Method for monitoring impedance of horn in real time

Abstract

The invention discloses a method for monitoring the impedance of a horn in real time, and the method comprises the following steps: (1) measuring an impedance curve of the horn through frequency sweeping according to a transfer function of the impedance of the horn; (2) based on a relation that an impedance curve changes along with temperature, superposing a low-frequency signal to test a low-frequency impedance curve of the loudspeaker; and (3) adjusting the impedance between the output of the power amplifier and the loudspeaker based on the low-frequency impedance curve, and judging whether the loudspeaker is normal or not. According to the invention, the impedance curve can be monitored in real time, the impedance can be automatically adjusted according to the impedance curve, and the loudspeaker can work in an optimal effect through test feedback.

Description

Technical Field

[0001] This invention relates to the field of audio amplification technology, and in particular to a method for real-time monitoring of speaker impedance, applicable to scenarios such as corporate meetings, government venues, and large multi-functional halls. Background Technology

[0002] The impedance equivalent circuit model of a loudspeaker is: Z(f) = Re + j2πfLe + Z_mech(f) + Z_acoustic(f), where Re is the DC resistance, f is the frequency, Le is the voice coil inductance, Z_mech(f) is the mechanical impedance of the vibrating system (related to resonance, damping, and mass), and Z_acoustic(f) is the equivalent impedance of the acoustic load (such as the influence of the enclosure, duct, etc.). The main influences are Re and Le, whose values ​​adjust with temperature.

[0003] As the speaker operates at varying temperatures, the diaphragm shifts, and the speaker's impedance changes due to aging or mechanical fatigue, leading to decreased volume, reduced power output, altered timbre, and increased distortion. In extreme cases, a rapid drop in impedance can damage the power amplifier and other amplifiers.

[0004] For the reasons mentioned above, there is a need in the speaker system to monitor the speaker impedance curve in real time, so as to ensure that the speaker impedance can be monitored during use and to take corresponding measures based on the impedance test results, such as impedance compensation, output power adjustment and even system protection.

[0005] Through the above monitoring, the following can be accomplished: Speaker protection: Immediately shut down the power amplifier when impedance is abnormal (such as short circuit or open circuit); Aging diagnosis: Long-term monitoring of impedance changes to determine the horn's condition; Intelligent EQ / DSP: Adaptive compensation or enclosure resonance calibration based on impedance feedback. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for real-time monitoring of speaker impedance.

[0007] The objective of this invention is achieved through the following technical solution: a method for real-time monitoring of speaker impedance, the method comprising the following steps: (1) Measure the impedance curve of the horn by sweeping the frequency based on the transfer function of the horn impedance; (2) Based on the relationship between impedance curve and temperature, the low-frequency impedance curve of the speaker is tested by superimposing a low-frequency signal. (3) Adjust the impedance between the power amplifier output and the speaker based on the low-frequency impedance curve, and determine whether the speaker is normal.

[0008] Furthermore, when the horn receives the sweep frequency signal, the operating current of the horn is obtained through a current sensor, and the characteristic curve of the horn is obtained by combining the sweep frequency signal.

[0009] Furthermore, the output measured based on the logarithmic sweep frequency signal is convolved with the inverted signal of the logarithmic sweep frequency signal to obtain the impulse response of the horn, and a fast Fourier transform is performed to obtain the transfer function of the horn.

[0010] Furthermore, the transfer function of the horn is 1 / R, where R is the horn impedance.

[0011] Furthermore, based on the impedance equivalent circuit model of the speaker, the relationship between the impedance curve and temperature is obtained. The operating current is obtained in real time by superimposing a low-frequency signal, and the low-frequency impedance curve of the speaker is tested.

[0012] Furthermore, the low-frequency signal is a signal of 50-100 Hz that is outside the range of human hearing.

[0013] Furthermore, after superimposing the low-frequency signal, the overall curve offset is estimated based on the low-frequency impedance, the impedance value of the low-frequency point is extracted in real time as a reference point, and the low-frequency impedance is mapped to the offset model of the overall impedance curve based on experimental modeling or empirical curves.

[0014] Furthermore, based on the current impedance curve and speaker load status, the output impedance or frequency response characteristics of the power amplifier are dynamically adjusted to achieve adaptive matching between the speaker and the power amplifier.

[0015] Furthermore, when the impedance suddenly increases significantly, drops sharply, or an abnormal resonance peak appears, it is determined that the speaker is malfunctioning, triggering a fault warning.

