Why the frequency slider is logarithmic
Human hearing perceives pitch logarithmically, not linearly. The difference between 20 Hz and 40 Hz sounds like the same musical interval — one octave — as the difference between 10,000 Hz and 20,000 Hz. A linear slider would pack the entire bass range (20–500 Hz) into the leftmost 2% of travel, making precise subwoofer testing nearly impossible.
This tool maps a 0–1000 internal range logarithmically to 20–20,000 Hz, so slider midpoint (500) lands at roughly 632 Hz. Bass and sub-bass frequencies occupy the lower third of slider travel, giving you the resolution you need where it matters most.
Choosing a waveform
The four waveforms differ in harmonic content. Sine is a pure fundamental with no harmonics — the cleanest signal for isolating a resonance frequency without harmonics exciting additional resonances. Start here for most testing.
Square adds strong odd harmonics (3rd, 5th, 7th…), making it useful for crossover testing and stressing drivers with complex content. Triangle has odd harmonics that fall off faster — a middle ground for tweeter distortion checks. Sawtooth contains all harmonics at full strength and is the harshest signal here — useful for amplifier headroom testing but fatiguing at high volume.
TIP When using Square or Sawtooth at high frequencies, the harmonic content extends well above the fundamental — a 5 kHz square wave produces harmonics at 15 kHz, 25 kHz, etc. Keep volume low when using these waveforms above 2 kHz.
Finding room resonances and rattle points
Room resonances (modes) are standing waves that build up at frequencies determined by room dimensions. They cause certain bass notes to sound disproportionately loud or muddy. To find them: run the Auto Sweep at slow speed (10 Hz/s) through the Subwoofer preset, and listen for frequencies where the sound seems to bloom or become uncomfortably loud despite no volume change.
Rattle points — loose panels, improperly fitted grilles, furniture vibrating in sympathy — are easier to locate using Manual mode. Sweep slowly through suspect ranges and pause when you hear a rattle. The frequency display shows the exact Hz. Note the frequency, then walk around the room while the tone plays to locate the source by proximity.
Subwoofer drop-off and roll-off testing
Most home subwoofers have a low-frequency extension limit — typically 20–30 Hz — below which output drops sharply. To find yours: set the Subwoofer preset (20–200 Hz), use Sine waveform, and manually sweep downward from 80 Hz. The point at which the subwoofer becomes significantly quieter or stops producing audible output is its roll-off frequency.
Similarly, sweep upward from 80 Hz to find the upper crossover point where your main speakers take over. A smooth, overlap-free handoff between subwoofer and mains produces a flat in-room response; a gap or peak at the crossover frequency indicates a crossover setting mismatch.
NOTE This tool outputs directly to your default system audio output. If your subwoofer is on a separate output (e.g., an AV receiver) rather than the default output, select it as your system default before using the Subwoofer preset.
Understanding your driver's resonant frequency
Every driver has a resonant frequency (Fs), the point where it moves most freely with the least electrical energy input. Below that frequency, the driver's mechanical compliance acts as a spring resisting further excursion, and output drops steeply. Above Fs in a well-designed enclosure, output stays relatively flat until the high-frequency roll-off from moving mass takes over. Manufacturers specify Fs in the driver datasheet, and understanding it tells you the lowest useful frequency before bass response falls away sharply.
Finding your driver's practical resonance with the sweep takes under two minutes. Sweep slowly downward from 100 Hz with the sine waveform selected and listen for the frequency where the driver sounds most prominent just before output drops sharply. Sealed enclosures shift Fs upward compared to the free-air specification; ported enclosures are tuned below Fs to extend low-frequency output, which is why ported designs reach lower but roll off more steeply below the port tuning frequency. Building on this knowledge, you can set crossover and EQ filter points at frequencies that respect your driver's actual behaviour rather than guessing from marketing copy.
