Match the amplifier’s RMS output at the subwoofer’s final impedance to the sub’s RMS rating, staying within roughly 75–150% of that figure.
For the full breakdown, see our best Amplifier And Subwoofer guide.
Two numbers settle the pairing, and neither one is the peak wattage plastered across an amplifier box. A subwoofer’s continuous power rating and the impedance its wiring creates decide which amps can feed it properly — and which ones cook a voice coil in an afternoon.
Matching an amp to a subwoofer hinges on the sub’s own continuous numbers. The arithmetic runs outward from the driver: RMS power handling, then the final load its wiring creates, then the amplifier’s rated RMS output at that same load. Published guides put the comfortable window at about 75% to 150% of the sub’s RMS figure, with some tightening it to 80% to 120%.
Start With The Subwoofer’s RMS Rating
RMS is the power a subwoofer handles steadily, and it’s the only number worth sizing an amplifier against. Peak and max ratings describe brief bursts that say nothing about what a driver survives on a two-hour drive.
The manual or the manufacturer’s product page lists RMS power handling along with the coil setup — single voice coil (SVC) or dual voice coil (DVC) — and the impedance of each coil in ohms. American Bass’s guide to reading a subwoofer spec sheet treats RMS, impedance, and Xmax as the specs that matter most, since they drive both amplifier choice and box design.
Write these down before shopping:
- RMS power handling in watts, taken from the manual rather than a retailer’s inflated listing.
- Coil configuration and impedance, so the final load gets calculated instead of guessed.
- Subwoofer count, because every extra driver adds to the total the amplifier has to feed.
How Much Amp Power Does A Subwoofer Need?
A subwoofer needs an amplifier whose RMS output at the final load lands between roughly 75% and 150% of the sub’s RMS rating. A 300-watt sub, for instance, pairs well with anything from about 225 to 450 watts of continuous RMS power at the impedance you