Speaker displacement measurement system and acoustic system

Abstract

To provide "a speaker displacement measurement system and an acoustic system" that can secure accuracy of displacement measurement.SOLUTION: A displacement detection magnet 211 is fixed to a voice coil bobbin 204 of a loudspeaker 2. A magnetic angle sensor 3 is held near the displacement detection magnet 211, movably by a sensor moving mechanism 6. Displacement of a vibration system of the speaker 2 is measured from an angle of a composite vector of a magnetic vector of a speaker 2's own magnetic circuit and the displacement detection 211 detected by the magnetic angle sensor 3. If there is any deviation from a target displacement-magnetic angle characteristic in a displacement-magnetic angle characteristic measured by outputting a test signal with a known response displacement to the loudspeaker 2, the magnetic angle sensor 3 is moved by the sensor moving mechanism 6 to an arrangement where the target displacement-magnetic angle characteristic is obtained by estimation.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a technology for measuring displacement of a vibration system of a speaker. [Background Art]

[0002] Further, as a technology for measuring displacement of a vibration system of a speaker, a motional feedback technology is known, in which a capacitive sensor or an optical sensor for detecting displacement of a diaphragm of the speaker is provided, and driving of the speaker is controlled according to vibration detected by the sensor so as to eliminate output distortion (for example, Patent Documents 1 and 2). [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2008-228214 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2010-124026 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] As a configuration for measuring displacement of a vibration system of a speaker, a configuration is conceivable in which a displacement detecting magnet fixed to the vibration system of the speaker and a magnetic angle sensor fixed to a non-vibration system of the speaker are used, and the magnetic angle sensor detects a magnetic angle of a combined vector of a magnetic flux vector generated by a magnetic circuit of the speaker itself and a magnetic flux vector generated by the displacement detecting magnet.

[0005] Since displacement of the displacement detecting magnet accompanying displacement of the vibration system changes the magnetic flux vector generated by the displacement detecting magnet as viewed from the magnetic angle sensor, the magnetic angle detected by the magnetic angle sensor changes in accordance with displacement of the vibration system, and displacement of the vibration system can be measured by converting the magnetic angle into displacement in accordance with displacement-magnetic angle characteristics.

[0006] On the other hand, with this configuration, if the relationship between the speaker's own magnetic circuit, the magnet for displacement detection, and the magnetic angle sensor is different in terms of position and orientation, the displacement-magnetic angle characteristics will be different. Therefore, if the manufacturing tolerance (manufacturing error) is large, the actual displacement-magnetic angle characteristics will deviate from the assumed displacement-magnetic angle characteristics, making it impossible to accurately measure the displacement of the vibration system. Also, if the relationship between the position and orientation described above changes due to aging, the actual displacement-magnetic angle characteristics will change, making it impossible to accurately measure the displacement of the vibration system.

[0007] Therefore, the object of the present invention is to provide a speaker displacement measurement system that can ensure the accuracy of displacement measurement of the speaker's vibration system. [Means for solving the problem]

[0008] To achieve the above objectives, the present invention provides a speaker displacement measurement system for detecting the displacement of the speaker's vibration system, comprising: a displacement detection magnet fixed to the speaker's vibration system; a magnetic angle sensor that detects the angle of the acting magnetic flux and outputs it as a magnetic angle; and a sensor movable mechanism fixed to the speaker's non-vibrating system that holds the magnetic angle sensor in a position where a magnetic flux resulting from the combination of the magnetic flux of the speaker's own magnetic circuit and the magnetic flux of the displacement detection magnet acts. Here, the sensor movable mechanism can move the held magnetic angle sensor to change the position of the magnetic angle sensor relative to the speaker's non-vibrating system.

[0009] In this speaker displacement measurement system, the sensor movable mechanism may be configured such that the held magnetic angle sensor is movable in at least the axial direction of each of the three orthogonal axes fixed to the non-vibrating system of the speaker. Furthermore, the sensor movable mechanism may be configured to allow the held magnetic angle sensor to rotate around at least one of the three axes. Furthermore, the speaker displacement measurement system is provided with a sensor placement adjustment means that controls the sensor movable mechanism to adjust the placement of the magnetic angle sensor. The characteristic of the correspondence between the displacement of the speaker's vibration system and the magnetic angle is defined as the displacement-magnetic angle characteristic. The sensor placement adjustment means outputs a predetermined test signal to the speaker and measures the displacement-magnetic angle characteristic, which shows the characteristic of the correspondence between the displacement of the speaker's vibration system, which is expected as a response to the test signal, and the magnetic angle output by the magnetic angle sensor during the output of the test signal. If the measured displacement-magnetic angle characteristic indicates that there are multiple magnetic angles corresponding to different displacements, the sensor movable mechanism is controlled to adjust the placement of the magnetic angle sensor. Adjust.

