To bass boost a song without distortion, raise the frequencies below about 120 Hz with a low-shelf filter by 6 to 9 dB, and turn the overall volume down by roughly 3 dB less than the boost so the bigger bass peaks still fit under 0 dBFS. A limiter at the end catches what is left. On an already loud song, a +9 dB boost with no volume change clipped 18,627 frames in our test; the same boost with the volume at -6 dB clipped none.
This guide shows which frequencies a bass boost actually changes, what we measured at +6 to +24 dB, and how to do it in the browser, in Audacity and with FFmpeg.
Photo by Scott Major on Unsplash
What does a bass boost actually do?
A bass boost is a low-shelf filter: it turns up every frequency below a chosen point by a set number of decibels and leaves the rest of the song alone. The Web Audio specification describes its lowshelf filter as one that "allows all frequencies through, but adds a boost (or attenuation) to the lower frequencies". FFmpeg's bass filter calls the same idea shelving equalisation, "similar to that of a standard hi-fi's tone-controls".
The shelf does not switch on at an exact frequency. It slopes in gradually, so a "120 Hz" shelf still nudges 200 Hz a little and gives its full boost only well below the corner.
Which frequencies should you boost for more bass?
Boost the range below about 100 to 120 Hz. That covers the kick drum and the bass line, and it is where most "bass boosted" edits put their energy. Audio interface maker Audient's frequency guide splits the low end into two bands:
| Band | Range | What lives there |
|---|---|---|
| Sub-bass | 20 to 60 Hz | Felt as much as heard: synth subs, 808s, the lowest bass notes |
| Bass | 60 to 250 Hz | The weight and solidity of the bass instrument and the kick |
| Low mids | 250 to 500 Hz | Vocal fundamentals and many instruments; too much sounds boxy |
The same guide notes that sub-bass needs "a very big pair of monitors, or a dedicated subwoofer" to really come through. That is why a shelf that stops around 120 Hz is a sensible default: it lifts the punch you can hear on headphones and normal speakers without pushing the crowded low mids.
We read the exact curve of the shelf that the SearchSound.cloud bass booster uses (a Web Audio lowshelf at 120 Hz) with getFrequencyResponse in Chromium. Each cell is the boost in dB that a frequency receives:
| Slider | 30 Hz | 60 Hz | 80 Hz | 100 Hz | 120 Hz | 150 Hz | 200 Hz | 250 Hz | 500 Hz | 1 kHz |
|---|---|---|---|---|---|---|---|---|---|---|
| +6 dB | 6.0 | 5.6 | 5.0 | 4.0 | 3.0 | 1.8 | 0.7 | 0.3 | 0.0 | 0.0 |
| +9 dB | 9.0 | 8.4 | 7.4 | 6.0 | 4.5 | 2.7 | 1.2 | 0.5 | 0.0 | 0.0 |
| +12 dB | 11.9 | 11.1 | 9.7 | 7.8 | 6.0 | 3.8 | 1.7 | 0.8 | 0.1 | 0.0 |
| +18 dB | 17.9 | 16.3 | 14.0 | 11.4 | 9.0 | 6.1 | 3.0 | 1.5 | 0.1 | 0.0 |
| +24 dB | 23.7 | 21.0 | 17.9 | 14.8 | 12.0 | 8.6 | 4.8 | 2.6 | 0.2 | 0.0 |
Two things stand out. The named frequency gets exactly half the boost (+9 dB on the slider means +4.5 dB at 120 Hz), and the full amount only arrives below about 40 Hz. So the slider number describes the deepest sub-bass, while the kick at 60 to 100 Hz gets a bit less. Other tools place the shelf differently: the Audacity Bass and Treble effect has its half-gain point at 250 Hz, and FFmpeg's bass filter defaults to 100 Hz, so the same "+9 dB" sounds different in each.
Why does bass boosting cause distortion?
Bass boosting causes distortion because bass carries most of a song's energy, so lifting it makes the waveform's peaks taller, and in a song that is already mastered loud those peaks have almost nowhere to go. Digital audio has a hard ceiling at 0 dBFS, and any sample pushed above it is cut flat. That flattening is clipping, and on bass it sounds like crackle or fuzz.
A limiter avoids most of it by turning the whole signal down for a moment whenever a peak would cross the ceiling. The catch is that it turns down everything, not only the bass. When the bass hits constantly, the limiter works constantly, and the vocals and hi-hats get quieter in time with the kick. That is the "pumping" sound of an overdone bass boost.
