Compressor system and method for avoiding clipping distortion or increasing the maximum sound level of active loudspeakers

Abstract

The present invention provides a compression limiting system comprising a first equalizing filter, a low-pass filter and a first compressor, a high-pass filter and a second compressor, and a mixer. The compression limiting system further comprises a second equalizing filter. An audio signal from a signal source first passes through the first equalizing filter. The first equalized signal is then split into two paths: one path is processed by the low-pass filter and the first compressor, while the other path is processed by the high-pass filter and the second compressor. These two processed signals then enter the mixer for mixed output. The mixed output signals then pass through the second equalizing filter for a second equalization filtering to avoid clipping distortion or achieve a higher maximum sound level.

Description

Technical Field

[0001] The present invention generally relates to a compression limiting system and method for an active loudspeaker. More particularly, the present invention relates to a compression limiting system and method for avoiding clipping distortion and increasing the maximum sound level of an active loudspeaker. Background Art

[0002] An audio signal is a carrier of information about the regular frequency and amplitude variations of a sound wave. Regular audio signals can be represented by sound waves or sine waves. A sine wave has three key parameters: frequency, amplitude, and phase, which determine the characteristics of the audio signal. For example, in music, the human perception of sound frequency is expressed as pitch; higher frequencies produce higher pitches. Amplitude, on the other hand, reflects the signal's energy: high-amplitude waveforms produce louder signals, while low-amplitude waveforms produce quieter sounds.

[0003] In an active speaker system, when the input signal amplitude is excessive and, after amplification by the power amplifier, exceeds the maximum output voltage of the power amplifier, the peaks and bottoms of the output signal waveform will be clipped, resulting in audible clipping distortion. Since a speaker's bass performance is largely dependent on its size, achieving good bass performance within a limited speaker size requires maximizing low-frequency signals. This makes it more likely that low-frequency signals will reach the maximum voltage limit of the amplifier. A compressor is often used in speaker design to limit the maximum output voltage to a specific level.

[0004] Therefore, loudspeaker systems often employ compressors, also known as limiters, to limit the signal to within the system's maximum voltage limit. A conventional compressor limits all frequencies to a threshold value. However, since music is often a dynamic, broadband signal, this configuration is less than ideal. For example, when adding heavy bass, a low-frequency signal with an amplitude that reaches or exceeds the maximum voltage limit may suddenly appear in the music, impacting the compressor and causing all frequencies to be compressed equally. This means that when such a low-frequency signal appears, the volume of the higher-frequency vocals will suddenly drop. Then, as the low-frequency signal disappears, the vocals' volume suddenly increases—an undesirable situation.

[0005] Another conventional compressor applies different thresholds to different frequency bands. For example, in a two-band compressor, signals near the crossover frequency are filtered by both the low-pass and high-pass filters. If the input signal amplitude is sufficiently high, the amplitude of the signal after mixing by the mixer will exceed the threshold, resulting in audible clipping. To avoid this clipping noise, the compressor gain must be set to a lower value to reduce the maximum sound level of the speaker system. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a compression limiting system, which includes a first equalizing filter, a low-pass filter and a first compressor, a high-pass filter and a second compressor, and a mixer. The compression limiting system provided by the present invention also includes a second equalizing filter.

[0007] The audio signal from the signal source first passes through the first equalization filter. After the first equalization filter, the signal is split into two paths: one path passes through a low-pass filter and the first compressor, and the other path passes through a high-pass filter and a second compressor. The cutoff frequencies of the low-pass and high-pass filters are equal and equal to the crossover frequency. Signals below the crossover frequency output by the low-pass filter do not exceed the first compression threshold after passing through the first compressor, while signals above the crossover frequency output by the high-pass filter do not exceed the second compression threshold after passing through the second compressor. These two filtered and compressed signals then enter the mixer for mixing.

[0008] In the compression limiting system provided in the present invention, the signal mixed by the mixer enters the second equalization filter for equalization filtering.

