Speaker output characteristic correction system and sound system

Abstract

The present invention addresses the problem of providing a "speaker output characteristic correction system and sound system" which correct the output characteristic of a speaker to a target output characteristic with high accuracy. [Solution] A control filter (61) convolves a sound source output signal u (n) with a reverse transmission characteristic G-that is a transmission characteristic of a sound pressure level at a predetermined sound reception point (M) and a target transmission characteristic H that is a target sound pressure level, and outputs the convolved sound source output signal through an amplifier (4). The speaker (2) is provided with a sensor (3) for detecting the displacement of the vibration system. A transfer characteristic setting unit (62) sets a reverse transfer characteristic G-in accordance with each parameter of an equivalent circuit of the speaker (2) determined on the basis of the detected displacement. Thereafter, the transmission characteristic setting unit (62) periodically determines a change in the parameter on the basis of the detected displacement, and updates the inverse transmission characteristic G-so as to match the determined changed parameter.

Description

Technical Field

[0001] The present invention relates to a technique for correcting the output characteristics of a speaker. Background Art

[0002] As a technique for correcting the output characteristics of a speaker, an audio reproduction device is known. An experiment is performed in advance in which a microphone is arranged at the sound receiving position and the transfer characteristics from the speaker to the sound receiving position are estimated. And during actual use, the inverse characteristics of the transfer characteristics estimated by the experiment and the required transfer characteristics are convolved with the audio signal and output to the speaker, so that the output characteristics of the speaker become desired characteristics (for example, Patent Document 1).

[0003] In addition, as a technique related to the present application, the following technique is known: A sensor for detecting the displacement of the vibration system of a speaker is provided, and each parameter of the equivalent circuit of the speaker is estimated or updated based on the response of the displacement detected by the sensor for a test signal output to the speaker (for example, Patent Document 2).

[0004] Prior Art Documents:

[0005] Patent Documents:

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2010-21982

[0007] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2023-125746 Summary of the Invention

[0008] Problems to be Solved by the Invention:

[0009] In the case of speakers such as a woofer or a subwoofer whose main function is to reproduce in the low frequency range, generally, in order to increase the fundamental sound pressure level in the output low frequency range, it is necessary to increase the diameter of the speaker.

[0010] However, increasing the diameter of the speaker is accompanied by an increase in size, weight, and cost, so sometimes it is not possible to apply the increase in diameter.

[0011] Therefore, instead of increasing the diameter of the speaker, it is also considered to apply the above technique of convolving the inverse characteristics of the transfer characteristics from the speaker to the sound receiving position and the required transfer characteristics with the audio signal and outputting it to the speaker, so as to increase the fundamental sound pressure level in the output low frequency range. However, in this technique, in order to obtain the transfer characteristics of the speaker, it is necessary to perform an experiment in which a microphone is arranged at the sound receiving position in advance. Therefore, it is not easy to accurately calculate the inverse characteristics of the transfer characteristics for each speaker with different characteristics or with characteristic errors. In addition, it is impossible to cope with the secular change of the transfer characteristics of the speaker.

[0012] Therefore, the problem to be solved by the present invention is to correct the output characteristics of the speaker to the target output characteristics with high precision in accordance with the actual transfer characteristics of each speaker.

[0013] Means for solving the problem:

[0014] To achieve the above problem, the present invention is an output characteristic correction system for a speaker that corrects the output characteristics of the speaker for an audio signal output from a sound source device, and is provided with: a filter that applies a set filter transfer characteristic to the audio signal output from the sound source device and outputs it to the speaker; a transfer characteristic setting mechanism that sets the filter transfer characteristic of the filter; and a displacement detection mechanism that detects the displacement of the vibration system of the speaker.

[0015] Here, the transfer characteristic setting mechanism sets the transfer characteristic of the inverse transfer characteristic and the target transfer characteristic for imparting the basic transfer characteristic as the filter transfer characteristic to the filter. The basic transfer characteristic is the transfer characteristic from the audio signal to the sound signal value at a specified sound reception point when the audio signal output from the sound source device is used as the output of the filter as it is. The target transfer characteristic is the transfer characteristic such that if the transfer characteristic from the audio signal to the sound signal value at the sound reception point is this target transfer characteristic when the audio signal output from the sound source device is used as the output of the filter as it is, a sound signal value having the target sound signal characteristic can be obtained at the sound reception point. In addition, the transfer characteristic setting mechanism determines the parameters of the equivalent circuit of the speaker based on the response of the displacement detected by the displacement detection mechanism for the audio signal output from the sound source device, calculates the inverse transfer characteristic according to the equivalent circuit having the determined parameters, and sets the transfer characteristic for imparting the calculated inverse transfer characteristic and the target transfer characteristic as the filter transfer characteristic to the filter.

