Why add a woofer to your system? A good subwoofer widens the soundstage, as if creating more space in the recording. All tones gain more brilliance and a slightly more saturated color. This effect is especially noticeable with acoustic instruments. A saxophone becomes darker and fuller in tone, a piano becomes fuller and deeper, and cymbals gain more depth in their sonorous sound. Proper adjustment and placement of a subwoofer are crucial in this regard.
REL subwoofers come with a Neutrik connection for high-level input. The advantage of this is that you don't need a dedicated output on your amplifier. This special cable connects to the amplifier's speaker terminals. This way, the woofer always plays in stereo.