What amplification circuit does the built-in amplifier of the subwoofer use?

The vast majority of active subwoofers, the built-in amplifiers use Class D amplification lines, and now the more fashionable name is also called the digital amplifier. Why use Class D amplification lines? Because this kind of amplification line is very efficient, does not generate heat, the output power can easily reach hundreds of watts or even kilowatts, and the cost is low. Moreover, the bandwidth of the subwoofer is about 20 Hz-150 Hz, and the distortion of the class D amplifier is high, which is disadvantageous for the disadvantages of the middle band and the high band. Of course, there are also a few higher-grade subwoofers that insist on using Class AB amplifiers. If you really work with Class AB amplification, the area of the heat sink on the back of the subwoofer is bound to be quite large, because the output area of a few hundred watts of output power is as large as a hundreds of watts.