-The DC resistance is the measurement of the coil at rest. When the cone starts moving, the magnetic field associated with the magnet and the moving coil increases the resistance of the voice coil. Usually the more resonant the enclosure, the higher the impedance rise. Most competitors try to factor rise into the equation so they can get the most power out of their amps.
How can u test exactly what ohm load your amp is seeing as your playing it?
- playing a one frequency sine wave, measure AC voltage and current, using ohms law find the actual impedance.
Impedance rise only happens at resonance, so at other frequencies the amp sees something closer to the DCR (DC resistance)