[0016] The beneficial effects of this invention are: 1. Real-time monitoring of impedance curves.

[0017] 2. The impedance can be automatically adjusted based on the impedance curve.

[0018] 3. Through testing and feedback, ensure the speaker operates at its optimal performance. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a block diagram of the system under test; Figure 2 This is a schematic diagram of the impedance curve. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are merely illustrative and not intended to limit the invention.

[0022] The present invention provides a method for real-time monitoring of speaker impedance, the specific steps of which are as follows: 1. Sweep frequency measurement of the speaker's impedance curve: A sweep frequency signal or pink noise is sent to the speaker, and the speaker's operating current is obtained through a current sensor. After obtaining the current, calculations are performed between the current and the sweep frequency signal to obtain the speaker's characteristic curve. The specific principle is as follows: Assume the system under test is a linear time-invariant system, denoted as h(t). Let the system input signal be x(t) and the output signal be y(t). The system block diagram is as follows: Figure 1 As shown; Let the input x(n) be a logarithmic sweep frequency signal: Where U is the amplitude of the sweep frequency signal, f0 is the signal start frequency, and f s s is the sampling frequency, s is the scan time, T is the scan signal length, and n=1:T is the scan sequence. l =T / ln(f1 / f0), where f1 is the signal termination frequency.

[0023] The flip signal of the swept frequency signal x(n) is: f0 is the signal start frequency, f1 is the signal end frequency, A is the signal amplitude; N is the total number of sampling points for the swept frequency signal. From the definition of a swept frequency signal, we know that: ; Where * denotes convolution, The unit impulse function; According to such Figure 1 The system block diagram shown indicates that when the input is a swept frequency signal x, the system output is y = x * h. Convolving both sides of the above equation with each other, we get: Right now: Since the system output y can be measured, the system's impulse response h can be obtained by convolving the output y measured when the system inputs a logarithmic sweep frequency signal with the inverted signal of the logarithmic sweep frequency signal.

[0024] By performing a fast Fourier transform on the impulse response h, the system transfer function H = fft(h) can be obtained.

[0025] If the system is a loudspeaker, the input signal is the loudspeaker voltage U, and the output signal is the loudspeaker current I, then I = U / R, and the transfer function of the system can be regarded as 1 / R (R is the loudspeaker impedance). Then 1 / R can be measured by inputting a swept frequency signal using the method described above. The specific impedance curve is shown below. Figure 2 As shown.

[0026] 2. The impedance curve formula Z(f) = Re + j2πfLe + Z_mech(f) + Z_acoustic(f) shows that the impedance curve changes almost linearly with temperature. This means that the overall impedance curve variation can be estimated based on the impedance value in the 50-100Hz range. Therefore, during real-time testing, by superimposing a low-frequency signal (typically 50-100Hz) onto the power amplifier and obtaining the operating current of this low-frequency signal in real time, the speaker's low-frequency impedance curve can be tested. This superimposed sweep signal, because of its low frequency, is outside the audible range of the human ear and does not affect the normal use of the product.

[0027] 3. By analyzing the impedance curve, adjust the impedance between the power amplifier output and the speaker to achieve the best acoustic performance for the speaker.

[0028] 4. By calculating the impedance curve in real time, the system can determine whether the speaker is working properly. If any abnormality is found in the speaker (such as offset or burnt voice coil), the system will provide timely feedback.

[0029] Example: Step 1: Frequency sweep excitation and signal acquisition A wide-band (e.g., 20Hz–20kHz) sweep excitation signal is generated using a sweep frequency signal generator and then driven by a power amplifier module.

[0030] Meanwhile, a high-precision voltage and current sampling module is installed at the output of the power amplifier to synchronously sample the output voltage V(t) and current I(t).

[0031] The acquired voltage and current signals are segmented using window functions in a digital signal processing platform (such as FPGA, DSP, MCU, or host computer software). A short-time Fourier transform is performed on each segment of sampled data to extract the complex amplitude values ​​of voltage and current at each frequency point, thus obtaining the initial impedance curve of the loudspeaker (speaker enclosure).

[0032] Step 2: Embed low-frequency signals to monitor temperature effects Based on the equivalent impedance model of a loudspeaker: Z(f) = Re + j2πfLe + Z_mech(f) + Z_acoustic(f) Studies have shown that the change in impedance in the low-frequency range (such as 50Hz~100Hz) has a high linear mapping relationship with the impedance characteristics of the entire frequency band.

