CN211184252U

CN211184252U - Amplitude detection device of moving-coil loudspeaker

Info

Publication number: CN211184252U
Application number: CN201921593076.4U
Authority: CN
Inventors: 不公告发明人
Original assignee: Huizhou Difenni Acoustic Technology Co ltd
Current assignee: Huizhou Difenni Acoustic Technology Co ltd
Priority date: 2019-09-24
Filing date: 2019-09-24
Publication date: 2020-08-04
Anticipated expiration: 2029-09-24

Abstract

The application discloses amplitude detection device of moving coil speaker includes: the electric capacity measurer comprises an electric capacity measurer, a first lead and a second lead, wherein a conductive voice coil framework located in a magnetic gap formed between a first soft iron and a washer is electrically connected with one end of the first lead, one end of the second lead is electrically connected with the first soft iron, and the other end of the first lead and the other end of the second lead are connected with the electric capacity measurer. The application provides an amplitude detection device and method of a moving-coil loudspeaker, which can reduce cost, ensure precision, stabilize structure and ensure service life.

Description

Amplitude detection device of moving-coil loudspeaker

Technical Field

The present application relates to the field of speaker technology, and more particularly, to an amplitude detection device for a moving-coil speaker.

Background

Fig. 1 shows a block diagram of a conventional external magnetic moving coil speaker. The moving-coil loudspeaker comprises a frame, and a vibration system and a magnetic circuit system which are accommodated in the frame, wherein the vibration system comprises a vibrating diaphragm and a voice coil 10; the magnetic circuit system 20 comprises a washer 21, a magnet 22 and a T-iron 23. A magnetic gap is formed between the washer 21 and the T-shaped iron 23, the voice coil 10 moves up and down in the magnetic gap, and the voice coil 10 comprises a voice coil framework 11 and a coil 12.

When the amplitude of the loudspeaker is very small, the stiffness coefficient Kms of a suspension system of the loudspeaker, the mechanical factor B L and the inductance L e of a magnetic circuit system can be considered as constants, which are often marked as Kms0, B L0 and L e0, and are considered to be irrelevant to the amplitude x, so that the distortion of the loudspeaker under small amplitude is very small.

However, the working of the loudspeaker depends on the amplitude of the diaphragm to push air to generate sound waves, and various existing acoustic products seek the output of high power and large sound pressure level, and the amplitude x is very large at this time, but the stiffness coefficient, the mechanical factor and the inductance cannot be regarded as constants under small amplitude, but can change along with the change of the amplitude x, and the change along with the amplitude x is not a linear relation, namely, the nonlinear, and is marked as Kms (x), B L (x) and L e (x), and the nonlinear is also the main source of various distortions of the loudspeaker.

When the moving-coil loudspeaker works, the driving force is from the voice coil, the displacement of the voice coil represents the amplitude of the loudspeaker, the nonlinear Kms (x), B L (x) and L e (x) are all unary multiple functions related to the amplitude x, and can be fitted according to the following 4-degree polynomial expression:

Kms(x)＝Kms0+Kms1x¹+Kms2x²+Kms3x³+Kms4x⁴

BL(x)＝BL0+BL1x¹+BL2x²+BL3x³+BL4x⁴

Le(x)＝Le0+Le1x¹+Le2x²+Le3x³+Le4x⁴

according to the vibration equation of the loudspeaker and the nonlinear expressions, the distortion curve of the loudspeaker can be predicted. In some known technologies, the amplitude x of the speaker during operation is detected by various different technologies to form a dynamic feedback to an electronic system of the sound box, and the magnitude of the audio signal voltage input to the speaker is automatically adjusted according to the magnitude of the real-time amplitude x by using a pre-designed digital signal processing module, so that the distortion performance of the speaker is effectively controlled in the whole working process.

Currently known techniques for loudspeaker amplitude detection include: acceleration sensor, Hall sensor, infrared ray displacement sensor, second coil response principle. However, the conventional amplitude detection method has the following major disadvantages or problems:

one, the cost is expensive. No matter which sensor among the acceleration sensor, the hall sensor and the infrared displacement sensor is used, an additional sensor must be added on the loudspeaker.

Secondly, the working accuracy of the sensor is problematic, because the voice coil vibrates rapidly up and down in a narrow magnetic gap, the sensor cannot directly align with the voice coil to measure. Usually the sensor can only be fixed to the frame or the magnetic circuit and the displacement or acceleration is detected against a certain point on the diaphragm. When the loudspeaker works under the condition of high-power input, the basin frame or the magnetic circuit has certain vibration, so that the detection result is inaccurate. Similarly, the diaphragm is easy to generate segmentation vibration, and the amplitude of the loudspeaker is difficult to accurately represent no matter the displacement of any point on the diaphragm.

