WO2023167113A1

WO2023167113A1 - Speaker device and sound system

Info

Publication number: WO2023167113A1
Application number: PCT/JP2023/006883
Authority: WO
Inventors: 弘須賀田
Original assignee: フォスター電機株式会社
Priority date: 2022-03-03
Filing date: 2023-02-24
Publication date: 2023-09-07
Also published as: JP2023128448A

Abstract

This speaker device includes: at least one driver including a diaphragm; an enclosure for accommodating the driver; and a plurality of drive circuits that each output a control signal for causing the diaphragm of the at least one driver to vibrate, on the basis of a sound source signal. Some of the drive circuits among the plurality of drive circuits are provided with a low-pass filter, and this low-pass filter is set so that a concave frequency in a frequency characteristic of a signal obtained by synthesizing the control signals outputted by the plurality of drive circuits corresponds to a peak frequency of a frequency characteristic of sound pressure outputted in accordance with the shape of the enclosure.

Description

Speaker device and sound system

The technology of the present disclosure relates to a speaker device and an acoustic system.

2. Description of the Related Art Conventionally, there has been known a loudspeaker comprising a loudspeaker, a cabinet for housing the loudspeaker, and a means for compensating for a difference in frequency sound pressure characteristics between the low frequency range and the middle and high frequency ranges due to the diffraction effect of the cabinet. (JP-A-61-41299).

A coil bobbin coupled to the diaphragm, a voice coil wound around the coil bobbin, a first terminal and a second terminal led out from both ends of the voice coil, and an intermediate terminal led out from the middle of the voice coil. and a bandpass filter connected to the second terminal, a driving current is supplied between the first terminal and the intermediate terminal, and a driving current is supplied between the second terminal and the intermediate terminal. A loudspeaker driven by current supplied through a bandpass filter is known (Japanese Laid-Open Patent Publication No. 9-163486). In this speaker, the reproduced sound pressure level is controlled by a drive current supplied between the second terminal and the intermediate terminal through the bandpass filter.

With conventional technology, there is room for improvement in terms of correcting for changes in driver output characteristics due to the diffraction effect of the baffle of the enclosure and realizing a low-cost, high-quality sound system.

In consideration of the above facts, the technology of the present disclosure aims to provide a speaker device and an acoustic system with a simple configuration and high sound quality.

One aspect of the present disclosure is a speaker device, which includes a drive unit including at least one driver including a diaphragm, an enclosure that houses the driver, and a diaphragm of the at least one driver based on a sound source signal. and a plurality of drive circuits outputting control signals for vibrating, wherein the drive section vibrates the diaphragm according to the outputs of the plurality of drive circuits, and drives some of the plurality of drive circuits. A low-pass filter is provided in the circuit, and the low-pass filter is a signal obtained by synthesizing the control signal output from each of the plurality of drive circuits with the peak frequency of the frequency characteristics of the sound pressure output according to the shape of the enclosure. is set so that the recess frequency in the frequency characteristic of is corresponding.

An aspect of the present disclosure is an acoustic system including the speaker device described above, a signal input unit that receives the sound source signal, and an amplifier that outputs the received sound source signal to the speaker device.

As described above, according to the technology of the present disclosure, it is possible to provide an acoustic system with a simple configuration and high sound quality.

1 is a schematic diagram of an acoustic system according to first, second, and third embodiments of technology of the present disclosure; FIG. 1 is a cross-sectional view showing a configuration of a speaker device according to a first embodiment of technology of the present disclosure; FIG. 1 is a circuit diagram showing an electrical configuration of a speaker device according to a first embodiment of technology of the present disclosure; FIG. 4 is a graph showing frequency characteristics of control signals output from drive circuits and combined signals; 1 is a circuit diagram showing an example of a configuration of a speaker device according to a first embodiment of technology of the present disclosure; FIG. 1 is a circuit diagram showing an example of a speaker device configured using a first-order low-pass filter; FIG. FIG. 4 is a circuit diagram when a voice coil is a pure resistance; 4 is a vector diagram representing voice coil voltages; FIG. 4 is a graph showing frequency characteristics of control signals output from drive circuits and combined signals; FIG. 3 is a circuit diagram showing an equivalent circuit of a speaker device configured using a secondary low-pass filter; 4 is a vector diagram representing voice coil voltages; FIG. 4 is a graph showing frequency characteristics of control signals output from drive circuits and combined signals; 4 is a graph showing the frequency characteristics of the control signal output from each drive circuit and the synthesized signal when ζ is varied. FIG. 4 is a circuit diagram showing an equivalent circuit of a speaker device configured using a third-order low-pass filter; 4 is a graph showing frequency characteristics of a signal obtained by synthesizing control signals output from each drive circuit when ζ is changed. FIG. 4 is a vector diagram showing voice coil voltages when first to fourth order low-pass filters are used; FIG. 4 is a circuit diagram showing an equivalent circuit of a drive circuit including a low-pass filter; FIG. 4 is a circuit diagram showing an equivalent circuit of a drive circuit including a low-pass filter; It is a graph showing the characteristic of each impedance. 5 is a graph showing frequency characteristics of a signal obtained by synthesizing control signals output from each of the drive circuits when the load is changed; 4 is a graph showing frequency characteristics of voice coil voltage; FIG. 4 is a cross-sectional view showing the configuration of a speaker device according to a second embodiment of the technique of the present disclosure; FIG. 4 is a circuit diagram showing the configuration of a speaker device according to a second embodiment of the technology of the present disclosure; FIG. 4 is a perspective view showing a single voice coil bobbin; FIG. 4 is a cross-sectional view of a two-line voice coil. FIG. 4 is a circuit diagram showing a speaker device configured without using a low-pass filter; 4 is a graph showing anechoic room characteristics in a 2π space and a bass reflex type enclosure in a speaker device configured without using a low-pass filter. 4 is a graph showing a comparison between the difference between the measured values of the bass reflex enclosure and the 2π space and the calculated data. 1 is a circuit diagram showing the configuration of a speaker device according to an example; FIG. 5 is a graph showing simulation results of frequency characteristics of a signal obtained by synthesizing control signals output from drive circuits; 7 is a graph showing sound pressure measurement results with and without a low-pass filter. 7 is a graph showing a sound pressure difference with and without a low-pass filter; 1 is a circuit diagram showing an example of the configuration of a speaker device according to an embodiment; FIG. 5 is a graph showing simulation results of frequency characteristics of a signal obtained by synthesizing control signals output from drive circuits; 7 is a graph showing sound pressure measurement results with and without a low-pass filter. 7 is a graph showing a sound pressure difference with and without a low-pass filter; It is a circuit diagram in which one voice coil is short-circuited. FIG. 25 is a graph showing sound pressure measurement results when one voice coil is short-circuited and when it is not (connection of FIG. 24). FIG. 4 is a circuit diagram of a state in which one voice coil is open; 7 is a graph showing sound pressure measurement results when one voice coil is open and when one voice coil is short-circuited; 1 is a circuit diagram showing the configuration of a speaker device in an example of use as a WF; FIG. 5 is a graph showing frequency characteristics of a control signal for each driver and a synthesized signal; 4 is a perspective view showing an example of an enclosure; FIG. 4 is a perspective view showing an example of an enclosure; FIG. 1 is a circuit diagram showing the configuration of a 2-way sound system; FIG. 5 is a graph showing frequency characteristics of a control signal for each driver and a synthesized signal; 7 is a graph showing the frequency characteristics of the control signal for each driver and the synthesized signal when considering the diffraction effect of the baffle. 1 is a circuit diagram showing a configuration of a speaker device provided with a compensation circuit; FIG. 5 is a graph showing frequency characteristics of a control signal for each driver and a synthesized signal; 4 is a graph showing filter characteristics when white noise is used as a signal source; 1 is a circuit diagram showing a configuration of a speaker device in an example of use as TW; FIG.

