JP6196860B2 - Speaker system - Google Patents

Description

The present invention relates to a speaker system in which a digital amplifier is directly connected to a voice coil.

In recent years, music is stored in a storage device such as an optical disk device or a flash memory, stored on an Internet cloud, or supplied by streaming via the Internet.
These music (sounds) are digitized and stored in a storage medium.

Further, in a music playback apparatus including a speaker, an analog or digital signal is amplified by an amplifier, and the speaker is driven using the amplified signal.
As amplifiers, analog amplifiers (class A, class B and AB amplifiers) that amplify analog signals and digital amplifiers (class D amplifiers) that amplify digital signals are known. Since the class D amplifier amplifies the digital signal, the digital signal as described above can be amplified without being analogized. However, in the class D amplifier, a PWM (Pulse Width Modulation) signal is amplified as a digital signal that is pulse-width modulated as a digital signal. For example, what is stored in a storage medium is PCM (Pulse Width Modulation). In the case of CODE Modulation) data, it is necessary to convert this into a PWM signal.

  Such a class D amplifier has advantages in that it is more efficient than each of the above-mentioned analog amplifiers, and therefore has low power consumption, low heat generation, and easy miniaturization. However, in the class D amplifier 1, conventionally, electromagnetic non-interference or electromagnetic compatibility (EMC) is ensured due to electromagnetic radiation of a noise component signal included in the PWM signal. Has been a problem (see, for example, Patent Document 1).

  That is, a PWM signal in a general class D amplification system includes a noise component signal in addition to a signal (audio signal) in an audible band (20 Hz to 20 kHz) to be originally reproduced. That is, a rectangular wave such as a PWM signal includes noise as a harmonic component.

  Patent Document 1 discloses that a PWM signal in a case where the duty is 50% includes a noise component (primary) (hereinafter referred to as a noise component signal) having a fundamental frequency f1 (PWM oscillation frequency in the case where the duty is 50%). And a signal of an odd-order harmonic component such as the third, fifth, and seventh orders with respect to the signal of the fundamental frequency component. In general, it is described that the fundamental frequency is a frequency between 400 kHz and 500 kHz.

In addition, in Patent Document 1, in addition to the fundamental frequency component signal and the odd harmonic component signal, the PWM signal when the duty is other than 50%, as a noise component signal,
It is described that signals of even-order harmonic components such as second-order, fourth-order, and sixth-order with respect to signals of fundamental frequency components are included.

As described in Patent Document 1, such a noise component signal is basically eliminated by arranging a low-pass filter on the output side of the class D amplifier.
In addition, as described in Patent Document 1, the low-pass filter is generally an LC type first-order low-pass filter composed of a coil (inductor) and a capacitor (capacitor), but in order to sufficiently remove noise. A secondary filter or a higher-order low-pass filter may be used. The low-pass filter has a function of integrating the PWM signal and converting it to an analog signal. In a class D amplifier, if a low-pass filter is not provided on the output side, a large noise is generated, which greatly affects not only the circuit but also surrounding electrical products and electronic devices.

A speaker that receives sound amplified by an amplifier and generates sound includes, for example, an electromagnet, a voice coil through which the current amplified by the amplifier flows in the magnetic field of the electromagnet, and a current in the magnetic field. It includes a diaphragm (cone) that generates sound by being vibrated by a voice coil that moves in a magnetic field by being passed, and a frame for supporting these.
Here, such a speaker unit is referred to as a speaker unit, and one or more speakers are included in a housing such as an enclosure (including not only a speaker-dedicated housing but also those integrated with various players, radios, televisions, etc.). A unit to which the unit is attached is called a speaker system.

  For example, in a general speaker system, a one-way speaker system using a full-range speaker unit in an enclosure, a two-way speaker system in which two speaker units such as a woofer and a tweeter are arranged in the enclosure, a woofer, a squawker, and a tweeter in the enclosure A three-way speaker system in which three speaker units are arranged is known.

  For example, in a general three-way speaker system, when an analog amplifier is used, for example, a PCM signal read by a CD player is converted into an analog signal by a digital analog converter provided in the CD player, and an analog amplifier is used to convert the analog signal. Amplifies the signal and outputs the amplified analog signal to the speaker system.

