Air coils (i.e. coils without a ferro-magnetic core) are absolutely distortion-free, which on the face of it makes them ideal for all audio applications. The trouble is, their electrical resistance increases with their inductance. There are two solutions to this problem: One can either use very thick windings (this is why our standard range includes windings with wire up to 3 mm in diameter) or coils with cores. Lower cost and smaller size are also
L denotes inductance, R the DC resistance, D the diameter, Le the length, Wire-W the width of the wire, DxH the diameter and the height.