Acoustic system

Abstract

To provide an "acoustic system" for enlarging a stroke width of a speaker by suppressing a winding width.SOLUTION: In accordance with the displacement of the vibration system, the polarity of the driving of the voice coil VC1 and the voice coil VC1 arranged separately below the electrode VC2 is switched. The polarity of the driving of the VC1 is a first polarity when a part of the VC1 is in the magnetic gap GAP1, and is a second polarity opposite to the first polarity when the part of the VC2 is in the magnetic gap GAP2, and the polarity of the driving of the VC2 is the second polarity when a part of the GAP2 is in the GAP1, and is the first polarity when the part of the ceiling is in the magnetic gap ceiling. The GAP2 is separately arranged below the GAP1, the magnetic fluxes of the GAP1 and the GAP2 are in opposite directions, the winding widths of the VC1 and the VC2 are smaller than the interval between the GAP1 and the GAP2, the upper end of the VC1 enters the before the lower end of the is separated upward from the, and the lower end of the enters the before the lower end of the is separated downward from the. VC1 GAP1 GAP2 GAP2 VC2 VC2 GAP1.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a technique for increasing the stroke width of a speaker that can be effectively controlled to drive it. [Background technology]

[0002] A known technology related to the present invention is one that obtains a constant driving force regardless of the displacement of the speaker's vibration system by arranging two magnetic gaps, an upper magnetic gap and a lower magnetic gap, in which the magnetic flux directions are opposite, an upper voice coil with a winding width L and a lower voice coil with a winding width L whose winding direction is opposite to that of the upper voice coil, so that the sum of the winding widths of the lower part of the upper voice coil in the upper magnetic gap and the upper part of the lower voice coil in the lower magnetic gap is L (for example, Patent Document 1).

[0003] Furthermore, as a technique related to the present invention, a technique for detecting the displacement of a vibration system of a speaker using an acceleration sensor, a velocity sensor, a displacement sensor, or the like is known (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-163495 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-81815 Summary of the Invention [Problem to be solved by the invention]

[0005] Even with a small-diameter speaker, by ensuring a large stroke width, it is possible to reproduce low-pitched sounds like a large-diameter speaker. Furthermore, when increasing the stroke width, it is necessary to increase the winding width (coil length) of the voice coil to prevent the voice coil from displacing to a position where it falls outside the magnetic gap and becomes uncontrollable. However, if the winding width is made larger than the width of the magnetic gap, the driving force acting on the voice coil will be smaller than that of a voice coil whose winding width is approximately the width of the magnetic gap. On the other hand, increasing the input gain of the voice coil can increase the driving force acting on the voice coil, but this will increase power consumption. Furthermore, increasing the winding width increases the weight of the vibration system including the voice coil, which is disadvantageous in terms of output sound pressure, etc.

[0006] Therefore, an object of the present invention is to increase the stroke width of a speaker that can effectively control the drive while suppressing the winding width of the voice coil. [Means for solving the problem]

[0007] To achieve the above object, the present invention provides an audio system including a speaker, the audio system including a displacement detection unit that detects an axial displacement of the speaker's vibration system, and a drive unit that drives the speaker with an audio signal. The speaker includes a first magnetic gap, a second magnetic gap that overlaps the first magnetic gap in the axial direction, and multiple voice coils that are fixed to the vibration system at intervals in the axial direction and positioned within the first and second magnetic gaps in the axial direction. The first magnetic gap propagates magnetic flux in one radial direction of the speaker, and the second magnetic gap propagates magnetic flux in the other radial direction. The axial interval between the first and second magnetic gaps is greater than the winding width of each voice coil. The vibration system is configured so that at least some of the multiple voice coils can vibrate between a position inside the first magnetic gap and a position inside the second magnetic gap. The driving unit drives each voice coil using the audio signal as a driving signal, and drives at least the voice coil whose displacement detected by the displacement detection means indicates that it is located inside the first magnetic gap with a driving signal of a first polarity, and drives the voice coil whose displacement detected by the displacement detection means indicates that it is located inside the second magnetic gap with a driving signal of a second polarity whose polarity is the inverse of the first polarity.

