I've made a couple virtual jukeboxes but of course did not document the build. I've been thinking about making a third with a steampunk theme. The intent of this project was to figure out the geometry needed to make a steampunk speaker. The final version will be made of copper or brass sheet, but this mock up is made of paper. the geometry can be scaled up or down once the size of the final version is determined.

Step 1: Materials

π (3.14159265358979323846264338327950288419716939937510582097494459230781640...)


Drawing tools (or a drawing program)

Poster board

Spray Mount

Scissors or xacto knife


Metallic Spray Paint

Step 2: Geometry

The first thing do do is to figure out a few of the dimensions, the size of the big end, the size of the small end and the length.

Step 3: More Geometry

Then you determine how many facets you want to break it into. The circle becomes a polygon, in this example I broke it into an 8 sided polygon, thus 8 facets. If you want the horn to look smoother you would use a polygon with more sides. Above is an example of an actual gramophone horn with 10 facets.

Then you divide the side into equal increments, I set mine at 1" to keep it simple.

Then you measure length of each of these lines on the side view. these lengths are the diameter of the horn at 1" increments.

Here is where π starts to come into play. π x diameter is the circumference of a circle, π x the length of each of these lines is the diameter of the cone at that location. we want to break the circumference into 8 straight pieces (sections of the 8 sided polygon) so we divide the circumference by 8 (π x D/8) to get the length of each segment at 1" increments. This is probably easier to understand if you just look at the pictures.

Step 4: Finally the Fun Part and No More Geometry

Layout the pieces for printing, I was only able to get 7 of 8 on a single sheet of paper. Of course that all depends on the size of the horn you are trying to make. I spray mounted them to a piece of poster board and cut out the pieces then folded them at the vertical lines.

Step 5: Glue It Together

Then you start gluing the pieces together one straight line segment at a time, until you complete the circle. This would be soldered together in the brass or copper model.

Step 6: Paint and More

Then I spray painted it just to see how it looked, and since I went through all that and then spray painted it I thought I would put together a little cell phone amplifier box to see how that would work. Surprisingly it does amplify the sound even though my intent was just to mock up the build, not the acoustics. The next step is to study the best geometries to improve the acoustics, up-size the horn to work with a real speaker and build it out of brass or copper.

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