[0016] Here, in such an output characteristic correction system for a speaker, a transfer characteristic update mechanism for updating the filter transfer characteristic of the filter may also be provided. In the transfer characteristic update mechanism, based on the displacement detected by the displacement detection mechanism, a change in the parameters of the equivalent circuit of the speaker is detected, the inverse transfer characteristic is updated according to the detected changed parameters, and the filter transfer characteristic of the filter is updated to the transfer characteristic for imparting the updated inverse transfer characteristic and the target transfer characteristic.

[0017] In addition, in an output characteristic correction system of such a speaker, there may also be provided: a transfer characteristic update mechanism that updates the filter transfer characteristic of the filter; and an input detection mechanism that detects the input current and input voltage of the speaker. In the transfer characteristic update mechanism, based on the impedance of the speaker obtained from the input current and input voltage detected by the input detection mechanism, a change in the parameters of the equivalent circuit of the speaker is detected, the inverse transfer characteristic is updated according to the equivalent circuit having the detected changed parameters, and the filter transfer characteristic of the filter is updated to a transfer characteristic for imparting the updated inverse transfer characteristic and the target transfer characteristic.

[0018] In addition, in order to achieve the above object, the present invention is an output characteristic correction system for a speaker that corrects the output characteristic of the speaker with respect to an audio signal output from a sound source device. The system includes: a filter that outputs the audio signal output from the sound source device to the speaker after applying a set filter transfer characteristic; a transfer characteristic update mechanism that updates the filter transfer characteristic of the filter; and a displacement detection mechanism that detects the displacement of the vibration system of the speaker. The filter transfer characteristic is a transfer characteristic for imparting the inverse transfer characteristic of the basic transfer characteristic and the target transfer characteristic. The basic transfer characteristic is the transfer characteristic from the audio signal to the sound signal value at a specified sound reception point when the audio signal output from the sound source device is directly used as the output of the filter. The target transfer characteristic is the transfer characteristic such that if the transfer characteristic from the audio signal to the sound signal value at the sound reception point is this target transfer characteristic when the audio signal output from the sound source device is directly used as the output of the filter, a sound signal value having a target sound signal characteristic can be obtained at the sound reception point. In addition, the transfer characteristic update mechanism detects a change in the parameters of the equivalent circuit of the speaker based on the displacement detected by the displacement detection mechanism, updates the inverse transfer characteristic according to the equivalent circuit having the detected changed parameters, and updates the filter transfer characteristic of the filter to a transfer characteristic for imparting the updated inverse transfer characteristic and the target transfer characteristic.

[0019] In addition, in order to achieve the above object, the present invention is an output characteristic correction system for a speaker, which corrects the output characteristic of the speaker for an audio signal output from a sound source device, and is characterized in that it is provided with: a filter that applies a set filter transfer characteristic to the audio signal output from the sound source device and outputs it to the speaker; a transfer characteristic update mechanism that updates the filter transfer characteristic of the filter; and an input detection mechanism that detects the input current and input voltage of the speaker. Here, the filter transfer characteristic is a transfer characteristic for imparting an inverse transfer characteristic of a basic transfer characteristic and a target transfer characteristic. The basic transfer characteristic is a transfer characteristic from the audio signal to the sound signal value at a specified sound reception point when the audio signal output from the sound source device is directly used as the output of the filter. The target transfer characteristic is a transfer characteristic such that if the transfer characteristic from the audio signal to the sound signal value at the sound reception point is this target transfer characteristic when the audio signal output from the sound source device is directly used as the output of the filter, a sound signal value having a target sound signal characteristic can be obtained at the sound reception point. In addition, the transfer characteristic update mechanism detects a change in the parameters of the equivalent circuit of the speaker based on the impedance of the speaker obtained from the input current and input voltage detected by the input detection mechanism, updates the inverse transfer characteristic according to the equivalent circuit having the detected changed parameters, and updates the filter transfer characteristic of the filter to a transfer characteristic for imparting the updated inverse transfer characteristic and the target transfer characteristic.

[0020] In addition, in the above output characteristic correction system for a speaker, the target sound signal characteristic may be set to the frequency characteristic of the sound pressure level, and the sound signal value may be set to the sound pressure level.

[0021] In addition, in this case, the basic transfer characteristic as the transfer characteristic from the audio signal to the sound signal value, that is, the sound pressure level, at the sound reception point may also be set to: a transfer characteristic determined according to the transfer characteristic from the audio signal to the displacement of the vibration system of the speaker obtained through the equivalent circuit of the speaker and a function for determining the relationship between the displacement of the vibration system of the speaker and the sound pressure level at the sound reception point.

[0022] In addition, in this case, the frequency characteristic of the sound pressure level as the target sound signal characteristic may also be set to: a frequency characteristic such that the sound pressure level at the sound reception point is greater in the low frequency range than when the audio signal output from the sound source device is directly used as the output of the filter.

