Subwoofer丨 What are subwoofers? Why do you need subwoofers? How to choose a subwoofer?
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Update time : 2021-12-10 17:54:19
►What is a subwoofer?
The subwoofer is mainly responsible for the sound frequency band below 120Hz and is the cornerstone of the sound of the entire theater. With it, you can truly feel the atmosphere created by movie sound effects. Subwoofer is a common name or abbreviation for everyone, strictly speaking, it should be: super bass speaker. The audio audible to the human ear can be divided into subwoofer, bass, low midrange, midrange, midrange, treble, and ultratreble. To put it simply, the low frequency is the basic framework of sound, the middle frequency is the flesh and blood of the sound, and the high frequency is the detailed reflection of the sound. With the development of science and technology and the development of economic foundation, super bass and broadband have entered the audio world. The super bass is to strengthen the structure, and the broadband is to make the sound difference more clear. This time we are specifically talking about super bass.
►What is the role of the subwoofer?
The audibility of super bass is extremely limited by the human ear. On the contrary, it can be felt by other sense organs except the human ear. This is the shocking feeling! As far as the needs of the audio program source reflected by the sound and home theater are concerned, the super bass only exists in the specific program source and needs to be restored. With it, the restoration of the program source can be made more solid, without it, it seems to be less strength. For example, in the theater or in reality, we can feel the shock of the power and energy when the plane takes off, but if our home theater is not equipped with subwoofer speakers or the configuration is unreasonable, we cannot feel this shock.
►What is the working index of the subwoofer?
In principle, the working mode of the subwoofer and the loudspeaker is exactly the same, except that the diameter of the diaphragm is larger, generally 8 to 10 inches, and speakers for resonance are added. In terms of subwoofer evaluation indicators, the subwoofer is basically the same as the speaker. Regarding numerical requirements: the frequency response is generally below 200 Hz, the rated impedance is also about 4Ω, and the sensitivity is generally greater than 90 dB/W/m.
►What is the difference between an active subwoofer and a passive subwoofer?
Subwoofers can be roughly divided into active subwoofers and passive subwoofers. An active subwoofer refers to a subwoofer with a built-in power amplifier. When using it, there is no need to add an additional power amplifier, and it usually has a cylindrical shape. The disadvantage of this type of subwoofer is that the heat dissipation is not ideal and the power is not large, and the cylindrical shape usually produces unnecessary resonance phenomena, which reduces the controllability of the subwoofer. In contrast, a passive subwoofer requires an external power amplifier to work. The shape and power selection of this subwoofer can be more flexible, and the effect is naturally more ideal. In addition, active speakers can be further divided into sealed boxes and perforated boxes. The former is more suitable for deep symphony, and the latter is more suitable for pop music.
►How does the subwoofer work?
The internal power amplifier circuit divides the sound into several wavelength bands through the demultiplexer. The short and medium band (mid-high tone) is output to the satellite speaker, and the medium and long band (mid-bass) is output to the subwoofer. Generally, the subwoofer emits a long-wave sound of 20-200HZ, which is easy for people to hear. However, due to its long wavelength, it is difficult to distinguish the sound source location. Such long-wave sound is transmitted through the inverted phase hole and resonates with the satellite speaker box. The long-wave speaker and the weak bass generated by the satellite speaker speaker combine, and the satellite speaker speaker will re-enable the performance speaker to release the bass. As a result, the bass effect is very intense, and it makes people feel like it is emitted from a satellite speaker speaker. By now, you should basically understand the principle of the speaker. As for why the ultra-long-wave horn and the long-wave resonance horn are used, it must be understood with physical knowledge: satellites are weak bass, although they can be heard by people, but their waveform amplitude is small, that is, the energy is not large enough. If the long-wave technology is used, when the ultra-long wave generated by the speaker overlaps with it, they will be in phase through the phase inversion hole, and the ultra-long wave will be loaded on the satellite bass waveform. Because the speaker has a very powerful power, the energy increases sharply after loading, so that you feel very excited.
（The inverted tube is a part of the speaker. It is actually a hollow tube, usually made of PVC material, and some are metal tubes or cardboard tubes. The inverter tube communicates with the outside space through an exit on the outer surface of the sound box, and that exit is the inverter hole. Inverted tubes are only used for inverted speakers. The phase-inverted hole is used on phase-inverted speakers to expand low-frequency sound waves. It turns out that when the diaphragm of the woofer vibrates back and forth, it pushes the front and back air to vibrate to produce sound. If it is a closed speaker, this part of the sound wave energy radiated into the box is wasted. Such a waste is really a pity, so some people thought of opening a hole in the box to use the air energy radiated into the box. Use this part of the energy to drive the air inside the inverter tube to vibrate and produce sound, broaden the low frequency range and sense of volume, and increase the total output efficiency of the speaker.The inverter tube is not arbitrarily bored. The inner diameter and length of the inverter tube need to be designed in conjunction with the physical parameters of the horn and the size of the box, so that the vibration frequency of the air in the inverter tube matches the low-frequency vibration frequency of the speaker unit installed in the box to play a correct role.）
►How to choose a subwoofer?
►First look at the frequency response (Frequency Response) to ensure that the desired "complete low frequency" can be restored. The "lower limit" shows the sincerity of this product design. A qualified subwoofer must have a lower limit of 20 Hz (the lowest limit of human hearing) or lower.
►Second, look at the maximum output sound pressure level (Maximum SPL). This is a real test of strength. In the frequency response range, extremely low frequency (20～30Hz) can output more than 100dB, and low frequency (30～100Hz) can output more than 120dB. To become a qualified (big voice) subwoofer.
►Finally, you can look at the most intuitive part, the caliber and number of the woofer, to judge the strength of the subwoofer. 18 inches, generally used in flagship products, the strength is no problem, it can make you high. 15 inches, high quality goods, generally qualified and sufficient. 12 inches, the situation is the most complicated, the specific situation is analyzed in detail, there are strong players, and there are some who have no strength to fill the number. 10-inch, entry-level players, if you don't use 2 or more units, it is difficult to have enough strength. The 8-inch subwoofer is slightly inferior to the others. Unless it is a particularly high-quality six 8-inch units, the 8-inch cannon is only capable of sounding and swinging.
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