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

[0010] When the input signal is relatively small and neither the first compressor nor the second compressor triggers the compression process, the first equalization filter and the second equalization filter cancel each other out.

[0011] The present invention also provides a compression method, which includes the following steps: first, equalizing and filtering an audio input signal from a signal source through a first equalizing filter, where the equalized filtered signal is divided into two paths, one of which is passed through a low-pass filter to obtain a signal below the crossover frequency. The signal below the crossover frequency is input to a first compressor for voltage limiting; the other signal is passed through a high-pass filter to obtain a signal above the crossover frequency, and the signal above the crossover frequency is input to a second compressor for voltage limiting. The two filtered and limited signals are then respectively sent to a mixer for mixing. The compression method provided by the present invention also includes equalizing and filtering the mixed signal output by the mixer through a second equalizing filter.

[0012] If the input signal is relatively small and neither reaches the first compression threshold value of the first compressor nor the second compression threshold value of the second compressor, the effects of the first equalization filter and the second equalization filter cancel each other out without affecting the sound effect of the input signal.

[0013] At least one advantage of the compression limiting system and method provided by the present invention is that it enables an active loudspeaker to avoid clipping distortion and also increases the maximum sound level of the active loudspeaker. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] These and / or other features, aspects, and advantages of the present invention will be better understood after reading the following detailed description with reference to the accompanying drawings, in which the components are not necessarily drawn to scale, emphasis instead being placed on illustrating the principles of the present invention. Furthermore, throughout the drawings, like characters represent like components, wherein:

[0015] Figure 1 shows the structure of a compression limiting system according to an embodiment of the present invention;

[0016] Figure 2 Shown Figure 1 The output signal electrical frequency response curves of the first compressor, the second compressor and the mixer in the compressor system;

[0017] Figure 3 Shown Figure 1 The output signal electrical frequency response curve of the compression limiting system after adding the second equalization filter;

[0018] Figure 4 Shown Figure 3 A partial enlarged view of

[0019] Figure 5 Shown Figure 1 The figure shows a comparison of the electrical frequency response curves of the output signal of the compression limiting system before and after the second equalization filter is added. DETAILED DESCRIPTION

[0020] As required, detailed embodiments of the present invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various forms and alternatives. The drawings are not necessarily drawn to scale; some features may be exaggerated or minimized to illustrate details of particular components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0021] The present invention is directed to a compression system that applies different compression thresholds in different frequency bands, thereby ensuring that the system's maximum sound level does not exceed the maximum voltage limit of the loudspeaker system, thereby preventing clipping distortion or increasing the maximum sound level of an active loudspeaker system. The following uses a two-band compressor as an example to illustrate the present invention's compression system, which separates an audio signal from a signal source into a low-frequency band and a high-frequency band for separate processing.

[0022] like Figure 1 As shown, Figure 1 1 shows a compression system 100 provided in the present invention, which includes a first equalizing filter 110, a low-pass filter 120, a first compressor 130, a high-pass filter 140, a second compressor 150, and a mixer 160. In addition, the compression system provided by the present invention also includes a second equalizing filter 170.

[0023] Depend on Figure 1 visible, Figure 1 In the illustrated compression system 100, an audio signal (e.g., music) from a signal source (not shown) first enters a first equalization filter 110 for equalization filter tuning. The parameters to be tuned for the equalization filter mainly include the center frequency fc, the quality factor Q, and the gain G. In the compression system 100 of the present invention, the first equalization filter 110 makes the center frequency fc be equal to the value of the first equalization filter 110. c_EQ1 The signal peak shape is improved, that is, the gain G _EQ1 This adjustment can make the signal at the center frequency f of the first equalization filter 110 c_EQ1 Gain is obtained so that a very high level can be obtained, while the levels of other frequencies remain unchanged, resulting in the center frequency f c_EQ1 The sound at the frequency is louder than the sound at other frequencies. The center frequency f of the first equalization filter 110 we are concerned about is c_EQ1 The selection is related to the crossover frequency that divides the audio signal into two frequency bands, high and low.

