WO2020066037A1

WO2020066037A1 - Speaker system capable of increasing driving power without changing heat loss in low-frequency sound range and having improved reproduction characteristic

Info

Publication number: WO2020066037A1
Application number: PCT/JP2018/037441
Authority: WO
Inventors: 角元　純一
Original assignee: 角元　純一
Priority date: 2018-09-25
Filing date: 2018-10-05
Publication date: 2020-04-02
Also published as: JP6597986B1; JP2020053749A

Abstract

[Problem] With respect to a small full-range speaker system, it is difficult, in a vibration-type speaker which vibrates a speaker unit, to achieve good reproduction in an intermediate band between two bands of a super low-frequency sound reproduction band obtained by vibrating the speaker unit and a low-frequency sound reproduction band obtained by vibration of a cone of the speaker unit. [Solution] In the intermediate frequency band between the super low-frequency sound reproduction band obtained by vibration of the speaker unit and the low-frequency sound reproduction band obtained by vibration of the cone of the speaker unit, a low-frequency sound resonator is provided in a cabinet of the speaker system to bring the low-frequency sound reproduction band obtained by vibration of the cone of the speaker unit in the direction of a resonance frequency of the resonator, whereby it becomes possible to enhance reproduction performance in the intermediate frequency band between the low-frequency sound reproduction band obtained by vibration of the speaker unit and the low-frequency sound reproduction band obtained by vibration of the cone of the speaker unit, reduce an interval therebetween, and increase driving power of a voice coil without increasing heat loss of the voice coil in the low-frequency sound reproduction band.

Description

A speaker system that can increase the driving power without changing the heat loss in the low frequency range and improve the reproduction characteristics

A bass reproduction method for small and lightweight speakers that makes use of the passive radiator effect.
By connecting the speaker unit and cabinet with an elastic body and vibrating the speaker unit, the vibration energy is transmitted to the structure of the installation destination, and a wider radiant area of the structure of the installation destination is used to produce stronger bass reproduction. Vibration phase relationship between passive radiator and cone

Mechanical vibration analysis and design

Actual application 2015-3298
The present invention relates to a vibrating speaker and a method of correcting bass reproduction characteristics thereof.
Vibration type speaker is a small and lightweight speaker unit, which is one of the powerful ways to extend the bass reproduction range.However, since it is a method of improving bass reproduction efficiency using strong resonance characteristics, it is possible to obtain a wide reproduction band. difficult. It is necessary to correct this weak point by signal processing, but if the weak point is corrected too much, an abnormal sound will be reproduced, and precise correction is required so as not to exceed the limit of linearity.
Patent application 2015-221089
The invention relates to the structure of a vibration type speaker described in the claims.
Japanese Patent Application No. 2010-251188 Loudspeaker device Japanese Patent Application No. 2011-514324 Loudspeaker device JP2010-097146 Sound absorbing structure group and acoustic room JP2010-097145 Sound absorbing structure group and acoustic room JP2010-031582 Sound absorbing structure group and acoustic room 2007 The speaker system and speaker enclosure design method described above relates to improving bass reproduction performance.

The terms and symbols defined in the claims are the same in the description.

Exercise 1.
Due to the wide valley Bom of the impedance characteristic between the resonance frequency fm of the mechanical vibration of the vibration type speaker and the resonance frequency f0 mainly determined by the speaker unit and the cabinet, it is difficult to obtain the expected bass reproduction characteristic.
This is shown in the characteristic diagram of the test sample in FIG.
The graph of FIG. 1 is a characteristic diagram of the impedance. Double Edge means a vibrating speaker. The small peak near 55 Hz is due to the second resonance, and the large peak near 260 Hz is due to the first resonance.
The graph of FIG. 2 is a characteristic diagram of the vibration amplitude of the cone of the test sample of FIG. Double Edge
The small peak near 55 Hz and the small valley near 75 Hz are due to the second resonance.

