Core materials are made for specific frequency ranges because the permeability of the core materials varies with frequency. Basically the permeability reduces the number of turns of wire you need to make the inductor (air has a permeability of 1.0). What you want in a core is high permeability and low volume resistivity. Low carbon steel has a flat B-H curve (low hysteresis) and is much more easily available than ferrite cores. A better way to make a core is to use sheets of low carbon steel with thin insulating material like varnish or paint between them.
The issue you get with a solid material is the volume resistivity issue and some energy is dissipated as eddy current losses. You can probably get decent results using a low carbon steel rod(say type 1006) of about 1" diameter as a core. My question is, is this all I need to know about choosing ferrite cores? And where can I buy ferrite cores on the internet or in what stores in general? Also Marcus wrote that "When choosing your core you should look at the data sheet and make sure that the BH-graph is linear and that it has as small as possible hysteresis." I only read two things on this forum about choosing cores: You should look for ferrite to use for inductors, look for ones with high "H" and B" values. I've heard that only some ferrite is suitable for winding inductors.
The designer of my cross-over (alvaius) recommended ferrite core anyway.
So I will make the 12 mH inductors ferrite core instead. of 12 gauge magnet wire and according to calculations I only needed 24 lbs., but I guess I didn't wind them very neatly and therefere thighly enough and I ran out of wie. I got done with one of the two 12 mH inductors I had left, when I realised that I didn't have enough wire to wind the other one (judging by the weight of wire left).
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