ABSTRACT

Using two speakers instead of headphones does not achieve the same effect. In nature, the sound from a central source in front of the listener travels an equal path, thus reaching both ears at the same time, at the same amplitude and with the same frequency content. But a two-channel stereo setup does not have a center speaker, so in order to create a central image both speakers emit the same sound. Having no real center speaker, this central image is known as phantom center. If we could ensure that the sound from each speaker only arrived at the nearest ear, as in Figure 13.2a, the simulation would be perfect. But the sound from each speaker also arrives to the far ear and does so slightly later, while being quieter and having less high frequencies (Figure 13.2b). This late arrival confuses our brains and results in a slight smearing of the perceived sound image. This smearing effect can be demonstrated in every 5.1 studio by comparing the sound emitted solely from the center speaker (real center) and that emitted at equal levels from both the left and right speakers (phantom center). How unfocused the latter might be can be quite surprising, especially in poorly tuned surround studios.