Exercise 2.
There is a method of using a passive radiator to fill the resonance frequency fpr in the middle of Bom.However, as a characteristic of the passive radiator, in the band lower than fpr, the vibration of the cone and the passive radiator is in opposite phase or opposite phase based on the sound pressure. There is a close relationship that the fundamental wave of the reproduced signal is canceled out, so that harmonic distortion and cross-modulation distortion remain.
Therefore, in a speaker system using a passive radiator, it is general to make low-frequency cutoff for suppressing reproduction of this band at the stage of signal processing.
FIG. 5 shows a distortion characteristic diagram of the test sample.
Doubl Edge + OuterPR is the characteristic when the outer PR is combined with the vibration type speaker system, and Doubl Edge + InnerPR is the characteristic when the inner PR of the present invention is combined with the vibration type speaker system.
The graph of FIG. 5A shows the speaker system of the sample under test.
When the input voltage is 50% of the nominal rating, the Doubl Edge + OuterPR side is 73.5Hz.
FIG. 7 is a spectrum characteristic diagram of a reproduced sound at 78.0 Hz on the Double Edge + InnerPR side. The reason that the two frequencies are different by a half octave is to make it easy to see the difference between the two characteristics.
73.5Hz is the lowest open string vibration frequency of the contrabass. The peak starting at 73.5Hz * 2 = 157Hz and appearing in the high frequency band is a harmonic distortion component.
FIG. 5B is a table of numerical values picked up from the graph. Each numerical value is the dB converted value of the ratio of the second to seventh harmonics when the fundamental wave is 0 dB.
In the case of Doubl Edge + OuterPR, if the distortion of the third harmonic and the fourth harmonic is combined, the distortion rate will be 53% of the fundamental wave.
The main cause of this distortion is that the fundamental wave is distorted and the phases of the radiation sound of the outer PR and the radiation sound of the cone are opposite, so that the fundamental wave is canceled.

Issue 3.
When filling the impedance valley Bom with a passive radiator,
Since the frequency range lower than fpr cannot be used as the reproduction band, if fpr is close to f0,
The area that is not suitable for reproduction is widened, which defeats the purpose of obtaining a good and wide bass reproduction band.

Issue 4.
If the interval between fpr and fo is wide, there will be a deep valley in this frequency band, making it difficult to obtain uniform bass reproduction characteristics. At the same time, the ratio of the heat loss of the voice coil to the driving power of the voice coil in this band increases, which causes the conversion efficiency of electric energy to acoustic energy to decrease.
This is shown in the Doble Edge + OuterPR characteristic diagram of the test sample in Fig. 1.
The graph of FIG. 2 is a characteristic diagram of the vibration amplitude of the cone of the test sample of FIG.
The deep valley near 160Hz of Double Edge + Outer-PR is due to the phase relationship between the first resonance and the outer PR.
Between fpr and fo there are two steep and high peaks around 105Hz and 260Hz and one deep valley around 160Hz. In this valley, the ratio of the heat loss of the voice coil to the driving power is high.
The double edge valley around 55Hz is due to the second resonance.

Means 1.
Cover the radiating surface of the passive radiator to the outside of the cabinet with a closed box.
This is the inner PR.

Means 2.
The resonance frequency fipr of the inner PR is determined by design so that the steep peak shape of the impedance characteristic at fo in the middle of Bom is broken and smooth.

Effect 1.
In a frequency band lower than the resonance frequency fipr of the inner PR, the vibration of the passive radiator does not radiate acoustic energy toward the outside of the cabinet, and does not cancel the acoustic energy radiated by the cone in this band.
As a result, it is possible to design such that bass reproduction characteristics with less distortion can be obtained.

Effect 2.
As a result of Effect 1,
In the outer PR, this band had to be cut off in the low range,
In the inner PR, it is possible to design an acoustic signal processing capable of applying low-frequency emphasis.
Therefore, in this band, it is possible to design the bass reproduction characteristics to be significantly improved, and as a result, it is possible to extend the reproduction band to a lower frequency band.

Effect 3.
From the property that fo is attracted to fipr by the interaction between fipr and fo,
It is possible to design so that fo, fipr, and fm have a gentle mountain-shaped impedance characteristic.
Therefore, it is possible to design a bass that can significantly improve bass reproduction characteristics in the band.

