Limiter system and method for avoiding clipping distortion or increasing maximum sound level in active speakers

Abstract

To provide a limiter system and method for avoiding clipping distortion or increasing the maximum sound level of an active speaker.SOLUTION: The present disclosure provides a limiter system. The limiter system includes a first equalization filter, a low-pass filter, a first limiter, a high-pass filter, a second limiter, and a mixer. The limiter system provided by the present disclosure further includes a second equalization filter. An audio signal from a signal source first passes through the first equalization filter, the equalized signal is divided into two signals first, one signal is processed by the low-pass filter and the first limiter, the other signal is processed by the high-pass filter and the second limiter, and then the two processed signals enter the mixer to be mixed and outputted. The mixed output signal is subjected to second equalization filtering by the second equalization filter to avoid clipping distortion or to obtain a higher maximum sound level.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates generally to limiter systems and methods for active speakers, and more particularly, to limiter systems and methods that avoid clipping distortion and increase maximum sound levels in active speakers. [Background technology]

[0002] An audio signal is a carrier of regular sound wave frequency and amplitude variation information. Regular audio can be represented as a sound wave or sine wave. A sine wave contains three important parameters: frequency, amplitude, and phase, which also characterize an audio signal. Taking music as an example, human perception of sound frequency is represented as pitch. The higher the pitch, the higher the frequency. Amplitude reflects the amount of energy in a signal. A waveform signal with high amplitude is loud, and a waveform with low amplitude is quiet.

[0003] In an active speaker system, when the amplitude of the input signal is too large and the voltage exceeds the maximum voltage that the power amplifier can output after being amplified by the power amplifier, the peaks and dips of the output signal waveform will be clipped, resulting in audible clipping distortion. Since the bass performance of a speaker depends heavily on the size of the speaker, to obtain good bass performance with a limited speaker size, the low-frequency signal needs to be amplified as much as possible, so the low-frequency signal is more likely to reach the maximum voltage limit of the amplifier. In speaker design, a limiter is usually used to limit the maximum output voltage to a certain output level.

[0004] Therefore, limiters, also called clippers, are usually used in speaker systems to limit signals so that they do not exceed the maximum voltage limit of the system. A conventional limiter limits signals of all frequencies below the limiting threshold. However, since music is usually a dynamic broadband signal, the effect of this configuration is not very satisfactory. For example, when adding heavy bass, a low-frequency signal whose amplitude reaches or exceeds the maximum voltage limit may suddenly appear in the music, affecting the limiter and compressing signals of all frequencies equally. That is, when such a low-frequency signal appears, the volume of the higher frequency human voice suddenly decreases. When this low-frequency signal disappears, the volume of the human voice suddenly increases again. This is clearly undesirable.

[0005] Another conventional limiter may impose different limiting thresholds on different bands. Take a two-band limiter as an example, signals with frequencies close to the crossover frequency are removed by both the low-pass filter and the high-pass filter. When the amplitude of the input signal is large enough, the signal amplitude of the mixed signal in the mixer will exceed the limiting value, resulting in audible clipping distortion. Therefore, to avoid this clipping noise, it is necessary to set the limiter to a lower gain to reduce the maximum sound level of the speaker system. Summary of the Invention [Means for solving the problem]

[0006] In order to solve the above technical problem, the present disclosure provides a limiter system. The limiter system includes a first equalization filter, a low-pass filter, a first limiter, a high-pass filter, a second limiter, and a mixer. The limiter system provided by the present disclosure further includes a second equalization filter.

[0007] The audio signal from the signal source first passes through the first equalization filter, and the signal filtered by the first equalization filter is split into two signals, one signal passes through the low-pass filter and the first limiter, and the other signal passes through the high-pass filter and the second limiter. The cutoff frequencies of the low-pass filter and the high-pass filter are equal and equal to the crossover frequency. The signal lower than the crossover frequency output by the low-pass filter does not exceed the first limiting threshold after passing through the first limiter, and the high-pass signal higher than the crossover frequency output by the high-pass filter does not exceed the second limiting threshold after passing through the second limiter. Then the two filtered limited signals are input into the mixer and mixed.