[0023] In addition, in the case of using such a target transfer characteristic, the transfer characteristic setting mechanism may also use an equivalent circuit obtained by correcting an equivalent circuit having the determined parameters in a manner that reduces impedance, as an equivalent circuit of a virtual speaker that can obtain an audio signal value having a target audio signal characteristic at the sound reception point, estimate the target transfer characteristic, and set, as the filter transfer characteristic, a transfer characteristic for imparting the estimated inverse transfer characteristic and the estimated target transfer characteristic to the filter.

[0024] In addition, the present invention also provides an audio system including an output characteristic correction system for a speaker, the speaker, and the sound source device.

[0025] According to the output characteristic correction system or the audio system for a speaker having a transfer characteristic setting mechanism as described above, an equivalent circuit of the speaker is estimated in a manner that matches the displacement of the vibration system of the measured speaker, and an inverse transfer characteristic G is set in a manner that follows the estimated equivalent circuit - , so that the correction of the output characteristic of the speaker to the target output characteristic can match the actual transfer characteristic of each speaker, and as a result, this correction can be performed with high precision.

[0026] In addition, according to the output characteristic correction system or the audio system for a speaker having a transfer characteristic updating mechanism as described above, the equivalent circuit of the speaker can be updated in a manner that matches the displacement of the vibration system of the measured speaker or the impedance of the speaker, and the inverse transfer characteristic G can be updated in a manner that follows the updated equivalent circuit - , so that even when secular changes occur in the transfer characteristic of the speaker, the correction of the output characteristic of the speaker to the target output characteristic can match the actual transfer characteristic of the speaker at each moment, and as a result, this correction can be performed with high precision.

[0027] Advantages of the Invention:

[0028] As described above, according to the present invention, the output characteristic of the speaker can be corrected to the target output characteristic in a manner that matches the actual transfer characteristic of each speaker and with high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 FIG. is a diagram showing the configuration of the audio system according to the embodiment of the present invention.

[0030] Figure 2 FIG. is a diagram showing the configuration of the displacement detection according to the embodiment of the present invention.

[0031] Figure 3 FIG. is a diagram showing the model of the control filter according to the embodiment of the present invention.

[0032] Figure 4 This is a diagram showing the equivalent circuit of a speaker.

[0033] Figure 5 This is a diagram showing the model used in sound pressure estimation.

[0034] Figure 6 This is a diagram showing an example of the impedance of a speaker estimated in an embodiment of the present invention.

[0035] Figure 7 This is a diagram illustrating the effects of an embodiment of the present invention.

[0036] Explanation of reference numerals:

[0037] 1... control unit, 2... speaker, 3... sensor, 4... amplifier, 5... sound source device, 6... signal processing unit, 7... displacement detection unit, 61... control filter, 62... transfer characteristic setting unit, 201... yoke, 202... magnet, 203... front magnetic plate, 204... voice coil bobbin, 205... voice coil, 206... chassis, 207... surround, 208... diaphragm, 209... edge, 210... dust cap, 211... displacement detection magnet, 212... magnetic angle sensor, 220... magnetic circuit, 2011... convex portion. Detailed description of the preferred embodiment

[0038] Hereinafter, an embodiment of the present invention will be described.

[0039] Figure 1 This shows the configuration of the audio system according to the present embodiment.

[0040] As shown in the figure, the audio system includes: a control unit 1, a speaker 2, a sensor 3 disposed on the speaker 2, an amplifier 4, a sound source device 5 that outputs a sound source output signal u(n) as a sound signal, a signal processing unit 6, and a displacement detection unit 7 that measures the displacement xs of the vibration system of the speaker 2 based on the output of the sensor 3.

[0041] In addition, the signal processing unit 6 includes a control filter 61 and a transfer characteristic setting unit 62 that sets or updates the transfer characteristic (filter coefficient) of the control filter 61. Here, the signal processing unit 6 can be configured using a DSP or an MCU. In this case, the control filter 61 and the transfer characteristic setting unit 62 become functional units specifically implemented by software execution.

[0042] In addition, the sound source output signal u(n) output from the sound source device 5 is output as an intermediate output signal to the amplifier 4 via the control filter 61 of the signal processing unit 6. The amplifier 4 amplifies the intermediate output signal with a predetermined gain to generate an amplifier output signal, and drives the speaker 2 using the amplifier output signal.

[0043] Next, Figure 2 a of represents the configuration of the speaker 2.

[0044] As shown in the figure, the speaker 2 has a yoke 201, a magnet 202, a front pole piece 203, a voice coil bobbin 204, a voice coil 205, a chassis 206, a surround 207, a diaphragm 208, a bead 209, a dust cap 210, and a displacement detection magnet 211.

