Subwoofer room corrector

Abstract

The invention discloses a subwoofer room corrector, relates to the technical field of sound equipment, and can solve the problem of standing waves generated when a subwoofer is used in small and medium-sized rooms by a simple method. The subwoofer room corrector inputs the sizes in three directions in a room through a size input tool, converts the room sizes into standing wave frequencies through a built-in room size / standing wave frequency conversion circuit according to a standing wave frequency formula f = sound velocity / (2 * room size), and sends the standing wave frequencies to a built-in audio equalizer. The three standing wave frequency points are subjected to default appropriate level low voltage and Q value adjustment, so that the adjusted subwoofer signal source frequency response curve, the sound wave which is emitted by the subwoofer and has three standing wave sunken points, and the reflected standing wave of a room are combined sound waves which are corrected and tend to a smooth frequency response curve when reaching human ears.

Description

Technical field:

[0001] The invention relates to the technical field of audio, and in particular to a subwoofer room corrector for use in small and medium-sized rooms, which can be widely applied to sound reinforcement systems in small and medium-sized rooms. Background technology:

[0002] Subwoofers are an important part of high-quality sound reinforcement systems in small and medium-sized rooms. They are used to reproduce the low-frequency and ultra-low-frequency sound waves of the sound source as realistically as possible. When using a subwoofer in a small and medium-sized room, the human ear hears the superposition of the original sound waves emitted by the subwoofer and the sound waves reflected between the walls, floor, and ceiling of the room. This superposition result is very different from the original sound waves emitted by the subwoofer.

[0003] See attached Figure 1 , schematic diagram of the electro-acoustic conversion waveform of the subwoofer system without room standing wave correction.

[0004] The subwoofer signal source (1) outputs a low-frequency electrical signal (2) with a smooth frequency response curve waveform, which is input to the subwoofer (3) (here taking an active subwoofer as an example). The subwoofer amplifies and converts a sound wave (4) with a smooth frequency response curve and transmits it to the room (7). At the same time, the sound wave (4) emitted by the subwoofer will also generate reflected sound waves (5) through the action of the room (7). Among them, the reflected sound waves between the three opposite surfaces of the room (the roof and the ground, the left wall and the right wall, and the front wall and the back wall) cause standing waves fh (10), fw (9) and f L (8) The intensity is the highest. In the end, what the human ear hears is the superposition of the sound waves (6) emitted by the subwoofer (4) and the sound waves (5) reflected from the walls, floor, and ceiling of the room. The distortion caused by the standing waves in the room can be clearly seen.

[0005] Calculation formula based on relative surface size / reflected standing wave frequency in the room:

[0006] f = sound speed / wavelength = sound speed / (2 * opposite surface size) = 344 / (2 * opposite surface size)

[0007] = 172 / relative surface size, where the speed of sound is 344 m / s (default room temperature 20°C 1 atmosphere)

[0008] For most small and medium-sized rooms that use subwoofers, they are usually rectangular, and the dimensions of the three opposite sides (length, width and height) are approximately 2.8 meters to 8 meters. According to the above formula, we can conclude that the standing wave frequency points of the three opposite sides are around 20Hz (172 / 8=20.5) to 60Hz (172 / 2.8=61), which is just included in the output sound wave frequency response range of most subwoofers. Because the standing wave frequency is inversely proportional to the size of the room, the smallest of the three opposite sides is the height direction by default, and the standing wave frequency is the highest. The default frequency is fh(10). At the same time, because the height direction has the largest relative area, the large area and the close distance result in the strongest standing wave sound pressure. The second largest size is the width direction by default, and the standing wave frequency is also lower. The default frequency is fw(9). The relative area is the second largest, and the sound pressure intensity is in the middle. The largest size is the length direction by default, and the standing wave frequency is the smallest. The default frequency is f L (8), the relative area is the smallest and the sound pressure intensity is the smallest.

[0009] Because the sound pressure intensity of the three standing waves is much stronger than the sound pressure of other non-standing wave frequency sound waves, the human ear usually perceives the sound wave (6) synthesized from the uncorrected subwoofer sound wave (4) and the room reflection sound wave (5) as coming mostly from the three fixed standing wave frequencies fh (10), fw (9) and f L The sound of (8) is very monotonous and harsh, because the sound pressure in other non-standing wave frequency bands is relatively weak and is suppressed by the standing wave. In particular, the height dimension is usually the smallest, the fh(10) value is the highest, and the sound pressure is the strongest, which makes people feel that the subwoofer frequency is very high and cannot sink.