Effect 4.
Since it is possible to design the average value of the absolute value of the impedance to be 1.4 to 3 times the resistance value of the voice coil in the Bom band with a gentle mountain shape,
If the heat loss of the voice coil is constant, the drive voltage in this band can be increased from 1.4 times to 3 times.
Or
The DC resistance of the voice coil can be increased from (1/2) to (1/9) times.
A design having a degree of freedom within a range in which one or both of them can be proportionately made possible.
As a result, the driving power of the voice coil is increased from 1.4 times to 3 times, and most of the driving power that can be increased in the band Bio is energy of acoustic radiation, and the conversion efficiency in this band can be greatly improved.
In the impedance characteristic diagram, since the DC resistance of the voice coil is also synthesized, the impedance corresponding to the actual acoustic radiation is deeper than the impedance valley read from the graph. Therefore, the conversion efficiency to acoustic energy in the valley is extremely small, and generally differs from the characteristics felt from the graph. Even if an attempt is made to fill this valley with equalizing, the dynamic range is insufficient, and driving at the rated power cannot be achieved at all.
For these reasons, it can be verified by experiments that if the impedance characteristic is several dB larger than the DC resistance of the voice coil, the reproduction characteristic in this band can be remarkably improved.

Figure of impedance characteristics of one sample for explanation of conventional problems Vibration amplitude characteristic diagram of the cone of the test sample with the impedance characteristics of Fig. 1 Impedance characteristic diagram when improvement of the present invention is added to the test sample of FIG. Fig. 3 Vibration amplitude characteristics of the sample cone with impedance characteristics shown in Fig. 3 Comparison diagram of distortion characteristics of outer PR and inner PR Comparison configuration diagram of the conventional and the present speaker system Explanatory drawing of test sample

Small and lightweight speaker system for small cars Ultra-small speaker system for portable terminals Small speaker system for desktop

Small speaker system with high bass reproduction efficiency and easy bass reproduction design

FIG. 1 is an impedance characteristic diagram of a test sample for explaining a conventional problem.
The horizontal axis is frequency, and the vertical axis is impedance.
10ohm is a pure resistance of 10 ohms, Double + Edge is the impedance characteristic of one sample of the vibration type speaker system, and Double Edge + Outer PR is the impedance characteristic of the sample of the vibration type speaker system with the outer PR added. The description of this characteristic diagram is as described in Problem 1.

FIG. 2 is a vibration amplitude characteristic diagram of a sample cone having the impedance characteristic of FIG.
The horizontal axis is frequency and the vertical axis is vibration amplitude.
Double Edge and Double Edge + Outer PR are the vibration amplitude characteristics of the sample of the vibration type speaker system and the vibration amplitude characteristics of the sample with the outer PR added to the vibration type speaker system, respectively. The description of this characteristic diagram is as described in Problem 3.

FIG. 3 is an impedance characteristic diagram of an inner-PR sample when the sample of FIG. 1 is improved according to the present invention. The horizontal axis is frequency, and the vertical axis is impedance.
Double Edge + innerPR PR-Back Cabity = XXcm ^ 3
XXcm ^ 3.
Differences in impedance characteristics are shown for three types of closed boxes, 5cm ^, 11cm ^ 3 and 18cm ^ 3.
When the volume of the closed box is 5 cm ^ 3, the fipr is high, and although it approaches fo, it moves away from fm, so the impedance characteristics in the band Bom greatly fluctuate.
When the volume of the closed box is 11cm ^ 3, the fluctuation of the impedance characteristics in the band Bom is small.
When the volume of the closed box is 18 cm ^ 3, the fluctuation of the impedance characteristics in the band Bom is large. As described above, the impedance characteristic of the band Bio greatly changes due to the mutual interference between the first resonance, the second resonance, and the third resonance. The characteristic to be used is determined by design.
In order for the band Bio to have a gentle mountain shape, it is necessary to finely adjust the volume of the closed box of the inner PR and the mass of the weight due to the interaction of a plurality of resonance characteristics.

FIG. 4 is a vibration characteristic diagram of the cone of the test sample of the inner PR having the impedance characteristics of FIG. The horizontal axis is frequency and the vertical axis is vibration amplitude.
The small peak around 70Hz is due to the vibrating speaker system. The vibration of the cone is about 4 Hz below the rising line of 20 dB per decard from around 200 Hz to the low frequency up to around 70 Hz. In addition, it shows that there is no constriction in the band Bio as compared with the case where the outer PR of FIG. 2 is used. In addition, since the reproduced signals of both the cone and inner-PR in the Bio band are not canceled out, the characteristics unique to the speaker system of this EUT were compensated by an equalizer of at most 4 dB over 70 Hz. It shows that it is enough. In addition, in the low frequency range from around 70 Hz, the structure vibrates due to the strong mechanical vibration generated by the vibrating speaker system, generating an ultra-low sound. Therefore, sufficient bass reproduction characteristics can be obtained in the range of fo or less.