[0008] To achieve the above object, the present invention provides an acoustic system including a speaker, comprising: a displacement detection unit for detecting an axial displacement of the speaker's vibration system; and a drive unit for driving the speaker with an audio signal. The speaker has a first magnetic gap, a second magnetic gap overlapping the first magnetic gap as viewed in the axial direction, and a first voice coil and a second voice coil fixed to the vibration system so as to be located inside the first magnetic gap and the second magnetic gap as viewed in the axial direction. One axial end of the speaker is above and the other is below, and the first magnetic gap is provided above the second magnetic gap at a distance in the axial direction, and the first voice coil is provided above the second voice coil at a distance in the axial direction. The first magnetic gap propagates magnetic flux in one radial direction of the speaker, the second magnetic gap propagates magnetic flux in the other radial direction, and the axial distance between the first magnetic gap and the second magnetic gap is greater than the winding width of the first voice coil and the second voice coil. The vibration system is provided so that at least a portion of the first voice coil and at least a portion of the second voice coil can vibrate between a position inside the first magnetic gap and a position inside the second magnetic gap. The drive unit drives the first voice coil with a drive signal of a first polarity when the displacement detected by the displacement detection means indicates that at least a predetermined percentage of the first voice coil is located inside the first magnetic gap, drives the first voice coil with a drive signal of a second polarity that is the opposite polarity to the first polarity when the displacement detected by the displacement detection means indicates that at least a predetermined percentage of the first voice coil is located inside the second magnetic gap, drives the second voice coil with a drive signal of the first polarity when the displacement detected by the displacement detection means indicates that at least a predetermined percentage of the second voice coil is located inside the first magnetic gap, and drives the second voice coil with a drive signal of the second polarity when the displacement detected by the displacement detection means indicates that at least a predetermined percentage of the second voice coil is located inside the second magnetic gap.

[0009] Here, such an acoustic system is preferably configured so that, in a first range of displacement of the vibration system, both a portion of the first voice coil that is equal to or greater than a predetermined percentage and a portion of the second voice coil that is equal to or greater than a predetermined percentage are inside the first magnetic gap, and so that, in a second range of displacement of the vibration system, both a portion of the first voice coil that is equal to or greater than a predetermined percentage and a portion of the second voice coil that is equal to or greater than a small predetermined percentage are inside the second magnetic gap, and so that, in the driving unit, when the displacement detected by the displacement detection means indicates that both a portion of the first voice coil that is equal to or greater than a predetermined percentage and a portion of the second voice coil that is equal to or greater than a predetermined percentage are located inside the first magnetic gap, the driving unit drives both the first voice coil and the second voice coil with a drive signal of the first polarity, and when the displacement detected by the displacement detection means indicates that both a portion of the first voice coil that is equal to or greater than a predetermined percentage and a portion of the second voice coil that is equal to or greater than a predetermined percentage are located inside the second magnetic gap.

[0010] In this case, the drive unit may stop driving the first voice coil when the displacement detected by the displacement detection means indicates that a portion of the first voice coil equal to or greater than the predetermined percentage is not located inside either the first magnetic gap or the second magnetic gap, and may stop driving the second voice coil when the displacement detected by the displacement detection means indicates that a portion of the second voice coil equal to or greater than the predetermined percentage is not located inside either the first magnetic gap or the second magnetic gap.

[0011] Here, the portion of the first voice coil that is greater than a predetermined percentage may be n% (where n>0) or more of the first voice coil, and the portion of the second voice coil that is greater than a predetermined percentage may be n% or more of the second voice coil. Furthermore, the above acoustic system may be configured such that when the upper half of the first voice coil is located within the lower part of the first gap, the lower half of the second voice coil is located within the upper part of the second gap. More specifically, for example, the winding width of the first voice coil and the second voice coil may be L, and the distance between the first voice coil and the second voice coil in the axial direction may be 0.5L. In this case, it is preferable that the length of the first magnetic gap and the second magnetic gap in the axial direction is 1.5L. According to the above-described acoustic system, at least some of the voice coils provided with multiple voice coils having different axial ranges can be selectively acted on both the first magnetic gap and the second magnetic gap, which have different axial ranges and opposite magnetic flux directions, to drive the speaker. This makes it possible to maintain the driving force over a wide displacement range of the vibration system while reducing the winding width of the voice coil, and as a result, it is possible to expand the stroke width of the speaker, over which driving can be effectively controlled. [Effects of the Invention]

[0012] As described above, according to the present invention, it is possible to increase the stroke width of a speaker that can effectively control the drive while reducing the winding width of the voice coil. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram showing a configuration of an audio system according to an embodiment of the present invention. [Figure 2] 1 is a diagram showing a configuration of a speaker according to an embodiment of the present invention; [Figure 3] FIG. 2 is a diagram showing the positional relationship between a magnetic gap and a voice coil according to an embodiment of the present invention. [Figure 4] FIG. 4 is a diagram illustrating a drive control of a voice coil according to an embodiment of the present invention. [Figure 5] 10A and 10B are diagrams illustrating another example of the drive control of the voice coil according to the embodiment of the present invention. [Figure 6]10A and 10B are diagrams illustrating another configuration example of the speaker according to the embodiment of the present invention. [Figure 7] FIG. 10 is a diagram illustrating another exemplary configuration of an acoustic system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described. FIG. 1 shows the configuration of an audio system according to this embodiment. As shown in the figure, the acoustic system includes a sound source device 1 that outputs an audio signal, a speaker 2, a displacement sensor 3 provided in the speaker 2, a signal processing device 4, a first amplifier 5, and a second amplifier 6. The signal processing device 4 can be configured, for example, using a DSP (Digital Signal Processor), and includes a first gain adjustment unit 41, a second gain adjustment unit 42, a first drive polarity control unit 43, a second drive polarity control unit 44, a displacement detection unit 45, and a control unit 46. Next, FIG. 2a shows the configuration of the speaker 2. As shown in the figure, the speaker 2 has a base 201, a yoke 202, a voice coil bobbin 203, a dust cap 204, a first voice coil VC1 (205), a second voice coil VC2 (206), a first plate 207, a second plate 208, a magnet 209, a frame 210, a damper 211, a diaphragm 212, and a displacement detection magnet 213.

