Sound system

Abstract

The present invention addresses the problem of providing a sound system that obtains a required driving force with low power consumption. A first voice coil (2051) having a height greater than the height of a gap through which magnetic flux propagates and a second voice coil (2052) having a height equal to the height of the gap are provided so that the center in the height direction coincides (a1). When the amplification factor of the audio signal applied to the first voice coil (2051) is A1, and the amplification factor of the audio signal applied to the second voice coil (2052) is A2, the displacement of the speaker (2) is detected, and when the second voice coil (2052) is within the displacement range of a position where the second voice coil (2052) can appropriately act on the magnetic flux of the gap, A1 is 0, and A2 is a predetermined amplification factor A2st. Furthermore, in a displacement range in which A2 is not set as A2st, A2 is set as 0, and A1 is set as a predetermined amplification factor A1st. A2st < A1st, and a range in which the second voice coil (2052) is separated from the gap is included in a displacement range (a1-a3, b1, b2) in which A1 is set as A1st.

Description

TECHNICAL FIELD

[0001] The present application relates to a technology of driving a speaker. BACKGROUND

[0002] As a technology related to the present application, there is known a technology of providing a sensor that detects displacement of a vibrating system of a speaker, correcting an input signal in a manner to reduce output distortion of the speaker based on a response of the displacement to the input signal, and outputting to the speaker (for example, Patent Literature 1).

[0003] Further, as a technology related to the present application, there is known a technology of providing a plurality of voice coils having different direct current resistance values in a speaker, and being able to switch a driven voice coil, thereby making a Q characteristic of a low frequency of the speaker variable (for example, Patent Literature 2).

[0004] [Patent Literature]

[0005] [Patent Literature]

[0006] [Patent Literature 1] Japanese Patent Application Laid-Open No. 2007-81815

[0007] [Patent Literature 2] Japanese Patent Application Laid-Open No. Sho 62-139192 SUMMARY

[0008] Problems to be Solved by the Invention

[0009] In a case where generation of output distortion of the speaker or generation of over-amplitude or the like of the speaker is suppressed by operating a signal applied to the voice coil based on displacement of the vibrating system of the speaker detected by the sensor, a driving force acts on the voice coil by interaction with magnetic flux passing through a gap between the leading magnetic plate and the center column, and therefore, if the voice coil is displaced to a position deviating from the gap, the driving force acting on the voice coil disappears, and generation of the bad action cannot be suppressed.

[0010] On the other hand, if the height of the voice coil is made sufficiently large with respect to the height (length in the axial direction of the speaker) of the gap, displacement of the voice coil to a position deviating from the gap can be suppressed, but in this case, the driving force acting on the voice coil is smaller than that of the voice coil having a height of the order of the height of the gap for the same input, and initial sensitivity or the like is deteriorated. On the other hand, if the amplification of the signal output to the voice coil is increased, the driving force acting on the voice coil can be increased, but in this case, power consumption is increased.

[0011] Therefore, the present application aims at suppressing power consumption as much as possible while obtaining a driving force required for the voice coil.

[0012] Means for Solving the Problems

[0013] To achieve the above object, the present application provides an audio system including a speaker and a drive unit that drives the speaker with an audio signal. The audio system includes a displacement detection unit that detects displacement of a vibration system of the speaker in an axial direction of the speaker. In addition, the speaker includes a first voice coil and a second voice coil that are disposed in a gap in which magnetic flux propagates in a radial direction of the speaker, a range of the first voice coil in the axial direction of the speaker is larger than a range of the gap in the axial direction, a range of the second voice coil in the axial direction is smaller than a range of the first voice coil in the axial direction, and the range of the second voice coil in the axial direction converges in the range of the first voice coil in the axial direction. Furthermore, the drive unit includes a first drive unit that applies an audio signal amplified at a first amplification rate to the first voice coil, a second drive unit that applies an audio signal amplified at a second amplification rate to the second voice coil, and an amplification rate setting unit that sets 0 as the second amplification rate when a position of the second voice coil in the axial direction indicated by displacement detected by the displacement detection unit is a position in an ineffective range in which the second voice coil cannot act on the magnetic flux propagating in the gap, sets a first standard amplification rate as the first amplification rate when the position of the second voice coil is a position in an effective range in which the second voice coil can appropriately act on the magnetic flux propagating in the gap, and sets 0 as the first amplification rate when the position of the second voice coil is a position in the ineffective range.