How much bass boost is too much?
On a typical loud master, +6 to +9 dB is the useful range; past +12 dB the extra bass mostly turns into clipping and limiter pumping. We measured this on a real track to put numbers on it.
We took 60 seconds of "by the across" by Thomas Park (Public Domain Mark), decoded to 44.1 kHz stereo (2,646,000 frames). It is mastered loud: -15.5 LUFS with a peak of -1.6 dBFS, so it has less than 2 dB of headroom. We rendered it in Chromium through the same chain the SearchSound.cloud bass booster runs: the 120 Hz low shelf, a volume stage, and a DynamicsCompressorNode set as a limiter (threshold -1 dB, ratio 20:1, 3 ms attack, 250 ms release). For comparison we also rendered the boost with no limiter. We counted frames that hit the 16-bit ceiling, measured loudness with FFmpeg's EBU R 128 meter, and measured the level below 100 Hz and above 1 kHz to see what the bass and the treble each did.
| Bass boost | Clipped frames, with limiter | Clipped frames, no limiter | Bass below 100 Hz | Treble above 1 kHz | Loudness |
|---|---|---|---|---|---|
| 0 dB | 0 | 0 | 0 dB | 0 dB | -15.0 LUFS |
| +6 dB | 73 (0.003%) | 3,034 (0.11%) | +4.7 dB | 0.0 dB | -12.6 LUFS |
| +9 dB | 789 (0.03%) | 18,627 (0.70%) | +6.7 dB | -0.1 dB | -11.5 LUFS |
| +12 dB | 2,264 (0.09%) | 52,489 (1.98%) | +8.5 dB | -0.2 dB | -10.3 LUFS |
| +18 dB | 13,397 (0.51%) | 243,584 (9.2%) | +11.1 dB | -1.1 dB | -8.6 LUFS |
| +24 dB | 48,651 (1.8%) | 643,189 (24.3%) | +12.7 dB | -2.6 dB | -7.5 LUFS |
What the numbers show:
- The limiter removes most of the clipping. At +9 dB it cut clipped frames by 96% compared with a plain boost. It is not a brick wall, though: its 3 ms attack lets the first instant of each big kick through.
- Returns shrink fast. Going from +12 to +24 dB on the slider added only 4.2 dB more bass, because the limiter pulled the whole mix down to make room.
- Past +12 dB the rest of the song pays. At +24 dB the treble dropped by 2.6 dB on average. That is the pumping you hear: the limiter ducking the vocals every time the bass hits.
The 0 dB row is 0.5 dB louder than the original because the Web Audio specification gives the compressor a fixed makeup gain, about +0.57 dB at these settings. The same effect is explained in our guide on how to make an MP3 louder without distortion.
The limit depends on the song. On a second, lighter track from the same album (-17.8 LUFS, peak -2.4 dBFS), +9 dB with no volume change clipped zero frames even without a limiter. Bass-heavy, loudly mastered songs such as hip hop and EDM have the least room.
How do you bass boost without clipping?
Turn the volume down before or while you boost. Lowering the overall level makes room for the taller bass peaks, so the limiter has little or nothing to do and the treble is not pumped. The Audacity manual gives the same advice: a bass boost can push the level "so high that it distorts", so "to avoid clipping, reduce the level by setting the Volume control lower".
Here is what pre-cutting did on the loud test track:
| Settings | Clipped frames | True peak | Bass vs treble, compared with the original |
|---|---|---|---|
| +9 dB bass, 0 dB volume | 789 | +0.1 dBTP | +6.8 dB |
| +9 dB bass, -6 dB volume | 0 | -0.9 dBTP | +7.4 dB |
| +12 dB bass, -9 dB volume | 0 | -1.8 dBTP | +9.9 dB |
| +12 dB bass, -12 dB volume | 0 | -4.8 dBTP | +9.9 dB |
The pre-cut versions ended up with more bass relative to the rest of the song than the full-volume version, because the limiter was no longer squashing the mix. The trade-off is that the file is quieter overall, so you turn up your playback volume instead. A workable rule from these runs: set the volume about 3 dB lower than the bass boost (+9 dB bass with -6 dB volume, +12 dB bass with -9 dB volume), then check the loudest part of the song.
How do you bass boost a song online for free?
On SearchSound.cloud you can bass boost a song with the free bass booster, which runs in your browser, so the file is never uploaded. The steps:
- Open the bass booster and drop in your file. MP3, WAV, FLAC, M4A, AAC, OGG and Opus files work.
