How to Make a DIY Phone Amplifier

Learn how to make a stylish and functional passive DIY phone amplifier using plywood! This beginner-friendly DIY project makes a perfect gift for anyone.

Have you heard the trick of placing your phone into a cup to make it sound louder?

That is called a passive phone amplifier. It’s passive because it doesn’t use any electricity or batteries. The amplifier naturally boosts the sound from the phone, making it louder.

Even if the physics behind it sounds complicated, the project is super simple all you need to do is make a channel for sound to travel through. I have the full tutorial for you below.

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How to Make the Phone Amplifier

Step 1: Design the Amplifier

I didn’t include plans for this because all phones have different sizes and dimensions. You will have to create the size and plans for the phone you want to use it with.

The above diagram shows you the various layers. I made all my squares 4 1/4″ x 4 1/4″, but this will change based on the size of the phone.

• Layer 1: The slot should be the width of the phone +1/8″, and the thickness should accommodate the phone along with the cover. You want to have at least 1/2″ on both sides of the slot

• Layer 2: The slot is slightly smaller in width than the slot in Layer 1. You want to make sure that this slot is large enough so it doesn’t obstruct the speakers on the phone. In my case, that was about 1/4″ on both sides.

• Layer 3: This is a small slot, and you can decide what you want it to be. I made it 1″ wide. This is where the sound starts to bounce and amplify. This slot also opens up to the edge to form the speaker shape.
• Layer 4: No slot. Just the speaker shape.
• Layer 5: No cuts. This is the bottom of the phone amplifier.

Step 2: Cut the Layers

• Make starter holes in the slots to make space for the jigsaw blade to go in.

• Clamp the board well. This can be a bit tricky because the squares are small, and you need space for the jigsaw to cut.

It took a few iterations of clamping the board on the edge and getting all the cuts done. Second, it may be safest to mark all of these cuts on a large board, cut the slots, and then cut them down to the squares.

Step 3: Assembly

• Apply wood glue on each layer and glue them up together one by one.

Make sure to wipe off any glue squeezed out at every step because it will be almost impossible to clean up later.

• Clamp everything together and allow it to dry overnight.

When you clamp the boards, they will tend to shift. Make sure that they stay aligned and use two clamps in opposite directions to counteract the forces.

Step 4: Final Touches

Once it has dried overnight, you can remove the clamps. The passive speaker now works, and you should be able to test it out. But there are a few more steps to make it look presentable.

• Clean up any glue residue and squeeze-outs using a sander.
• For the insides, you can use a thin chisel to remove any glue squeeze-outs and sandpaper wrapped around a pencil to get inside the tight spaces.

• Route out the edges of the cube using a trim router with a 1/4″ round over bit. This is totally optional, but I like that it adds the soft corners. See how to use a router.

You can also quickly run a sander along the edges. Be careful with this, though, so you don’t get uneven edges.

• Apply an oil base top coat to bring out the layers and seal the phone amplifier.

That is it! That is the phone amplifier.

Of course, I had to test it out and get some actual quantitative data. There is a 10-15 decibel increase in volume when the phone is added to the amplifier.

It is a fantastic gift idea for anyone who loves listening to tunes, podcasts, or watching videos. It’s perfect for anyone who spends time at their desk or likes to keep things simple and stylish. Plus, it’s handmade and can be easily customized. You can add decals, wood-burned or engraved features, and more!