[0014] In this case, in the audio system, the ineffective range can be a range in which the position of the second voice coil in the axial direction is outside the range of the gap, and the effective range can be a range in which the position of the second voice coil in the axial direction is not outside the range of the gap.

[0015] In addition, the above audio system can be configured such that, in a state in which the audio signal is not applied to both the first voice coil and the second voice coil, the gap is equal to a midpoint of the ranges of the first voice coil and the second voice coil in the axial direction.

[0016] Furthermore, in the above audio system, the first standard amplification rate can be greater than the second standard amplification rate, the first drive unit can include a first amplifier that outputs the audio signal applied to the first voice coil, and the second drive unit can include a second amplifier that outputs the audio signal applied to the second voice coil, and a power supply voltage of the second amplifier can be smaller than a power supply voltage of the first amplifier.

[0017] Further, the above-described audio system can be configured such that the above-described amplification ratio setting unit is replaced by an amplification ratio setting unit configured to set, as the second amplification ratio, a smaller amplification ratio than that set as the first amplification ratio when the position of the second voice coil in the axial direction indicated by the displacement detected by the displacement detecting unit is a position at which the second voice coil cannot act on the magnetic flux propagating in the gap, and set, as the first amplification ratio, a larger amplification ratio than that set as the second amplification ratio when the position of the second voice coil in the axial direction indicated by the displacement detected by the displacement detecting unit is a position at which the second voice coil can act on the magnetic flux propagating in the gap.

[0018] In this case, in the above-described driving unit of the audio system, a bad action suppressing unit configured to operate the audio signal for driving the first voice coil based on the displacement detected by the displacement detecting unit so as not to cause a bad action of the loudspeaker can be provided.

[0019] As described above, the audio system according to the present application is provided with a first voice coil having an axial range larger than the gap and a second voice coil having an axial range smaller than the first voice coil. Typically, when the second voice coil is located in a range in which the second voice coil can appropriately act on the magnetic flux propagating in the gap, the loudspeaker is driven by applying the audio signal to only the second voice coil, and when the second voice coil is located in a range in which the second voice coil cannot act on the magnetic flux propagating in the gap, the loudspeaker is driven by applying the audio signal to only the first voice coil.

[0020] In this case, in the case in which the second voice coil can appropriately act on the magnetic flux propagating in the gap, the second voice coil having a smaller axial range than the first voice coil has a larger driving force for the same input, and therefore the amplification ratio of the audio signal when the loudspeaker is driven by applying the audio signal to only the second voice coil can be smaller than the amplification ratio of the audio signal when the loudspeaker is driven by applying the audio signal to only the first voice coil, and as a result, the power consumption when the loudspeaker is driven by applying the audio signal to only the second voice coil can be smaller than the power consumption when the loudspeaker is driven by applying the audio signal to only the first voice coil.

[0021] Further, even if the second voice coil is separated from the gap and cannot act on the magnetic flux propagating in the gap, the first voice coil having a larger axial range than the second voice coil is in a state in which the first voice coil can act on the magnetic flux propagating in the gap, and therefore the driving force required for appropriate reproduction of the audio signal, suppression of a bad action, and the like can be obtained by driving the first voice coil.

[0022] Effects of the Invention

[0023] As described above, according to the present application, it is possible to suppress the power consumption as much as possible while obtaining the driving force required for the voice coil. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1is a diagram showing the configuration of a sound system according to an embodiment of the present application.

[0025] Figure 2 is a diagram showing the configuration of a speaker according to an embodiment of the present application.

[0026] Figure 3 is a diagram showing a control example of magnification according to an embodiment of the present application.

[0027] Explanation of Reference Numerals:

[0028] 1…sound source device, 2…speaker, 3…displacement sensor, 4…signal processing device, 5…first amplifier, 6…second amplifier, 41…first magnification adjustment section, 42…second magnification adjustment section, 43…first distortion suppression section, 44…second distortion suppression section, 45…over-amplitude protection section, 46…displacement detection section, 47…control section, 201…yoke, 202…magnet, 203…front magnetic plate, 204…voice coil former, 206…yoke, 207…rubber damper, 208…diaphragm, 209…edge, 210…dust cover, 211…magnet for displacement detection, 220…magnetic circuit, 2011…center pole, 2051…first voice coil, 2052…second voice coil. DETAILED DESCRIPTION

[0029] Hereinafter, an embodiment of the present application will be described.

