Parts for acoustic system and acoustic system

The present invention relates to an acoustic system and its parts used when converting an electric signal into sound, and further to an acoustic system part and an acoustic system for improving the sound quality of a dynamic speaker system.

In the conventional acoustic system, a dynamic speaker unit in which a diaphragm made of paper or resin is driven by an electromagnetic coil is often used because of its economy and handleability. In this method, a voice coil is arranged in a magnetic field generated by a permanent magnet, and an acoustic signal current is passed through the voice coil to vibrate the diaphragm with an electromagnetic force generated thereby to vibrate the air. The dynamic speaker unit is usually a baffle plate, an open back box, a closed box, and a bass reflex type (phase inversion type) in order to improve the reduction of bass due to the sound pressure behind the dynamic speaker unit being out of phase with respect to the sound pressure phase in front of the dynamic speaker unit. ) Used by attaching to a cabinet called a box or the like.

The baffle plate or the open-back box is intended to reduce the influence of the rear sound pressure by the distance until the sound pressure radiated to the rear of the speaker unit wraps around to the front, and to prevent the reduction of the front sound pressure. is there. In addition, the closed type and bass reflex type boxes basically try to prevent the sound pressure from being reduced by shielding the sound pressure radiated to the rear of the speaker unit from the surroundings.

Generally, the bass reproduction capability of a dynamic speaker unit depends on the area of the diaphragm, but the diaphragm area becomes too large to obtain sufficient bass reproduction capability, which is not practical. Therefore, it is common to give resonance characteristics to the low frequency range by the mass of the vibration system such as the diaphragm, that is, the inertia and the elasticity of the edges and dampers that support it, and the electrical impedance of the coil rises near the resonance frequency fo. Therefore, even if the current flowing through the voice coil is small, the vibration system moves relatively large to compensate for the lack of sound pressure in the bass. Figure 1 shows the frequency, sound pressure, and impedance characteristics. The dotted line shows the case where there is no resonance, and the solid line shows the case where there is resonance, and the case where it is mounted in a sufficiently large box is shown.

Furthermore, when this speaker unit is attached to a finite closed box, the bass sound pressure characteristics are adjusted as necessary by the resonance between the box and the speaker unit, which is determined by the air volume inside the box. The alternate long and short dash line shows its characteristics. In this case, sufficient sound pressure can be obtained up to the resonance frequency fr of the box, but when the frequency falls below that, the sound pressure drops sharply. Patent Document 1 attempts to improve the sound pressure characteristics of bass by controlling this resonance.<patcit num="1"><text>JP 2002-101494</text></patcit>

