JP2018186322A - Electronic device equipped with speaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic device capable of diagnosing abnormality of speaker wiring when a plurality of speakers are connected to one channel.SOLUTION: A power amplifier 100 of the present invention includes a self-diagnosis function 200 for diagnosing abnormality of speaker wiring. The self-diagnosis function 200 includes: an input switching part 260 for inputting a diagnosis signal to a drive circuit 230; the drive circuit 230 for driving each of a plurality of speakers 140, 160, 180 by the diagnosis signal inputted from the input switching part 260; a current detection part 220 for detecting a current when a speaker is driven by the drive circuit 230; and a control part 250 for diagnosing wiring based on the detected current.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an electronic device having a speaker, and more particularly to an electronic device having a function of diagnosing whether or not there is an abnormality in a speaker line (wiring).

  When an electronic device such as a power amplifier equipped with a speaker is shipped, a function for diagnosing whether or not the speaker wiring is abnormal may be required. For example, an information device including a speaker disclosed in Patent Document 1 supplies a test signal having a frequency outside the human audible frequency band to an amplifier during self-diagnosis, and detects a signal level of a ripple component extracted from the amplifier when the speaker is driven. Thus, it is determined whether or not the speaker is normally connected to the amplifier. The abnormality detection system for speaker wiring in Patent Document 2 can detect open / short with high reliability when the number of output terminals on the speaker drive side is smaller than the number of speakers. Specifically, the speaker is driven by a normal phase test signal and a negative phase test signal, and the sound of the two is input, and whether or not the connection state of the speaker is appropriate is determined based on the level difference.

JP 2001-251700 A JP 2014-107663 A

  As described above, some power amplifiers have a built-in self-diagnosis function for diagnosing the suitability of speaker wiring. FIG. 1 shows a configuration of a self-diagnosis function of a conventional power amplifier. The power amplifier 10 is connected to the speaker 20 via a positive side terminal 22 and a negative side terminal 24. During normal operation, the power amplifier 10 is driven by the source current Isource flowing from the supply voltage Vcc of the power supply unit 12 to the speaker 20 via the positive terminal 220 based on the input audio signal, and from the speaker 20 to the negative terminal 24. The speaker 20 is AC driven by a sink current Isink that flows to the ground via.

  On the other hand, when diagnosing the speaker, the control unit 30 changes the supply voltage Vcc of the power supply unit 12 to a DC voltage Vs of, for example, 5 V, and passes the coil of the speaker 20 between the power supply unit 12 and the ground. A current path is formed, and an abnormality in the wiring of the speaker 20 is detected based on the current flowing therethrough. The differential amplifier 40 detects the presence or absence of a power fault between the power supply unit 12 and the positive terminal 22, and if there is a power fault, a voltage larger than the reference voltage Vref is input and detected. To do. The differential amplifier 42 detects the presence or absence of a short circuit between the positive terminal 22 and the negative terminal 24. If there is a short circuit between the terminals, the input voltage difference becomes very small. This is detected. The differential amplifier 44 detects the presence or absence of a ground fault. If there is a ground fault, a voltage smaller than the reference voltage Vref is input and detected. These detection results are provided to the control unit 30, and the control unit 30 outputs the diagnosis results by, for example, an alarm.

  The above diagnostic method uses a DC current path to detect speaker wiring power supply faults, ground faults, and short-circuit / open abnormalities between terminals. Limited to wiring connection. For example, when a capacitor or the like that cuts off a direct current is connected to the speaker, such as a tweeter speaker that outputs a high sound range, the diagnosis cannot be performed. Further, even when a plurality of speakers are connected to one channel of the power amplifier via the speaker network, there is a problem that it is impossible to diagnose which speaker wiring is abnormal.

  An object of the present invention is to solve such a conventional problem, and to provide an electronic device capable of diagnosing abnormality of speaker wiring even when a plurality of speakers are connected to at least one channel. To do.

  An electronic device according to the present invention has a function of driving a speaker based on an audio signal, and is connected to at least one channel and has a plurality of speakers having different frequency characteristics, and wirings of the plurality of speakers. Diagnostic means for diagnosing abnormalities, the diagnostic means detecting the current consumption when each of the plurality of speakers is driven, and whether there is an abnormality in each speaker wiring based on the detected current consumption Determination means for determining.