[0030] Figure 1 The structure of a sound system according to the present embodiment is shown.

[0031] As shown in the figure, the sound system is provided with 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.

[0032] The power supply voltage V1 of the first amplifier 5 is greater than the power supply voltage V2 of the second amplifier 6, and the rated output / output maximum amplitude of the first amplifier 5 is greater than that of the second amplifier 6.

[0033] Here, in the case where the sound system is mounted on a car, a battery of the car can be used as the power supply of the second amplifier 6, and in this case, the power supply voltage V2 is about 12 V to 13 V. Also, in the case where the battery of the car is used as the power supply of the second amplifier 6, the power supply voltage of the battery is boosted to, for example, 20 V and used as the power supply voltage V1.

[0034] The signal processing device 4 is configured using, for example, a DSP (Digital Signal Processor), and includes a first amplification ratio adjustment section 41, a second amplification ratio adjustment section 42, a first distortion suppression section 43, a second distortion suppression section 44, an over-amplification protection section 45, a displacement detection section 46, and a control section 47.

[0035] Next, in Figure 2 The structure of the speaker 2 is shown in a.

[0036] As shown in the drawing, the speaker 2 has a yoke 201, a magnet 202, a front magnetic plate 203, a voice coil former 204, a voice coil 205, a spider 206, a dust cap 207, a diaphragm 208, a rim 209, a dust cover 210, and a displacement detection magnet 211.

[0037] Now, if the upward direction in the drawing in the axial direction of the speaker 2 is taken as the upward direction of the speaker 2 and the downward direction is taken as the downward direction of the speaker 2, the yoke 201 has a center pole 2011 projecting upward in the central portion, and the magnet 202 is provided in a ring shape on the outer peripheral portion of the center pole 2011. The front magnetic plate 203 is provided in a ring shape on the magnet 202. In addition, the front magnetic plate 203 is made of a member having electrical conductivity such as iron. Furthermore, a magnetic circuit 220 is formed by the yoke 201, the magnet 202, and the front magnetic plate 203.

[0038] Here, as shown in a and b of Figure 2 The voice coil former 204 has a hollow cylindrical shape, as shown in b and c of Figure 2 The first voice coil 2051, which is indicated by a white circle, and the second voice coil 2052, which is indicated by a black circle, are wound in a state in which the second voice coil 2052 is stacked on the outer periphery of the first voice coil 2051, as shown in b and c of

[0039] In addition, the center pole 2011 of the yoke 201 is inserted into the hollow of the voice coil former 204 from below, and the voice coil former 204 is movable up and down with respect to the yoke 201.

[0040] In addition, as shown in b and c of Figure 2 In a neutral state in which no signal is applied to the first voice coil 2051 and the second voice coil 2052, the first voice coil 2051 and the second voice coil 2052 are arranged so that the position of the center in the upward and downward directions of the first voice coil 2051 and the second voice coil 2052 coincides with the position of the center in the upward and downward directions of the gap, which is a gap through which the magnetic flux between the center pole 2011 of the yoke 201 and the front magnetic plate 203 propagates in the radial direction of the speaker 2 (the left and right directions of the drawing).

[0041] In addition, as shown in b and c of Figure 2As shown in c, the height (length in the vertical direction) H1 of the first voice coil 2051 is much larger than the height H0 of the gap (e.g., H1 ≥ 1.5 × H0), and the height H2 of the second voice coil 2052 is approximately equal to the height H0 of the gap.

[0042] Therefore, when the impedances of the first voice coil 2051 and the second voice coil 2052 are made the same, the first voice coil 2051 has a larger wire diameter and a longer wire length compared to the second voice coil 2052.

[0043] The diaphragm 208 has a shape that is approximately the same as the side of a frustum with the vertical direction of the speaker 2 as its height direction, and its outer peripheral end is connected to the upper end of the frame 206 via the edge 209. In addition, the inner peripheral end of the diaphragm 208 is fixed to the upper end of the voice coil frame 204.