FIG. 5 is a comparison diagram of the distortion characteristics when the applied voltage to the speaker system is the same for both the outer PR and the inner PR.
The horizontal axis is frequency, and the vertical axis is sound pressure level.
The distortion characteristics of the outer PR are as described in Problem 2.
Double-Edge + Inner-PR is a distortion characteristic when inner PR is used.
The frequency is changed only by a semitone to make it easier to compare with the distortion characteristics when using the outer PR. As can be seen from FIG. 5A, the reproduced sound pressure at the fundamental frequency in the case of the inner PR is 10 dB higher than that of the outer PR. FIG. 5B shows the ratio of the harmonic to the fundamental wave in dB. 1st to 7th indicate the order of harmonics, respectively. The proportion of harmonics was reduced by 11 dB or more, 7 dB, 8 dB, 18 dB or more, 17 dB, and 17 dB at each frequency, indicating that significant improvement was achieved.

FIG. 6 is a comparative configuration diagram of the speaker system of the related art and the present invention.
6A is a configuration diagram in the case of the outer PR, FIG. 6B is a configuration diagram in the case where the inner PR is on the back of the cabinet, and FIG. 6C is a diagram in which the inner PR is in the space inside the cabinet. FIG. 6D shows a configuration diagram in a case where a plurality of inner PRs and a plurality of side walls of the cabinet are provided.
Cabinet is a cabinet, SP is a speaker unit, 2nd Edge is an elastic film to give the degree of freedom necessary to vibrate the speaker unit in the vibration axis direction,
Outer PR is outer PR, and Inner PR is inner PR.

FIG. 7 is a photograph of the test sample. This test sample is a working sample for comparing and explaining the explanation of the support of the present invention with the conventional product on data.
In the case of the inner PR structure, two test pieces are installed on the left and right sides of the dashboard near the windshield of a medium-sized passenger car, for a total of two pieces. An acoustic performance replacing four door speakers can be obtained.
Since the speaker system is small, it is possible to install the speaker system in front of the driver's seat, and it is possible to secure sufficient sound quality and volume for the full-band acoustic radiation from the front even in the rear seat. In addition, although it is an experimental result, as a result, there is also obtained an effect that the rate of raising the volume with respect to traveling noise during high-speed traveling can be reduced as compared with the door speaker.

The speaker system is
Outer diameter 72mm
Height 65mm
Total weight 211g

The speaker unit is
Nominal diameter 2.25 inch Nominal impedance 8ohm
Nominal allowable power 10W
120g

The elastic membrane that connects the speaker unit and the frame
Material Latex for balloon Thickness 0.3mm
7% tension in all directions, width 3 mm

Inner PR is
Radiation window area 34cm ^ 2
Weight 5g * 8 pieces = 40g, adjustable in 10g increments Internal volume 5cm ^ 3, 11cm ^ 3, 18cm ^ 3, slide adjustable Elastic membrane material Foil latex Thickness 0.3mm
Its tension is 7% and it is stretched in all directions. Its width is 3mm.

Cabinet is 144cm ^ 3 in volume, including speaker unit structure

FIG. 7A is a photograph of the sound emitting surface side of the test sample.
2nd Edge is an elastic film to give the degree of freedom necessary to vibrate the speaker unit in the vibration axis direction. The elastic membrane uniformly stretches a circular 0.3 mm latex sheet by 7%, glues the outer frame with tension applied, and glues the frame on which the speaker unit is placed inside the latex sheet, and attaches it to the frame. The speaker unit is bonded. There is no need to use latex for performance.
In the case of a test sample, it is necessary to significantly shorten the period until reaching the optimum state. Therefore, in order to find the optimal elasticity and movable range, a cut-and-try process with a minimum waiting time is required. All parts except speaker units are prototyped by hand on the desk, minimizing one cycle of correction work and performance confirmation time, and shortening the entire process until the result is obtained. We need to find the optimal solution for some system.
It uses latex, which is easily available and quick to process, in order to keep track of the methods and procedures for the optimal elastic modulus and the optimal solution of the movable range. Latex is not a material suitable for mass production of car audio used in harsh environments.
Cone is the speaker unit cone, Edge is the speaker unit edge, Frame is the speaker unit frame, Cabinet is the cabinet,
IPR Cover is the back cover that adjusts the volume of the inner PR, Adjust is the sliding direction of the back cover that adjusts the volume of the inner PR, IPR Case is the side cabinet of the inner PR, IPR Weight is the weight of the inner PR, and IPR Edge is the inner PR. The elastic film, IPR Plate, is a base on which the weight of the inner PR is evenly placed on the elastic film, and IPR Frame is a frame of the inner PR elastic film.
In the case of the test sample, the elastic film of the inner PR is the same as the 2nd Edge.