[0008] In the limiter system provided by the present disclosure, the signal mixed by the mixer enters a second equalization filter where equalization filtering is performed.

[0009] Preferably, the first equalization filter and the second equalization filter have the same center frequency, Q value, and gain. The first equalization filter is a peak equalization filter, and the second equalization filter is a dip equalization filter.

[0010] When a small signal is input and both the first limiter and the second limiter do not trigger the limiting process, the first equalization filter and the second equalization filter are offset from each other.

[0011] The present disclosure also provides a limiting method. The limiting method includes the following steps: First, an equalization filter processes an audio input signal from a signal source by a first equalization filter. Here, the equalization filter processed signal is divided into two signals, and one signal is passed through a low-pass filter to obtain a signal lower than a crossover frequency. The signal lower than the crossover frequency is input to a first limiter to be limited. The other signal is passed through a high-pass filter to obtain a signal higher than a crossover frequency. The signal higher than the crossover frequency is input to a second limiter to be limited. Then, the two filtered limited signals are respectively sent to a mixer and mixed. The limiting method provided by the present disclosure further includes: an equalization filter processes an audio input signal mixed by the mixer by a second equalization filter.

[0012] When the input signal is relatively small and does not reach either the first limiting threshold of the first limiter or the second limiting threshold of the second limiter, the effects of the first equalization filter and the second equalization filter offset each other without affecting the acoustic effect of the input signal.

[0013] At least one advantage of the limiter system and method provided by the present disclosure is that it can avoid clipping distortion in active speakers and increase the maximum sound level of the active speakers. For example, the present application provides the following: (Item 1) a first equalization filter; a low-pass filter connected to the first equalization filter and outputting a signal lower than a crossover frequency; a high-pass filter connected to the first equalization filter and outputting a signal higher than the crossover frequency; a first limiter configured to receive and limit the signal below the crossover frequency; a second limiter configured to receive and limit the signal above the crossover frequency; a mixer configured to mix the signal below the crossover frequency limited by the first limiter with the signal above the crossover frequency limited by the second limiter; A limiter system for an active speaker, comprising: the limiter system further includes a second equalization filter configured to receive the signal output from the mixer and perform equalization filtering on the signal. The limiter system mentioned above. (Item 2) The limiter system described in the preceding item, wherein the center frequency of the first equalization filter is the same as the center frequency of the second equalization filter. (Item 3) The limiter system of any one of the preceding claims, wherein the first equalization filter increases a signal at the center frequency of the first equalization filter and the second equalization filter decreases a signal at the center frequency of the second equalization filter. (Item 4) 2. The limiter system of claim 1, wherein the absolute value of the increased gain of the first equalization filter is equal to the absolute value of the decreased gain of the second equalization filter. (Item 5) 2. The limiter system of claim 1, wherein the first equalization filter and the second equalization filter have the same Q value. (Item 6) 2. The limiter system of claim 1, wherein the first equalization filter is a peak equalization filter and the second equalization filter is a dip equalization filter. (Item 7) The limiter system of any one of the preceding claims, wherein the first limiter is configured to limit the signal below the crossover frequency at which the signal does not exceed a first limiting threshold, and the second limiter is configured to limit the signal above the crossover frequency at which the signal does not exceed a second limiting threshold. (Item 8) 2. The limiter system of claim 1, wherein the first limit threshold and the second limit threshold are the same. (Item 9) 2. The limiter system of claim 1, wherein the first limit threshold and the second limit threshold are different. (Item 10) 2. The limiter system of claim 1, wherein the first equalization filter and the second equalization filter are offset from each other when a low-pass signal does not reach the first limiting threshold and a high-pass signal does not reach the second limiting threshold. (Item 11) performing equalization filtering on the input signal with a first equalization filter; performing low pass filtering with a low pass filter to output a signal below a crossover frequency; outputting a signal higher than the crossover frequency through a high-pass filter; limiting the signal below the crossover frequency with a first limiter; limiting said signal above said crossover frequency with a second limiter; mixing the limited signal below the crossover frequency with the limited signal above the crossover frequency with a mixer; A method for limiting an active speaker, comprising: The limiting method further includes performing equalization filtering on the signal mixed by the mixer using a second equalization filter. The above restriction method. (Item 12) The limiting method according to the preceding item, further comprising setting a center frequency of the second equalization filter to be the same as a center frequency of the first equalization filter. (Item 13) 2. The limiting method of claim 1, further comprising: increasing a signal at the center frequency of the first equalization filter by the first equalization filter; and decreasing a signal at the center frequency of the second equalization filter by the second equalization filter. (Item 14) 2. The limiting method of claim 1, further comprising setting the increased gain of the first equalization filter and the decreased gain of the second equalization filter to have equal absolute values. (Item 15) The limiting method of any one of the preceding items, further comprising setting the second equalization filter and the first equalization filter to have the same Q value. (Item 16) 2. The limiting method according to claim 1, wherein the first equalization filter is a peak equalization filter and the second equalization filter is a dip equalization filter. (Item 17) The limiting method of any one of the preceding claims, further comprising: limiting the signal by the first limiter below the crossover frequency that does not exceed a first limiting threshold; and limiting the signal by the second limiter above the crossover frequency that does not exceed a second limiting threshold. (Item 18) The limiting method according to any one of the preceding items, further comprising setting the first limiting threshold and the second limiting threshold to be the same. (Item 19) The restriction method according to any one of the preceding items, further comprising setting the first restriction threshold and the second restriction threshold to be different. (Item 20) The limiting method of any one of the preceding items, further comprising offsetting the first equalization filter and the second equalization filter from each other when the first limiter and the second limiter do not perform limiting processing. (Summary) The present disclosure provides a limiter system. The limiter system includes a first equalization filter, a low-pass filter, a first limiter, a high-pass filter, a second limiter, and a mixer. The limiter system provided by the present disclosure further includes a second equalization filter. An audio signal from a signal source is first passed through the first equalization filter, and the equalized signal is first split into two signals, one signal is processed by the low-pass filter and the first limiter, and the other signal is processed by the high-pass filter and the second limiter. Then, the two processed signals are input to the mixer, mixed, and output. The mixed output signal is subjected to a second equalization filter process by the second equalization filter to avoid clipping distortion or obtain a higher maximum sound level.

