Sound system

Abstract

To provide "an audio system" in which an overheated speaker can be quickly cooled.SOLUTION: In an audio system, when overheating of a speaker 2 is detected, a controller 9 controls a first selector 3 and a second selector 6 to input an audio signal output by an audio source device 1 to a cooling processing section 4 and causes output of the cooling processing section to be output to the speaker 2. In the cooling processing section 4, a mixer 46 mixes an audio signal obtained by removing, by a high-pass filter 41, a low-frequency component from the audio signal input to the cooling processing section 4 with a cooling signal at an infrasonic frequency generated by a cooling signal generator 42 and adjusted with a gain by a gain adjuster 44, and the mixed signal is output from the cooling processing section 4 via a nonlinear inverse filter 47. A gain setting section 45 of the cooling processing section 4 sets the gain of the gain adjuster 44 such that power of the cooling signal output from the gain adjuster 44 matches power of the low-frequency component of the audio signal input to the cooling processing section 4, the component being extracted by a low-pass filter 43.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a technique for suppressing overheating of a speaker in an acoustic system provided with a speaker.

Background Art

[0002] As a technique for suppressing overheating of a speaker in an acoustic system, there is known a technique in which the temperature of the speaker is detected by a temperature sensor, and when the detected temperature rise is excessive, the level of the acoustic signal output to the speaker is reduced (for example, Patent Document 1). Also, there is known a technique for correcting an acoustic signal for driving a speaker so that distortion of the output of the speaker with respect to an input is eliminated based on an equivalent circuit of the speaker (Patent Document 2). Also, there is known a technique of motional feedback that includes a sensor for detecting vibration of a diaphragm of a speaker and controls driving of the speaker according to the vibration detected by the sensor (for example, Patent Documents 3 and 4).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document {4}

Summary of the Invention

Problems to be Solved by the Invention

[0004] Suppressing speaker overheating is important for preventing speaker damage and maintaining output sound quality. Furthermore, as mentioned above, if a sensor is installed to detect vibrations of the speaker's diaphragm, suppressing speaker overheating becomes especially important from the standpoint of preventing damage to the sensor and its associated devices and ensuring their proper operation.

[0005] On the other hand, the aforementioned technology, which suppresses speaker overheating by reducing the level of the acoustic signal output to the speaker when the temperature rise is excessive, can suppress speaker heat generation, but it cannot be expected to cool the speaker quickly. Furthermore, reducing the level of the acoustic signal output to the speaker also reduces the volume of the audio content audible to the user, causing inconvenience and discomfort to the user.

[0006] Therefore, the present invention aims to quickly cool an overheated speaker without significantly affecting the user's listening experience of audio content. [Means for solving the problem]

[0007] To achieve the above objectives, the present invention provides an acoustic system comprising an audio source device that outputs a first acoustic signal and a speaker, the system comprising: an overheat detection means for detecting the occurrence of an overheating state of the speaker; a cooling processing unit that outputs a second acoustic signal; a switching means for switching the acoustic signal to be output to the speaker between the first acoustic signal and the second acoustic signal; and a control means for causing the switching means to switch the acoustic signal to be output to the speaker to the second acoustic signal when the overheat detection means detects the occurrence of an overheating state of the speaker while the switching means is outputting the first acoustic signal to the speaker. Here, the cooling processing unit outputs a signal as the second acoustic signal, which is a cooling signal with an ultra-low frequency, below the audible range, by mixing a signal obtained by removing the low-frequency component from the first acoustic signal output by the audio source device with a cooling signal with a frequency below the audible range, at least when the switching means is outputting the second acoustic signal to the speaker.

[0008] Here, the acoustic system includes a sensor provided in the speaker for detecting vibrations of the speaker's vibration system, and a signal correction means for correcting the first acoustic signal, and the switching means provides the first acoustic signal corrected by the signal correction means. and The audio signal to be output to the speaker may be switched between the second audio signal and the first audio signal, and the signal correction means may be configured to correct the first audio signal output by the audio source device based on the vibration detected by the sensor so that the output distortion of the speaker is canceled.

[0009] Furthermore, the above-described acoustic system may be provided with a temperature detection means for detecting the temperature of the speaker, and the overheat detection means may detect the occurrence of an overheating state of the speaker when the temperature detection means detects a temperature exceeding a first threshold, and the control means may be configured such that when the switching means is outputting the second acoustic signal to the speaker, and the temperature detection means detects a temperature below the second threshold, which is a threshold less than or equal to the first threshold, the switching means switches the acoustic signal output to the speaker back to the first acoustic signal.