[0024] In order to enable the speaker to apply compression thresholds in different frequency bands respectively, the audio signal needs to be divided into different frequency bands accordingly. In the present invention, the input audio signal is divided into two frequency bands, for example, a low frequency band and a high frequency band.

[0025] For a loudspeaker, the signal generated by the signal source is an audio signal having, for example, an audio frequency. As known to those skilled in the art, the full audio frequency range is approximately between 20 Hz and 20 kHz. The compression limiting system provided by the present invention can be applied to audio signals whose input signals fall within the full audio frequency range. For such an audio input signal, a low-pass filter and a high-pass filter can be used to perform frequency division to form two components: a signal below the crossover frequency and a signal above the crossover frequency.

[0026] For example, in order to avoid affecting the part of the human voice contained in the audio signal, considering that the frequency range of the human voice is approximately from 300Hz to 3400kHz, the audio signal can be divided into the part above 300Hz, for example, in the high frequency band, and the part below 300Hz, for example, in the low frequency band. Figure 1 In the compression system 100 shown, the cutoff frequency f of the low-pass filter 120 can be set to_cutoff_Lp The cutoff frequency f of the high-pass filter 140 is set to 300 Hz, for example. _cutoff_Hp In this case, the low-pass filter 120 and the high-pass filter 140 are based on the same cutoff frequency, which is called the crossover frequency f _crossover , for example in Figure 1 In the illustrated compression system 100, the crossover frequency is set at, for example, f _crossover =300Hz.

[0027] Next, refer to Figure 1 After the low-pass filter 120 filters out the signal higher than the crossover frequency, the remaining signal lower than the crossover frequency enters the first compressor 130. The first compressor 130 has a first compressor threshold value Th _limiter_1 , that is, the maximum amplitude value, if the signal below the crossover frequency exceeds the first pressure limit threshold value Th _limiter_1 , the signal below the crossover frequency will be compressed as a whole to a value not exceeding the first compression threshold. Thus, when the input signal below the crossover frequency is large enough, the signal below the crossover frequency may be compressed as a whole in the first compressor, while when the input signal below the crossover frequency is small, the first compressor may not work.

[0028] Correspondingly, in the high frequency band, such as Figure 1 As shown, after the high-pass filter 140 filters out the signal below the crossover frequency, the retained high-frequency signal enters the second compressor 150. The second compressor 150 has a second compressor threshold value (amplitude limit value) Th _limiter_2 If the signal higher than the crossover frequency exceeds the second pressure limit threshold Th _limiter_2 , the signal above the crossover frequency will be compressed as a whole until it does not exceed the second compression threshold. In other words, when the input signal above the crossover frequency is large enough, the signal above the crossover frequency may be compressed as a whole in the second compressor, while when the input signal above the crossover frequency is small, the second compressor may not work.

[0029] After being compressed by the first and second compressors, the signals are fed into the mixer. The mixer outputs audio signals that have been compressed in different frequency bands, so the maximum compression threshold is not set equally across all frequencies. For dynamic, wideband signals like music, this prevents the situation where, for example, when enhancing bass, low-frequency signals might suddenly appear in the music with amplitudes exceeding the maximum voltage limit, resulting in equal compression across all frequencies.

[0030] The compression limiting system 100 provided by the present invention further includes a second equalization filter 170. The second equalization filter 170 is connected downstream of the mixer and is a valley-shaped equalization filter. In the second equalization filter 170, the center frequency f C_EQ2 The waveform of the audio signal at the position decreases due to attenuation, that is, the gain G of the second equalization filter 170 is _EQ2 It is set to a negative number, so it can also be regarded as a reduction in gain, while other frequency signals are not processed.

[0031] The role of the second equalization filter 170 in the compression limiting system 100 of the present invention can be combined with Figure 2 Provide explanation.

