Latency is the delay between putting sound in – singing into a mic or playing a key – and the processed sound reaching your speakers or headphones. It is measured in milliseconds, and when it grows large during recording, your own voice or playing comes back late and makes it hard to keep time.
Where the delay comes from
Time is added at every stage of the signal path: A/D conversion at the mic input, the audio driver, the DAW’s input and output buffers, plugin processing, and D/A conversion. The value shown on screen does not always match the total delay that actually reaches your ears.
Round-trip latency
The total time for a sound to enter the computer and come back out after processing is called round-trip latency. When you monitor a vocal or an instrument through software, this round-trip time is what affects how the performance feels.
The relationship with buffer size
Making the buffer size smaller means less audio data is held at a time, which shortens latency. However, the CPU then has to finish its work in shorter intervals, and under heavy load you get clicks, dropouts, and system overload messages.
Delay caused by plugins
Look-ahead limiters, linear phase EQs, noise reduction, and similar processors sometimes need extra time to do their work. A DAW’s delay compensation lines the playback positions of tracks up with each other, but that does not necessarily make the monitor signal during recording immediate.
What to do while recording
Lower the buffer as far as stays stable, and either temporarily remove heavy plugins you do not need or use a low latency mode. Direct monitoring on your audio interface also helps. For how to display latency in Logic Pro, see How to customize the control bar and the display (Japanese).
