How do you properly set up a horn speaker

Hi- I have a set of Classic audio T1.4 horns that I am setting up - Do horns get set up the same way as regular speakers- I was going to use the cardas method but want to be sure that is fine- Also my room is 15x28 but at the point where the speakers are is a bay window(treated) that jets out to 17 feet so when using the calculator from cardas do I use the 17 feet where the speakers sit or the 15 feet which is the rest of the room- Thanks for the input-