When the loudspeaker works, a large amount of heat and air flow are generated, the temperature of a magnetic circuit can reach more than 100 ℃, and the service life of a sensor fixed on the loudspeaker is tested seriously.

And fourthly, when the second coil induction principle is used for detecting the displacement of the voice coil, the second coil needs to be wound on the voice coil, the integral vibration quality is increased undoubtedly, and the sensitivity of the loudspeaker is sacrificed.

Because of various defects of the current loudspeaker amplitude detection method, the amplitude detection method is actually used and dynamically fed back to the system, and few products are used for distortion control.

SUMMERY OF THE UTILITY MODEL

To the above-mentioned problem among the correlation technique, this application provides an amplitude detection device of moving coil speaker, can realize reduce cost, guarantee precision, stable in structure and life and obtain the guarantee.

The technical scheme of the application is realized as follows:

according to an aspect of the present application, there is provided an amplitude detecting apparatus for a moving-coil speaker, comprising: a capacitance measuring device, a first conductive line, and a second conductive line,

the conductive voice coil framework located in the magnetic gap formed between the first soft iron and the washer is electrically connected with one end of the first lead, one end of the second lead is electrically connected with the first soft iron, and the other end of the first lead and the other end of the second lead are connected with the capacitance measurer.

According to the embodiment of the application, the moving-coil loudspeaker is an external magnetic moving-coil loudspeaker, and the first soft iron is T-shaped soft iron.

According to an embodiment of the present application, one end of the second conductive wire is directly electrically connected to a lower surface of the T-shaped soft iron.

According to the embodiment of the application, the first soft iron of the internal magnetic moving-coil loudspeaker of the moving-coil loudspeaker is U-shaped soft iron.

According to an embodiment of the present application, one end of the second wire is directly electrically connected to a surface of the U-shaped soft iron.

According to an embodiment of the present application, the first soft iron is a soft iron made of a low carbon steel material.

According to an embodiment of the application, the first conductor is a silk thread.

According to the embodiment of the application, the first conducting wire is the same as a lead wire type used for inputting the audio signal to the voice coil of the moving coil loudspeaker.

According to an embodiment of the present application, the capacitance measurer is a capacitance detection circuit.

The capacitor structure of the air medium is innovatively constructed between the magnetic circuit system of the loudspeaker and the voice coil, and the capacitor structure is the air medium capacitor which only changes along with the displacement of the voice coil. The required physical structure is extremely concise, and various sensors or secondary coils required by the traditional method are not needed, so that the cost of detecting the amplitude is reduced to the minimum;

the change of the capacitance value can well represent the displacement of the voice coil, namely the amplitude of the loudspeaker. In addition, the detection precision can be ensured;

compared with a detection method (the sensitivity is reduced) of adding a secondary coil on a voice coil by using a traditional method, the method can keep the original acoustic performance of the loudspeaker; and compare with traditional detection method increase that the sensor can receive the threat of heat damage, detection device stable in structure, life that this application provided can be ensured.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is a structural view of a conventional external magnetic moving coil speaker;

fig. 2 is a sectional view of a partial structure of a moving-coil speaker and an amplitude detecting device thereof according to an embodiment of the present application;

fig. 3 is a top view of a voice coil bobbin and a center post in a T-iron in a moving coil speaker according to an embodiment of the present application;

FIG. 4 is a simulation result of the structure shown in FIGS. 2 and 3;

fig. 5 is a sectional view of a partial structure of a moving-coil speaker and an amplitude detecting device thereof according to another embodiment of the present application;

fig. 6 is a top view of a voice coil bobbin and U-shaped soft iron in a moving coil speaker according to another embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments that can be derived from the embodiments given herein by a person of ordinary skill in the art are intended to be within the scope of the present disclosure.

Fig. 2 is a sectional view showing a partial structure of a moving-coil speaker and an amplitude detecting apparatus thereof according to an embodiment of the present application. As shown in fig. 2, a conductive voice coil bobbin 11 having a conductive property is located in a magnetic gap formed between the first soft iron and the washer 21. In the embodiment shown in fig. 2, the first soft iron is T-shaped soft iron 23. The amplitude detection means of the moving coil loudspeaker comprises a first wire 31 and a second wire 32. The voice coil bobbin 11 is electrically connected to one end of the first wire 31, and the other end of the first wire 31 is led out to the outside of the speaker as a first pole of a physical quantity to be detected later. The first wire 31 needs to be a flexible and bend resistant wire. One end of the first wire 31 may be soldered to the conductive bobbin to be electrically connected to the voice coil bobbin 11. One end of the second wire 32 is electrically connected to the first soft iron (e.g., T-shaped soft iron 23). The other end of the second wire 32 serves as a second pole of the detected physical quantity.