Hereinafter, embodiments of the technology of the present disclosure will be described in detail with reference to the drawings.

<Summary of embodiment of technology of the present disclosure>
Acoustic systems emphasizing high-quality sound reproduction require broadband, low-distortion, and flat sound pressure frequency characteristics.

In sound systems for general users, the space factor is emphasized in the enclosure, and a rectangular parallelepiped shape such as a small sound system or a tallbow type (which is expanded in all directions to increase the volume to make bass reproduction advantageous) is used. is the mainstream (see FIGS. 41A and 41B). These include those using a full-range driver that can radiate all bands with a single driver, and multi-way sound systems that divide the input signal into bass, middle, and treble by a dividing network circuit and reproduce them with dedicated drivers. There is

When the volume of the enclosure and the diameter of the driver become smaller, the problem of insufficient bass tends to occur, such as the lower limit frequency that can be reproduced becomes higher and the sound pressure in the bass band becomes insufficient. For this reason, it has been proposed to add a subwoofer sound system for reproducing the band below the reproduction lower limit frequency of the sound system. Here, the subwoofer sound system reproduces frequencies below the lower limit frequency of the main sound system with one sound system, taking advantage of the fact that the listener cannot perceive the direction in the lowest sound range.

The effect of the subwoofer is that it is possible to reinforce the area below the lower frequency limit of the main sound system. ) has no effect of correcting for the influence of the diffraction effect.

Also, in a multi-way sound system, it is possible to control characteristics such as sound pressure differences between each unit, but since the reproducible band of each unit is limited, the frequency range of the sound pressure difference due to the diffraction effect of the baffle, It may not be possible to create characteristics that match the peak frequency. For example, when the sound pressure difference portion due to the diffraction effect of the baffle is within the reproduction band of the bass driver, it cannot be corrected.

Here, the diffraction effect of the baffle will be explained. Generally, bass drivers and full-range drivers for Hi-Fi audio systems for listening to music are of the electrodynamic type for the driving part and the direct radiation type (cone type, flat plate type, etc.) for the radiating part. be.

When this type of driver is attached to an infinite baffle to separate the radiated sound before and after the diaphragm (radiating into 2π space), the characteristics of the driver axis in the mass control band (frequency band higher than the lowest resonance frequency) Since the sound pressure at the upper listening point is proportional to the input voltage, theoretically the characteristics are generally flat within that band.

However, since it is not realistic to construct an infinite baffle, it is common to use a rectangular parallelepiped enclosure that surrounds the sound radiated from the rear of the driver.

The baffle has a finite size, and sound waves are diffracted at the edge of the baffle. As a result, the radiation space substantially becomes a 4π space in the low frequency band (long wavelength band) in which the directivity is weak, so that a sound pressure drop of 6 dB occurs in the high frequency band in which the directivity is strong. That is, the low frequency side is 6 dB lower than the high frequency side. Also, a virtual sound source is produced at the end of the baffle, which causes an undulation in the characteristic on the driver axis.

In this way, for example, when a conductive driver is attached to the baffle plate of a general rectangular parallelepiped enclosure, there are two prominent characteristics of the sound pressure characteristics. First, there is a characteristic that the high frequency band is higher than the low frequency band by 6 dB. Secondly, there is a feature that a peak of about 1 to 3 dB is generated with respect to the sound pressure on the high frequency side in the middle band.

Correcting at least these two characteristics is effective in improving the lack of bass in the acoustic system, that is, in achieving flat sound pressure frequency characteristics. A conductive driver has a sound pressure characteristic proportional to a voltage, and has a flat sound pressure characteristic with an infinite baffle.

As an example of countermeasures for compensating for these, in the case of a two-way acoustic system configured using a high frequency driver (tweeter: hereinafter also referred to as "TW") and a low frequency driver (woofer: hereinafter also referred to as "WF") , and a crossover network (dividing network, hereinafter also referred to as "network").

FIG. 42 is a basic circuit diagram showing a speaker device for a two-way sound system. The HPF is a high pass filter that filters the input signal to the appropriate band signal components for the TW. The LPF is a low-pass filter that converts the input signal into signal components in the appropriate band for WF. ATT is an attenuator, and is a circuit for adjusting the magnitude of the input voltage to TW. In the example of FIG. 42, the resistors are arranged in an L-shape, and the impedance when viewed from the HPF is close to pure resistance. This makes the characteristics of the HPF less susceptible to the voice coil inductance and motional impedance of the TW.

