Use a hoover to hoover a small thread through the hole, attach to speaker cable and pull through, same as you might thread a di2 wire through a bike frame.
I fished cables through a 125yo stud wall today using a gear outer, then winding the earth of a 3 core cable round an inner cable. Taped it all together and got it all through in one go.
Use a hoover to hoover a small thread through the hole, attach to speaker cable and pull through, same as you might thread a di2 wire through a bike frame.