The PSRX718S subwoofer’s compact design is equally at home as a small, high-performance satellite subwoofer system or as a building block for larger subwoofer arrays. 18 inch, 2268H Differential Drive® woofer for extended low frequency output. Large port area for reduced distortion. 20mm threaded pole socket for solid, secure satellite speaker mounting. 18 inch plywood subwoofer High power, reliable and performance Suitable for tour sound