Hornresp "acoustic path" question

I have Hornresp 51.20
For back-loaded horn situation, if I go to "combined acoustical power" window what "acoustic path lenght between outputs" means in respect to listener position?
For eg. 30cm. Is that means horn is closer to listener or other way around?

What boders me is that I have old 34.40 version too. 30cm path can be specified as positive (horn is closer to listener) or negative, but none of the results is same as version 51.20

If paths are zero, both versions give same results.
Thanks
 
I go to "combined acoustical power" window what "acoustic path lenght between outputs" means in respect to listener position?

It is independent of the listener position.

What boders me is that I have old 34.40 version too. 30cm path can be specified as positive (horn is closer to listener) or negative, but none of the results is same as version 51.20

Version 51.20 has a more accurate model, and is the one that should be used for your simulations.