Step 1- You will need a template of your speaker. Cut out three pieces of MDF to the shape of your speaker. The speaker side (face) will need to be cut out for your speaker to fit. Clamp all three pieces and sand the edges so they are smooth and even. As you can see we used a vise to keep our pieces together. Keep them clamped for now.
Step 2- Measure to see how long you want the speaker tube to be. Then cut two pieces of MDF 1" (25mm) x (length of speaker). With the sections still clamped cut 1" notches off the top and bottom of the main three pieces so the two length piece can be fitted. Now unclamp them and glue them together as shown. "Make sure the depth of your notches match up with the thickness of your MDF. In this case we used 1/4" thick material."
Step 3- On the aluminum sheet, drill four evenly spaced holes making sure there is a hole at each end of the tube. Rivet the sheet to the 1" piece of MDF, wrap the sheet all the way around and repeat for the other side. Try to minimize the gap where the two ends meet. If you have aluminum sheet overhanging from the tube, you could trim them off with scissors.
Step 4-To give it strength and for waterproofing purposes, fiberglass the inside and outside of the tube. Then sand the outside to get rid of the sharp edges and to make it smooth.
Step 5- If the finishing of the tube is to your liking, you may want to cover it with gel coat. In this case I went for marine grade vinyl. I had to send this one away to get it covered by professionals. They also lined it with sponge to give it more cushion and to hide away any errors.
Step 6- Measure the size of the pipe diameter where you want this Speaker to be mounted and purchase the right sized U-Bolts Stainless or Aluminum. If you're going to cover the U-Bolts you may want to go slightly bigger. I covered my U-Bolts with black automotive vacuum hose to stop it from scratching and rattling. Drill 4 holes how you want your tube to be fitted and bolt them up.