Apple Logic Pro 9 - Manual (Page 1185)

The center speaker is usually used for “dialogue,” and “incidental music/effects,” tracks
in films. Its level should be fairly close to that of the left and right speakers, but can be
increased a little to enhance the intelligibility of dialogue.
In general, you should aim to have the sound from all front speakers arriving “evenly” at
the listening position at the same time.
The level of surround speakers and the subwoofer (LFE) is also critical. You want to set
these levels to be “immersive,” and part of the surround stage, rather than “additions” to
the front speakers. In general, surround speakers are used for “surround effects,” “main
score” and “incidental music/effects” tracks.
Also critical for the surround and subwoofer channels is the delay time. Unfortunately,
there’s no formula that will work for every listening situation, due to a range of factors,
such as surround speaker distance from the listening position, among others.
Assuming that the levels of all speakers are suitable, the timing of the surround (and LFE)
speakers may seem slightly “out” in comparison to the front speakers. Most surround
amplifiers allow you to negatively or positively adjust the “delay” of these speakers.
When mixing in Logic Pro, you should aim to strike the right balance between all of the
factors discussed.
The surround encoding process—performed in Compressor—writes “surround encode
flags” for the surround speakers, depending on the chosen format. These “flags” are
understood by surround decoders (AV receivers, decoding software or surround amplifiers).
There’s no need to worry about setting slight delays between tracks when working in
Logic Pro. The surround encode flags are designed to handle this.
Encoding Surround Bounce Files
Logic Pro surround bounces are not encoded. Surround bounce files can, however, be
encoded in Compressor, which is included in the Logic Pro package. See the Compressor
documentation for instructions on surround encoding.
Dolby Digital
Dolby Digital (also known as AC3) includes the LFE channel. It is a compressed format,
commonly used for DVDs and digital terrestrial or satellite TV broadcasts. It is also widely
used for computer game soundtracks.
DVD-A
DVD Audio format, used for music delivery. Supports 24-bit, 96 kHz playback of up to 6
channels (5.1). 24-bit, 192 kHz mono or stereo is also supported by the format.
1185 Chapter 39 Working with Surround