[0044] In this loudspeaker 2 structure, when a signal is applied to the first voice coil 2051 and the second voice coil 2052, the voice coil frame 204 vibrates up and down according to the amplitude of the applied signal through the electromagnetic interaction between the magnetic flux passing through the gap in the radial direction and the signal flowing in the first voice coil 2051 and the second voice coil 2052. Furthermore, when the voice coil frame 204 vibrates, the diaphragm 208 connected to the voice coil frame 204 vibrates, producing sound corresponding to the applied signal.

[0045] Next, as Figure 2 As shown in a and b, the displacement detection magnet 211 is fixed to the outer periphery of the voice coil frame 204 in a manner that moves up and down together with the voice coil frame 204, generating a magnetic flux in a direction orthogonal to the magnetic flux generated by the magnetic circuit 220.

[0046] Next, the aforementioned displacement sensor 3 is fixed to the position of the proximity displacement detection magnet 211 of the non-vibration system of the speaker 2, such as the front guide magnetic plate 203. The displacement sensor 3 is a magnetic angle sensor, such as... Figure 2 As shown in d, the arctangent of the angle Qs / Qc of the resultant vector Q of the magnetic flux vector Qc acting from the magnetic circuit 220 and the magnetic flux vector Qs acting from the displacement detection magnet 211 is detected and output as the magnetic angle. The magnetic flux vector generated by the displacement detection magnet 211 acting on the displacement sensor 3 changes due to the displacement of the voice coil frame 204 in the vertical direction. Therefore, this magnetic angle becomes a value corresponding to the vertical displacement of the voice coil frame 204, that is, the vertical position of the speaker 2's vibration system.

[0047] return Figure 1 The displacement detection unit 46 of the signal processing device 4 calculates the vertical displacement position z_VC of the vibration system of the loudspeaker 2 based on the magnetic angle detected by the displacement sensor 3 and outputs it to the control unit 47.

[0048] The control section 47 controls the amplification A1 of the first amplification ratio adjustment section 41 in accordance with the displacement position z VC of the vibration system of the speaker 2 detected by the displacement detection section 46, and controls the amplification A2 of the second amplification ratio adjustment section 42 in accordance with the displacement position z VC.

[0049] In addition, the control section 47 predicts generation of an over-amplitude of the vibration system of the speaker 2 in accordance with the displacement position z VC of the vibration system of the speaker 2 detected by the displacement detection section 46, the amplitude of the vibration of the vibration system of the speaker 2 indicated by the displacement position z VC, and the like, and controls execution of the over-amplitude protection operation of the over-amplitude protection section 45 if generation of the over-amplitude is predicted. Here, the over-amplitude of the vibration system of the speaker 2 refers to an amplitude of a size that causes a mechanical failure such as a bottoming of the voice coil former 204 colliding with the yoke 201.

[0050] In addition, the control section 47 relays the displacement position z VC of the vibration system of the speaker 2 detected by the displacement detection section 46 to the first distortion suppression section 43, the second distortion suppression section 44, and the over-amplitude protection section 45.

[0051] Next, the first amplification ratio adjustment section 41 amplifies and outputs the audio signal input from the sound source device 1 at the amplification A1 set by the control section 47 to the first distortion suppression section 43. However, the first amplification ratio adjustment section 41 can also implement amplification based on the amplification A1 by setting the output to 0 when the amplification A1 is 0.

[0052] The first distortion suppression section 43 outputs the audio signal input from the first amplification ratio adjustment section 41 after applying the transfer function set to itself. In addition, the first distortion suppression section 43 performs an operation of updating the transfer function set to itself to correct the transfer function of the audio signal in such a way that the response of the displacement position z VC notified from the control section 47 to the audio signal input from the first amplification ratio adjustment section 41 becomes a distortionless response. However, the first distortion suppression section 43 can also perform an operation of setting the output to 0 when the amplification A1 is 0.

