Speaker Frequency Sweep & Resonance Tester

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 as the difference between 10,000 Hz and 20,000 Hz, because both represent a doubling of frequency.¹ 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 the slider midpoint (500) lands at roughly 632 Hz rather than the 5000 Hz a linear scale would place there.¹ Bass and sub-bass frequencies occupy the lower third of slider travel, giving you the resolution you need where it matters most, and you can isolate a troublesome frequency by slowing your drag.

Choosing a waveform

The four waveforms differ in harmonic content, and picking the right one determines what the test reveals about your speaker or the room you are in. Sine is a pure fundamental with no harmonics, which makes it the cleanest signal available for isolating a single resonance frequency without other harmonics exciting adjacent resonances or masking the one you are trying to pin down.² Start here for most testing, and switch to a richer waveform only when the sine sweep leaves a question unanswered.

Square adds strong odd harmonics (3rd, 5th, 7th…), making it useful for crossover testing and stressing drivers with complex content.² Triangle has odd harmonics that fall off faster, so it serves as a middle ground for tweeter distortion checks that need less bite. Sawtooth contains all harmonics at full strength and is the harshest signal here, which suits amplifier headroom testing but grows fatiguing at high volume.³

Finding room resonances and rattle points

Room resonances (modes) are standing waves that build up at frequencies determined by room dimensions.⁴ 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 originate from loose panels, improperly fitted grilles, and furniture that vibrates in sympathy with the tone, so they are easier to locate using Manual mode. Sweep slowly through suspect ranges and pause the moment you hear a rattle, then check the frequency display for the exact Hz. Walk around the room while the tone plays, and the source will become obvious once you are close to it, letting you identify the offending panel or furniture piece quickly.

What does a healthy system sound like across the whole range? Even, mostly. As a sweep travels from 20 Hz to 20 kHz, a well-behaved speaker and room keep the same loudness all the way up: no single frequency blooming louder than its neighbors, no abrupt hole where a band drops out, no mechanical buzz joining in anywhere along the climb. Judge the whole journey, not one reading, because every room boosts some bass and muffles some treble, and small peaks and dips are normal room behavior rather than faults. The frequency reference guide walks every landmark from sub-bass to tweeter breakup with what each one should sound like, including the 16 kHz checkpoint near the top of the range.

Subwoofer drop-off and roll-off testing

Two related tests share the Subwoofer preset, and both reveal whether your bass setup covers the range you expect. One finds how low your subwoofer holds output before roll-off swallows the bass; the other locates the crossover where your main speakers take over from the subwoofer. Running them back to back tells you whether a gap or a peak exists between the two.

Finding the subwoofer roll-off

Most home subwoofers have a low-frequency extension limit, typically somewhere between 20 and 30 Hz, below which the output drops sharply instead of holding steady.⁵ To find yours on this tool, set the Subwoofer preset, which spans 20 to 200 Hz, pick the sine waveform, and then sweep downward manually from 80 Hz. The point at which the subwoofer becomes noticeably quieter, or stops producing any audible output at all, is its roll-off frequency.

Locating the upper crossover point

Similarly, sweep upward from 80 Hz to locate the upper crossover point where your main speakers take over from the subwoofer. As you move through that transition region, listen carefully for any dip in output or any unexpected peak. A smooth, overlap-free handoff between the subwoofer and the main speakers produces a flat in-room response, while a gap or a pronounced peak at the crossover frequency points to a crossover setting mismatch that you can correct in your receiver or amplifier.

For accuracy checks, prefer a wire over a Bluetooth link. The common Bluetooth audio profile re-encodes everything it carries: its spec makes the SBC subband codec mandatory for interoperability and recommends running it at a few hundred kilobits per second, so the tone leaving your computer is not the tone arriving at the speaker.⁶ A re-encoding stage is the variable a diagnostic wants gone, because a codec squeezing the stream down to fit the radio link can smooth over the loudness differences a sweep exists to expose. With nothing in between deciding what survives, a cable carries the oscillator's output straight to the amplifier. Keep Bluetooth for convenience. Keep the wire for the verdict.

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.⁷ 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. Knowing this figure helps you decide where to set a subwoofer low-pass filter and whether a given driver can handle the bass content you plan to test.

How enclosures shift the resonant frequency

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.⁷ 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.

Checking your own hearing range

The sweep gives you a direct way to listen at your own hearing rather than at a spec sheet. By running tones up and down through the range your ears can still track, you build a personal picture of where you respond and where the response starts to fall away. That is a different question from how loud a speaker can play or how low it can reach, and it says something about the listener rather than about the hardware.

Finding your hearing ceiling

Run the check in a quiet room with the volume set moderate, because you are hunting a disappearance, not a thrill. With the sine waveform selected, start the tone somewhere comfortable around 1 kHz, then either drag the slider upward slowly or switch to Auto Sweep across the Treble preset at its slow speed. Watch the frequency display and note the reading where the tone fades to something you can no longer call sound. That reading is your hearing ceiling for today, and it belongs to you rather than to the speakers: a ceiling measured through unknown hardware is really a statement about the hardware, which is why headphones you trust or a speaker you know cold produce the honest number.

Age is the biggest variable between two people running this check. The NIDCD counts roughly one in three American adults between 65 and 74 as having hearing loss, and nearly half of those past 75; the loss arrives gradually, through changes in the inner ear and along the nerve pathways from the ear to the brain, with years of noise exposure layered on top.⁸ Because none of it appears on a spec sheet, a ceiling comparison between two people describes their ears, not their equipment. Treat it as a curiosity rather than a contest: the reading belongs to the listener, the tonal character belongs to the hardware, and an older ear topping out early on the same sweep is the statistic doing exactly what statistics do.

Treat the result as a rough map, not a diagnosis. Ambient room noise quietly lowers the ceiling you measure, because traffic, an air conditioner, or a humming fridge buries the faint last trace of the tone that would otherwise still be audible; a quiet room is the only fair bench. This is also not an audiogram: a clinic measures hearing across controlled levels and specific frequencies, and nothing on a browser sweep replaces that. If the tone disappears far below where you expected it, or one ear clearly outruns the other, that is a reason to book a hearing check, not a reason to keep sweeping. The sweep tells you where to be curious; a professional tells you what it means.

Pinning a single tone

A sweep is only half of what the generator does. Switch to Manual mode, pick a frequency, press Play Tone, and the oscillator holds that single pitch for as long as you leave it running, which turns the tool into a plain tone generator whenever you need one. People reach for a held tone more often than you might guess: isolating the one frequency that makes a grille buzz, tuning an instrument or a filter by ear against a reference pitch, or feeding one driver a steady signal while you listen for coil rub or distortion at a known frequency. The slider keeps working while the tone plays, so you can scrub around a suspect region without stopping anything.

Held tones deserve more respect than passing sweeps, so keep the volume moderate and the sessions short. Unlike a sweep, which spreads its energy across the whole band as it travels, a parked tone keeps delivering the same power to the same driver and the same narrow region of your hearing for every second it runs, which is exactly the pattern that turns tiring into damaging if you let the level creep up. The volume slider exists for this: start low, raise it only until the tone is comfortably clear, and stop the tone the moment your check is done rather than letting it drone on in a background tab.