This Instructable is based on a workshop that I do for primary schools. Students would create a DIY cardboard speaker. I've modified that a little to 3D printable headphones of my own design, but still using a simple copper coil and magnet system to create sound output. It's a great project for anyone and you may learn something about electromagnetic induction!

This you will need:

Access to a 3D printer.
STL files from my thingiverse account.
enamelled copper wire.
headphone cable with 3.5mm jack.
4 10mm x 3mm round magnets (I use neodymium).
small piece of sandpaper.
Soldering iron, solder & shrink wrap/electrical tape.
Glue

Step 1: Print Headphones

The STL files that you can download are to make a modular set of 3D printable headphones.

Print the number of pieces for the size you need and choose from the different types of corner pieces.

Example of parts you need to print for one set of headphones:

2 x ears pieces.
2 x corner pieces.
2 x 40mm spacers & 1 joiner for left side.
2 x 40mm spacers & 1 joiner for right side.
3 x 40mm spacers & 2 joiners for top.
2 x coil membranes

Download STL files from my Thingiverse.

If you do not own a 3D printer then you can find own near you with at 3dhubs.com

Make sure you do not yet connect or glue the two earphone parts as we will need to use the square hole at the top for access later and to test the speakers work.

The printed parts should fit snuggly into each other but you may need to glue them together for strength. Once assembled the headphones should be hollow for you to insert wires if necessary.

Step 2: Prepare Coils and Magnets

In this step we will create the speakers that will be inserted into the headphones.

Take the length of enamalled copper wire and wind it around a pen several times to make a small coil. Remove from pen and then wrap the lead wires around the coil a few times to hold the coil together like in the picture above with the 5p coin. Leave some wire at both ends to use to connect to the headphone cable.

Use a small piece of fine sandpaper to gently remove the enamel from both ends of the wire. It will appear brighter like a shiney new copper coin does. Repeat both the above tasks so that you have two copper coils.

Step 3: Magnets & Membranes.

Membranes

You can use the STL file I have created to make the speaker membrane or you can simply use a piece of card with a hole instead that you can insert into the earphone part.

Alternatively, do what I did. Use some sellotape and tape across one side of the membrane. On the other side stick the coil to the tape that is across the hole. Then tape across that side too, trapping the coil in between. Remember to let the copper leads to protrude for the bottom of the membrane.

Repeat this process so that you have two membranes with coils.

Insert the membranes downwards into the slot in the earphone part. Thread the copper leads wires through the hole in the bottom so we can solder to the headphone cable. You should glue the membrane so that it does not move about.

Magnets
Take one of the earphone parts and 2 of the magnets. I'm using 10mm x 3mm Neodymium magnets. They are strong and the electromagnetic field they produce will create more sound.

You should be able to see the circle shaped magnet locators. One magnet goes either side and are held in place purely by the magnet attraction. You can glue them if you prefer.

Repeat this for the other side too.

Step 4: Solder the Wires and Connect to the Coil.

Take the headphone cable making sure that one end has a 3.5mm stereo jack and the other end is the stripped wire.

You should have something like the image above. 2 plastic cords, each containing 2 wires. Here you can see blue and red enamalled wires. Using the sand paper like you did previously. Lightly sand the enamel to bare the copper wire underneath.

If you want to use shrink wrap to cover the solder joins. Thread one piece over each copper coil wire now. Althernatively you will need to use electrical tape to insulate the wires.

Soldering

You can tin the copper wires and the headphone wire if you now how to, prior to soldering. If not you can twist and solder one of the copper coil wires to one of the wires from the first cord. The other copper coil wire can be twisted and soldered to the other wire. You can move the shrink wrap to the join and apply heat to shrink. Or use electrical tape instead.

Repeat this for the second speaker too.

Step 5: Testing and Finishing

Testing the speakers

Plug the stereo jack into your phone and play some of your favourite music. Put your ear to the coil. You should be able to hear music. It wont be as loud as your are used to with your usual headphones. But hey! It's not bad for a bit of copper wire and a couple of magnets.

Once you have successfully tested it you can attach and glue the earphone parts to the rest of the headphones and enjoy your music.

I tested this one and it works great, though it does make me look a little like a Cyberman from Dr Who! If there are enough comments I may actually add the photo I just took!

I hope you like the instructable. Pleae vote for me in 3D printing competition.