JP3598014B2 - Low frequency reproduction speaker device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a low-frequency sound reproduction speaker device capable of obtaining high low-frequency reproduction capability despite being a small cabinet.
[0002]
[Prior art]
In general, regarding the low-frequency reproduction of a speaker, there is an inverse relationship between the volume V in the cabinet, the low-frequency reproduction limit frequency fc, and the efficiency μ, and it is a principle that a small cabinet reproduces to a low frequency without lowering the efficiency. Is known to be very difficult.
[0003]
In addition, the concept itself has long existed that if the inside volume of the cabinet could be equivalently increased, it would be possible to escape from this restriction and improve the low-frequency reproduction capability. However, the reality is that there was no good way to implement this.
[0004]
Here, conventional technologies that have been proposed in the past to realize this concept will be described. This prior art is described in U.S. Pat. No. 2,810,021 (LOW FREQUENCY LOUDSPAKER, Patented Oct. 15, 1957). FIG. 9 shows the structure of this conventional bass reproduction speaker device.
[0005]
In FIG. 9, reference numeral 51 denotes a speaker unit, which includes a field part 51a, a frame 51b, a voice coil 51c, a damper 51d, an edge 51e, and a diaphragm 51f. Reference numeral 52 denotes a closed cabinet to which a speaker unit 51 is attached.
[0006]
58 is a support and is fixed to the cabinet 52. A spring 59b is arranged on the inner peripheral portion of the support body 58, and presses the lever 59c in the inner peripheral direction. The lever 59c is supported by the fulcrum receiving groove 59d. On the other hand, a rod 59a is attached to the upper part of the voice coil 51c of the speaker unit 51, and a toggle pin 59f is fitted between a receiving groove 59g of the rod 59a and a receiving groove 59e of the lever 59c.
[0007]
In addition, a movable electric contact 60a that is flexibly supported by a spring 60c is provided above the rod 59a. The fixed electric contact 60b is arranged so as to sandwich the movable electric contact 60a. An exhaust pump 60d and an intake pump 60e are connected to these electrical contacts.
[0008]
The operation of the conventional low-frequency sound reproduction speaker device configured as described above is as follows. Since the spring 59b pushes the toggle pin 59f in the inner circumferential direction through the lever 59c, when the voice coil 51c is displaced and the toggle pin 59f is out of the equilibrium state, the toggle pin 59f pushes the rod 59a so as to further fall in the displacement direction. become.
[0009]
When the vibration system such as the voice coil 51c and the diaphragm 51f is displaced, the stiffness of the damper 51d and the edge 51e, that is, the stiffness of the support system, and the stiffness of the air in the cabinet 52 work to return the vibration system to the center position. However, the force generated by the toggle mechanisms 59a to 59g is in the opposite direction, and is intended to push the vibration system of the speaker unit 51 further in the direction of displacement.
[0010]
That is, the above-mentioned toggle mechanisms 59a to 59g give negative stiffness to the vibration system of the speaker unit 51, and cancel and reduce the stiffness caused by the support system of the speaker unit 51 and the air in the cabinet 52. , The inner volume of the cabinet 52 is equivalently increased. Thus, the low frequency reproduction capability is improved. It should be noted that the principle of equivalently increasing the internal volume of the cabinet due to negative stiffness and improving the low frequency reproduction capability will be described in detail in the description of the present invention.
[0011]
If the negative stiffness is larger than the stiffness of the support system of the speaker unit 51, the vibration system of the speaker unit 51 cannot continue to stay at the original displacement center position (a small amount of air leaks from the cabinet 52 or the like). ), It is biased in one of the displacement directions. The electric contacts 60a and 60b and the pumps 60d and 60e are for correcting this.
[0012]
That is, for example, when the vibration system of the speaker unit 51 is biased forward, the movable electrical contact 60a contacts the upper side of the fixed electrical contact 60b, and the exhaust pump 60d operates. Then, the air in the cabinet 52 is exhausted, and the vibration system of the speaker unit 51 is returned to the original displacement center position. Conversely, when the vibration system is biased backward, the movable electric contact 60a comes into contact with the lower side of the fixed electric contact 60b, and the intake pump 60e operates. Then, air flows into the cabinet 52 and the vibration system of the speaker unit 51 is pushed back to the original displacement center position.
