DIY Acoustic Smartphone Amplifier (Wooden Passive Speaker)

Hello everybody, hope you're doing well

in this instructable, I'm going to show you how to make an acoustic phone amplifier, which is also called a passive phone speaker. The cool thing about an acoustic phone amplifier is that it doesn't require any additional components like an additional external speaker or batteries, wires, switches, and so on, but that doesn't mean that you should underestimate this kind of device in fact don't underestimate this concept thinking that the sound won't be louder, after all this is an old principle that is more common than you may think for example old phonographs (in later forms called gramophones) used this principle to amplify sound (through the horn), or for example, an acoustic guitar uses string vibrations that resonates through the body, unlike an electric guitar that uses electromagnetic pickups to pick up sound.

So to sum it up this is an amplifier that doesn't use any electrical components and that could be occasionally moved from desk to desk, make one that looks good and you got yourself a functional piece of home decor :).

Note that this design of an acoustic amplifier will work on those phones that have a speaker located on the bottom of a phone (right next to the charging port), those phones that have a speaker located for example right next to the camera require a slightly different design.

This project doesn't require a lot of components essentially to make this you only need a wooden board (I recycled an old cutting board, this worked great because I didn't have to make a hole for the phone to fit through).

Square dowel rod (2cm by 2cm)

Sponge foam (optional)

Popsicle sticks (2 sticks)

Rubber feet (optional)

Wood glue (or epoxy)

Linseed oil

Spray paint (optional)

Tools: Manual miter saw and box (I used a manual miter and saw box to make miter corners, but a regular handsaw would also work), jigsaw, drill sandpaper, clamps, ruler, hot glue gun.

As you can see this project does not require a lot of components.

I used a ruler and a marker to draw a line on the board that splits the board in half and I later cut the board using a jigsaw, because I used an old cutting board that already had a hole for the smartphone I didn't have to prepare that hole in the board, but if you use an ordinary wooden board you would need to cut that hole out, and probably the easiest way of doing it (using simple tools) would be to first trace it out with a marker or a pen then using a drill and proper drill bit drill two holes (one at each end of smartphone hole) and cut out the hole using a jigsaw. Note that you may need to do some fileing additionally.

In this step you're gonna need to do some measuring, although you could get away without using a ruler, probably the easiest approach would be to cut these pieces out one by one. So you mark where you need to cut, and then cut that piece, and then you measure out the second piece, and then cut that one, and then you repeat this process with the third piece. I wanted to use miter corners in this project so I used a manual miter saw and box to cut those pieces out.

At this point, I painted those square dowel rods, but I repainted them later, so this is an optional step

In this step, I used wood glue and super glue. So I applied wood glue and then to position those pieces and put them together I used superglue (with activator spray), after that, I used clamps to hold them together.

The function of those popsicle sticks is to lift/hold the phone upwards, and this small piece is required to direct the sound that is coming out of the speaker and making it is fairly simple, at first I was stacking them up (using super glue with activator spray) one by one and I stopped after 4 pieces (to popsicle sticks each cut in half).

I superglued this piece to the board slightly left on the board because the speaker is located slightly right on the smartphone. To sum it up this piece acts as a spacer so the smartphone speaker does not touch the wooden board.

In this step glue the top piece on those three square-shaped dowels. And then use some clamps to hold them together until the glue dries.

In this step, sand those rough edges if there are any, I used an angle grinder with a sanding disc, the disc that I used was slightly warn out so I ended up with a few burn marks left on the wood, and I thought they look good so I didn't sand them off later.

I mentioned in one of the previous steps that I repainted those square-shaped dowel rods and I repainted them in this step. First I used tape to tape the parts that I didn't want to be painted, and then I painted those square-shaped dowel rods.

This is an optional step, but it does make this amplifier look more high end, anyway the idea behind this "cushion" piece is that this piece prevents the sound from escaping through the smartphone hole. Cut the cushion piece from a larger piece of sponge foam, easy way of attaching this would be to first position the cushion piece opposite from where it should be then add some hot glue, and then push the cushion into place. And also one more part of this step that is also optional is to cut two more pieces (a bit longer than the cushion piece) of sponge foam, these two pieces fit inside of the speaker box, but you would probably need something like a screwdriver to push those into place along the edges of the amplifier.

Cutting those pieces out is fairly easy using a pair of scissors.

In this step apply some finish, I used linseed oil, and after that add some rubber legs and that is it for this project!