[0014] These and / or other features, aspects and advantages of the present disclosure will become better understood from the following detailed description when taken in conjunction with the drawings, in which like reference numerals represent like components throughout. [Brief description of the drawings]

[0015] [Figure 1] 1 illustrates the structure of a limiter system according to an embodiment of the present disclosure. [Diagram 2] 2 shows electrical frequency response curves of output signals of a first limiter, a second limiter, and a mixer in the limiter system of FIG. 1; [Diagram 3] 2 shows the electrical frequency response curve of the output signal of the limiter system of FIG. 1 after adding a second equalization filter. [Figure 4] FIG. 4 is a partially enlarged view of FIG. [Diagram 5] 2 shows a comparative diagram of the electrical frequency response curves of the output signal of the limiter system shown in FIG. 1 before and after adding a second equalization filter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Where necessary, detailed embodiments of the present disclosure are disclosed herein. However, it should be understood that the disclosed embodiments are merely illustrative of the present disclosure, which may be embodied in various and alternative forms. The drawings are not necessarily to scale. Some features may be enlarged or minimized to show details of specific components. Therefore, specific structural and functional details disclosed herein should not be construed as limiting, but merely serve as a representative basis to teach those skilled in the art to employ the present disclosure in different ways.

[0017] The objective of the present disclosure is to provide a limiter system that can impose different limiting thresholds on different bands so that the maximum sound level of the system does not exceed the maximum voltage limit of the speaker system, thereby avoiding clipping distortion or increasing the maximum sound level of the active speaker system. To illustrate the limiter system of the present disclosure in which the audio signal from a signal source is divided into a low frequency band and a high frequency band for processing respectively, a limiter with two bands is taken as an example below.