[0013]
Therefore, even when the negative stiffness is large, the bias of the vibration system of the speaker unit 51 in the displacement direction is corrected.
[0014]
[Problems to be solved by the invention]
However, in the above-mentioned conventional configuration, since the negative stiffness generating means is a mechanical toggle mechanism using 59a to 59g, mechanical fatigue occurs in the spring 59b (there is a danger of breakage if the large amplitude operation is continued for a long time). ), There is a problem that there is no reliability, and abnormal noise and noise are generated from the contact portion between the toggle pin 59g and the lever 59c. Another problem is that the apparatus is complicated because of the large number of components.
[0015]
Furthermore, when the negative stiffness is large, the pumps 60d and 60e are required to correct the deviation in the displacement direction of the diaphragm, so that the apparatus becomes more complicated and large-scale, and noise is generated from the pumps 60d and 60e. There was also a problem, such as.
[0016]
In other words, although there was a concept of improving the low-frequency reproduction capability by equivalently increasing the internal volume of the cabinet, the low-frequency reproduction speaker device according to the prior art had many problems and was not practical at all.
[0017]
SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides a low-frequency sound reproduction speaker device that is highly reliable, free of noise and the like, is simple and practical, and has an equivalently large cabinet volume. With the goal.
[0018]
[Means for Solving the Problems]
To achieve the above object, the present invention has the following configuration.
[0019]
That is, the bass reproduction speaker device of the present invention includes a speaker unit, a cabinet accommodating the speaker unit, a movable magnet that moves together with a vibration system of the speaker unit, and a fixed magnet. The speaker unit is configured to generate negative stiffness with respect to the vibration system. The fixed magnet is formed in a ring shape, the movable magnet is arranged coaxially at the center position in the thickness direction on the inner peripheral side of the fixed magnet, and an electric signal is detected by detecting a bias in a displacement direction of a vibration system of the speaker unit. A detection unit that generates the signal, and feeds back the electric signal from the detection unit to a power amplifier that drives the speaker unit to correct a bias in a displacement direction of a vibration system of the speaker unit. Equipped with means for holding the vibration system near the center position in the displacement direction It is characterized by the following. According to such a configuration, it is highly reliable, free of noise and the like, simple and practical, In addition, the mechanism for generating negative stiffness can be simplified, and the capacity inside the cabinet is equivalently extremely large. A bass reproduction speaker device can be realized.
[0021]
In the above configuration, it is preferable that the movable magnet and the fixed magnet are configured so that a generated negative stiffness is reduced before the displacement of the vibration system of the speaker unit reaches the maximum displacement. According to such a preferred configuration, it is possible to realize a low-frequency sound reproduction speaker device that is resistant to excessive input.
[0023]
Here, it is preferable that the detecting means for detecting the bias in the displacement direction of the vibration system of the speaker unit includes a Hall element. According to such a preferred configuration, it is possible to simplify the means for detecting the bias in the displacement direction of the vibration system of the speaker unit.
[0025]
In the above configuration, it is preferable that the fixed magnet is an electromagnet. According to such a preferred configuration, the low-frequency characteristics can be varied.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a bass reproduction speaker device of the present invention will be described based on specific embodiments.
[0027]
(Embodiment 1)
FIG. 1 shows the structure of the bass reproduction speaker device of the first embodiment. In FIG. 1, a speaker unit 1 including a field part 1 a, a frame 1 b, a voice coil 1 c, a damper 1 d, an edge 1 e, a diaphragm 1 f, and a dust cap 1 g is attached to a cabinet 2. The ring-shaped movable magnet 3 is attached to the voice coil 1c, and moves together with the voice coil 1c, the diaphragm 1f, and the dust cap 1g, that is, the vibration system.
[0028]
A ring-shaped fixed magnet 4 is attached to the frame 1b. The two magnets 3 and 4 are coaxially arranged so that the movable magnet 3 is located at the center position in the thickness direction (the displacement direction of the vibration system) inside the fixed magnet 4 when the vibration system is at the center position in the displacement direction. ing. The movable magnet 3 and the fixed magnet 4 are magnetized to have the same polarity in the thickness direction and repel each other. Therefore, the movable magnet 3 and the fixed magnet 4 give a force for the vibration system to escape from the center position, that is, a negative stiffness to the vibration system of the speaker unit 1.