[0015] Now, assuming that the upward direction in the axial direction of the speaker 2 in the drawing is the upward direction of the speaker 2 and the downward direction is the downward direction of the speaker 2, the yoke 202 has a cylindrical shape and is supported at the center of the base 201. The voice coil bobbin 203 has a hollow cylindrical shape, and the yoke 202 is inserted into the hollow of the voice coil bobbin 203 from below so that the voice coil bobbin 203 is movable up and down relative to the yoke 202. A first voice coil VC1 (205) is wound around the outer periphery of the voice coil bobbin 203, and a second voice coil VC2 (206) is wound at a position spaced below the first voice coil VC1 (205).

[0016] In addition, on the outside of the voice coil bobbin 203, an annular second plate 208 supported on the outer periphery of the base 201, an annular magnet 209, and an annular first plate 207 are stacked in that order from below. Here, the yoke 202 and the second plate 208 are electrically and magnetically separated by the base 201, and the yoke 202, the second plate 208, the magnet 209, and the first plate 207 form a magnetic circuit in which magnetism circulates: magnet 209 - second plate 208 - yoke 202 - first plate 207 - magnet 209.

[0017] The frame 210 is fixed to the base 201 via the yoke 202, the first plate 207, the magnet 209, and the second plate 208, and the diaphragm 212 has its outer peripheral end fixed to the frame 210 and its inner peripheral end fixed to the voice coil bobbin 203. Next, displacement detection magnet 213 is fixed to the outer periphery of voice coil bobbin 203 so as to move up and down together with voice coil bobbin 203, and generates a magnetic flux in a direction perpendicular to the magnetic flux generated by the magnetic circuit. The displacement sensor 3 described above is fixed to a position close to the displacement detecting magnet 213 in a non-vibration system of the speaker 2, such as the first plate 207. The displacement sensor 3 is a magnetic angle sensor, and as shown in FIG. 2b, it detects and outputs the arctangent Qs / Qc of the angle of the resultant vector Q of the magnetic flux vector Qc acting from the magnetic circuit and the magnetic flux vector Qs acting from the displacement detecting magnet 211 as a magnetic angle. The magnetic flux vector generated by the displacement detecting magnet 213 acting on the displacement sensor 3 changes due to the displacement of the displacement detecting magnet 213 accompanying the vertical displacement of the voice coil bobbin 203, so this magnetic angle is a value according to the vertical displacement amount of the voice coil bobbin 203, and therefore the vertical displacement position of the vibration system of the speaker 2.

[0018] Here, FIG. 3a shows the positional relationship between the yoke 202, the first voice coil VC1 (205), the second voice coil VC2 (206), the first plate 207, the second plate 208, and the magnet 209. As shown in Fig. 3b, a first magnetic gap GAP1 through which magnetic flux passes is formed between first plate 207 and yoke 202, and a second magnetic gap GAP2 through which magnetic flux passes is formed between second plate 208 and yoke 202. In addition, as shown in Fig. 3c, the direction of the magnetic flux passing through first magnetic gap GAP1 and the direction of the magnetic flux passing through second magnetic gap GAP2 are opposite to each other in the radial direction of speaker 2.

[0019] The winding width (coil length / height in the vertical direction) of the first voice coil VC1 (205) and the second voice coil VC2 (206) is equal. Furthermore, the winding width of the first voice coil VC1 (205) and the second voice coil VC2 (206) is L, and the distance between the first magnetic gap GAP1 and the second magnetic gap GAP2 is set to be larger than L so that the first voice coil VC1 (205) or the second voice coil VC2 (206) does not enter both the first magnetic gap GAP1 and the second magnetic gap GAP2 at the same time. In addition, the size and arrangement of each part are determined so that the voice coil bobbin 203 moves upward and the upper end of the second voice coil VC2 (206) enters the first magnetic gap GAP1 before the lower end of the first voice coil VC1 (205) moves upward away from the first magnetic gap GAP1, and the voice coil bobbin 203 moves downward and the lower end of the first voice coil VC1 (205) enters the second magnetic gap GAP2 before the lower end of the second voice coil VC2 (206) moves downward away from the second magnetic gap GAP2.

[0020] Here, in this embodiment, an example is shown in which the vertical width of the first magnetic gap GAP is 1.5L, the vertical width of the second magnetic gap GAP2 is 1.5L, the vertical width of the space between the first magnetic gap GAP1 and the second magnetic gap GAP2 is 1.5L, and the vertical space between the first voice coil VC1 (205) and the second voice coil VC2 (206) is 0.5L.