In the impedance (Imp.) correction, the electrical impedance of the driver is composed of the motional impedance, the DC resistance of the voice coil, and the voice coil inductance of WF. The circuit of FIG. 42 can eliminate the influence of the voice coil inductance of the WF in the LPF band. That is, it can be seen as a pure resistance.

FIG. 43 shows an example of the frequency characteristics of the control signal input to each driver and the frequency characteristics of the synthesized signal, assuming that the output characteristics of each driver are flat and have the same efficiency within their respective bands. It is a graph showing. FIG. 43 shows calculated values in a circuit connected so that the TW side is in reverse phase, Ein is the input voltage from the amplifier, and Ewf is the voltage of the signal input to the WF side driver. and Etw is the voltage of the signal input to the driver on the TW side.

Also, FIG. 44 shows a graph showing an example of the frequency characteristics of the control signal input to each driver and the frequency characteristics of the combined signal when the influence of the diffraction effect of the baffles is further considered. In FIG. 44, the inductance L1 of the LPF is tripled compared to the example shown in FIG. 43, so that the output gradually decreases from a lower frequency, and the TW output is 6 dB lower than the WF output at ATT. This shows an example of correcting the diffraction effect of the baffle.

In the example shown in FIG. 44, correction is possible only by changing the constants of the elements while maintaining the typical dividing network circuit configuration of the two-way acoustic system. However, in order to create a hollow near the crossover frequency of WF and TW, TW must be sufficiently reproducible up to near the frequency at which the sound pressure peaks due to the baffle effect. In the example of FIG. 44, the TW needs to be sufficiently reproducible in a band of 1 kHz or higher.

Also, when a diaphragm with an effective diameter of 145 mm is attached to a cuboid enclosure with a baffle of about 300 x 450 mm, for example, a peak occurs at 700 Hz in sound pressure characteristics due to the baffle effect. A TW capable of sufficiently reproducing 700 Hz or higher (in the case of a two-way sound system) is required for correction by a similar method. In this way, TWs that can be used for those with high low-frequency reproduction capability are limited according to the outer dimensions of the acoustic system.

As another example, if the TW has a high reproducible lower limit frequency or the TW has a low input resistance, the crossover frequency may have to be increased in order to increase the input resistance performance of the system. In addition, there are also those in which the crossover frequency is intentionally set high in order to use a wideband WF or full-range type driver, and those in which TW is not used. In these cases, the band in which the sound pressure difference occurs due to the baffle effect is within the output band of the low-frequency driver or the full-range driver.

For example, as shown in FIG. 45, there is known a method of providing a compensation circuit for making the frequency characteristics of the signal input to the driver reverse to the baffle effect. FIG. 46 is a graph showing an example of the frequency characteristics of the input signal to each driver in the circuit of FIG. 45 and the frequency characteristics of the combined signal.

　In the method shown in the example of Fig. 42, when the baffle is large, the reproduction band of the TW widens to the low frequency side, and there is a problem that the voice coil of the TW is likely to be damaged due to heat generation and excessive amplitude. In addition, there is a problem that the input resistance of the system is lowered as a result. In addition, there is a problem that the low-frequency reproduction limit of TW must be sufficiently low, and options for TW are reduced.

In the method shown in the example of FIG. 45, the resistance in the compensation circuit generates a large amount of heat, which causes changes in characteristics and safety problems. In addition, since voice signals or music signals have low energy in high frequencies and high energy in middle and low frequencies, when resistors are used in the network, they are mainly used on the high frequency side. Further, there is a problem that the extension of the TW reproduction band to the low frequency side is disadvantageous in terms of reliability. It should be noted that the characteristics of the signal for the input resistance test of the speaker stipulated in the international standards are stipulated (see FIG. 47). FIG. 47 shows filter characteristics when white noise is used as a signal source.

The embodiment of the technology of the present disclosure solves the above problem and provides an inexpensive high-quality sound system.

Here, as the main features of the diffraction effect of the baffle of the enclosure such as a rectangular parallelepiped, there is a sound pressure difference of 6 dB between the low range and the high range, and the sound pressure rise part (approximately 2 dB peak).

The input signal to the normal driver is corrected to have the opposite characteristics of the above characteristics and is input to the driver. No resistance is used.

Specifically, a driver (WF or full-range type driver) that emits a band that produces a sound pressure difference due to the baffle effect is used as a component to correct the 6 dB sound pressure difference between the low and high frequencies. , the drive circuits of two or more systems are electrically driven, and the drive circuits of some systems are provided with low-pass filters and connected in parallel with the drive circuits of the other systems.

As a result, the low-frequency driver output is made larger than the high-frequency driver output, and the sound pressure difference between the low-frequency side and the high-frequency side due to the finite baffle is corrected.

As a configuration in which two or more drive circuits are electrically driven, each drive circuit applies force in the same direction to an input signal by any of the following first to third methods. It may be configured to generate

In the first method, a plurality of drive circuits for a plurality of drivers are connected in parallel and used.

In the second method, a plurality of drive circuits are provided for a single driver (diaphragm) and connected in parallel. Specifically, a plurality of sets of magnetic gaps and voice coils are provided in a single driver.

In the third method, multiple lines of voice coil wires are arranged for a single magnetic gap and a single voice coil in a single driver.

When using even-numbered drive circuits with the same performance, half of the drive circuits may be provided with low-pass filters, and the other drive circuits may be driven by inputting signals to the drivers without providing low-pass filters. This makes the high frequency side lower than the low frequency side by 6 dB. That is, the driving force becomes 1/2.

As a component for correcting the fact that there is a sound pressure rise portion (approximately 2 dB peak) on the high-frequency side of the sound pressure step, a low-pass filter is added to the input-side inductance (coil) connected in series with the voice coil and the voice coil. It shall be of a second order or higher consisting of a capacitance (capacitor) connected in parallel with the coil. Also, in the frequency characteristics of the signal input to the driver, a depression is formed near the peak frequency caused by the baffle effect.

