Logic Pro automatically recognizes any installed Core Audio hardware, and uses the default settings as defined in the Audio MIDI Setup utility (Applications/Utilities/Audio MIDI Setup). However, you may want to optimize the settings for your individual hardware setup, particularly if you use several audio interfaces or a multiple input/output device.
The Devices pane contains the following preferences:
Core Audio Enabled checkbox: Enables the Core Audio driver.
Output Device pop-up menu: Use to choose between any installed Core Audio device, including the internal sound hardware. This also includes aggregate audio devices, consisting of several audio interfaces. See the Audio MIDI Setup Help for information on aggregate devices.
Input Device pop-up menu: Use to choose between any installed Core Audio device, including the internal sound hardware. This also includes aggregate audio devices, consisting of several audio interfaces. See the Audio MIDI Setup Help for information on aggregate devices.
Note: When setting an output device that also provides inputs, the Input Device pop-up menu changes accordingly. If choosing a different input device, you’ll be advised to use a common Word Clock for both audio devices, in order to ensure the best sound quality.
I/O Buffer Size pop-up menu: Determines the size of the buffer used by the audio hardware for both input and output. The smaller the buffer size, the less latency you encounter when monitoring while recording, or using software instruments.
Some points to note:
As the value is reduced, a higher strain is placed on your computer’s processor or processors.
There may be a point where the selected I/O buffer size is too small for your computer, and begins to affect playback. This usually takes the form of clicks, pops, and crackles in your audio.
You should aim for the lowest possible I/O buffer size value that doesn’t introduce clicks, pops, and crackles in your audio.
Tip: If you find that a higher I/O buffer size setting provides suitably low latency during record monitoring and software instrument playback, you should use it. This minimizes the impact on your computer’s processor or processors.
Resulting Latency (Roundtrip/Output) display: Displays the resulting roundtrip and output latency for the I/O buffer size.
Apply Changes button: Reloads the audio driver with any adjustments made to preferences in this window.
When Show Advanced Tools is selected in Advanced preferences, the following are available:
Recording Delay slider: Delays the recording of audio by a certain fixed value, helping you to compensate for any delays that are caused by the audio driver.
Note: You should not normally need to touch this setting.
Processing Threads pop-up menu: Choose the maximum number of processing threads used, or have the number of threads set automatically. Automatic is the default setting, and is recommended except when you use other CPU-intensive applications simultaneously with Logic Pro.
Process Buffer Range pop-up menu: Determines the size of the buffer used to compute mixes and effects. You can choose between Small, Medium, and Large buffer sizes.
Multithreading pop-up menu: Determines whether multithreading is set for playback tracks only, or for playback and live tracks.
Summing pop-up menu: Determines whether the Logic audio engine uses double precision or standard precision buffers when summing audio.
ReWire Behavior pop-up menu: Configures the ReWire behavior when sending MIDI data to a ReWire-compatible software instrument. You can choose between:
Playback mode: Use when playing back MIDI tracks via ReWire. This setting requires less processing power.
Live mode: Use when playing a ReWire instrument live. This setting uses more processing resources, but has lower latency.