[0029]
Here, the materials and dimensions of the components of the bass reproduction speaker device will be specifically described.
[0030]
The diameter of the speaker unit 1 is 18 cm. The field portion 1a uses a ferrite magnet having a diameter of 70 mm. The frame 1b has a diameter of 18 cm and is made of an iron plate. The diameter (nominal diameter) of the voice coil 1c is 19 mm (the actual outer diameter of the voice coil bobbin is about 20 mm). The material of the edge 1e is urethane foam and has an up-roll shape. The diaphragm 1f is a cone made of paper. The material of the dust cap 1g is paper.
[0031]
The cabinet 2 is of a closed type and has a small internal volume of 10 liters.
[0032]
The dimensions of the movable magnet 3 are 28 mm in outer diameter, 20 mm in inner diameter, and 2.5 mm in thickness, and the material is neodymium having a magnetic energy product of 30 M · G · Oe (megagauss Oersted). The dimensions of the fixed magnet 4 are 70 mm in outer diameter, 32 mm in inner diameter, and 15 mm in thickness, and the material is ferrite.
[0033]
With the above-described configuration, negative stiffness can be generated without using any mechanical means and without any contact portions, and therefore, there is no occurrence of mechanical fatigue, noise, and the like, and the reliability is excellent. Further, since only two magnets 3 and 4 are required to generate negative stiffness, the structure is simple.
[0034]
With regard to the effect of equivalently increasing the internal volume of the cabinet and the improvement of the low-frequency reproduction capability, the negative stiffness increases the internal volume of the cabinet 2 approximately twice in the present embodiment, and reduces the minimum resonance frequency, that is, the low resonance frequency. The range reproduction limit frequency could be extended from 96 Hz to 81 Hz.
[0035]
Hereinafter, the principle of equivalently increasing the internal volume of the cabinet by negative stiffness and improving the low-frequency reproduction capability will be considered and described.
[0036]
Assuming that the effective vibration mass of the speaker unit is M and the lowest resonance frequency in a single free air state is f0, the stiffness Ks of the support system (damper or edge) of the speaker unit is
[0037]
(Equation 1)
Ks = M × (2πf0) ² ... Formula ▲ 1 ▼
[0038]
It is. Assuming that the effective vibration radius of the speaker unit is a, the air sound velocity is c, the air density is ρ, and the volume of the cabinet is V, the stiffness Kc that air in the cabinet gives to the speaker unit vibration system is:
[0039]
(Equation 2)
Kc = ρc ² (Πa) ² / V… Equation ▲ 2 ▼
[0040]
It is. When the speaker unit is attached to the cabinet, a stiffness of Ks + Kc acts on the speaker unit vibration system. Assuming that the lowest resonance frequency at this time is f1,
[0041]
(Equation 3)
f1 = (Ks + Kc) ^1/2 / 2πM ^1/2 … ▲ 3 ▼
[0042]
It is.
[0043]
Here, the magnitude of the negative stiffness is assumed to be Kn. Then, the stiffness acting on the vibration system of the speaker unit becomes Ks + Kc-Kn, which corresponds to the stiffness of the air in the cabinet changing from Kc to Kc-Kn. Since the stiffness of the air in the cabinet is inversely proportional to the internal volume according to the equation (2), this is equivalent to an increase in the internal volume of the cabinet from 1 / Kc to 1 / (Kc-Kn).
[0044]
FIG. 2 shows the relationship between the stiffness force (dashed line), the negative stiffness force (dash-dot line), and the total stiffness force (solid line) acting on the vibration system of the speaker unit in a state where the speaker unit is mounted on the cabinet. The stiffness is simply like a spring constant, and corresponds to the slope of each displacement-force curve in FIG. In other words, the smaller the slope of the curve, the smaller the stiffness and the easier the vibration system is to move.
[0045]
Due to the negative stiffness, the lowest resonance frequency of the speaker unit mounted on the cabinet is
[0046]
(Equation 4)
f1 = (Ks + Kc-Kn) ^1/2 / 2πM ^1/2 … Equation ▲ 4 ▼
[0047]
Therefore, the lowest resonance frequency is {(Ks + Kc−Kn) / (Ks + Kc)}. ^1/2 That is, the low-frequency reproduction limit frequency is extended, and the low-frequency reproduction capability is improved.
