2. Low end and loudness: the bass decides how loud the song gets
Why low frequencies limit your master's loudness, how LUFS and true peak relate to the bass, and how much headroom to deliver.
Here’s the most useful relationship in the whole mastering stage, and it’s worth memorizing: how loud you can get your song depends almost entirely on the state of your low end. Two mixes with the same balance can end up 3 dB apart in loudness purely because of the state of the bass.
Why low end limits loudness
A low-frequency wave is big: it has a lot of amplitude because of the energy it carries. When the master’s limiter tries to raise the song, the first thing it meets are those low-end peaks, and from there it can’t go further without shaving them.
The math that explains everything
If your bass has uncontrolled peaks, the limiter shaves them and compensates by pulling the whole song down: you end up with a quieter master and flattened low end too. If instead the bass is even and clean down low, the limiter meets a dense, constant signal and can push it much further before anything breaks.
A controlled bass = several dB of loudness for free. No mastering plugin can buy that.
LUFS and true peak, concretely
Measures how loud the song is perceived, not its peaks. It's the unit Spotify, YouTube and Apple Music normalize by: if your master is louder than their reference, they turn it down anyway. Which means squeezing the song gives you no extra volume on streaming, only less dynamics.
The real peak of the signal, including what appears when converting to compressed formats (MP3, AAC). Leaving −1 dBTP of margin avoids distortion in the conversion. Low-end peaks are the ones that exceed it most easily.
The more you flatten in search of loudness, the less range is left and the more fatiguing the song becomes. In rock/metal some flattening is part of the style, but a well-controlled bass lets you get loud WITHOUT flattening: which is why it's worth solving in the mix.
How much headroom to deliver
Delivering the mix with headroom costs nothing (it's pulling a fader down) and gives the master real room to work. Delivering a mix pinned to the ceiling forces you to redo the mix if the master doesn't come out well.
- Main bus peaks around −6 dBFS. No more precision than that is needed.
- No limiter on the main bus while you mix. If you used one to “hear how it’ll sound”, take it off before exporting.
- Export as 24-bit WAV, at the project’s sample rate (48 kHz). Don’t export to MP3 for mastering.
- If you used Console Shaperstock or saturations on the bus, check they’re not pushing the output level up.
What you should NOT chase yet
Quick route — delivering a masterable mix
Quick path
- Bass high-pass in place (30–40 Hz): no inaudible energy.
- Even bass: the limiter shouldn't react to a single note.
- Remove any limiter from the main bus.
- Pull the main bus down to peaks around −6 dBFS, without touching the internal balance.
- Check bass + kick alone: they shouldn't be near the ceiling.
- Export 24-bit WAV at 48 kHz.
Expected result
Expected result
A masterable mix: peaks around −6 dBFS, no limiter on the main bus, with the bass clean down low and even in the low end, exported as 24-bit/48 kHz WAV. And a clear idea of why this matters: the state of your bass defines how much the master can raise the song without flattening it. Last step: the bass checklist before mastering.