The fo is a factor mainly due to the characteristic of the speaker unit, the volume of the cabinet, and the nature of the air. However, in a small speaker, the effect of the small volume of the cabinet has a great effect. We would like to design the fo around 150Hz if possible, but it is necessary to consider the coordination with the high frequency performance. Therefore, it is normal for the speaker system of this size to be 200Hz or more.
The fo of the test sample used for the demonstration of this project is at 260Hz. This value can be said to be fatal in the case of car audio where bass reproduction is a necessary condition.

However, reducing the size and weight of the speaker system is one of the issues for passenger cars in recent years. With such a size and weight, if the entire band can be reproduced, its value is sufficient. How to devise a speaker system with an fo of 260Hz so that it can reproduce up to ultra-low sound is also a major issue at the speaker system design site.
On the other hand, vibration type speakers
By vibrating the speaker unit with its own vibration and transmitting the vibration to a large structure through a cabinet, the ultra-low frequency band is reproduced using the acoustic radiation effect of the structure. This type of loudspeaker system is not rare on the market because of its small size and easy reproduction of ultra-bass.
However, it is difficult to achieve good reproduction of the band between the ultra-low and mid-low frequencies, and in the case of car audio that is widely spread to various user groups in daily life, versatility is required for sound quality. Therefore, the vibration type speaker cannot satisfy the universal standard regarding sound quality.

Therefore, it is easy to come up with a method to cover the intermediate band between fo and fm using a passive radiator, but there is a reason that it has not been put to practical use.
Passive radiators can easily reproduce the low-pitched sound, which is an inevitable method for small speakers. Passive radiators are used in almost all small speakers capable of reproducing low-frequency sounds in the market in recent years.
However, even with a passive radiator, the bass feeling can be reproduced, but the distortion is large in a low frequency band lower than fpr, and the reproduced sound of a bass drum has an uncomfortable sound quality that is significantly different from the original sound in an attack part. There are two reasons for this.
The first reason is that
In the frequency band slightly higher than fpr, the radiated sound of both the passive radiator and the cone are in or near in phase in the steady state, but in the transient state of the attack, both are in or near out of phase, Gives great discomfort to the sound quality. This sound quality is far from universal standards.
The second reason is that
In the frequency band lower than around fpr, both the phase of the radiated sound from the passive radiator and the phase of the radiated sound from the cone are constantly reversed or close to reversed phase. Due to the prominent wave components. Therefore, low-frequency cutoff from around fpr must act as low-frequency cutoff.
As a result, the outer PR does not have a reproduction characteristic that satisfies a universal level of market needs in a wide bass range.

FIG. 7B is a photograph of the back side of the test sample. The back is the back cover of the inner PR, which has a structure in which the internal volume can be slid and adjusted, and the optimal volume is selected in combination with the weight.

FIG. 7C is a photograph of the inside of the inner PR of the test sample. A circular 0.3mm latex sheet is evenly stretched by 7%, the outer frame is adhered under tension, and a base for placing a weight on the inside of the latex sheet is adhered.
Multiple weights of 1.5mm thickness are bonded. While checking the impedance characteristics, select the optimal mass according to the number of weights.
FIG. 7D is a photograph of the inside of the inner PR of the test sample. This is a state where the frame of the side wall of the inner PR is attached.