In one embodiment, the first conductor 31 is a tinsel wire. In one embodiment, the first wire 31 is the same type of lead wire as the audio signal of the speaker is input to the voice coil. Because the first lead 31 can continuously vibrate together with the voice coil when the loudspeaker works, the lead wire is selected to ensure the service life of the first lead 31 and ensure that the lead wire can continuously and stably keep electric conduction with the voice coil framework 11 from the outside of the loudspeaker. Since the second wire 32 does not need to be vibration-resistant to fatigue, a common wire may be used for the second wire 32.

In addition, the other end of the first conductive line 31 and the other end of the second conductive line 32 may be electrically connected to a capacitance measurer of the amplitude detecting device. In one embodiment, the capacitance measurer is a capacitance detection circuit. The capacitance detection circuit is used to detect the two poles led out from the first conducting wire 31 and the second conducting wire 32 to obtain a capacitance value C, and the capacitance value C can well represent the amplitude x of the loudspeaker. Because the detection technology of the capacitance value by using the detection circuit is mature, the precision of the detection method can be ensured.

In the present embodiment, the moving-coil speaker is an external magnetic moving-coil speaker, and the first magnet is T-shaped soft iron (may be generally referred to as T-iron) 23. In one embodiment, one end of the second wire 32 may be directly electrically connected to the surface of the T-shaped soft iron 23. Since the lower surface of the T-shaped soft iron 23 is exposed on the outer surface of the speaker and is easily connected, one end of the second wire 32 may be directly electrically connected to the lower surface of the T-shaped soft iron 23 as shown in fig. 2.

As the conductive voice coil bobbin 11, for example, a metal bobbin or the like having a conductive property may be used. In one embodiment, the voice coil bobbin 11 is an aluminum bobbin. The T-shaped soft iron 23 is a magnet made of a low-carbon steel material. Metal frames, such as titanium frames and aluminum frames, are also found in conventional moving coil speakers, with aluminum frames being most used. Because the aluminum framework has light weight, strong rigidity, low price and good heat conduction and heat dissipation capability. But very few have noticed and used the conductive properties of the aluminum skeleton. Another property that is easily overlooked is that the T-shaped soft iron 23 and the washer 21 in the magnetic circuit system are both made of mild steel, because the high permeability of mild steel is helpful for magnetic conduction, but in practice, mild steel not only can conduct magnetism, but also has the conductive property.

As can be seen from fig. 1 and 2, the T-iron center post 231 of the T-shaped soft iron 23 forms a magnetic gap with the inner diameter of the washer 21, and the voice coil moves up and down in the magnetic gap with a constant size. If the gap is too small, the abnormal sound of the wiping ring tends to be poor, and if the gap is too large, the magnetic flux density B of the magnetic gap becomes too small, and the sensitivity of the speaker becomes insufficient. Therefore, in some embodiments, the gap d between the voice coil bobbin 11 and the center post 231 of the T-iron is generally 0.2-0.5 mm. Throughout the operation of the speaker, the voice coil bobbin 11 is kept vibrating vertically up and down within a narrow magnetic gap, and the displacement of the voice coil bobbin 11 best characterizes the amplitude of the speaker. Once the product design is finalized, the gap d between the voice coil bobbin 11 and the center post 231 of the T-iron is fixed. The top view of the voice coil bobbin 11 and the T-iron center post 231 is shown in fig. 3, because both the voice coil bobbin 11 and the T-iron center post 231 have conductive properties and the magnetic gap therebetween is uniform, an air dielectric capacitor formed by the inner cylinder electrode and the outer cylinder electrode of the two mutually insulated coaxial cylindrical plates can be formed between the voice coil bobbin 11 and the T-iron center post 231.

The air dielectric capacitor formed here is a cylindrical capacitor whose capacitance value is determined by the formula:

C＝2π*x/(LnR-Lnr)。

where, it is dielectric constant, x is the facing length between the cylindrical plates, R is the radius of the first electrode (i.e., outer cylinder electrode) formed by the voice coil bobbin 11, and R is the radius of the second electrode (i.e., inner cylinder electrode) formed by the T-iron center post 231, since both R and R are constants, the capacitance value C ═ a ═ x is obtained by making constant 2 pi/(L nR-L nR) ═ a (a is a constant).