[0010] Generally, for the same input voltage, the diaphragm displacement is greater in the ultra-low frequency band, which is below the lower limit of the audible range, than in the frequency band higher than the speaker's resonant frequency. Therefore, with this acoustic system, which outputs a second acoustic signal to the speaker that is a mixture of an ultra-low frequency cooling signal when the speaker overheats, the speaker's diaphragm can be vibrated with a larger amplitude than when the first acoustic signal is output to the speaker. This generates a larger airflow inside the speaker, allowing for more powerful and rapid cooling of the speaker by this airflow.

[0011] Furthermore, even while the second acoustic signal, which is mixed with the cooling signal, is output to the speaker, the output of the higher-frequency components of the acoustic signal output by the audio source device, which are more audibly apparent, is maintained. At the same time, the cooling signal mixed into the speaker output has a frequency below the lower limit of the audible range and is not audible to the user. Therefore, it is possible to suppress any significant impact on the user's listening experience of the audio content represented by the first acoustic signal output by the audio source device.

[0012] Next, the above-described acoustic system includes a gain adjustment means in the cooling processing unit that adjusts the gain of the cooling signal so that the power of the low-frequency component of the first acoustic signal output by the audio source device matches the power of the cooling signal. There are . By doing this, the mixing of cooling signals prevents the overall power of the second audio signal input to the speaker from becoming greater than when the first audio signal output by the audio source device is output directly to the speaker, thus preventing the speaker from overheating.

[0013] Furthermore, the above-described acoustic system may include a nonlinear inverse filter in the cooling processing unit that corrects the second acoustic signal output by the cooling processing unit so as to cancel the nonlinear distortion of the speaker. By doing so, it is possible to reduce the impact on the audible range caused by the nonlinear distortion of the speaker, which usually becomes noticeable when the speaker diaphragm is vibrated significantly. [Effects of the Invention]

[0014] As described above, according to the present invention, an overheated speaker can be quickly cooled without significantly affecting the user's listening to audio content. [Brief explanation of the drawing]

[0015] [Figure 1] This figure shows the configuration of an acoustic system according to an embodiment of the present invention. [Figure 2]It is a diagram showing a configuration of vibration detection according to an embodiment of the present invention. [Figure 3] It is a diagram showing an example of displacement - frequency characteristics of a speaker. [Figure 4] It is a flowchart showing a cooling control process according to an embodiment of the present invention.

Mode for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described. FIG. 1 shows a configuration of an acoustic system according to an embodiment. As shown in the figure, the acoustic system includes an audio source device 1 that outputs a digital acoustic signal of audio content such as music, a speaker 2, a first selector 3, a cooling processing unit 4, a signal correction unit 5, a second selector 6, an amplifier 7 for driving the speaker 2, a vibration measurement unit 8 that measures vibration / displacement of the vibration system of the speaker 2, and a control unit 9.

[0017] In such a configuration, the first selector 3 outputs an acoustic signal input from the audio source device 1 to either the cooling processing unit 4 or the signal correction unit 5 according to the control of the control unit 9. The cooling processing unit 4 outputs an acoustic signal obtained by mixing a cooling signal with an acoustic signal from which a low - frequency side component has been removed from the acoustic signal input from the first selector 3 to the second selector 6, and the signal correction unit 5 corrects the acoustic signal input from the first selector 3 so that the output distortion of the speaker is canceled and outputs it to the second selector 6. The second selector 6 outputs either the acoustic signal input from the cooling processing unit 4 or the acoustic signal input from the signal correction unit 5 to the amplifier 7 according to the control of the control unit 9, and the amplifier 7 converts and amplifies the acoustic signal input from the second selector 6 into an analog signal (voltage signal) to drive the speaker 2.

[0018] FIG. 2a shows a configuration of the speaker 2. As shown in the figure, speaker 2 has a yoke 201, a magnet 202, a top plate 203, a voice coil bobbin 204, a voice coil 205, a frame 206, a damper 207, a diaphragm 208, an edge 209, and a dust cap 210. In this diagram, with the upper part representing the front of the front speaker and the lower part representing the rear of the front speaker, the yoke 201 has a protruding portion 2011 in the center that projects forward, and an annular magnet 202 is provided on the outer circumference of the protruding portion 2011, with an annular top plate 203 provided on top of the magnet 202. This top plate 203 is made of a conductive material such as iron, and the yoke 201, magnet 202, and top plate 203 form a magnetic circuit 220.