[0021] In this embodiment, in a neutral state in which no signal is applied to the first voice coil VC1 (205) and the second voice coil VC2 (206), the first voice coil VC1 (205) and the second voice coil VC2 (206) are arranged so that the upper half of the first voice coil VC1 (205) is located at the bottom within the first magnetic gap GAP1, and the lower half of the second voice coil VC2 (206) is located at the top within the second magnetic gap GAP2.

[0022] Next, assuming that the direction of the current flowing from the front to the back of the paper in Fig. 3 (toward the rear) is the forward direction and the direction of the current flowing from the back to the front of the paper in Fig. 3 (toward the front) is the reverse direction, if the directions of the magnetic flux passing through the first magnetic gap GAP1 and the magnetic flux passing through the second magnetic gap GAP2 are as shown in Fig. 3c, when at least a part of the first voice coil VC1 (205) is located within the first magnetic gap GAP1, as shown in Fig. 3d1, if a forward current flows through the first voice coil VC1 (205), an upward force is applied to the voice coil bobbin 203. Similarly, as shown in Fig. 3d2, when at least a part of the second voice coil VC2 (206) is located within the first magnetic gap GAP1, if a forward current flows through the second voice coil VC2 (206), an upward force is applied to the voice coil bobbin 203. On the other hand, as shown in Fig. 3d3, when at least a portion of the first voice coil VC1 (205) is located within the second magnetic gap GAP2, if a reverse current flows through the first voice coil VC1 (205), an upward force is applied to the voice coil bobbin 203. Similarly, when at least a portion of the second voice coil VC2 (206) is located within the second magnetic gap GAP2, as shown in Fig. 3d4, if a reverse current flows through the second voice coil VC2 (206), an upward force is applied to the voice coil bobbin 203. Furthermore, when the direction of the current is reversed, forces in the opposite directions are applied to the voice coil bobbin 203.

[0023] Therefore, as long as at least a portion of at least one of the first voice coil VC1 (205) and the second voice coil VC2 (206) is located within at least one of the first magnetic gap GAP1 and the second magnetic gap GAP2, by applying an audio signal with appropriate polarity and gain to the first voice coil VC1 (205) or the second voice coil VC2 (206), the electromagnetic interaction between the magnetic flux generated in the first magnetic gap GAP1 or the second magnetic gap GAP2 and the current flowing through the first voice coil VC1 (205) or the second voice coil VC2 (206) can cause the diaphragm 212 to vibrate according to the amplitude of the audio signal via the voice coil bobbin 203, thereby generating sound according to the audio signal.

[0024] Returning to FIG. 1, the displacement detection unit 45 of the signal processing device 4 calculates the vertical displacement position ΔZ of the vibration system of the speaker 2 from the magnetic angle detected by the displacement sensor 3 and outputs it to the control unit 46. In addition, the first gain adjustment unit 41 adjusts the gain of the audio signal input from the sound source device 1 using the gain set by the control unit 46 and outputs the result to the first drive polarity control unit 43, and the second gain adjustment unit 42 adjusts the gain of the audio signal input from the sound source device 1 using the gain set by the control unit 46 and outputs the result to the second drive polarity control unit 44.

[0025] The first drive polarity control unit 43 outputs the audio signal input from the first gain adjustment unit 41 to the first amplifier 5, and also performs a process of switching between whether or not to output the audio signal to the first amplifier 5 under the control of the control unit 46, and a process of switching between the positive and negative polarities of the audio signal output to the first amplifier 5 under the control of the control unit 46. Similarly, the second drive polarity control unit 44 outputs the audio signal input from the second gain adjustment unit 42 to the second amplifier 6, and also performs a process of switching between whether or not to output the audio signal to the second amplifier 6 under the control of the control unit 46, and a process of switching between the positive and negative polarities of the audio signal output to the second amplifier 6 under the control of the control unit 46.

[0026] The first amplifier 5 amplifies the audio signal input from the first drive polarity control unit 43 with a predetermined fixed gain and outputs the amplified signal to the first voice coil VC2 of the speaker 2, and the second amplifier 6 amplifies the audio signal input from the second drive polarity control unit 44 with the same gain as the first amplifier 5 and outputs the amplified signal to the second voice coil VC2 (206) of the speaker 2.