<p>However, these conventional techniques have the following problems.</p><p>First, if the resonance of the system including the unit and the box is too strong, the transient response becomes poor and it becomes difficult to faithfully reproduce the original sound signal. Generally, in a speaker unit with weak resonance, the driving magnetic circuit is set relatively strongly with respect to the inertia (mass) of the vibration system, so that it reacts sensitively to even a small signal. On the contrary, in the speaker unit having strong resonance, the magnetic circuit for driving is set to be relatively weak with respect to the inertia of the vibration system, so that the response to a small signal tends to be slow. For example, when a light car is combined with a strong horsepower engine, acceleration / deceleration is agile, but conversely, when a heavy car is combined with a weak engine, acceleration / deceleration becomes slow.</p><p>Therefore, the response to a weak signal is better when the resonance is weak. However, if the resonance is weak, the amplitude of the vibration system is insufficient near the resonance frequency and the sound pressure is insufficient. Especially in a speaker unit with a small diameter, in order to keep the sound pressure in the space at the same level in the bass and treble, it is necessary to vibrate with a larger amplitude in the bass, which makes it difficult.</p><p>Figure 2 shows a comparison of the sound pressure and impedance characteristics when the speaker unit is attached to the box based on the strength of its resonance. In Fig. 2, the solid line shows the case where the resonance is strong, and the dotted line shows the case where the resonance is weak.</p><p>Next, when the speaker unit is attached to a baffle plate or an open rear box, the degree of bass attenuation changes depending on the path length at which the sound pressure wraps around from the rear to the front of the speaker unit, but since the path length is finite, the bass range It is inevitable that the sound pressure will drop.</p><p>Furthermore, when the speaker unit is attached to a closed box or bass reflex box, if the internal volume of the box is small, the resonance frequency of the system becomes high as described above, and the necessary bass range cannot be obtained.</p><p>In addition, if the sound absorption processing inside the box is insufficient, a standing wave is generated inside at a specific frequency, and unintended vibration is generated in the diaphragm of the speaker due to the back sound pressure due to the standing wave, and the original sound signal can be faithfully reproduced. It becomes difficult. Moreover, it is thought that it is easily affected by the high electrical impedance and weak electrical driving force to the vibration system in the frequency band where resonance occurs. If the electric driving force is strong, including the case where the internal resistance of the amplifier that drives the speaker is made very small, the intended driving of the diaphragm can be sufficiently performed even if it resists the back sound pressure in the resonance frequency band. Because it should be possible.</p><p>Another reason is that general glass wool and other fibrous sound absorbing materials have a low sound absorbing effect at low frequencies, and a sufficient sound absorbing effect cannot be obtained in the resonance frequency band of speakers and boxes. On the contrary, if the sound absorption process is excessive, the resonance is insufficient and the bass is insufficient.</p><p>As described above, in the speaker system using the conventional dynamic speaker, the response to the minute signal is different due to the influence of the resonance between the speaker unit and the box, and the speaker unit diaphragm is used to solve the problem of faithful reproduction of the original sound signal. Due to the box resonance on the back and the influence of the back sound pressure due to the standing wave, vibrations that are not in the original sound occur and the diaphragm cannot vibrate faithfully to the original sound. In this case, there was a contradictory problem that the sound pressure in the low frequency range was insufficient.</p><p>On the other hand, there is also a speaker system called a horn type speaker system that does not actively utilize resonance. This vibrates a lightweight diaphragm with a voice coil, and guides the air flow generated by the vibration to a suitable narrow space that acts as an acoustic metamorphic device in front of the diaphragm, and in front of it is a horn with large acoustic resistance. Is formed to obtain sufficient sound pressure. In this case, the degree of resonance is made as small as possible in order to widen the reproduction frequency band. Therefore, this speaker system is generally known as a system having high reproduction clarity and good transient response.</p><p>However, in order to reproduce sufficient bass with this system, it is necessary to make the opening of the horn considerably large, and it is difficult to make it large enough to be easily used in ordinary life. Therefore, an object of the present invention is to simplify an acoustic system that is large enough to be used in ordinary life, has a clear transient response, can obtain a reproduced sound faithful to a signal, and can sufficiently reproduce a bass. The purpose is to obtain it at low cost with a simple structure.</p>

<p>Therefore, claim 1 is a speaker system consisting of a speaker unit and a cabinet in which an air layer is partitioned between a front portion and a back portion of the unit, which is composed of a breathable acoustic resistance material, and the vicinity of the back surface of the speaker unit is the acoustic resistance material. By covering the speaker unit so that there is no other air passage, a first air chamber is formed on the back surface of the diaphragm of the speaker unit so as to partition the air layer on the side farther from the diaphragm of the speaker unit from the first air chamber. It provides parts for sound systems that are characterized by being placed in the speaker.</p><p>Further, in claim 2, in a speaker system consisting of a speaker unit and a box forming an air chamber on the back side of the unit, a breathable acoustic resistance material is used near the back surface of the unit, and an air passage other than the acoustic resistance material is used. It is characterized by including a speaker system having a structure in which the inside of the box is divided into a first air chamber on the diaphragm side of the speaker unit and a second air chamber on the side farther from the diaphragm of the speaker unit. It provided a sound system.</p><p>Further, claim 3 provides an acoustic system using the parts for the acoustic system of claim 1 or an acoustic system of claim 2 provided with a bass amplifier circuit.</p>

