Sound system

Abstract

This system provides an acoustic mechanism that expands the speaker stroke width, allowing for effective drive control while keeping the voice coil winding width low. [Solution] The speaker estimates the displacement of the vibration system from the magnitude of the audio signal and switches the drive polarity of the first voice coil (VC1) and the second voice coil (VC2) located below the first voice coil according to the estimation. The drive polarity of VC1 is such that when a part of VC1 is in the magnetic gap GAP1, current flows in the first direction, and when it is in the second magnetic gap GAP2, current flows in the second direction opposite to the first direction. The drive polarity of VC2 is such that when a part of VC2 is in the second magnetic gap, current flows in the second direction, and when it is in the first magnetic gap, current flows in the first direction. The second magnetic gap is spaced below the first magnetic gap, the direction of the magnetic flux is opposite, and the winding widths of VC1 and VC2 are smaller than the distance between the first and second magnetic gaps.

Description

Technical Field

[0001] The present invention relates to a technique for expanding the stroke width of a speaker capable of effectively controlling driving.

Background Art

[0002] As a technique related to the present invention, there are two magnetic gaps, an upper magnetic gap and a lower magnetic gap, in which the directions of magnetic fluxes are opposite to each other, and an upper voice coil with a winding width (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 are provided such 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, so that a constant driving force can be obtained regardless of the displacement of the vibration system of the speaker (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Even a small-diameter speaker can reproduce bass like a large-diameter speaker by securing a large stroke width. When increasing the stroke width, it is necessary to increase the winding width so that the voice coil does not displace to a position outside the magnetic gap and become uncontrollable. However, when the winding width is increased, the driving force acting on the voice coil becomes smaller than that of a voice coil whose winding width is about the width of the magnetic gap. On the other hand, if the gain of the input to the voice coil is increased, the driving force acting on the voice coil can be increased, but in this case, power consumption increases. Further, when the winding width is increased, the weight of the vibration system including the voice coil increases, which is disadvantageous in terms of output sound pressure and the like.

[0005] Therefore, the present invention aims to increase the stroke width of a speaker that can effectively control its drive while suppressing the winding width of the voice coil. [Means for solving the problem]

[0006] To achieve the above objectives, the present invention provides an acoustic system comprising a speaker, a drive unit that drives the speaker with a drive signal obtained by signal processing of an input audio signal, and a displacement estimation means. The speaker has a first magnetic gap, a second magnetic gap that overlaps the first magnetic gap when viewed in the axial direction of the speaker, and a first voice coil and a second voice coil fixed to the vibrating system of the speaker that vibrates in the axial direction, so as to be located inside the first magnetic gap and the second magnetic gap when viewed in the axial direction. With one of the axial directions being upward and the other downward, the first magnetic gap is provided above the second magnetic gap at an axial distance, the first voice coil is provided above the second voice coil at an axial distance, the first magnetic gap propagates magnetic flux in one of the radial directions of the speaker, 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 widths of the first and second voice coils, and the vibration system is provided so as to be able to vibrate between a position where at least a portion of the first voice coil and at least a portion of the second voice coil are inside the first magnetic gap and a position where they are inside the second magnetic gap.

[0007] Furthermore, the displacement estimation unit estimates the axial positions of the first voice coil and the second voice coil of the speaker from the magnitude of the input audio signal. The drive unit drives the first voice coil with a drive signal of polarity such that the direction of the current flowing through the first voice coil in response to a positive audio signal is in a first direction when the position estimated by the displacement estimation means is a position where at least a predetermined proportion of the first voice coil is inside the first magnetic gap; drives the first voice coil with a drive signal of polarity such that the direction of the current flowing through the first voice coil in response to a positive audio signal is in a second direction opposite to the first direction when the position estimated by the displacement estimation means is a position where at least a predetermined proportion of the second voice coil is inside the first magnetic gap; drives the second voice coil with a drive signal of polarity such that the direction of the current flowing through the second voice coil in response to a positive audio signal is in a first direction when the position estimated by the displacement estimation means is a position where at least a predetermined proportion of the second voice coil is inside the first magnetic gap; and drives the second voice coil with a drive signal of polarity such that the direction of the current flowing through the second voice coil in response to a positive audio signal is in a second direction when at least a predetermined proportion of the second voice coil is inside the second magnetic gap.

