BASS EXTENSION REPLACING PORT Alternative to overlong ports, passive radiators offer designers a well-proven method of extending and enhancing bass response. The Superior Dynamic Sounds (SDS) Series provides the smallest but highest-quality subwoofers in the industry today. Leveraging the best in Danish craftsmanship, but manufactured to be very affordable, these audio transducers are ideal for use in small surround sound systems, but can also be used in a wide variety of end user products and applications for multimedia audio reproduction. Steel frame. Pairs with 830656