[0010] or The speaker displacement measurement system described above is provided with a sensor placement adjustment means that controls the sensor movable mechanism to adjust the placement of the magnetic angle sensor. The characteristic of the correspondence between the displacement of the speaker's vibration system and the magnetic angle is defined as the displacement-magnetic angle characteristic. The sensor placement adjustment means outputs a predetermined test signal to the speaker and measures the displacement-magnetic angle characteristic, which shows the characteristic of the correspondence between the displacement of the speaker's vibration system, which is expected as a response to the test signal, and the magnetic angle output by the magnetic angle sensor during the output of the test signal. If the correlation between the measured displacement-magnetic angle characteristic and a predetermined displacement-magnetic angle characteristic is smaller than a predetermined threshold, the sensor movable mechanism is controlled to adjust the placement of the magnetic angle sensor. Adjust.

[0011] orThe speaker displacement measurement system described above is provided with a sensor placement adjustment means that controls the sensor movable mechanism to adjust the arrangement of the magnetic angle sensors. The characteristic of the correspondence between the displacement of the speaker's vibration system and the magnetic angle is defined as the displacement-magnetic angle characteristic. The sensor placement adjustment means outputs a predetermined test signal to the speaker and measures the displacement-magnetic angle characteristic, which shows the characteristic of the correspondence between the displacement of the speaker's vibration system, which is expected as a response to the test signal, and the magnetic angle output by the magnetic angle sensor during the output of the test signal. For a plurality of predetermined arrangements of magnetic angle sensors, according to the arrangement-specific characteristic information in which the correspondence between the arrangement of magnetic angle sensors and the displacement-magnetic angle characteristic is registered, the arrangement of the magnetic angle sensor whose correspondence with the measured displacement-magnetic angle characteristic is registered in the arrangement-specific characteristic information is estimated as the current arrangement of magnetic angle sensors. The sensor movable mechanism is controlled to adjust the arrangement of the magnetic angle sensors so that the deviation of the estimated current arrangement of magnetic angle sensors from a predetermined sensor arrangement is eliminated. Adjust.

[0012] Furthermore, the present invention also provides an acoustic system equipped with the above-described speaker displacement measurement system. This acoustic system includes the speaker, a sound source device that outputs sound, a displacement conversion means that converts the magnetic angle output by the magnetic angle sensor into the displacement of the speaker's vibration system, and a signal correction means that, referring to the displacement converted by the displacement conversion means, corrects the sound output by the sound source device so as to reduce the output distortion of the speaker and outputs it to the speaker.

[0013] With the speaker displacement measurement system and acoustic system described above, even if the arrangement of the magnetic angle sensors becomes such that the expected displacement-magnetic angle characteristics cannot be obtained due to manufacturing tolerances (manufacturing errors) or aging, the sensor movable mechanism allows the arrangement of the magnetic angle sensors to be adjusted to an arrangement that can obtain the expected displacement-magnetic angle characteristics. This ensures the accuracy of displacement measurement of the speaker's vibration system using magnetic angle sensors. Effects of the Invention

[0014] As described above, according to the present invention, a speaker displacement measurement system capable of guaranteeing the accuracy of displacement measurement of a speaker vibration system can be provided. Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a diagram showing the configuration of an acoustic system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the configuration of a speaker according to an embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing a configuration example of a sensor movable mechanism according to an embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing the contents of reference data and a characteristic data set according to an embodiment of the present invention. [Figure 5] FIG. 5 is a diagram showing an example of displacement-magnetic angle characteristics according to an embodiment of the present invention. [Figure 6] FIG. 6 is a flowchart showing sensor arrangement adjustment processing according to an embodiment of the present invention. Mode for Carrying Out the Invention

