Audio
Impedance
Also called: speaker impedance, ohm load
The AC resistance a loudspeaker presents to an amplifier, measured in ohms; it determines how much power the amplifier delivers and how many speakers can safely share a channel.
Amplifiers are rated into a specific load — commonly 8 or 4 ohms. Wiring speakers in parallel lowers the combined impedance, and dropping below the amplifier's minimum makes it run hot, distort, or shut down into protection. This is the arithmetic behind 'why did the amp keep cutting out' on rooms wired by whoever was cheapest.
Impedance is also a diagnostic. A load reading well below design usually means a shorted run or a speaker wired in the wrong configuration; a reading well above means a disconnected leg. Measuring impedance per zone before first power-up takes minutes and catches wiring faults before an amplifier does.
Related terms
- 70V/100V Line
- A distributed audio wiring scheme where amplifier output is stepped up to a constant voltage so dozens of speakers can share one long run, each drawing a set wattage via its transformer tap.
- Ceiling Tile Speaker
- A loudspeaker installed into a suspended ceiling grid, used in distributed arrays so coverage is even across a room instead of loud at the front and thin at the back.
More Audio terms
Support305 in the press
All press coverageNeed this specified correctly?
Our engineers will review your drawings or quote and tell you exactly where Impedance belongs in the design.
Talk to an engineer