[0053] The over-amplitude protection section 45 normally outputs the audio signal inputted from the first distortion suppression section 43 directly to the first amplifier 5 transparently, but during the period in which the execution of the over-amplitude protection operation is controlled by the control section 47, the over-amplitude protection operation as follows is performed. That is, the over-amplitude protection section 45 performs, for example, a braking operation as the over-amplitude protection operation in which a braking signal for supplying a driving force in the direction opposite to the displacement direction indicated by the displacement position z VC notified from the control section 47 to the first voice coil 2051 is generated and outputted to the first amplifier 5 instead of the audio signal. Alternatively, the over-amplitude protection section 45 performs, for example, an amplitude suppression operation as the over-amplitude protection operation in which the audio signal inputted from the first distortion suppression section 43 is attenuated and then outputted to the first amplifier 5.

[0054] The first amplifier 5 amplifies the audio signal or the braking signal inputted from the over-amplitude protection section 45 at the amplification rate set fixedly in advance and then outputs the amplified signal to the first voice coil 2051 of the speaker 2.

[0055] Next, the second amplification rate adjustment section 42 amplifies the audio signal inputted from the sound source device 1 at the amplification rate A2 set by the control section 47 and then outputs the amplified signal to the second distortion suppression section 44. However, the second amplification rate adjustment section 42 can also realize the amplification based on the amplification rate A2 by setting the output to 0 when the amplification rate A2 is 0.

[0056] The second distortion suppression section 44 applies the transfer function set to itself to the audio signal inputted from the second amplification rate adjustment section 42 and then outputs the signal to the second amplifier 6. In addition, the second distortion suppression section 44 performs an operation of updating the transfer function set to itself to a transfer function for correcting the audio signal in such a manner that the response of the displacement position z VC notified from the control section 47 to the audio signal inputted from the second amplification rate adjustment section 42 becomes a response without distortion. However, the second distortion suppression section 44 can also perform an operation of setting the output to 0 when the amplification rate A2 is 0.

[0057] The second amplifier 6 amplifies the audio signal inputted from the second distortion suppression section 44 at the same amplification rate as the first amplifier 5 and then outputs the amplified signal to the second voice coil 2052 of the speaker 2.

[0058] Next, the control of the amplification rates Al of the first amplification rate adjustment section 41 and A2 of the second amplification rate adjustment section 42 by the control section 47 corresponding to the displacement position z VC of the vibration system of the speaker 2 will be described.

[0059] Now, as Figure 3indicated by a1, in a case where the displacement position z VC is indicated using the z-axis of the speaker 2 in the up-down direction, when the position in the height direction of the first voice coil 2051 and the second voice coil 2052 at the center coincides with the position in the height direction (up-down direction) of the gap at the center, z VC = 0, when the voice coil skeleton is displaced upward from the position of a1, as indicated by a2, when the lower end of the second voice coil 2052 reaches the upper end of the gap, z VC = Uz > 0, when the voice coil skeleton is displaced downward from the position of a1, as indicated by a3, when the upper end of the second voice coil 2052 reaches the lower end of the gap, z VC = Lz < 0, the control section 47 controls the magnification A1 of the first magnification adjustment section 41 and the magnification A2 of the second magnification adjustment section 42, for example, as indicated by b1 and b2. Figure 3 Figure 3 Figure 3 Figure 3 Figure 3

[0060] That is, in a range of Uz ≥ z VC ≥ Lz in which the second voice coil 2052 is positioned in a range in which the magnetic flux of the gap can act appropriately, the magnification A1 is set to 0, and the magnification A2 is set to a predetermined magnification A2st. Also, in a range in which the magnification A2 is not set to the magnification A2st, the magnification A2 is set to 0, and the magnification A1 is set to a predetermined magnification A1st. Here, in the range in which the magnification A1 is set to the magnification A1st, a range of z VC < Lz in which the second voice coil 2052 is in a position in which it is separated from the gap and a range of z VC > Uz are included. Also, the range in which the second voice coil 2052 is positioned in a range in which the magnetic flux of the gap can act appropriately can be a range of Uz ≥ z VC ≥ Lz in which the second voice coil 2052 is not completely separated from the gap.

[0061] Here, A1st is a magnification with which a driving force required for desired vibration can be achieved by driving only the first voice coil 2051 using an audio signal amplified by A1st, and A2st is a magnification with which a driving force required for desired vibration can be achieved by driving only the second voice coil 2052 using an audio signal amplified by A2st when the second voice coil 2052 can act appropriately with the magnetic flux of the gap, and the driving force of the second voice coil 2052, which is smaller in height, is larger than the driving force of the first voice coil 2051 for the same input when it can act appropriately with the magnetic flux of the gap, so as shown, 0 < A2st < A1st is obtained.

