The Swedes' numbers against the Belgians Florent Lambiet and Martin Allegro were written as 11-7,12-10,11-3.
It wasn't the most exciting match, a tentative first set and a tight second before the Swedes ran away in the third.
Falck's short game paved the way for Karlsson, who was often able to step inside and cut in his fast, heavy forehand.
Both Falck and Karlsson will enter the singles match later today.
Semi-final and final games in the doubles tournament await tomorrow.
The pair Karlsson/Falck have played together for ten years and have a WC title, two EC silver and two EC bronze in doubles together.