In loudspeaker-based reproduction, the spatial quality deteriorates when the listeners move outside the sweet spot. While this seems well known in the spatial audio community, perceptual data that allows quantifying this effect is not common, which prevents suggesting solutions for off-centre listening. In this study, we collected perceptual data to answer three main hypotheses: (H1) that localisation for stereo reproduction over loudspeakers and over headphones with binaural recordings of a dummy head would result in similar perceptual outcomes, (H2) that translation of the listener is equivalent to adding the corresponding interchannel time and level differences in the sweet spot, and (H3) that the spread of localisation responses is correlated to the localisation uncertainty perceived by the listener. Regarding H1, the responses for binaural recordings and loudspeakers were equivalent within a 2° margin. Regarding H2, localisation off-centre produced only a shift in the responses compared to interchannel time and level differences in the sweet spot. Regarding H3, the spread in localisation responses strongly correlated with the perceived uncertainty ratings. Altogether, the results suggest that a localisation test using binaural recordings in the sweet spot — including interaural time and level differences — may be sufficient to characterise off-centre localisation and localisation uncertainty for stereo reproduction.
