What is would be a small listening room size?

go by cubic feet (Height X Width X )Length.

12X12 with 7.5' ceiling (~ 1100 cubic feet)is towards the small end of the spectrum.

Your room is 1530 cubic feet, ~ 30 % larger, still towards the smaller end of the spectrum I would say.

I'd say 8000-9000 cubic feet is the ballpark of a typical "large" room.

12X17 is a great size for a listening room. It's at the lower end of medium in size.

Size is in the eye of the beholder,three inches to some is eight !!! Oh, never mind.

8000 = 40x20x10h, no?

That seems to me a very large room, with a footprint comparable to many houses, in many parts of the country.

I might call your room medium; I think many speakers designed for smaller spaces would start to swim, and you could accommodate some larger room designs.

John