[0008] In this acoustic system, if, within a first range of displacement of the vibration system, both a predetermined proportion or more of the first voice coil and a predetermined proportion or more of the second voice coil are inside the first magnetic gap, and within a second range of displacement of the vibration system, both a predetermined proportion or more of the first voice coil and a slightly predetermined proportion or more of the second voice coil are inside the second magnetic gap, the drive unit may drive both the first voice coil and the second voice coil with a drive signal of polarity such that the direction of the current flowing with respect to a positive audio signal is the first direction when the position estimated by the displacement estimation means is a position where both a predetermined proportion or more of the first voice coil and a predetermined proportion or more of the second voice coil are inside the first magnetic gap, and drive both the first voice coil and the second voice coil with a drive signal of polarity such that the direction of the current flowing with respect to a positive audio signal is the second direction when the position estimated by the displacement estimation means is a position where both a predetermined proportion or more of the first voice coil and a predetermined proportion or more of the second voice coil are inside the second magnetic gap.

[0009] In this case, the drive unit may stop driving the first voice coil when the position estimated by the displacement estimation means is such that a predetermined percentage or more of the first voice coil is not inside either the first or second magnetic gap, and may stop driving the second voice coil when the position estimated by the displacement estimation means is such that a predetermined percentage or more of the second voice coil is not inside either the first or second magnetic gap. In this case, the displacement estimation means may set a correspondence between each combination of displacement regions of the first voice coil, which consists of a displacement region in which a predetermined proportion or more of the first voice coil is located inside the first magnetic gap, a displacement region in which a predetermined proportion or more of the first voice coil is located inside the second magnetic gap, and a displacement region in which a predetermined proportion or more of the first voice coil is not located inside either the first or second magnetic gap, and a combination of displacement regions of the second voice coil, which consists of a displacement region in which a predetermined proportion or more of the second voice coil is located inside the first magnetic gap, a displacement region in which a predetermined proportion or more of the second voice coil is located inside the second magnetic gap, and a displacement region in which a predetermined proportion or more of the second voice coil is not located inside either the first or second magnetic gap, and the range of the magnitude of the audio signal, and the displacement estimation means may estimate the displacement regions of the first voice coil and the second voice coil indicated by the combination corresponding to the range that includes the magnitude of the input audio signal as the axial positions of the first voice coil and the second voice coil of the speaker.

[0010] Furthermore, in the above acoustic system, the portion of the first voice coil exceeding a predetermined proportion is the portion of the first voice coil that is n% or more (where n>0), and the portion of the second voice coil exceeding a predetermined proportion may be the portion of the second voice coil that is n% or more. Furthermore, in the above acoustic system, 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 may be located within the upper part of the second gap. Furthermore, in the above acoustic system, the winding width of the first voice coil and the second voice coil may be L, the axial distance between the first voice coil and the second voice coil may be 0.5L, and the axial length of the first magnetic gap and the second magnetic gap may be 1.5L.

[0011] With the acoustic system described above, at least one of two voice coils with different axial ranges can selectively act on both the first and second magnetic gaps, which have different axial ranges and opposite magnetic flux directions, to drive the speaker. As a result, the winding width of the voice coil can be reduced while maintaining driving force over a wide displacement range of the vibration system, and consequently, the stroke width of the speaker over which the drive can be effectively controlled can be increased. [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 suppressing the winding width of the voice coil. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows the configuration of an acoustic system according to an embodiment of the present invention. [Figure 2] This diagram shows the configuration of a speaker according to an embodiment of the present invention. [Figure 3] This figure shows the positional relationship between the magnetic gap and the voice coil according to an embodiment of the present invention. [Figure 4] This figure shows the relationship between displacement and voice coil drive control according to an embodiment of the present invention. [Figure 5] This figure shows an example of the area of ​​magnitude of an input audio signal according to an embodiment of the present invention. [Figure 6] This figure shows an example of voice coil drive control according to an embodiment of the present invention. [Figure 7] This figure shows an example of voice coil drive control according to an embodiment of the present invention. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described below. Figure 1 shows the configuration of the acoustic system according to this embodiment. As shown in the figure, the audio system includes a sound source device 1 that outputs an audio signal, a speaker 2, a signal processing device 3, a first amplifier 4, and a fifth amplifier 5. The signal processing device 3 can be configured using, for example, a DSP (Digital Signal Processor), and includes a first gain adjustment unit 31, a second gain adjustment unit 32, a first signal processing unit 33, a second signal processing unit 34, a control unit 35, and a displacement estimation unit 36. Next, Fig. 2a shows the configuration of the speaker 2. [[ID=I]] 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, and a diaphragm 212.