[0019] The voice coil bobbin 204 has a hollow cylindrical shape, and the voice coil 205, to which the signal from the amplifier 7 is applied, is wound around its outer circumference. The protrusion 2011 of the yoke 201 is inserted from the rear into the hollow of the voice coil bobbin 204 so that the voice coil bobbin 204 can move back and forth relative to the yoke 201. The voice coil 205 is positioned between the protrusion 2011 of the yoke 201 and the top plate 203, through which the magnetic flux generated between the inner ends of the top plate 203 by the magnetic circuit 220 passes.

[0020] The diaphragm 208 has a shape roughly similar to the side of a frustum of a cone, with the front-to-back direction of the front speaker as the height direction, and its outer edge is connected to the front end of the frame 206 by an edge 209. The inner edge of the diaphragm 208 is fixed to the front end of the voice coil bobbin 204.

[0021] In this speaker 2 configuration, when a signal is applied to the voice coil 205 from the amplifier 7, the electromagnetic interaction between the magnetic vector generated from the magnetic circuit 220 and the acoustic signal flowing through the voice coil 205 causes the voice coil bobbin 204 to vibrate back and forth in accordance with the amplitude of the acoustic signal input from the amplifier 7. When the voice coil bobbin 204 vibrates, the diaphragm 208 connected to the voice coil bobbin 204 vibrates, generating sound corresponding to the input acoustic signal.

[0022] Next, as shown in the figure, with the axial direction of speaker 2 being the X direction and the radial direction being the Y direction, a displacement detection magnet 211 and a magnetic angle sensor 212 are assembled to speaker 2 as sensors to detect the displacement of the diaphragm 208 in the X direction. The displacement detection magnet 211 is fixed to the voice coil bobbin 204 so as to move up and down together with the voice coil bobbin 204, and the magnetic angle sensor 212 is fixed on the top plate 203 or the like so as not to change position relative to the magnetic circuit 220. The magnetic angle sensor 212 then detects the magnitudes of the X-direction component and the Y-direction component of the composite vector V, which is the resultant vector V of the magnetic vector generated by the magnetic circuit 220 and the magnetic vector generated by the displacement detection magnet 211, as shown in Figure 2b. It then outputs the X-detection value Vs, which indicates the magnitude of the X-direction component, and the Y-detection value Vc, which indicates the magnitude of the Y-direction component, to the vibration measurement unit 8.

[0023] Here, the magnitude and direction of the composite vector V (the combination of the magnitudes of the X-direction component and the Y-direction component) change according to the X-direction displacement of the displacement detection magnet 211 associated with the displacement of the voice coil bobbin 204. Therefore, the amount of X-direction displacement of the speaker 2's vibration system can be calculated from the X-detection value Vs and the Y-detection value Vc.

[0024] Furthermore, a temperature sensor 231 is attached to the magnetic circuit 220 of speaker 2, and the temperature sensor 231 outputs the detected temperature to the control unit 9. Returning to Figure 1, the vibration measurement unit 8 measures the vibration / displacement of the speaker 2's vibration system, including the voice coil bobbin 204 and diaphragm 208, from the output of the speaker 2's magnetic angle sensor 212, and outputs it to the control unit 9 and the signal correction unit 5. Furthermore, the control unit 9 receives input voltage and input current information from the speaker 2 or amplifier 7. Next, the cooling processing unit 4 includes a high-pass filter 41 (HPF41), a cooling signal generation unit 42, a low-pass filter 43 (LPF43), a gain adjustment unit 44, a gain setting unit 45, a mixer 46, and a nonlinear inverse filter 47. The input to the cooling processing unit 4 is the acoustic signal output by the first selector 3, and the acoustic signal input to the cooling processing unit 4 is then input to the high-pass filter 41 and the low-pass filter 43. The high-pass filter 41 outputs an audio signal to the mixer 46, with the low-frequency components (for example, components below 50Hz) removed from the input audio signal. The low-pass filter 43 extracts the low-frequency components from the input acoustic signal and outputs them to the gain setting unit 45. These low-frequency components are the same as those removed by the high-pass filter 41. The cooling signal generation unit 42 outputs a cooling signal, which is an ultra-low frequency signal (for example, a 10Hz sine wave) with a frequency below the lower limit of the audible range (20Hz), to the gain adjustment unit 44. The gain adjustment unit 44 adjusts the gain of the cooling signal output from the cooling signal generation unit 42 to the gain set by the gain setting unit 45, and outputs it to the mixer 46. The gain setting unit 45 calculates the effective value and power of the low-frequency component input from the low-pass filter 43, and sets the gain of the gain adjustment unit 44 so that the power of the cooling signal output from the gain adjustment unit 44 matches the power of the low-frequency component input from the low-pass filter 43.

