Sub bass

Role in the mix

Sub bass is the part of a bass sound below 100 Hz, often a dedicated sine wave (or filtered triangle), that you feel in your body more than you hear with your ears. It is the foundation of house, deep house, techno, dubstep, drum and bass, UK garage, grime, dub and modern reggae, and of many electronic pop arrangements in which the “audible” bass (mid bass, reese, growl) is a separate layer. The goal of the sub mix is stable, mono energy, one clear note, a precise relationship with the kick, and translation on systems that cannot reproduce the sub (through the harmonics of the upper layer or controlled saturation). Difference from the 808: sub bass is a continuous bass voice (sustained, legato notes), not a hit with a decay.

Choosing the sound

• Pure sine wave: the cleanest, but inaudible below 50 Hz on small systems. Use it with a mid layer.
• Triangle or slightly saturated sine: adds the 3rd and 5th harmonics, so it is more audible.
• Synth: in FL Studio, 3x Osc (sine wave), Sytrus, FLEX, Harmor; alternatives Serum, Vital (free). Turn off unison and detune on the sub oscillator; use retrigger or free phase depending on the result: with phase retrigger at 0° every note starts the same way (consistent punch), while with free phase every note changes slightly (more “analog” but less consistent).
• Sub + mid layering: sine sub with an LP at 100–150 Hz + a mid layer (reese, filtered saw, growl) with an HP at 100–200 Hz. Align phase and crossover: invert the polarity of one layer and keep the version with more energy in the crossover zone.
• Register: notes between E1 (41 Hz) and E2 (82 Hz) for the fundamental; in DnB and dubstep often F1–A1.

Gain staging

Sub has a very low crest factor (sine ≈ 3 dB): lots of RMS energy with moderate peaks. Keep it at peaks of −8/−6 dBFS and check with an LUFS meter that it does not dominate (short-term) over the kick in club genres.

Corrective EQ

• HP at 20–30 Hz (even on sine waves: fast envelopes generate energy below the fundamental).
• LP at 100–200 Hz on the sub layer if there is a mid layer.
• Resonant notes: some notes resonate more than others (also because of the listening room!). Check with an analyzer that every note in the line has a similar level; if not, fix the note velocities or use dynamic EQ/compression.

Creative EQ

Boost rarely. If the sub is weak, change the octave, the waveform or the level before adding dB at 40 Hz.

Compression

• Light compression (opto or VCA, 2:1–3:1, attack 20–40 ms, release 150–300 ms, 1–3 dB) to even out different notes.
• Multiband on the bass bus (Fruity Multiband Compressor, Maximus, Pro-MB) to lock the energy below 100 Hz independently of the mid layer.
• Release times that are too fast on a sine wave cause distortion (the compressor follows the waveform): do not go below 50–80 ms.

Transient shaper

Useful only to give notes a slight attack (Attack +) when there is no kick defining them (e.g. offbeat sub lines in UK garage).

Saturation and distortion

• Light saturation (Distructor tape, Saturn 2 “Warm Tape”, Decapitator) to add perceivable harmonics; make sure the sub level does not drop.
• Low Lifter to generate harmonics above the crossover.
• Heavy distortion only on the mid layer, never on the pure sub (it turns to mud at 100–300 Hz).

Delay and reverb

No. The sub is dry and mono. Effects only on the mid layer (above 150–200 Hz).

Modulation

None on the sub. Chorus, flanger, phaser, unison and filter movement go on the mid layer.

Stereo and panning

Absolute mono. On every sub: Fruity Stereo Shaper or Spreader with Low Bypass and Mono, or the mixer track’s Stereo separation knob. For vinyl mastering, a stereo sub is unacceptable.

Sidechain

• House/techno: deep sidechain from the kick (6–12 dB, attack 0–2 ms, release 80–200 ms in time) or volume shaping with a “pumping” shape (Gross Beat, LFO Tool, Kickstart). The sub often does not play at all under the kick (offbeat bass).
• DnB/dubstep: short ducking (30–80 ms) from the kick; the sub holds the note between the hits.
• Dynamic EQ on the kick band only when the sub note has to stay continuous.

Automation

• LP on the mid layer (not on the sub) for build-ups.
• Mute the sub in the bars before the drop, bring it back in on the first beat.
• Sub volume slightly higher in the drop (+0.5/+1 dB).

Differences by genre

Common mistakes

• Stereo sub or sub with unison: low end that disappears in mono and in the club.
• Sub that is too loud because it was judged on headphones or in an untreated room: always check with an analyzer and on multiple systems.
• Two subs (808 + synth sub) playing together: cancellations and beating.
• Notes that are too low (below 35–40 Hz) in a track for streaming: invisible energy that costs loudness.
• Distortion on the pure sub: mud.