How to Make Your Own Bass Tubes
By Jan Benschop
A bass tube is just another type of cabinet for a woofer, only easier to build. A product called Sonotube, which contractors use to pour cylindrical concrete columns, is the ideal building material for a bass tube. To finish the end of a tube, circles cut from 3/4-inch plywood work great, are easy to machine and provide strength. If deep bass in a minimum space is your goal, this single-woofer tube design yields very low, articulate bass.
Cut a piece of Sonotube 18 inches long. Set a table saw rip guide to 18 inches and slowly rotate the tube as you cut. If you are doing this with a saber saw, make a small hole in a yardstick at 18 inches, stand the tube and the stick on end together and slide the yardstick around the tube with a pencil point through the hole to mark a circle on the tube. Sand the edges smooth.
Cut two plywood circle plugs to fit inside the tube ends. Cut slightly too large and rasp or sand them just small enough to tap into the tube gently with a hammer. In one circle, cut out a hole to fit the inside-flange diameter of the woofer. In the other circle, cut a hole 1/2-inch smaller than the outside diameter.
Work the woofer circle into the tube end. Drill eight evenly-spaced holes through the tube edge into the edge of the plywood. Drive in pan-head screws. Paint the tube and the other wood ring now, if desired.
Cut a foot of speaker wire. Split and strip 1/2-inch of insulation off the ends. Solder the copper side to the woofer's positive and the tinned side to the negative terminal. Drill two small holes in the tube side near the woofer for binding posts. Solder the copper wire to the red post and the tinned wire to the black post. Attach the posts through the holes you made for them. Screw the woofer into the end circle.
Connect the speaker to the amp with the sine generator driving it. Experiment with different densities of pillow stuffing in the tube while running sine-wave sweeps at the lowest frequencies. Go for the loudest sound at the lowest frequency.
Wrap a circle of cloth around the edges of the other wood circle and staple it around the back edge. Insert the ring into the empty end of the tube.
Jan Benschop started writing professionally in 1979. His corporate technical writing clients included Nortel, Alcatel and Glaxo. Also the author of several short stories, Benschop holds a Bachelor of Science in English from Campbell University. He built loudspeakers for more than a decade and has several international patents pending in the field.