Subwoofer

In a home theater system, subwoofer is indispensable. The speakers used for the subwoofer channel are called subwoofers or subwoofers.
The bass frequency of this kind of speaker is generally below 160Hz, and some requirements are below 120Hz. The upper limit frequency of this kind of speaker is generally around 160Hz, and its lower limit frequency is generally 20~60Hz, and its frequency range is adjustable (some are continuous adjustment, some are step adjustment). However, the lower limit frequency (-3dB frequency point) of many subwoofer speakers is less than 20Hz, or even less than 40Hz, so such speakers may not be able to reproduce subwoofers, but it is customary to call such speakers as subwoofers. Speakers.

The -3dB frequency point is common in audio systems and can be illustrated by the frequency response characteristic curve shown in Figure 5-79. The frequency point where the curve in the figure drops to -3dB is called -3dB frequency point, of which 20Hz is called the lower limit frequency and 180Hz is called the upper limit frequency. When the frequency is lower than the lower limit frequency and higher than the upper limit frequency, it is regarded as unresponsive due to its poor response.

 
Types of subwoofers
Subwoofer speakers can be divided into two categories: active and passive. Among them, active speakers are divided into ordinary active subwoofer speakers and active balanced subwoofer speakers. Active subwoofer speakers are also called active subwoofer speakers, and passive subwoofer speakers are also called passive subwoofer speakers.
Passive subwoofer speakers. The speaker cabinet itself has been designed to have the ability to reproduce subwoofers, and there is no special requirement for the power amplifier that drives it. It can be used as long as the power is sufficient and impedance matching, and it can be directly connected to a stereo power amplifier.
A simple frequency divider composed of coils and capacitors is installed inside this subwoofer speaker, and there are 2 or 3 crossover frequency point adjustment devices. These frequency points can be adjusted with other speakers in the audio system (such as the main speaker). Etc.) It is more convenient to use to keep the frequency response matching, but the effect of this kind of speaker is not very ideal. Among the speakers, the active balanced subwoofer is the most complicated. Of course, the effect of replaying the subwoofer is quite good, and the volume of the speaker is relatively small. The cabinet of this kind of speaker does not have or does not fully have the ability to reproduce super bass, but through the electronic circuit (including power amplifier) specially designed for the cabinet, the lower limit frequency of this kind of speaker extends to the super bass frequency band.
This kind of speaker can extend the lower limit frequency of the speaker by 0.5~loct (octave) through the "equalization" circuit. If the lower limit frequency of the speaker is 40Hz, if the loct can be extended downward, the lower limit frequency of the speaker after the "equalization" function can reach 20Hz. The electronic circuit part of this kind of sound box has a variety of patented technologies, and the circuit forms vary widely. The electronic circuit part can be set inside the cabinet of the speaker, or it can be set separately.
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