DAFX: Digital Audio Effects, Second Edition

5.5 Spatial Audio Effects for Multichannel Loudspeaker Layouts

5.5.1 Loudspeaker Layouts

In the history of multichannel audio [Ste96, Dav03, Tor98] multiple different loudspeaker layouts with more than two loudspeakers have been specified. The most frequently used layouts are presented in this chapter. In the 1970s, the quadraphonic setup was proposed, in which four loudspeakers are placed evenly around the listener at azimuth angles ±45° and ±135°. This layout was never successful because of problems related to reproduction techniques of that time, and because the layout itself had too few loudspeakers to provide good spatial quality in all directions around the listener [Rum01].

For cinema sound, a system was evolved in which the frontal image stability of the standard stereophonic setup was enhanced by one extra center channel, and two surround channels were used to create atmospheric effects and room perception. This kind of setup was first used in Dolby's surround sound system for cinemas from 1976 [Dav03]. Later, the layout was investigated [The91], and ITU gave a recommendation about the layout in 1992 [BS.94]. In the late 1990s, this layout also became common in domestic use. It is widely referred to as the 5.1 system, where 5 stands for the number of loudspeakers, and .1 stands for the low-frequency channel. In the recommendation, three frontal loudspeakers are at directions 0° and ±30°, and two surround channels at , as shown in Figure 5.5. The system has been criticized ...