Wire gauge on a simple speaker

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Hey
I've built a speaker and the cone is about 20cm in diameter. I need help choosing the wire gauge for the voice coil though. When I look at this chart http://www.powerstream.com/Wire_Size.htm I can't really see anything that will work. My stereo puts out 50W and if I want the resistance to be about 8 ohms the current would be the sqareroot of 50/8, which is 2,5 (I know speakers are more complicated than this but I'm not there yet). However, according to that chart that would mean I need a wire with a diameter of 0.45mm. The thickness of that wire and the length that I would need to get 8 ohms makes the mass pretty stupid. And on a normal voice coil you only see one "layer" of wire.

Am I supposed to just go with a higher wire gauge (0,2mm) and not play on full volume in order to not burn it? If the wire was about 0,2mm I could get a pretty nice voice coil with only 1 layer of wire. The diameter of the coil is 5cm.

Help is very appreciated.
Feel free to elaborate too, I might do a high school project about this soon.

Edit: It might not be 1 layer after all but it's still less than what I would need in the example above.
If I made a 4-layer coil that's 3cm high using 0,25mm wire the resistance would be 26 ohms and the current would be 1,3A. That wire should handle 0.86A so I'm getting closer lol
 
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  • #2
Tom.G
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Unless you play slow organ music at full volume, don't worry too much about dissipation in the voice coil. Most music has power peaks ten times or so the RMS value. That means for your amplifier to handle 50 Watts without distortion, you will be running 5 Watts or less "most" of the time.

Since you are designing and building the speaker, use a wire size you are comfortable with; if it burns up, go down 3 gauges in wire size (that doubles the current capability).
 
  • #3
davenn
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Hey
I've built a speaker and the cone is about 20cm in diameter. I need help choosing the wire gauge for the voice coil though. When I look at this chart http://www.powerstream.com/Wire_Size.htm I can't really see anything that will work. My stereo puts out 50W and if I want the resistance to be about 8 ohms the current would be the sqareroot of 50/8, which is 2,5 (I know speakers are more complicated than this but I'm not there yet). However, according to that chart that would mean I need a wire with a diameter of 0.45mm. The thickness of that wire and the length that I would need to get 8 ohms makes the mass pretty stupid. And on a normal voice coil you only see one "layer" of wire.
you are mis-understanding the difference of Impedance and Resistance
A speaker can have an impedance of 8 Ohms ( 4 Ohms and 16 Ohms also common)
BUT its electrical resistance will not be 8 Ohms ( the resistance of the coil). It is likely to be much less, maybe only 1 Ohm or less


Dave
 
  • #4
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Unless you play slow organ music at full volume, don't worry too much about dissipation in the voice coil. Most music has power peaks ten times or so the RMS value. That means for your amplifier to handle 50 Watts without distortion, you will be running 5 Watts or less "most" of the time.

Since you are designing and building the speaker, use a wire size you are comfortable with; if it burns up, go down 3 gauges in wire size (that doubles the current capability).
you are mis-understanding the difference of Impedance and Resistance
A speaker can have an impedance of 8 Ohms ( 4 Ohms and 16 Ohms also common)
BUT its electrical resistance will not be 8 Ohms ( the resistance of the coil). It is likely to be much less, maybe only 1 Ohm or less


Dave
Thank you, this helped! Calculating the impedance seemed more complicated but hopefully it won't blow up if the resistance of the coil is 1 or 2 ohms. :)
 

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