[0018] As shown in Fig. 1, a limiter system 100 provided by the present disclosure is shown in Fig. 1, which includes a first equalization filter 110, a low-pass filter 120, a first limiter 130, a high-pass filter 140, a second limiter 150, and a mixer 160. In addition, the limiter system provided by the present disclosure further includes a second equalization filter 170.

[0019] As can be seen from Fig. 1, in the limiter system 100 shown in Fig. 1, an audio signal (e.g., music) from a signal source (not shown) first enters the first equalization filter 110 for equalization filter adjustment. When using an equalization filter, the parameters to be adjusted mainly include a center frequency fc, a quality factor Q, and a gain G. In the limiter system 100 of the present disclosure, the first equalization filter 110 is a filter having a center frequency f c_EQ1 In other words, at this moment, the gain G _EQ1is positive, but signals of other frequencies are not processed. This adjustment causes the signal to be adjusted to the center frequency f of the first equalization filter 110 while the other frequency levels remain unchanged. c_EQ1 can be increased to very high levels at the center frequency f c_EQ1 The loudness of the sound at the center frequency f of the first equalization filter 110 is greater than the sounds at other frequencies. c_EQ1 A relevant selection relates to the crossover frequency that splits the audio signal into a high band and a low band.

[0020] In order for the speaker to be able to impose limiting thresholds on different bands, the audio signal needs to be divided into different bands accordingly. In this disclosure, the input audio signal is divided into two bands, for example a low frequency band and a high frequency band.

[0021] In the case of a speaker, the signal generated by the signal source is, for example, an audio signal having an audible frequency. As known to those skilled in the art, the full audible frequency range is approximately between 20 Hz and 20 kHz. The limiter system provided by the present disclosure may be applied to an audio signal having an input signal within the full audible frequency range. For such an audio input signal, a low-pass filter and a high-pass filter may be used in the crossover to form two parts, one below the crossover frequency and one above the crossover frequency.

[0022] Take a case as an example. Considering that the frequency range of human voice is about 300 Hz to 3400 kHz, for example, in order to keep the human voice portion contained in the audio signal unchanged, the audio signal may be determined to have a high frequency band, for example, a portion higher than 300 Hz, and a low frequency band, for example, a portion lower than 300 Hz. Thus, referring to the limiter system 100 shown in FIG. 1, the cutoff frequency f of the low-pass filter 120 may be determined to be 100 Hz. _cutoff_Lp may be set to, for example, 300 Hz, and the cutoff frequency f _cutoff_Hpmay be set to, for example, 300 Hz. In this case, the low-pass filter 120 and the high-pass filter 140 are based on the same cutoff frequency. The cutoff frequency is the crossover frequency f _crossover For example, the crossover frequency in the limiter system 100 shown in FIG. _crossover =300Hz.

[0023] Next, referring back to FIG. 1, after the low pass filter 120 removes the signal above the crossover frequency, the remaining signal below the crossover frequency enters the first limiter 130. The first limiter 130 is a first limiting threshold Th _limiter_1 , i.e., has a maximum amplitude value. At this point, the signal below the crossover frequency reaches the first limiting threshold Th _limiter_1 If the input signal below the crossover frequency exceeds the first limiting threshold, the signal below the crossover frequency is generally compressed so as not to exceed the first limiting threshold. It can be seen that when the input signal below the crossover frequency is sufficiently large, the signal below the crossover frequency of the first limiter may be generally compressed, and when the input signal below the crossover frequency is small, the first limiter does not need to operate.

[0024] Correspondingly, as shown in FIG. 1, in the high frequency band portion, after the high pass filter 140 removes the signal below the crossover frequency, the retained high frequency signal enters the second limiter 150. The second limiter 150 has a second limiting threshold (clipping value) Th _limiter_2 At this moment, a signal higher than the crossover frequency reaches the second limiting threshold Th _limiter_2 If the input signal exceeds the second limiting threshold, the signal above the crossover frequency is generally compressed so as not to exceed the second limiting threshold. In other words, when the input signal above the crossover frequency is sufficiently large, the signal above the crossover frequency of the second limiter may be generally compressed, and when the input signal above the crossover frequency is small, the second limiter may not operate.

