The spaciousness of soundstage is not only determined by the features of a system (or orchesta, for example). Spaciousness is also related to the subjective perception of space created by the room acoustics. Therefore, also speakers positioning and paradoxically the room parameters themselves cause the illusion of being in a larger room.
For a long time, it was common belief that spaciousness was a direct function of an even distribution of the sound field within a listening room. Only since the late 1960s real progress has been made in finding the cause of spaciousness: diffuse field is not the primary cause.
The element that most emphasizes the spaciousness is the lateral arrival of the first reflections. Therefore, a wider spatial impression can be created wirh few delayed early reflections reaching the listener’s head from lateral directions.
The diagram above shows the path difference between direct sound (blue) and early reflections (violet); “a” is the arrival angle.
Early reflections are independent of room’s reverberation. Only reflections with a delay time with respect to direct sound in the range from 5 to 80 milliseconds ( from 6 feet in to 90 feet in additional path) contribute to spaciousness. Frequencies from 500 to 3000 Hz contribute most to the perception of spaciousness, and their arrival angle is proportional to their effectiveness. For example, a zero arrival angle (i.e. early reflections from the room’s bottom) will result in no spatial enhancement due to the lack of sound pressure difference between the listener’s ears.
Therefore, is it possible to improve spaciousness with better speakers’ or listener’s positioning. It is also possible, when desired, to modify room’s acoustics in order to adjust early reflection to the listener’s seat.
First reflections’ arrival angle is the factor which most contributes to spaciousness, but not the only one. For example, spaciousness increases proportionally to the listening volume.
- Barron M, Marshall AH, “Spatial Impression Due to Early Lateral Reflections in Concert Halls. 1981.
- Burgtorf W, “The Percectibility of Delayed Sound Signals. 1964.
- Neu G, Mommerz E, Schmitz A, “Investigation on the True Directional Sound Reproduction by Playing Head-related Recordings Over Two Loudspeakers”. 1992.