[0027] The control of the first drive polarity control unit 43 and the second drive polarity control unit 44 performed by the control unit 46 will be described below. The control unit 46 controls the first drive polarity control unit 43 and the second drive polarity control unit 44 to switch between output and non-output and the positive / negative polarity of the audio signal to be output, depending on the vertical displacement position ΔZ of the vibration system of the speaker 2 calculated by the displacement detection unit 45. 4a shows the positional relationship between the displacement position ΔZ, the first voice coil VC1 (205), the second voice coil VC2 (206), the first magnetic gap GAP1, and the second magnetic gap GAP2. Also, FIG. 4b1 shows the relationship between the displacement position ΔZ, whether the first drive polarity control unit 43 outputs to the first amplifier 5, and the positive / negative polarity of the audio signal output to the first amplifier 5. The positive / negative polarity of the audio signal output to the first amplifier 5 is indicated by the direction of the current flowing through the first voice coil VC1 (205) when the value of the audio signal input to the first drive polarity control unit 43 is positive. Also, FIG. 4b2 shows the relationship between the displacement position ΔZ, whether the second drive polarity control unit 44 outputs to the second amplifier 6, and the positive / negative polarity of the audio signal output to the second amplifier 6. However, the positive or negative polarity of the audio signal output to the second amplifier 6 is indicated by the direction of the current flowing through the second voice coil VC2 (206) when the value of the audio signal input to the second drive polarity control unit 44 is positive.

[0028] The direction of the current flowing through the first voice coil VC1 (205) and the second voice coil VC2 (206) is indicated by the forward direction / reverse direction shown in FIGS. 3d1-d4. As shown in the figure, the control unit 46 controls the output of the first drive polarity control unit 43 to the first amplifier 5 so as to stop output to the first amplifier 5 when the entire first voice coil VC1 (205) is neither within the first magnetic gap GAP1 nor within the second magnetic gap GAP2. In addition, the control unit 46 controls the positive and negative polarities of the audio signal that the first drive polarity control unit 43 outputs to the first amplifier 5 so that when at least a portion of the first voice coil VC1 (205) is within the first magnetic gap GAP1, current flows in the forward direction through the first voice coil VC1 (205) when the value of the audio signal input to the first drive polarity control unit 43 is positive, and when at least a portion of the first voice coil VC1 (205) is within the second magnetic gap GAP2, current flows in the reverse direction through the first voice coil VC1 (205) when the value of the audio signal input to the first drive polarity control unit 43 is positive.

[0029] In addition, the control unit 46 controls the output of the second drive polarity control unit 44 to the second amplifier 6 so as to stop output to the second amplifier 6 when the entire second voice coil VC2 (206) is neither within the second magnetic gap GAP2 nor within the first magnetic gap GAP1. In addition, the control unit 46 controls the positive / negative polarity of the audio signal that the second drive polarity control unit 44 outputs to the second amplifier 6 so that when at least a portion of the second voice coil VC2 (206) is within the second magnetic gap GAP2, current flows in the reverse direction through the second voice coil VC2 (206) when the value of the audio signal input to the second drive polarity control unit 44 is positive, and when at least a portion of the second voice coil VC2 (206) is within the first magnetic gap GAP1, current flows in the forward direction through the second voice coil VC2 (206) when the value of the audio signal input to the second drive polarity control unit 44 is positive. As a result, when the displacement position ΔZ is within the range BZ in Figure 4a, which is the range between the position where the upper end of the first voice coil VC1 (205) is the lower end of the second magnetic gap GAP2 and the position where the lower end of the second voice coil VC2 (206) is the upper end of the first magnetic gap GAP1, at least a portion of at least one of the first voice coil VC1 (205) and the second voice coil VC2 (206) is within at least one of the first magnetic gap GAP1 and the second magnetic gap GAP2, a driving force can be exerted by at least one of the first voice coil VC1 (205) and the second voice coil VC2 (206).Furthermore, within this range of BZ, by the control of the control unit 46 shown in Figures 4b1 and 4b2, a force can be applied to the voice coil bobbin 203 in a direction appropriate to the positive and negative of the audio signal output by the sound source device 1, thereby vibrating the vibration system of the speaker 2.

[0030] Here, if only the first magnetic gap GAP1 is provided as the magnetic gap and a single voice coil is used to exert driving force within the range of BZ, a voice coil VCL is required with a winding width equal to the length from the upper end of the first voice coil VC1 (205) to the lower end of the second voice coil VC2 (206), which exceeds the sum of the winding widths of the first voice coil VC1 (205) and the second voice coil VC2 (206), 2L, as shown in Figure 4c.

[0031] Therefore, according to this embodiment, it is possible to increase the stroke width of the speaker 2, which allows for effective drive control, without using a voice coil with a large winding width. Also, since the magnetic circuit structure is symmetrical between the top and bottom, asymmetric distortion is less likely to occur. Returning to FIG. 1, the control unit 46 controls the gain of the first gain adjustment unit 41 and the gain of the second gain adjustment unit 42 in accordance with a preset correspondence between the displacement position ΔZ and the combination of the gain of the first gain adjustment unit 41 and the gain of the second gain adjustment unit 42 so that a target response of the driving force of the vibration system by the first voice coil VC1 (205) and the second voice coil VC2 (206) is obtained in response to the audio signal output by the sound source device 1 in the above configuration.