[0048]
If the technique of the negative stiffness is not used, in order to lower the lowest resonance frequency, the effective vibration mass must be increased or the effective vibration area must be reduced, so that the efficiency is reduced. On the other hand, if negative stiffness is used, the lowest resonance frequency can be lowered without such a thing, so that the low range can be extended without lowering the efficiency.
[0049]
If the magnitude Kn of the negative stiffness is made very large, Kn> Ks. In this case, in the state of the speaker unit which is not attached to the cabinet, the vibration system cannot stand still at the center position. Immediately biased to one side. To put it simply, the support system of the speaker unit loses negative stiffness. Since air leakage cannot be completely eliminated even when the speaker unit is mounted on a cabinet, the vibration system of the speaker unit gradually deviates from the center position and is deviated.
[0050]
Therefore, when the negative stiffness Kn is larger than the support stiffness Ks, a means for correcting the bias of the vibration system is required. A solution to this will be described in another embodiment of the present invention.
[0051]
In accordance with the principle described above, the effect of equivalently increasing the internal volume of the cabinet and improving the low-frequency reproduction capability according to the present embodiment will be described.
[0052]
In the present embodiment, the lowest resonance frequency (with the movable magnet 3) of the speaker unit 1 is 60 Hz, and the effective vibration mass is 15 g. The effective vibration radius is 70 mm. That is, the stiffness Ks of the support system of the speaker unit is Ks = 2130 (N / m) according to the equation (1). The stiffness Kc given by the air in the cabinet 2 is Kc = 3290 (N / m) according to the equation (2). That is, Ks + Kc = 5420 (N / m). Then, the minimum resonance frequency f1 of the speaker unit 1 in a state where the speaker unit 1 is attached to the cabinet 2 and there is no fixed magnet 4 is f1 = 96 Hz from Equation (3) (the same as the actually measured value).
[0053]
When the negative stiffness Kn is given, the minimum resonance frequency f1 becomes 81 Hz. However, Ks + Kc−Kn = 3820 (N / m) calculated from the equation (4), so that Kn = 5420-3820 = 1600 (N / m) m). Therefore, this corresponds to a decrease in the stiffness of the air in the cabinet 2 from Kc = 3290 (N / m) to Kc−Kn = 3290-1600 = 1690 (N / m). Since the stiffness of the air in the cabinet is inversely proportional to the internal volume, this is equivalent to increasing the internal volume of the cabinet 2 at a ratio of 1/3290 to 1/1690. That is, in the present embodiment, it can be said that the internal volume of the cabinet 2 is equivalently approximately doubled.
[0054]
As described above, according to the first embodiment, it is possible to realize a low-pitched sound reproducing device that is excellent in reliability, practical, simple, and has excellent low-frequency reproduction capability.
[0055]
In the first embodiment, the movable magnet 3 and the fixed magnet 4 are configured as described above, but various other configurations are possible. 3 and 4 show a part of another configuration example.
[0056]
In the speaker unit 11 shown in FIG. 3, two disk-shaped fixed magnets 14a and 14b are provided at positions symmetrical in the thickness direction on the inner peripheral side of the ring-shaped movable magnet 13 attached to the voice coil 11c (that is, in the thickness direction). The fixed magnets 14a and 14b are arranged at positions that are equidistant from the movable magnet 13. The fixed magnets 14a and 14b are attached to the upper part of the field part 11a by a support 11h. The magnets 13, 14a, 14b are magnetized in the thickness direction with the same polarity. The fixed magnets 14a and 14b generate an attractive force in a direction of pulling the movable magnet 13 from the center position, thereby generating negative stiffness.
[0057]
In the speaker unit 21 of FIG. 4, a ring-shaped fixed magnet 24 is arranged at the center of the inner periphery of a ring-shaped movable magnet 23 attached to the voice coil 21c. The fixed magnet 24 is attached to the upper part of the field part 21a by a support 21h. In this example, the movable magnet 23 and the fixed magnet 24 are magnetized in radially opposite directions. The movable magnet 23 and the fixed magnet 24 generate forces repelling each other, and generate negative stiffness.
[0058]
By arranging the fixed magnet on the inner peripheral side of the movable magnet as described above, there is an advantage that the number of parts used can be reduced. On the other hand, as already described, the configuration shown in FIG. 1 is the simplest because only two magnets are required. In addition, since the size of the fixed magnet 4 can be increased, a very large negative stiffness can be obtained. There is also a merit that it can be easily obtained. Another characteristic is that the generated negative stiffness displacement-force characteristic curve is relatively linear.