  Preferably, the diagnostic unit generates a diagnostic signal corresponding to the frequency characteristic of each speaker, and a driving unit outputs a driving signal for driving the speaker based on the diagnostic signal generated by the generating unit. Have Preferably, the diagnostic means includes input switching means for switching input of the diagnostic signal or audio signal to the driving means, and input switching control means for controlling switching of input of the input switching means, and the input switching The control unit causes the driving unit to input the diagnostic signal at the time of diagnosis. Preferably, the generating unit generates a corresponding diagnostic signal according to the number of diagnoses and the diagnostic order of each speaker, and the generated diagnostic signals are sequentially input to the driving unit. Preferably, the plurality of speakers are connected to the driving means via a filter circuit network corresponding to the frequency characteristics of the speakers. Preferably, the determination unit compares the detected current consumption with a threshold value, and determines that there is an open in the speaker wiring to be diagnosed when the current consumption is lower than a threshold value by a certain amount or more, and the current consumption is lower than the threshold value. When larger than a certain level, it is determined that there is a short circuit in the wiring of the speaker to be diagnosed. Preferably, the determination means sets a threshold value for determining the total current consumption of the overlapping speakers when making a diagnosis in a range where the frequency characteristics of the speakers overlap. Preferably, the plurality of speakers includes a speaker selected from a tweeter speaker, a squawker speaker and a woofer.

  According to the present invention, the current consumption when each of the plurality of speakers is driven is detected, and the presence / absence of abnormality of each speaker wiring is determined based on the detected current consumption. Even when a speaker is connected or a plurality of speakers are connected via a network, it is possible to diagnose whether there is an abnormality in the wiring of the speaker.

It is a figure explaining the structure of the self-diagnosis function of the conventional power amplifier. It is a figure which shows the network speaker structural example which concerns on the Example of this invention. It is a figure explaining the structure of the self-diagnosis function of the power amplifier which concerns on the Example of this invention. It is a graph which shows the frequency characteristic of 3 way speaker connected to a power amplifier. It is a block diagram which shows the functional structure of the diagnostic program based on the Example of this invention. It is a figure which shows the example of storage of the diagnostic signal corresponding to the speaker connected. It is an operation | movement flow explaining the diagnostic method of the speaker wiring which concerns on the Example of this invention. FIG. 8A shows an example in which the frequency characteristics of speakers overlap, and FIG. 8B shows the relationship between power consumption and frequency at that time.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. In a preferred aspect of the present invention, the electronic device including a speaker is, for example, a speaker system, a power amplifier, an audio device, an in-vehicle device, or the like. The use of the power amplifier and the audio device is not particularly limited, and for example, it can be mounted on a vehicle such as a moving body and operated by electric power supplied from a battery or the like. In a preferred embodiment of the present invention, the speaker connected to the electronic device is a multi-way such as a 2-way, a 3-way or the like.

  FIG. 2 is a diagram showing a schematic configuration of a power amplifier (or speaker system) including a multi-way speaker according to the first embodiment of the present invention. For example, the power amplifier 100 inputs a reproduced audio signal, generates a drive signal obtained by amplifying the input audio signal according to a setting of a volume or the like, and generates the generated drive signal from the positive terminal Tp and the negative terminal Tn. By outputting, the connected speaker is AC driven. A speaker is connected to the positive terminal Tp and the negative terminal Tn of the power amplifier 100 via the LC network 120. The figure shows an example in which three-way speakers 140, 160, and 180 are connected.

  The LC network 120 filters the drive signal output from the power amplifier 100 according to the frequency characteristics of the connected speaker. For example, when the speaker 140 is a tweeter speaker that outputs a high sound range, the LC network 120 includes a high-pass filter that passes a high-frequency band of a drive signal from the power amplifier 100, and the drive signal is output to the tweeter speaker. When the speaker 160 is a squawker speaker that outputs a mid-range, the LC network 120 includes a band-pass filter that passes the middle band of the drive signal from the power amplifier 100, and this signal is output to the squawker speaker. When the speaker 180 is a woofer that outputs a low sound range, the LC network 120 includes a low-pass filter that passes a low frequency band from the power amplifier 100, and this drive signal is output to the woofer.

