Speaker Device and Acoustic System

A speaker device includes: a limiting unit that limits a signal band of a sound source signal that has been input; a speaker unit that includes a diaphragm; a housing that houses the speaker unit; and a drive circuit that, based on the sound source signal with the limited signal band, outputs a control signal that causes the diaphragm of the speaker unit to vibrate, wherein: the limiting unit limits the sound source signal to a frequency band including a peak frequency of frequency characteristics of an amplitude of the speaker unit in accordance with a shape of the speaker unit and a shape of the housing.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2022-057269 filed on Mar. 30, 2022, the disclosure of which is incorporated by reference herein.

BACKGROUND

Technical Field

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

Related Art

Conventionally, a speaker device that can be made thin (for example, Japanese Patent Application Laid-Open (JP-A) No. 2010-63078) is known. This speaker device is configured by installing plural speaker units in a cabinet, each of the speaker units having a radiating surface from which sound waves are radiated and a back surface that is opposite from the radiating surface.

In the prior art, there is room for improvement in realizing a speaker device that has a simple configuration and is thin.

SUMMARY

An object of the present disclosure is to provide a speaker device and an acoustic system which have a simple configuration and can be made thin.

A first aspect of the present disclosure is a speaker device that includes: a limiting unit that limits a signal band of a sound source signal that has been input; a speaker unit that includes a diaphragm; a housing that houses the speaker unit; and a drive circuit that, based on the sound source signal with the limited signal band, outputs a control signal that causes the diaphragm of the speaker unit to vibrate, wherein: the limiting unit limits the sound source signal to a frequency band that includes a peak frequency of frequency characteristics of an amplitude of the speaker unit in accordance with a shape of the speaker unit and a shape of the housing.

A second aspect of the present disclosure is an acoustic system that includes: the speaker device of the first aspect; a signal input unit that receives the sound source signal; and an amplifier that outputs the received sound source signal to the speaker device.

Effect of the Invention

According to the present disclosure, it is possible to provide a speaker device and an acoustic system which have a simple configuration and can be made thin.

DETAILED DESCRIPTION

Detailed explanation follows regarding the exemplary embodiments of the present disclosure, with reference to the drawings.

Summary of Exemplary Embodiments of the Present Disclosure

Movable parts and fixed parts exist as a structure of a speaker unit of a speaker device. It is necessary to set a clearance between parts so that these parts do not hit against each other during operation.

The total height of the speaker unit of the speaker device is determined from the dimension of each component and the clearance dimension between the fixed parts and the movable parts which ensures a necessary stroke amount. Further, the amplitude of the components of the speaker unit is proportional to the output sound pressure under the same frequency.

Therefore, in the exemplary embodiments of the present disclosure, the amplitude and the output sound pressure characteristics are controlled by providing a resonant structure at an enclosure.

For example, in an acoustic system using a bass reflex type enclosure, by synthesizing the sound pressure characteristics (FIG.1A) directly output from the speaker unit and the sound pressure characteristics (FIG.1B) output from the duct, frequency characteristics of the sound pressure of the entire speaker device are determined (FIG.1C). InFIG.1C, the solid line indicates the sound pressure characteristics directly output from the speaker unit, the dashed line indicates the sound pressure characteristics output from the duct, and the alternate long and short dash line indicates the frequency characteristics of sound pressure of the entire speaker device.

Therefore, by adjusting the resonance frequency of the duct, the amplitude characteristics of the speaker unit can be adjusted, that is, the maximum amplitude of the speaker unit can be adjusted (seeFIG.2). The upper graph ofFIG.2is a graph illustrating sound pressure characteristics output from the entire acoustic system, and the lower graph ofFIG.2is a graph illustrating amplitude characteristics of the speaker unit.

As illustrated inFIG.2, the band of the input signal to the speaker unit is limited. InFIG.2, by limiting the frequency band at the lower side of the frequency indicated by the dotted line (for example, the frequency band below 25 Hz) so as to avoid the maximum amplitude peak, the amplitude of the speaker unit is reduced, and therefore, the clearance between the movable parts can be set smaller.

Further, since the clearance dimension between the movable parts can be reduced, it is possible to make the speaker unit thinner, and it is possible to make the enclosure thinner.

In addition, the adoption of a bass reflex type enclosure does not significantly impair the acoustic output compared to a conventional structure.

