There are three main types of headphones: Dynamic, Balanced Armature and Electrostatic headphones. Although there are several equivalent magnetic formulas in addition to these three types, they are either eliminated or used for professional purposes. The market share in Hi-Fi field is very small.

Notice the difference between resistance and resistance. In the world of direct current (DC), the effect of object on current obstruction is called resistance, but in the field of alternating current (AC), besides resistance, capacitance and inductance can also obstruct current flow. This effect is called resistance, which we call impedance everyday. It is the sum of resistance and reactance on the vector.