[0062] ​​​​​Therefore, when the audio signal amplified by A2st is provided to the second amplifier 6 to drive only the second voice coil 2052, the amplitude of the audio signal output from the second amplifier 6 or the power consumption of the second amplifier 6 is less than when the audio signal amplified by A1st is provided to the first amplifier 5 to drive only the first voice coil 2051, the amplitude of the audio signal output from the first amplifier 5 or the power consumption of the first amplifier 5. Furthermore, since the outputs of both the first and second amplifiers 5 are also zero, the power consumption of the first amplifier 5 when amplification A1 is set to 0 or the power consumption of the second amplifier 5 when amplification A12 is set to 0 becomes sufficiently small.

[0063] Therefore, by controlling the amplification A1 of the first amplification adjustment unit 41 and the amplification A2 of the second amplification adjustment unit 42, the power consumption of the first amplifier 5 and the second amplifier 6 when only the second voice coil 2052 is driven can be suppressed to be smaller than the power consumption of the first amplifier 5 and the second amplifier 6 when only the first voice coil 2051 is driven, and the driving force required for the desired vibration can be ensured even when only the first voice coil 2051 is driven.

[0064] In addition, in driving the second voice coil 2052, a second amplifier 6 with a power supply voltage (rated output / maximum output voltage) smaller than that of the first amplifier 5 used in driving the first voice coil 2051 is used. Therefore, from this point of view, it is also possible to suppress the power consumption when only driving the second voice coil 2052.

[0065] Furthermore, even if the second voice coil 2052 disengages from the gap and thus cannot interact with the magnetic flux propagating in the gap, the first voice coil 2051, which has a wider axial range than the second voice coil 2052, is in a state where it can interact with the magnetic flux propagating in the gap. Therefore, the first voice coil 2051 can be driven to obtain the driving force required for proper reproduction of audio signals, suppression of malfunctions, etc.

[0066] In addition, in such Figure 3 When the amplification A1 of the first amplification adjustment unit 41 and the amplification A2 of the second amplification adjustment unit 42 are controlled as shown in b1 and b2, the control unit 47 controls the operation of the first distortion suppression unit 43 and the second distortion suppression unit 44 in such a way that the update of the transfer function set to itself in the first distortion suppression unit 43 is performed only during the period when the amplification A2 is 0, and the update of the transfer function set to itself in the second distortion suppression unit 44 is performed only during the period when the amplification A2 is 0.

[0067] Here, it is also possible to... Figure 3 The magnification A1 of the first magnification adjustment unit 41 and the magnification A2 of the second magnification adjustment unit 42 are controlled as shown in c1 and c2.

[0068] Figure 3 The control of c1 and c2 is that, Figure 3 In the control of b1 and b2, the changes between 0 and A1st of amplification A1 and between 0 and A2st of amplification A2 are gradually carried out.

[0069] In addition, in such Figure 3 When the amplification A1 of the first amplification adjustment unit 41 and the amplification A2 of the second amplification adjustment unit 42 are controlled in the same way as c1 and c2, the control unit 47 also controls the operation of the first distortion suppression unit 43 and the second distortion suppression unit 44 in such a way that the update of the transfer function set to itself in the first distortion suppression unit 43 is performed only during the period when the amplification A2 is 0, and the update of the transfer function set to itself in the second distortion suppression unit 44 is performed only during the period when the amplification A2 is 0.

[0070] Here, it is also possible to... Figure 3 The first magnification adjustment unit 41 controls the magnification A1 and the second magnification adjustment unit 42, as shown by d1 and d2.

[0071] Figure 3 The control of d1 and d2 is, in Figure 3 In the control of c1 and c2, the A2st ratio of the amplification A2 is made... Figure 3 The amplification shown by c2 is small, and during the period when the amplification A2 is A2st, the amplification A1 is A1sp. There exists A1st>A1sp>0, and A1sp is set to be the amplification of the driving force of the vibration system required for the desired vibration, which can be achieved by driving the second voice coil 2052 based on the amplification A2st and driving the first voice coil 2051 based on the amplification A1sp.