<p>It is generally known that a breathable porous material has acoustic resistance. It is believed that this is due to friction between air particles when the air flow passes through a large number of small holes in a substance.</p><p>The inventor first considered in claim 1 to cover the vicinity of the rear of the diaphragm of the cone-shaped dynamic speaker unit with this breathable porous material to reduce the degree of resonance of the unit. In this way, the volume of the first air chamber on the back surface of the diaphragm of the speaker unit is small, and the air flow to and from the outside of the first air chamber due to the density of air generated in the air chamber on the rear side due to the vibration of the speaker diaphragm Since all exchanges are performed only through the small holes of the acoustic resistance material, the acoustic load (resistance) of the diaphragm increases, excessive vibration due to resonance with respect to the electric drive signal of the diaphragm of the speaker unit is suppressed, and the resonance phenomenon. Has the effect of reducing.</p><p>This approximates the relationship between the solid line and the dotted line in FIG. 2, and the solid line corresponds to the case where there is no acoustic resistance substance according to claim 1, and the dotted line corresponds to the case where there is an acoustic resistance substance.</p><p>By using the acoustic resistance material of claim 1, the extra vibration due to the resonance of the diaphragm of the speaker unit is suppressed and the fidelity of the diaphragm vibration to the signal is increased, so that the transient response is improved and the sound quality is clear. become. In addition, since it is moderately breathable, it does not completely block the air flow, so the vibration of the diaphragm at low frequencies is not suppressed at all, and the diaphragm drives the voice coil even at low frequencies. It can vibrate moderately by the force, and when the air flow comes out from the acoustic resistance substance to the outer air layer, the sound pressure is correspondingly weakened. It is considered that this is because the friction of air particles caused by the air flow passing through the small holes in the acoustic resistance substance and the energy consumption due to the vibration of the acoustic resistance substance itself occur.</p><p>Therefore, in this case, the sound pressure of the opposite phase on the back surface of the diaphragm is weakened in the low frequency region as compared with the case where the speaker unit is electrically driven in a bare state, so that the sound pressure returns in front of the speaker unit. Can be increased. That is, the invention of claim 1 can provide a part for an acoustic system having these effects.</p><p>Next, in the invention of claim 2, in the speaker system including the speaker unit and the box forming the air chamber on the back side of the unit, the vicinity of the back side of the unit is a breathable acoustic resistance material other than the acoustic resistance material. Include a speaker system with a structure that covers the inside of the box so that there is no air passage and partitions the inside of the box into a first air chamber on the diaphragm side of the speaker unit and a second air chamber on the side farther from the diaphragm of the speaker unit. Provided a characteristic sound system.</p><p>According to this structure, the speaker unit can reduce the degree of resonance as in claim 1, and the sound pressure on the back surface of the diaphragm due to the resonance of the second air chamber in the box is the vibration of the speaker unit through the acoustic resistance material. It will reach the board, and its effect can be reduced by the presence of acoustically resistant material.</p><p>Therefore, unlike the alternate long and short dash line from the solid line in Fig. 1, the resonance frequency is less likely to be dragged by the resonance frequency of the second air chamber in the box and become higher, but rather the characteristics of the dotted line can be approached from the solid line in Fig. 2. .. Furthermore, the influence of the back sound pressure on the diaphragm due to the standing wave in the second air chamber of the box can be weakened by the presence of the acoustic resistance substance, and the vibration bias other than the vibration of the diaphragm due to the drive signal to the voice coil can be weakened. Since it is possible to weaken the diaphragm, the diaphragm vibrates faithfully to the drive signal.</p><p>As described above, according to the invention of claim 2, when the speaker unit is attached to the box, it is possible to provide a speaker system in which the diaphragm vibrates faithfully to the drive signal applied to the voice coil of the speaker unit. Therefore, it is possible to provide an acoustic system in which the transient response of the reproduced sound is increased and the clarity of the reproduced sound is improved.</p><p>Further, the invention of claim 3 provides an acoustic system using the parts for the acoustic system of claim 1 or an acoustic system of claim 2 provided with a bass amplifier circuit. As described in the effects of the inventions of claim 1 and claim 2, by using these sound system parts and sound systems, the vibration of the diaphragm of the speaker unit has the effect of vibrating more faithfully to the source signal. The sound pressure of the bass is lower than that of the source signal as shown by the dotted line in Fig. 2, and it is hard to say that it is faithful including the sound pressure.</p><p>Therefore, by adding a bass enhancement circuit that compensates for the decrease in bass sound pressure to the system, it is possible to obtain an acoustic system that can reproduce the original sound almost faithfully.</p><p>FIG. 3 is a diagram showing the situation. In the figure, the solid line shows the frequency sound pressure characteristics of the sound system parts of claim 1 or the sound system of claim 2, but the sound pressure decreases as the frequency decreases. Therefore, by adding an electric circuit having a low frequency amplification characteristic such as a dotted line to the system, the frequency vs. sound pressure characteristic can be improved like a one-dot chain line.</p><p>In this case, the vibration of the vibrating plate of the speaker unit of claims 1 and 2 is faithful to the source signal, and the transient response is also good and clear. Therefore, by amplifying the bass of the source signal in advance, the bass can be reduced. A faithful reproduced sound with good transient response can be obtained while ensuring sound pressure. Further, the means of claims 1 to 3 are very simple and low in cost because it is only necessary to add an acoustic resistance substance or a bass amplifier circuit to the conventional structure.</p>

FIG. 4 is an example of claim 1 of the present invention. In the figure, 101 is a ring-shaped acoustic resistance material made of a breathable porous material, and is formed of a sponge-like material such as urethane foam. Further, 102 is a plate-shaped acoustic resistance substance formed of the same acoustic resistance substance as 101. The surfaces 1012 and 102 of 101 are adhered with an adhesive or double-sided tape as shown in 1 of FIG. 5, and a recess is formed on the inner surface thereof so as to wrap the back shape of the speaker unit. Further, the acoustic resistance substance 1 of FIG. 5 may not be a combination of the two shapes as shown in FIG. 4, but may be integrally formed in advance by a mold or the like.

