In response to the audible difference between air core and steel laminate inductors, I have replaced a 16 gauge 3.9 mh steel laminate 0.20 dcr inductor with a 9 gauge Intertechnik air core inductor of identical 3.9 mh and 0.20 ohm dcr on the low pass over of a 12" woofer. The sonic difference is quite substantial even at 1/4 watt listening level, there is a lot more going on happening than dcr or hysteresis to pass a musical signal from point a to point b. The air core sounds more natural on voices, (300 Hz cutoff ) with meatier bass impacts faster, richer and cleaner sound all round. I reckon that the curent capability of a coil is important. The smaller gauge conductor in the steel inductor is a current choke even with a low dcr. Im configuration, with the 3 ohm impedance at around 225 hz of my speakers , the steel inductor with a 240 watt power rating in 8 ohm gives a current rating of only 5.48 amps which translate into 90 watts for a 3 ohm load. The air core with a 1180 watt power rating into 8 ohm gives a current rating of over 12 amps or 440 watts into 3 ohm. Sure there is more length of wire in the air core, but when the gauge is thick enough to equate the dcr of the steel inductor, the ability for the air core to pass current and the musical signal is in a different league. Music flows in that air core whereas it feels restricted, squeezed and compressed in the steel core even at very low listening levels. My conclusion is very similar to what North creek audio found out years ago.