  The example of FIG. 2 shows an example in which a 3-way speaker is connected to one channel (one set of positive side terminal Tp and negative side terminal Tn). A speaker may be connected. Furthermore, the power amplifier 100 may include a plurality of channels, and multi-way speakers may be connected to the plurality of channels, respectively. When the speaker system shown in FIG. 2 is mounted on a moving body such as an automobile, multi-way speakers are arranged on the left and right of the front seat, the left and right of the rear seat, the center of the front seat, etc., and the 5.1 channel surround space. May be included. Further, the example of FIG. 2 shows an example in which a plurality of speakers are connected to the power amplifier 100, but the aspect of the electronic device is not limited to this, and the speaker may include a power amplifier.

  The power amplifier 100 of this embodiment is equipped with a self-diagnosis function 200 for diagnosing an abnormality in speaker wiring in addition to a normal function of driving a speaker. FIG. 3 is a diagram showing a configuration relating to a self-diagnosis function built in the power amplifier 100 and a circuit configuration of the LC network 120. The self-diagnosis function 200 is based on a power supply unit 210 that supplies power Vcc to the power amplifier 100, a current detection unit 220 that detects a current of the drive signal when the speaker is driven by the drive signal, an audio signal, and a diagnostic signal. A drive circuit 230 that generates an amplified drive signal and outputs the drive signal from the positive terminal Tp and the negative terminal Tn, a memory 240, a control unit 250 including a function for controlling a diagnostic function, an audio signal input from the outside, or An input switching unit 260 that switches input of a diagnostic signal at the time of diagnosis is included.

  In the following description, 140 is a tweeter speaker, 160 is a squawker speaker, and 180 is a woofer. The LC network 120 includes a high-pass filter 122 that passes a high-frequency band drive signal corresponding to the frequency characteristic of the tweeter speaker 140, and a band-pass filter that passes a medium-frequency band drive signal corresponding to the frequency characteristic of the squawker speaker 160. 124 and a low-pass filter 126 that passes a low frequency band corresponding to the frequency characteristic of the woofer 180. FIG. 4 shows a graph of frequency characteristics of the tweeter speaker 140, the squawker speaker 160, and the woofer 180. The high frequency range output from the tweeter speaker 140 is ft1 to ft2, the mid frequency range output from the squawker speaker 160 is fs1 to fs2, and the low frequency range output from the woofer 180 is fw1 to fw2. It is.

  In one preferred example, the control unit 250 executes a diagnostic program for diagnosing abnormalities in speaker wiring. The control unit 250 includes, for example, a microcontroller for executing a diagnostic program stored in the ROM / RAM. FIG. 5 shows a functional configuration of the diagnostic program 300. The diagnosis program 300 includes a diagnosis start detection unit 310, a diagnosis signal generation unit 320, an input switching control unit 330, a current consumption acquisition unit 340, and an abnormality presence / absence determination unit 350.

  The diagnosis start detection unit 310 detects the timing for starting the self-diagnosis function 200. For example, the power amplifier 100 includes a test terminal (not shown), and when a diagnosis start signal is input to the test terminal, the diagnosis start detection unit 310 detects the diagnosis start signal to start diagnosis. Alternatively, the power amplifier 100 includes an external connection terminal (not shown), and when a diagnosis start signal is input from an external device or an external system via the external connection terminal, the diagnosis start detection unit 310 starts diagnosis. Alternatively, when the power amplifier 100 is incorporated in an audio device or a vehicle-mounted device, when there is an instruction from the audio device or the vehicle-mounted device, the diagnosis start detection unit 310 starts diagnosis in response to the instruction. Alternatively, when the power amplifier 100 is turned on, the diagnosis start detection unit 310 starts diagnosis as one of the power-up sequences. The diagnosis of the speaker wiring is preferably performed before the power amplifier is shipped as a product.

  When the diagnosis start detection unit 310 detects the start of diagnosis, the diagnosis signal generation unit 320 generates a diagnosis signal. The diagnostic signal is an audio signal for actually AC driving a connected speaker, and the diagnostic signal generation unit 320 generates a diagnostic signal having a specific frequency corresponding to each frequency characteristic of the connected speaker. For example, when the tweeter speaker 140, the squawker speaker 160, and the woofer 180 are connected, the diagnostic signal generation unit 320 generates an audio signal having a high frequency as a diagnostic signal when diagnosing the tweeter speaker 140. When diagnosing 160, an audio signal having a mid-range frequency is generated as a diagnostic signal, and when diagnosing the woofer 180, an audio signal having a low-frequency range is generated as a diagnostic signal.

