Electrodynamic loudspeaker parameter test system

Abstract

The present invention discloses an electric loudspeaker parameter testing system, which is characterized in that it includes a control host, a dynamic signal acquisition card, a current sensor and a voltage sensor. After the transducer is connected to the electric loudspeaker, the current sensor and the voltage sensor respectively record the current signal and the voltage signal between the transducer terminals. After the control host collects the current signal and the voltage signal via the dynamic signal acquisition card, an electrical impedance curve is obtained, and a relationship between the electrical impedance curve and the magnetic circuit force factor BL is established. The relationship is fitted with multiple parameters to obtain the value of the magnetic circuit force factor BL and derive the related small signal parameters. The present invention has the advantages of high signal-to-noise ratio, low cost, strong adaptability, high efficiency and convenience. The present invention can be used for parameter measurement and quality control in laboratory research and development and batch production on production lines.

Description

Technical Field

[0001] The present invention relates to a parameter testing system for an electrodynamic (dynamic) loudspeaker, which is used to guide the early development and subsequent batch production process control of electroacoustic products and can be applied to the testing of acoustic systems such as speakers, headphones, mobile phones, and car audio. Background Art

[0002] Loudspeakers have a history of over a hundred years, and vented (or reflex) and closed-box systems span over half a century. Thiele's filter synthesis approach ushered in a new era of rigorous design theory. In the 1970s, Dr. Small of the University of Sydney, Australia, published a series of renowned papers that advanced loudspeaker system design to a systematic level. Since then, loudspeaker manufacturers and international standards have adopted Small's recommendations to varying degrees, listing both small-signal and large-signal parameters in product specifications and standards. These are known as TS parameters (T for Mr. Thiele, S for Mr. Small).

[0003] As a speaker unit, Small's theory summarizes the four most basic small signal parameters, namely f s 、V AS , Q ms , Q es , where: f s is the resonant frequency of the vibration system of the speaker unit; V AS is the equivalent volume of the speaker unit's acoustic compliance; Q ms is the mechanical damping factor of the loudspeaker unit, is the electrical equivalent reactance of the vibration system at f s The ratio of Q es is the DC impedance of the voice coil to the reactive reactance at f s The ratio of is the electromagnetic damping factor of the speaker unit.

[0004] f s 、V AS , Q ms and Q es It is easy to obtain by measurement and plays a dominant role in the design of the speaker system. In fact, the physical parameters of the speaker unit that determine these four parameters are: voice coil DC resistance R e , magnetic flux density B in the magnetic gap, length L of the voice coil wire in the magnetic field, effective projected area Sd (=πr 2 ), the force compliance C of the vibration system ms , including the mechanical mass M of the speaker and air load ms , the force resistance R of the vibration system ms, where the magnetic flux density B in the magnetic gap and the length L of the voice coil wire in the magnetic field are expressed as BL, which is also called the magnetic circuit force factor.

[0005] Currently, there are three main methods for testing loudspeaker parameters: the weight-added method, the compliance-added method, and the laser Doppler method. The weight-added method requires attaching a certain mass to the surface of the loudspeaker under test, changing its electrical impedance curve. All small-signal parameters are then derived through calculations based on certain physical relationships. The compliance-added method requires adding an additional cavity to change the overall compliance of the loudspeaker, and then deriving all small-signal parameters. The laser Doppler method is a direct measurement method that directly obtains the vibration velocity of the diaphragm surface and then derives all small-signal parameters. The weight-added method and the compliance-added method require multiple measurements, which is time-inefficient and may damage the sample during the measurement process. Furthermore, in actual operation, the measured values ​​fluctuate with changes in the additional parameters, resulting in low test accuracy. The laser Doppler method requires an additional laser velocity sensor and ensures good reflectivity on the loudspeaker diaphragm surface. Although the laser Doppler method only requires a single measurement, the entire setup is expensive and requires special sample handling, so it is only used in the research and development stage.

[0006] Therefore, the accuracy and cost-effectiveness of traditional measurement methods need to be improved. Summary of the Invention

[0007] The technical problem to be solved by the present invention is that the loudspeaker parameter measurement method has low precision and poor cost performance.

