## What Impedance Is
Impedance is the total opposition to alternating current flow in the loudspeaker circuit — the combination of the driver's DC resistance, its inductive reactance as the voice coil moves through the magnetic field, and the reactive contribution of the crossover network. The nominal impedance figure on the spec sheet is a simplified average; the actual impedance curve rises and falls with frequency and may dip significantly at certain points.
For the power amplifier, the loudspeaker's impedance is the load it must drive. Halving the load impedance from 8 ohm to 4 ohm — at constant output voltage — doubles the current draw and doubles the power delivered to the load.
## Why Minimum Impedance Ratings Matter
Amplifiers are designed to drive loads down to a specified minimum impedance, typically 4 or 2 ohm for professional units. Driving a load below the minimum demands more current than the output transistors can supply without overheating. Most amplifiers protect against this with thermal limiting or fuse protection, but sustained operation below minimum impedance reduces amplifier lifespan and may trip protection circuits at critical moments.
## Series and Parallel Cabinet Wiring
**Parallel wiring** — the configuration used in virtually all professional audio — reduces combined impedance. Two 8-ohm cabinets wired in parallel present a 4-ohm load. Two 4-ohm cabinets in parallel present a 2-ohm load. Formula: 1/R_total = 1/R1 + 1/R2. Parallel wiring increases total power delivery from the amplifier, but that power must be within the combined continuous rating of the cabinets.
**Series wiring** adds impedances: two 8-ohm cabinets in series present 16 ohm. The amplifier's output power drops and the power is divided between cabinets. Series wiring is rarely used in professional audio.
The practical rule: always check the combined impedance of your cabinet configuration against the amplifier's minimum impedance rating before powering the system. SSOUNDS provides cabinet wiring guides for all multi-cabinet configurations, including permitted parallel combinations for each amplifier platform recommended for its systems.