[0045] Here, the upper side in the figure is set as the front of the speaker 2, and the lower side is set as the rear of the speaker 2. The yoke 201 has a convex portion 2011 protruding forward at the central portion, and a ring-shaped magnet 202 is provided on the outer peripheral portion of the convex portion 2011. A ring-shaped front pole piece 203 is provided above the magnet 202. In addition, the front pole piece 203 is made of a conductive component such as iron. In addition, a magnetic circuit 220 is formed by the yoke 201, the magnet 202, and the front pole piece 203.

[0046] The voice coil bobbin 204 has a hollow cylindrical shape, and a voice coil 205 to which a signal from the amplifier 4 is applied is wound around the outer periphery. In addition, the convex portion 2011 of the yoke 201 is inserted into the hollow portion of the voice coil bobbin 204 from the rear in such a manner that the voice coil bobbin 204 can move back and forth with respect to the yoke 201, and the voice coil 205 is disposed at a position where the magnetic flux generated by the magnetic circuit 220 between the inner peripheral ends of the front pole piece 203 passes.

[0047] The diaphragm 208 has a shape substantially the same as the side surface of a frustum of a cone with the front-rear direction of the speaker 2 as the height direction, and its outer peripheral end is connected to the front end portion of the chassis 206 at the bead 209. In addition, the inner peripheral end of the diaphragm 208 is fixed to the front end portion of the voice coil bobbin 204.

[0048] In the configuration of such a speaker 2, if an output signal from the amplifier 4 is applied to the voice coil 205, the voice coil bobbin 204 vibrates back and forth corresponding to the amplitude of the output signal by the electromagnetic action between the magnetic flux generated from the magnetic circuit 220 and the signal flowing in the voice coil 205. In addition, if the voice coil bobbin 204 vibrates, the diaphragm 208 connected to the voice coil bobbin 204 vibrates, generating a sound corresponding to the signal from the amplifier 4.

[0049] The displacement detection magnet 211 is fixed to the outer peripheral side of the voice coil bobbin 204 so as to move together with the voice coil bobbin 204, and generates a magnetic flux in a direction orthogonal to the magnetic flux generated by the magnetic circuit 220.

[0050] Here, the above-described sensor 3 is fixed to a position of the non-vibrating system of the speaker 2, such as the leading magnetic plate 203, near the displacement detection magnet 211. The sensor 3 is a magnetic angle sensor, as shown in Figure 2 b of Figure 2 , and outputs the arctangent of the angle of the resultant vector Q of the magnetic flux vector Qc acting from the magnetic circuit 220 and the magnetic flux vector Qs acting from the displacement detection magnet 211 as the magnetic angle Qs / Qc. According to the displacement of the displacement detection magnet 211 accompanying the displacement of the voice coil bobbin 204, the magnetic flux vector generated by the displacement detection magnet acting on the sensor 3 changes, so this magnetic angle becomes a value following the displacement amount of the voice coil bobbin 204.

[0051] In addition, as shown in Figure 1 , the displacement detection unit 7 measures the displacement of the vibrating system of the speaker 2 based on the output of the sensor 3, and outputs it as the displacement xs to the transfer characteristic setting unit 62.

[0052] Here, although not shown in the figure, the speaker 2 is provided with an input detection unit that detects the input voltage or input current (the current flowing in the speaker 2), and the input detection unit outputs the information of the detected input voltage or input current to the transfer characteristic setting unit 62.

[0053] Next, Figure 3 shows a block diagram equivalent to the filtering process performed by the control filter 61.

[0054] As shown in the figure, the control filter 61 performs a process equivalent to the following process: applying the inverse transfer characteristic G of the transfer characteristic from the speaker input to a specified sound reception point M to the sound source output signal u(n) output from the sound source device 5, and applying the target transfer characteristic H to the sound source output signal u(n) after applying the inverse transfer characteristic G - , and then outputting it as an intermediate output signal to the amplifier 4. The target transfer characteristic H is the transfer characteristic from the speaker input to the sound reception point M such that the frequency characteristic of the sound pressure level at the sound reception point M becomes the target frequency characteristic. - After that, the target transfer characteristic H is applied to the sound source output signal u(n), and then output as an intermediate output signal to the amplifier 4. The target transfer characteristic H is the transfer characteristic from the speaker input to the sound reception point M such that the frequency characteristic of the sound pressure level at the sound reception point M becomes the target frequency characteristic.

[0055] However, the control filter 61 may actually be configured as a single filter that sets the transfer characteristic obtained by combining the inverse transfer characteristic G - with the target transfer characteristic H.

[0056] Next, the transfer characteristic setting unit 62 performs initial setting and update of the transfer characteristic of the control filter 61.

[0057] First, the initial setting of the transfer characteristic of the control filter 61 performed by the transfer characteristic setting unit 62 will be described.

[0058] The control unit 1 controls the execution of this initial setting during pre - shipment adjustment of the audio system or at the start of actual operation, etc.

