What is a passive radiator?

A passive radiator is a type of loudspeaker driver that does not actively generate sound waves, but rather enhances the output of a main active driver through vibration. It consists of a diaphragm and a suspension system, similar to an active driver, but it is not powered by an amplifier or voice coil. Instead, it responds to the sound waves generated by the main driver and moves in response, causing the air inside the enclosure to vibrate and generating additional bass frequencies. Passive radiators are often used in subwoofers and other high-performance audio systems to improve low-frequency response and reduce distortion. They can also provide a more efficient and compact design compared to traditional ported enclosures, and can offer greater flexibility in tuning the system to achieve optimal sound quality.