[0008] To solve the above technical problems, the technical solution of the present invention is to provide an electrodynamic loudspeaker parameter testing system, characterized in that it includes a control host, a dynamic signal acquisition card, a current sensor, and a voltage sensor. After the transducer is connected to the electrodynamic loudspeaker, the current sensor and the voltage sensor respectively record the current signal and voltage signal between the transducer terminals. After the control host collects the current signal and voltage signal via the dynamic signal acquisition card, an electrical impedance curve is obtained. The relationship between the electrical impedance curve and the magnetic circuit force factor BL is established based on the following formula:

[0009]

[0010] In the above formula, Z vc To consider the first-order electrical impedance model of the inductor, R e is the DC resistance of the voice coil, L e is the voice coil inductance, R ms is the force resistance of the vibration system, BL is the magnetic circuit force factor, C ms is the force compliance of the vibration system, M ms is the mechanical mass of the speaker and air load, ω0 is the resonant angular frequency, Z vc(ω0) is the impedance peak, p is the sound pressure level in the quality control area, V in is the input voltage value, S D is the equivalent radiation area of ​​the loudspeaker, ρ is the air density, r is the effective radius of the loudspeaker, Q ms is the equivalent mechanical quality factor, Q ts is the total quality factor of the system;

[0011] Multi-parameter fitting is performed on the relationship to obtain the BL value of the magnetic circuit force factor and deduce the related small signal parameters.

[0012] Preferably, the sound pressure level p in the quality control area is the far-field test result. If the actual test is the near-field pressure, the near-field to far-field conversion relationship is as follows:

[0013]

[0014] Where p far is the sound pressure level in the quality control area of ​​the far-field test, p near is the sound pressure level in the quality control area of ​​the near-field test.

[0015] Preferably, the sound pressure conversion relationship satisfies p=10 dB / 20 ·2·10 -5 Pa, Pa is the pressure in the SI unit system, the unit is Pascal.

[0016] Preferably, when performing multi-parameter fitting, the real part and the imaginary part are fitted separately, and the real part of the strict impedance formula is as follows:

[0017]

[0018] The imaginary part of the strict impedance formula is as follows:

[0019]

[0020] After dividing the real and imaginary parts of the impedance, we get two extreme angular frequency points ω1 and ω2, and the following relationship exists:

[0021]

[0022]

[0023] ω1-ω2=A / M ms

[0024] Where,

[0025] The magnetic circuit force factor BL is directly obtained through the three relationship equations of the two angular frequency extreme points ω1 and ω2, and then the small signal parameters are gradually obtained.

[0026] The present invention is based on the classic electroacoustic system model and utilizes the acoustic impedance calculation relationship of the loudspeaker small signal model. It can be used for design evaluation in the R&D stage and for the control of materials and assembly processes in the subsequent production stage. In the past, measuring loudspeaker parameters was time-consuming and labor-intensive, and was often limited to the laboratory verification stage due to the complicated process and high cost. The present invention has developed a new test system that uses the electrical impedance curve and sound pressure value of the loudspeaker to quickly and efficiently fit the loudspeaker parameters. The present invention proposes a test system for T / S parameters based on the loudspeaker impedance curve and sound pressure value. Compared with traditional parameter testing methods such as the added mass method, the added compliance method and the laser Doppler method, the system has the advantages of high signal-to-noise ratio, low cost, strong adaptability, high efficiency and convenience. The present invention can be used for parameter measurement and quality control in laboratory R&D and batch manufacturing on production lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of signal transmission in the test system;

[0028] Figure 2 This is a schematic diagram of the test system hardware connection. DETAILED DESCRIPTION

[0029] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0030] like Figure 1 and Figure 2 As shown, the electrodynamic loudspeaker parameter testing system disclosed in this embodiment includes a control host, a dynamic signal acquisition card, a current sensor, and a voltage sensor. After connecting the transducer to the electrodynamic loudspeaker, the current sensor and voltage sensor respectively record the current and voltage signals between the transducer terminals. The control host collects the current and voltage signals via the dynamic signal acquisition card to generate an electrical impedance curve.

[0031] The physical parameters of a loudspeaker unit exist objectively, and small-signal parameters have a definite relationship with them. However, TS parameters are more convenient in analysis and design. In the small-signal model, the electrical impedance curve has the following basic relationship as shown in formulas (1) to (4):

[0032]

[0033] In formula (1), Z vc To consider the first-order electrical impedance model of the inductor, L eis the voice coil inductance. In formula (2), ω0 is the resonant angular frequency. In formula (3), Z vc (ω0) is the impedance peak. In formula (4), p is the sound pressure level in the quality control area (relatively flat SPL area), S D is the equivalent radiation area of ​​the loudspeaker, ρ is the air density, and r is the effective radius of the loudspeaker.