  In a speaker system, the amplified analog signal is divided into a high range, a mid range, and a low range by a crossover network (passive network), which will be described later. For example, a high range analog signal is input to a tweeter, An analog signal is input to the squawker and a low-frequency analog signal is input to the woofer.

  The above-mentioned crossover network is a circuit for dividing a sound range composed only of passive elements (for example, capacitors (capacitors), inductors (coils), resistors, etc.), and may be simply called a network.

  The network consists of a channel divider that divides analog signals into each sound range corresponding to each speaker unit using an inductor and a low pass filter consisting of a capacitor, a high pass filter, a band pass filter, etc. And an attenuator using a resistor for adjusting the balance.

  Further, in recent high-end audio systems, for example, after converting a digital signal output from a CD player into an analog signal and before amplifying the analog signal, the above-mentioned high-frequency analog signal and mid-range are amplified by a channel divider. The analog signal is divided into the analog signal of the low frequency range, each analog signal is amplified by a separate amplifier, and the signal amplified from each amplifier to each speaker unit described above is output one-to-one. . As a relatively inexpensive speaker system, an active speaker having an amplifier built in the speaker system is known.

  In addition, as shown in FIG. 4, a digital signal processor (DSP) 1 may be used to divide each sound range as a digital signal, and each speaker unit 6 has a class D amplifier 2 as an amplifier as described above. When provided, the digital signal can be input to the class D amplifier 2 as it is without being converted into an analog signal. Also in this case, a configuration in which a low-pass filter 3 including an inductor 4 and a capacitor 5 is arranged in a portion of the class D amplifier 2 that outputs an amplified rectangular wave, and an output from the low-pass filter 3 is input to the speaker unit 6. It is necessary to remove noise.

JP 2009-111893 A

  By the way, in the reproduction of digital sound data, in order to suppress the deterioration of the sound as much as possible, the sound stored in the storage medium as the digital data (including the sound streamed by the digital signal and the sound digitally output from the microphone) is connected to the speaker. In the case of reproduction with a digital signal, it is conceivable to transmit the signal as it is without converting it from analog to a speaker system (speaker unit) via a digital amplifier from a sound data reading device such as a CD player. When a class D amplifier is used, for example, if the CD player has an analog output, the CD player performs digital / analog (DA) conversion, and the DSP or class D amplifier performs AD conversion. Sound deteriorates.

  For example, by connecting a speaker system or speaker unit to the output side of a class D amplifier that amplifies the signal as it is, the sound can be reproduced from the speaker unit without converting the digital signal into an analog signal as described above. Is possible.

  In this case, if a low-pass filter that removes the above-described noise due to the rectangular wave output from the class D amplifier is not used, there is a risk that other devices will be greatly affected by the noise. However, when the harmonics are cut by the low-pass filter, there is a possibility of affecting the sound signal in the audible range. That is, there is a possibility that the sound is deteriorated, and even if the digital sound reproduction is fully digitized as described above, the influence of the low-pass filter is inevitable.

  In designing a multi-way speaker system, a worker who is skilled in the above-described network design and a long development period are required, which causes an increase in the cost of the speaker system.

The present invention has been made in view of the above circumstances, and suppresses the generation of noise even in a structure in which a voice coil of a speaker is connected to the output side of a digital amplifier without a low-pass filter to output sound. An object of the present invention is to provide a speaker system capable of performing

The speaker unit of the present invention is a speaker unit having a voice coil,
A digital amplifier that amplifies an input sound signal is directly connected to the voice coil, and the voice coil connection terminal of the digital amplifier circuit and a winding start point or winding end of the winding of the voice coil The length of the wiring connecting these points is 20 cm or less.

  According to such a configuration, the wiring between the voice coil and the digital amplifier is 20 cm or less and is sufficiently short, so that electromagnetic radiation of noise related to the above harmonics from the wiring can be suppressed.

  If the wiring through which the above-mentioned amplified rectangular wave flows becomes long to some extent, the wiring functions as an antenna and noise due to harmonics is radiated, but the noise is radiated because the wiring is short and the function as an antenna is low. Can be reduced.

