1. Closed speaker
Closed enclosure (Closed Enclosure) is the simplest speaker system. Frederick proposed in 1923. It consists of speaker units installed in a fully sealed box. It can completely isolate the forward radiated sound waves and the backward radiated sound waves of the speaker. Due to the existence of the closed box, the rigidity of the resonance of the moving mass of the loudspeaker is increased, and the lowest resonance frequency of the loudspeaker is raised.

2. Bass reflex speakers
Also known as inverted speaker, it was invented by Thuras in 1930. In its load, there is a sound outlet opening on a panel of the box. There are various positions and shapes of openings, but most of them are also equipped with sound pipes in the holes. .

3. Acoustic resistance speakers
The acoustic resistance speaker is essentially a deformation of the inverted speaker. It fills the sound outlet conduit with sound absorbing material or structure, and acts as a semi-hermetic box to control and guide it, so as to buffer it and reduce the vibration frequency to broaden the bass. playback band.

4. Transmission line speaker
Transmission line speakers are named after the transmission line of classical electrical theory, and behind the speaker is a sound duct made of sound-absorbing siding, the length of which is one-quarter or one-eighth of the wavelength of the low-frequency sound that needs to be boosted. In theory, it attenuates sound waves coming from behind the cone, preventing it from reflecting into the open end and affecting the sound radiation of the woofer.

5. Passive radiating speakers
Passive radiant speakers are a branch of bass reflex speakers, also known as empty paper cone speakers. It was published by Olson and Preston in the United States in 1954. Its opening sound outlet was replaced by an empty paper cone (passive cone) without a magnetic circuit and voice coil.