[0015] Now, if the upward direction in the figure among the axial directions of the speaker 2 is defined as the upward direction of the speaker 2 and the downward direction as the downward direction of the speaker 2, the yoke 202 has a cylindrical shape and is supported at the central portion 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 can move up and down with respect 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 separated from the first voice coil VC1 (205) downward.

[0016] Also, an annular second plate 208, an annular magnet 209, and an annular first plate 207 supported by the outer periphery of the base 201 are provided in a stacked form in the order from below on the outer peripheries of the yoke 202 and the voice coil bobbin 203. Here, the yoke 202 and the second plate 208 are electrically and magnetically separated by the base 201, and a magnetic circuit in which magnetic flux circulates through the magnet 209 - second plate 208 - yoke 202 - first plate 207 - magnet 209 is formed by the yoke 202, the second plate 208, the magnet 209, and the first plate 207.

[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. 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. Here, FIG. 3a shows the positional relationship among 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 the first plate 207 and the yoke 202, and a second magnetic gap GAP2 through which magnetic flux passes is formed between the second plate 208 and the yoke 202. Also, as shown in FIG. 3c, 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 opposite when viewed in a cross-section including the axis of the speaker 2 in the plane.

[0018] Now, the winding widths (coil length / vertical height) of the first voice coil VC1 (205) and the second voice coil VC2 (206) are equal. Also, with the winding width of the first voice coil VC1 (205) and the second voice coil VC2 (206) being L, the distance between the first magnetic gap GAP1 and the second magnetic gap GAP2 is larger than L so that the first voice coil VC1 (205) and the second voice coil VC2 (206) do not enter both the first magnetic gap GAP1 and the second magnetic gap GAP2 simultaneously. Also, the sizes and arrangements of each part are determined such that before the lower end of the first voice coil VC1 (205) detaches from the first magnetic gap GAP1 as the voice coil bobbin 203 moves upward, the upper end of the second voice coil VC2 (206) enters the first magnetic gap GAP1, and before the lower end of the second voice coil VC2 (206) detaches from the second magnetic gap GAP2 as the voice coil bobbin 203 moves downward, the lower end of the first voice coil VC1 (205) enters the second magnetic gap GAP2.

[0019] In this embodiment, we take as an example the 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 gap between the first magnetic gap GAP1 and the second magnetic gap GAP2 is 1.5L, and the vertical distance between the first voice coil VC1(205) and the second voice coil VC2(206) is 0.5L.

[0020] In this embodiment, when 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 such that the upper half of the first voice coil VC1(205) is located within the first magnetic gap GAP1 and the lower half of the second voice coil VC2(206) is located within the second magnetic gap GAP2.

[0021] Next, assuming that the direction of the current flowing from the front to the back (towards the back) of the paper in Figure 3 is the forward direction, and the direction of the current flowing from the back to the front (towards the front) of the paper in Figure 3 is the reverse direction, and that the direction of the magnetic flux passing through the first magnetic gap GAP1 and the direction of the magnetic flux passing through the second magnetic gap GAP2 are as shown in Figure 3c, when at least a portion of the first voice coil VC1(205) is located within the first magnetic gap GAP1, as shown in Figure 3d1, an upward force is applied to the voice coil bobbin 203 when a forward current flows through the first voice coil VC1(205). Similarly, as shown in Figure 3d2, when at least a portion of the second voice coil VC2(206) is located within the first magnetic gap GAP1, an upward force is applied to the voice coil bobbin 203 when a forward current flows through the second voice coil VC2(206). On the other hand, as shown in Figure 3d3, when at least a portion of the second voice coil VC2(206) is located within the second magnetic gap GAP2, an upward force is applied to the voice coil bobbin 203 when a reverse current flows through the second voice coil VC2(206). Similarly, as shown in Figure 3d4, when at least a portion of the first voice coil VC1(205) is located within the second magnetic gap GAP2, an upward force is applied to the voice coil bobbin 203 when a reverse current flows through the first voice coil VC1(205).