Moreover, since the voice coil is in a state of vibrating with respect to the digital amplifier, the wiring needs to have a length that allows the voice coil to vibrate. The minimum length of the wiring described above is determined by the vibration width of the voice coil, and is mainly determined by the size of the speaker unit.
Basically, when the rectangular wave is input to the voice coil, the noise is removed in substantially the same manner as when the rectangular wave is input to the low-pass filter having the coil. Therefore, the wiring whose distance is to be regulated is the wiring from the winding start point or winding end point of the voice coil to the terminal of the digital amplifier circuit.

The digital amplifier is, for example, integrated and chipped, and the voice coil terminal is a terminal of a chip constituting the digital amplifier.
Basically, in the conventional digital amplifier, it is preferable that the above-mentioned wiring distance is set to be about the wiring distance from the terminal that outputs the amplified rectangular wave to the inductor and / or capacitor of the low-pass filter. The digital amplifier is, for example, a class D amplifier using PWM.

According to such a speaker unit, by inputting a digital sound signal to each speaker unit, it is possible to generate sound by driving the speaker directly by the output of the digital amplifier. It is possible to amplify the analog signal after digitizing it with a digital amplifier, but it is preferable to input a digital sound signal to the digital amplifier.
There is a possibility that sound quality can be improved by digitizing from reading of a digital signal from a storage medium to output to a speaker and using no low-pass filter.

In the configuration of the present invention, in addition to the voice coil, a magnet in which the voice coil is disposed in a magnetic field, a vibrating body connected to the voice coil to vibrate, the magnet, and the voice A coil and a support that supports the vibrating body so as to vibrate,
It is preferable that the digital amplifier is provided on the support.

  According to such a configuration, the distance between the voice coil and the digital amplifier is shortened, and the wiring can be shortened. As a result, the generation of noise can be suppressed by setting the length of the wiring within the above-mentioned range. In addition, an amplifier is arranged in each speaker unit as in the conventional high-end audio system, and the setting of the amplifier can be changed in each speaker unit. Also, instead of the speaker system, the speaker unit becomes an active speaker.

  Further, in the war record configuration of the present invention, the digital amplifier includes frequency range restricting means for restricting a frequency range of an input sound signal, and the digital amplifier amplifies the sound signal in a predetermined frequency range to thereby generate the voice coil. Is preferably output.

According to such a configuration, when a speaker unit is used as a multi-way speaker system, if a sound signal is input to the speaker unit, a signal in a frequency range corresponding to the sound range of each speaker is used in each speaker unit. Will be. Therefore, a speaker system can be constructed by combining speaker units having different sound ranges, and the manufacturing cost of the multi-way speaker system can be reduced.
However, in order to digitally transmit a sound signal from a recording medium reading device (or a streamed digital sound signal or a digital sound signal output from a microphone) to a speaker, the frequency range regulating means is a low-pass filter or the like. It is preferable to use a network that regulates the frequency range without changing the network.

  In the configuration of the present invention, the frequency range restricting means is a digital signal processor (DSP) that restricts a frequency range of a sound signal input to the digital amplifier and corrects a frequency characteristic of the output sound. Is preferred.

  According to such a configuration, it is possible to correct not only the sound frequency range of the DSP but also the frequency characteristics of the speaker unit in that frequency range. Therefore, when a multi-way speaker system is assembled with a plurality of speaker units, for example, it is designed by setting the DSP of each speaker unit so that the designed frequency characteristics are obtained while measuring the output sound. Sounds close to frequency characteristics can be set.

Therefore, even if the same speaker unit has different frequency characteristics due to individual differences, each speaker unit can have the same frequency characteristics, preventing the yield from deteriorating due to the individual differences of the speaker units during mass production. it can.
In addition, the same speaker unit can be used for different speaker systems by changing its frequency characteristics. For example, an excellent speaker unit can be used in many speaker systems, and the cost can be reduced. .

  The speaker system of the present invention includes the speaker unit configured as described above and an enclosure that supports the speaker unit.

  According to such a configuration, it is possible to obtain the same effects as the above-described speaker units.

  The speaker system of the present invention includes a plurality of speaker units including the above-described DSP and an enclosure that supports the speaker unit, and the frequency range and frequency of sound output for each speaker unit according to the setting of the digital signal processor. It is characterized by determining the characteristics.

