Impedance

The voltage required to produce one amp of current. [ohm] Impedance is the reciprocal of admittance.

• At short circuit resonance, a low impedance (high admittance) is one indicator of a properly designed stack, whereas a high impedance indicates a lossy stack.
• At open circuit resonance, a high impedance (low admittance) is one indicator of a properly designed stack, whereas a low impedance indicates a lossy stack.

Also see impedance plot.