First Exemplary Embodiment

Configuration of the Acoustic System According to the First Exemplary Embodiment of the Present Disclosure

FIG.3is a schematic view of an acoustic system10according to an exemplary embodiment of the present disclosure.

As illustrated inFIG.3, the acoustic system10includes a sound source input unit12, an amplifier14, and a speaker device16.

The sound source input unit12receives a sound source signal.

The amplifier14outputs the received sound source signal to the speaker device16.

As illustrated inFIG.4, the speaker device16includes a speaker unit20and an enclosure22that houses the speaker unit20. In the present exemplary embodiment, the enclosure22is a rectangular parallelepiped housing and is a bass reflex type enclosure. The enclosure22includes a duct24.

Further, the speaker device16includes a high-pass filter28to which the sound source signal is input, a drive circuit30that outputs a control signal that causes a diaphragm40(seeFIG.5) of the speaker unit20to vibrate based on the output of the high-pass filter28, and the speaker unit20.

As illustrated inFIG.5, the speaker unit20includes the diaphragm40. The diaphragm40is formed in an annular shape as seen in a front view, and has a cone-shaped front surface that is recessed toward the central portion. The diaphragm40is configured by, as an example, cone paper (a cone made of a material including pulp fibers or the like). A center cap42is arranged at a front central portion side of the diaphragm40. As an example, the center cap42is formed in a dome shape, and is arranged so that a center portion of the center cap42bulges forward.

An outer peripheral portion of the center cap42is formed in a flange shape over the entire circumference and is joined to the front surface of the diaphragm40. An edge44made from an elastic material such as rubber is joined to an outer peripheral portion of the diaphragm40over the entire circumference. The edge44is formed in an annular shape as seen in a front view, and is joined to a frame52over the entire circumference.

A circular hole is formed through a central portion of the diaphragm40, and the edge of the circular hole is joined to a front portion of an outer peripheral surface of a voice coil bobbin46. The voice coil bobbin46is a film made to be in a cylindrical shape. In the drawings, the cross sections of the diaphragm40, the center cap42, the edge44, the voice coil bobbin46, a voice coil48, a damper50, and the frame52are indicated by thick lines for the sake of convenience. The voice coil48, which is configured by an electric wire (as an example, copper wire), which is a linear conductor, is wound around an outer peripheral side of a rear portion of the voice coil bobbin46. Note that the cross section of the voice coil48is simplified for illustration.

An inner peripheral portion of the damper50is joined to the outer peripheral surface of voice coil bobbin46at a portion further to the rear side than the circular hole of the diaphragm40. The damper50is a flexible thin plate member formed in an annular shape as seen in a front view and has a wave-like corrugated portion. The voice coil bobbin46is connected to the frame52via the damper50or the like, and is supported by the damper50or the like in a state such that the voice coil bobbin46can vibrate with respect to the frame52, along the cylinder axis direction of the voice coil bobbin46. Further, the diaphragm40is connected to the frame52via the edge44, and is supported by the edge44in a state such that the diaphragm40can vibrate with respect to the frame52, along the cylinder axis direction of the voice coil bobbin46. Further, the above-described diaphragm40vibrates integrally with the voice coil bobbin46.

An external magnetic circuit56is provided at the rear of the speaker unit20. The magnetic circuit56is configured by a plate58, a magnet60, and a yoke62. The plate58is made of an electromagnetic material, is formed in an annular shape, is arranged at an outer peripheral side of the voice coil48, and is fixed to a rear surface of a bottom wall portion of the frame52. The magnet60is formed in an annular shape, is arranged at the outer peripheral side of the voice coil48, and is fixed to the rear surface of the plate58. The yoke62is fixed to a rear surface of the magnet60.

The yoke62is formed of an electromagnetic material, and includes a disc-shaped base portion that constitutes a rear end portion of the yoke62, and a columnar pole portion that protrudes forward from a center portion of the base portion.

A part of the pole portion is arranged in a space at the inner peripheral side at the rear portion of the voice coil bobbin46. The voice coil48and the voice coil bobbin46are inserted into the magnetic gap between an inner peripheral surface of the plate58and the pole portion of the yoke62.

The voice coil48is connected to an external power source via a terminal (not shown in the drawings).

The drive circuit30outputs a control signal obtained, via the high-pass filter28, from the sound source signal that has been input, to the voice coil48, and causes the diaphragm40of speaker unit20to vibrate by the magnetic circuit56.

The high-pass filter28limits a low frequency side of the signal band of the sound source signal that has been input.