[First embodiment]
<Configuration of Acoustic System According to First Embodiment of Technology of the Present Disclosure>
FIG. 1 shows a schematic diagram of an audio system 10 according to an embodiment of the technology of the present disclosure.

As shown in FIG. 1, the acoustic system 10 includes a sound source input section 12, an amplifier 14, and a speaker device 16.

The sound source input unit 12 receives sound source signals.

The amplifier 14 outputs the received sound source signal to the speaker device 16 .

The speaker device 16 includes, as shown in FIG. 2, a drive section 18 consisting of two drivers 20A and 20B, and an enclosure 22 that houses the drive section 18. As shown in FIG. In this embodiment, the enclosure 22 is a rectangular parallelepiped housing and is a bass reflex type enclosure. Drivers 20A and 20B are full-range drivers.

As shown in FIG. 3, the speaker device 16 includes a drive circuit 30A that outputs a control signal for vibrating a diaphragm (not shown) of the driver 20A based on the sound source signal, and a driver 20B that vibrates the driver 20B based on the sound source signal. It includes a drive circuit 30B that outputs a control signal for vibrating a plate (not shown), and a drive unit 18 that vibrates the diaphragm according to the outputs of the drive circuits 30A and 30B. The drive circuit 30B has a low-pass filter 32 .

The drivers 20A, 20B include voice coils VC1, VC2 and magnetic circuits (not shown).

The drive circuit 30A outputs a control signal corresponding to the input sound source signal to the voice coil VC1, and causes the diaphragm of the driver 20A to vibrate with the magnetic circuit.

The drive circuit 30B outputs a control signal obtained from the input sound source signal through the low-pass filter 32 to the voice coil VC2, and vibrates the diaphragm of the driver 20B by the magnetic circuit.

In the low-pass filter 32, the peak frequency of the frequency characteristics of the sound pressure output according to the shape of the enclosure 22 corresponds to the depression frequency in the frequency characteristics of the signal obtained by synthesizing the control signals output from the drive circuits 30A and 30B. (see arrows in FIG. 4). In FIG. 4, Ein indicates the voltage of the input signal from the amplifier 14, Evc1 indicates the voltage of the control signal input to the voice coil VC1, and Evc2 indicates the voltage of the control signal input to the voice coil VC2. showing. A dip frequency is a frequency that is a minimum value in the frequency characteristics of a signal.

The low-pass filter 32 is of secondary or higher order and consists of an inductance (coil) connected in series with the voice coil VC2 and a capacitance (capacitor) connected in parallel with the voice coil VC2.

For example, as shown in FIG. 5, the low-pass filter 32 has an inductance L connected in series with the voice coil VC2 and a capacitance C connected in parallel with the voice coil VC2.

<Description on the order of the low-pass filter>
Here, the reason why the low-pass filter 32 is of second order or higher will be described.

First, the case where the low-pass filter is primary, that is, the case where the low-pass filter is composed only of coils will be described (Fig. 6). FIG. 6 is a circuit diagram showing a speaker device configured using a first-order low-pass filter.

When the voltage of the input signal is Ein=1, the electrical impedance of each voice coil is Rvc1 and Rvc2, respectively, and the voltage of the control signal output to the voice coil is Evc1 and Evc2 (see FIG. 7), the following formula expressed. FIG. 7 is a circuit diagram showing an equivalent circuit of the speaker device when the voice coil is pure resistance.

When the voltage of the control signal to each voice coil is represented by the vector diagram shown in FIG. 8, Evc1(ω) is constant at 1 regardless of the frequency, so the vector does not rotate (see the dashed arrow in FIG. 8).

In addition, in FIG. 7 above, the voice coil is a pure resistance for the sake of simplification. Strictly speaking, since the voice coil is not a pure resistance, other influences such as reactance will be described later.

Evc2(ω) moves from 1 to 0 on the dashed curve as ω(=2πf) increases from 0. Therefore, the real part of Evc2(ω) never becomes negative (the phase angle ranges from 0 to -90°).

Evc1(ω)+Evc2(ω) (see the tip of the practical arrow in FIG. 8) moves from 2, which is the real part, toward 1 on the solid curve as ω increases from 0. Therefore, the length of the combined vector (|Evc1(ω)+Evc2(ω)|) is always greater than or equal to 1 and never falls below the value of Ein. ). FIG. 9 is a graph showing the frequency characteristics of the control signal output by each drive circuit in the circuit of FIG. 7 and the combined signal.

As a condition for the length of the combined vector (|Evc1(ω)+Evc2(ω)|) to be less than 1 (a hollow is formed), at least the real part of Evc2(ω) must be negative. In other words, the phase angle of Evc2(ω) should be in a part of -90 to +90 degrees.

Next, as shown in FIG. 10, the case of using a secondary low-pass filter, that is, the case of configuring a low-pass filter using one coil and one capacitor, will be described. FIG. 10 is a circuit diagram showing an equivalent circuit of a speaker device configured using a secondary low-pass filter. Voltages Evc1 and Evc2 of the control signals output to the voice coil are expressed by the following equations.

It can be seen that the real part of Evc2(ω) is negative if (1−ω ² CL)<0, since the denominator is always positive. In other words

(See the case where the dashed curve in FIG. 11 passes through the third quadrant). FIG. 11 is a vector diagram showing the voltage of the control signal output to the voice coil in the circuit shown in FIG. 10 above.

Evc1(ω)+Evc2(ω) (see the tip of the solid arrow in FIG. 11 above) moves from 2 to 1 on the solid curve as the frequency increases from 0, and the absolute value is 1 at high frequencies. and converges to 1.

From this, it is possible to form a depression on the frequency characteristic of the voltage of the synthesized signal at a specific portion of the frequency (phase between -90° and -180°) where the real part of Evc2(ω) becomes negative. (FIG. 12). FIG. 12 is a graph showing the frequency characteristics of the control signal output by each drive circuit in the circuit shown in FIG. 10 and the combined signal.