[0032] refer to Figure 2 The output signal electrical frequency response curve after being processed by the first compressor 130 is as follows: Figure 2 As shown in 2B. Figure 2 As shown, for example, the compression threshold value Th of the first compressor 130 is set to _limiter_1 When it is set to 0dB, it can be seen that after being processed by the low-pass filter 120 and the first compressor 130, the cut-off frequency f _cutoff_Lp , that is, the crossover frequency f _crossover The signal is passed through, while the signal above the crossover frequency f _crossover The frequency signal is suppressed, and the electrical frequency response curve 2B of the signal output by the first compressor 130 after compression is no greater than 0 dB.

[0033] Also refer to Figure 2 The output signal electrical frequency response curve after the second compressor 150 is processed is as follows: Figure 2 For example, the compression threshold value Th of the second compressor 150 is set to _limiter_2 When it is also set to 0dB, it can be seen that after being processed by the high-pass filter 140 and the second compressor 150, the cut-off frequency f _cutoff_Hp , that is, the crossover frequency f _crossover The signal is passed through, while the signal below the crossover frequency f _crossover The frequency signal is suppressed, and the electrical frequency response curve 2C of the signal output by the second compressor 150 after compression is no greater than 0 dB.

[0034] Figure 2 Also shown is an electrical frequency response curve 2A of an audio signal processed and output by the low-pass filter 120 and the first compressor 130 and another audio signal processed and output by the high-pass filter 140 and the second compressor 150 after mixing in the mixer 160. Figure 2It can be seen that in the above example, the electrical frequency response curve of the signal output after mixing in the mixer 160 has a high peak shape in the frequency range of 100 Hz-1 kHz, which exceeds the threshold value 0 dB of the first compressor 130 and the second compressor 150 in the compressor system 100.

[0035] The reason why the mixed signal exceeds the compression threshold is that the audio signal tuned by the first equalization filter 110 is at the crossover frequency f _crossover The signal is filtered by the low-pass filter 120 and the high-pass filter 140 at the same time. However, in practice, the low-pass filter and the high-pass filter cannot filter the signal abruptly at the cutoff frequency of each filter. Instead, the signal is attenuated to a certain extent at the cutoff frequency. For example, in the compression system 100 of the present invention, after passing through the low-pass filter 120 and the first compressor 130 and the high-pass filter 140 and the second compressor 150 respectively, the electrical frequency response curves 2B and 2C of the two output signals intersect at a certain slope at the crossover frequency. In this example, both signals are attenuated to -6dB at this time, as shown in FIG. Figure 2 As shown in Figure 1, the amplitude of the signal generated by mixing the two signals in mixer 160 is exactly 0 dB. Therefore, when the input signal continues to increase and exceeds -6 dB, the amplitude of the signal generated by mixing the two signals in mixer 160 is even higher, exceeding the compressor threshold of 0 dB.

[0036] The compression limiting system 100 of the present invention further includes a second equalization filter 170. The center frequency f _EQ2 Set to the center frequency f of the first equalization filter 110 _EQ1 Same as the crossover frequency f _crossover equal or close to, and ideally, the second equalization filter 170 is set to have the same quality factor as the first equalization filter 110 and the opposite gain. That is, in the first equalization filter 110, the audio signal at the center frequency f _EQ1 The amount of improvement at the center frequency f is determined accordingly in the second equalization filter 170. _EQ2 How much it dropped.

[0037] Figure 3 The electrical frequency response curve of the output signal after being processed by the second equalization filter 170 is shown. _crossover The signal is higher than the crossover frequency f _crossoverThe signals are relatively small and will not trigger the first compressor 130 and the second compressor 150 to perform limiting processing, that is, the sound quality is not affected when the input signal does not reach a level sufficient to trigger the compressor. In this case, the equalization filtering in the second equalization filter 170 completely offsets the tuning of the first equalization filter 110, and the electrical frequency response curve of the audio signal output by the second equalization filter 170 should be a straight horizontal line. However, those skilled in the art can imagine that when the input audio signal gradually increases and the amplitude of the signal is large enough, the compressor will be triggered, and if the first compressor and the second compressor are not triggered at the same time, the signal after passing through the mixer does not form a standard "peak" shape near the crossover frequency, so that after attenuation through the second equalization filter 170, the following may appear. Figure 3 Unevenness shown.

