A speaker device includes a main cabinet composed of a cabinet body and a speaker mounted on the cabinet body; an extendable cabinet composed of a bellows tube and a passive diaphragm, the bellows tube having a front end communicably connected to the cabinet body and a rear end closed by the passive diaphragm, and the passive diaphragm being axially aligned with the speaker; and a damping assembly being arranged in the cabinet body and in the bellows tube, and having a front end connected to the cabinet body and a rear end to the passive diaphragm. With these arrangements, the speaker device can have improved bass performance in the entire low-frequency band instead of being limited to only a few low-frequency points.