Build a passive speaker for your phone

If you’ve ever dropped your phone into a glass to amplify the sound, you know what a passive speaker is. Here’s one, made from wood, that works even better, and you can make it to fit any phone.

A full blow-by-blow is in my book, Build Stuff with Wood, coming out next year, but here’s the skinny on the how-to.

The trick is breaking it down into three layers, all made from off-the-shelf project boards from your local home center. All are 5-1/2 in. wide, but the middle layer is a thinner 3/8 in. thick while the front and back layers are 3/4.

If you have a jigsaw (or bandsaw or even a coping saw) for the curves, and almost any other kind of saw to cut the ends square, you are good to go.

You’ll notice that I left the layers long at first, so give me room for clamping as I worked on them. Then once they are all glued together, I just chopped the ends off, and then rounded all the edges to create the sleek, sexy science project you see before you.

By the way, if your phone has two speakers on the bottom, you can make a double-wide version, with two channels and two speaker holes, one on each side of the phone.

You start with the middle layer, cutting a pocket to fit around your phone (make it short enough so that the volume controls stick out the top side), and then a channel over to where the speaker will be. Sand that channel for better sound.
The front layer is thicker. All you need to do now is cut a slightly smaller pocket in it with the jigsaw, which will keep your phone in place while letting you access the screen. I used a dowel and sandpaper to make nice round corners.
Now you glue the layers together. See the little nails in the bottom layer? Those are little brads with the heads clipped off, which will help keep the layers aligned while you clamp them. Use lots of clamps to get even pressure.
You need to cut a speaker hole through the first and second layers now. This is a little jig for cutting perfect holes with your jigsaw. The jigsaw sticks to it with double-stick tape.
The blade starts in a starter hole that you drill through both layers, then the little piece of plywood pivots around the nail, letting the blade cut a perfect circle. If you see the blade wandering, the tape will flex enough to let you correct the steering.
Out comes a smooth plug, which makes an ugly coaster or even worse bathtub toy.
After gluing on the back layer and chopping the block to final length, I used the world’s simplest router table and a 3/8-in. roundover bit to round all the corners, starting in the speaker hole.
Keep the block moving steadily across the bit to avoid burn marks. Looking good! Some sanding, a couple coats of oil, and it’s ready to play your Mongolian throat singing tunes.




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