[0059]
Although the movable magnet 3 and the fixed magnet 4 are magnetized in the thickness direction in FIG. 1 of the first embodiment, they may be magnetized in the radial direction as shown in FIG. Further, an iron plate or a yoke may be attached to the fixed magnet 4 or the movable magnet 3. In the first embodiment, the movable magnet 3 and the fixed magnet 4 are formed in a circular ring shape, but may be formed in a disk shape, a rectangular shape, a square ring, or other shapes.
[0060]
Further, in the first embodiment, the movable magnet 3 is attached to the voice coil 1c. However, the movable magnet 3 may be attached to another part of the vibration system of the speaker unit 1. Further, an elastic body or the like may be interposed between the movable magnet 3 and the vibration system of the speaker unit 1, and the movable magnet 3 and the vibration system may move together in a low frequency range.
[0061]
Further, in the first embodiment, the speaker unit 1 is a normal electrodynamic type, but the present invention can be applied to other electroacoustic conversion type speaker units such as a motor drive type and an electromagnetic type.
[0062]
Although the cabinet 2 is a closed type in the first embodiment, other types of cabinets such as a Kelton type and a bass reflex type may be used.
[0063]
In addition, it goes without saying that the present invention is not limited to the examples described above.
[0064]
(Embodiment 2)
The configuration of the bass reproduction speaker device according to the second embodiment of the present invention is exactly the same as that of the first embodiment described with reference to FIG. The same applies to the effect of equivalently increasing the volume in the cabinet and improving the low frequency reproduction capability. The only differences are the dimensions of the fixed magnet and the resulting negative stiffness displacement-force characteristic curve. Therefore, a detailed description other than the fixed magnet 4 and the displacement-force characteristic curve of the negative stiffness is omitted here.
[0065]
In the second embodiment, the fixed magnet 4 has an outer diameter of 65 mm, an inner diameter of 32 mm, and a thickness of 10 mm, and is made of ferrite.
[0066]
FIG. 5 shows a negative stiffness displacement-force characteristic curve and the like in the second embodiment. The displacement-force characteristic curve of the stiffness force applied to the vibration system of the speaker unit 1 attached to the cabinet 2, that is, the displacement-force characteristic curve of the sum of the stiffness of the support system of the speaker unit 1 and the stiffness of the air in the cabinet 2 is indicated by a broken line in FIG. Is shown. The maximum amplitude of the speaker unit 1 is about ± 8 mm, and when the displacement is close to 8 mm, the support system is tight, and the slope of the displacement-force characteristic curve is large.
[0067]
A dashed line in the figure indicates a displacement-force characteristic curve of the generated negative stiffness. The slope of the linear portion of this curve is 8 (N) / 5 (mm), that is, 1600 (N / m), which is the same as the value calculated and described in the first embodiment. The outer diameter of the fixed magnet 4 was smaller than that of the first embodiment, but the generated negative stiffness was the same. This is a result of experiments, but in this configuration, the negative stiffness that occurs is larger as the outer diameter of the fixed magnet is larger, but the negative stiffness that occurs when the thickness is smaller tends to increase. It is due to being.
[0068]
In the figure, the displacement-force characteristic curve of the negative stiffness indicated by the alternate long and short dash line has a peak around ± 5 mm, and the negative stiffness force generated when the peak is exceeded is reduced. This ± 5 mm corresponds to exactly half of the thickness of the fixed magnet 4, and the displacement of this peak is determined almost in proportion to the thickness of the fixed magnet 4.
[0069]
The solid line in the drawing shows a displacement-force characteristic curve of the stiffness acting on the vibration system of the speaker unit 1 when negative stiffness is generated (that is, in total). A curve in which the stiffness increases when the distance exceeds about ± 5 mm is obtained. In other words, the movable magnet 3 and the fixed magnet 4 are configured so that the generated negative stiffness is reduced before the displacement of the vibration system of the speaker unit 1 reaches the maximum displacement. The stiffness can be increased from a displacement area smaller than the displacement.
[0070]
Therefore, since the vibration is applied to the vibration system of the speaker unit 1 before the maximum amplitude is reached, the support system does not generate a sharp tension when an excessive input is applied to the speaker unit 1 and is durable against the excessive input. A low-pitched sound reproduction speaker device with high reliability can be realized.
