Speaker driver that is not powered and is used in conjunction with a woofer generating movement by being vibrated by the back-pressure of the powered woofer. Passive radiators are used instead of ports to achieve a similar effect. Instead of being ported, the woofer enclosure is sealed and airtight. The powered woofer moves and creates pressure inside the cabinet, increasing pressure as it moves in and decreasing pressure as it moves out. The passive radiator is moved by these pressure changes being pushed out as the woofer moves in compressing the air inside the cabinet and being pulled in as the woofer cone moves out. he passive radiator allows the back force of the powered woofer to increase sound levels without using a port or opening the cabinet in some other way. This results in tighter, lower bass more similar to a sealed enclosure with increased efficiency more like a ported enclosure (of course not fully achieving the maximums set by either format as this design is a calculated compromise).