The acoustic resistance substance 1 in FIG. 5 is used as shown in FIG. In FIG. 6, 2 is a speaker unit and 3 is a baffle plate. The speaker unit is attached to the opening 301 of the baffle plate 3 from the front surface with screws or the like. The front portion 1011 of the acoustic resistance substance 1 is attached to the back surface of the baffle plate 3 with an adhesive, double-sided tape, or the like. Reference numeral 4 denotes a lead wire for electrically pulling out the voice coil terminal of the speaker unit, which communicates from the inside to the outside of the acoustic resistance substance 1 without impairing the confidentiality.

Due to this structure, a small space (first air chamber) 5 through which air cannot pass other than the acoustic resistance substance 1 is created on the back side of the diaphragm 201 of the speaker unit 2, and the resonance characteristic of the speaker unit 2 is the above-mentioned claim. As described in the effect of the invention of 1, the solid line in FIG. 2 can be changed to something like a dotted line. Further, in the first air chamber 5, since the wall surface of the first air chamber is an acoustic resistance substance having small holes, it has a sound absorbing effect, and if it is an elastic substance such as urethane foam, the wall surface itself is Since it is soft, there is almost no standing wave. The degree of characteristic change from the solid line to the dotted line in Fig. 2 can be adjusted by adjusting the degree of foaming and thickness of the acoustic resistance substance 1.

FIG. 7 is a second embodiment of the invention of claim 1, in which an acoustic resistance substance 1 is adhered to a ring-shaped frame 6 fixed between a baffle plate 3 and a speaker unit 2, and FIG. 8 is a ring-shaped frame. An example in which the frame 6 is fixed to the back surface of the baffle plate 3, FIG. 9 is an example in which an acoustic resistance material is adhered so as to cover the opening 202 of the frame of the speaker unit 2, and both are the back surfaces of the diaphragm 201 of the speaker unit 2. The first air chamber 5 or 7 is formed in.

FIG. 10 is an embodiment of the invention of claim 2, which is a cross-sectional view of a speaker system in which a speaker unit 2 and an acoustic resistance substance 1 are attached to a closed box 8. In FIG. 10, the speaker unit 2, the baffle portion 801 and the acoustic resistance substance 1 and the first air chamber 5 are the same as those shown in FIG. 6 above. In FIG. 10, 9 is the second air chamber and 10 is the sound absorbing material.

By partitioning the inside of the box 8 with the acoustic resistance substance 1 into the first air chamber 5 and the second air chamber 9 in this way, an acoustic system capable of obtaining the effect as described in the effect of the invention of claim 2 described above can be obtained. Obtainable.

FIG. 11 shows an example in which the back open type is used for the box, and FIG. 12 shows an example in which a bass reflex (phase inversion type) is used for the box. Although 11 in FIG. 11 and 9 in FIG. 12 correspond to the second air chamber, the acoustic resistance substance 1 reduces the vibration effect of the resonance and the standing wave on the diaphragm of the speaker unit 2 in any case. This is the same as in FIG.

In the embodiment of FIG. 12, reference numeral 12 denotes a resonance port called a duct, but its influence is slightly different in frequency from the resonance of the second air chamber, and the second air chamber affects the diaphragm of the speaker unit. It has nothing to do with the influence of.

FIG. 13 is a first embodiment of the invention shown in claim 3. In FIG. 13, 13 is an electric signal of a sound source, 14 is an amplifier, for example, a preamplifier, 15 is a bass amplifier circuit, 16 is a power amplifier for driving a speaker, and 17 is a speaker system similar to that in FIG.

As the bass amplifier circuit 15 in FIG. 13, a circuit using CR can be considered as shown in FIG. 14, for example. In the circuit of FIG. 14, R1 and C1 form a treble attenuation circuit having the first cutoff characteristic, and R2 and C1 form a bass enhancement circuit having the second cutoff characteristic, and the attenuation characteristics are shown in FIG. As described above, it has a characteristic of attenuating at 6 dB / oct from the first cutoff frequency fcf to the second cutoff frequency fcH. If necessary, an amplifier (AMP) may be provided as shown in FIG.

