Is a restaurant, a shul social hall or your neighbor's house a בית חתנים?
But then it's a seuda
exclusively prepared for the
honor of the choson and kallah, and everybody that comes to participate are only coming in for the choson and kallah's honor. So when it's done in a restaurant, the entire place is rented out, or a simcha room is rented out so it's מקום מיחד - and not stam a place where other people are found and are also served to eat.
And then by the sephardim, they poskin sheva berachos is ONLY made in the home of the choson and kallah, otherwise if sheva berachos is outside their home, then they only make two berachos -- בורא פרי הגפן and אשר ברא ששון ושמחה.