Sub bass (the frequencies below 100Hz) carries the weight and power of your mix. It's what you feel in your chest at a club, what makes headphones feel immersive, and what gives your track presence on any playback system. But it's also the hardest frequency range to mix well. Here's how to get it right.
Rule 1: Only Two Things Live Below 100Hz
In a well-mixed track, only the kick drum and the bass should have significant energy below 100Hz. Everything else - vocals, guitars, pads, keys, hi-hats - should be high-passed to remove their low-frequency content. This is the single most important sub bass mixing principle.
High-pass everything except kick and bass. Put a high-pass filter on every channel except the kick and bass instrument. Set it at 80-150Hz depending on the source. Vocals: 100-200Hz. Guitars: 100-150Hz. Pads and synths: 80-200Hz depending on their role. Hi-hats and cymbals: 300Hz+.
This seems aggressive, but each instrument's low-frequency content adds up. Ten tracks with unnecessary energy below 100Hz creates a cumulative mud that robs your kick and bass of power and clarity. Removing it frees up enormous headroom in the frequency range where it matters most.
Rule 2: Give the Kick and Bass Their Own Space
The kick and bass need to share the sub-bass range without fighting each other. The two most common approaches:
Frequency separation. Let the kick own 50-60Hz and the bass own 70-90Hz (or vice versa). Use EQ to cut the bass at the kick's fundamental frequency and cut the kick at the bass's fundamental frequency. This creates pockets where each element dominates without overlapping.
Temporal separation (sidechaining). Use sidechain compression so the bass ducks every time the kick hits. The kick punches through clearly, the bass fills the space between kicks. This is the standard approach in electronic music - the pumping groove it creates is often desirable. Set the sidechain for 3-6dB of ducking with a fast attack and medium release that matches the groove.
Many producers use both techniques together - slight EQ separation plus sidechain ducking. This gives you maximum clarity with maximum impact.
Rule 3: Keep Sub Bass Mono
Sub bass frequencies (below 100-150Hz) should be in mono (centred, no stereo spread). There are two reasons: first, stereo sub bass causes phase cancellation on mono playback systems (clubs, phones, some Bluetooth speakers), which makes the bass disappear. Second, sub bass in stereo sounds unfocused and wastes energy.
How to ensure mono bass: Most bass synths and 808 samples are naturally mono, but check by putting a correlation meter on your bass channel. If it shows values below 0, you have phase issues. Use a utility plugin to sum everything below 100-150Hz to mono. Many mastering plugins include a low-frequency mono switch for this exact purpose.
Your upper bass harmonics (100-300Hz) can have some stereo width - it's only the sub-bass fundamentals that need to be centred.
Rule 4: Add Harmonics for Audibility
Pure sub bass (a clean sine wave at 40-60Hz) is felt more than heard on small speakers. Laptop speakers, earbuds, and phone speakers can't physically reproduce frequencies below 80-100Hz. If your bass is a pure sub with no harmonics, it literally disappears on small playback systems.
The fix: add upper harmonics. Use saturation or distortion to generate harmonics in the 100-300Hz range that give your bass presence and audibility on small speakers. The sub foundation stays, but the added harmonics ensure the bass is heard everywhere.
A common technique: duplicate your bass onto two channels. Keep the original clean sub on one, and add heavy saturation/distortion to the duplicate. High-pass the distorted duplicate at 100Hz (removing its sub content to avoid phase issues) and blend it underneath the clean sub. You get the weight of the pure sub plus the audibility of the harmonic content.
Rule 5: Monitor Accurately
You can't mix what you can't hear. Most bedroom producers mix on speakers or headphones that don't accurately reproduce sub bass, which leads to over-compensating (adding too much bass) or under-compensating (not adding enough).
Use a spectrum analyser. SPAN by Voxengo (free) shows you the frequency content of your mix visually. Compare your low-end energy to a reference track loaded in the same session. If your reference has a gentle slope from 40-100Hz and yours has a massive peak at 60Hz, you know you've got too much sub.
Check on headphones. Good closed-back headphones (Audio-Technica ATH-M50x, beyerdynamic DT 770) give you a more accurate picture of the sub range than most untreated rooms. Use them as a secondary reference alongside your monitors.
Check on earbuds and phone speakers. If your bass disappears entirely on small speakers, you need more harmonics (see Rule 4 above). If it's boomy and overwhelming, you have too much.
The Golden Rule of Sub Bass: Less is more. A clean, controlled sub bass at the right level always sounds more powerful than an excessive, muddy sub that overwhelms the mix. If in doubt, pull the bass down 1-2dB and listen again. Professional mixes often have less sub bass than you'd expect - they just use it more efficiently.
🎛️ Master Your Low End
Our Mixing Tutorial covers sub bass mixing in detail alongside the full mixing and mastering process. Learn the techniques that make professional mixes hit harder.
All the best - the Born To Produce Team ✌️
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