[0022] Furthermore, when a forward current flows through the first voice coil VC1(205) and the second voice coil VC2(206), the direction of the magnetic flux generated by the first voice coil VC1(205) and the second voice coil VC2(206) is opposite to the direction of the reverse current flowing through them. Also, when a current flows through the first voice coil VC1(205) and the second voice coil VC2(206) in the same direction, the direction of the magnetic flux generated by the first voice coil VC1(205) and the second voice coil VC2(206) is the same.

[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 in at least one of the first magnetic gap GAP1 and the second magnetic gap GAP2, by applying an audio signal to the first voice coil VC1(205) and the second voice coil VC2(206) with appropriate polarity, the electromagnetic interaction between the magnetic flux generated in the first magnetic gap GAP1 and the second magnetic gap GAP2 and the signal flowing through the first voice coil VC1(205) and the second voice coil VC2(206) causes the diaphragm 212 to vibrate via the voice coil bobbin 203 in accordance with the amplitude of the reproduced sound signal, thereby generating sound in accordance with the reproduced sound signal.

[0024] Now, returning to Figure 1, the displacement estimation unit 36 ​​of the signal processing device 3 estimates the region where the first voice coil VC1 (205) and the second voice coil VC2 (206) are located from the audio signal output by the sound source device 1, and outputs it to the control unit 35. Here, this region includes the first magnetic gap GAP1, the second magnetic gap GAP2, the intermediate region which is the region between the first magnetic gap GAP1 and the second magnetic gap GAP2, and the region outside the GAP, which is neither the first magnetic gap GAP1, the second magnetic gap GAP2, nor the intermediate region, but is the region opposite to the second magnetic gap GAP2 with respect to the first magnetic gap GAP1 and the region opposite to the first magnetic gap GAP1 with respect to the second magnetic gap GAP2.

[0025] The displacement estimation unit 36 ​​estimates whether the first voice coil VC1(205) is located within the first magnetic gap GAP1, within the second magnetic gap GAP2, in the middle, or outside the GAP, and outputs this to the control unit 35. Here, "the first voice coil VC1(205) is located within the first magnetic gap GAP1" means that at least a part of the first voice coil VC1(205) is located within the first magnetic gap GAP1, "the first voice coil VC1(205) is located within the second magnetic gap GAP2" means that at least a part of the first voice coil VC1(205) is located within the second magnetic gap GAP2, "the first voice coil VC1(205) is located in the middle" means that the entire first voice coil VC1(205) is located in the middle, and "the first voice coil VC1(205) is located outside the GAP" means that the entire first voice coil VC1(205) is located outside the GAP.

[0026] Similarly, for the second voice coil VC2(206), it is estimated whether the second voice coil VC2(206) is located within the first magnetic gap GAP1, within the second magnetic gap GAP2, in the middle, or outside the GAP, and this is output to the control unit 35. Here, "the second voice coil VC2(206) is within the first magnetic gap GAP1" means that at least a part of the second voice coil VC2(206) is within the first magnetic gap GAP1, "the second voice coil VC2(206) is within the second magnetic gap GAP2" means that at least a part of the second voice coil VC2(206) is within the second magnetic gap GAP2, "the second voice coil VC2(206) is in the middle" means that the entire second voice coil VC2(206) is in the middle, and "the second voice coil VC2(206) is outside the GAP" means that the entire second voice coil VC2(206) is outside the GAP.

[0027] Next, the first gain adjustment unit 31 adjusts the gain of the audio signal input from the sound source device 1 using the gain set by the control unit 35 and outputs it to the first signal processing unit 33, and the second gain adjustment unit 32 adjusts the gain of the audio signal input from the sound source device 1 using the gain set by the control unit 35 and outputs it to the second signal processing unit 34.

[0028] The first signal processing unit 33 outputs the audio signal input from the first gain adjustment unit 31 to the first amplifier 4, and performs the process of switching whether or not to output the audio signal to the first amplifier 4 according to the control unit 35, and the process of switching the positive and negative polarity of the audio signal output to the first amplifier 4 according to the control unit 35. Similarly, the second signal processing unit 34 outputs the audio signal input from the second gain adjustment unit 32 to the second amplifier, and performs the process of switching whether or not to output the audio signal to the second amplifier according to the control unit 35, and the process of switching the positive and negative polarity of the audio signal output to the second amplifier according to the control unit 35.