[0010] When a qualified subwoofer leaves the factory, its output sound wave frequency response curve (4) is smooth, but it is usually tested in an anechoic chamber, and the room environment factors after being put into market application will not appear. However, even the most qualified subwoofers will be affected by the room environment. Therefore, solving the impact of room standing waves on the use of subwoofers is the most important factor in the normal function of subwoofers. However, most subwoofers currently used in small and medium-sized rooms on the market have not solved the problem of standing wave room correction. This is also because most users lack the correct perceptual understanding of smooth subwoofer sound waves. When they hear the bang bang sound containing strong standing waves, they mistake it for the sound of a normal subwoofer. Especially in rooms with relatively small room sizes, the standing wave frequency is higher, the standing wave sound pressure is stronger, and the effect is worse. This makes most people think that subwoofers cannot express ultra-low frequencies in small rooms, and they cannot enjoy the pleasure of high-fidelity subwoofer sound waves. Even most audio-visual workers have not reasonably understood and solved this problem.

[0011] At present, the more professional and simple method to solve the standing wave problem in the subwoofer room is to start with the adjustment of the electrical signal at the front end of the subwoofer. Figure 2 , schematic diagram of the electro-acoustic conversion waveform of a subwoofer system using an audio equalizer for room standing wave correction.

[0012] First, according to the room size / standing wave frequency formula mentioned above, calculate the standing wave frequencies of the three opposite sides of the room, fh (10), fw (9) and f L (8), and then, on the audio equalizer (11), the parameters of the three frequency points are appropriately adjusted, including reducing the level, and the reduction value is sorted according to the sound pressure intensity of the three opposite surfaces, so that the electrical signal (12) output by the audio equalizer (11) to the subwoofer (3) is a frequency response curve corresponding to the depressions of the three standing wave frequency points. The levels of these three points are not reduced to zero during debugging, nor are they intended to completely eliminate the standing waves. They are only weakened, so that after the input levels of the three standing wave points are adjusted, the subwoofer outputs sound waves (13) with three depressions. Through the reflection effect of the room (7), the sound waves (14) reflected by the three opposite surfaces of the room still contain the corresponding three frequency values ​​fh (10), fw (9) and f L (8) standing waves, but the sound pressure of the standing waves formed at this time is relatively weakened compared to before correction. Then adjust the three standing wave points to the appropriate Q value, so that the three raised standing wave points formed by the room reflection and the three concave points corresponding to the subwoofer output are filled with each other. Finally, the sound wave frequency response curve (15) synthesized by the original sound wave (13) emitted by the subwoofer and the sound wave (14) reflected by the room tends to be smooth. After the synthesized sound wave frequency response curve (15) is adjusted to a better smoothness, a good listening effect will be obtained. At this time, the low frequency is clearly layered and powerful, and a large sound pressure is not required, which reduces disturbance to the public. Especially for the musical expression of low-frequency instruments, the effect is very good, and it also solves the misunderstanding of most people that subwoofers can only be used as background sound for war and martial arts films.

[0013] However, for the above method, because it is a combination of electronics and acoustics, firstly, people who work in audio and video rarely know the mathematical conversion formula between the standing wave frequency point in the room and the relative surface size of the room. Secondly, the standing wave frequency value needs to be calculated from the room size first, and then input into the audio equalizer, including the adjustment of the level and Q value. Most people think it is very troublesome, and non-audio and video professionals will not do it. Therefore, for a long time, the subwoofers used in small and medium-sized rooms, regardless of whether an audio equalizer is used at the front end, basically most of them have not made the correct room standing wave correction, and the original sound wave (4) effect of the subwoofer cannot be heard.

[0014] How to achieve standing wave correction of subwoofers in small and medium-sized rooms in a simple and easy way to achieve a wide range of market applications? The subwoofer room corrector of the present invention provides a solution. Summary of the invention:

[0015] The mathematical conversion formula between the standing wave frequency point in the room and the relative surface size of the room is the core theoretical basis for the use of this subwoofer room corrector function.

[0016] The subwoofer room corrector is essentially an audio equalizer. Based on the aforementioned professional method for solving the subwoofer room standing wave problem, we have simplified the method of using the audio equalizer to form a subwoofer room corrector (20), which is briefly described as follows:

[0017] a>Change from inputting three standing wave frequency values ​​to directly inputting three room size values, omitting the intermediate conversion step.

[0018] b> The manual adjustment settings of the attenuation level and Q value of the three standing wave frequencies are changed to the default values ​​in the audio equalizer. The manual adjustment setting steps of the level and Q value are omitted.