[0033] Therefore, in the frequency sweeping process, the method of the present invention continuously superimposes a low-frequency detection signal (such as 55Hz or 70Hz), which is outside the range of human hearing sensitivity (such as being imperceptible under background noise), and its amplitude is much lower than that of the main signal.

[0034] Step 3: The overall curve offset is estimated based on low-frequency impedance, and the impedance values ​​of low-frequency points (such as 50Hz, 60Hz, and 80Hz) are extracted in real time as reference points.

[0035] Based on experimental modeling or empirical curves, a shift model is used to map the low-frequency impedance to the overall impedance curve, thereby avoiding the computational burden caused by real-time calculation of the entire high-frequency band.

[0036] Example: A linear regression model can be used for fitting: Z(f)≈Zref(f)+k[Z(60Hz)−Zref(60Hz)] Zref (60Hz) represents the theoretical impedance at 60Hz, and Z (60Hz) represents the actual measured impedance at 60Hz. The difference between the two is then included in the final impedance value as the theoretical deviation.

[0037] Zt(100Hz)=Zref(100Hz)+k[Z(60Hz)−Zref(60Hz)] Where k is an empirical coefficient Step 4: Intelligent adjustment of power amplifier output characteristics Based on the current impedance curve and speaker load status, the output impedance or frequency response characteristics (such as gain, Q value, filtering parameters, etc.) of the power amplifier are dynamically adjusted to achieve adaptive matching between the speaker and the power amplifier.

[0038] This matching allows the speaker to operate under optimal acoustic load for extended periods, improving sound quality and lifespan.

[0039] This step can be achieved through a closed-loop control system, such as PID control, lookup table algorithms, or neural network parameter mapping.

[0040] Step 5: Output monitoring results and anomaly warnings The monitored impedance curves and their changing trends are transmitted to a host computer or APP interface for visualization.

[0041] A fault warning will be triggered if the following abnormal indicators are detected: Sudden and significant increase in impedance (such as a broken wire or open-circuited voice coil), sudden drop in impedance (such as a short circuit or burnt-out coil), abnormal resonance peak (such as voice coil displacement or diaphragm damage). The impedance curve can be plotted and output to a display terminal in real time, or transmitted to a remote device via a network interface.

[0042] The above embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method of monitoring the impedance of a loudspeaker in real time, characterized by, The method comprises the following steps: (1) According to the transfer function of the impedance of the loudspeaker, the impedance curve of the loudspeaker is measured by frequency sweeping; (2) Based on the relationship between the impedance curve and the temperature change, the low-frequency impedance curve of the loudspeaker is tested by superimposing the low-frequency signal; (3) Based on the low-frequency impedance curve, the impedance between the power amplifier output and the loudspeaker is adjusted, and it is judged whether the loudspeaker is normal.

2. The method of claim 1, wherein, When the loudspeaker receives the frequency sweeping signal, the working current of the loudspeaker is obtained through the current sensor, and the characteristic curve of the loudspeaker is obtained in combination with the frequency sweeping signal.

3. The method of claim 1, wherein, Based on the output measured by the logarithmic frequency sweeping signal, the impulse response of the loudspeaker is obtained by convolution with the inverted signal of the logarithmic frequency sweeping signal, and the transfer function of the loudspeaker is obtained by fast Fourier transform.

4. The method of claim 3, wherein, The transfer function of the loudspeaker is 1 / R, and R is the impedance of the loudspeaker.

5. The method of claim 1, wherein, Based on the impedance equivalent circuit model of the loudspeaker, the relationship between the impedance curve and the temperature change is obtained, the working current is obtained in real time by superimposing the low-frequency signal, and the low-frequency impedance curve of the loudspeaker is tested.

6. The method of claim 1, wherein, The low-frequency signal is a signal in the range of 50-100hz which is not in the audible range of human ears.

7. The method of claim 1, wherein, After superimposing the low-frequency signal, the overall curve offset is estimated based on the low-frequency impedance, the impedance value of the low-frequency point is extracted in real time as a reference point, and the low-frequency impedance is mapped to the offset model of the overall impedance curve based on experimental modeling or experience curve.

8. The method of claim 1, wherein, According to the current impedance curve and the load state of the loudspeaker, the output impedance or frequency response characteristic of the power amplifier is dynamically adjusted to realize the adaptive matching of the loudspeaker and the power amplifier.

9. The method of claim 1, wherein, When it is judged that the impedance suddenly rises greatly, the impedance suddenly drops or abnormal resonance peak appears, it is judged that the loudspeaker is abnormal, and fault warning is triggered.

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