Specifically, the high-pass filter28limits the sound source signal to a low-side frequency band including the peak frequency of the frequency characteristics of the sound pressure output in accordance with the shape of the enclosure22(limits the sound source signal to a frequency band to the left of the dotted line inFIG.2).

The enclosure22includes the duct24as a resonant structure, and the duct24has a shape that results in a resonance frequency that is determined so as to adjust the system resonance frequency. For example, the duct24has a duct resonance frequency that adjusts the system resonance frequency corresponding to the upper limit of the frequency band to be limited (for example, 25 Hz indicated by the dotted line inFIG.2). The system resonance frequency refers to the resonance frequency of the entire acoustic system. Further, the system resonance frequency is preferably a frequency that optimizes the sound pressure characteristics, the amplitude, and the like of the acoustic system.

More specifically, by lengthening or narrowing the shape of the duct24, the duct resonance frequency is lowered, and in accordance therewith, a system resonance frequency with an anti-resonance frequency or a Hermholtz resonance frequency reduced to a lower than conventional value is set to a lower value. In the examples inFIG.2, examples of a system resonance frequency of 40 Hz, 35 Hz, 30 Hz, 25 Hz, and 20 Hz, which are lower than compared to a conventional design in which the system resonance frequency is 45 Hz, are illustrated. Here, the anti-resonance frequency is a frequency at which phase reversal occurs for each sound pressure radiated from the diaphragm40and the duct24when looking at the entire acoustic system. In the band below the anti-resonance frequency, there is an anti-phase relationship (the sound pressure is reduced), and in the band above the anti-resonance frequency, there is an in-phase relationship (the sound pressure is strengthened). In the speaker unit, the amplitude characteristics becomes minimal near the anti-resonance frequency.

As illustrated in the examples ofFIG.2, the maximum amplitude of the speaker unit20can be suppressed at the higher frequency side than the low-side frequency band to be limited.

Therefore, in the present exemplary embodiment, the speaker unit20is configured such that the clearance between parts of the speaker unit20is determined according to this maximum amplitude. Specifically, a clearance C1 between the voice coil48and the yoke62, a clearance C2 between the damper50and the plate58, a clearance C3 between the damper50and the diaphragm40, and a clearance C4 between a front part (for example, a grill cover) and the diaphragm40are configured so as to be clearances obtained by adding the maximum amplitude and a predetermined margin.

Operation of the Acoustic System According to the First Exemplary Embodiment Of the Present Disclosure

The sound source input unit12receives an input of a sound source signal from an audio player or the like.

The amplifier14outputs the received sound source signal to the speaker device16.

The high-pass filter28of the speaker device16limits the low-frequency side of the signal band of the sound source signal and outputs the sound source signal to the drive circuit30.

Based on the sound source signal with the limited low-frequency side of the signal band, the drive circuit30outputs the control signal to speaker unit20and causes the diaphragm40of the speaker unit20to vibrate.

The high-pass filter28limits the sound source signal to a low-side frequency band including the peak frequency of the frequency characteristics of the sound pressure output in accordance with the shape of the enclosure22(limits the sound source signal to a frequency band at a lower side than the dotted line inFIG.2). Further, the duct24of the enclosure22has a duct resonance frequency that adjusts the system resonance frequency corresponding to the upper limit of the frequency band to be limited.

As a result thereof, the maximum amplitude of the speaker unit20can be suppressed at the higher frequency side than the low-side frequency band to be limited.

Since the clearance between parts of the speaker unit20is configured to be determined in accordance with the maximum amplitude, it is possible to make the speaker unit20thinner.

As described above, in the acoustic system according to the first exemplary embodiment of the present disclosure, the sound source signal is limited to a low-side frequency band including the peak frequency of the frequency characteristics of the sound pressure output in accordance with the shape of the enclosure22, and the drive circuit30causes the diaphragm40of the speaker unit20to vibrate based on the sound source signal with the limited signal band, and therefore, can provide a speaker device that has a simple configuration and can be made thin.

In addition, compared to a case in which a low-side frequency band including the peak frequency of the frequency characteristics of the sound pressure output in accordance with the shape of the enclosure22is not limited, the amplitude of the speaker unit is reduced, and therefore, it is possible to set a smaller clearance between the movable parts and it is possible to make the speaker unit thinner. Further, by using a bass reflex type enclosure, the acoustic output is not greatly impaired.

