N Cook wrote in message
...
The blurb technical said 300W RMS handling for this 12 inch speaker.
Now it is blown and I've opened up
2 layers of 90 turns , so 180 turns of .16mm or 6.3 mil/thou diameter wire
on 64 mm diameter former.
300 Watt ?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



My trusty 1941 Electrical Engineer's Companion has the following data
Resistivity for 0.0063 inch diameter wire 0.76 ohm per yard
Safe current carying capacity of the smallest gauge listed of 0.044 inches
diameter of 5 amps in air.
No reason to suspect this data.

This voice coil of 180 turns on 64 mm
gives 1425 inches = 40 yards
so resistance 30 ohms

Scaling by areas, current carying capacity is reduced by ratio of squares of
44 to 6.3 giving about 0.1 amp, only, in free air
I*I*R = 0.3 Watt

Where is my error ?