[0025] The signals limited by the first limiter and the second limiter enter the mixer. The mixer outputs audio signals with individual limiting processes in different bands, so the maximum limiting threshold is not set equally for all frequencies. In a dynamic broadband signal such as music, for example, when the bass is enhanced, a low-frequency signal with an amplitude that exceeds the maximum voltage limit suddenly appears in the music, and all frequency signals are compressed equally.

[0026] The limiter system 100 provided by the present disclosure further includes a second equalization filter 170. The second equalization filter 170 is connected downstream of the mixer and is a dip equalization filter. In the second equalization filter 170, the center frequency f C_EQ2 The audio signal is attenuated and the waveform is lowered, i.e., the gain G _EQ2 is now set to be negative, which may be seen as a reduction in gain, and other frequency signals are not processed.

[0027] The role of the second equalization filter 170 in the limiter system 100 of the present disclosure may be described with reference to FIG.

[0028] 2, the electrical frequency response curve of the output signal processed by the first limiter 130 is shown as 2B in FIG. 2. As shown in FIG. 2, for example, the limiting threshold Th _limiter_1 When is set to 0 dB, after being processed by the low-pass filter 120 and the first limiter 130, the cutoff frequency f _cutoff_Lp , i.e., the crossover frequency f _crossover Lower signals pass through, and the crossover frequency f _crossover It can be seen that higher frequency signals are suppressed. The electrical frequency response curve 2B of the signal output by the first limiter 130 after limiting is below 0 dB.

[0029] 2, the electrical frequency response curve of the output signal processed by the second limiter 150 is shown as 2C in FIG. _limiter_2 When the second limiter 150 is also set to 0 dB, the cutoff frequency f _cutoff_Hp That is, the crossover frequency f _crossover Higher signals pass through, and the crossover frequency f _crossover It can be seen that higher frequency signals are suppressed. The electrical frequency response curve 2C of the signal output by the second limiter 150 after limiting is below 0 dB.

[0030] 2 also shows electrical frequency response curves 2A of the audio signal processed and output by the low-pass filter 120 and the first limiter 130, and the other audio signal processed and output by the high-pass filter 140 and the second limiter 150 after being mixed in the mixer 160. As can be seen from FIG. 2, in the above example, the electrical frequency response curve of the output signal after mixing in the mixer 160 has a higher peak shape within the frequency range of 100 Hz to 1 kHz, which exceeds the threshold 0 dB of the first limiter 130 and the second limiter 150 of the limiter system 100.

[0031] The reason why the mixed signal exceeds the limit threshold is because the crossover frequency f _crossoverThis is because the audio signal adjusted by the first equalization filter 110 in is filtered out by both the low-pass filter 120 and the high-pass filter 140. However, in the actual filtering of a signal by the low-pass filter and the high-pass filter, the signal cannot be abruptly stopped at the cut-off frequency of each filter, but is attenuated to a certain extent at the cut-off frequency. For example, in the limiter system 100 of the present disclosure, after passing through the low-pass filter 120 and the first limiter 130, and then through the high-pass filter 140 and the second limiter 150, the electrical frequency response curves 2B and 2C of the two output signals cross each other with a certain slope at the crossover frequency. In this example, the two signals are attenuated to -6 dB at this moment, as shown in FIG. 2. Therefore, the amplitude of the superimposed signal after mixing the two signals in the mixer 160 is exactly 0 dB. Therefore, when the input signal continues to increase and exceeds −6 dB, the amplitude of the superimposed signal after mixing the two signals in the mixer 160 becomes large and exceeds the limiting threshold of the limiter, 0 dB.