[0019] The operation of the subwoofer room corrector is now reduced to inputting the room size, changing the professional operation mode to a fool-proof operation mode.

[0020] The details are as follows, see the attached figure:

[0021] Since there is a mathematical conversion formula between the standing wave frequency point in the room and the relative surface size of the room, and most rooms are rectangular, we directly start from the length, width and height of the room, and input the length, width and height of the room to the subwoofer room corrector (20) through the input key panel (18), the room size input circuit (17) and the room size display (19). Then, the standing wave frequency point corresponding to the room size is converted according to the standing wave frequency formula through the room size / standing wave frequency conversion DSP circuit (16), and then the level attenuation and Q value of the three standing wave frequency points are appropriately adjusted through the built-in audio equalizer (11). In order to allow users of the subwoofer room corrector to quickly get started, we only retain the operation of inputting the three room sizes. As for the level attenuation adjustment and Q value adjustment of the internal audio equalizer (11) circuit after the three dimensions of the room are converted into three standing wave frequencies, it is difficult to establish a mathematical model of the attenuation level value and Q value constructed with the electroacoustic environment. This is because it contains many complex electroacoustic technical factors, including the electroacoustic parameters of the front-stage electronic equipment, the rear-stage power amplifier and the subwoofer, and the acoustic parameters of the room. Therefore, for the adjustment of these two parameters, we have made empirical simplifications. Based on our more than 40 years of experience in audio-visual work, the level attenuation adjustment of these three standing wave frequency points can be set by default to fh (10), -3dB; fw (9), -2dB; and f L(8), -1dB. The Q value of the three standing wave frequency points is set to 8 by default, and the upper limit of the subwoofer signal input terminal is 90Hz by default. 90Hz can be matched with the low frequency lower limit of 80Hz of the other mid-high frequency speakers in the vast majority of subwoofer systems. Through the above methods, the purpose of subwoofer room correction is basically achieved.

[0022] However, due to the different length, width and height ratios of various rectangular rooms and other complex electroacoustic factors, the smoothness of the final frequency response curve obtained by the above debugging method using the default values ​​of several parameters will have some deviations. Considering that users with higher technical requirements hope to adjust the frequency response curve to be smoother, we installed a USB interface (21) on the back of the device, which can be directly connected to a computer to use a monitor to make more detailed adjustments to the level and Q value of the standing wave frequency point, which is suitable for more professional needs.

[0023] The room dimensions can be input to the subwoofer room corrector either by button or remote control, including mobile phone APP operation. Description of the drawings:

[0024] Figure 1 This is a schematic diagram of the electroacoustic conversion waveform of the subwoofer system without room standing wave correction

[0025] Figure 2 This is a schematic diagram of the electroacoustic conversion waveform of a subwoofer system using an audio equalizer to correct room standing waves.

[0026] Figure 3 Schematic diagram of a subwoofer system using a subwoofer room corrector

[0027] Figure 4 is a front panel diagram of an embodiment of a subwoofer room corrector

[0028] Figure 5 Schematic diagram of the rear panel of an embodiment using a subwoofer room corrector

[0029] Figure 1 Middle: 1. Subwoofer signal source

[0030] 2. The low-frequency electrical signal with a smooth frequency response curve output by the subwoofer signal source

[0031] 3. Subwoofer

[0032] 4. The subwoofer amplifies and electroacoustically converts a sound wave with a smooth frequency response curve

[0033] 5. The sound wave waveform formed by the reflection of the sound waves output by the subwoofer on the six surfaces of the room

[0034] 6. The sound waves output by the subwoofer are superimposed on the sound waves reflected by the room, and the sound waves heard by the human ear

[0035] 7. Rooms with subwoofers

[0036] 8. Standing wave frequency f formed by reflection in the length direction of the room L (8)

[0037] 9. Standing wave frequency fw(9) formed by reflection in the room width direction

[0038] 10. Standing wave frequency fh(10) formed by reflection in the room height direction

[0039] Figure 2 Middle: 11. Audio Equalizer

[0040] 12. The waveform of the electrical signal output to the subwoofer after the audio equalizer adjusts the parameters of the three standing wave frequency points

[0041] 13. The final sound waveform emitted by the subwoofer after the audio equalizer adjusts the parameters of the three standing wave frequency points

[0042] 14. Sound waves generated by the reflection of the sound waves output by the subwoofer after correction in the room

[0043] 15. The sound waves output by the subwoofer after correction and the sound waves reflected by the room after the subwoofer output sound waves are synthesized to form the sound wave waveform heard by the human ear

[0044] Figure 3 Middle: 16. Room size / standing wave frequency conversion DSP circuit

