A passive subwoofer is a type of subwoofer that does not have its own integrated amplifier and therefore needs to be connected to an external amplifier. Passive subwoofers are often chosen for larger sound systems or for environments where an amplifier or AV receiver is already present. Because of the need for an external amplifier, passive subwoofers can require more work to install and set up, but they can also provide more flexibility in sound editing.