[0029] The first amplifier 4 amplifies the audio signal input from the first signal processing unit 33 with a predetermined gain and outputs it to the first voice coil VC1 (205) of the speaker 2, and the second amplifier amplifies the audio signal input from the second signal processing unit 34 with the same gain as the first amplifier 4 and outputs it to the second voice coil VC2 (206) of the speaker 2.

[0030] The control of the first signal processing unit 33 and the second signal processing unit 34 performed by the control unit 35 will be described below. The control unit 35 controls the switching of the output of the first signal processing unit 33 and the second signal processing unit 34, and the switching of the positive and negative polarity of the output audio signal, according to the region where the first voice coil VC1 (205) and the second voice coil VC2 (206) are located, as estimated by the displacement estimation unit 36. Here, Figure 4a shows the displacement ΔZ of the speaker 2's vibration system, and the positional relationship between the first voice coil VC1 (205), the second voice coil VC2 (206), the first magnetic gap GAP1, the second magnetic gap GAP2, the intermediate region, and the region outside the GAP. Figure 4b1 shows the relationship between the region where the first voice coil VC1(205), controlled by the control unit 35, is located, the presence or absence of output from the first signal processing unit 33 to the first amplifier 4, and the positive and negative polarity of the audio signal output to the first amplifier 4. However, the positive and negative polarity of the audio signal output to the first amplifier 4 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 signal processing unit 33 is positive. Figure 4b2 shows the relationship between the region where the second voice coil VC2(206), controlled by the control unit 35, is located, the presence or absence of output from the second signal processing unit 34 to the second amplifier, and the positive and negative polarity of the audio signal output to the second amplifier. However, the positive and negative polarity of the audio signal output to the second amplifier 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 signal processing unit 34 is positive.

[0031] 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 / reverse direction shown in Figures 3d1-d4. As shown in the figure, the control unit 35 controls the polarity of the audio signal output by the first signal processing unit 33 to the first amplifier 4, such that when the first voice coil VC1(205) is in 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 signal processing unit 33 is positive, and when the first voice coil VC1(205) is in 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 signal processing unit 33 is positive.

[0032] Furthermore, the control unit 35 controls the output of the first signal processing unit 33 to the first amplifier 4 so as to stop the output to the first amplifier 4 when the first voice coil VC1(205) is in the middle or outside the GAP. Furthermore, the control unit 35 controls the polarity of the audio signal output by the second signal processing unit 34 to the second amplifier so that when the second voice coil VC2(206) is inside 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 signal processing unit 34 is positive, and when the second voice coil VC2(206) is inside 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 signal processing unit 34 is positive.

[0033] Furthermore, the control unit 35 controls the output of the second signal processing unit 34 to the second amplifier so as to stop the output to the second amplifier when the second voice coil VC2(206) is in the middle or outside the GAP. As a result, when the speaker 2 is displaced within the range BZ, which is the range between the position where the lower end of the first voice coil VC1(205) is at the lower end of the second magnetic gap GAP2 and the position where the lower end of the second voice coil VC2(206) is at the upper end of the first magnetic gap GAP1, at least a part 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 BZ, the control unit 35 shown in Figures 4b1 and 4b2 can apply force to the voice coil bobbin 203 in the appropriate direction relative to the positive and negative values ​​of the audio signal output by the sound source device 1, thereby causing the vibration system of the speaker 2 to vibrate.

[0034] Here, if only the first magnetic gap GAP1 is provided as the magnetic gap, and a single voice coil is required to exert driving force within the BZ range, then a voice coil VCL 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), as shown in Figure 4c, is required.

[0035] Therefore, according to this embodiment, the stroke width of the speaker 2 can be increased without using a voice coil with a large winding width, allowing for effective drive control. In addition, since the structure of the magnetic circuit is symmetrical vertically, asymmetrical distortion is less likely to occur. Returning to Figure 1, the control unit 35 controls the gain of the first gain adjustment unit 31 and the gain of the second gain adjustment unit 32 so that the required driving force response from 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.