Also, the constant of the second-order Butterworth low-pass filter is

However, by changing ζ, the shoulder characteristic of the low-pass filter can be changed.

Specifically, the characteristic change due to ζ is as follows.

Among the changes in sound pressure due to the baffle diffraction effect, the band in which the sound pressure decreases from the low frequency side to the high frequency side is generally wider than 2 oct. It is better to make the shoulder characteristic smoother than the other. However, along with this, the depression also becomes shallow (see FIG. 13). FIG. 13 is a graph showing frequency characteristics of a signal obtained by synthesizing the control signals output from the drive circuits when .zeta. is varied in the circuit shown in FIG.

In this way, it is possible to adjust f and ζ in the second-order low-pass filter so that the correction characteristic approaches the inverse characteristic of the baffle diffraction effect.

Next, as shown in FIG. 14, the case of using a third-order low-pass filter will be described. FIG. 14 is a circuit diagram showing an equivalent circuit of a speaker device configured using a third-order low-pass filter.

Each Butterworth constant is represented by the following formula.

By adjusting each ζ, it is possible to approximate the inverse characteristics of the baffle diffraction effect (see FIG. 15). The bandwidth of the sound pressure drop band, the level of the hollow band, etc. can be adjusted. FIG. 15 is a graph showing frequency characteristics of a signal obtained by synthesizing the control signals output from the drive circuits when .zeta. is varied in the circuit shown in FIG.

Next, the case of using a fourth-order or higher low-pass filter will be described.

Since the phase rotation angle of Evc2 increases as the order increases, the real part of Evc2 becomes negative in the case of 4th and higher orders, as in the case of 2nd and 3rd orders (phase is -90 to +90 degrees). exists. Thus, the formation of depressions is possible. FIG. 16 is a vector diagram showing the vector trajectory of the voltage Evc2 of the control signal output to the voice coil when each of the 1st to 4th order low-pass filters is used.

<Description on the influence of the electrical impedance of the driver>
Next, the influence of the electrical impedance of the driver as the load of the low-pass filter will be explained.

The calculation data such as the correction characteristics shown so far are calculated using the driver's electrical impedance as pure resistance. The electrical impedance of an actual driver has a specific impedance characteristic Ze mainly due to the motional impedance Zem and the reactance Zex due to the voice coil inductance.

Due to these factors, if the band where the reactance component is large with respect to pure resistance is close to the band where the low-pass filter produces a 6 dB step difference, the frequency characteristics of the control signal input to the voice coil will differ from those of pure resistance. change compared to

The motional impedance Zem is the effect of the back electromotive force generated by the motion of the voice coil within the magnetic gap, and is expressed by the following formula.

The reactance Zex due to the voice coil inductance is expressed by the following equation due to the influence of the magnetic material (magnetic circuit) acting as the voice coil winding and iron core.
Zex = jωL

where L is the inductance of the voice coil, A is the force coefficient (magnetic flux density × effective length of VC2), Mm is the vibration system mass, Sm is the stiffness, and Rm is the mechanical resistance. is.

The electrical impedance of a general dynamic speaker and its effect on the terminal voltage will be described below as the characteristics of the voice coil VC2 in FIG.

The equivalent circuit of the drive circuit on the voice coil VC2 side is as follows.

When the impedance of the voice coil is pure resistance, the impedance Ze of the voice coil is expressed by the following equation (FIG. 17).
Ze=Rvc2

FIG. 17 is a diagram showing an electric system equivalent circuit of a drive circuit including a low-pass filter when the impedance of the voice coil is pure resistance.

In addition, the electrical impedance Ze of the driver when considering the reactance Zex due to the motional impedance Zem and the voice coil inductance is expressed by the following formula (Fig. 18).

Ze=Rvc2+Zex+Zem

FIG. 18 is a diagram showing an equivalent circuit of a drive circuit including a low-pass filter when considering the motional impedance Zem and the reactance Zex due to the voice coil inductance. (1) in FIG. 18 corresponds to the motional impedance Zem, and (2) in FIG. 18 corresponds to the reactance Zex due to the voice coil inductance.

FIG. 19 shows the characteristics of the electrical impedance of the driver in the circuit shown in FIG. 18 above. FIG. 19 is a graph showing respective characteristics of |Zex|, |Zem|, |Ze|, and pure resistance Rvc2.

Also, FIG. 20 shows changes in frequency characteristics of a signal obtained by synthesizing control signals to each voice coil due to differences in load. FIG. 20 is a graph when the electrical impedance of the driver is a pure resistance and when the reactance Zex due to the motional impedance Zem and voice coil inductance is considered. This graph is a graph showing frequency characteristics of a signal obtained by synthesizing the control signals output from each of the drive circuits.

The influence of motional impedance (see (1) in FIG. 20) is shown near 200 Hz, and the influence of voice coil inductance ((2) in FIG. 20) is shown near 1.5 kHz.

For these effects, it is possible to approach the desired characteristics by conducting simulations calculated according to the specifications of the driver and confirming them through actual measurements, and adjusting the constants of the low-pass filter.

In addition, if a circuit that cancels the inductance (impedance compensation circuit described above) is provided between the low-pass filter on the voice coil VC2 side and the driver, or a short ring (that cancels the magnetic flux change that occurs with the voice coil current) is installed. When used, the inductance component in the load of the low-pass filter is reduced, so the effect of the reactance Zex due to the voice coil inductance is also reduced. Also, in general, a voice coil with a smaller number of turns, such as a full-range driver, has a smaller inductance than WF, and thus has less influence.

<Operation of Acoustic System According to Embodiment of Technology of the Present Disclosure>
A sound source input unit 12 receives input of a sound source signal from an audio player or the like.

Then, the amplifier 14 outputs the received sound source signal to the speaker device 16 .

Then, the drive circuit 30A of the speaker device 16 outputs a control signal to the driver 20A based on the sound source signal to vibrate the diaphragm (not shown) of the driver 20A.

Further, the drive circuit 30B of the speaker device 16 uses the low-pass filter 32 based on the sound source signal to output a control signal to the driver 20A to vibrate the diaphragm of the driver 20B.

