Subwoofer for Keyboard instruments New Twisted Flare Port contributes to clear and tight bass Advanced YST II (Yamaha Active Servo Technology II) 20 cm (8”) cone woofer Stylish addition to any room Excellent Bass for Music Performance This compact subwoofer incorporates a number of Yamaha’s advanced, high performance bass technologies, including Twisted Flare Port and Advanced YST II (Yamaha Active Servo Technology II). This results in sensational bass response that adds significantly to the enjoyment of music performance. Enrich bass to your keyboard’s speaker KS-SW100 is compatible with Yamaha keyboard instrument shown below.