[0036] Next, we will explain the estimation operation of the displacement estimation unit 36, which estimates the region where the first voice coil VC1 (205) and the second voice coil VC2 (206) are located, based on the audio signal output by the sound source device 1. The displacement estimation unit 36 ​​has, in advance as shown in Figure 5, a correspondence between the range of nine areas, A1 to A9, which represent the magnitude range of the audio signal output by the sound source device 1, and the areas where the first voice coil VC1 (205) and the second voice coil VC2 (206) are located. Here, each area is predetermined and set as follows:

[0037] Area A1: This is the area where, when the control of the control unit 35 described above (control of the gain of the first gain adjustment unit 31 and the second gain adjustment unit 32, and control of the switching of the presence or absence of output of the first signal processing unit 33 and the second signal processing unit 34, and the switching of the positive and negative polarity of the output audio signal) is performed on an audio signal S at a level within Area A1, both the first voice coil VC1 (205) and the second voice coil VC2 (206) are outside the GAP, and the regions where the first voice coil VC1 (205) and the second voice coil VC2 (206) are located are associated.

[0038] Area A2: This is the area where, when the control unit 35 described above is applied to an audio signal S at a level within Area A2, the first voice coil VC1 (205) is outside the GAP and the second voice coil VC2 (206) is inside the first magnetic gap GAP1. The regions where the first voice coil VC1 (205) and the second voice coil VC2 (206) are located are associated.

[0039] Area A3: This is the area where, when the control unit 35 described above is applied to an audio signal S at a level within Area A3, both the first voice coil VC1 (205) and the second voice coil VC2 (206) are within the first magnetic gap GAP1, and the regions in which the first voice coil VC1 (205) and the second voice coil VC2 (206) are located are associated.

[0040] Area A4: This is the area where, when the control unit 35 described above is applied to the audio signal S at the level within Area A4, the first voice coil VC1 (205) is within the first magnetic gap GAP1 and the second voice coil VC2 (206) is in the middle. The regions in which the first voice coil VC1 (205) and the second voice coil VC2 (206) are located are associated.

[0041] Area A5: When the control unit 35 described above is applied to an audio signal S at a level within Area A5, there is an area where the first voice coil VC1 (205) is within the first magnetic gap GAP1 and the second voice coil VC2 (206) is within the second magnetic gap GAP2, and the regions in which the first voice coil VC1 (205) and the second voice coil VC2 (206) are located are associated with each other.

[0042] Area A6: When the control unit 35 described above is applied to the audio signal S at the level within Area A6, there is an area where the first voice coil VC1 (205) is in the middle and the second voice coil VC2 (206) is in the second magnetic gap GAP2, and the regions where the first voice coil VC1 (205) and the second voice coil VC2 (206) are located are associated with each other.

[0043] Area A7: When the control unit 35 described above is applied to the audio signal S at the level within Area A7, there is an area where both the first voice coil VC1 (205) and the second voice coil VC2 (206) are within the second magnetic gap GAP, and the regions in which the first voice coil VC1 (205) and the second voice coil VC2 (206) are located are associated with each other.

[0044] Area A8: When the control unit 35 described above is applied to an audio signal S at a level within Area A8, there is an area where the first voice coil VC1 (205) is inside the second magnetic gap GAP and the second voice coil VC2 (206) is outside the GAP, and the regions where the first voice coil VC1 (205) and the second voice coil VC2 (206) are located are associated with each other.

[0045] Area A9; When the control unit 35 described above is applied to an audio signal S at a level within Area A1, there is an area where both the first voice coil VC1 (205) and the second voice coil VC2 (206) are outside the GAP, and the regions where the first voice coil VC1 (205) and the second voice coil VC2 (206) are located are associated with each other.

[0046] The displacement estimation unit 36 ​​then detects which area the magnitude of the audio signal output by the sound source device 1 falls into, estimates the region corresponding to the detected area as the region where the first voice coil VC1 (205) and the second voice coil VC2 (206) are located, and outputs it to the control unit 35. As a result of the above control, when the value of the applied audio signal is positive, and current flows in the forward direction through the first voice coil VC1 (205) and in the reverse direction through the second voice coil VC2 (206), the output of the first signal processing unit 33 is controlled as shown in Figure 6, and the output of the second signal processing unit 34 is controlled as shown in Figure 3.