Because the speaker during operation is vibrating all the time, the displacement x of voice coil loudspeaker voice coil is constantly changing, has resulted in the capacitance value C constantly changing between voice coil loudspeaker voice coil skeleton 11 and the T iron, deducing by above capacitance value formula and can deriving capacitance value C and be the univariate function relation of voice coil loudspeaker voice coil displacement x, as long as detect capacitance value C's change just can calculate voice coil loudspeaker voice coil displacement x's change, consequently this application is through increasing first wire 31 and second wire 32 and drawing out two poles of the earth from voice coil loudspeaker voice coil skeleton 11 and T type soft iron 23's surface and detect the capacitance value.

Fig. 4 shows simulation results of the structures shown in fig. 2 and fig. 3, which are matched with the above theoretical analysis, and fig. 4 clearly shows a linear relationship between voice coil displacement and detected capacitance, thereby further verifying the usability of the amplitude detection method of the present application.

Fig. 5 is a sectional view showing a partial structure of a moving-coil speaker and an amplitude detecting device thereof according to another embodiment of the present application. Fig. 6 is a plan view showing the voice coil bobbin and the U-shaped soft iron in the structure shown in fig. 5. In the present embodiment, the moving-coil speaker is an internal magnetic moving-coil speaker, the voice coil bobbin 11 is located in a magnetic gap formed between the first magnet and the washer 21, and the first magnet is a U-shaped soft iron (may be generally referred to as U-iron) 24. The amplitude detection device provided by the present application is suitable for moving coil speakers of any configuration, such as the magnetic circuit system of external magnetic structure shown in fig. 2 and 3, which is an air capacitor formed by the center post 231 of the T-iron and the voice coil bobbin 11. For the magnetic circuit system with internal magnetic structure, as shown in fig. 5 and 6, the side wall of the U-shaped soft iron 24 and the voice coil bobbin 11 are used to form an air capacitor, and only the surface of the T-shaped soft iron 23 of the second electrode for measuring the capacitance value needs to be changed into the surface of the U-shaped soft iron 24, that is, one end of the second wire 32 is directly electrically connected to the surface of the U-shaped soft iron 24. The working principle of the magnetic circuit system is the same as that of the magnetic circuit system with the external magnetic structure, and the structure is simple and stable.

In summary, the present application constructs an air dielectric capacitor structure between the magnetic circuit system of the speaker and the voice coil, and the air dielectric capacitor structure is an air dielectric capacitor which changes only with the displacement of the voice coil. The required physical structure is extremely concise, and various sensors or secondary coils required by the traditional method are not needed, so that the cost of detecting the amplitude is reduced to the minimum;

the displacement of the voice coil, namely the amplitude of the loudspeaker can be well represented by the change of the capacitance value through calculation of the capacitance value formula. The detection technology of the capacitance value by using the detection circuit is mature, so the precision of the detection method can be ensured;

The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. An amplitude detection device for a moving-coil speaker, comprising: a capacitance measuring device, a first conductive line, and a second conductive line,

2. The amplitude detection device of a moving-coil speaker according to claim 1,

the moving-coil loudspeaker is an external magnetic moving-coil loudspeaker, and the first soft iron is T-shaped soft iron.

3. The amplitude detection device of a moving-coil speaker according to claim 2,

the one end of the second lead is directly and electrically connected with the lower surface of the T-shaped soft iron.

4. The amplitude detection device of a moving-coil speaker according to claim 1,

the inner magnetic type moving coil loudspeaker of the moving coil loudspeaker is characterized in that the first soft iron is U-shaped soft iron.

5. The amplitude detection device of a moving-coil speaker according to claim 4,

the one end of the second lead is directly and electrically connected with the surface of the U-shaped soft iron.

6. The amplitude detection device of a moving-coil speaker according to any one of claims 1 to 5, wherein the first soft iron is a soft iron made of a low-carbon steel material.

7. The amplitude detection device of a moving-coil speaker according to any one of claims 1 to 5, wherein the first conductive wire is a tinsel wire.

8. The amplitude detection device of a moving-coil speaker according to claim 7, wherein the first conductive line is the same type as a lead wire line used for inputting an audio signal to the voice coil of the moving-coil speaker.

9. The amplitude detection device for a moving-coil speaker according to any one of claims 1 to 5, wherein the capacitance measuring device is a capacitance detection circuit.