[0032] The correspondence between the displacement position ΔZ and the combination of the gain of the first gain adjustment unit 41 and the gain of the second gain adjustment unit 42 is determined so that the upper and lower limits of the displacement position ΔZ for the audio signal output by the expected sound source device 1 fall within the range BZ. The embodiments of the present invention have been described above. In the above embodiment, the first voice coil VC1 (205) is driven when at least a part of the first voice coil VC1 (205) is in the first magnetic gap GAP1 or the second magnetic gap GAP2, and the second voice coil VC2 (206) is driven when at least a part of the second voice coil VC2 (206) is in the first magnetic gap GAP1 or the second magnetic gap GAP2. However, when the first voice coil VC1 (205) has a predetermined winding width (for example, When a portion of the first voice coil VC1 (205) that is 10% or more of the winding width is not within the first magnetic gap GAP1 or the second magnetic gap GAP2, the output to the first voice coil VC1 (205) may be stopped, and when a portion of the second voice coil VC2 (206) that is 10% or more of the winding width of a predetermined length (for example, 10% of the winding width of the second voice coil VC2 (206)) is not within the first magnetic gap GAP1 or the second magnetic gap GAP2, the output to the second voice coil VC2 (206) may be stopped.

[0033] Furthermore, in the above embodiments, the control unit 46 may perform control to limit the range of the displacement position ΔZ of the vibration system so that the sum of the ranges of the first voice coil VC1 (205) and the second voice coil VC2 (206) within either the first magnetic gap GAP1 or the second magnetic gap GAP2 does not deviate from a range that is equal to or greater than a predetermined width (vertical length).

[0034] That is, for example, as shown in FIG. 5a, over-amplitude protection control may be performed to control the displacement position ΔZ so that it does not deviate from the range CZ between the position where the lower end of the first voice coil VC1 (205) becomes the lower end of the second magnetic gap GAP2 and the position where the upper end of the second voice coil VC2 (206) becomes the upper end of the first magnetic gap GAP1, so that the total range of the first voice coil VC1 (205) and the second voice coil VC2 (206) within either the first magnetic gap GAP1 or the second magnetic gap GAP2 is equal to or greater than L.

[0035] In this case, the correspondence between the displacement position ΔZ and the combination of the gain of the first gain adjustment unit 41 and the gain of the second gain adjustment unit 42 is determined so that the upper and lower limits of the response of the displacement position ΔZ to the audio signal output by the expected sound source device 1 fall within the range CZ. 5a, by limiting the range of the displacement position ΔZ to the range CZ, the total range of the first voice coil VC1 (205) and the second voice coil VC2 (206) within either the first magnetic gap GAP1 or the second magnetic gap GAP2 within the range CZ is always L. Therefore, the range in which the magnitude of the magnetic flux passing through the first voice coil VC1 (205) and the second voice coil VC2 (206) is linear is expanded, and the same driving force can be realized over a wide range.

[0036] In this case, the over-amplitude protection control can be realized by the control unit 46 performing the control shown in Figs. 5b1 and 5b2, for example. That is, the control unit 46 controls the positive / negative polarity of the audio signal that the first drive polarity control unit 43 outputs to the first amplifier 5 so that, between the position where the lower end of the first voice coil VC1 (205) is the upper end of the first magnetic gap GAP1 and the position where the upper end of the first voice coil VC1 (205) is the lower end of the first magnetic gap GAP1, when the value of the audio signal input to the first drive polarity control unit 43 is positive, a current flows in the forward direction through the first voice coil VC1 (205). Between the position where the upper end of the gap GAP2 is located and the position where the lower end of the first voice coil VC1 (205) is located at the lower end of the second magnetic gap GAP2, the first drive polarity control unit 43 controls the positive / negative polarity of the audio signal that it outputs to the first amplifier 5 so that when the value of the audio signal input to the first drive polarity control unit 43 is positive, current flows in the opposite direction to the first voice coil VC1 (205), and in the range of other positions within the range CZ, the first drive polarity control unit 43 controls the output to the first amplifier 5 so that the output to the first amplifier 5 is stopped.

[0037] Furthermore, the control unit 46 controls the polarity of the audio signal that the second drive polarity control unit 44 outputs to the second amplifier 6 so that, between a position where the upper end of the second voice coil VC2 (206) is the lower end of the second magnetic gap GAP2 and a position where the lower end of the second voice coil VC2 (206) is the upper end of the second magnetic gap GAP2, when the value of the audio signal input to the second drive polarity control unit 44 is positive, a current flows in the opposite direction to the first voice coil VC1 (205). Between the position where the lower end of the gap GAP1 is located and the position where the upper end of the second voice coil VC2 (206) is located at the upper end of the first magnetic gap GAP1, the second drive polarity control unit 44 controls the positive / negative polarity of the audio signal to be output to the second amplifier 6 so that current flows in the forward direction through the first voice coil VC1 (205) when the value of the audio signal input to the first drive polarity control unit 43 is positive, and controls the output of the second drive polarity control unit 44 to the second amplifier 6 so that the output to the second amplifier 6 is stopped in the range of other positions within the range CZ.