[0032] The limiter system 100 of the present disclosure further includes a second equalization filter 170. The second equalization filter 170 has a center frequency f _EQ2 is the center frequency f of the first equalization filter 110. _EQ1 Same as crossover frequency f _crossover and the second equalization filter 170 is ideally set to have the same Q value and a different gain than the first equalization filter 110. That is, the center frequency f _EQ1 The degree of increase in the audio signal at the center frequency f _EQ2 corresponds to the degree of reduction in the audio signal at

[0033] 3 shows the electrical frequency response curve of the output signal processed by the second equalization filter 170. _crossover With a lower input signal and a crossover frequency f _crossoverWhen both higher signals are relatively small, the first limiter 130 and the second limiter 150 are not triggered to perform limiting processing, i.e., when the input signal is not high enough to trigger the limiter, the sound quality is not affected. In this case, the equalization filter processing in the second equalization filter 170 completely offsets the adjustment of the first equalization filter 110, and the electrical frequency response curve of the audio signal output by the second equalization filter 170 is a straight horizontal line. However, when the input audio signal gradually increases and the amplitude of the signal becomes large enough, the limiter is triggered, and if the first limiter and the second limiter are not triggered at the same time, the signal passing through the mixer does not form a standard "peak" shape near the crossover frequency, so that the non-uniformity as shown in FIG. 3 may occur after being attenuated by the second equalization filter 170, as can be imagined by those skilled in the art.

[0034] By observing the ordinate of FIG. 3 in a magnified manner in FIG. 4, it can be seen that when the second equalization filter 170 is used, the electrical frequency response curve of the output signal has a "peak-dip-peak" shape. When the limiting thresholds of the first limiter and the second limiter are set to be different, i.e., Th _limiter_1 ≠Th _limiter_2 When this is the case, the situation can become even more complicated.

[0035] 5 shows a comparison diagram of the electrical frequency response curves of the input signal and the output signal of the second equalization filter 170 in the limiter system 100 of the present disclosure. As shown in FIG. 5, the dotted line in the figure represents the electrical frequency response curve of the signal having the maximum input before being input to the second equalization filter 170. When the maximum output limiting threshold after the system amplification is 0 dB, it can be predicted that the electrical frequency response curve of the output signal has obvious clipping within the frequency range of 50 Hz to 2 kHz, resulting in large distortion.

[0036] 5 represents the electrical frequency response curve of the output signal with the maximum input after the equalization filtering process is performed by the second equalization filter 170. In contrast, after passing through the second equalization filter 170, the electrical frequency response curve of the signal forms a peak-dip-peak shape between 100 Hz and 1 kHz, so that the clipping distortion is greatly reduced even though the limiting threshold is set to 0 dB.

[0037] Therefore, in this disclosure, when the input signal voltage is high, the second equalization filter 170 outputs a crossover frequency f _crossover It can be seen that the voltage of the output signal close to 1000 Hz can be reduced. Therefore, it is possible to avoid clipping distortion in a wide range and increase the maximum sound pressure level of the speaker system. If the output signal does not reach the limit value of the limiter system, the first equalization filter 110 and the second equalization filter 170 can offset each other, so that the tone of the music from the signal source is not affected. In general, the system of the present disclosure can avoid some of the drawbacks of the conventional limiter, such as unstable human voice and clipping distortion. On the other hand, the limiter system and method of the present disclosure can increase the voltage utilization rate, making it possible to reliably obtain the maximum sound level without distortion.

[0038] Therefore, in summary, the various parameters included in the limiter system provided in the present disclosure may be summarized as having the following relationship: In the limiter system provided in the present disclosure, the low-pass filter and the high-pass filter have the same cutoff frequency f _cutoff_Lp =f _cutoff_Hp The cutoff frequency is the crossover frequency f _crossover The first limiter is the crossover frequency f _crossover and the second limiter is configured to limit the amplitude of a signal having a frequency lower than the crossover frequency f _crossover It is configured to limit the amplitude of higher frequency signals.

[0039] The first equalization filter is a peak equalization filter, and the second equalization filter is a dip equalization filter. The center frequencies of the first equalization filter and the second equalization filter are equal and are f C_EQ1 =f C_EQ2 , respectively, crossover frequency f _crossover Furthermore, the first equalization filter and the second equalization filter have the same Q value, Q _EQ1 =Q _EQ2 , the absolute value of the increased gain of the first equalization filter G _EQ1 and the reduced gain G of the second equalization filter _EQ2 are equal, i.e., f _Lp_cutoff =f _Hp_cutoff =f _crossover ; f _EQ1 =f _EQ2 ; Q _EQ1 =Q _EQ2 ; |G _EQ1 |=|G _EQ2 | Where: f _cutoff_Lp is the cutoff frequency of the low-pass filter, f _cutoff_Hp is the cutoff frequency of the high-pass filter. f _crossover is the crossover frequency. f _EQ1 is the center frequency of the first equalization filter, and f _EQ2 is the center frequency of the second equalization filter. Q _EQ1 is the Q value of the first equalization filter, and Q _EQ2 is the Q value of the second equalization filter. G _EQ1 is the gain of the first equalization filter, and G _EQ2 is the gain of the second equalization filter.

