The low-frequency lower limit of a speaker is closely related to two elements: the resonant frequency of the speaker unit and the volume of the enclosure. In the absence of packaging, the low-frequency resonance frequency of the bass unit is usually considered as the lower limit of the effective frequency response of the unit. The larger the aperture of the unit, the lower the resonance frequency is generally. Therefore, using a large speaker is beneficial for restoring lower frequencies.
In addition, a larger diaphragm area can propel more air under the same amplitude, making it easier to achieve more low-frequency sensing. After the horn unit is packed, its resonant frequency will increase due to the effect of air stiffness inside the box. The larger the volume of the box, the smaller the effect of air on the unit, and the smaller the increase in resonant frequency, which is conducive to achieving a lower comprehensive low-frequency response. On the one hand, large speakers are convenient for using large caliber bass units, and on the other hand, they have a larger box volume, so low frequencies are usually better.