[0071]
It goes without saying that the present invention is not limited to the above-described example.
[0072]
(Embodiment 3)
The configuration of the bass reproduction speaker device according to Embodiment 3 of the present invention will be described with reference to FIG.
[0073]
The speaker unit 31 (31a to 31g) and the cabinet 32 according to the third embodiment correspond to the speaker unit 1 (1a to 1g) and the cabinet 2 according to the first embodiment described with reference to FIG. 1, respectively. Therefore, a detailed description thereof will be omitted here.
[0074]
In the third embodiment, the movable magnet 33 is a strong neodymium having dimensions of an outer diameter of 28 mm, an inner diameter of 20 mm, and a thickness of 3 mm, and a magnetic energy product of 45 M · G · Oe (Mega Gauss Oersted). The fixed magnet 34 has dimensions of an outer diameter of 75 mm, an inner diameter of 32 mm, and a thickness of 15 mm, and is made of ferrite. The movable magnet 33 and the fixed magnet 34 are magnetized to have the same polarity in the thickness direction, and repel each other. Accordingly, the negative stiffness generated in the third embodiment is 2800 (N / m), which is a large value exceeding the stiffness 2130 (N / m) of the support system of the speaker unit 31.
[0075]
In the third embodiment, there are provided means 35 and 35a for detecting deviation in the displacement direction of the vibration system of the speaker unit 31 and generating an electric signal, and the power amplifier 36 for driving the speaker unit 31 receives the signal from the detection means. The electric signal is fed back to correct the bias of the vibration system of the speaker unit 31 in the displacement direction.
[0076]
The means 35, 35a will be specifically described. Reference numeral 35 denotes a Hall element, which is vertically arranged near the center of the movable magnet 33 in the thickness direction. Reference numeral 35a is a feedback circuit that feeds back an output signal from the Hall element to the power amplifier 36.
[0077]
The Hall element 35 generates an output signal in accordance with a magnetic flux vector generated by the movable magnet 33 inward in the horizontal direction. At the center position of the movable magnet 33 in the thickness direction of the N pole and the S pole, the horizontal magnetic flux vector becomes zero. Therefore, when the center position in the thickness direction of the movable magnet 33 coincides with the center position in the vertical direction of the Hall element 35, no signal is output because the magnetic flux passing horizontally through the Hall element 35 is zero.
[0078]
When the movable magnet 33 is displaced in either direction, the magnetic flux distribution becomes asymmetric at the position of the Hall element 35 (in short, either the N pole side or the S pole side approaches the Hall element 35), and the horizontal direction Is generated. At this time, a signal is generated from the Hall element 35. Needless to say, for example, if the Hall element 35 generates a positive signal when the N pole approaches, the direction of the magnetic flux vector is reversed when the S pole approaches, so the Hall element 35 generates a negative signal.
[0079]
When the vibration system of the speaker unit 31 has no bias in the displacement direction, the electric signal generated by the Hall element 35 when low-frequency AC power is applied to the speaker unit 31 is a plus side signal and a minus side signal with respect to a zero level. Become symmetrical, and if this is integrated, the signal becomes zero. However, when a bias occurs in the vibration system, the level of either the plus side signal or the minus side signal increases (that is, a bias is generated), so that a signal is generated even when integration is performed.
[0080]
In the third embodiment, for example, when the vibration system of the speaker unit 31 starts to be biased to one side, the current is returned in the opposite direction, that is, the current in the direction of returning to the original displacement center position is output from the power amplifier 36 to the speaker unit 31. As a result, a Hall element 35 and a feedback circuit 35a are configured.
[0081]
FIG. 7 shows a circuit diagram of the detecting means 35 and 35a according to the third embodiment. Terminals 1 and 3 of the Hall element (HE) 35 are driving current terminals. Terminals 2 and 4 are output terminals, at which a detection voltage is generated. C is an integration capacitor, and the amplification gain of the OP (operational amplifier) attenuates as the frequency increases. As a result, feedback is applied only to the very low frequency component signal corresponding to the biased movement of the vibration system of the speaker unit 31. In other words, no feedback is generated for the movement of the vibration system of the bass such as music of several tens Hz or more, so that the bass is not adversely affected. VR is a volume for offset adjustment, and can perform adjustment such as making the detection voltage zero when the vibration system of the speaker unit 31 is at the center position.