[0038] Figure 4 Will Figure 3 Zooming in on the middle vertical axis reveals that the signal frequency response curve after the second equalization filter 170 is output has a "peak-valley-peak" shape. _limiter_1 ≠Th _limiter_2 , the situation may be more complicated.

[0039] exist Figure 5 FIG. 1 shows a comparison of the electrical frequency response curves of the input signal and the output signal of the second equalization filter 170 in the compression limiting system 100 of the present invention. Figure 5 As shown in the figure, the dotted line represents the electrical frequency response curve of the signal with maximum input before inputting the second equalization filter 170. If the maximum output voltage limit threshold value after the system is amplified is 0dB, it can be expected that such an output signal electrical frequency response curve will show obvious clipping in the frequency range of 50Hz-2kHz, resulting in greater distortion.

[0040] Figure 5 The middle dotted line represents the electrical frequency response curve of the output signal with maximum input after equalization and filtering by the second equalization filter 170. In comparison, after passing through the second equalization filter 170, the electrical frequency response curve of the signal forms a peak-valley-peak shape between 100 Hz and 1 kHz. Therefore, even if the compression threshold value is set to 0 dB, its clipping distortion is greatly reduced.

[0041] It can be seen that in the present invention, if the input signal voltage is high, the second equalization filter 170 can reduce the output signal after the mixer 160 is mixed at the divided frequency f _crossovervoltage nearby. Therefore, clipping distortion can be avoided over a large range, or the maximum sound pressure level in the speaker system can be increased. If the output signal does not reach the limit value of the compression limiter system, the first equalizing filter 110 and the second equalizing filter 170 can cancel each other out, thereby having no effect on the timbre of the music from the signal source. In general, the system of the present invention can avoid some of the shortcomings of conventional compressors, such as unstable vocal volume and clipping distortion. On the other hand, the compression limiter system and method of the present invention can increase voltage utilization to ensure that the maximum sound level is obtained without distortion.

[0042] Therefore, in summary, the various parameters involved in the compression system provided in the present invention can be summarized as having the following relationship: In the compression system provided in the present invention, the low-pass filter and the high-pass filter are based on the same cut-off frequency f _cutoff_Lp =f _cutoff_Hp , the cut-off frequency is called the crossover frequency f _crossover The first compressor is used to limit the frequency below the crossover frequency f _crossover The second compressor is used to limit the frequency higher than the crossover frequency f _crossover The amplitude of the signal.

[0043] The first equalization filter is a peak equalization filter, and the second equalization filter is a valley equalization filter. The center frequencies of the first equalization filter and the second equalization filter are equal, f C_EQ1 =f C_EQ2 And respectively with the frequency division frequency f _crossover Moreover, the first equalization filter and the second equalization filter have the same quality factor Q _EQ1 =Q _EQ2 , and the boost gain G of the first equalization filter _EQ1 and the second equalization filter's reduced gain G _EQ2 The absolute values ​​are equal, that is:

[0044] f _Lp_cutoff =f _Hp_cutoff =f _crossover ;

[0045] f _EQ1 =f _EQ2 ;

[0046] Q _EQ1 =Q _EQ2 ;

[0047] |G _EQ1 |=|G _EQ2 |

[0048] in:

[0049] f _cutoff_Lpis the cutoff frequency of the low-pass filter, and f _cutoff_Hp is the cutoff frequency of the high-pass filter;

[0050] f _crossover is the crossover frequency;

[0051] f _EQ1 is the center frequency of the first equalization filter, and f _EQ2 is the center frequency of the second equalization filter;

[0052] Q _EQ1 is the quality factor of the first equalization filter, and Q _EQ2 is the quality factor of the second equalization filter;

[0053] G _EQ1 is the first equalization filter gain, and G _EQ2 is the second equalization filter gain.

