User guide

Chapter 36 Working With Plug-in Latencies 867
Working With Plug-in Delay Compensation
The Compensation menu in the Logic Express > Preferences > Audio > General tab
allows you to either disable plug-in delay compensation (Off), or activate it for:
 Audio and software instrument tracks.
 All channels (audio, instrument, aux, output, bus, and ReWire).
About Plug-in Delay Compensation
Logic Express provides plug-in delay compensation for all channels: If activated,
Logic Express compensates for latency introduced by plug-ins, ensuring that audio
routed through such plug-ins is synchronized with all other audio.
Logic Express achieves this by calculating the amount of latency caused by plug-ins,
and then delaying audio streams by an appropriate amount—or shifting instrument
and audio tracks forward in time. The compensation method depends on the type of
channel that the latency-inducing plug-in is inserted into.
 If latency-inducing plug-ins are inserted into aux or output channels (or ReWire
channels, if used), Logic Express delays all other audio streams by an appropriate
amount.
 If latency-inducing plug-ins are inserted into audio or instrument channels,
Logic Express automatically shifts these tracks forward in time. The advantage of this
method is that other channels (that do not contain latency-inducing plug-ins) do not
need to be delayed.
As an example: Imagine a simple song with a few bass, guitar, vocal, and drum tracks.
The bass track is routed through an audio channel that contains an effect that
introduces a latency of 10 ms. All guitar tracks are routed to an aux channel that
contains several inserted effects. The combined latency introduced by these effects is
30 milliseconds (ms). The vocals are routed through another aux channel that has a set
of effects that introduce 15 ms of latency. The drum tracks are routed straight to the
main outputs, without being routed through any effects. If latencies were not
compensated for, the drum tracks would play 30 ms ahead of the guitar tracks. The
bass track would play 20 ms ahead of the guitar track, but 10 ms behind the drums. The
vocals would play 15 ms before the guitar track, but 15 ms behind the drums and 5 ms
behind the bass. Needless to say, this isn’t ideal.