Subwoofer Test — Tones & Sweep

A subwoofer test checks whether your system reproduces the bottom two octaves. Sine tones at 20, 30, 40, 50, 60, 80, and 100 Hz find the extension limit, a 20–200 Hz sweep runs 16 seconds, and 55 Hz kick hits repeat at 96 BPM. Everything runs in your browser, and nothing is uploaded.

How to use it

1. Use a system that can move air. Phone and laptop speakers roll off below about 100 to 200 Hz, so a 20 Hz preset may be silent or produce only a faint rattle. Use a subwoofer or full-range speakers.
2. Start quiet on a familiar preset. Press 80 Hz, then press Play preset tone. Each preset is a continuous sine with a 30 ms attack and a 50 ms release, so there is no click.
3. Step down through the presets. Hold 60, 50, 40, 30, and 20 Hz for 5 to 10 seconds each. Note the lowest frequency that stays clean, and stop if you hear chuffing, buzzing, or a tone that jumps in level.
4. Run the sweep. Press Play sweep for a logarithmic pass from 20 to 200 Hz over 16 seconds, about 4.8 seconds per octave, with the current frequency shown every 100 ms. Walk the room while it plays.
5. Start the kick pulse. Press Start kick pulse for a 55 Hz sine hit every 625 ms at 96 BPM, with a 5 ms attack and a 180 ms release inside each 280 ms hit.
6. Stop before you change anything. Press Stop, adjust placement or the subwoofer’s crossover, then repeat the 80 Hz and 100 Hz presets to hear whether the handover improved.

What each test tells you

The three signals answer different questions: the presets find the limit, the sweep finds the room, and the kick finds the overhang.

Preset tones

Each preset is a continuous sine at the labelled frequency, played at 0.25 gain with a click-free envelope. The lowest preset with clean output is your usable extension limit. A tone that gets louder as you step down usually means a room mode, not more sub output. A tone that turns into a buzz or a windy noise between 30 and 50 Hz is port chuffing or a loose panel.

Slow sweep

The sweep is logarithmic, so each octave gets equal time: about 4.8 seconds across the 16 second pass from 20 to 200 Hz. The live readout lets you note where output blooms or disappears. A peak that follows you around the room is a mode; a null that stays fixed points at the listening position, the crossover, or the sub’s phase setting.

Kick pulse

The kick repeats a 55 Hz sine with a 5 ms attack and a 180 ms release at 96 BPM, one hit every 625 ms. Each hit lasts 280 ms, leaving 345 ms of silence between hits. Tight, even hits suggest good amplifier control; overhang or rattling objects mean the room rings longer than the source.

Wavelengths, room gain and crossover

At 20 °C sound travels at about 343 m/s, so wavelength follows λ = 343 / f: a 20 Hz tone measures 17.2 m, longer than most rooms. Rectangular rooms reinforce frequencies whose half-wavelengths fit their dimensions, so axial modes land at f = n × 343 / (2L). A 4.0 m dimension puts its first mode at 42.9 Hz, 3.5 m at 49.0 Hz, and 2.5 m at 68.6 Hz. Below the lowest mode the room behaves like a pressure vessel rather than a resonating box, so output can rise by several dB per octave instead of rolling off.

A crossover near 80 Hz is common because direction cues weaken below roughly 150 Hz, so the sub’s position is hard to hear once the handover is smooth; receivers usually low-pass the LFE channel near 120 Hz.

Port chuffing is turbulence, not distortion: air speed in a bass-reflex port rises near the tuning frequency, and the airflow turns noisy. It sounds like a puffing texture rather than a buzz, appears near 30 to 50 Hz, and usually disappears when you drop the level.

Frequency	Wavelength at 343 m/s	Period	Musical or system anchor
20 Hz	17.2 m	50.0 ms	Bottom of the audible band; felt more than heard
30 Hz	11.4 m	33.3 ms	Low B0 of a 5-string bass (30.9 Hz)
40 Hz	8.6 m	25.0 ms	Low E1 of a bass guitar (41.2 Hz)
55 Hz	6.2 m	18.2 ms	The kick pulse’s fundamental
80 Hz	4.3 m	12.5 ms	Common sub/satellite crossover

Accuracy, limits and troubleshooting

• Levels are dBFS, not dB SPL. The readout is digital level relative to full scale, and the page has no microphone, so it cannot report room SPL.
• Equal-loudness changes what you hear. At 30 to 40 Hz a tone needs far more SPL to sound as loud as 1 kHz; ISO 226:2023 specifies the equal-loudness contours that describe this. Do not judge a low preset by loudness alone.
• Small speakers have hard limits. Cone area and cabinet volume set how much air a driver can move. If a laptop shows nothing below 100 Hz, the test worked.
• Separate hearing limits from hardware limits. If a 30 Hz tone is inaudible on headphones that should reproduce it, try the low frequency hearing test first.
• Distortion can impersonate bass. A small driver that cannot complete a 30 Hz cycle may produce audible harmonic distortion at 60 and 90 Hz. The giveaway is a definite, octave-too-high pitch while the cone moves in large, slow excursions.
• Room correction and loudness modes rewrite the result. Receiver EQ, night mode, dynamic loudness, and phone “bass boost” all reshape low output. Disable them before testing.
• Keep levels modest and sessions short. High-level sub-bass heats voice coils and works the suspension hard, and 20 Hz is loud in the room even when it seems quiet at your ears. Never raise the volume to hear a 20 Hz tone.

Related tools

• Bass Test — Discrete 30 to 200 Hz tones and a 30 to 250 Hz sweep for a second look at the low end.
• Subwoofer Calibration 10–200 Hz — A step-by-step calibration walk-through with placement and level guidance.
• Low Frequency Hearing Test — Check what your ears can hear before blaming the speaker.

Aliases covered on this page: subwoofer test, bass test, sub bass test, low frequency test, 20hz test tone, and subwoofer kick test.