[0016] Embodiments of the present invention will be described below. FIG. 1 shows the configuration of an acoustic system according to the present embodiment. As illustrated, the acoustic system includes a sound source device (1), a speaker (2), a magnetic angle sensor (3), a signal correction unit (4), an amplifier (5), a sensor movable mechanism (6), a displacement conversion unit (7), a sensor arrangement adjustment unit (8), and a storage unit (9). The storage unit (9) stores reference data, a characteristic data set, and test signal displacement data. However, the displacement conversion unit (7), the signal correction unit (4), the sensor arrangement adjustment unit (8), and the like may be provided as functional units embodied by a processor executing a program. FIG. 2a shows the configuration of the speaker (2). As shown in the figure, speaker 2 includes a yoke 201, a magnet 202, a top plate 203, a voice coil bobbin 204, a voice coil 205, a frame 206, a damper 207, a diaphragm 208, an edge 209, a dust cap 210, and a displacement detection magnet 211. In this diagram, with the upper part representing the front of the front speaker and the lower part representing the rear of the front speaker, the yoke 201 has a hollow protrusion 2011 projecting forward in its central part. An annular magnet 202 is provided on the outer circumference of this protrusion 2011, and an annular top plate 203 is provided on top of the magnet 202. This top plate 203 is made of a conductive material such as iron. The yoke 201, magnet 202, and top plate 203 form a magnetic circuit 220.

[0017] The voice coil bobbin 204 has a hollow cylindrical shape, and the voice coil 205, to which the signal from the amplifier 5 is applied, is wound around its outer circumference. The protrusion 2011 of the yoke 201 is inserted from the rear into the hollow of the voice coil bobbin 204 so that the voice coil bobbin 204 can move back and forth relative to the yoke 201. The voice coil 205 is positioned between the protrusion 2011 of the yoke 201 and the top plate 203, through which the magnetic flux generated between the inner ends of the top plate 203 by the magnetic circuit 220 passes.

[0018] The diaphragm 208 has a shape roughly similar to the side of a frustum of a cone, with the front-to-back direction of the front speaker as the height direction, and its outer edge is connected to the front end of the frame 206 by an edge 209. The inner edge of the diaphragm 208 is fixed to the front end of the voice coil bobbin 204.

[0019] In this speaker 2 configuration, when a signal is applied to the voice coil 205 from the amplifier 5, the electromagnetic interaction between the magnetic flux generated from the magnetic circuit 220 and the signal flowing through the voice coil 205 causes the voice coil bobbin 204 to vibrate back and forth in accordance with the amplitude of the signal. When the voice coil bobbin 204 vibrates, the diaphragm 208 connected to the voice coil bobbin 204 vibrates, generating sound corresponding to the signal from the amplifier 5.

[0020] The displacement detection magnet 211 is fixed to the outer circumference of the voice coil bobbin 204 so as to move up and down together with the voice coil bobbin 204, and generates a magnetic flux perpendicular to the magnetic flux generated from the magnetic circuit 220. A sensor movable mechanism 6 is positioned within the hollow space of the protrusion 2011 of the yoke 201, fixed to the yoke 201. Furthermore, the magnetic angle sensor 3 is held movably by the sensor movable mechanism 6 at a position near the displacement detection magnet 211 on the inner circumference side of the voice coil bobbin 204. As shown in Figure 2b, the magnetic angle sensor 3 detects and outputs the arctangent Vs / Vc of the combined vector V, which is the angle of the magnetic flux vector Vc acting from the magnetic circuit 220 and the magnetic flux vector Vs acting from the displacement detection magnet 211, as the magnetic angle ω. As the displacement of the displacement detection magnet 211 due to the displacement of the voice coil bobbin 204 causes the magnetic flux vector generated by the displacement detection magnet acting on the magnetic angle sensor 3 to change, this magnetic angle ω will be a value that corresponds to the displacement of the voice coil bobbin 204.

[0021] Next, Figure 3 shows an example of the configuration of the sensor movable mechanism 6. In the following explanation, the X-axis direction will be defined as the direction from the central axis perpendicular to the central axis of speaker 2 toward the displacement detection magnet 211, the Y-axis direction will be defined as the direction perpendicular to the X-axis direction and the direction of the central axis of speaker 2, and the Z-axis direction will be defined as the direction of the central axis of speaker 2. As shown in the figure, the sensor movable mechanism 6 includes a holder 61 that holds the magnetic angle sensor 3, a rotation mechanism 62 that supports the holder 61 and rotates the holder 61 around the X axis, a Z-direction linear motion mechanism 63 that supports the rotation mechanism 62 and moves the rotation actuator in the Z-axis direction, a Y-direction linear motion mechanism 64 that supports the Z-direction linear motion mechanism 63 and moves the Z-direction linear motion mechanism 63 in the Y-axis direction, and an X-direction linear motion mechanism 65 that supports the Y-direction linear motion mechanism 64 and moves the Y-direction linear motion mechanism 64 in the X-axis direction. The rotation mechanism 62 can be realized by a mechanism using a servo motor or the like, and each linear motion mechanism can be realized by a mechanism combining a servo motor and a ball screw or the like.

