If we told you that we were going to show you how to make a speaker out of a paper cup, you would probably say, “oh yeah– we’re going to make a string phone.”
But we’re not going to do *that* project.
What if we told you that you would be able to hear the music playing on your phone if you plug your paper cup speaker into your phone’s headphone jack? No way, right?
Yes way. It blew our minds too when we heard music from our paper cup speakers.
Read on to learn how speakers work and how to build your own speaker with just a few common supplies.
This is a great STEM project to do with school-aged kids as a homeschool activity or in a makerspace. Some steps are a bit fiddly and likely required the help of an adult.
This project and all Geek Pack Hack activities must be undertaken with a suitable adult completing their own risk assessment and supervising their children at all times.
We’ll list the parts we used and then give you step-by-step instructions for how to make a speaker.
You can check out our video tutorial here and subscribe to our YouTube channel to keep up with new projects.
Everything is explained below as well (but you have to watch to see what wacky surprise the boys had for Dad this time…)
Sound moves through solids, liquids, and gases as vibrations.
As a sound wave moves through space, each individual molecule gets pushed by the previous molecule and, in turn, propagates the wave along to the next molecule.
You can visualize sound moving through air by the way that waves move through a stretched-out slinky.
We can imagine that each loop of the slinky is like one air molecule. When we give one end of the slinky a push, we can see how the sound wave can be carried along the slinky and through the air.
You can read about electromagnets in our post about building a crazy electromagnet doorbell.
In a nutshell, an electromagnet is a coil of wire with electrical current flowing through it.
When the current stops flowing through an electromagnet, the coil stops being magnetic.
Permanent magnets, on the other hand, are magnetic all the time.
How Speakers Work
A speaker works by attaching an electromagnet to some sort of flexible cone and putting it close to a permanent magnet.
The sound transmitted through the wire as an electrical signal changes the magnetic field of the electromagnet, which attracts and repels the nearby permanent magnet.
This makes the electromagnet vibrate.
Since the electromagnet is attached to the flexible cone, the cone amplifies those vibrations and propagates the sound through the air.
Supplies to Make a Speaker
Audio device (there is a small risk that you could fry it with your home-made speaker!)
Steps to Make a Speaker
Step 1: Make the electromagnet and tape it to the cup
Cut (or break off) an 8 ft-long piece of the enamel-coated magnet wire.
Leaving about 8 inches at each end, wind the rest of your wire loosely around something round like a D-battery.
Carefully remove your coil from the battery. Wrap each end around the coil a couple of times to keep the coil from unraveling.
Use a piece of tape to attach the coil to the outside bottom of your cup (leaving the wire ends free).
Step 2: Attach the audio cable
We have to remove the enamel coating from the last couple of inches of each end of the wire. Use a piece of sandpaper to rub the exposed ends of the wire.
Then, prepare your audio cable by cutting it in half with your wire strippers. You should see two insulated wires– the left and right audio channels. You should also see a third uninsulated “ground” wire.
Use the wire strippers to strip the insulation off of one of the insulated wires inside the audio cable.
Twist one of the wire ends of your electromagnet coil together with the insulated wire that you just stripped.
Then, twist the other end of your electromagnet coil together with the uninsulated ground wire.
(Note: we found that we could actually connect our electromagnet wires to *any* two of the wires inside of the audio cable. Even connecting them to the two insulated audio channel wires and leaving the ground wire unconnected worked! Why? We have no idea, but we’re investigating… Let us know if you have an explanation!)
Step 3: Put the permanent magnets on the speaker
Put a couple of small ceramic batteries inside and outside of the bottom of the cup so that they hold each other on.
You’re ready to try out your speaker!
A note of warning: we did successfully use our speaker with our iPad, but we measured the resistance with a multimeter first to make sure there wasn’t a short-circuit anywhere.
We’d suggest you use your speaker with an audio device that isn’t too important to you.
Or, you can learn how to use a multimeter and then just check that there are a few ohms of resistance in your circuit before plugging it into your new phone!
If you don’t hear sound coming through your speaker, the best way to troubleshoot is using a multimeter. You can check for continuity through your electromagnet coil– you might need to sand off more of the enamel coating from the ends of your coil wire to make for a good electrical connection.
If you enjoyed this project or have questions, please let us know.
Are there other projects you’d like us to build? Please leave us a comment!
Check out all of our cool engineering projects.
We also have a helpful basic electronics page that teaches skills such as how to use a breadboard and multimeter.