Stereo image, panning and mid/side

What it is and how it works

The stereo image comes from the differences between the left and right channels: in level (panning), in time (Haas, spaced microphones), in phase and in content (two different takes, reverbs). It can also be described as Mid (M = (L+R)/2: what is the same in both channels, the center) and Side (S = (L−R)/2: what is different, the sides). More Side relative to Mid = a wider image; zero Side = mono.

Typical goals of a mix: solid center (kick, bass/808, snare, lead vocal), full and balanced sides (guitars, synths, pads, choirs, reverbs), bass in mono (below 100–150 Hz), mono compatibility (the mix must also work when summed: smartphones, Bluetooth speakers, clubs with a mono sub).

Panning: strategies

• Center: kick, bass, 808, snare (or slightly off-center if the drums are miked from the drummer's or the audience's perspective), lead vocal, often the clap.
• LCR (Left-Center-Right): elements at 100% L, center or 100% R. A sharp image, widely used in rock (doubled guitars L/R).
• Intermediate panning: 20–60% for percussion, piano, secondary synths, choirs; builds a "natural" scene.
• Balance: for every element on the left there should be something similar on the right in energy and register (hi-hat right ↔ shaker left; rhythm guitar L ↔ rhythmic synth R).
• Drums: decide on the perspective (drummer or audience) and keep it consistent between overheads and toms.
• Pan law: when you move a pan, the level at the center is compensated differently depending on the DAW (−3 dB, −4.5 dB, −6 dB): check the levels after panning.
• In FL Studio every mixer track has Pan and Stereo separation (a knob that goes from mono to widened stereo, using a mid/side method); the Channel Rack channel has its own pan.

Width tools

• FL mixer – Stereo separation: reduces or increases the L/R difference (mid/side). Reducing it on bass or on overly wide synths is the first step.
• Spreader (FL): widens while keeping mono compatibility (Spread 0–100%), Separation (mid/side, can compromise mono), Low Bypass 10 Hz–10 kHz to exclude the lows, Mono to make the low part mono; vectorscope and pre/post phase meters.
• Fruity Stereo Enhancer, Fruity Stereo Shaper (L/R matrix, delay up to 500 ms for pseudo-stereo, all-pass to decorrelate), Fruity Center (removes DC offset: useful, but doesn't widen), Fruity Phase Inverter.
• Third-party: iZotope Ozone Imager (free, with vectorscope and correlation), Polyverse Wider (free, mono-compatible), Waves S1, Brainworx bx_control/bx_solo, FabFilter Pro-Q (M/S), Soundtoys MicroShift.
• Recording and production techniques: real double takes (L/R), different layers on left and right, chorus/ensemble, micro-pitch, Haas (see the dedicated guide), stereo reverbs.

Mid/side in practice

• M/S EQ: HP on the Side at 100–150 Hz; +1/+2 dB shelf on the Side at 8–12 kHz to open it up; cut on the Mid at 250–400 Hz to clean the center (see "EQ types").
• M/S compression: compress only the Mid (stabilizes vocal and kick) or only the Side (controls wide guitars and reverbs). In mastering, with great caution.
• Saturation on the Side: harmonics at the sides for perceived width.
• Limiter in M/S: Emphasis has a Mid/Side mode (it pushes harder: reduce the input by 3–6 dB).

Reference values and measurements

• Correlation (phase correlation, −1/+1): +1 = mono; 0 = independent channels; negative = out-of-phase parts (they cancel in mono). Typical mix: +0.2/+0.8 in dense sections; brief excursions toward 0 acceptable; steadily negative values = a problem.
• Width per band: below 100–150 Hz practically mono; mids moderately wide; highs wider.
• Vectorscope: vertical shape = strong center; horizontal = out of phase; a vertical elliptical "cloud" = healthy mix.
• Mono test: the integrated level shouldn't drop by more than 1–3 LU in mono; vocal, kick, bass and snare must stay clear.

Starting settings

By genre

• Trap, drill: very strong center (808, kick, vocal), wide hi-hats and melodies, ad-libs at the sides.
• Pop: vocal in the center and wide choirs; choruses wider than verses (width automation).
• Rock, metal: LCR with doubled guitars; bass and kick in mono.
• EDM: very wide drops (supersaws), mono sub, mono kick; narrower breakdowns for contrast.
• Jazz, acoustic, orchestral: realistic image according to the musicians' arrangement.

Common mistakes

• Widening everything: the mix loses center and power, and collapses in mono.
• Stereo bass (808 with chorus, bass with a widener): unstable low end and problems in clubs.
• An identical copy of the same sound L/R: it's still mono (at most a higher level).
• Aggressive wideners with negative correlation.
• Forgetting to check in mono and on a phone.

How to hear it

• Listen to the Side alone (Ozone Imager, Fruity Parametric EQ 2 with SIDE monitoring in the analyzer, or an M/S plugin): you should hear guitars, pads, reverbs, not bass and lead vocal.
• Switch to mono every now and then throughout the mix (also from the master with Fruity Stereo Shaper or the stereo separation knob at minimum).