Second Exemplary Embodiment

Next, explanation follows regarding an acoustic system according to a second exemplary embodiment. Note that parts having the same configuration as in the first exemplary embodiment are denoted by the same reference numerals, and explanations thereof are omitted.

The second exemplary embodiment differs from the first exemplary embodiment in that a passive radiator is used.

As illustrated inFIG.3, an acoustic system210includes the sound source input unit12, the amplifier14, and a speaker device216.

As illustrated inFIG.6, the speaker device216includes the speaker unit20and an enclosure222that houses the speaker unit20. In the present exemplary embodiment, the enclosure222is a rectangular parallelepiped housing and is a passive radiator type enclosure. The enclosure222includes a passive radiator224.

The enclosure222includes the passive radiator224as a resonant structure, and the passive radiator224includes a diaphragm226and an edge228which result in a resonance frequency that is determined so as to adjust the system resonance frequency. For example, the passive radiator224has a passive radiator resonance frequency that adjusts the system resonance frequency corresponding to the upper limit of the frequency band to be limited.

More specifically, by adjusting the weight of the diaphragm226and the size of the spring of the edge228, the passive radiator resonance frequency is made to be a lower than conventional value, and in accordance therewith, the system resonance frequency is set to a lower value.

Since other configuration and operation of the acoustic system210according to the second exemplary embodiment are the same as those in the first exemplary embodiment, explanation thereof is omitted.

Third Exemplary Embodiment

Next, explanation follows regarding an acoustic system according to a third exemplary embodiment. Note that parts having the same configuration as in the first exemplary embodiment are denoted by the same reference numerals, and explanations thereof are omitted.

The third exemplary embodiment differs from the first exemplary embodiment in that a counter-drive type speaker unit is used.

As illustrated inFIG.3, the acoustic system10includes the sound source input unit12, the amplifier14, and a speaker device316.

Further, the speaker device316includes the high-pass filter28, the drive circuit30, and a speaker unit320.

As illustrated inFIG.7, the speaker unit320includes a diaphragm340. The diaphragm340is formed in an annular shape as seen in a front view, and has a cone-shaped front surface that is convex toward the central portion. A center cap342is arranged at a front central portion side of the diaphragm340. An edge344made from an elastic material such as rubber is joined to an outer peripheral portion of the diaphragm340over the entire circumference. The edge344is formed in an annular shape as seen in a front view, and is joined to a frame352over the entire circumference.

A circular hole is formed through a central portion of diaphragm340, and the edge of the circular hole is joined to a front portion of an outer peripheral surface of a voice coil bobbin346. In the drawings, the cross sections of the diaphragm340, the center cap342, the edge344, the voice coil bobbin346, a voice coil348, a damper350, and the frame352are indicated by thick lines for the sake of convenience. The voice coil348is wound around a rear outer peripheral side of the voice coil bobbin346. Note that the cross section of the voice coil348is simplified for illustration.

An inner peripheral portion of damper350is joined to the outer peripheral surface of voice coil bobbin346at a portion further to the front side than the circular hole of the diaphragm340. The damper350is a flexible thin plate member formed in an annular shape as seen in a front view and has a wave-like corrugated portion. The voice coil bobbin346is connected to the frame352via the damper350or the like, and is supported by the damper350or the like in a state such that the voice coil bobbin346can vibrate with respect to the frame352, along the cylinder axis direction of the voice coil bobbin346. Further, the diaphragm340is connected to the frame352via the edge344, and is supported by the edge344in a state such that the diaphragm340can vibrate with respect to the frame352, along the cylinder axis direction of the voice coil bobbin346. Further, the above-described diaphragm340vibrates integrally with the voice coil bobbin346.

An external magnetic circuit356is provided at the rear of the speaker unit320. The magnetic circuit356is configured by a plate358, a magnet360, and a yoke362.

The drive circuit30outputs a control signal obtained, via the high-pass filter28, from the sound source signal that has been input, to the voice coil348, and causes the diaphragm340of speaker unit320to vibrate by magnetic circuit356.

Further, in the same manner as in the above-described first exemplary embodiment, the maximum amplitude of the speaker unit320can be suppressed at the higher frequency side than the low-side frequency band to be limited.

Therefore, in the present exemplary embodiment, the speaker unit320is configured such that the clearance between parts of the speaker unit20is determined according to this maximum amplitude. Specifically, the speaker unit320is configured such that a clearance C1 between the voice coil348and the yoke362, a clearance C2 between the diaphragm340and the yoke362, a clearance C3 between the damper350and the diaphragm340, and a clearance C4 between a front part (for example, a grill cover) and the voice coil bobbin346are clearances obtained by adding the maximum amplitude and a predetermined margin.

