How to Test a Subwoofer

Run the bass sweep

The subwoofer sweep plays one smooth tone that glides from 20 Hz up to 200 Hz over ten seconds — the bass range a consumer subwoofer typically covers. It starts at the deepest rumble and climbs into the upper bass, so every part of the low end gets its turn.

Listen for an even, unbroken rise. A healthy setup keeps the loudness fairly steady across the whole range; warning signs are sudden dropouts where the tone disappears, single notes that boom far louder than their neighbors, and buzzing that rides on top of the tone.

Where the crossover fits in

A crossover splits the work between your speakers: the subwoofer plays the frequencies below the crossover point, and the main speakers play everything above it. On AV receivers this point is typically adjustable between 40 and 80 Hz, and less expensive receivers often fix it at 80 Hz.

That makes 80 Hz a common default: THX-certified systems keep the subwoofer below 80 Hz, and professional live-sound systems run their subwoofers below 100 Hz. As the sweep passes through your crossover region, listen to the handoff — the tone should travel from the subwoofer to the main speakers without a dip or a bump in loudness along the way.

Rattles, placement, and the room

Run the sweep at a moderate volume and walk around while it plays. Loose objects reveal themselves by buzzing at very specific frequencies — picture frames, shelves, air vents, and lampshades are classic offenders.

The room shapes what you hear as much as the subwoofer does. In small rooms it is normal for some frequencies to sound louder than others, and the low end changes noticeably when you move the subwoofer — or yourself. If one spot booms, repeat the sweep from another position and compare.

Check the polarity — at a sensible volume

When one speaker of a pair is wired with plus and minus swapped, its cone pulls back while the other pushes out, and the bass partly cancels: the sound turns thin and hard to place. The polarity test plays the same sound through both speakers and lets you flip one side — if the flipped setting sounds fuller, one cable is reversed.

Whatever you test, start at a low volume and raise it gradually. Sweep tones and deep bass are louder than they feel and can strain both speakers and ears at high levels.

Related guide: How to test your speakers — the full walkthrough

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