[0040] However, those skilled in the art can understand that the setting relationship of the above parameters is implemented in an ideal state. In fact, when using a speaker, a user often selects an audio signal from a signal source as a favorite sound effect, such as pop, rock, dance, classical, jazz, metal, or heavy bass, which is actually adjusted through various settings of the equalization filter to achieve a more ideal effect. On the other hand, a user can also manually adjust the gain and Q value of each frequency of the equalization filter, and the equalizer can be used to process input signals of different frequencies to correct and modify the speaker. In this case, when audio signals of other frequencies need to be adjusted, various changes in the Q value and gain and adjustments of adjacent frequencies may affect the crossover frequency of the present disclosure, which may be another reason for the unevenness of the electrical frequency response curve of the signal equalized by the added second equalization filter in the above description of the present disclosure. Therefore, those skilled in the art can imagine that when the first equalization filter and the second equalization filter are actually used, the center frequency, Q value, and gain of the two filters are not necessarily set equally. Rather, in order to get the perfect sound effect, different adjustments of the equalization filter should be set according to actual needs.

[0041] In summary, the limiter system and method provided by the present disclosure can reduce the voltage close to the crossover frequency after passing through the mixer by adding a second equalization filter when the input signal voltage is high, thereby significantly avoiding clipping distortion or increasing the maximum sound pressure level of the speaker system. Furthermore, if the input signal does not reach the limiting threshold of the limiter, the adjustments of the first equalization filter and the second equalization filter can be offset from each other without affecting the tone. In general, the limiter system and method of the present disclosure overcomes the shortcomings of conventional limiters, such as unstable human voice and audible clipping distortion. Furthermore, by using the limiter system and method provided by the present disclosure, the voltage utilization rate can be increased to ensure that the speaker plays at the maximum sound level without distortion.

[0042] For purposes of illustration, this disclosure has described embodiments, but the described embodiments are not exhaustive and are not limited to the embodiments disclosed herein. Numerous modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0043] Various aspects of the present disclosure may be embodied as a system, a method, or a computer program product. Accordingly, various aspects of the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment of a combination of software and hardware, all of which are generally referred to herein as a "module" or "system." Furthermore, any hardware and / or software technique, process, function, component, engine, module, or system described in this disclosure may be implemented as a circuit or group of circuits. Furthermore, various aspects of the present disclosure may take the form of a computer program product embodied in one or more computer-readable medium(s), having computer-readable program code embodied on the computer-readable medium(s).

[0044] Any combination of one or more computer readable media may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. The computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or apparatus, or any suitable combination thereof. More specific examples (non-exhaustive list) of computer readable storage media include each of an electrical connection with one or more communication lines, a portable computer floppy disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EEPROM or flash memory), an optical fiber, a portable CD-ROM, an optical storage device, a magnetic storage device, or any suitable combination thereof. In the context of this document, a computer readable storage medium may be any tangible medium that can contain or store a program for use by or in combination with an instruction execution system, device, or apparatus.

[0045] Aspects of the present disclosure are described above with reference to flowchart illustrations and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present disclosure. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, a special purpose computer, or other programmable data processing device to produce a machine. When the instructions are executed via the processor of the computer or other programmable data processing device, the function / action specified in the block or blocks of the flowchart illustrations and / or block diagrams may be realized. These processors may be, but are not limited to, a general purpose processor, a special purpose processor, a special purpose application processor, or a field programmable gate array.

