Impedance (Ω)
Definition
The total opposition a circuit presents to alternating current, measured in ohms (Ω). In audio, impedance matching between devices — microphones, headphones, amplifiers, and speakers — determines signal transfer efficiency, frequency response, and potential for noise or distortion. For microphones, impedance is the output impedance of the source (the mic itself); for recording devices, it's the input impedance that determines how much voltage the device expects and how well it couples with the microphone.
In Simple Terms
Electrical resistance that affects how audio devices work together. Low-impedance headphones (32 ohms) are easy to drive from a phone. High-impedance headphones (250+ ohms) need a dedicated amplifier. With microphones, a 48-ohm dynamic mic plugged into a 10k-ohm input (common in professional interfaces) works great. Plugged into a 1k-ohm input (common in cheap portables), the mic sounds quiet and thin.
In Practice
A dynamic microphone (48–600 ohms output) connected to a professional audio interface (10k+ ohm input) produces a strong, clear signal. The same microphone into a basic portable recorder (often 2k ohms or less) sounds weak and dull because the input impedance is too low — the recorder is essentially loading down the microphone's output, causing a voltage divider that kills gain and changes the frequency response.
Common Confusion
"My mic doesn't work with my portable recorder" usually means impedance mismatch, not a broken mic. Field recorders designed for instrument recording (like acoustic guitar) have low input impedance to handle dynamic microphones. Those same recorders are terrible for condenser mics because condensers have higher output impedance and need the higher input impedance of a professional interface to deliver their full voltage. Professional audio interfaces (Zoom Liaise, Scarlett, etc.) are designed with 10k–60k ohm inputs specifically to accept a wide range of microphone impedances without coloring the signal.
Sources & Verification
- AES48-2005 — AES standard on interconnections — Grounding and EMC practicesAudio Engineering Society
- Self, D. — Small Signal Audio Design (3rd ed., impedance and mic coupling chapter)Focal Press, 2020
- AES Pro Audio Reference — Microphone input impedance and matchingAudio Engineering Society
Last verified: 2026-08-05