier (77, 78, 79, 80) and a downstream free pass (81, 82, 83, 84).
  • the microphone signal is routed to one input of the correlator and a reference signal derived from the excitation signal to the other input.
  • the amplitude of the reference signals is arbitrary and has no information value. However, the frequency and phase position of the reference signals correspond to the basic tones, harmonics or intermodulations in the microphone signal.
  • the reference signal R (f1) and R (f2) at the multipliers (77, 78) is obtained by linear filtering (68, 89) with the transfer function X (s) of the linear two-port of the equalizer circuit from the excitation signal.
  • the reference signal R (f 1) is linked in the correlator (77, 81) with the microphone signal, then passed through a differentiator (85) to the control input (39) of the memory-free, non-linear two-port stiffness compensation.
  • the reference signal R (f2) is fed to the correlator (78, 82) and its output is connected to the control input (39) of the damping compensation via a differentiating element (86).
  • Both control signals change the constant portion of the memoryless, non-linear two gates N S and N D so that the linear transmission behavior (resonance frequency and quality) of the equalizer network converter system matches the transmission behavior X (s) and the output signal at the integrators ( 81) and (82) becomes maximum.
  • the reference signals R (f1 + f2) and R (2 ⁇ f1 + f2) are synthetically generated in an electronic replica of the nonlinear converter.
  • This network is a circuit implementation of the modeling of the transmission behavior with the VOLTERRA series.
  • the signals f 1 and f 2 are passed through linear filters X (68, 89), multiplied together in (72) and filtered again with the linear transfer function of the converter (74).
  • the reference signal R (f 1 + f 2) obtained in this way corresponds in phase and frequency to the intermodulations which are generated by asymmetries in the characteristic curve of the electrodynamic coupling factor ([6] Klippel, W.: Dynamic Measurement of Non-Linear Parameters of Electrodynamical Loudspeakers and their Interpretation 88. Conv. Of the Audio Eng. Soc., March 1990, preprint 2903).
  • the signal f1 is additionally squared before multiplication.
  • the output signal of the multiplier (71) is also subjected to linear filtering (74) with the transfer function X.
  • the reference signal R (f1 + f2) is linked in the correlator (79, 83) with the microphone signal, then fed to the unbalanced control input (40) of the memory-free, non-linear two-port drive compensation N B.
  • the reference signal R (2 ⁇ f1 + f2) is fed to the correlator (80, 84) and its output signal is connected to the symmetrical control input (41) of the memoryless, non-linear two-port N B of the drive compensation.
  • the characteristic curve is changed by both control signals so that the second and third order intermodulation products in the received measurement signal are reduced and the output signal of the integrators (83) and (84) runs towards zero.
  • the sign of the correlation signal indicates over- or under-compensation by the equalizer network and leads to a decrease or increase in the voltage in the subsequent holding circuits (48, 49, 50, 51, 52) of the non-linearity without memory.
  • the main control system (89) connects the equalizer input (31) to the generating part (75), switches on the lowest excitation voltage via the voltage-controlled amplifier (91) and starts the adaptation the constant of the two-port N D , N S and determines the optimal voltage value in the holding circuit (48).
  • the coefficients of the linear and quadratic branches are changed in the two-port N B and optimal voltages in the holding circuits (49, 50) are determined.
  • the main control system (89) switches on the two higher coefficients of the Taylor development in N B with the switches (44, 45), increases the excitation voltage and determines the optimum value for the holding circuits (51, 52).
  • the constant parameters in the two-port N S and N D ie the values in the holding circuits (48), are no longer changed.
  • the main control system switches off the generating part (75) and connects the equalizer input (31) to the general signal input (93).
  • the advantages achieved with the invention consist in particular in realizing simple equalizer networks which largely take into account the converter-specific features and require a minimal number of components.
  • the problem of adapting the equalizer network to the converter was solved with the aid of a further circuit arrangement.
  • the adjustment system which is activated at times, enables the optimum equalizer parameters to be determined and set independently.
  • both a desired change in the linear properties and a reduction in the non-linear distortions can be achieved over the entire modulation range of the converter.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Electromagnetism (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Amplifiers (AREA)
EP19920106049 1991-04-09 1992-04-07 Circuit arrangement for correcting linear and non-linear transfer characteristics of electroacustic transducers Withdrawn EP0508392A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4111884A DE4111884A1 (de) 1991-04-09 1991-04-09 Schaltungsanordnung zur korrektur des linearen und nichtlinearen uebertragungsverhaltens elektroakustischer wandler
DE4111884 1991-04-09

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EP0508392A2 true EP0508392A2 (fr) 1992-10-14
EP0508392A3 EP0508392A3 (en) 1993-12-15

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EP (1) EP0508392A3 (fr)
DE (1) DE4111884A1 (fr)

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GB2292854A (en) * 1994-08-12 1996-03-06 Motorola Ltd Control of audio output using motional feedback and ambient noise detection
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DE19931387B4 (de) * 1999-07-07 2004-02-05 Innomar Technologie Gmbh Verfahren und Anordnung mit parametrischer Sendung zur Echolotung des Bodens, von Sedimentschichten und von Objekten am und im Boden sowie zur Unterwassernachrichtenübertragung
WO2008018099A1 (fr) * 2006-08-10 2008-02-14 Claudio Lastrucci améliorations sur des systèmes pour une diffusion acoustique
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EP2092787A2 (fr) * 2006-10-18 2009-08-26 DTS, Inc. Système et procédé pour compenser une distorsion non linéaire, sans mémoire, d'un transducteur audio
EP2092787A4 (fr) * 2006-10-18 2011-01-26 Dts Inc Système et procédé pour compenser une distorsion non linéaire, sans mémoire, d'un transducteur audio
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WO2009007322A2 (fr) * 2007-07-11 2009-01-15 Austriamicrosystems Ag Dispositif de reproduction et procédé de calibrage d'un dispositif de reproduction
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DE102014101881B4 (de) 2014-02-14 2023-07-27 Intel Corporation Audioausgabeeinrichtung und Verfahren zum Bestimmen eines Lautsprecherkegelhubs

Also Published As

Publication number Publication date
EP0508392A3 (en) 1993-12-15
US5438625A (en) 1995-08-01
DE4111884A1 (de) 1992-10-15
DE4111884C2 (fr) 1993-09-02

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