  According to such a speaker system, it is not necessary to set a network at the time of designing. Instead of designing a network after designing a hardware configuration such as an enclosure or each speaker unit, for example, frequency characteristics of the speaker system. Etc., and setting (programming) the DSP of each speaker unit while measuring the sound, the speaker system can be put in a state of outputting the set sound.

  Therefore, it does not take a long time to design the network, and the cost of the speaker system can be reduced by reducing the development cost of the speaker system. Also, by enabling users of the speaker system to change DSP settings and adding settings, it is possible to output sound with frequency characteristics that match the user's preference and usage environment, and to set the sound field It is also possible to do.

  According to the present invention, without arranging a filter such as a low-pass filter between the digital amplifier as the class D amplifier and the voice coil of the speaker unit, even if the digital amplifier is directly connected to the voice coil to generate sound, Generation of noise based on the rectangular wave can be suppressed, and the sound of the digital signal that has not been filtered by the low-pass filter can be reproduced by the speaker unit.

It is a block diagram which shows the outline of the speaker unit of embodiment of this invention. It is a schematic sectional drawing which shows the said speaker unit. It is the schematic which shows the speaker system provided with two or more said speaker units. It is a block diagram which shows the outline of an example of the conventional common audio system. It is a graph which shows the change of the electric field strength of noise at the time of changing the distance of the wiring for connection to the low-pass filter instead of a voice coil in experiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The speaker unit 12 of this embodiment includes a DSP (frequency regulating means) 13 and a class D amplifier (digital amplifier) 14 in a speaker unit main body 11 as schematically shown in FIG. However, the conventional low-pass filter is not provided on the output side of the class D amplifier 14, and the wiring from the output terminal of the class D amplifier 14 is directly connected to a voice coil 24 (shown in FIG. 2) of the speaker unit body 11 described later. ing.

  As shown in FIG. 2, the speaker unit main body 11 is a general speaker unit. For example, a magnet (magnet) 21, a top plate 22 and a back plate 23 as a yoke, a voice coil 24, and a center cap 25. A cone (vibrating body) 26, a damper 27, and a frame (supporting body) 28.

  In the speaker unit main body 11 of this embodiment, a cylindrical top plate 22 is arranged in front of the cylindrical magnet 21 (in the direction of sound generation), and the magnet 21 and the top plate 22 are arranged coaxially. In addition, a columnar center pole (pole piece) 30 provided in the back plate 23 is in a state of penetrating the cylindrical magnet 21 and the cylindrical top plate 22. In the back plate 23, the above-described center pole 30 extends forward from the center of a disk-shaped main body disposed after the magnet 21. The magnet 21, the top plate 22, and the back plate 23 are fixedly supported by the frame 28.

  The voice coil 24 is a winding in which a conducting wire is wound in a cylindrical shape, and is disposed outside the center pole 30 inside the cylindrical top plate 22. That is, the voice coil 24 is inserted into the top plate 22 and the center pole 30 is inserted into the voice coil 24. A magnetic field suitable for the position where the voice coil 24 is disposed is formed by the magnetic flux of the magnet 21 being guided by the top plate 22 and the back plate 23 as a yoke.

The voice coil 24 is supported by a damper 27 connected to the frame 28 at the above-described arrangement position. The voice coil 24 supported by the damper 27 vibrates in the axial direction of, for example, the magnet 21, the top plate 22, and the back plate 23 when a current that is a sound signal is input.
The cone 26 is a vibrating body and is connected to the voice coil 24 to vibrate and generate sound by vibrating the air. The cone 26 formed in a substantially conical cylindrical shape is supported on the frame 28 by an edge (not shown) on the outer peripheral edge side.

  In this embodiment, conductive wires (wirings) 32 and 33 are provided continuously at the winding start point and winding end point of the voice coil 24, and these conductive wires 32 and 33 are connected to the speaker unit. Rather than being led to the outside, one lead wire 33 is connected to a terminal 34 provided on the frame 28. The other conducting wire 32 is connected to the frame as a ground.

