Cardboard Horn Amplifier

Exponential Horns are amazing acoustical machines with no moving parts. They also look gorgeous!

Horn shapes were widely used by the ancient Greeks. They designed circular arenas which opened like funnels where if performers whispered on stage, their voices could be clearly heard from the uppermost seats. This is because of the unique characteristics of the acoustic horn which maximizes the efficiency with which sound waves are transferred to air from their source.

When the first gramophone was invented in 1898, its horn amplified the minute mechanical oscillations of a pin running along a disc to produce sounds that could be heard by the human ear.

In this Instructable, using a single sheet of cardboard, I created an amplifier that turns sounds from a smartphone into music that can fill an entire room.

Step 1: Designing the Horn

To design my horn, I used Fusion360 to create a loft shape from 3 hexagon.
I then unrolled one of the sides of the lofted shapes to give me a flat pattern, I also added tabs so that when I assemble the horn these tabs will lock into each other.

I have attached a PDF with my patterns that you can use to either print and then hand cut or laser cut your cardboard!

I have now also included Letter sized tile print too!

To achieve a wrinkle-free smooth curve in the card board I scored the cardboard at every flute.

You will need to cut through the top and middle layer of the cardboard, this allows the cardboard to become flexible.

Step 2: Assembly Time!

Now that you have cut all the cardboard for the horn and dock, score the dashed lines and assemble as shown in the images below.

Use tape to complete the dock.

Next assemble the horn by interlocking each 'petal' of your horn as shown ensuring that each tab is secured.

Step 3: Cue the Music!

Insert the horn into the phone dock and your speaker is ready.

Put on your favorite music and enjoy pure and simple amplification!

Comments

[theguywitheyebrows]

this is absolutely amazing! i am printing now, i'll tape together the print-out and find a cardboard large enough to lay the full print on!! i have a pile of cardboard boxes saved to use for projects like this one!! this is awesome, thanks for doing all the detail work and sharing it with us!! pictures to come soon!!

[theguywitheyebrows]

although i feel like i could have saved an inordinate amount of paper if you had drawn only one petal and the base. as such, this pattern tile-prints on 20 sheets, with margins, that have to be taped together before the cardboard pieces can be cut. could printed on 3-5 pages instead with only one petal, since all sides are symmetrical. course, i could be mistaken and the 3 petals could all be different....buuuut that seemingly defeats the purpose of the arduous computer mapping.

[Pushan Panda]

Have now added letter sized PDF prints in step 1!
Meant to include this earlier, sorry for the hassle!
You are right, each petal is symmetrical.

[mccanlessdesign]

Well, each petal is "identical" to the other petals, not "symmetrical" themselves - they all have to be cut from the same desired face of the cardboard - there is a left and right side to each petal. This may be just a language detail.

[theguywitheyebrows]

i got the first one cut out and used it as a template to cut the rest of them. i didn't keep the same face of the cardgboard, so mine's ugly and i have no tape to keep it together. when the tape reappears, i'll secure it all together and see how well it works!!

[Pushan Panda]

Each petal is identical and symetrical along the horn's central axis.

[adhitya.venkat12]

Is the Horn Amplifier functionable?

[orion3119761]

This was an awesome "attention to detail" project
I dont have patience and wanted to hurry up and put it together to see how it looks...not bad, but u can see I had to use tape but awesome fun for my grandson!!!! And yes they was leftover yard sale signs...lol

[heligato]

Excellent..!! Many thanks..

[mccanlessdesign]

Hmm - instructions aren't very thorough, and the rear phone compartment doesn't really assemble or "wrap" correctly. Also, seems like the phone compartment is sealed off from the horn volume? Tried with two phones - doesn't amplify or direct the sound in any noticeable way with either; three people listening and trying various positions.

[Pushan Panda]

Congrats on making a horn! I'm sorry it's not working well for you, my phone has it's speakers at the very bottom, maybe try enlarging the "cradle area" and sliding parts of your phone into it? Do keep in mind this is entirely made of cardboard, and manage expectations accordingly ;)

[seamster]

I wondered the same thing. I think if you cut a hole in the "cradle" area that holds the phone that matches up with the location of your specific phone's speaker, that would resolve this issue.

[Pavelino]

Great project, tsk for sharing, will try it. I actually have a few speaker drivers and will try the horn with them. Horns work very well, have a pair of Altec Valencias loudspeakers, from the 70's, that use horn for the higher frequency sounds, wonderful, technology that every audiophile of today knows and respects in spades.

[MartinMeiss]

Neat project, but I object to calling the horn an amplifier because it doesn't add any energy to the acoustic signal. Rather, it directs the signal in a limited direction rather than letting it dissipate in all directions. But anyhow, a good use of cardboard!

[golfturfpro]

Definition of amplify?

[MartinMeiss]

Here's what Dictionary.com says:
verb (used with object), amplified, amplifying.

1. to make larger, greater, or stronger; enlarge; extend.
2. to expand in stating or describing, as by details or illustrations; clarify by expanding.
3. Electricity. to increase the amplitude of; cause amplification in.
4. Archaic. to exaggerate.

The original poster's use may be a borderline case. The sound would definitely be louder for one standing in front of the horn, but presumably quieter if one were behind it. But in any case, to total energy of the signal is not increased.

[golfturfpro]

https://www.merriam-webster.com/dictionary/amplify

[Diez66]

An acoustic horn or waveguide is a tapered sound guide designed to provide an acoustic impedance match between a sound source and free air. This has the effect of maximizing the efficiency with which sound waves from the particular source are transferred to the air.
Learned that in collage and it is also on Wikipedia et al.

[tompotter]

For those of us with fewer computer/printer skills, could you please revise your PDF download to print on multiple sheets of "standard" letter-size paper. Each of your petals should fit, and it would make the assembly a lot easier for millions more of your followers. Thanks.

[Pushan Panda]

Have now added letter sized PDF prints in step 1!