[0038] In addition, the over-amplitude suppression operation is performed in a range where the displacement position ΔZ is larger than the range CZ and a range where it is smaller than the range CZ. In the range where the displacement position ΔZ is larger than the range CZ, the second drive polarity control unit 44 is caused to generate a brake signal that applies a driving force to the second voice coil VC2 (206) in the opposite direction to the displacement direction indicated by the displacement position ΔZ, and this brake signal is output to the second amplifier 6 in place of an audio signal. In the range where the displacement position ΔZ is smaller than the range CZ, the first drive polarity control unit 43 is caused to generate a brake signal that applies a driving force to the first voice coil VC1 (205) in the opposite direction to the displacement direction indicated by the displacement position ΔZ, and this brake signal is output to the first amplifier 5 in place of an audio signal.

[0039] Furthermore, in the above embodiment, the case where two voice coils, the first voice coil VC1 (205) and the second voice coil VC2 (206), are used as voice coils has been described, but a greater number of voice coils may be provided.

[0040] For example, four voice coils VC1-VC4 may be arranged on the voice coil bobbin 203 as shown in FIG. 6a1. According to the arrangement shown in FIG. 6a1, in the stroke range between FIG. 6a2 and FIG. 6a3, the total winding width of all voice coils in either the first magnetic gap GAP1 or the second magnetic gap GAP2 can be set to be equal to or greater than L, thereby vibrating the vibration system of the speaker 2.

[0041] Alternatively, for example, five voice coils VC1-VC5 may be arranged on the voice coil bobbin 203 as shown in FIG. 6b1. According to the configuration shown in FIG. 6b1, in the stroke range between FIG. 6b2 and FIG. 6b3, the total winding width of all voice coils in either the first magnetic gap GAP1 or the second magnetic gap GAP2 can be set to be equal to or greater than L, and the vibration system of the speaker 2 can be vibrated. 6a1 and 6b1 show a case where the vertical width of the first magnetic gap GAP is 1.5L, the vertical width of the second magnetic gap GAP2 is 1.5L, the vertical width of the space between the first magnetic gap GAP1 and the second magnetic gap GAP2 is 1.5L, and the vertical space between adjacent voice coils VC is 0.5L. Here, with this configuration, the same voice coil VCi (i=1, 2, ... n) will not enter both the first magnetic gap GAP1 and the second magnetic gap GAP2 at the same time. Furthermore, as the voice coil bobbin 203 moves upward, the upper end of the k+1th voice coil VCk+1 enters the first magnetic gap GAP1 before the lower end of the kth voice coil VCk (k=1, 2, ..., n-1) moves upward away from the first magnetic gap GAP1, and as the voice coil bobbin 203 moves downward, the lower end of the j-1st voice coil VCj-1 enters the second magnetic gap GAP2 before the lower end of the jth voice coil VCj (j=2, 3, ..., n) moves downward away from the second magnetic gap GAP2.

[0042] Now, when a larger number n of voice coils are provided as in Figures 6a1 and 6b1, a set of an ith gain control unit GCi, an ith drive polarity control unit DPCi, and an ith amplifier AMPi corresponding to each voice coil VCi (i = 1, 2, ... n) is provided as shown in Figure 7, and the ith drive polarity control unit controls the output of the audio signal to the ith amplifier so that the output to the voice coil VCi via the ith amplifier AMPi is stopped when the entire voice coil VCi is not within either the first magnetic gap GAP1 or the second magnetic gap GAP2. In addition, when at least a portion of the voice coil VCi is within the first magnetic gap GAP1, the i-th drive polarity control unit controls the positive / negative polarity of the audio signal output to the i-th amplifier AMPi so that when the value of the audio signal input to the first drive polarity control unit 43 is positive, a current flows in the forward direction through the first voice coil VC1 (205), and when at least a portion of the first voice coil VCi is within the second magnetic gap GAP2, a current flows in the reverse direction through the i-th voice coil VCi when the value of the audio signal input to the i-th drive polarity control unit is positive. [Explanation of symbols]

[0043] 1...sound source device, 2...speaker, 3...displacement sensor, 4...signal processing device, 5...first amplifier, 6...second amplifier, 41...first gain adjustment unit, 42...second gain adjustment unit, 43...first drive polarity control unit, 44...second drive polarity control unit, 45...displacement detection unit, 46...control unit, 201...base, 202...yoke, 203...voice coil bobbin, 204...dust cap, 205...first voice coil VC1, 206...second voice coil VC2, 207...first plate, 208...second plate, 209...magnet, 210...frame, 211...damper, 212...diaphragm, 213...displacement detection magnet.

