The ABLM plugin, https://www.tbproaudio.de/products/ablm, calculates the latency between a chain of plugin as banded by a send and receieve instance of that plugin. The ABLM plugin can be operated in “gain stage” mode so that it only calculates latency and does not match the output volume among various plugin chains in the mix.
A mix using the same 3rd party AU plugins and presets is shown below in Logc and Reaper. The latency times Logic and Reaper report are compared to the latency times the ABLM plugin reports. The latency times reported by Reaper and ABLM are essentially the same. However, the latency times reported by Logic and ABLM differ for each plugin chain. There also seems to be a pattern of a 20ms offset between the 3 plugin chains measured by ABLM in Logic. Yet the latency times reported by Reaper and Logic are also essenitally the same.
One possibly is the ABLM plugin is working correctly in Reaper but working incorrectly in Logic, i.e, Logic and Reaper are both reporting the same plugin chain latencies so therefore ABLM must be wrong in Logic. Another possibility is that ABLM is working correctly in both Reaper and Logic and there fore Logic’s PDC is working incorrectly. The fact that the mix results from Reaper and Logic do not sound the same may indicate PDC in Logic is not working correctly.
The 10.6.3 release of Logic reportedly fixed issues with plugin delay compensation (PDC) fpr plugins using a sidechain input.
REAPER native PDC and ABLM PDC
Logic native PDC and ABLM PDC