  In one preferred example, the memory 240 stores a diagnostic signal for use with a connected speaker, and the diagnostic signal generator 320 can read out a diagnostic signal corresponding to the speaker to be diagnosed from the memory 240. For example, as shown in FIG. 6, the memory 240 stores a diagnostic signal having a frequency corresponding to the frequency characteristic of the speaker. The diagnostic signal may be either a sine wave signal or a rectangular wave signal, for example.

  The input switching control unit 330 controls the input switching unit 260 so that the diagnostic signal generated by the diagnostic signal generation unit 320 is input to the drive circuit 230 when the diagnosis start detection unit 310 detects the diagnosis start of the speaker. To do. The input switching unit 330 sequentially switches the input of the diagnostic signal generated by the diagnostic signal generation unit 320 according to the number of speakers to be diagnosed (three in this example) and the order of diagnosis. For example, when the time required for diagnosis of one speaker has elapsed, the input switching control unit 330 causes the drive circuit 230 to input a diagnosis signal for diagnosing the next speaker. In another example, the input switching control unit 330 may cause the next diagnostic signal to be input to the drive circuit 230 after a certain time has elapsed after the diagnostic signal is input to the drive circuit 230.

  The consumption current acquisition unit 340 acquires the current detected by the current detection unit 220 when the speaker is driven by the drive circuit 230 according to the diagnostic signal. That is, when driving the speaker, the drive circuit 230 is supplied with the power supply voltage Vcc from the power supply unit 210, and a source current flows from the positive side terminal Tp to the speaker via the LC network 120. It is detected by the detection unit 220. The consumption current acquisition unit 340 acquires the consumption current detected by the current detection unit 220. In addition, the current consumption acquisition unit 340 may calculate an average value of a plurality of detection results when a plurality of detection results are acquired during the period in which the diagnosis target speaker is being driven. The consumption current acquisition unit 340 acquires the consumption current for each of when a plurality of speakers are diagnosed, and provides the acquisition result to the abnormality presence / absence determination unit 350.

  The abnormality presence / absence determination unit 350 determines the presence / absence of an abnormality in the speaker wiring based on the consumption current acquired by the consumption current acquisition unit 340. The abnormality presence / absence determination unit 350 determines the presence / absence of an abnormality such as a short circuit or an open of the speaker by comparing the acquired power consumption with a threshold value prepared in advance. The threshold value can be set based on a current that will be consumed if a normally connected speaker is driven. For example, the threshold value may be calculated from the rated power consumption of the speaker. The threshold value is set for each speaker to be diagnosed. For example, the threshold value of the speaker to be connected is stored in the memory 240 and is read from the memory 240 at the time of determination.

  For example, in the diagnosis of the tweeter speaker 140, if the current consumption is smaller than the threshold value by a certain amount or more, it is determined that the wiring of the tweeter speaker 140 is open. If the power consumption is greater than a certain threshold value than the threshold, it is determined that there is a short circuit in the tweeter speaker wiring. Similarly, in the diagnosis of the squawker speaker 160, if the current consumption is smaller than the threshold value by a certain amount or more, it is determined that the wiring of the squawker speaker is open, and if the current consumption is larger than the threshold value by a certain value, the squawker speaker It is determined that there is a short in the wiring. The diagnosis of the woofer can be performed by the DC current as in the conventional case because the LC network 120 does not shield the DC current. However, in the woofer diagnosis, as in the case of the tweeter speaker or the squawker speaker, the open current / short circuit may be diagnosed by comparing the current consumption with the threshold value.