[0025] The mixer 46 outputs an acoustic signal, which is a mixture of the acoustic signal with the low-frequency components removed from the high-pass filter 41 and the cooling signal input from the gain adjustment unit 44, to the nonlinear inverse filter 47. The nonlinear inverse filter 47 applies a transfer function to the audio signal input from the mixer 46 to cancel the nonlinear distortion of speaker 2, and outputs it to the second selector 6. In this state, when the first selector 3 outputs the audio signal input from the audio source device 1 to the cooling processing unit 4, and the second selector 6 outputs the audio signal input from the cooling processing unit 4, the audio signal output by the audio source device 1 is processed by the cooling processing unit 4, and the output of the cooling processing unit is output to the speaker 2.

[0026] In this state, the audio signal output to speaker 2 includes the high-frequency component of the audio signal output by audio source device 1 and the cooling signal, which is an ultra-low frequency audio signal. As shown in Figure 3, an example of the relationship between the displacement of the speaker 2's diaphragm and frequency, generally, for the same input voltage, the displacement of the diaphragm is greater in the ultra-low frequency band, which is below the lower limit of the audible range, than in the frequency band higher than the speaker 2's resonant frequency. Therefore, by mixing a cooling signal, which is an ultra-low frequency signal, with the low-frequency component of the acoustic signal output by the audio source device 1 and outputting it to the speaker 2, the diaphragm 208 of the speaker 2 can be vibrated with a larger amplitude than when the acoustic signal input from the audio source device 1 is output directly to the speaker 2. By vibrating the diaphragm 208 of the speaker 2 with a larger amplitude in this way, a larger airflow is generated inside the speaker 2, and this airflow allows for more powerful and rapid cooling of the speaker 2.

[0027] Furthermore, the gain of the cooling signal is adjusted and output so that it has the same power as the low-frequency components removed from the audio signal. This prevents the overall power of the audio signal input to speaker 2 from becoming greater than when the audio signal input from audio source device 1 is output directly to speaker 2, thus preventing speaker 2 from overheating.

[0028] Furthermore, the output from speaker 2 of the higher-frequency components of the acoustic signal output by audio source device 1, which are more audibly apparent, is maintained. At the same time, the cooling signal mixed with the output of speaker 2 has a frequency below the lower limit of the audible range and is not audible to the user. This suppresses a significant impact on the user's listening experience of the audio content represented by the acoustic signal output by audio source device 1.

[0029] Furthermore, if the diaphragm 208 of speaker 2 is vibrated with a large amplitude using a cooling signal that remains a sine wave, the nonlinear distortion of speaker 2 due to the nonlinearity of speaker 2's characteristics such as driving force, rigidity, and inductance will increase, causing distortion even in the audible range. However, since the acoustic signal mixed with the cooling signal is output to speaker 2 through a nonlinear inverse filter 47 that cancels the nonlinear distortion of speaker 2, the effects of such nonlinear distortion of speaker 2 are also reduced.

[0030] Next, the signal correction unit 5 corrects and outputs the audio signal output by the audio source device 1 so that distortion of the output due to the linear or nonlinear characteristics of the speaker 2 is eliminated. In other words, the signal correction unit 5 includes a nonlinear part correction filter 51, a linear inverse filter 52, an adaptive algorithm execution unit 53, an error calculation unit 54, and an estimation filter 55. The input to the signal correction unit 5 is the acoustic signal output by the first selector 3. The acoustic signal input to the signal correction unit 5 passes through the nonlinear correction filter 51 and the linear inverse filter 52 before being output to the second selector 6. The nonlinear correction filter 51 has a transfer function (filter coefficient) set such that when the speaker 2 is driven by the acoustic signal output by the nonlinear correction filter 51, the distortion of the speaker 2's output due to the nonlinear parameters of the speaker 2 with respect to the acoustic signal input to the signal correction unit 5 is canceled out. In other words, it is a transfer function that corrects the distortion due to the nonlinear parameters of the speaker 2.