[0054] However, those skilled in the art will appreciate that the above parameter settings are implemented under ideal conditions. In practice, when using a loudspeaker, users often select their preferred audio effects from the signal source, such as pop, rock, dance, classical, jazz, metal, or heavy bass. This is achieved by tuning the equalizer filter settings differently, hoping to achieve a more ideal sound. Alternatively, users can manually adjust the gain and quality factor of each frequency at the equalizer filter. By processing input signals at different frequencies using the equalizer, the loudspeaker can be compensated and modified. In this case, when tuning audio signals at other frequencies, changes in the quality factor and gain, as well as tuning of adjacent frequencies, may affect the crossover frequency in the present invention. This is another reason why the frequency response curve of the signal after equalization by the second equalizer filter mentioned earlier in the present invention exhibits unevenness. Therefore, those skilled in the art will appreciate that, in practice, the center frequencies, quality factors, and gains of the first and second equalizer filters are not necessarily set to be equal. To achieve a perfect sound effect, the various tuning settings of the equalizer filters should be set according to actual needs.

[0055] In summary, the compression limiting system and method provided by the present invention can reduce the voltage near the crossover frequency after passing through the mixer by adding a second equalizing filter when the input signal voltage is high. This can avoid clipping distortion to a large extent, or increase the maximum sound pressure level of the speaker system. Moreover, if the input signal does not reach the compression threshold value of the compressor, the tuning of the first equalizing filter and the second equalizing filter can offset each other and have no effect on the timbre. In general, the compression limiting system and method of the present invention overcome the defects of traditional compressors, such as unstable human voice volume, audible clipping distortion, etc. In addition, by using the compression limiting system and method provided by the present invention, the voltage utilization rate can be increased to ensure that the speaker plays at the maximum sound level without distortion.

[0056] For illustrative purposes, the present disclosure has provided descriptions of embodiments, but the described embodiments are not exhaustive or limited to the embodiments disclosed herein. Without departing from the scope and spirit of the described embodiments, those skilled in the art will appreciate that there are many modifications and variations.

[0057] Aspects of the present embodiment may be embodied as systems, methods or computer program products. Therefore, aspects of the present disclosure may take the form of a complete hardware embodiment, a complete software embodiment (including firmware, resident software, microcode, etc.) or a combination of software and hardware embodiments, which may generally all be referred to herein as "modules" or "systems." Additionally, any hardware and / or software technology, process, function, component, engine, module or system described in the present disclosure may be implemented as a circuit or a group of circuits. Additionally, aspects of the present disclosure may take the form of a computer program product embodied in one or more computer-readable media, which embodies computer-readable program code thereon.

[0058] Any combination of one or more computer-readable media can be utilized. Computer-readable media can be computer-readable signal media or computer-readable storage media. Computer-readable storage media can be, for example, but not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or apparatuses, or any suitable combination of the foregoing. More specific examples (non-exhaustive list) of computer-readable storage media can include the following: an electrical connection with one or more wires, a portable computer floppy disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable CD-ROM, an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer-readable storage medium can be any tangible medium that can contain or store a program for use by or in conjunction with an instruction execution system, device, or apparatus.

[0059] Aspects of the present disclosure are described above with reference to the flowchart illustrations and / or block diagrams of the methods, devices (systems) and computer program products according to the embodiments of the present disclosure. It will be understood that each block of the flowchart illustrations and / or block diagrams and the combination of the blocks in the flowchart illustrations and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer or other programmable data processing device to produce a machine. The instructions can implement the functions / actions specified in the flowchart and / or block diagram block or multiple blocks when executed by the processor of the computer or other programmable data processing device. These processors can be, but are not limited to, general-purpose processors, special-purpose processors, special application processors or field programmable gate arrays.

