Mira la página 6 del manual, a ver si es lo que buscas...
http://www.knufinke.de/sir/downloads/SIR2_Manual.pdf
"The default impulse-file directory is the directory, which content you see, when you open a new
instance of SIR.
If you want to change the directory use the “...” button.
If you want to change the directory after installation, use the option in the preferences-menu of
SIR2 (see 8.3 Default Impulse File Directory)"