[0031] The input to the estimation filter 55 is the acoustic signal that is input to the signal correction unit 5, and the output of the estimation filter 55 is input to the adaptive algorithm execution unit 53 and the error calculation unit 54. In addition, the estimation filter 55 is pre-set with a transfer function that represents the vibration characteristics of speaker 2.

[0032] The error calculation unit 54 uses the output of the estimation filter 55 to calculate the difference between the distortion-free vibration of speaker 2 relative to the acoustic signal input to the signal correction unit 5 and the actual vibration of speaker 2 measured by the vibration measurement unit 8. The linear inverse filter 52 is a variable filter, and the linear inverse filter 52, the adaptive algorithm execution unit 53, and the estimation filter 55 constitute an adaptive filter. The adaptive algorithm execution unit 53 uses the output of the estimation filter 55 as a reference signal and the difference calculated by the error calculation unit 54 as the error, and performs adaptive operation to update the transfer function (filter coefficients) of the linear inverse filter 52 to minimize the error using the Filtered-x LMS algorithm or the like.

[0033] Here, when the first selector 3 outputs the audio signal input from the audio source device 1 to the signal correction unit 5, and the second selector 6 outputs the audio signal input from the signal correction unit 5, the signal correction unit 5 corrects the audio signal output by the audio source device 1 so that the distortion of the output due to the linear or nonlinear characteristics of the speaker 2 is eliminated, and this corrected audio signal is output to the speaker 2.

[0034] Next, the cooling control process performed by the control unit 9 will be described. The procedure for this cooling control process is shown in Figure 4. As shown in the figure, the control unit 9 acquires the temperature of speaker 2 in the cooling control process (step 402). The temperature of speaker 2 is acquired from the temperature sensor 231. However, the temperature of speaker 2 may also be calculated by estimating the amount of heat generated by speaker 2 from the history of the input voltage and input current of speaker 2, which are indicated by the information input from speaker 2 or amplifier 7.

[0035] Then, it is determined whether the temperature of speaker 2 exceeds the threshold Th1 (step 404). The threshold Th1 is set to a temperature slightly lower than the upper limit of the temperature at which normal operation of both speaker 2 and magnetic angle sensor 212 is guaranteed. Then, if the temperature of speaker 2 does not exceed the threshold Th1, the output destination of the acoustic signal input from audio source device 1 of the first selector 3 is set to signal correction unit 5 (step 406), and the output of the second selector 6 is set to the acoustic signal output by signal correction unit 5 (step 408).

[0036] Then, the process of obtaining the temperature of speaker 2 (step 410) and determining whether the temperature of speaker 2 exceeds the threshold Th1 (step 412) is repeated until it is determined that the temperature of speaker 2 exceeds the threshold Th1. If it is determined that the temperature of speaker 2 exceeds the threshold Th1 (step 412), the process proceeds to step 414. On the other hand, if it is determined in step 404 that the temperature of speaker 2 exceeds threshold Th1, the process proceeds to step 414. Then, if the process proceeds from step 404 or step 412 to step 414, the output destination of the audio signal input from the audio source device 1 of the first selector 3 is set to the cooling processing unit 4 (step 414), and the output of the second selector 6 is set to the audio signal output by the cooling processing unit 4 (step 416).

[0037] Then, the process of obtaining the temperature of speaker 2 (step 418) and determining whether the temperature of speaker 2 is below the threshold Th2 (step 420) is repeated until it is determined that the temperature of speaker 2 is below the threshold Th2. Here, the threshold Th2 ≤ Th1. Then, if it is determined in step 420 that the temperature of speaker 2 is below the threshold Th2, the process proceeds to step 406. The cooling control process performed by the control unit 9 has been described above. With this cooling control process, when the temperature of speaker 2 exceeds the threshold Th1, the audio signal output by audio source device 1 is processed by the cooling processing unit 4 until the temperature of speaker 2 falls below the threshold Th2, and the output of the cooling processing unit 4 is output to speaker 2. Furthermore, during periods other than the time when the temperature of speaker 2 exceeds threshold Th1 and then falls below threshold Th2, the audio signal output by audio source device 1 is processed by signal correction unit 5, and the output of signal correction unit 5 is output to speaker 2. Embodiments of the present invention have been described above. In this embodiment, the control unit 9 may estimate the change in the nonlinear characteristics of the speaker 2 according to the temperature of the speaker 2, and process the transfer functions of the nonlinear inverse filter 47 and the nonlinear correction filter 51 of the cooling unit to match the current nonlinear characteristics of the speaker 2 according to the estimated change.