Since other configuration and operation of the acoustic system310according to the third exemplary embodiment are the same as those in the first exemplary embodiment, explanation thereof is omitted.

Examples

Explanation follows regarding an example of the acoustic system described in the first exemplary embodiment. In the example, the capacity of the enclosure was set to 10 L, and the anti-resonance frequency or Helmholtz resonance frequency was adjusted to be lower than that of a conventional bass reflex type design.

An acoustic system using a closed type enclosure having the same capacity as the enclosure according to the first exemplary embodiment and an acoustic system having an infinite spatial volume at the rear side are comparative examples.

FIG.8is a graph illustrating frequency characteristics of sound pressure of the entire acoustic system in the acoustic system described in the first exemplary embodiment and the comparative examples. Further,FIG.9is a graph illustrating amplitude characteristics of the speaker unit in the acoustic system described in the first exemplary embodiment and in the comparative examples.

FromFIG.8andFIG.9, it was found that the acoustic system described in the first exemplary embodiment can achieve sound pressure equal to or greater than the acoustic system of the comparative examples which had an enclosure volume equal to or greater than that of the acoustic system described in the first exemplary embodiment, while reducing the amplitude of the speaker unit.

According to the present disclosure, the limiting unit limits the sound source signal to a frequency band including a peak frequency of frequency characteristics of an amplitude of the speaker unit in accordance with the shape of the speaker unit and the shape of the housing. Further, the drive circuit outputs, based on the sound source signal with the limited signal band, a control signal that causes the diaphragm of the speaker unit to vibrate. The housing is, for example, a speaker enclosure, a rear-opening enclosure for a speaker, vehicle interior parts (trim, pillars, instrument panels, headlining, luggage, trunk room or the like) or plate parts. Furthermore, the peak frequency is the frequency at which the maximum point or the maximum amplitude value is obtained.

As described above, the sound source signal is limited to a frequency band including a peak frequency of frequency characteristics of an amplitude of the speaker unit in accordance with the shape of the speaker unit and the shape of the housing, and the drive circuit causes the diaphragm of the speaker unit to vibrate based on the sound source signal with the limited signal band. As a result, it is possible to provide a speaker device that has a simple configuration and that can be made thin.

The housing according to the present disclosure can include a resonant structure.

The housing according to the present disclosure is a bass reflex type enclosure, and the resonant structure is a duct.

The limiting unit according to the present disclosure can limit a low-side frequency band.

The housing according to the present disclosure includes a resonant structure, and the resonant structure can have a resonance frequency that adjusts a system resonance frequency corresponding to an upper limit of a frequency band to be limited.

The clearance between parts of the speaker unit according to the present disclosure can be configured so as to be a clearance that is determined in accordance with a maximum amplitude of the speaker unit.

The speaker unit according to the present disclosure further includes a damper, a voice coil, a yoke, and a plate, and the speaker unit can be configured so that the clearance between the damper and the diaphragm, the clearance between the voice coil and the yoke, and the clearance between the damper and the plate are clearances that are determined in accordance with the maximum amplitude.

The speaker unit can be configured such that a clearance between the speaker device according to the present disclosure and a part arranged corresponding to the speaker device is a clearance determined in accordance with the maximum amplitude.

The speaker unit according to the present disclosure can be a counter-drive type speaker unit.

According to the present disclosure, a signal input unit receives the sound source signal. The amplifier outputs the received sound source signal to the speaker device. Then, in the speaker device, the sound source signal is limited to a frequency band including a peak frequency of frequency characteristics of an amplitude of the speaker unit in accordance with the shape of the speaker unit and the shape of the housing, and the drive circuit causes the diaphragm of the speaker unit to vibrate based on the sound source signal with the limited signal band. As a result, it is possible to provide a speaker device that has a simple configuration and that can be made thin.

The present disclosure is not limited to the above-described exemplary embodiments, and various modifications and applications are possible within a range that does not depart from the gist of the technique of the present disclosure.

For example, although the case of using a bass reflex type enclosure or a passive radiator type enclosure has been described as an example in the above-described exemplary embodiments, the present invention is not limited thereto. The enclosure may be an enclosure having a resonant structure other than a duct or a passive radiator.