[0034] It should be noted that formula (4) is the far-field test result. If the actual test is the near-field pressure, the near-field to far-field conversion relationship is shown in formula (5):

[0035]

[0036] In formula (5), p far is the sound pressure level in the quality control area of ​​the far-field test, p near is the sound pressure level in the quality control area of ​​the near-field test.

[0037] The transformation of formula (2) is:

[0038]

[0039] We can further obtain formula (6):

[0040]

[0041] The formula (7) can be obtained by transforming formula (3):

[0042]

[0043] The formula (4) can be transformed into formula (8):

[0044]

[0045] In formula (8), the sound pressure conversion relationship satisfies p=10 dB / 20 ·2·10 -5 Pa, Pa is the pressure in the SI unit system, the unit is Pascal.

[0046] At the same time, several quality factors and small signal parameters have the relationship shown in formula (9) and formula (10):

[0047]

[0048] In formula (9), Q ms is the equivalent mechanical quality factor, Q ts is the total quality factor of the system.

[0049] Therefore, a relationship between the electrical impedance curve and the magnetic circuit force factor BL can be established, where the known quantities are DC impedance, inductance (the high-frequency part is approximated), resonant frequency, speaker size, and radiation sensitivity. Multi-parameter fitting is performed on the relationships described in formulas (1), (6), (7), (8), (9), and (10), and the magnetic circuit force factor BL value can be obtained, and the related small signal parameters can be derived to obtain all the transducer parameters.

[0050] In order to reduce the amount of calculation, the real part and imaginary part are fitted separately when performing multi-parameter fitting. The real part and imaginary part of the strict impedance formula are shown in the following equations (11) and (12):

[0051]

[0052] Formula (11) is the real part of the impedance, and formula (12) is the imaginary part of the impedance.

[0053]

[0054]

[0055] Where, is the newly defined process intermediate quantity, is the derivative of the newly defined process intermediate quantity.

[0056]

[0057] ω1 and ω2 are two angular frequency extreme points obtained by dividing the real and imaginary parts of the impedance, and have the following relationship:

[0058]

[0059] ω1-ω2=A / M ms

[0060] Through the three relationship equations of the two angular frequency extreme points ω1 and ω2, the magnetic circuit force factor BL can be directly obtained, and then other parameters can be gradually obtained.

Claims

1. An electrodynamic loudspeaker parameter testing system, characterized in that: The system includes a control host, a dynamic signal acquisition card, a current sensor, and a voltage sensor. After the transducer is connected to the electrodynamic speaker, the current sensor and the voltage sensor respectively record the current signal and voltage signal between the transducer terminals. After the control host collects the current signal and voltage signal via the dynamic signal acquisition card, an electrical impedance curve is obtained. The relationship between the electrical impedance curve and the magnetic circuit force factor BL is established based on the following formula: In the above formula, Z vc To consider the first-order electrical impedance model of the inductor, R e is the DC resistance of the voice coil, L e is the voice coil inductance, R ms is the force resistance of the vibration system, BL is the magnetic circuit force factor, C ms is the force compliance of the vibration system, M ms is the mechanical mass of the speaker and air load, ω0 is the resonant angular frequency, Z vc (ω0) is the impedance peak, p is the sound pressure level in the quality control area, V in is the input voltage value, S D is the equivalent radiation area of ​​the loudspeaker, ρ is the air density, r is the effective radius of the loudspeaker, Q ms is the equivalent mechanical quality factor, Q ts is the total quality factor of the system; Perform multi-parameter fitting on the relationship to obtain the BL value of the magnetic circuit force factor and derive the related small signal parameters; When performing multi-parameter fitting, the real part and imaginary part are fitted separately. The real part of the strict impedance formula is as follows: The imaginary part of the strict impedance formula is as follows: After dividing the real and imaginary parts of the impedance, we get two extreme angular frequency points ω1 and ω2, and the following relationship exists: Where, The magnetic circuit force factor BL is directly obtained through the three relationship equations of the two angular frequency extreme points ω1 and ω2, and then the small signal parameters are gradually obtained.

2. The electrodynamic loudspeaker parameter testing system according to claim 1, wherein: The sound pressure level p in the quality control area is the far-field test result. If the actual test is the near-field pressure, the near-field to far-field conversion relationship is as follows: Where p far is the sound pressure level in the quality control area of ​​the far-field test, p near is the sound pressure level in the quality control area of ​​the near-field test.

3. The electrodynamic loudspeaker parameter testing system according to claim 1, wherein: The sound pressure conversion relationship satisfies p=10 dB / 20 ·2·10 -5 Pa.

Images