Turn A PVC Tube Into A Passive Amp

Pipe up your smartphone volume

Your smartphone crushes it when ordering pizza, snapping photos, or displaying YouTube videos. But playing the audio that goes with those videos? Not so much. You could overcome the problem with a pricy speaker or some headphones—but that’s the boring route. Instead, use a PVC pipe or a sturdy cardboard tube to make a simple passive amplifier.


  • Time: 1 hour
  • Cost: $10
  • Difficulty: Easy

Tools + Materials

  • 10-inch-by-2-inch PVC pipe
  • Miter saw
  • Dremel or milling machine
  • Drill
  • 1-1⁄2-inch-long, 1⁄4-inch-diameter self-threading screw
  • Spray paint (optional)


  1. Cut the PVC pipe at 45 degrees on both ends. It should be symmetrical, with the shortest part about 8 inches long.
  2. Rotate the tube so the shortest side faces you. Along the top center of the pipe, use the Dremel to make a slot that’s slightly wider and thicker than your phone in its case.
  3. To prevent rolling, drill a pilot hole for the screw in the center of the pipe’s longest side, at a 90-degree angle to the phone’s position.
  4. Secure the screw in the hole.
  5. Optionally, decorate the amplifier with spray paint. Once it dries, put on some tunes and insert your phone speaker-first. If you have an iPhone with speakers in the bottom, prop it up with a spacer.

This article was originally published in the May/June 2016 issue of Popular Science, under the title “Pipe Up the Volume.”