SRX12SP bass systems are designed with simplicity and performance in mind. These bass systems feature a subwoofer and enclosure with a built in amplifier. The sealed enclosure design was build to the exact parameters for the included 12" Street Reference subwoofer which maximizes the bass output and performance of the system. Don't believe a single 12" subwoofer can give you the extra lows you're looking for you? You'll just have to experience the power of the SRX12SP bass system.