LNGR / Knowledge
Passive radiators in practice
A passive radiator can achieve low tuning without a long port, but it requires enough moving mass and substantially more excursion capability than the active driver around tuning.
What moves the radiator?
The active driver compresses and rarefies the air in the enclosure. That pressure drives the passive radiator. Its moving mass and suspension form the tuning element.
Mass sets tuning
Adding mass lowers the tuning frequency. The correct amount depends on enclosure volume, radiator parameters and the active driver alignment. Simulation is the starting point, not a final guarantee.
Excursion margin
Near tuning the radiator can move much farther than the active driver. A radiator with insufficient displacement capacity will become the system limit even when the powered driver remains within Xmax.