Here, the low-pass filter 32 combines the peak frequency of the frequency characteristics of the sound pressure output according to the shape of the enclosure 22 with the control signal output from each of the drive circuits 30A and 30B, and the depression frequency in the frequency characteristics of the signal. are set accordingly. Therefore, in the frequency characteristics of the signal obtained by synthesizing the input signals to the drivers 20A and 20B, there is a depression near the peak frequency caused by the baffle effect of the enclosure 22. FIG. As a result, the acoustic system 10 achieves a flat sound pressure frequency characteristic.

As described above, according to the acoustic system according to the first embodiment of the technology of the present disclosure, the low-pass filter provided in one of the two drive circuits is adjusted according to the shape of the enclosure. The peak frequency of the frequency characteristics of the output sound pressure is set so that the depression frequency in the frequency characteristics of the signal obtained by synthesizing the control signals output from each of the two drive circuits corresponds. As a result, it is possible to provide a high-quality speaker device with a simple configuration.

In addition, it is possible to provide a low-cost, high-quality sound system with a simple circuit configuration by correcting the driver input so as to reverse the characteristics of the driver output due to the diffraction effect of the baffle of the enclosure. can.

In addition, since the speaker device does not use resistance and generates little heat, the characteristics during use are stable, and it is also advantageous for designing a highly durable sound system.

In addition, by adjusting the output balance and element constants of each drive circuit, it is possible to correct the driver characteristics in addition to the correction according to the characteristics of the diffraction effect of the rectangular baffle.

[Second embodiment]
Next, an acoustic system according to the second embodiment will be described. Parts having the same configuration as in the first embodiment are denoted by the same reference numerals, and descriptions thereof are omitted.

The second embodiment differs from the first embodiment in that a plurality of drive circuits are provided for a single driver and the plurality of drive circuits are connected in parallel.

As shown in FIG. 1, the acoustic system 210 includes a sound source input section 12, an amplifier 14, and a speaker device 216.

The speaker device 216, as shown in FIG. 21, includes a driving section 218 including a driver 220 and an enclosure 22 that houses the driver 220. As shown in FIG.

Further, as shown in FIG. 22, the speaker device 216 includes a drive circuit 30A, a drive circuit 30B, and a drive section 218 that vibrates the diaphragm according to the outputs of the drive circuits 30A and 30B. The drive circuit 30B has a low-pass filter 32 .

Each of drive circuit 30A and drive circuit 30B outputs a control signal for vibrating the diaphragm of single driver 220 based on the sound source signal.

The driver 220 includes multiple sets of magnetic circuits and voice coils. Specifically, the driver 220 includes a voice coil VC1 and magnetic circuit set and a voice coil VC2 and magnetic circuit set.

The drive circuit 30A vibrates the diaphragm of the single driver 220 by outputting a control signal to the voice coil VC1 based on the sound source signal. Further, the driving circuit 30B vibrates the diaphragm of the single driver 220 by outputting a control signal to the voice coil VC2 based on the sound source signal.

The rest of the configuration and operation of the acoustic system according to the second embodiment are the same as those of the first embodiment, so descriptions thereof will be omitted.

In the acoustic system according to the second embodiment, even in the case of a single driver, it is possible to correct the influence of the diffraction effect of the baffle with a simple circuit.

[Third Embodiment]
Next, an acoustic system according to the third embodiment will be described. Parts having the same configuration as those in the first and second embodiments are denoted by the same reference numerals, and descriptions thereof are omitted.

The third embodiment differs from the second embodiment in that the driver has a single magnetic circuit, a single voice coil, and multiple lines of voice coil wires. there is

Specifically, as shown in FIGS. 23A and 23B, the driver is configured using a single voice coil bobbin with two lines of conductors wound in parallel in the same direction. FIG. 23B shows a cross section of the winding portion, showing how the coil wire of the voice coil VC1 and the coil wire of the voice coil VC2 are wound in parallel around the voice coil bobbin.

The rest of the configuration and operation of the acoustic system according to the third embodiment are the same as those of the second embodiment, so descriptions thereof will be omitted.

[Example]
An example of the acoustic system described in the third embodiment will be described. In this embodiment, the voice coil used is a single voice coil bobbin with an inner diameter of Φ25 and two conductor wires wound in parallel in the same direction (DCR6.9+6.9Ω). The magnetic circuit was a ferrite magnet external magnet type, and a cone diaphragm (curved cone, cloth edge) with an effective vibration diameter Φ80 was used. A bass-reflex type enclosure having external dimensions of W214×H384×D150 was used.

Also, as a comparative example, a speaker device configured without using the low-pass filter shown in FIG. 24 was used. FIG. 25 is a graph showing anechoic room characteristics in a 2π space and a bass reflex type enclosure in a speaker device constructed without using a low-pass filter. The 2π space is an anechoic chamber that simulates the 2π space and has a baffle on one side. Also, FIG. 26 is a graph showing a comparison between the difference between the measured values of the bass reflex enclosure and the 2π space and the calculated data. Here, the difference between the measured values corresponds to the diffraction effect of the baffle.

Below 200Hz, the characteristics of the bass reflex type enclosure appear, but above 300Hz, the effect of baffle diffraction generally agrees with the calculated data obtained by simulation.

Also, FIG. 27 is a circuit diagram showing the configuration of a speaker device 216 according to an embodiment using a secondary low-pass filter. Here, it is assumed that the inductance L of the low-pass filter is 3 mH and the capacitor C is 20 μF.

FIG. 28 is a graph showing a simulation result of frequency characteristics of a signal (composite voltage) obtained by combining the control signals output from each of the drive circuits in the circuit shown in FIG.

FIG. 29 is a graph showing the sound pressure measurement results with and without the low-pass filter. FIG. 30 is a graph showing sound pressure differences with and without a low-pass filter. Note that the values in FIG. 30 are calculated from actual measurements.

Also, FIG. 31 is a circuit diagram showing the configuration of a speaker device 216 according to an embodiment using a third-order low-pass filter. Here, it is assumed that the inductance L1 of the low-pass filter is 3 mH, the capacitor C is 15 μF, and the inductance L2 is 0.5 mH.