An amplifier module 41 is provided in the vicinity of the terminal 34 of the frame 28. The amplifier module 41 includes, for example, a class D amplifier (digital amplifier) 14 shown in FIG.
Is provided. The amplifier module 41 includes, for example, an integrated circuit of the class D amplifier 14 and an integrated circuit of the DSP 13 on a printed wiring board. The class D amplifier 14 and the DSP 13 may be a single integrated circuit.

  The output terminal 42 of the amplified sound signal of the integrated circuit of the class D amplifier 14 (integrated circuit combining the DSP 13 and the class D amplifier 14) and the terminal 34 to which the conducting wire 33 provided in the frame 28 is connected by wiring. It is connected. The output terminal 42 and the conductive wire 33 may be directly connected.

  For example, a digital sound signal obtained by amplifying a PWM signal is output from the output terminal 42 of the amplifier module 41 (class D amplifier 14) as a rectangular wave sound signal. Noise based on the higher harmonics is electromagnetically radiated. In this case, when the conducting wire 33 functions as an antenna, noise is electromagnetically radiated. In order to reduce the electromagnetic radiation of noise, it is necessary to shorten the conducting wire 33 and the like.

  That is, the distance from the output terminal 42 to the winding start point or winding end point of the winding of the voice coil 24 through the terminal 34 and the conductive wire 33 of the voice coil 24 provided on the frame 28 needs to be as short as possible. . Here, the length of the wiring (including the conductor 33) from the output terminal 42 of the amplifier module 41 to the winding start point or winding end point of the winding of the voice coil 24 is set to 20 cm or less. In this way, noise can be reduced, and the speaker unit main body 11 can be driven without using a low-pass filter.

  The length of the wiring (including the conductor 33) from the output terminal 42 of the amplifier module 41 to the winding start point or winding end point of the winding of the voice coil 24 is 20 cm or less as described above. In order to further reduce the above, it may be 15 cm or less, or may be 10 cm or less.

The conducting wire 33 needs to have a length that does not hinder the vibration of the voice coil 24, and this length is determined by, for example, the size of the speaker unit, the frequency band (sound range) of the generated sound, and the like. That is, it differs depending on the model of the speaker unit.
Further, the length of the wiring is preferably as short as possible in order to reduce noise. For example, the minimum length of the wiring based on the vibration width of the voice coil 24 or a length slightly longer than the length is preferable. It may be good.
Further, in the conventional class D amplifier, a low pass filter is provided on the output terminal side in order to suppress noise. For example, a conventional class D amplifier equivalent to the class D amplifier used in this embodiment is used. In the amplifier, the length of the wiring (printed wiring) on the board from the terminal of the chip as the class D amplifier to the low-pass filter, and the class D up terminal and the voice coil 24 are connected by the wiring of substantially the same length. Also good.

  The amplifier module 41 is provided with a power supply (Vcc) terminal 43, a data terminal 44, and a GND (ground) terminal 45. Basically, a sound signal is inputted from the data terminal 44 and electric power inputted from the power supply terminal 43. The digital signal amplified by the above and inputted to the voice coil 24 as described above is input. The input to the amplifier module 41 is preferably a digital signal, but an AD converter may be provided in the amplifier module 41 to convert the input analog signal to digital.

  A digital signal stored in a CD or other storage medium is preferably input to the amplifier module 41 as it is. Note that not only a digital sound signal read from a storage medium but also a sound signal captured by a microphone may be digitized and input to the amplifier module 41.

  In the class D amplifier 14, a PWM signal is used as a digital signal. When the digital signal input to the amplifier module 41 is, for example, PCM, the amplifier module 41 needs to convert it into a PWM signal. In recent years, DSD signals are increasingly used as digital signals for music. The DSD signal is a method used in SACD (Super Audio CD), but is also used in recording and the like.

  The DSD signal is a rectangular wave signal similar to the PWM signal, and uses PDM (Pulse Density Modulation). The DSD (PDM) signal may be amplified by the class D amplifier 14 like the PWM signal, and this DSD signal may be input to the amplifier module 41.