[0072] However, in such ​ When the amplification A1 of the first amplification adjustment unit 41 and the amplification A2 of the second amplification adjustment unit 42 are controlled in the same way as d1 and d2, the control unit 47 controls the first distortion suppression unit 43 in such a way that the update of the transfer function set for itself in the first distortion suppression unit 43 is only performed during the period when the amplification A2 is 0. Alternatively, in this case, the transfer function of the second distortion suppression unit 44 is not updated, and a predetermined transfer function is fixedly used as the transfer function of the second distortion suppression unit 44. Or, the second distortion suppression unit 44 may not be provided, and the audio signal may be directly output from the second amplification adjustment unit 42 to the second amplifier 6.

Claims

1. A sound system comprising a loudspeaker and a driver unit for driving the loudspeaker using an audio signal, characterized in that, A displacement detection unit is provided that can detect the displacement of the vibration system of the loudspeaker along the axial direction of the loudspeaker. The loudspeaker includes a first voice coil and a second voice coil disposed radially within a gap for the magnetic flux to propagate radially. The first voice coil has a larger axial extent than the gap, and the second voice coil has a smaller axial extent than the first voice coil. The range of the second voice coil in the axial direction converges to the range of the first voice coil in the axial direction. The drive unit has: The first driving unit applies the amplified audio signal at a set first amplification rate to the first voice coil; The second drive unit applies the amplified audio signal at a set second amplification rate to the second voice coil; as well as The amplification setting unit, based on the position of the second voice coil in the axial direction represented by the displacement detected by the displacement detection unit, sets 0 as the second amplification when the position of the second voice coil is within the ineffective range, and sets a first standard amplification as a predetermined amplification as the first amplification. The ineffective range is the range within which the second voice coil cannot interact with the magnetic flux propagating in the gap. When the position of the second voice coil is within the effective range, the unit sets 0 as the first amplification, and sets a second standard amplification as a predetermined amplification as the second amplification. The effective range is the range within which the second voice coil can appropriately interact with the magnetic flux propagating in the gap.

2. The audio system according to claim 1, characterized in that, The ineffective range is the range where the position of the second voice coil in the axial direction is outside the range of the gap, and the effective range is the range where the position of the second voice coil in the axial direction is not outside the range of the gap.

3. The audio system according to claim 1, characterized in that, When no audio signal is applied to either the first voice coil or the second voice coil, the gap in the axial direction is equal to the midpoint of the range of the first voice coil and the second voice coil in the axial direction.

4. The audio system according to claim 1, characterized in that, The first standard magnification is greater than the second standard magnification. The first driving unit has a first amplifier that outputs an audio signal applied to the first voice coil. The second driving unit has a second amplifier that outputs an audio signal applied to the second voice coil. The power supply voltage of the second amplifier is less than that of the first amplifier.

5. A sound system comprising a loudspeaker and a driver unit for driving the loudspeaker using an audio signal, characterized in that, A displacement detection unit is provided that can detect the displacement of the vibration system of the loudspeaker along the axial direction of the loudspeaker. The loudspeaker includes a first voice coil and a second voice coil disposed radially within a gap for the magnetic flux to propagate radially. The first voice coil has a larger axial extent than the gap has a larger axial extent, and the second voice coil has a smaller axial extent than the first voice coil. The range of the second voice coil in the axial direction converges to the range of the first voice coil in the axial direction. The drive unit has: The first driving unit applies the amplified audio signal at a set first amplification rate to the first voice coil; The second drive unit applies the amplified audio signal at a set second amplification rate to the second voice coil; as well as The amplification setting unit, based on the position of the second voice coil in the axial direction represented by the displacement detected by the displacement detection unit, sets a smaller amplification rate than when the second voice coil is in a position where it cannot interact with the magnetic flux propagating in the gap, as the second amplification rate; and sets a larger amplification rate than when the second voice coil is in a position where it cannot interact with the magnetic flux propagating in the gap, as the first amplification rate.

6. The audio system according to any one of claims 1 to 5, characterized in that, The driving unit has a malfunction suppression unit, which operates the audio signal driving the first voice coil based on the displacement detected by the displacement detection unit, so as to prevent malfunction of the speaker.

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