Configuring the Playback System

Of the various surround sound formats introduced over the years , the one that's emerged as most common is called 5.1 . With this format, you typically play your audio through five full-frequency speakers, which are fed by five independent channels (left, right, center, left surround, and right surround), plus one dedicated low-frequency subwoofer , which is fed by a channel referred to as an LFE (low-frequency effect). Many manufacturers package systems that include the speakers and amplifiers to play back 5.1 audio. If you're looking to purchase a system, make sure it has six analog inputs, so that it can receive signals from the outputs of your audio interface.

You can place your speakers in a lot of different ways. The following diagram shows an overview of a common layout designed specifically for monitoring 5.1 music playback. The basic idea is that the speakers are placed at an equal distance from where you (the black dot in the center) typically listen. The numbers indicate degrees of separation. Looking directly ahead, the center speaker is considered to be 0° off center. The right front speaker is 30° to the right of the center speaker, and the right rear speaker is 110° to the right of the center. The left front and left rear speakers are mirrored on the left side. The LFE is not indicated in the diagram because subwoofers tend to sound dramatically different depending on where you put them in the room. Exact placement of the subwoofer will be unique for every room, but typically it is placed on the floor in alignment with one of the front three speakers.

Configuring Logic

You'll need to do a little preliminary work in Logic to get it prepared for surround mixing.

Assigning the Outputs

In order for this to work, you will need not only the speakers but also an audio interface with at least six independently addressable audio outputs. Emagic's EMI 26 sound card is a good example of one that will work well. Logic will then need to know which outputs are connected to which speakers . Otherwise, when you tell Logic you want a track to be played out of the center speaker, it may come out of the left rear one.

1.	Navigate to APTS_Logic_7 > Song Files > Lesson 14 Project Files, and open the file 14Begin.lso .
2.	From the main menu bar, select Logic Pro > Preferences > Audio. The Audio Preferences pane opens.
3.	On the Audio Preferences pane, choose the Surround tab. The Surround tab lets you configure various options related to your speaker output. Most important, it shows you which audio interface outputs are designated for which speaker positions . You can assign a hardware output to each surround sound channel by choosing an output from the pop-up menu under each channel, or choose a surround format from the Show As menu. Let's choose 5.1.
4.	From the Show As menu, choose 5.1. The Output Assignment area updates to show the selected surround format. Pay particular attention to which audio output has been assigned to which channelthis will become important as the lesson progresses.
5.	Close the Preferences window.

Adding Output Objects

In the exercise above, you set Logic to send signals to six discrete outputs. Logic consequently needs six Output Objects in the Environment to transport the signal to your audio interface. Let's create a Surround Output layer in the Environment and populate it with the appropriate Audio Output Objects.

1.	Press Cmd-8 to open the Environment.
2.	Switch to the Environment's Audio layer.
3.	Create six Audio Objects. (For more information on creating Audio Objects, see Lesson 12, "Setting Up the Audio Environment.") Logic doesn't have a single surround sound Object, so creating six Output Objects works just the same.
4.	Now assign the new Objects to Output channels, and name them to match their speaker positions, as follows : Assign the first new Output Object to output 1 (in the Object Parameter box), and change the name to Left. Assign the second new Output Object to output 2 (in the Object Parameter box), and change the name to Right. Assign the third new Output Object to output 3 (in the Object Parameter box), and change the name to Rear Left. Assign the fourth new Output Object to output 4 (in the Object Parameter box), and change the name to Rear Right. Assign the fifth new Output Object to output 5 (in the Object Parameter box), and change the name to Center. Assign the sixth new Output Object to output 6 (in the Object Parameter box), and change the name to LFE .
5.	Select all the new Output Objects, and then deselect the Show EQ, Show Inserts, Show Sends, and Show I/O check boxes.
6.	Rearrange the Output Objects so that the meter positions better reflect the actual speaker positions. Compare them with the figure below. This layout makes it easier to understand at a glance what each meter represents.
7.	Close the Environment window.