Not just an active 21-inch subwoofer, the Thunder-KMT21 I is also a proper instrument for the management and processing of the audio signal. At the heart of the Thunder-KMT21 I are 2 channels of 2400 W @ 4Ω in Class D – one dedicated to the 21" woofer and the other connected to a speakOn output on the rear panel – allowing different configurations in combination with any of our passive loudspeakers such at single mid-high speaker, entire columns of line arrays or other passive subs as reinforcement of the mid-low frequencies in larger applications. With a 21" woofer, the Thunder-KMT21 I is ideal for medium to large applications where high quality, powerful sound is required.