The amplifier module 41 includes not only the class D amplifier 14 but also the DSP 13. The amplifier module 41 limits the frequency range (sound range) of the sound signal input to the speaker unit main body 11, and the frequency range is divided into a plurality of bands. At the same time, the gain is attenuated or amplified in each band. That is, the DSP 13 can function as a low-pass filter, a high-pass filter, a band-pass filter, or the like, and limits the frequency range of the sound signal input to the class D amplifier 14. Further, the frequency characteristics of the speaker unit main body 11 can be adjusted by equalizing. Furthermore, it is possible to set a sound field or the like.
In other words, by having the DSP 13, it is possible to perform functions of a conventional network and various filters and to correct frequency characteristics by equalizing.

  Note that the DSP 13 can easily change the above-described functions by changing the program and program data, and the frequency characteristics and the like can be changed in accordance with the characteristics of the speaker unit main body 11. . Note that the Data terminal 44 of the amplifier module 41 can change the program of the DSP 13 and the data for the program not only by inputting a sound signal but also by inputting a command.

Here, an input device for the DSP 13 can be connected to the Data terminal 44 of the amplifier module 41, and various settings can be changed or new functions can be added by a program.
That is, in the speaker unit 12, not only can the class D amplifier 14 be connected to the voice coil 24 without passing through a low-pass filter, but also a DSP 13 is provided to provide an intelligent speaker unit that can be programmed.

  Note that a wireless LAN or Bluetooth (registered trademark) device may be connected to the Data terminal 44 of the amplifier module 41 in the speaker unit 12 to input sound signals, various commands, programs, data, and the like wirelessly. In this case, a dedicated application (application) for a smartphone, a tablet, or the like may be created so that the smartphone or tablet can be used as the above-described input device.

  According to such a speaker unit 12, since the distance of the conducting wire (wiring) connecting the class D amplifier 14 and the voice coil 24 is short, noise based on harmonics of a rectangular wave electromagnetically radiated using the conducting wire as an antenna is reduced. be able to. Therefore, the speaker unit 12 can be driven with a digital signal without disposing a low-pass filter that converts the PWM signal into an analog signal between the class D amplifier 14 and the voice coil 24.

  In this case, for example, the digital signal from the device that outputs a digital sound signal, such as a CD player, to the input to the class D amplifier 14 is input, so that the digital signal is input to the speaker from the class D amplifier. The sound signal is not converted to analog until the end, and real full digital in which the digital sound signal is handled in the entire audio system can be realized.

As shown in FIG. 3, in the speaker system including the speaker unit 12 of this embodiment, the three speaker units 12 are attached to the enclosure 51 to form a multi-way (three-way) speaker system.
For example, the speaker system includes a high-frequency range speaker unit 12a (12), a mid-range range speaker unit 12b (12), and a low-range range speaker unit 12c (12).

  Conventionally, in such a speaker system, a frequency range of sound output from each speaker is set by a network including various analog filter circuits and the like. In contrast, in this speaker system, since each speaker unit 12 has the DSP 13 and the class D amplifier 14 as described above, for example, the frequency range of the digital sound signal is limited before amplification by the class D amplifier 14. It is possible to adjust the frequency characteristics of the speaker unit 12 by attenuating or amplifying the gain in each band of this frequency range.

  In this case, for example, it is possible to perform sound by actually producing sound from each of the speaker units 12a to 12c of the speaker system and changing the setting automatically. Compared to designing a network composed of analog circuits, the development time of the speaker system can be greatly reduced.

  Further, in the speaker system, the frequency characteristics and frequency range of each speaker unit 12 can be changed. For example, in a speaker system that is the same product, the characteristics of the speaker unit 12 that is used may vary depending on individual differences. Even if it differs depending on the system, the characteristics of different speaker units 12 are corrected by the DSP 13 so that they do not differ from other speaker systems, but can be shipped as products, improving yield. Can be planned.

  Further, even if there is a specification change in the enclosure 51 or each speaker unit 12 or the product itself may be changed due to a change in the supplier, the characteristics of each speaker unit 12 can be changed by the DSP 13. Therefore, it is possible to set so that a similar sound can be produced. Further, even when the individual differences between the speaker units 12 and the enclosures 51 are large as described above, it is possible to easily perform correction so that the frequency characteristics of the speaker systems are substantially the same.