[0022] Furthermore, with the sensor movable mechanism 6 having such a configuration, the position x in the X-axis direction, the position y in the Y-axis direction, the position z in the Z-axis direction, and the rotation angle θ around the X-axis of the magnetic angle sensor 3 held in the holder 61 can be changed and adjusted. Returning to Figure 1, the displacement conversion unit 7 converts the magnetic angle output from the magnetic angle sensor 3 into a displacement according to a preset displacement-magnetic angle characteristic for displacement conversion and outputs it. The signal correction unit 4, while referring to the displacement output from the displacement conversion unit 7, corrects the sound output from the sound source device 1 so that the output distortion of speaker 2 is eliminated, and then performs a signal correction operation to output to speaker 2 via amplifier 5.

[0023] Next, we will explain the reference data and characteristic data set stored in the memory unit 9. The combination of the X-axis position x, Y-axis position y, Z-axis position z, and rotation angle θ around the X-axis of the magnetic angle sensor 3 (x, y, z, θ) is referred to as the sensor configuration. As shown in Figure 4a, the reference data includes the sensor configuration (xr, yr, zr, θr) and the displacement-magnetic angle characteristic showing the relationship between displacement dx and magnetic angle ω.

[0024] The displacement-magnetic angle characteristics registered in the reference data are those best suited for displacement measurement, obtained experimentally or through simulation for various sensor configurations. The sensor configurations (xr, yr, zr, θr) registered in the reference data are those for which the most suitable displacement-magnetic angle characteristics were obtained.

[0025] Furthermore, the displacement-magnetic angle characteristics registered in the reference data are also set in the displacement conversion unit 7 as the displacement-magnetic angle characteristics for displacement conversion as described above. Here, the displacement-magnetic angle characteristic most suitable for measuring displacement is, for example, characteristic A in Figure 5, a characteristic in which the change in magnetic angle ω with respect to the change in displacement dx is as linear as possible, and the change in magnetic angle ω with respect to the change in displacement dx is as large as possible. Here, as in characteristic B, if the change in magnetic angle ω is small in response to the change in displacement dx, it becomes impossible to measure the displacement with good resolution, and displacement measurement becomes impossible in the range of displacement dx where the magnetic angle ω does not change. Furthermore, in cases like characteristic C, where there is a displacement-magnetic angle characteristic reflection where multiple displacements dx correspond to the same magnetic angle ω, it becomes impossible to determine the displacement dx from the magnetic angle ω. Next, as shown in Figure 4b, the characteristic dataset is registered in association with the displacement-magnetic angle characteristics obtained experimentally or through simulation for multiple different sensor configurations (xi, yi, zi, θi), and the sensor configurations for which those displacement-magnetic angle characteristics were obtained. Next, we will explain the sensor placement adjustment process performed by the sensor placement adjustment unit 8 in Figure 1. Sensor placement adjustment is performed during the initial setup of the acoustic system, and thereafter, it is performed periodically or according to instructions from a human by the sensor placement adjustment unit 8. Figure 6 shows the procedure for this sensor placement adjustment process. As shown in the diagram, in this process, first, the signal correction operation of the signal correction unit 4 is stopped (step 602), and the sound input from the sound source device 1 to the signal correction unit 4 is output directly to the speaker 2 via the amplifier 5. Next, the sound source device 1 is made to output a predetermined test signal (step 604). Preferably, the test signal is a sound signal that contains only components with frequencies lower than the audible range. Next, the current displacement-magnetic angle characteristics of speaker 2 are measured (step 606). This measurement is performed by acquiring the magnetic angle ω output from the magnetic angle sensor 3 at each point in time during the test signal output, and calculating the displacement-magnetic angle characteristics by using the acquired magnetic angle ω as the detected magnetic angle ω for the displacement dx that is estimated to occur as a response to the test signal at that point in time.

[0026] Here, the displacement that is estimated to occur as a response to the test signal at each point in time is calculated in advance by experiment or simulation, and stored in the storage unit 9 as test signal displacement data. In step 606, the current displacement-magnetic angle characteristics of speaker 2 are measured according to the test signal displacement data.