The same symbol has the same function in each figure.
fo 1st resonance
Resonance characteristics depending on acoustic properties of speaker units and cabinets
fm 2nd resonance
The main factors are the speaker unit and the volume of the air chamber on the back.
Resonance characteristics of mechanical vibration
fpr Outer PR resonance frequency
The valley of the impedance characteristic between Bom fo and fm
fipr Inner PR resonance frequency
Band between Bio fipr and fo
Band between Bim fipr and fm
Multiplier of the representative value of K Bim impedance to DC resistance of voice coil

1 and 2
Impedance impedance
Displacement vibration amplitude
10ohm pure resistance
Elastic membrane connecting the Double Edge speaker unit and cabinet
Double Edge + Outer PR Combination of vibration type speaker and outer PR

3 and 4
Doubl Edge + Inner PR Combination of vibration type speaker and inner PR
PR Back Capacity = XX ^ 3 XX is the volume of the inner PR sealed box

Figure 5
1st ,,, 7th From fundamental wave to 7th harmonic
Double Edge + Outer PR (1st-xxdB)
DB converted value of the ratio of harmonic to fundamental wave of the combination of vibrating speaker and outer PR
Double Edge + Inner PR (1st-xxdB)
DB converted value of the ratio of the harmonic to the fundamental wave of the combination of vibrating speaker and inner PR

FIG.
Cbinet cabinet
SP is a speaker unit
2nd Edge elastic membrane,
Outer PR Outer PR
Inner PR Inner PR

FIG.
Elastic membrane to attach 2nd Edge speaker unit to cabinet
Cone cone
Edge Edge of the cone of the speaker unit
Frame Frame of speaker unit
Cabinet cabinet
IPR Cover Inner PR back cover
Adjust Move the back cover to adjust the inner PR inner volume
IPR Case Inner PR side case
IPR Weight Inner PR weight
IPR Edge Inner PR elastic membrane
A platform on which the weight of the IPR Plate inner PR is placed
IPR Frame Inner PR elastic membrane frame