[0045] 17. Room size input circuit

[0046] 18. Room size input button panel

[0047] 19. Room size display

[0048] 20. Subwoofer Room Corrector

[0049] 21. USB interface

[0050] Figure 4 Middle: 22. Room height dimensions shown on the display

[0051] 23. Room width dimensions shown on the display

[0052] 24. Room length dimensions shown on the display

[0053] 25. Room height dimension input adjustment button

[0054] 26. Room width dimension input adjustment button

[0055] 27. Room length dimension input adjustment button

[0056] 28. Click the confirmation button after entering the room dimensions. Example:

[0057] The following is a further description of the application embodiments of the present invention in conjunction with the accompanying drawings:

[0058] This embodiment only shows the key-type operation mode.

[0059] The circuit composition of the subwoofer room corrector (20) is shown in the figure frame. The room corrector (20) is composed of a room size input button panel (18), a room size input circuit (17), a room size display screen (19), a room size / standing wave frequency conversion DSP circuit (16), an audio equalizer (11) and a USB interface (21). The signal of the subwoofer signal source (1) is transmitted to the subwoofer room corrector (20) and connected to the pre-stage of the subwoofer (3) through the output end of the subwoofer room corrector (20). When the subwoofer room corrector is working, the length, width and height dimensions of the room where the subwoofer is used are input to the room size / standing wave frequency conversion DSP circuit (16) in the subwoofer room corrector through the room size input button panel (18) and the room size input circuit (17), and the input dimension data is displayed on the room size display screen (19), wherein the height dimension (22) displayed on the room size display screen is adjusted through the room height dimension adjustment button (25), the width dimension (23) displayed on the room size display screen is adjusted through the room width dimension adjustment button (26), and the length dimension (24) displayed on the room size display screen is adjusted through the room length dimension adjustment button (27). After the three dimensions are input, the confirmation button (28) is pressed.

[0060] The subwoofer, treated with a subwoofer room corrector, functions correctly in this room.

[0061] The USB interface (21) is connected to the audio equalizer (11), and the audio and video technician can use a computer through the USB interface (11) to use professional software to make more professional adjustments.

[0062] The subwoofer room corrector (20) can be an independent device, or it can be integrated into other audio pre-stage devices including the output subwoofer signal source (1), or integrated into a separate or combined active subwoofer amplifier, including the active subwoofer (3) shown in the figure, and then a room size display (19) is added to these devices. The room size input button panel (18) is a room size input device, and the room size input device can also be made into a remote control or mobile phone APP with a room display, which uses wireless method to send the input room size signal to the subwoofer room corrector (20) host and transmit it to the room size input circuit (17).

Claims

1. A subwoofer room corrector (20), characterized in that: The subwoofer room corrector (20) is composed of a room size input button panel (18), a room size input circuit (17), a room size display screen (19), a room size / standing wave frequency conversion DSP circuit (16), an audio equalizer (11), and a USB interface (21); the room size input circuit (17) is used to receive a room size signal input by the room size input button panel (18), and display the signal on the room size display screen (19); the room size / standing wave frequency conversion DSP circuit is used to convert the length, width, and height dimensions of the room sent by the room size input circuit into frequency values ​​of three standing wave frequency points and transmit them to the built-in audio equalizer; the built-in audio equalizer is used to adjust the level and Q value parameters of the three standing wave frequency points in the three-dimensional direction of the room for use with the subwoofer, and output the low-frequency signal after adjusting the three standing wave points to the subwoofer amplifier pre-stage.

2. A subwoofer room corrector according to claim 1, characterized in that: The room size input button panel (18) is a room size input device, through which the length, width and height of the room can be input into the room size input circuit; the room size input device can be a keypad, or a wireless transmitting and receiving device such as infrared or Bluetooth, including but not limited to a remote control or a mobile phone APP.

3. A subwoofer room corrector according to claim 1, characterized in that: The room size display screen (19) is used to display the length, width and height dimensions of the room input by the input device.

4. A subwoofer room corrector according to claim 1, characterized in that: The USB interface is connected to the audio equalizer, and you can use a computer through the USB interface to make fine professional adjustments to the audio equalizer.

5. A subwoofer room corrector according to claim 1, characterized in that: It can be an independent device comprising the content described in claim 1.

6. A subwoofer room corrector according to claim 1, characterized in that: It can be an embedded component containing the content described in claim 1, embedded in other independent audio devices, including but not limited to active subwoofers, audio pre-amplifiers and audio power amplifiers, and the embedded other independent audio devices contain the features of the content described in claim 1.

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