What is the recommended way to add or change a manufacturer's loudspeakers and get into the base. I have the data files on disk but I am unsure how to load them into the manufacturer's data base without interfering the existing data?

If you don't want to touch existing data, go to the Speaker Base main directory (GlobalSpeakers30) and create a subdirectory like Speakers_New. Copy the new data to this location. To use these Speaker Models in a project go to Select Speaker Models, choose the path from above and "Add" the Speaker Models you want to use. If you now hit F2 after having picked a Loudspeaker the list shown will contain all of the added Speaker Models.