Why is the horn packed in a wooden box?

　　Let's start with the first reason. When the diaphragm of the low sound unit moves forward and backward, there are sound waves radiating forward as well as backward. The sound radiation phases of the two directions are exactly opposite, that is, 180 degrees apart. Because the wavelength of low-frequency sound wave is very long, its diffraction ability is very strong, that is to say, the directivity of low-frequency sound wave is very weak. If the horn unit is not boxed, the backward radiated sound wave will go around to the front to offset the front radiation, and the overall forward acoustic radiation energy will be greatly reduced, which is called "acoustic short circuit". It is necessary to try to eliminate the appearance of "acoustic short circuit", otherwise the low-frequency substrate cannot effectively radiate. If the horn unit is installed in a box, the radiation behind the diaphragm will be isolated by the box, which will not constitute a "sound short circuit".

　　The second reason is that every electric low-frequency unit has a low-frequency resonance point, and the output at this resonance point reaches a peak value, but the distortion is also high, and the transient response is very poor. If this resonance peak is not suppressed, the playback quality will be seriously affected. If the unit is boxed, the stiffness of the air in the box will restrain the movement of the diaphragm, so as to achieve the purpose of reducing the resonant peak and improving the function. In addition, by reasonably selecting the structure and parameters of the box, the intention of expanding low-frequency echo can be achieved. Well planned inverter boxes, passive radiator speakers, and transmission line speakers can achieve this effect.

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