This may be a semi hijack of this thread... Joe jumped in on the phenomenon of reactance as it relates to the way the impedance from the speakers see the AC signal that drives the speakers to produce sound. And Fred stated, "I've always thought of impedance as the AC equivalent to resistance in a DC circuit." And I think this is generally true.
The way I understand how the AC signals coming out of our PL700Bs is that perfect resistors possess resistance, but not reactance. Perfect inductors and perfect capacitors possess reactance but no resistance. All components possess impedance when conducting AC, so, it makes sense to translate the component values of our crossovers and speakers (resistance, inductance, capacitance) into common terms of impedance as the first step in analyzing how our speakers work at different frequencies.
That aside, when we test into dummy loads, we use wire wound resistors. Is that inductance a problem at 1 KHz? Can a SPICE model be used to replicate what happens when we substitute a purely resistive 8 Ohm dummy load for the impedance of our speakers and how this affects the amplifier under test? Assuming a test signal of 1 KHz (we all use that, right?), then should we be adding capacitance and inductance in series with our resistive dummy load to better (safer) test the amplifier?
I read about a guy who used (4) 3500 Watt water heater elements with a resistance of about 16 Ohms each, in parallel he had a very high power 4 Ohm dummy load.