[0027] Next, the displacement-magnetic angle characteristics measured in step 606 are checked to see if there is any reflection, as shown in characteristic C of Figure 5, where multiple displacements dx correspond to the same magnetic angle ω (step 608). If reflection exists, the process proceeds to step 614. If no folding occurs, the correlation coefficient between the displacement-magnetic angle characteristics measured in step 606 and the displacement-magnetic angle characteristics of the reference data is calculated, for example, using Equation 1 below (step 610).

number

[0028] Then, the sensor configuration registered in the characteristic dataset is estimated as the current sensor configuration in correspondence with the explored displacement-magnetic angle characteristics, and the difference between the estimated current sensor configuration and the sensor configuration in the reference data is calculated (step 616). Then, the sensor movable mechanism 6 is controlled to move the magnetic angle sensor 3 by the calculated difference (step 618). In other words, if the sensor arrangement of the reference data is (xr, yr, zr, θr) and the sensor arrangement estimated as the current sensor arrangement in step 616 is (xq, yq, zq, θq), then the difference is (xr-xq, yr-yq, zr-zq, θr-θq). Therefore, the sensor movable mechanism 6 is controlled to move the magnetic angle sensor 3 by xr-xq in the X-axis direction, yr-yq in the Y-axis direction, zr-zq in the Z-axis direction, and θr-θq around the X-axis.

[0029] Here, it is expected that the movement of the magnetic angle sensor 3 in step 618 will allow the sensor position of the magnetic angle sensor 3 to be adjusted to obtain the same displacement-magnetic angle characteristics as the reference data. Then, the signal correction operation of the signal correction unit 4 is restarted (step 620), and the sensor placement adjustment process is completed. Embodiments of the present invention have been described above. Hereinafter, the sensor movable mechanism 6 has been described as being capable of moving the magnetic angle sensor 3 in the X-axis direction, the Y-axis direction, the Z-axis direction, and rotational movement around the X-axis. However, the sensor movable mechanism 6 does not necessarily have to be capable of all of these movements. For example, the sensor movable mechanism 6 may only be capable of moving the magnetic angle sensor 3 in the X-axis direction, the Y-axis direction, and the Z-axis direction. Alternatively, the sensor movable mechanism 6 may be capable of rotating the magnetic angle sensor 3 around the Y-axis and rotating it around the Z-axis.

[0030] In these cases, the sensor arrangement in the above embodiments uses a combination of coordinates and angles in the direction in which movement is possible. [Explanation of Symbols]

[0031] 1...Sound source device, 2...Speaker, 3...Magnetic angle sensor, 4...Signal correction unit, 5...Amplifier, 6...Sensor movable mechanism, 7...Displacement conversion unit, 8...Sensor placement adjustment unit, 9...Memory unit, 61...Holder, 62...Rotation mechanism, 63...Z-direction linear motion mechanism, 64...Y-direction linear motion mechanism, 65...X-direction linear motion mechanism, 201...Yoke, 202...Magnet, 203...Top plate, 204...Voice coil bobbin, 205...Voice coil, 206...Frame, 207...Damper, 208...Diaphragm, 209...Edge, 210...Dust cap, 211...Magnet for displacement detection, 220...Magnetic circuit, 2011...Protrusion.

Claims

1. A speaker displacement measurement system that detects the displacement of the speaker's vibration system, A displacement detection magnet fixed to the speaker's vibration system, A magnetic angle sensor that detects the angle of the acting magnetic flux and outputs it as a magnetic angle, A sensor movable mechanism fixed to the non-vibrating system of the speaker, which holds the magnetic angle sensor in a position where a magnetic flux obtained by combining the magnetic flux of the speaker's own magnetic circuit and the magnetic flux of the displacement detection magnet acts upon it, and which is capable of moving the held magnetic angle sensor to change the position of the magnetic angle sensor relative to the non-vibrating system of the speaker. It has a sensor placement adjustment means that controls the sensor movable mechanism to adjust the arrangement of the magnetic angle sensor, The characteristic of the correspondence between the displacement of the speaker's vibration system and the magnetic angle is defined as the displacement-magnetic angle characteristic. The speaker displacement measurement system is characterized in that the sensor placement adjustment means outputs a predetermined test signal to the speaker, measures a displacement-magnetic angle characteristic which shows the relationship between the displacement of the speaker's vibration system that can be expected as a response to the test signal and the magnetic angle output by the magnetic angle sensor during the output of the test signal, and controls the sensor movable mechanism to adjust the placement of the magnetic angle sensor when the measured displacement-magnetic angle characteristic indicates that there are magnetic angles corresponding to multiple different displacements.

