Fig. 4-1 A three-knob 5.1-channel panner.

The precedence effect, or Law of the First Wavefront, says that we localize sound to the first arriving location, so if sound is panned halfway between left and center and we are sitting to the left of center, then the sound location will be distorted towards the left loudspeaker.

The second type of panner is the joystick. Here, a single computer game-style controller can move a sound around the space. This type emphasizes easier movement, at the expense of precision in knowing where the sound is being panned. It also emphasizes the "internal" parts of the sound field, where the source is sent to L, C, R, LS, and RS all simultaneously, for that is what such panners will typically do when set with the joystick straight up. This is often not a desirable situation since each listener around a space hears the first arriving direction—so a huge variety of directions will be heard depending exactly on where one is sitting, and a listener seated precisely at the center hears a mess, with each loudspeaker's sound affected by the associated head-related transfer functions (HRTFs). What is heard by a perfectly centered listener to perfectly matched loudspeakers driven together, is different frequency regions from different directions, corresponding to peaks in the HRTFs. It sounds as though the source "tears itself apart" spectrally.

Upon panning from front to surround, certain frequency ranges seem to move at first, then others, only to come back together as the pan approaches one single channel. Thus, although it may seem at first glance that joystick-based panning would be the most desirable from the standpoint of ease of use, in fact, most large-format consoles employ the three-knob approach, not simply because it fits within the

physical constraints of a channel slice, but because the emphasis of the three-knob panner is more correct.

The third type of multichannel panner is software for DAW. Various "plug-ins" are available for multichannel panning, and it is only a matter of time before multichannel panning is a core feature of DAW software. Advantages of software panners include automation and the potential linking of channels together to make a pair of source channels "chase" each other around a multichannel space.This is valuable because practically all sound effects recordings are 2-channel today, and it is often desirable to spatialize them further into 5.1. Methods for doing this will be described below.

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