[0082]
By this detection and feedback, the low-frequency sound reproduction speaker device of the third embodiment operates stably even if the generated negative stiffness exceeds the stiffness of the support system of the speaker unit 31, and equivalently reduces the internal volume of the cabinet 32. By increasing the frequency by 6.8 times, the lowest resonance frequency, that is, the low-frequency reproduction limit frequency could be significantly extended from 96 Hz to 67 Hz.
[0083]
As described above, according to the third embodiment, it is possible to realize a low-frequency sound reproduction speaker device having an extremely large equivalent volume in the cabinet and excellent low-frequency reproduction capability. In the third embodiment, since the Hall element 35 is used as the detecting means, the structure of the detecting means can be simplified.
[0084]
In the third embodiment, the Hall element 35 is used as the detecting means. However, for example, an optical method using a CDS, a photodiode, a phototransistor, or the like as a detecting element, or another method may be used. If a Hall IC is used instead of the Hall element 35, the feedback circuit can be omitted.
[0085]
Although the Hall element 35 detects the magnetic flux of the movable magnet 33, a small magnet may be attached to the vibration system separately from the movable magnet 33 to detect the magnetic flux.
[0086]
It goes without saying that the present invention is not limited to the above-described example.
[0087]
(Embodiment 4)
The configuration of the bass reproduction speaker device according to Embodiment 4 of the present invention will be described with reference to FIG.
[0088]
A speaker unit 41 (41a to 41g), a cabinet 42, a movable magnet 43, a fixed magnet 44, a hall element 45 as a detection unit, and a feedback circuit 45a according to the fourth embodiment are the same as those according to the third embodiment described with reference to FIGS. , A cabinet 32, a movable magnet 33, a fixed magnet 34, a Hall element 35 as a detecting means, and a feedback circuit 35a, which are completely the same. Specific description is omitted.
[0089]
In the fourth embodiment, means for holding the vibration system of the speaker unit 41 near the center position in the displacement direction when the bass reproducing speaker device is not operating, that is, when the power of the power amplifier 46 is turned off (vibration system holding). (Means) 47.
[0090]
This will be described in detail. A plunger 47a supplies power using a power amplifier 46 for driving the speaker unit 41 in the fourth embodiment. A rod 47b is attached to the voice coil 41c of the speaker unit 41, and is made of resin.
[0091]
The rod 47b is provided with a hole that fits into the arm of the plunger 47a, and locks the rod 47b when the plunger 47a is not energized. When the plunger 47a is energized, the arm is instantaneously sucked and detached from the rod 47b.
[0092]
Therefore, in the fourth embodiment, the vibration system of the speaker unit 41 is held near the center position in the displacement direction when the low-pitched sound reproduction speaker device is not operating, and a long time does not elapse to one side. For this reason, since the stress applied to the edge 41e and the damper 41d can be reduced, a long-life low-frequency sound reproduction speaker device with little change over time can be realized.
[0093]
It goes without saying that the present invention is not limited to the above-described example.
[0094]
(Embodiment 5)
The bass reproduction speaker device according to the fifth embodiment of the present invention uses the fixed magnet in each of the embodiments described above as an electromagnet. With this configuration, the negative stiffness generated by increasing or decreasing the current flowing through the electromagnet can be increased or decreased, so that the lowest resonance frequency of the bass reproduction speaker device can be varied. In addition, the energization of the fixed magnet electromagnet can be turned off when the low-frequency sound reproduction speaker device is not operating, and the generation of negative stiffness can be stopped when the low-frequency sound reproduction speaker device is not operating. .
[0095]
The electromagnet of the fixed magnet may be a superconducting magnet.
[0096]
In addition, it goes without saying that the present invention is not limited to the examples described above.
[0097]
【The invention's effect】
As described above, according to the low-frequency sound reproduction speaker device according to claim 1 of the present invention, the speaker unit, the cabinet that houses the speaker unit, the movable magnet that moves together with the vibration system of the speaker unit, and the fixed magnet By providing the movable magnet and the fixed magnet so as to generate negative stiffness with respect to the vibration system of the speaker unit, the generation of the negative stiffness is not caused by mechanical means, and no contact portion is generated. Since it can be carried out without any noise, there is no occurrence of mechanical fatigue or noise. Therefore, it is possible to realize a practical bass reproduction speaker device having excellent reliability.
