Car subwoofers with passive radiator

Passive radiator

— a passive radiator, or radiator, is the outer part of the speaker (diffuser) installed in a corresponding hole in the subwoofer cabinet. Roughly speaking, this is the same speaker, but without the coil and magnet. It is usually installed in "closed box" type cases, and its role is similar to that of a phase inverter: improving sound quality, in particular, "deepening" the sound of small models. At the same time, the passive radiator is not subject to noise due to air flow (which is typical for a phase inverter tube) and does not actually affect the thickness of the subwoofer cabinet.