[0046] The flowcharts and block diagrams in the drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, apparatus, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowcharts or block diagrams may represent a module, a section, or a portion of code, which includes one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions described in the blocks may occur in a different order than the order described in the drawings. For example, two blocks shown in succession may in fact be executed substantially simultaneously, or the blocks may sometimes be executed in the reverse order, depending on the functionality involved. It should also be noted that each block of the block diagrams and / or flowchart diagrams, and combinations of blocks in the block diagrams and / or flowchart diagrams, may be implemented by a dedicated hardware-based system or dedicated hardware and computer instructions that perform the specified functions or actions.

[0047] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the present disclosure may be contemplated without departing from the basic scope of the disclosure, the scope of which is determined by the appended claims.

Claims

1. a first equalization filter; a low-pass filter connected to the first equalization filter and outputting a signal lower than a crossover frequency; a high-pass filter connected to the first equalization filter and outputting a signal higher than the crossover frequency; a first limiter configured to receive and limit the signal below the crossover frequency; a second limiter configured to receive and limit the signal above the crossover frequency; a mixer configured to mix the signal below the crossover frequency limited by the first limiter with the signal above the crossover frequency limited by the second limiter; A limiter system for an active speaker, comprising: the limiter system further includes a second equalization filter configured to receive the signal output from the mixer and perform equalization filtering on the signal; the first limiter is configured to limit the signal below the crossover frequency without exceeding a first limiting threshold, and the second limiter is configured to limit the signal above the crossover frequency without exceeding a second limiting threshold; A limiter system, wherein the first limiting threshold and the second limiting threshold are the same.

2. 2. The limiter system of claim 1, wherein a center frequency of the first equalization filter is the same as a center frequency of the second equalization filter.

3. 2. The limiter system of claim 1, wherein the first equalization filter enhances a first signal at a center frequency of the first equalization filter and the second equalization filter attenuates a second signal at a center frequency of the second equalization filter.

4. 4. The limiter system of claim 3, wherein an absolute value of the increased gain of the first equalization filter is equal to an absolute value of the decreased gain of the second equalization filter.

5. The limiter system of claim 1 , wherein the first equalization filter and the second equalization filter have the same Q value.

6. 2. The limiter system of claim 1, wherein the first equalization filter is a peak equalization filter and the second equalization filter is a dip equalization filter.

7. 2. The limiter system of claim 1, wherein the first equalization filter and the second equalization filter are offset from each other when a low pass signal does not reach the first limiting threshold and a high pass signal does not reach the second limiting threshold.

8. performing equalization filtering on the input signal with a first equalization filter; performing low pass filtering with a low pass filter to output a signal lower than a crossover frequency; outputting a signal higher than the crossover frequency by a high pass filter; limiting the signal below the crossover frequency with a first limiter; limiting the signal above the crossover frequency with a second limiter; mixing the limited signal below the crossover frequency with the limited signal above the crossover frequency with a mixer; performing equalization filtering on the signal mixed by the mixer with a second equalization filter; by the first limiter, limiting the signal below the crossover frequency that does not exceed a first limiting threshold, and by the second limiter, limiting the signal above the crossover frequency that does not exceed a second limiting threshold; Setting the first limit threshold value and the second limit threshold value to be the same; A method for limiting an active speaker, comprising:

9. 9. The limiting method of claim 8, further comprising setting a center frequency of the second equalization filter to be the same as a center frequency of the first equalization filter.

10. 9. The limiting method of claim 8, further comprising: increasing a signal at a center frequency of the first equalization filter with the first equalization filter; and decreasing a signal at a center frequency of the second equalization filter with the second equalization filter.

11. 11. The limiting method of claim 10, further comprising setting the increased gain of the first equalization filter and the decreased gain of the second equalization filter to have equal absolute values.

12. The limiting method of claim 8 , further comprising setting the second equalization filter and the first equalization filter to have the same Q value.

13. 9. The limiting method of claim 8, wherein the first equalization filter is a peak equalization filter and the second equalization filter is a dip equalization filter.

14. 9. The limiting method of claim 8, further comprising: when the first limiter and the second limiter do not perform limiting, the first equalization filter and the second equalization filter are offset from each other.

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