Claims

A unit that converts an electric signal to an acoustic signal is called a speaker unit,
A speaker system that integrates a speaker unit and a cabinet is called a speaker system.
The vibration direction of the voice coil of the speaker unit is the vibration axis,
A speaker whose speaker unit has a movable range in the vibration direction is a vibration type speaker,
The resonator is one or both of a resonator of air vibration and a resonator of mechanical vibration, which resonates by transfer of energy through air in the cabinet due to voice coil vibration of the speaker unit,
;
The electrical impedance characteristic of the speaker system is defined as impedance or impedance characteristic,
The resonance characteristic called fo, which is mainly determined by the acoustic properties of the speaker unit and the cabinet, is defined as the first resonance.
Let fo be the resonance frequency of the first resonance,
;
The mass of the speaker unit,
The elastic stiffness that supports the speaker unit,
The resonance characteristic of the mechanical vibration, which is mainly determined by the volume of the air chamber on the back of the speaker unit and
Let the resonance frequency of the second resonance be fm,
;
The passive radiator made on the wall of the speaker cabinet is used as the outer PR,
The outer PR shall have an acoustic emission surface outside the cabinet,
Let the resonance frequency of the outer PR be fpr,
;
In a vibrating speaker system having fo due to the first resonance and fm due to the second resonance, which is an effective means for bass reproduction of a small speaker system,
In a vibration type speaker system that is imposed with full band reproduction,
In general, it is not easy to lower fo without sacrificing high frequency reproduction characteristics,
Generally, it is not easy to bring fm close to fo without reducing the mass of the speaker unit so as to sacrifice the overall playback characteristics.
The valley of the impedance characteristic generated between fo and fm under these conditions is defined as the impedance valley, and the band is defined as Bom.
;
Producing the outer PR where the resonance frequency fpr exists within the range of Bom is
It is one of the well-known methods that can fill the impedance valley Bom to some extent.However, although a low pitch can be obtained by hearing, the characteristics of the valley between fpr and fo are not filled,
In the low-frequency range from fpr to fm, the phases of the outer PR vibration and the cone vibration become opposite in phase with respect to the reproduced sound pressure. The characteristic that the distortion rate and the intermodulation distortion rate increase becomes the bass cancellation effect,
;
Designed to reduce the width of the Bom necessary for reproducing good bass characteristics,
The essence of the present invention is to solve the problem of how to improve the overall reproduction characteristics, which can be obtained by filling the impedance valley Bom with high impedance characteristics.
;
The window for sound radiation to the outside of the outer PR cabinet is a PR radiation window,
An inner PR is a resonator that has a unique resonance characteristic formed by a PR radiation window having a window facing the space inside the closed box and cabinet, which is made by closing the PR radiation window with a closed box,
The resonance characteristic of the inner PR is the third resonance,
The inner PR diaphragm is used as the inner PR diaphragm,
Having the inner PR as the first,
;
The resonance frequency due to the resonance characteristics of the inner PR is fipr,
fipr should be within Bom
The volume of the closed box that constitutes the inner PR,
Radiation area and mass of inner PR diaphragm,
Shall be selected and designed.
;
Bio is the band between fipr and fo,
Bim is the band between fipr and fm,
;
According to the first result,
In band Bim, since the inner PR diaphragm does not radiate sound to the outside of the cabinet, the second is to use the function of eliminating the bass cancellation effect that occurs in the case of the outer PR,
The fact that the phase of the vibration of the inner PR diaphragm and the vibration of the cone in or near the same phase near the third resonance fipr is used to make the impedance characteristic near the fipr a gentle mountain shape is used. 3, and
With the shape of a gentle mountain, the shape of the shape where the peak of the steep mountain shape is lowered and the skirt is widened or the shape of two mountains where the skirt overlaps,
;
According to the first result,
In a system where the two resonance characteristics are in a state of mutual interference, due to the phenomenon that both resonance characteristics influence each other, the impedance characteristic of the steep peak shape of fo is changed to a gentle peak shape by the property that fo and fipr attract each other. The fourth is to use the action of changing,
;
According to the first result,
In a system where the two resonance characteristics are in the state of mutual interference, the fo and fipr attract each other due to the phenomenon that both resonance characteristics influence each other, and fill the impedance valley of the band Bio with large undulating impedance characteristics. The fifth is to use the action.
;
The arithmetic mean or root mean square value of the absolute value of the impedance of band Bio or a representative value based on some criterion is used as the representative value of the impedance of band Bio,
Due to the first result,
According to the second, third, fourth and fifth results,
Let K be the magnification of the representative value of the impedance of the band Bim with respect to the DC resistance of the voice coil.
In band Bio
Under the condition that the heat loss of the voice coil is equal to the heat loss of the voice coil when the impedance is considered to be the same as the DC resistance of the voice coil,
Increase the DC resistance of the voice coil by one,
Increase the voice coil voltage by K times,
By doubling the voice coil current, the driving power of the voice coil in the band Bio can be increased by a factor of K without changing the heat loss of the voice coil.
Or
The DC resistance of the voice coil is (1 / K ^ 2) times,
Let the impedance be (1 / K ^ 2) * K = 1 / K times,
By increasing the voltage of the voice coil by 1 and the current of the voice coil by K times,
The driving power of the voice coil in the band Bio can be increased K times without changing the heat loss of the voice coil.
Can be selected,
Furthermore, in band Bio,
Under the condition that the heat loss of the voice coil is constant and the driving power is K times,
Sixth, the DC resistance of the voice coil and the drive power of the voice coil can be selected and determined by design,
;
A vibration type speaker system that enables the vibration of the speaker unit in the vibration axis direction of the voice coil of the speaker unit,
A resonator that does not have a sound radiating surface outside the cabinet of the vibration type speaker system, but has a sound radiating surface inside the cabinet,
Both of which have a structure combining known means,
First,
The second, third, fourth and fifth according to the first result;
The sixth according to the second to fifth results,
By
Where it can be used as a reproduction range without interrupting the super bass band lower than fipr due to the mechanical vibration of the vibrating speaker, and
where the distortion rate in the low frequency band lower than near fo can be reduced and the volume can be significantly improved, and
A speaker system in which the driving power of the voice coil can be increased without increasing the heat loss of the voice coil in the low frequency band.
A resonator having a resonance frequency between fo and fm and a resonator having a closed space on the back of the diaphragm are defined as resonators in the cabinet,
A vibration type speaker system that enables the vibration of the speaker unit in the vibration axis direction of the voice coil of the speaker unit,
Having an in-cabinet resonator instead of the inner PR described in claim 1 in the air chamber of the speaker system cabinet,
First,
The second, third, fourth and fifth according to the first result;
The sixth according to the second to fifth results,
By
Where it can be used as a reproduction range without interrupting the super bass band lower than fipr due to the mechanical vibration of the vibrating speaker, and
where the distortion rate in the low frequency band lower than near fo can be reduced and the volume can be significantly improved, and
A speaker system in which the driving power of the voice coil can be increased without increasing the heat loss of the voice coil in the low frequency band.