When recording audio or playing a software instrument in Logic Pro X, you might experience a slight delay between playing or singing a note and when you hear the sound from your speakers or headphones. This delay is called input monitoring latency. A variety of factors contribute to input monitoring latency, including:
- The input and output (I/O) buffer size setting in Logic Pro
- The analog-to-digital (A/D) and digital-to-analog (D/A) conversion processes
- Any audio interface software that you're using
- The sample rate of your project
- Plug-ins inserted on tracks in your project
Though you can’t change the amount of input monitoring latency produced by the A/D and D/A conversion processes or by your audio interface’s software, you can set the sample rate of your project and adjust the I/O buffer size to minimize latency. You can also manage latency caused by plug-ins using Low Latency Mode while recording.
Set the sample rate of your project
Set the sample rate for your project when you first create it. Higher sample rates result in less input monitoring latency. However, projects with higher sample rates create larger audio files, which can increase the load on the processor and the disk in your Mac. Plug-ins also require more processing power at higher sample rates.
You can't change the sample rate of a project after you've created it.
Adjust the I/O buffer size
The I/O buffers temporarily store some of the incoming and outgoing audio data to protect against audible dropouts, clicks, or pops. You can change the I/O buffer size at any time to minimize latency.
In Logic Pro, smaller I/O buffer sizes reduce input monitoring latency. However, smaller buffer sizes require more processing power, which can cause system overload alerts. Larger I/O buffer sizes require less processing power, but increase latency.
When recording, set the I/O buffer to the lowest setting. If you encounter system overload alerts, increase the I/O buffer size to the next setting. Projects with many tracks or a lot of software instruments require higher I/O buffer sizes, depending on the amount or RAM and the speed of the processor in your Mac.
To change the I/O buffer size:
- Choose Logic Pro X > Preferences > Audio.
- Click Devices.
- Choose the buffer size from the I/O Buffer Size pop-up menu. If you're using a USB interface, set the I/O buffer size to no less than 128 samples. For Thunderbolt interfaces, you can set the I/O buffer size to the lowest setting.
Logic Pro shows the resulting latency under the I/O Buffer Size menu. Roundtrip latency is the total amount of input monitoring latency you'll experience from audio input to audio output.
Turn Low Latency Mode on to manage plug-in latency
Certain plug-ins can contribute to input monitoring latency, particularly dynamics plug-ins with look-ahead functions. If you're using these kinds of plug-ins in a project, you can minimize the latency they produce while recording using Low Latency Mode.
Low Latency Mode bypasses plug-ins as needed, so the amount of latency doesn't exceed the Limit setting in the Plug-in Latency section of the General Audio preferences of Logic Pro. Low latency mode is especially useful when you want to record a software instrument in a project that includes latency-inducing plug-ins.
To turn Low Latency Mode on, choose Record > Low Latency Mode.