A coffee cup loud speaker

In the blog post “Musical Coffee”, I used a loud speaker that I had made out of a coffee cup.  This (hopefully brief) post is just to explain how the speaker was made in order that you can make it at home.  Firstly though I need to thank Jose Pino who had posted instructions for a very similar speaker (link) and from whom I got the idea for this speaker. Secondly, I ought to say that this video is the making of the actual speaker used in Musical Coffee.  Some further optimisation is clearly possible.

To make a loud speaker out of a coffee cup you will need

  1. A take-away coffee cup
  2. Paper and some scissors
  3. Sticky tape
  4. OLD ear-phones
  5. copper wire (0.28mm diameter worked well)
  6. superglue
  7. a magnet (a rare-earth magnet is best)

Instructions

Step 1: Make a paper “jacket” for the magnet. This jacket is there so that, eventually, we can pull the magnet out from the coil that we are going to wrap around the magnet.

Step 2: Make a second jacket with feet.  This jacket is to support the coil.  The ‘feet’ will allow us to easily superglue the jacket to the bottom of the take-away cup.

Step 3: Protect the magnet with a piece of paper. This paper just sits between the magnet and the cup.  It is to stop the magnet from getting glued to the cup in the next step.

Step 4: Glue the jackets to the cup. This is where the feet in step 2 come in.  Glue the outer jacket to the cup, the magnet should still be inside the jackets at this point but DO NOT glue the magnet to the bottom of the cup.

Step 5: Wind the coil. I used 100 turns of 0.28mm diameter (enamel coated) copper wire.  This worked quite well but could easily be optimised.

coffee cup loud speaker, cup speaker

The coffee cup speaker in an improved design

Step 6: Attach the legs. If I were to do this again, I would use cocktail sticks as in the photo here. In the video Musical Coffee though, I used bits of polystyrene cup stuck on with glue after having tried using straws. The aim is to make the cup fairly rigid so that the vibrations from the coil at the bottom of the cup are transmitted into the fluid of the coffee. The legs made out of bits of polystyrene cup worked well enough to hold coffee in the cup while it was being used as a loud-speaker but the cocktail stick design worked much better.

Step 7: Remove the inner paper jacket.  This is so that when you turn the coffee cup over and mount it onto a piece of card, the magnet will fall out onto the card centred with the coil.

Step 8: Glue the speaker and magnet to the card. Look again at the picture.  See that the magnet is on the card and directly below the coil? This is how it should be attached. Depending on what you used for legs, either superglue or wax (as used in the photo of the speaker with cocktail stick legs) would be good to hold the speaker in place.

Step 9: Be brutal with your ear-phones. Cut an ear-bud off.  There should be two wires left exposed.

Step 10: Solder the ends of the coil to the wires from the ear-phones. If you are not happy soldering, remove the enamel coating of the wire used for the coil with a sharp blade and then twist this wire with the ear-phone wires before fixing it with tape.

You are ready to go.  Let me know how you get on in the comments section below. Have fun.

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