  Next, FIG. 7 shows a flow of the diagnostic operation of this embodiment. Here, it is assumed that diagnosis is performed in the order of the tweeter speaker 140, the squawker speaker 160, and the woofer 180. First, whether or not diagnosis is started is detected by the diagnosis start detection unit 310 (S100). When the diagnosis start is detected, the diagnosis signal generation unit 320 diagnoses the tweeter speaker 140 according to the diagnosis order of the speakers. For this purpose, a diagnostic signal is generated (S102). As shown in FIG. 4, this diagnostic signal is an audio signal in the frequency band ft1 to ft2 of the sound range output from the tweeter speaker 140. When the diagnostic signal is generated, the input switching control unit 330 inputs the diagnostic signal for tweeter to the driving circuit 230 via the input switching unit 260, and the driving signal output from the driving circuit 230 passes through the high pass filter 122. The tweeter speaker 140 is then driven (S104). While the tweeter speaker 140 is being driven, current consumption is detected, which is acquired by the current consumption acquisition unit 340 and provided to the abnormality presence / absence determination unit 350 (S106).

  After a certain period of time has elapsed or the current consumption during driving of the tweeter speaker 140 is acquired, a diagnostic signal for the squawker is generated (S108), and the squawker speaker 160 is driven based on the diagnostic signal for the squawker (S110). . The diagnostic signal for the squawker is an audio signal in the frequency band fs1 to fs2 of the sound range output from the squawker speaker shown in FIG. Current consumption is detected while the squawker speaker 160 is being driven, and this is provided to the abnormality presence / absence determination unit 350 (S112).

  Next, the diagnosis of the woofer is made by applying a DC signal by the same method as in the prior art shown in FIG. 1 (S114). Next, the abnormality presence / absence determination unit 340 compares the current consumption detected at the time of diagnosis of the tweeter speaker and the squawker speaker with a threshold value, and determines whether or not there is an abnormality in the wiring of these speakers (S116). Further, it is determined whether or not the woofer has an abnormality in the wiring of the woofer based on the diagnosis result. When it is determined that there is an abnormality, the abnormality presence / absence determination unit 340 can output an alarm indicating the abnormality (S120). In this case, an alarm corresponding to the type of open or short circuit abnormality may be output. When outputting an alarm, the power amplifier 100 shown in FIGS. 2 and 3 includes an output unit for outputting a diagnosis result.

  As described above, according to the present embodiment, the presence or absence of abnormality in the speaker wiring is determined based on the current consumption when the speaker is driven by the diagnostic signal corresponding to the frequency characteristic of the connected speaker. It is possible to diagnose whether there is an abnormality in a tweeter speaker, a squawker speaker, or a multi-way speaker wiring connected to the LC network.

  Next, a modification of the present embodiment will be described. In the above embodiment, the diagnostic signal generator 320 prepares in advance a diagnostic signal for the speaker to be diagnosed, but the method for generating the diagnostic signal is not limited to this. In the modification, the diagnostic signal generation unit 320 may extract a diagnostic signal corresponding to the frequency characteristic of a speaker to be diagnosed from a full-range frequency signal or a white noise signal. For example, when diagnosing the tweeter speaker 140, the diagnostic signal generation unit 320 generates a diagnostic signal having a frequency corresponding to the frequency characteristic of the tweeter speaker from the white noise signal, and when diagnosing the squawker speaker, A diagnostic signal having a frequency corresponding to the frequency characteristic of the squawker may be generated. In this case, the diagnostic signal generation unit 320 may include a high-pass filter or a band-pass filter.

  Next, a second embodiment of the present invention will be described. The second embodiment relates to a diagnosis method when the frequency characteristics of speakers largely overlap. As shown in FIG. 8A, the frequency characteristics of each speaker partially overlap, but in particular, the frequency characteristics of woofer and squawker largely overlap. Since the frequency characteristics of each speaker can be known in advance, the wiring of the speakers can be diagnosed by changing the threshold value for determining the measured current consumption in the portion where the frequency characteristics overlap.

  FIG. 8B shows current consumption when the speaker of FIG. 8A is used. In the portion where the frequency specification of the woofer and the squawker speaker overlaps, the woofer and the squawker speaker are driven simultaneously, so the current consumption is the sum of both. (1) to (4) are frequencies at the time of diagnosis based on the diagnosis signal, and the presence / absence of abnormality at this time is determined as follows.

Diagnosis (1):
The frequency f1 of the diagnostic signal is a woofer frequency band (fw1 <f1 <fw2). In this case, since only the woofer is driven, a threshold value Th1 for determining the current consumption when the woofer is driven is set. If the detected current consumption is smaller than the threshold Th1 by a certain value or more, it is determined that the woofer wiring is open, and if the current consumption is larger than the threshold Th1 by a certain value or more, it is determined that the woofer wiring is short-circuited.