2. A speaker displacement measurement system for detecting the displacement of the vibration system of a speaker, A displacement detection magnet fixed to the speaker's vibration system, A magnetic angle sensor that detects the angle of the acting magnetic flux and outputs it as a magnetic angle, A sensor movable mechanism fixed to the non-vibrating system of the speaker, which holds the magnetic angle sensor in a position where a magnetic flux obtained by combining the magnetic flux of the speaker's own magnetic circuit and the magnetic flux of the displacement detection magnet acts upon it, and which is capable of moving the held magnetic angle sensor to change the position of the magnetic angle sensor relative to the non-vibrating system of the speaker. It has a sensor placement adjustment means that controls the sensor movable mechanism to adjust the arrangement of the magnetic angle sensor, The characteristic of the correspondence between the displacement of the speaker's vibration system and the magnetic angle is defined as the displacement-magnetic angle characteristic. The speaker displacement measurement system is characterized in that the sensor placement adjustment means outputs a predetermined test signal to the speaker, measures a displacement-magnetic angle characteristic which shows the relationship between the displacement of the speaker's vibration system that can be expected as a response to the test signal and the magnetic angle output by the magnetic angle sensor during the output of the test signal, and controls the sensor movable mechanism to adjust the placement of the magnetic angle sensor when the correlation between the measured displacement-magnetic angle characteristic and a predetermined displacement-magnetic angle characteristic is smaller than a predetermined threshold.

3. A speaker displacement measurement system for detecting the displacement of the vibration system of a speaker, A displacement detection magnet fixed to the speaker's vibration system, A magnetic angle sensor that detects the angle of the acting magnetic flux and outputs it as a magnetic angle, A sensor movable mechanism fixed to the non-vibrating system of the speaker, which holds the magnetic angle sensor in a position where a magnetic flux obtained by combining the magnetic flux of the speaker's own magnetic circuit and the magnetic flux of the displacement detection magnet acts upon it, and which is capable of moving the held magnetic angle sensor to change the position of the magnetic angle sensor relative to the non-vibrating system of the speaker. It has a sensor placement adjustment means that controls the sensor movable mechanism to adjust the arrangement of the magnetic angle sensor, The characteristic of the correspondence between the displacement of the speaker's vibration system and the magnetic angle is defined as the displacement-magnetic angle characteristic. The sensor placement adjustment means outputs a predetermined test signal to the speaker and measures a displacement-magnetic angle characteristic that shows the relationship between the displacement of the speaker's vibration system, which is expected as a response to the test signal, and the magnetic angle output by the magnetic angle sensor during the output of the test signal. For a pre-configured arrangement of multiple magnetic angle sensors, according to the arrangement-specific characteristic information which registers the correspondence between the arrangement of magnetic angle sensors and the displacement-magnetic angle characteristics, the arrangement of magnetic angle sensors whose correspondence with the measured displacement-magnetic angle characteristic is registered in the arrangement-specific characteristic information is estimated as the current arrangement of magnetic angle sensors. A speaker displacement measurement system characterized by controlling the sensor movable mechanism to adjust the arrangement of the magnetic angle sensors so as to eliminate the discrepancy between the estimated current arrangement of magnetic angle sensors and a predetermined arrangement of sensors.

4. A speaker displacement measurement system according to claim 1, 2, or 3, The speaker displacement measurement system is characterized in that the sensor movable mechanism is capable of moving the held magnetic angle sensor in at least the axial direction of each of the three orthogonal axes fixed to the non-vibrating system of the speaker.

5. A speaker displacement measurement system according to claim 4, The speaker displacement measurement system is characterized in that the sensor movable mechanism is capable of rotatably moving the held magnetic angle sensor around at least one of the three axes.

6. An acoustic system comprising a speaker displacement measurement system according to claim 1, 2, or 3, An acoustic system comprising: a speaker; a sound source device that outputs sound; a displacement conversion means that converts the magnetic angle output by the magnetic angle sensor into the displacement of the speaker's vibration system; and a signal correction means that, referring to the displacement converted by the displacement conversion means, corrects the sound output by the sound source device so as to reduce the output distortion of the speaker and outputs it to the speaker.

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