[0047] In other words, as shown in Figure 6, the output of the first signal processing unit 33 is stopped when the magnitude of the audio signal S output by the sound source device 1 is within areas A1 and A2, the polarity of the audio signal S is maintained when it is within areas A3, A4 and A5, stopped when it is within area A6, the polarity of the audio signal S is reversed when it is within areas A7 and A8, and stopped when it is within area A9.

[0048] Furthermore, as shown in Figure 7, the output of the second signal processing unit 34 is stopped when the magnitude of the audio signal S output by the sound source device 1 is within area A1, the polarity of the audio signal S is reversed when it is within areas A2 and A3, stopped when it is within area A4, the polarity of the audio signal S is maintained when it is within areas A5, A6 and A7, and stopped when it is within areas A8 and A9.

[0049] Now, the correspondence between the ranges of the nine areas A1 to A9, which are set in advance in the displacement estimation unit 36, and the regions in which the first voice coil VC1 (205) and the second voice coil VC2 (206) are located can be determined, for example, as follows. Specifically, a sensor is provided to detect the displacement ΔZ of the speaker 2's vibration system. The displacement estimation unit 36 ​​calculates the region where the first voice coil VC1 (205) and the second voice coil VC2 (206) are located based on the displacement ΔZ detected by the sensor and outputs it to the control unit 35. With the control unit 35 performing the above-described control, the sound source device 1 outputs a predetermined test signal (for example, a sine wave) with a gradually increasing amplitude.

[0050] Then, when the combination of regions where the first voice coil VC1(205) and the second voice coil VC2(206) are located, as calculated by the displacement estimation unit 36, changes, the magnitude of the test signal is stored by associating the detected combination of regions with the boundary between the area corresponding to the detected combination of regions and the area corresponding to the combination of regions adjacent to that area in the direction where the absolute value of the magnitude of the audio signal is smaller. As the magnitude of the test signal, the maximum value of the test signal is used if the detected combination of regions corresponds to the magnitude of a positively changing audio signal, and the minimum value is used if the detected combination of regions corresponds to the magnitude of a negative audio signal.

[0051] Then, using the boundaries between each area determined as described above, we determine the correspondence between the ranges of the nine areas A1 to A9 and the regions where the first voice coil VC1 (205) and the second voice coil VC2 (206) are located. Embodiments of the present invention have been described above. In this embodiment, the displacement estimation unit 36 ​​estimates the displacement ΔX of the first voice coil VC1 (205) and the second voice coil VC2 (206) from the magnitude of the audio signal output by the sound source device 1, and the control unit 35 controls the gain of the first gain adjustment unit 31 and the gain of the second gain adjustment unit 32 in accordance with the displacement ΔX estimated by the displacement estimation unit 36, so that the response of the vibration system to the audio signal is as equal as possible within the displacement range BZ shown in Figure 4a. [Explanation of Symbols]

[0052] 1...Sound source device, 2...Speaker, 3...Signal processing device, 4...First amplifier, 5...Fifth amplifier, 31...First gain adjustment unit, 32...Second gain adjustment unit, 33...First signal processing unit, 34...Second signal processing unit, 35...Control unit, 36...Displacement estimation unit, 201...Base, 202...Yoke, 203...Voice coil bobbin, 204...Dust cap, 205...Voice coil VC2, 206...Voice coil VC1, 207...First plate, 208...Second plate, 209...Magnet, 210...Frame, 211...Damper, 212...Diaphragm.