[0098]
further The fixed magnet is formed in a ring shape, and the inner peripheral side of the fixed magnet. At the center in the thickness direction The movable magnet Coaxial By arranging, only two magnets are required to generate negative stiffness, so the structure is simple, and the size of the fixed magnet can be increased, so that it is easy to obtain a very large negative stiffness. Can be. Further, the displacement-force characteristic curve of the generated negative stiffness is linear. Therefore In addition to the above It is possible to realize a low-frequency sound reproduction speaker device which is simple and has excellent performance.
[0100]
Moreover Detecting means for detecting a bias in the displacement direction of the vibration system of the speaker unit to generate an electric signal, and feeding back the electric signal from the detecting means to a power amplifier for driving the speaker unit; By correcting the bias in the displacement direction of the vibration system, even if the generated negative stiffness exceeds the stiffness of the support system of the speaker unit, it operates stably, so the equivalent internal volume of the cabinet is extremely large. In addition to the above It is possible to realize a low-frequency sound reproduction loudspeaker device having a further excellent low-frequency reproduction capability.
[0102]
Moreover By providing a means for holding the vibration system of the speaker unit near the center position in the displacement direction when not operating, the vibration system of the speaker unit is not biased to one side during non-operation and does not elapse for a long time. And the stress applied to the damper can be reduced. Therefore In addition to the above A long-life low-frequency sound reproduction speaker device with little change over time can be realized.
[0104]
As described above, the present invention has an extremely large practical value.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a structure of a bass reproduction speaker device according to a first embodiment of the present invention.
FIG. 2 is a stiffness displacement-force characteristic curve diagram showing the principle of improving the low-frequency reproduction capability of the bass reproduction speaker device of the present invention.
FIG. 3 is a cross-sectional view showing a configuration of a movable magnet and a fixed magnet portion of the bass reproduction speaker device having another configuration according to the first embodiment of the present invention.
FIG. 4 is a cross-sectional view showing a configuration of a movable magnet and a fixed magnet portion of the low-frequency sound reproduction speaker device having still another configuration of the first embodiment of the present invention.
FIG. 5 is a stiffness displacement-force characteristic curve diagram of the bass reproduction speaker device according to the second embodiment of the present invention.
FIG. 6 is a cross-sectional view showing a configuration of a bass reproduction speaker device according to Embodiment 3 of the present invention.
FIG. 7 is a circuit diagram of a detection unit according to a third embodiment of the present invention.
FIG. 8 is a cross-sectional view illustrating a configuration of a bass reproduction speaker device according to a fourth embodiment of the present invention.
FIG. 9 is a sectional view showing the structure of a conventional bass reproduction speaker device.
[Explanation of symbols]
1,11,21,31,41 Speaker unit
1a, 11a, 21a, 31a, 41a Field part
1b, 31b, 41b frame
1c, 11c, 21c, 31c, 41c Voice coil
1d, 31d, 41d damper
1e, 31e, 41e edge
1f, 31f, 41f diaphragm
1g, 31g, 41g Dust cap
2,32,42 cabinet
3,13,23,33,43 Movable magnet
4,14a, 14b, 24,34,44 Fixed magnet
35, 45 Hall element
35a, 45a feedback circuit
36,46 power amplifier
47 Vibration system holding means
47a plunger
47b rod

Claims (1)

A speaker unit, a cabinet accommodating the speaker unit, a movable magnet that moves together with a vibration system of the speaker unit, and a fixed magnet, wherein the movable magnet and the fixed magnet are negative with respect to the vibration system of the speaker unit. The fixed magnet is configured to generate stiffness, the fixed magnet is formed in a ring shape, the movable magnet is arranged coaxially at the center position in the thickness direction on the inner peripheral side of the fixed magnet, and the moving direction of the vibration system of the speaker unit is changed. Detecting means for detecting the deviation and generating an electric signal, and feeding back the electric signal from the detecting means to a power amplifier for driving the speaker unit, thereby correcting the deviation in the displacement direction of the vibration system of the speaker unit; When the speaker unit is not operating, the vibration system of the speaker unit is centered in the displacement direction. Bass reproduction speaker apparatus characterized by comprising means for holding the.

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