Introduce several types of speaker cabinet structure, mainly including closed box, reflector box, transmission line, passive radiator, coupling cavity and horn, etc., as follows:
1. Closed Enclosure is the simplest speaker system. It consists of a speaker unit installed in a fully sealed cabinet, which can completely isolate the forward and backward radiated sound waves of the speaker. However, due to the presence of the closed box, the rigidity of the resonance of the motion mass of the speaker is increased, and the minimum resonance frequency of the speaker is increased. It sounds a bit deep, but the bass analysis is good. When using ordinary hard folding ring speakers, in order to obtain satisfactory bass reproduction, a large cabinet with a large volume is required. The new airtight speaker uses the elastic effect of the compressed air quality enclosed in the box. Although the speaker is installed in a smaller box, the air cushion behind the cone will exert a counter-driving force on the cone, so this small airtight speaker is also It is called air cushion speaker.
2. Bass-Reflex Enclosure (Bass-Reflex Enclosure) is also called Acoustical Phase Inverter. In its load, there is a sound outlet opening on a panel of the cabinet. How many positions and shapes are the openings? Species, but most of them are equipped with acoustic tubes in the holes. According to the Helmholtz resonance principle, the relationship between the internal volume of the box and the sound duct hole produces resonance at a certain frequency, which is called the anti-resonance frequency. The sound waves radiated from the rear of the loudspeaker are inverted through the pipe, and then radiated from the sound outlet to the front, and superimposed in phase with the sound waves radiated from the front of the loudspeaker. It can provide a wider bandwidth, higher sensitivity, and smaller Under ideal conditions, the lower limit of the low-frequency playback frequency can be as much as 20% lower than the speaker resonance frequency. This type of speaker can reproduce rich bass with a smaller cabinet, and is currently the most widely used type.
3. Acoustic resistance enclosure (Acoustic resistance Enclosure) is essentially a deformation of an inverted enclosure. It is filled with sound-absorbing material or structure in the sound outlet duct, which acts as a semi-closed box to control the phase inversion and buffer it. , To reduce the anti-resonance frequency to broaden the bass replay frequency band.
Fourth, the transmission line speaker (Labyrinth Enclosure) is named after the transmission line of classical electrical theory. There is a sound tube made of sound-absorbing wall panels on the back of the speaker, and its length is a quarter of the wavelength or one eighth. In theory, it attenuates the sound wave coming from behind the cone, preventing it from being reflected to the open end and affecting the sound radiation of the woofer. But in fact, the transmission line speaker has a mild damping and tuning effect, which increases the sound output of the speaker near or below the resonance frequency, and reduces the amount of stroke while enhancing the bass output. Usually the sound ducts of this kind of sound box are mostly folded in a labyrinth shape, so they are also called labyrinth or tortuous.
5. Passive radiating speaker (Drone Cone Enclosure) is a branch of bass reflex speaker, also known as empty cone speaker. Its opening sound outlet is replaced by an empty paper cone (passive cone) without a magnetic circuit and voice coil. The radiated sound generated by the passive cone vibration and the forward radiated sound of the speaker are in the same phase working state, using the air in the box The composite sound compliance and passive cone quality formed with the passive cone support element form resonance to enhance the bass. The main advantage of this kind of speaker is that it avoids the unstable sound produced by the reflected sound hole, and it can obtain good sound radiation effect even if the volume is not large. Therefore, the sensitivity is high, which can effectively reduce the working range of the speaker, and the standing wave influence is small. Clear and transparent.
6. The coupled cavity speaker is a box structure between the closed type and the bass reflex type. Its output is output by the sound hole driven by one side of the cone, and the other side of the cone is coupled with a closed box. The advantage of this kind of speaker is that the amount of air pushed by the speaker at low frequencies is greatly increased. Because the coupling cavity is a tuning system, when the cone movement is restricted, the output of the sound outlet does not exceed the sound output of a single cone, which broadens the low frequency weight. Amplify the range, so the distortion is reduced and the withstand power increases. In 1969, the A·S·W (Acoustic Super Woofer) speaker published by Yukihiko Kawashima of Lo-D in Japan is a coupled cavity speaker, suitable for reproducing bass without distortion with small-diameter long-stroke speakers.
7. Horn type enclosure (Horn type Enclosure) for household type, mostly adopt the form of folded horn (Folded Horn), its horn mouth is coupled with a larger air load at the mouth, and the driving end diameter is small. The back of the speaker is fully sealed, and the pressure in the chamber is as much as the back of the speaker cone. In order to keep the pressure balance between the front and rear of the cone, an inverted horn is installed in front of the speaker. The folding horn speaker is a derivative of the phase-inverted speaker, and its sound effect is better than the closed speaker and the general bass reflex speaker.