The APS 8 D is designed to deliver maximum performance in a sealed enclosure with ultra-compact volumes from 7.5 lt. to 8.5 lt. It features push connectors for ease of wiring and configurations and has been developed with a primary goal: to deliver high output in tight spaces. Output is a matter of excursion; the more air the cone moves, the more output. However reduced mounting depth traditionally has meant low excursion. Prima subwoofers employ a special cone-dustcap-basket geometry which guarantees large excursion of the mobile group, while keeping the mounting depth to a minimum. The surround and spider have been carefully designed to prevent the rocking-mode phenomenon. The cooling circuit has been designed with air vents on the basket underneath the spider, eliminating the need for vents on the bottom-plate. This allows the subwoofer to be mounted close to the back wall of the enclosure, making the most of the reduced mounting depth.