DEVELOPING THE COPPER COIL INSIDE THE SPEAKER Speakers have to be 8ohms of resistance - this is, so they do not cause amps to over heat. There is little risk of blowing up the large paper speaker - as they are not prone to overheating or tearing. Which is good. What you want - is to use the most wire possible, in a tight space, keeping the resistance below 8 ohms. Which can be tricky to calculate. Firstly you need to work out the weight of the wire: I am using two wires.
0.12mm thick : 36/37 AWG
0.212mm thick : 32 AWG.
I haven't discovered which wire will produce the loudest sound, so I have decided to try both. Both wires are fiddly and easy to tangle - which is not ideal.
The first step is to calculate how many lengths of wire you will use and how long each length will be - to create such large speakers, and to use enough wire to create decent vibrations, you need to put the wires in parallel - decreasing the over all resistance.
I like to work out how much resistance is in one meter of each wire (lets start with the 31 AWG - for ease. I like to use this calculator - I find it is a bit off, but is a good starting point: https://www.inchcalculator.com/wire-gauge-size-and-resistance-calculator/ It tells me that the 32AWG wire has 1.72 Ω per meter. 10m = 4.884 Ω 20m = 9.768 Ω 30m = 14.652 Ω
According to my measurements, I have more like
6.6 Ω per 10m
13.2 Ω per 20m
19.8 Ω per 30m
26.4Ω per 40m
Now to calculate how many lengths of 40m I should use in this speaker
Here is the basic formula, for working out resistance in parrallel... but I like to cheat and use an online calculator
https://www.omnicalculator.com/physics/parallel-resistor
Ideally I would like 5 x 32 ohm lengths of 6 x 40 ohm lengths. Lets try the second option (why not?) Which makes each length need to be 70m (approx!) A total of 420m per speaker! SPEAKER ONE 32AWG (.212 mm) Wire 70m (40ohm) x 6 = 8 ohm
Speaker TWO 30 m (40ohm) x 6 = 8 ohm
Then the wire lengths have to be measured out. I found that using a metre rule and then winding the wire around a toilet tube to be effective. You can only do this in 5m stages, any more than this and the wire risks becoming quickly tangled.
Then I set up a board with nails hammered in. I was inspired by wire bending crafts like this:
I constructed my own grid, you can see in the first picture of the blog - this was initially done to a small scale, and these initial paper speaker tests can be found in an earlier post. Now, wanting to work larger, I constructed my own jig on a large scale. The wire was wound around the nails and glued into place. It created an amazing grid shape. I found using toilet paper under the nails provided a suitable support for each corner point of the mesh.
The first time the paper speaker was made, I did not have a paper making frame larger than A3. So the paper had to be created in layers. I was very unsatisfied with how it looked, but the speaker worked well. I have dedicated a page to making paper frames, as making a sheet of paper 80cmx80cm was a challenge in itself and it took a great deal of trial and error.
My first prototype was complete. Although it looked ugly, the proof of concept worked, all it took now was some serious refinement to get it to look beautiful.
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