Step 3: Drill Hole In Plumbing Cap and Insert Vinyl Hose
Take your plumbing cap.. and a drill (or I just used scissors as an awl).
Make a hole in the middle of the top of the plumbing cap.
You want to make the hole a bit smaller that your vinyl hose, this is so you won't have to glue the tube into the hole.
The tube is pliable enough that once the hole is just a little smaller than the hose you should be able to force the tube in (lots of twisting and arm power).
Make sure the tube only goes into the cap about 1/2 and inch to 3/4s of an inch.
(you don't want the tube to puncture the speaker when the parts are put together).