Claims

1. Speakers and, A drive unit that drives the speaker with a drive signal generated from the input audio signal, It includes a displacement estimation means, The aforementioned speaker is A first magnetic gap and a second magnetic gap that overlaps with the first magnetic gap when viewed in the axial direction of the speaker, The speaker has a first voice coil and a second voice coil fixed to the vibrating system of the speaker which vibrates in the axial direction, such that they are located inside the first magnetic gap and the second magnetic gap when viewed in the axial direction. With one of the aforementioned axial directions being upward and the other downward, the first magnetic gap is provided above the second magnetic gap at an axial distance. The first voice coil is provided above the second voice coil at the axial distance, The first magnetic gap propagates magnetic flux in one of the radial directions 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, and the vibration system is provided to vibrate between a position in which at least a portion of the first voice coil and at least a portion of the second voice coil are inside the first magnetic gap and a position in which they are inside the second magnetic gap. The displacement estimation unit is, From the magnitude of the input audio signal, the axial positions of the first voice coil and the second voice coil of the speaker are estimated. The aforementioned drive unit is When the position estimated by the displacement estimation means is such that at least a predetermined proportion of the first voice coil is inside the first magnetic gap, the first voice coil is driven with a drive signal of polarity such that the direction of the current flowing through the first voice coil with respect to a positive audio signal is in a first direction, and when the position is such that a predetermined proportion of the first voice coil is inside the second magnetic gap, the first voice coil is driven with a drive signal of polarity such that the direction of the current flowing through the first voice coil with respect to a positive audio signal is in a second direction, opposite to the first direction. An acoustic system characterized in that, when the position estimated by the displacement estimation means is such that at least a predetermined portion of the second voice coil is inside the first magnetic gap, the second voice coil is driven with a drive signal of polarity such that the direction of the current flowing through the second voice coil in response to a positive audio signal is the first direction, and when at least a predetermined proportion of the second voice coil is inside the second magnetic gap, the second voice coil is driven with a drive signal of polarity such that the direction of the current flowing through the second voice coil in response to a positive audio signal is the second direction.

2. The acoustic system according to claim 1, In the first range of displacement of the vibration system, both a portion of the first voice coil exceeding a predetermined proportion and a portion of the second voice coil exceeding a predetermined proportion are located inside the first magnetic gap, and in the second range of displacement of the vibration system, both a portion of the first voice coil exceeding a predetermined proportion and a portion of the second voice coil exceeding a small predetermined proportion are located inside the second magnetic gap. The drive unit is characterized in that, when the position estimated by the displacement estimation means is a position in which both a predetermined proportion or more of the first voice coil and a predetermined proportion or more of the second voice coil are inside the first magnetic gap, it drives both the first voice coil and the second voice coil with a drive signal of polarity such that the direction of the current flowing with respect to a positive audio signal is the first direction, and when the position estimated by the displacement estimation means is a position in which both a predetermined proportion or more of the first voice coil and a predetermined proportion or more of the second voice coil are inside the second magnetic gap, it drives both the first voice coil and the second voice coil with a drive signal of polarity such that the direction of the current flowing with respect to a positive audio signal is the second direction.

3. The acoustic system according to claim 2, The drive unit is characterized in that it stops driving the first voice coil when the position estimated by the displacement estimation means is such that a predetermined proportion or more of the first voice coil is not inside either the first or second magnetic gap, and stops driving the second voice coil when the position estimated by the displacement estimation means is such that a predetermined proportion or more of the second voice coil is not inside either the first or second magnetic gap.

4. The acoustic system according to claim 3, The displacement estimation means includes: One element of a set of displacement regions of the first voice coil, which includes a displacement region in which a predetermined proportion or more of the first voice coil is located inside the first magnetic gap, a displacement region in which a predetermined proportion or more of the first voice coil is located inside the second magnetic gap, and a displacement region in which a predetermined proportion or more of the first voice coil is not located inside either the first or second magnetic gap, One element of a set of displacement regions of the second voice coil, which includes a displacement region in which a predetermined proportion or more of the second voice coil is located inside the first magnetic gap, a displacement region in which a predetermined proportion or more of the second voice coil is located inside the second magnetic gap, and a displacement region in which a predetermined proportion or more of the second voice coil is not located inside either the first or second magnetic gap, Each combination has a corresponding range for the audio signal magnitude. The displacement estimation means is characterized by estimating the displacement regions of the first voice coil and the second voice coil, which are indicated by a combination corresponding to a range that includes the magnitude of the input audio signal, as the axial positions of the first voice coil and the second voice coil of the speaker.

5. The acoustic system according to claim 1, 2, 3, or 4, An acoustic system characterized in that a predetermined proportion or more of the first voice coil is n% or more of the first voice coil (where n > 0), and a predetermined proportion or more of the second voice coil is n% or more of the second voice coil.

6. The acoustic system according to claim 1, An acoustic system characterized in that when the upper half of the first voice coil is located within the lower half of the first gap, the lower half of the second voice coil is located within the upper half of the second gap.

7. The acoustic system according to claim 6, An acoustic system characterized in that the winding width of the first voice coil and the second voice coil is L, the axial distance between the first voice coil and the second voice coil is 0.5L, and the axial length of the first magnetic gap and the second magnetic gap is 1.5L.

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