Here is the thermal resistance data for three speaker coils disengaged from the speaker cone. Any ideas? I would think it would be a horizontal line.
http://en.wikipedia.org/wiki/Thermal_resistance Absolute thermal resistance of the part, K/W
edit: I also want to point out that the same trend occurred with the loudspeaker functioning as a normal speaker (before I tore out the voice coils to test separately). The reason for this test was that I thought the drop in thermal resistance was due to unwanted cooling effects (actually desirable, but not at the moment) from diaphragm movement, but the drop in thermal resistance vs temperature is still there.
edit: I am going to run the same experiment using a 1/4W resistor today and report my findings.
For x_C = 40, 60, 80:
- Heat oven to x_C
- Measure electrical resistance
- put .2W of power into resistor
- Let the resistance measurement settle (thermal time constants)
- Measure increased electrical resistance
- Calculate resulting change in temperature of resistor
- Calculate resulting thermal resistance (dT/dR)