Cardboard Speaker

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The Cardboard speaker is a device that takes an Audio Signal through an eighth inch audio jack and converts it to a sound. It is made with magnet wire and cardboard, along with an amplifier board, and that's it!


The cardboard speaker was part of the May 2017 kit for the Monthly Make-It along with the Electromagnet Kit, and the Popsicle Stick Harmonikazoo


!!Note: If you order a kit from us do not throw away the box we ship it in. It is the source of cardboard you will use for this project!!

1. Cardboard Base x1

2. Cardboard Rectangle x1

3. Cardboard Spring Strips x2

4. Amplifier Circuit Board x1

5. 8th Inch Audio Cable x1

6. Alligator Clip Wire x2

7. Vinyl Electrical Tape

8. Double Sided Tape

9. Water Bottle

11. 24' (7.3m) Magnet Wire

12. 3/4" Neodymium Magnet

13. 1" x 3/4" Wooden Dowel

Optional: Hot Glue



This project has two major parts. First we will build a speaker out of cardboard, magnets, and magnet wire. Then we will connect that speaker to an amplifier board and a ⅛” audio cable so we can play sounds from our various audio devices out of our speaker.

The speaker consists of an electromagnet made by coiling wire around the neck of a soda or water bottle, and a stationary magnet mounted to a piece of cardboard. Our audio signal will turn our electromagnet off and on. This changing magnetic field, combined with the field created by the permanent magnets, will cause another piece of cardboard to rapidly vibrate in a way that produces the audio signal from our cable.

CBSpeaker08SoundDiagram.jpg How a Speaker works: by Plusea CC Attribution Share-Alike Generic

Step 1: Cut The Top Off The Water Bottle

We will use the very top of the water bottle as a spool to coil our magnet wire around to create our voice coil. The section you cut off should have a small lip below the threads for the cap, as well as a larger lip on the bottom. We can easily coil our magnet wire between these two lips.


Step 2: Wind the Voice Coil


Carefully wind the voice coil around the bottle top. You will need to have access to both of the ends of the wire when you hook up your speaker, so make sure that you don’t accidentally cover one of them as you coil. When you’re done it should look like this:


Step 3: Tape The Voice Coil

Tape the coils of wire to prevent them from uncoiling. Trim the tape when you’re done.


Step 4: Remove Insulation From The Wire

The wire we use for the voice coil is a special kind of wire called “Magnet Wire” which has a very thin enamel coating as its insulation instead of the plastic insulation that most wire has.

We need to remove this coating to connect the audio source to our voice coil. We use sandpaper to sand off the insulation.

CBSpeaker14SandWires.jpg CBSpeaker02StrippedWires.jpg

When the insulation is removed, you should be able to see a lighter-colored, differently-shiny metal on the inside of the wire.

Step 5: Cut Out the Speaker Cone

The speaker-cone can be any piece of material that can be attached to the voice coil. We are going to make the simplest speaker possible, which will just be a flat piece of cardboard. More elaborate speaker designs, and designs using other materials can sound better and have different acoustic properties.

Cut yourself a piece of cardboard about 5”x3”. You can use almost anything, but the cardboard boxes we use for shipping are are great.


Step 6: Attach the Voice Coil

Use a piece of double-sided tape. We will attach the lid for the bottle to the cone.

CBSpeaker13TapeOnCone.jpg CBSpeaker05CoilOnCone.jpg

This will allow you to build different cones using different materials and other bottle-caps. The you can swap them out to experiment with different designs and sounds.

Step 7: Make Cardboard Springs

These supports will allow the cone to more easily move up and down.

Cut two lengths of cardboard, about 6”x1 ¼”.


Do an “accordion fold” on these lengths of cardboard. Fold them into around 4 even lengths. Don’t worry about being too precise -- you can easily make more and experiment.


Step 8: Attach Springs the Speaker Cone

Use a couple of pieces of tape.


Step 9: Make the base of the speaker

Cut yourself another rectangle, around 8”x5”. Put a piece of double-sided tape in the middle of one side. CBSpeaker18TapeBase.jpg

Attach the wooden post to the double sided tape on the base, and then attach magnets to the post using another piece of double sided tape.


Step 10: Position The Voice Coil

Place the voice coil over the top of the post and magnets. Tape the springs to the speaker base so that the cone can move up and down.


Step 11: Attach the Amplifier Board

Attach the amplifier board to the other side of the base using double-sided tape.


Step 12: Orient The Amplifier

You’re done making the speaker, now we just have to send our audio signal to it. To do that, we have to attach the amplifier to the speaker and to our audio cable.


Look at the amplifier board. One side should have 4 wires coming off of it. The other side should have 5. Align it so that the side with 4 cables is to your left.

Step 13: Power The Amplifier

The two wires on the top-right attach to your battery pack to power your amplifier. The top wire is ground, and should go to the black ground wire on your battery pack. The one right below to it is power and should connect to the red wire on your battery pack.


Step 14: Connect The Audio Cable

The bottom three wires on the right side of the board connect to your ⅛” audio cable. The top of the 3 is the “right” channel signal. The middle is ground. And the bottom is “left”. “Right” connects to the white wire in your audio cable. Ground connects to green. Left connects to red. The black wire on your audio cable is for microphone output, which we aren’t using in this project.


Step 15: Connect The Speaker

The left side of the board contains two pairs of output wires to connect to two speakers. Each speaker. We will plug alligator clips into these wires and clip them to the sanded-off ends of our voice coil wires.


Since we only have one speaker, we should pick one of the channels, either left or right. It does not particularly matter which one. You can make or find another speaker to connect the other channel to if you want stereo sound.



You’re done! Plug your speaker into your audio source of choice and give it a listen!



This documentation describes Open Hardware and is licensed under the CERN OHL v.1.2.

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