[0059] Figure 4 It represents an equivalent circuit of a well - known speaker 2 using Thiele - Small (TS) parameters.

[0060] If an equation is established based on this equivalent circuit for Laplace transform and discrete approximation is performed by the backward Euler method, the displacement x(n) of the vibration system of the speaker 2 with respect to the input audio signal u(n) is expressed by Equation 1.

[0061] x(n) = - a1x(n - 1)-a2x(n - 2)-a3x(n - 3)+b0u(n) ··· Equation 1

[0062] a0 = R e K ms +Fs(R e R ms +L e K ms +Bl 2 )+Fs 2 (R e M ms +L e R ms )+Fs 3 (M ms L e )

[0063] a1 = {- Fs(R e R ms +L e K ms +Bl 2 ) - 2Fs 2 (R e M ms +L e R ms ) - 3Fs 3 (M ms L e )} /

[0064] a0

[0065] a2 = {Fs 2 (R e M ms +L e R ms )+3Fs 3 (M ms L e )} / a0

[0066] a3 = - Fs 3(M ms L e )} / a0

[0067] b0 = Bl / a0

[0068] Fs is the sampling frequency.

[0069] In addition, the inverse function of Equation 1 is Equation 2.

[0070] x(n) = {a0u(n) + a1x(n - 1) + a2x(n - 2) + a3x(n - 3)} / b0 ··· Equation 2

[0071] In addition, regarding Figure 5 the absolute value of the sound pressure |P| at the sound reception point M located at a distance r from the diaphragm on the central axis of the diaphragm with an infinite baffle and a radius of a, through the Rayleigh integral, setting d = r / a, the absolute value of the sound pressure |P| is obtained as Equation 3 or Equation 4 which is an approximation of Equation 3. Among them, U in Equation 4 is the volume velocity, U = πa 2 V0.

[0072] [Equation 1]

[0073]

[0074] [Equation 2]

[0075]

[0076] Therefore, the diaphragm velocity V0 of Equation 3 or Equation 4 is a function of x(n) of Equation 1. Therefore, by obtaining the values of the respective parameters of Equation 1 in the transfer characteristic setting unit 62, setting a prescribed position on the central axis of the speaker 2 as the sound reception point M, and setting the radius a of the diaphragm in a manner matching the radius of the speaker 2, the transfer characteristic G from the input U(n) of the speaker 2 to the absolute value of the sound pressure |P| at the sound reception point M can be obtained through Equation 1 and Equation 3 or Equation 4.

[0077] In addition, based on the obtained transfer characteristic G, using the inverse function of Equation 2, etc., the inverse transfer characteristic G can be estimated - .

[0078] In the transfer characteristic setting unit 62, the values of the respective parameters of Equation 1 can be calculated based on the displacement xs of the vibration system of the speaker 2 detected by the displacement detection unit 7.

[0079] That is, for example, in the transfer characteristic setting unit 62, reference data is stored in advance for a plurality of slightly different error values within the manufacturing tolerance of the speaker 2. The reference data registers the theoretical values of the respective parameters and the correspondence relationship between the displacement response of the speaker 2 corresponding to a specified test signal (for example, a frequency sweep signal) in the case where an error with such an error value exists in various elements of the speaker 2.

[0080] In addition, in the transfer characteristic setting unit 62, in a state where the control filter 61 is set to output the sound source output signal u(n) as it is, a test signal is output to the sound source device 5, and the response of the displacement xs of the vibration system of the speaker 2 corresponding to the test signal detected by the displacement detection unit 7 is recorded. In addition, the theoretical values of the respective parameters are calculated as the values of the respective parameters in Equation 1, and in the reference data, the correspondence relationship between the response of the speaker 2 that best matches the recorded displacement response and the theoretical values of the respective parameters is registered.

[0081] Among them, in the initial setting of the transfer characteristic of the control filter 61, as the values of the respective parameters in Equation 1, the values of the respective parameters obtained in advance according to the design specifications of the speaker 2 or the values of the respective parameters obtained in advance by measurement can also be used.

[0082] Next, the target transfer characteristic H is set in advance for the transfer characteristic from the input U(n) of the speaker 2 to the absolute sound pressure |P| at the sound reception point M. This transfer characteristic is a transfer characteristic obtained in advance in such a way that the frequency characteristic of the absolute sound pressure |P| is made as consistent as possible with the target frequency characteristic.

[0083] The target transfer characteristic H can also be obtained by calculation, simulation, experiment, etc.

[0084] Alternatively, as the target transfer characteristic H, the transfer characteristic G of another type of speaker with good frequency characteristics of the absolute sound pressure |P| or a transfer characteristic obtained by adjusting the transfer characteristic G of the other speaker can also be used. In addition, in this case, the transfer characteristic G of the other type of speaker can also be calculated in the same manner as the transfer characteristic G of the speaker 2 described above.

