As of 2014, the current version of Logic is Logic Pro 9. To use surround sound in Logic Pro 9, go to the "Preferences," menu, then to "Audio," then click "I/O Assignments."
Once in the I/O Assignments tab, select "Output." Under "Surround," "Show As," click the combination of surround sound speakers that you currently have. Select the output for each speaker position, depending on the number of speakers in the surround sound system. To support surround sound, the sound system must have at least five speakers, including a center channel, two front speakers, and two rear speakers. Most five-speaker surround systems also have a subwoofer, making the system a 5.1 surround sound system. There are also a number of other combinations of surround sound speakers. These include 5.2, 7.1, 7.2, 9.1, and 9.2. If the surround system's name has a .2 at the end of it, this indicates that the system has two subwoofers. For a seven-speaker setup, the surround sound is one center channel, two front speakers, two rear speakers, and either two high-front or two mid-back speakers, creating a complete surround environment. For a nine-speaker setup, the surround speakers are generally two front, one center, two high-front, two back, and two mid-back speakers.