Claims

1. An audio system having a speaker, a displacement detection means for detecting a displacement of the vibration system of the speaker in the axial direction of the speaker; a driver that drives the speaker with an audio signal; The speaker includes: a first magnetic gap; and a second magnetic gap overlapping the first magnetic gap when viewed in the axial direction; a plurality of voice coils fixed to the vibration system at intervals in the axial direction so as to be located inside the first magnetic gap and the second magnetic gap as viewed in the axial direction; the first magnetic gap propagates magnetic flux in one radial direction of the speaker, and the second magnetic gap propagates magnetic flux in the other radial direction; the axial distance between the first magnetic gap and the second magnetic gap is greater than the winding width of each voice coil; the vibration system is provided so that at least some of the voice coils among the plurality of voice coils can vibrate between a position inside the first magnetic gap and a position inside the second magnetic gap, The driving unit drives each voice coil using the audio signal as a driving signal, and drives at least the voice coil whose displacement detected by the displacement detection means indicates that it is located inside the first magnetic gap with a driving signal of a first polarity, and drives the voice coil whose displacement detected by the displacement detection means indicates that it is located inside the second magnetic gap with a driving signal of a second polarity whose polarity is opposite to the first polarity.

2. An audio system having a speaker, a displacement detection means for detecting a displacement of the vibration system of the speaker in the axial direction of the speaker; a driver that drives the speaker with an audio signal; The speaker includes: a first magnetic gap; and a second magnetic gap overlapping the first magnetic gap when viewed in the axial direction; a first voice coil and a second voice coil fixed to the vibration system so as to be located inside the first magnetic gap and the second magnetic gap when viewed in the axial direction; one axial direction of the speaker is defined as an upper side and the other axial direction is defined as a lower side, and the first magnetic gap is provided above the second magnetic gap at a distance in the axial direction, the first voice coil is provided above the second voice coil at a distance in the axial direction, the first magnetic gap propagates magnetic flux in one radial direction of the speaker, and the second magnetic gap propagates magnetic flux in the other radial direction; the axial distance between the first magnetic gap and the second magnetic gap is greater than the winding width of the first voice coil and the second voice coil; the vibration system is provided so that at least a portion of the first voice coil and at least a portion of the second voice coil can vibrate between a position inside the first magnetic gap and a position inside the second magnetic gap, The drive unit is When the displacement detected by the displacement detection means indicates that at least a predetermined percentage or more of the first voice coil is located inside the first magnetic gap, the first voice coil is driven with a drive signal of a first polarity, and when the displacement detected by the displacement detection means indicates that at least a predetermined percentage or more of the first voice coil is located inside the second magnetic gap, the first voice coil is driven with a drive signal of a second polarity that is the opposite polarity to the first polarity, an acoustic system characterized in that the second voice coil is driven with a drive signal of the first polarity when the displacement detected by the displacement detection means indicates that at least a predetermined percentage or more of the second voice coil is located inside the first magnetic gap, and the second voice coil is driven with drive signals of the first polarity and the second polarity when the displacement detected by the displacement detection means indicates that at least a predetermined percentage or more of the second voice coil is located inside the second magnetic gap.

3. 3. The acoustic system of claim 2, In a first range of displacement of the vibration system, both a portion of the first voice coil of a predetermined percentage or more and a portion of the second voice coil of a predetermined percentage or more are inside the first magnetic gap, and in a second range of displacement of the vibration system, both a portion of the first voice coil of a predetermined percentage or more and a portion of the second voice coil of a small predetermined percentage or more are inside the second magnetic gap, the driving unit drives both the first voice coil and the second voice coil with a drive signal of the first polarity when the displacement detected by the displacement detection means indicates that both a portion of the first voice coil that is equal to or greater than a predetermined percentage and a portion of the second voice coil that is equal to or greater than a predetermined percentage are located inside the first magnetic gap, and drives both the first voice coil and the second voice coil with a drive signal of the second polarity when the displacement detected by the displacement detection means indicates that both a portion of the first voice coil that is equal to or greater than a predetermined percentage and a portion of the second voice coil that is equal to or greater than a predetermined percentage are located inside the second magnetic gap.

4. 4. The acoustic system of claim 3, an acoustic system characterized in that the driving unit stops driving the first voice coil when the displacement detected by the displacement detection means indicates that a portion of the first voice coil equal to or greater than the predetermined percentage is not located inside either the first magnetic gap or the second magnetic gap, and stops driving the second voice coil when the displacement detected by the displacement detection means indicates that a portion of the second voice coil equal to or greater than the predetermined percentage is not located inside either the first magnetic gap or the second magnetic gap.

5. 5. An acoustic system according to claim 2, 3 or 4, An acoustic system characterized in that a portion of the first voice coil that is equal to or greater than a predetermined percentage is equal to or greater than n% (where n > 0) of the first voice coil, and a portion of the second voice coil that is equal to or greater than a predetermined percentage is equal to or greater than n% of the second voice coil.

6. 3. The acoustic system of claim 2, 1. An acoustic system, comprising: a first voice coil having a first upper half located within a first gap; a second voice coil having a second lower half located within a second gap;

7. 7. The acoustic system of claim 6, An acoustic system characterized in that the winding width of the first voice coil and the second voice coil is L, and the axial distance between the first voice coil and the second voice coil is 0.5L.

8. 8. The acoustic system of claim 7, An acoustic system characterized in that the axial length of the first magnetic gap and the second magnetic gap is 1.5L.

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