[0085] Alternatively, the target transfer characteristic H can also use the transfer characteristic G of the speaker 2 calculated on the basis of reducing the spring constant K in Equation 1 ms By reducing K ms the resonance frequency f0 expressed by Equation 5 can be shifted toward the low frequency region.

[0086] [Mathematical formula 3]

[0087]

[0088] For example, if K msIf it is set to 1 / 4, the resonance frequency f0 becomes 1 / 2. The output sound pressure level of the speaker 2 is greatly reduced on the low-frequency side of the resonance frequency f0. Therefore, in the case where the target frequency characteristic of the sound pressure absolute value |P| is a frequency characteristic that increases the sound pressure level of the speaker 2 in the low-frequency range, by using such a target transfer characteristic H to shift the resonance frequency f0 to the low-frequency side, it is possible to suppress the reduction of the sound pressure level in the low-frequency range.

[0089] The transfer characteristic setting unit 62 sets the transfer characteristic for imparting (convolving) the inverse transfer characteristic G obtained as described above - and the target transfer characteristic H as the transfer characteristic of the control filter 61, thereby performing the initial setting of the transfer characteristic of the control filter 61.

[0090] Next, the update of the transfer characteristic of the control filter 61 performed by the transfer characteristic setting unit 62 will be described.

[0091] The execution of this update is controlled by the control unit 1, for example, periodically.

[0092] In the update of the transfer characteristic of the control filter 61, the inverse transfer characteristic G is updated in a manner that matches the change in the actual characteristic of the speaker 2 - , and the transfer characteristic of the control filter 61 is updated to the transfer characteristic for imparting (convolving) the updated inverse transfer characteristic G - and the target transfer characteristic H.

[0093] By updating the parameters of Equation 1 in a manner that follows the change in the actual characteristic of the speaker 2, and using the updated parameters to calculate the above-mentioned inverse transfer characteristic G - , the update of this inverse transfer characteristic G - is performed.

[0094] The update of the parameters does not necessarily have to be performed for all the parameters of Equation 1, and it is also possible to update only a part of the parameters, for example, the parameters whose values are expected to change over time.

[0095] For example, in the case where the parameter K ms whose value changes significantly due to long-term use is set as the object of update, it can be performed as follows.

[0096] That is, if the inductor with small influence in the low-frequency range is ignored in the equivalent circuit of Figure 4 , when i(t) is set as the current, Equations 6 and 7 can be obtained.

[0097] [Equation 4]

[0098]

[0099] [Equation 5]

[0100]

[0101] According to these two equations, by substituting to eliminate the current i(t), Equation 8 can be obtained.

[0102] [Equation 6]

[0103]

[0104] Then, the transfer characteristic setting unit 62 uses the values at the initial setting as the parameters of Equation 1 other than K ms and calculates K according to Equation 8 based on the displacement xs of the vibration system detected by the displacement detection unit 7, or its differential or second differential. ms If the calculated K ms changes by an amount greater than the allowable value, the parameter K ms is updated.

[0105] In addition, when the parameter K ms is set as the object to be updated, the update of K ms can also be performed as follows.

[0106] That is, the resonance frequency f0 at which the impedance v = u / i of the speaker 2 obtained by setting the input current detected by the above input detection unit as i and the input voltage of the speaker 2 as v becomes a peak is detected.

[0107] Then, using M ms calculate according to the above Equation 5:

[0108] K ms = (2πfs) 2 M ms

[0109] If the calculated K ms changes by an amount greater than the allowable value, the parameter K ms is updated.

[0110] Here, in the update of the parameters, the processing of updating the parameters can also be performed according to the accumulated amount of the state related to the parameters of the speaker 2.

[0111] That is, for example, a change table registering the correspondence between the accumulated amount of the state related to the parameters of Equation 1 and the change amount of the elements (specifications) of the speaker 2 can be stored in advance, and the accumulated amount of the state can be managed. The change amount of the elements of the speaker 2 corresponding to the current accumulated amount of the state is obtained from the change table, and the value of the current elements of the speaker 2 is obtained, and the parameters are updated in a manner that matches the obtained element values.

[0112] As a state for managing the amount of accumulation, for example, the temperature at which the magnet demagnetizes can be used. In this case, in the change amount table, the correspondence between the amount of accumulation of the temperature at which the magnet demagnetizes and the demagnetization amount of the magnet is registered in advance. In addition, a temperature sensor is installed on the magnet to detect and record the temperature, or the temperature of the magnet is estimated and recorded based on the heat transfer from the joule heat generated by the voice coil, which is obtained from the input voltage or input current of the speaker 2, to the magnet.

[0113] In addition, based on the recorded temperature history of the magnet, the amount of accumulation of the temperature at which the magnet demagnetizes (for example, the time integral of the temperature at which demagnetization occurs) in the magnet is obtained, and the demagnetization amount of the magnet corresponding to the obtained amount of accumulation is acquired from the change amount table, and the driving force Bl(x) when the magnetic potential of the magnet is reduced by the obtained demagnetization amount of the magnet with respect to the initial value is estimated as the current driving force Bl(x).