In the above-described network design, the same network is used in the speaker system that is basically the same product, and it is difficult to individually adjust the sound. However, according to the speaker system of this embodiment, the speaker It is possible to adjust the sound of each speaker unit 12 individually in the system.
Further, after the speaker system is shipped, the setting of the DSP 13 such as the above-described frequency range and frequency characteristics may be changed by the user. For example, a DSP 13 input device may be provided in the speaker system. Further, an input device for adjusting the volume by the class D amplifier 14 is required.

  In the above-described embodiment, the DSP 14 is provided in each speaker unit 12. However, for example, the DSP 13 may be provided in a speaker system or other equipment, or the DSP 13 may be provided as a single device. . However, by providing the DSP 13 together with the class D amplifier 14 in the speaker unit 12, it becomes possible to provide the intelligent speaker unit 12 as described above. By changing the setting of each speaker unit 12 individually, a speaker system can be obtained. Detailed adjustment is possible.

  In any case, each speaker unit 12 is provided with a class D amplifier 14 similarly to the configuration in which an amplifier is connected to each speaker unit in a high-end audio system, and controls the speaker unit 12 in the same manner as in a high-end audio system. It becomes possible.

  Further, the number of speaker units 12 mounted in the speaker system is not limited to three, but may be one, two, or four or more. In this case, there may be two or more speaker units 12 for the same sound range.

Examples are described below.
The following experiment was conducted as an example.
In this experiment, the change in the electric field strength of noise caused by extending the distance of the wiring connecting the terminal of the class D amplifier 14 and the low-pass filter having a coil for removing noise was examined. Here, as described above, the voice coil 24 has an effect of suppressing noise similarly to the coil of the low-pass filter. When the low-pass filter in this experiment is replaced with the voice coil, There is a high possibility that an approximate result will be obtained, and at least the change in the electric field strength of noise due to an increase in the distance of the wiring tends to be the same in the low-pass filter and the voice coil 24.

  Therefore, in this experiment, a low-pass filter is used instead of the voice coil 24, and the distance of the wiring connecting the output terminal of the class D amplifier 14 and the low-pass filter is set to the original length of the product and the extended length. In this case, the electric field strength of noise was measured.

Specific experimental conditions are described below.
a, Class D Amplifier: Tripath 20W Class D Amplifier TA2020
b. Field strength measuring instrument: Akizuki Denshi's field strength meter kit assembly

  This class D amplifier 14 is a class D amplifier with analog input and analog output, and a low-pass filter circuit is mounted on the output terminal side of the printed circuit board, and the distance of wiring connected to this low-pass filter on the printed circuit board Is about 2 cm.

  The class D amplifier 14 is provided with a positive output terminal and a negative output terminal for the left channel and the right channel for stereo, respectively, and a low-pass filter is arranged for each. In the experiment, only the negative terminal side of one channel among the low-pass filters of a total of four circuits provided for the positive and negative terminals of the left and right channels of the class D amplifier 14, that is, only the low-pass filter of one circuit. The experiment was conducted using. In the experiment, the class D amplifier 14 was turned on and an analog music signal was input to the input terminal of one of the channels.

In addition, an electric field strength meter was arranged at a position about 30 cm away from the class D amplifier 14 to measure the electric field strength.
The measurement results are described below.

(1) Measurement of environmental electric field As a result of measuring the electric field strength with the class D amplifier 14 turned off, the electric field strength was 22 dBμV.

(2) Measurement in the original state of class D amplifier (reference example)
Using the wiring connection of the minus terminal of one channel of the low-pass filter circuit of the printed circuit board of the class D amplifier, with the wiring distance on the printed circuit being 2 cm as described above, the class D amplifier is turned on and the output is 1 W. As a result of measuring the electric field strength in the state where music was reproduced, the electric field strength was 24 dBμV.

(3) Measurement when the low-pass filter wiring is extended to 10 cm (Example)
The wiring to the low-pass filter circuit on the printed circuit board was cut off, the wiring connecting the low-pass filter circuit was extended using a 10 cm conductor, and the music was reproduced and the electric field strength was measured as in (2). As a result, the electric field strength was 24 dBμV.
(4) Measurement when the wiring of the low-pass filter is extended to 20 cm (Example)
The wiring to the low-pass filter circuit on the printed circuit board was cut off, the wiring connecting the low-pass filter circuit was extended using a 20 cm conductor, and the electric field strength was measured by playing music in the same manner as in (2). As a result, the electric field strength was 25 dBμV.