FIG. 32 is a graph showing simulation results of frequency characteristics of a signal (composite voltage) obtained by combining the control signals output from each of the drive circuits in the circuit shown in FIG.

FIG. 33 is a graph showing the sound pressure measurement results with and without the low-pass filter. FIG. 34 is a graph showing sound pressure differences with and without a low-pass filter. Note that the values in FIG. 34 are calculated from actual measurements.

Next, we will explain the influence of electromagnetic coupling on the voice coil. In this embodiment, two voice coils are positioned at the same portion in the coaxial vibration direction. Therefore, the two voice coils are in a coupling relationship that shares the magnetic flux generated by the current, and an electromotive force is generated in each voice coil according to the current change in the other voice coil. As a result, the current generated in the other voice coil becomes a current in the opposite direction to the input voltage to each voice coil, and the higher the frequency, the greater the change in magnetic flux with respect to time, the greater the current. These currents have the effect of reducing the driving force generated by each input, which is more pronounced at higher frequencies. Note that the effect of this phenomenon is reduced when the aforementioned short ring is provided.

In addition, when there is no low-pass filter (Fig. 24 above), the circuit of each voice coil system is the same as when the other voice coil is short-circuited (Fig. 35) (normally, the output impedance of the amplifier is sufficiently higher than the voice coil impedance). It can be said that the characteristic when both terminals are input when no low-pass filter is used is the characteristic (+6 dB) obtained by combining two characteristics (see the solid line in FIG. 36) in this case (see the broken line in FIG. 36). . FIG. 35 is a circuit diagram in which one voice coil is short-circuited. FIG. 36 is a graph showing the results of sound pressure measurement when one voice coil is short-circuited (FIG. 35) and when it is not short-circuited (FIG. 24).

Also, FIG. 37 shows a circuit diagram in which the voice coil VC2 side is open. FIG. 38 shows the sound pressure measurement result in the circuit shown in FIG. 35 (when one voice coil is short-circuited) and the sound pressure measurement result in the circuit shown in FIG. 37 (when one voice coil is open). The result of comparing the characteristics with

From FIG. 38, it can be seen that short-circuiting the voice coil VC2 side reduces the high frequencies due to the current generated by the coupling. In addition, the reason why the sound pressure is reduced in the low range despite the fact that there is almost no effect of electromagnetic coupling is that the coil wire of the voice coil VC2 oscillates in the magnetic gap, and a braking force is generated by the back electromotive force. It is for

In the case of a speaker device using a third-order low-pass filter (FIG. 31), since the inductance L2 of the low-pass filter is connected in series with the voice coil VC2, the current in the voice coil VC1 side causes back electromotive force in the voice coil VC2. Electric power is generated, but current is difficult to flow at high frequencies. Therefore, the output characteristics of the input signal on the voice coil VC1 side in the high frequency range are close to the state in which the voice coil VC2 side is open. FIG. 31 is a circuit diagram showing an example of the configuration of a speaker device according to an embodiment using a third-order low-pass filter.

As a result, the sound pressure drop in the high range is less than 6 dB compared to the case without a low-pass filter. This phenomenon has little effect when configured as a WF that handles only low frequencies, but must be taken into consideration in the case of a full-range type driver as in this embodiment.

Next, an embodiment in which the speaker device is used as a WF (an embodiment in which a sound pressure difference and a peak occur between the low and high frequencies due to the diffraction effect of the baffle in the WF band) will be described. When it is used as a WF, it is necessary to limit the frequency output of the TW band in the WF output. When a dividing network is used, a desired network circuit may be provided on the voice coil VC1 side for the circuit intended to reverse the baffle diffraction effect (see FIGS. 27 and 31).

FIG. 39 is a circuit diagram showing the configuration of the speaker device 316 in the embodiment used as WF. The upper drive circuit 330C outputs a control signal to the driver 320 used as TW. The middle drive circuit 330A outputs a control signal to the voice coil VC1, and the lower drive circuit 330B outputs a control signal to the voice coil VC2.

Here, the inductance L1 of the low-pass filter is 2.5 mH, the capacitor C1 is 20 μF, and the inductance L2 is 0.5 mH. Also, the inductance L3 of the dividing network is 0.5 mH, and the capacitor C3 is 2.6 μF. Also, the resistor R for impedance correction is set to 7Ω, and the capacitor C2 is set to 6.8 μF.

FIG. 40 is a graph showing simulation results of the frequency characteristics of the control signal output by each of the drive circuits 330A, 330B, and 330C in the circuit shown in FIG. Let Etw be the voltage of the control signal output to the voice coil VC3, and Etotal be the voltage of the combined signal.

As in this example, it can also be implemented for WF in a 2-way sound system using TW. In this example, the sound pressure step and peak to be suppressed are in the bass band (WF band), and the band is limited by a low-pass filter provided in the drive circuit for the driver on the bass band side. not a thing If the sound pressure steps and peaks you want to suppress are in the treble driver band (TW band) or in the mid-range driver (SQ) band such as 3-way, use the treble or mid-range driver. A high-pass filter may be provided in the drive circuit of the technique of the present disclosure, and a high-pass filter may be provided to limit the band on the low-frequency side. However, the high-pass filter in this case may be provided before branching to each VC circuit of the drive circuit of the technology of the present disclosure, as shown in FIG.

According to the technology of the present disclosure, the low-pass filter provided in some of the plurality of drive circuits is adapted to reduce the peak frequency of the frequency characteristics of the sound pressure output according to the shape of the enclosure to the plurality of is set so that the depression frequency in the frequency characteristic of the signal obtained by synthesizing the control signals output from each of the drive circuits corresponds to the frequency characteristic. A plurality of drive circuits output control signals for vibrating the diaphragm of the at least one driver based on the sound source signal.

In this way, the low-pass filters provided in some of the plurality of drive circuits are arranged at the peak frequency of the frequency characteristics of the sound pressure output according to the shape of the enclosure. The recess frequencies in the frequency characteristics of the signal obtained by synthesizing the control signals output from each are set so as to correspond to each other. As a result, it is possible to provide a high-quality speaker device with a simple configuration.