In the acoustic system to which the bass amplifier circuit 15 is added as shown in FIG. 13, the frequency-sound pressure characteristics (solid line in FIG. 3) of the speaker system in 17 can be comprehensively selected by appropriately selecting the fHC in FIG. It is possible to obtain improved characteristics such as the alternate long and short dash line.

It is also possible to use such a bass amplifier circuit in two stages as shown in FIG. Generally, the frequency sound pressure characteristics of the speaker system shown in FIG. 10 are as shown in FIG. That is, the sound pressure of the bass starts to decrease from the bass curve point fc1 of the speaker unit, and the frequency further decreases, and the sound pressure further decreases from the bass curve point fc2 due to the influence of the box volume.

Therefore, by using a combination of two bass amplifier circuits with different characteristics as shown in Fig. 16, it is possible to eliminate the lack of sound pressure in the bass below the bass curve point fc2. Furthermore, by using the bass amplifier circuit of FIGS. 13 and 16, the effect of compensating the frequency-phase characteristics of the speaker system 17 of FIGS. 13 and 16 can be expected to some extent.

That is, it is known that the frequency-phase characteristics of the speaker system are generally as shown in FIG. That is, as the frequency decreases from the bass curve point fc1 of the speaker unit, the phase gradually advances with respect to the signal of the sound source, and the phase advance of about 90 degrees at the resonance frequency fr as a system. As the frequency further decreases, the sound pressure decreases and the phase advance increases due to the limitation of the capacity of the box, resulting in a phase advance of up to 180 degrees.

However, the frequency-phase characteristics of the bass amplifier circuit in Fig. 14 can have a phase delay of up to 90 degrees in the vicinity of fr by selecting fcf and ffc with an appropriate dissociation as shown in Fig. 19. The phase characteristic in fr can be corrected. Moreover, when the bass amplifier circuit is used in two stages as shown in FIG. 16, another phase delay is added, so that the phase shift near the maximum of 180 degrees in FIG. 18 can be compensated. Figure 20 shows the phase compensation characteristics in the case of two stages.

According to the present invention, in an audio device that requires pure and faithful reproduced sound for a sound source signal, not only a speaker system that covers the entire band with one speaker, but also a 2-way, 3-way, or multi-amplifier system, etc. In addition to being applicable to pure audio systems, it can also be applied to audio systems that require high-quality sound in home appliances that use dynamic speakers, such as audio visuals, TVs, personal computers, and portable radio tape recorders.

<figref num="1">Diagram showing frequency sound pressure and frequency impedance characteristics of a dynamic speaker system</figref><figref num="2">Part 2 of the figure showing the frequency sound pressure and frequency impedance characteristics of the dynamic speaker system</figref><figref num="3">The figure which shows the improvement of the frequency sound pressure characteristic of a dynamic type speaker system</figref><figref num="4">Diagram of the configuration of parts for an acoustic system according to claim 1 of the present invention.</figref><figref num="5">The figure of the part for an acoustic system according to claim 1 of this invention.</figref><figref num="6">Diagram of a usage example of a part for an acoustic system according to claim 1 of the present invention.</figref><figref num="7">The figure of another embodiment of the part for an acoustic system according to claim 1 of this invention.</figref><figref num="8">The figure of another embodiment of the part for an acoustic system according to claim 1 of this invention.</figref><figref num="9">The figure of another embodiment of the part for an acoustic system according to claim 1 of this invention.</figref><figref num="10">Diagram of an acoustic system according to claim 2 of the present invention</figref><figref num="11">Figure of another embodiment of the acoustic system according to claim 2 of the present invention.</figref><figref num="12">Figure of another embodiment of the acoustic system according to claim 2 of the present invention.</figref><figref num="13">Diagram of an acoustic system according to claim 2 of the present invention</figref><figref num="14">Diagram of an example of a bass amplifier circuit</figref><figref num="15">Diagram of circuit characteristics in FIG.</figref><figref num="16">Figure of another embodiment of the acoustic system according to claim 2 of the present invention.</figref><figref num="17">Diagram of speaker system characteristics</figref><figref num="18">Diagram of speaker system characteristics</figref><figref num="19">Diagram of phase characteristics of bass amplifier circuit</figref><figref num="20">Diagram of phase characteristics of bass amplifier circuit</figref>

Code description

1 Sound system parts 2 Speaker unit 3 Baffle plate 4 Lead wire 5 First air chamber 6 Frame 7 First air chamber 8 Box 9 No. Second air chamber 10 ... Sound absorbing material 11 ... Second air chamber 12 ... Second air chamber 13 ... Signal source 14 ... Amplifier 15 ... Bass amplifier circuit 16 ... Amplifier 17 ... Speaker system