[0060] The flowcharts and block diagrams in the figures illustrate the architecture, functionality and operation of possible implementations of the systems, methods and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagram can represent a module, segment or portion of a code, and the code includes one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functionality described in the block may not occur in the order described in the figure. For example, two blocks shown in succession can actually be executed substantially simultaneously, or the blocks can sometimes be executed in reverse order depending on the functionality involved. It should also be noted that each block of the block diagram and / or flowchart illustration and the combination of the blocks in the block diagram and / or flowchart illustration can be implemented by a system based on dedicated hardware that performs a specified function or action or a combination of dedicated hardware and computer instructions.

[0061] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope of the disclosure is determined by the claims that follow.

Claims

1. A compression limiting system for an active loudspeaker, comprising: a first equalization filter; a low-pass filter connected to the first equalizing filter and outputting a signal lower than the crossover frequency; a high-pass filter connected to the first equalizing filter and outputting a signal higher than the crossover frequency; a first compressor configured to receive and limit the signal having a frequency lower than the crossover frequency; a second compressor configured to receive and limit the signal having a frequency higher than the crossover frequency; a mixer configured to mix the signal below the crossover frequency limited by the first compressor and the signal above the crossover frequency limited by the second compressor, The compression limiting system further includes a second equalization filter configured to receive and equalize the signal output from the mixer. The first compressor is configured to make the signal below the crossover frequency not exceed a first compressor threshold value, and the second compressor is configured to make the signal above the crossover frequency not exceed a second compressor threshold value, and The first compression threshold value and the second compression threshold value are the same. 2 . The compression limiting 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 . The compression limiting system of claim 1 , wherein the first equalization filter boosts a signal at a center frequency of the first equalization filter, and the second equalization filter drops a signal at a center frequency of the second equalization filter. 4 . The compression limiting system of claim 3 , wherein the absolute values ​​of the boost gain of the first equalization filter and the drop gain of the second equalization filter are equal. 5 . The compression limiting system of claim 1 , wherein the first equalization filter and the second equalization filter have the same quality factor. 6 . The compression limiting system according to claim 1 , wherein the first equalization filter is a peak equalization filter, and the second equalization filter is a valley equalization filter. 7 . The compression system of claim 1 , wherein when the first compressor and the second compressor are not performing compression processing, the first equalization filter and the second equalization filter cancel each other.

8. A compression limiting method for an active loudspeaker, the method comprising the following steps: equalizing and filtering the input signal through a first equalizing filter; The signal below the crossover frequency is output through low-pass filtering; The signal with a frequency higher than the crossover frequency is output through a high-pass filter; limiting the signal below the crossover frequency by a first compressor; limiting the signal having a frequency higher than the crossover frequency by a second compressor; The mixer mixes the signal whose compression limit is lower than the crossover frequency with the signal whose compression limit is higher than the crossover frequency. The compression limiting method further comprises equalizing and filtering the signal mixed by the mixer through a second equalizing filter. Wherein, the compression method further includes: The first compressor is used to ensure that the signal below the crossover frequency does not exceed a first compressor threshold value; Using the second compressor to limit the signal higher than the crossover frequency to not exceed a second compressor threshold value; and The first compression threshold value and the second compression threshold value are set to be the same. 9 . The compression limiting method according to 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. The compression limiting method according to claim 8, further comprising boosting the signal at the center frequency of the first equalizing filter by the first equalizing filter, and reducing the signal at the center frequency of the second equalizing filter by the second equalizing filter. 11 . The compression limiting method according to claim 10 , further comprising setting the boost gain of the first equalizing filter to have an absolute value equal to the drop gain of the second equalizing filter. 12 . The compression method according to claim 8 , further comprising setting the second equalization filter to have the same quality factor as the first equalization filter. 13 . The compression limiting method according to claim 8 , wherein the first equalization filter is a peak equalization filter, and the second equalization filter is a valley equalization filter.

14. The compression method according to claim 8, further comprising: when the first compressor and the second compressor do not perform compression processing, the first equalization filter and the second equalization filter cancel each other.

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