Homemade Horn

We are going to make a very simple horn, with homemade (or easily available) materials and put it into operation to understand how it works.

1. Large stopper (for example from a bottle).
2. Silicone and the gun.
3. Small nut.
4. Two neodymium magnets.
5. A sheet of acetate.
6. Paper.
7. Enameled copper wire.
8. An audio amplifier (or mount it).
9. Power source, power supply 9V.

We heat the silicone, for this we will need the silicone gun connected and simply wait the required time specified by the manufacturer.

We place the small nut in the center of the cap and check that the cap does not have any relief on the edges. In this case, file the edges so that they are completely flat, since later we will place the acetate sheet.

We leave the nut fixed in the center of the cap with the hot silicone. BE VERY CAREFUL NOT TO TOUCH THE SILICONE IMMEDIATELY AFTER PLACING IT.

We cut a piece of paper approximately 5cm long and 1cm high. The height will depend on the size of the plug, in our case it will not be 1cm, but approximately 0.7cm

We roll the paper on a cylindrical surface with a diameter millimeter larger than the neodymium magnets and fix the paper so that it remains with that diameter, later, with 2 meters of enameled copper wire and leaving a 5cm margin on each side of the wire, We begin to roll it around the piece of paper so that it looks like the image, finally, we apply hot silicone around the coil so that it remains fixed. (In the image you can see two coils of different heights, both valid for different types of caps).

We place the two magnets on top of the cap nut, then we stick the coil in the center of the acetate sheet with hot silicone and, when it dries, we fit the coil so that the magnets are inside the hole in the paper. Finally, we leave the acetate sheet fixed on the edges with hot silicone (4 drops of silicone around the circumference of the plug is enough).

IMPORTANT: Before placing the acetate sheet, we need to drill the plug on one side to allow the 5cm of wire that we have left to pass through, since we will need to connect it to the negative and positive input of the audio amplifier.

The horn itself is now finished, and all that remains is to put it into operation. The easiest method? Check it by connecting it with a phone. For this we will need an audio amplifier since the signal provided by the phone with a 3.5mm Jack is too low.

Then we connect, as we mentioned above, the edges of the enameled wire to the input of the amplifier. Regardless of which pin we connect to the positive and negative, it should work.

In our case, we have used a 9V battery, which is more than enough to power the circuit.

Now all that remains is to connect the battery to the audio amplifier, connect the amplifier and a phone using a 3.5mm jack and try playing something on the phone.

Why does it work?

A horn works through the interaction between a permanent magnet and an electromagnet. The permanent magnet is fixed to the housing, while the electromagnet, connected to a membrane, generates a magnetic field when receiving an electric current. When an audio signal is applied to the electromagnet, it vibrates in rhythm with the signal thanks to the forces of attraction and repulsion with the permanent magnet. These vibrations are transmitted to the membrane, which converts them into sound. In this case, the housing is a plastic cap, the permanent magnet is neodymium magnets, the membrane is an acetate, and the electromagnet is a coiled wire.

In this video we will put the speaker into operation, we can see that if we raise the volume too much, the speaker is saturated and begins to sound quite regular. It is quite curious that with so few things a song can be played.