[0114] Here, since the driving force Bl(x) is proportional to the magnetic potential of the magnet, the current driving force Bl(x) is a driving force obtained by reducing the driving force Bl(x) stored as the initial value as a parameter by the same ratio as the demagnetization amount of the magnet.

[0115] Here, Figure 7 An example showing the specific effect of the sound system as described above.

[0116] Figure 7 The gray line B is the frequency characteristic of the sound pressure level at the sound reception point M of the speaker 2 with a diameter of 10 cm when the sound source output signal u(n) is directly output to the amplifier 4. The black solid line CntB is the frequency characteristic of the sound pressure level at the sound reception point M of the speaker 2 with a diameter of 10 cm when the above control is performed by the signal processing unit 6. The dotted line Ref is the frequency characteristic of the sound pressure level at the sound reception point M of the speaker 2 with a diameter of 17 cm when the sound source output signal u(n) is directly output to the amplifier 4.

[0117] As shown in the figure, in the low-frequency range below 100 Hz, when the sound source output signal u(n) is directly output to the amplifier 4, the sound pressure level B of the speaker 2 with a diameter of 10 cm is about 10 dBSPL lower than the sound pressure level Ref of the speaker 2 with a diameter of 17 cm. In contrast, when the above control is performed by the signal processing unit 6 for the speaker 2 with a diameter of 10 cm, the difference between the sound pressure level CntB and the sound pressure level Ref of the speaker 2 with a diameter of 17 cm becomes within approximately 1 dBSPL.

[0118] Therefore, according to Figure 7 , it is shown that by this embodiment, the sound pressure level in the low-frequency range can be increased without increasing the diameter of the speaker 2.

[0119] The above describes the embodiments of the present invention.

[0120] As described above, according to this embodiment, an equivalent circuit of the speaker 2 is estimated in a manner that matches the displacement of the vibration system of the measured speaker 2, and the inverse transfer characteristic G is set in a manner that follows the estimated equivalent circuit. - In addition, at each moment, the equivalent circuit of the speaker 2 is updated in a manner that matches the state accumulation amount such as the displacement of the vibration system of the measured speaker 2, the impedance of the speaker 2, or the temperature of the speaker 2, and the inverse transfer characteristic G is updated in a manner that follows the updated equivalent circuit. - .

[0121] Therefore, it is possible to correct the output characteristic of the speaker 2 to the target output characteristic in accordance with the actual transfer characteristic of each speaker 2 at each moment, and as a result, this correction can be performed with high accuracy.

Claims

1. An output characteristic correction system for a speaker, which corrects the output characteristics of the speaker for an audio signal output from a sound source device, characterized in that comprising: a filter that applies a set filter transfer characteristic to an audio signal output from a sound source device and outputs the signal to the speaker; a transfer characteristic setting mechanism that sets the filter transfer characteristic of the filter; and a displacement detection mechanism that detects the displacement of the vibration system of the speaker, wherein the transfer characteristic setting mechanism sets, as the filter transfer characteristic of the filter, a transfer characteristic that is the inverse transfer characteristic for imparting a basic transfer characteristic and a target transfer characteristic, the basic transfer characteristic being the transfer characteristic from the audio signal to the sound signal value at a specified sound reception point when the audio signal output from the sound source device is output as the output of the filter as it is, the target transfer characteristic being the transfer characteristic such that, when the audio signal output from the sound source device is output as the output of the filter as it is, if the transfer characteristic from the audio signal to the sound signal value at the sound reception point is this target transfer characteristic, a sound signal value having a target sound signal characteristic can be obtained at the sound reception point, the transfer characteristic setting mechanism determines the parameters of the equivalent circuit of the speaker based on the response of the displacement detected by the displacement detection mechanism for the audio signal output from the sound source device, calculates the inverse transfer characteristic according to the equivalent circuit having the determined parameters, and sets, as the filter transfer characteristic of the filter, a transfer characteristic for imparting the calculated inverse transfer characteristic and the target transfer characteristic; 2. The output characteristic correction system of the loudspeaker according to claim 1, characterized in that, comprising: a transfer characteristic update mechanism that updates the filter transfer characteristic of the filter, wherein the transfer characteristic update mechanism detects a change in the parameters of the equivalent circuit of the speaker based on the displacement detected by the displacement detection mechanism, updates the inverse transfer characteristic according to the detected changed parameters, and updates the filter transfer characteristic of the filter to a transfer characteristic for imparting the updated inverse transfer characteristic and the target transfer characteristic; 3. The output characteristic correction system of the loudspeaker according to claim 1, characterized in that, comprising: a transfer characteristic update mechanism that updates the filter transfer characteristic of the filter; and an input detection mechanism that detects the input current and input voltage of the speaker, wherein the transfer characteristic update mechanism detects a change in the parameters of the equivalent circuit of the speaker based on the impedance of the speaker obtained from the input current and input voltage detected by the input detection mechanism, updates the inverse transfer characteristic according to the equivalent circuit having the detected changed parameters, and updates the filter transfer characteristic of the filter to a transfer characteristic for imparting the updated inverse transfer characteristic and the target transfer characteristic; 4. An output characteristic correction system for a speaker, which corrects the output characteristics of the speaker for an audio signal output from a sound source device, is characterized in that, comprising: a filter that applies a set filter transfer characteristic to an audio signal output from a sound source device and outputs the signal to the speaker; a transfer characteristic update mechanism that updates the filter transfer characteristic of the filter; and a displacement detection mechanism that detects the displacement of the vibration system of the speaker, The filter transfer characteristic is a transfer characteristic for imparting an inverse transfer characteristic and a target transfer characteristic to a basic transfer characteristic. The basic transfer characteristic is a transfer characteristic from the audio signal to the sound signal value at a specified sound reception point when the audio signal output from the sound source device is directly output as the output of the filter. The target transfer characteristic is a transfer characteristic such that, when the audio signal output from the sound source device is directly output as the output of the filter, if the transfer characteristic from the audio signal to the sound signal value at the sound reception point is this target transfer characteristic, then a sound signal value having a target sound signal characteristic can be obtained at the sound reception point. The transfer characteristic updating mechanism detects a change in the parameters of the equivalent circuit of the speaker based on the displacement detected by the displacement detection mechanism, updates the inverse transfer characteristic according to the equivalent circuit having the detected changed parameters, and updates the filter transfer characteristic of the filter to a transfer characteristic for imparting the updated inverse transfer characteristic and the target transfer characteristic.

