Sorter speed is located in a tab labelled "System Speed Selection"*, typically in the Command Center section.  For the desired sorter, make sure that the appropriate Control Panels are stopped, then select the new speed for that sorter selected by drop down. After changing sorter speed control panel should started, followed by starting the sorter & merge. For speed measurement actual speed & ICW speed site can check by using Tachometer to test speed correctly. 

*Key points make sure control panel should be stop during speed selection & change.