The Harman Kardon subwoofers add a deep bass to your movies. You can easily connect the subwoofers to your other Harman Kardon Citation speakers. That way, you can easily create a home cinema. The subwoofers are made of Kvadrat fabrics. The fabrics of this brand repel dirt and let the sound through without quality loss. You use the Citation Sub S in your smaller living room or a large bedroom. If you want to fill a large living room with a deep bass, go for the Citation Sub. It's larger and provides a more powerful bass.