Diagnosis (2):
The frequency f2 of the diagnostic signal overlaps with the woofer and squawker frequency bands (fs1 <f2 <fw2). In this case, since the woofer and the squawker are driven, a threshold value Th2 for determining the current consumption when both the woofer and the squawker are driven is set. If the detected current consumption is more than a certain value smaller than the threshold value Th2, it is determined that there is an open in the wiring of either the woofer or the squawker speaker. If the consumption current is greater than a certain value greater than the threshold value T2, either the woofer or the squawker speaker is determined. It is determined that there is a short circuit in the wiring.

Diagnosis (3):
The frequency f3 of the diagnostic signal is the frequency band of the squawker speaker (fs1 <f3 <fs2). In this case, since only the squawker speaker is driven, a threshold value Th3 for determining the current consumption when the squawker speaker is driven is set. If the detected current consumption is smaller than the threshold value Th3 by a certain amount or more, it is determined that the wiring of the squawker speaker is open, and if the consumption current is larger than the threshold value Th3 by a certain value or more, it is determined that there is a short circuit in the wiring.

Diagnosis (4):
The frequency f4 of the diagnostic signal is the frequency band of the tweeter speaker (ft1 <f4 <ft2). In this case, since only the tweeter speaker is driven, a threshold value Th4 for determining the current consumption when the tweeter speaker is driven is set. If the detected current consumption is smaller than the threshold Th4 by a certain amount or more, it is determined that the tweeter speaker wiring is open, and if the consumption current is larger than the threshold Th4 by a certain amount or more, it is determined that there is a short circuit in the tweeter speaker wiring.

  As described above, according to the present embodiment, even when the frequency characteristics of speakers overlap, diagnosis of wiring of speakers in an overlapping relationship is performed by appropriately setting a threshold for determining current consumption. be able to.

  The preferred embodiment of the present invention has been described in detail above. However, the present invention is not limited to the specific embodiment, and various modifications and variations are possible within the scope of the gist of the invention described in the claims. It can be changed.

100: Power amplifier 120: LC network 140: Speaker (tweeter) 160: Speaker (squaker)
180: Speaker (woofer) 200: Self-diagnosis function 210: Power supply unit 220: Current detection unit 230: Drive circuit 240: Memory 250: Control unit 260: Input switching unit

Claims (8)

An electronic device having a function of driving a speaker based on an audio signal,
A plurality of speakers connected to at least one channel and having different frequency characteristics;
Diagnostic means for diagnosing abnormalities in each wiring of a plurality of speakers,
The diagnostic means includes detection means for detecting current consumption when each of the plurality of speakers is driven,
An electronic device comprising: determination means for determining whether or not each speaker wiring is abnormal based on the detected current consumption. The diagnostic unit includes a generation unit that generates a diagnostic signal corresponding to the frequency characteristic of each speaker, and a driving unit that outputs a drive signal for driving the speaker based on the diagnostic signal generated by the generation unit. The electronic device according to claim 1. The diagnostic means includes input switching means for switching input of the diagnostic signal or audio signal to the driving means, and input switching control means for controlling switching of input of the input switching means, and the input switching control means The electronic apparatus according to claim 2, wherein the diagnostic signal is input to the driving unit at the time of diagnosis. The electronic device according to claim 2, wherein the generation unit generates a corresponding diagnostic signal according to the number of diagnoses and the diagnostic order of each speaker, and the generated diagnostic signal is sequentially input to the driving unit. The electronic device according to claim 2, wherein the plurality of speakers are connected to the driving unit via a filter circuit network corresponding to a frequency characteristic of the speakers. The determination means compares the detected current consumption with a threshold value, and when the current consumption is smaller than a threshold value by a certain value, determines that there is an open in the speaker wiring to be diagnosed. The electronic device according to claim 1, wherein when it is large, it is determined that there is a short circuit in the wiring of the speaker to be diagnosed. The electronic device according to claim 6, wherein the determination unit sets a threshold for determining a total current consumption of the overlapping speakers when making a diagnosis in a range where the frequency characteristics of the speakers overlap. The electronic device according to claim 1, wherein the plurality of speakers includes a speaker selected from a tweeter speaker, a squawker speaker, and a woofer.

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