The enclosure according to the technology of the present disclosure has a peak (point of inflection) in the middle band between the low sound pressure range and the high sound pressure range due to the diffraction effect with respect to the driver sound pressure characteristics in the infinite baffle. It can be an enclosure that causes For example, the enclosure can be a rectangular parallelepiped housing.

The drive unit according to the technology of the present disclosure includes one driver, and each of the plurality of drive circuits can output a control signal for vibrating the diaphragm of the driver, based on the sound source signal.

The drive unit according to the technology of the present disclosure includes a plurality of drivers provided corresponding to the plurality of drive circuits, and each of the plurality of drive circuits vibrates the corresponding driver based on a sound source signal. A control signal for vibrating a plate is output, and the drive unit can vibrate the diaphragm corresponding to each of the plurality of drive circuits according to the output of the drive circuit.

The driver according to the technology of the present disclosure can include a voice coil and a magnetic circuit.

A sound system according to the technology of the present disclosure includes the speaker device described above, a signal input unit that receives the sound source signal, and an amplifier that outputs the received sound source signal to the speaker device.

According to the technology of the present disclosure, the signal input unit receives the sound source signal. An amplifier outputs the received sound source signal to the speaker device. In the speaker device, a plurality of drive circuits output control signals for vibrating the diaphragm of the at least one driver based on the sound source signal. Here, the low-pass filter provided in a part of the drive circuits among the plurality of drive circuits filters the peak frequency of the frequency characteristics of the sound pressure output according to the shape of the enclosure to each of the plurality of drive circuits. is set so as to correspond to the recess frequency in the frequency characteristic of the signal obtained by synthesizing the control signals output by . As a result, it is possible to provide an acoustic system with a simple configuration and high sound quality.

It should be noted that the present invention is not limited to the above-described embodiments, and various modifications and applications are possible without departing from the gist of the present invention.

For example, in the above embodiment, the sound pressure difference between the low frequency side and the high frequency side is 6 dB, but it is not limited to this. When considering only the diffraction effect of the baffle, the sound pressure difference between the low frequency side and the high frequency side is 6 dB. This is the sound pressure difference between a sufficiently high frequency that the radiation space can be regarded as 2π and a sufficiently low frequency that it can be regarded as 4π. However, the characteristics of the sound system have other factors that change the frequency characteristics, such as the cone shape of the driver, the configuration of the magnetic circuit, and other parts. It is also possible that the characteristic characteristics can be regarded as optimal.

In such a case, the impedance of the voice coil VC1 and the voice coil VC2 can be arbitrarily adjusted by setting the impedance of the voice coil VC1 and the voice coil VC2 to a value other than 1:1 by making the driving forces of the two systems unequal. It is also possible to use three or more driving circuits and adjust the driving force and the driving coefficient. For example, if the driving forces on the voice coil VC1 side and the voice coil VC2 side are set to 1.3:1 and a low-pass filter is provided on the voice coil VC2 side, the sound pressure difference will be 5 dB. It should be noted that when such a method is used, it should be noted that the size of the recesses is also slightly increased or decreased.

In addition, when configuring two or more coils on a single voice coil bobbin, a method of using voice coils wound on the same axis and at different positions in the vibration direction may be used other than the embodiments. The current direction and the gap magnetic flux direction should be set so that force is generated in the same direction when the same voltage is applied to each.

In addition, a ring-shaped high-conductivity conductor (copper ring, etc.) may be wound around the pole piece of the speaker device to reduce the alternating magnetic flux generated when current flows through the voice coil. This eliminates the impedance of the voice coil and eliminates the need for impedance correction. That is, the design can be made by ignoring the inductance of the voice coil. In addition, by reducing the alternating magnetic flux, the distortion generated in the current can be reduced, and the sound quality can be improved.

When winding two or more voice coils on a single voice coil bobbin, if the voice coils are wound on the same axis and at different positions in the vibration direction, the same voltage is applied to the two windings. The directions of the AC magnetic fluxes generated in each case are opposite to each other. This makes it possible to reduce the mutual influence of each system. As a result, the design can be made by ignoring the inductance of the voice coil. In addition, by reducing the alternating magnetic flux, the distortion generated in the current can be reduced, and the sound quality can be improved.

The disclosure of Japanese application 2022-032793 is incorporated herein by reference in its entirety.

All publications, patent applications and technical standards mentioned herein are to the same extent as if each individual publication, patent application and technical standard were specifically and individually indicated to be incorporated by reference. incorporated herein by reference.

Claims

a drive unit comprising at least one driver including a diaphragm;
an enclosure that houses the driver;
a plurality of drive circuits that output control signals for vibrating the diaphragm of the at least one driver based on the sound source signal;
The drive unit vibrates the diaphragm according to outputs of the plurality of drive circuits,
A low-pass filter is provided in some of the plurality of drive circuits,
In the low-pass filter, the peak frequency of the frequency characteristics of the sound pressure output according to the shape of the enclosure corresponds to the recess frequency in the frequency characteristics of the signal obtained by synthesizing the control signals output from each of the plurality of drive circuits. A speaker device configured to
the driving unit is composed of one driver,
each of the plurality of drive circuits outputs a control signal for vibrating the diaphragm of the driver based on the sound source signal;
2. The speaker device according to claim 1, wherein said drive section vibrates a single diaphragm according to outputs of said plurality of drive circuits.
The drive unit comprises a plurality of drivers provided corresponding to the plurality of drive circuits,
each of the plurality of drive circuits outputs a control signal for vibrating the diaphragm of the corresponding driver based on the sound source signal;
2. The speaker device according to claim 1, wherein the drive section vibrates the diaphragm corresponding to each of the plurality of drive circuits according to the output of the drive circuit.
The speaker device according to any one of claims 1 to 3, wherein the driver includes a voice coil and a magnetic circuit.
a speaker device according to any one of claims 1 to 4;
a signal input unit that receives the sound source signal;
an amplifier that outputs the received sound source signal to the speaker device;
sound system including.