[0038] Furthermore, the configuration described above, which uses the cooling processing unit 4 to cool the speaker 2, can also be applied to acoustic systems that do not have a signal correction unit 5, a vibration measurement unit 8, a displacement detection magnet 211, or a magnetic angle sensor 212, by inputting the output of the first selector 3 to the second selector 6 instead of the output of the signal correction unit 5. [Explanation of symbols]

[0039] 1...Audio source equipment, 2...Speaker, 3...First selector, 4...Cooling processing unit, 5...Signal correction unit, 6...Second selector, 7...Amplifier, 8...Vibration measurement unit, 9...Control unit, 41...High-pass filter, 42...Cooling signal generation unit, 43...Low-pass filter, 44...Gain adjustment unit, 45...Gain setting unit, 46...Mixer, 47...Nonlinear inverse filter, 51...Nonlinear part correction filter, 52...Linear inverse filter, 53...Adaptive algorithm execution unit, 54...Error calculation unit, 55...Estimation filter, 201...Yoke, 202...Magnet, 203...Top plate, 204...Voice coil bobbin, 205...Voice coil, 206...Frame, 207...Damper, 208...Diaphragm, 209...Edge, 210...Dust cap, 211...Displacement detection magnet, 212...Magnetic angle sensor, 220...Magnetic circuit, 231...Temperature sensor, 2011...Convex part.

Claims

1. An audio system comprising an audio source device that outputs a first acoustic signal and a speaker, An overheat detection means for detecting the occurrence of an overheating state in the speaker, A cooling processing unit that outputs a second acoustic signal, A switching means for switching the audio signal to be output to the speaker between the first audio signal and the second audio signal, The switching means is outputting the first acoustic signal to the speaker, and when the overheat detection means detects that the speaker is overheating, the switching means is controlled to switch the acoustic signal output to the speaker to the second acoustic signal. The cooling processing unit outputs a second acoustic signal, which is a cooling signal with an ultra-low frequency range below the audible range, by mixing the low-frequency component from the first acoustic signal output by the audio source device with the cooling signal, when the switching means is outputting the second acoustic signal to the speaker, and further, The sound system is characterized in that the cooling processing unit has gain adjustment means for adjusting the gain of the cooling signal so that the power of the low-frequency component of the first sound signal output by the audio source device matches the power of the cooling signal.

2. The acoustic system according to claim 1, A sensor provided in the speaker detects vibrations in the speaker's vibration system, The system includes signal correction means for correcting the first acoustic signal, The switching means switches the audio signal to be output to the speaker between the first audio signal and the second audio signal, which have been corrected by the signal correction means. The signal correction means is characterized by correcting the first acoustic signal output by the audio source device based on the vibration detected by the sensor, so as to cancel the output distortion of the speaker.

3. The acoustic system according to claim 1, The speaker has a temperature detection means for detecting the temperature of the speaker, The overheat detection means detects the occurrence of an overheating state of the speaker when the temperature detection means detects a temperature exceeding a first threshold, The control means is characterized in that, when the switching means is outputting the second acoustic signal to the speaker, the temperature detection means detects a temperature below the second threshold, which is below the first threshold, and causes the switching means to switch the acoustic signal output to the speaker to the first acoustic signal.

4. The acoustic system according to claim 2, The speaker has a temperature detection means for detecting the temperature of the speaker, The overheat detection means detects the overheating state of the speaker when the temperature detection means detects a temperature exceeding a first threshold, The control means is characterized in that, when the switching means is outputting the second acoustic signal to the speaker, the temperature detection means detects a temperature below the second threshold, which is below the first threshold, and causes the switching means to switch the acoustic signal output to the speaker to the first acoustic signal.

5. The acoustic system according to claim 1, 2, 3, or 4, The acoustic system is characterized in that the cooling processing unit has a nonlinear inverse filter that corrects the second acoustic signal output by the cooling processing unit so as to cancel the nonlinear distortion of the speaker.

6. The acoustic system according to claim 1, 2, 3, or 4, The cooling unit includes a gain adjustment means for adjusting the gain of the cooling signal so that the power of the low-frequency component of the first acoustic signal output by the audio source device matches the power of the cooling signal, An acoustic system characterized by having a nonlinear inverse filter that corrects the second acoustic signal output by the cooling processing unit so as to cancel the nonlinear distortion of the speaker.

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