(5) Measurement when the wiring of the low-pass filter is extended to 35 cm The wiring to the low-pass filter circuit on the printed circuit board is cut off, and the wiring for connecting the low-pass filter circuit is extended using a 35 cm conductor (2) As in the case of, music was reproduced and the electric field strength was measured. As a result, the electric field strength was 28 dBμV.
(6) Measurement when the wiring of the low-pass filter is extended to 50 cm The wiring to the low-pass filter circuit on the printed circuit board is cut off, and the wiring for connecting the low-pass filter circuit is extended using a 50 cm conductor (2) As in the case of, music was reproduced and the electric field strength was measured. As a result, the electric field strength was 32 dBμV.

  As an experimental result, FIG. 5 shows a graph showing the relationship between the distance (2 cm to 50 cm) of the wiring connected to the above-described low-pass filter and the electric field strength (dBμV) of noise. In the graph shown in FIG. 5, the vertical axis represents the electric field strength (dBμV) of the noise, and the horizontal axis represents the length of the wiring between the terminal of the chip as a class D amplifier and the terminal of the low-pass filter (inductor or capacitor). (Cm).

  From the above results, it was confirmed that by extending the wiring to 50 cm, leakage radio wave (noise) of at least 8 dBμV was increased. However, with the extension of 10 cm, the original printed circuit board (commercially available analog) that did not extend the wiring The value was the same as that of the output class D amplifier 14), and the increase in electric field strength due to the extension of the wiring was less than the reading accuracy of the measuring instrument.

  Here, the leaked radio wave also increases / decreases according to the volume (output) by the class D amplifier 14, and is used simultaneously by making it mono to stereo or making a multi-way speaker system for a one-way speaker system. When the number of speaker units is increased and the class D amplifiers 14 are connected to the respective speaker units, the number of class D amplifiers 14 (wirings used as antennas of leaked radio waves that cause noise) increases. In consideration of this, the total amount of increase in leaked radio waves is further expanded.

Therefore, under such experimental conditions, it is desired that the amount of increase in leaked radio waves be smaller than 8 dBμV, and the length of the wiring connecting the class D amplifier 14 and the voice coil 24 needs to be shorter than 50 cm. In addition, when the wiring length is 10 cm, the noise level is the same as that of a commercially available analog output class D amplifier 14 using a low-pass filter. Therefore, even if the wiring length is longer than 10 cm, a commercially available analog output is possible. It is possible to make the noise level substantially equal to that of the class D amplifier 14.
From the above, the length of the wiring is preferably 20 cm or less, more preferably 15 cm or less, and further preferably 10 cm or less.

11 Speaker unit body 12 Speaker unit 13 DSP (frequency regulating means: digital signal processor)
14 Class D amplifier (digital amplifier)
21 Magnet
24 Voice coil 26 Cone (vibrating body)
28 Frame (support)
33 Conductor (part of wiring)

Claims (2)

Have a voice coil, together with a digital amplifier for amplifying a sound signal to be input is directly connected to the voice coil, the winding of the the terminal for the voice coil connection, winding of the voice coil of the circuit of the digital amplifier A plurality of speaker units having a wiring length connecting the start point or the end point of winding of 20 cm or less and an enclosure for supporting the speaker unit,
The digital amplifier includes frequency range regulation means for regulating a frequency range of an input sound signal, and the digital amplifier amplifies a sound signal in a predetermined frequency range and outputs the amplified sound signal to the voice coil.
The frequency range regulating means is a digital signal processor that regulates a frequency characteristic of a sound that is output while regulating a frequency range of a sound signal that is input to the digital amplifier,
A speaker system, wherein a frequency range and a frequency characteristic of sound output for each speaker unit are determined by setting of the digital signal processor. The speaker unit supports, in addition to the voice coil, a magnet in which the voice coil is disposed in a magnetic field, a vibrating body connected to the voice coil, and the magnet. A support that supports the vibrating body so as to vibrate;
The speaker system according to claim 1, wherein the digital amplifier is provided on the support.

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