3-D audio systems are effective when the listener's head location is close to the head location assumed when the system was designed. In order to accommodate head movement, it is possible to design 3-D sound systems that continuously select appropriate virtual audio filters that correspond to a listener’s varying head position. The required spatial resolution of the audio filters depends on the size of the sweet spot. In this paper the size of the sweet spot of a two loudspeaker 3-D audio system is evaluated subjectively at symmetric and asymmetric head locations.