5. An output characteristic correction system for a speaker, which corrects the output characteristics of the speaker for an audio signal output from a sound source device, is characterized in that Comprising: A filter that outputs to the speaker after applying a set filter transfer characteristic to the audio signal output from the sound source device; A transfer characteristic updating mechanism that updates the filter transfer characteristic of the filter; And An input detection mechanism that detects the input current and input voltage of the speaker, The filter transfer characteristic is a transfer characteristic for imparting an inverse transfer characteristic and a target transfer characteristic to a basic transfer characteristic. The basic transfer characteristic is a transfer characteristic from the audio signal to the sound signal value at a specified sound reception point when the audio signal output from the sound source device is directly output as the output of the filter. The target transfer characteristic is a transfer characteristic such that, when the audio signal output from the sound source device is directly output as the output of the filter, if the transfer characteristic from the audio signal to the sound signal value at the sound reception point is this target transfer characteristic, then a sound signal value having a target sound signal characteristic can be obtained at the sound reception point. The transfer characteristic updating mechanism detects a change in the parameters of the equivalent circuit of the speaker based on the impedance of the speaker obtained from the input current and input voltage detected by the input detection mechanism, updates the inverse transfer characteristic according to the equivalent circuit having the detected changed parameters, and updates the filter transfer characteristic of the filter to a transfer characteristic for imparting the updated inverse transfer characteristic and the target transfer characteristic.

6. The output characteristic correction system for a speaker according to any one of claims 1 to 5, wherein The target sound signal characteristic is the frequency characteristic of the sound pressure level, and the sound signal value is the sound pressure level.

7. The output characteristic correction system for a speaker according to claim 6, wherein The basic transfer characteristic, which is the transfer characteristic from the audio signal to the sound signal value, i.e., the sound pressure level, at the sound reception point, is determined by the transfer characteristic from the audio signal to the displacement of the vibration system of the speaker obtained from the equivalent circuit of the speaker and a function for determining the relationship between the displacement of the vibration system of the speaker and the sound pressure level at the sound reception point.

8. The speaker output characteristic correction system according to claim 6, wherein The frequency characteristic of the sound pressure level as the target sound signal characteristic is a frequency characteristic such that the sound pressure level at the sound reception point is greater in the low frequency range than in the case where the audio signal output from the sound source device is directly used as the output of the filter.

9. The speaker output characteristic correction system according to claim 8, wherein The transfer characteristic setting mechanism uses an equivalent circuit obtained by modifying the equivalent circuit having the determined parameters in a manner that reduces the impedance as the equivalent circuit of a virtual speaker capable of obtaining a sound signal value having the target sound signal characteristic at the sound reception point, estimates the target transfer characteristic, and sets the transfer characteristic for imparting the estimated inverse transfer characteristic and the estimated target transfer characteristic as the filter transfer characteristic to the filter.

10. An audio system, characterized in that, A speaker output characteristic correction system, the speaker, and the sound source device according to any one of claims 1 to 7.

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