the big space you can see on the RH side extends into a kitchen - so the room is about 30 ft wide at the speakers; but is about 12 ft wide at the listening position (not counting the cavity in the chimney created by the firebox - the smney stack itself must act like a port (!))
Wendell at Magnepan says the 3.7 is acoustically SMALLER than the 1.7, even tho it is physically larger (different design internally)