- Start from the preset. It begins at +9 dB of bass with the volume at 0 dB and the limiter always on.
- Play the loudest part of the song (usually the drop or final chorus) and adjust the bass slider, which goes from 0 to +24 dB.
- Lower the volume slider by about 3 dB less than your bass boost if the kick starts to crackle or the vocals duck.
- Download as MP3, WAV or FLAC. Choose WAV or FLAC if you plan to edit the file again, since each MP3 encode loses a little more detail (our test of whether converting MP3 to WAV improves quality explains why).
The same preview also has more effects, so you can combine a bass boost with a speed change. The nightcore maker, for example, starts with a +3 dB bass boost to bring back weight that speeding up takes away. If the whole song is too quiet rather than thin in the low end, the volume booster is the better tool.
How do you bass boost in Audacity or FFmpeg?
Audacity: select the track, open Effect, then EQ and Filters, then Bass and Treble. Raise Bass (the range is ±30 dB, per the manual) and either lower Volume yourself or tick "Link Volume control to Tone controls", which adjusts the volume automatically. Its shelf reaches higher (half-gain at 250 Hz), so expect a fuller, warmer boost than a 120 Hz shelf gives, and listen for a boxy sound.
FFmpeg: chain a volume cut, the bass filter and a limiter:
ffmpeg -i in.mp3 -af "volume=-6dB,bass=g=9:f=120,alimiter=limit=0.89:level=disabled" out.wav
g is the boost in dB and f the shelf frequency; the FFmpeg documentation warns "Beware of clipping when using a positive gain". A limit of 0.89 is about -1 dBFS. On our test track this command produced -17.4 LUFS with a true peak of -1.5 dBTP, so nothing clipped.
Why can't I hear the bass boost on my phone?
Small speakers cannot move enough air to reproduce deep bass, so a boost aimed at 30 to 60 Hz mostly disappears on a phone or laptop. Audient's guide makes the same point: sub-bass needs big monitors or a subwoofer, with decent headphones as the next best thing. As our table shows, that is where the shelf applies its full boost. What a phone can play is the upper part of the shelf, which gets only a fraction of the slider value (half of it at 120 Hz, about a seventh at 200 Hz). Check a bass boost on headphones or proper speakers. If it has to work on phones, a lower boost with the volume pre-cut is a safer choice than a huge one that rattles the speaker.
It also helps to know that ears are far less sensitive to low frequencies at low volume, as equal-loudness contours show. A bass boost that sounds right quietly can be overwhelming when played loud, and turning everything up to hear more bass is how listening gets unsafe: the WHO estimates that over 1 billion young adults are at risk of permanent, avoidable hearing loss from unsafe listening practices.
Where can you find songs that already have a bass boost?
If you want ready-made bass boosted tracks instead of making your own, search SoundCloud on SearchSound.cloud for "bass boosted" and filter by BPM, duration and date. Bass boosted uploads of other artists' songs are still their recordings, so treat them as personal listening rather than music you can reuse in your own videos. For music you can publish, see our guide to royalty-free music for YouTube.
FAQ
What is the best bass boost setting?
For most songs, +6 to +9 dB on a shelf around 100 to 120 Hz, with the overall volume lowered by about 3 dB less than the boost. In our test that combination added 7 dB of bass relative to the rest of the song with zero clipped frames. Go higher only on quiet or bass-light tracks.
Does bass boost reduce audio quality?
The filter itself does not, but clipping and heavy limiting do. A +18 dB boost on a loud master clipped 9.2% of the frames without a limiter and still 0.5% with one. Keep the boost moderate, pre-cut the volume, and save as WAV or FLAC if you will process the file again.
What Hz is bass?
Bass is roughly 60 to 250 Hz and sub-bass 20 to 60 Hz. The bass instrument and the kick drum carry their weight in the bass band, while 808s and synth subs reach into the sub-bass. Boosting much above 250 Hz works on the low mids instead, which tends to sound boxy rather than bassier.
Is bass boost bad for headphones or speakers?
Moderate boosts are fine. Very large ones push small drivers to their limits, which causes rattling or audible distortion in the speaker even when the file itself is clean. If you hear buzzing on one device but not on another, the speaker is the limit, not the file.
Can I bass boost a song and post it on YouTube?
You can upload it, but a bass boosted version of someone else's song is still their recording, and copyright claims apply to it as they do to the original. The safe options are boosting music you own, or royalty-free music whose license allows changes.