6.3: Impedance

Impedance

Impedance is the effective resistance of an electrical circuit to alternating current (AC), measured in ohms (Ω). In microphones, impedance refers to how much the mic resists the flow of electrical signal.

• Low Impedance (Low-Z): Typically 150–600 Ω. These microphones are preferred for professional use because they allow long cable runs with minimal signal degradation and reduced noise. In essence the signal is difficult to “impede”.
• High Impedance (Hi-Z): Typically greater than 10k Ω. Found in many consumer and older microphones. Hi-Z mics are more susceptible to noise, signal loss, and reduced clarity, especially over long cables. These mics are easy to “impede”.

Importance of Impedance Matching

Impedance matching is critical for achieving the best signal transfer between a microphone and the device it’s connected to (such as a preamp, mixer, or recording device). If the microphone’s output impedance is too high compared to the input impedance of the device, signal loss, reduced frequency response, and added noise can occur. Professional audio gear is designed so that the input impedance is much higher (often 10x or more) than the microphone’s output impedance. This ensures maximum voltage transfer, minimal distortion, and cleaner audio capture.