How to match an amp to your subwoofer (RMS, impedance, verified watts)

1. Start with your sub's RMS rating

RMS is the continuous power the sub is built to handle. Ignore "max" or "peak" figures. Add up the RMS of all the subs the amp will drive.

2. Work out the final impedance

How you wire the voice coils and the subs sets the load the amp sees (for example 1Ω, 2Ω or 4Ω). An amp's output changes a lot with load, so its power has to be judged at your load. The impedance calculator works it out for you.

3. Compare against measured watts, not the box

Box ratings are often inflated, and the load they're quoted at isn't always stated (see rated vs actual). Use dyno-measured output at your final impedance instead.

4. Leave some headroom

A common rule of thumb is an amp that delivers roughly 75–150% of your total sub RMS at the final load, with the gain set properly. Too little power tempts you to turn the gain up into clipping; far too much risks damaging the sub if the gain isn't set carefully.

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