Acoustic drum overheads and room mics

Role in the mix

Overheads and room mics are the stereo image of the drums: they tell you where each piece of the kit sits, how big the room is and how much the drums "sound together". In classic rock mixes the overheads are the drums and the close mics are reinforcement; in modern mixes (metal, pop rock) the close mics and samples carry the punch and the overheads carry cymbals and image. The room mics give size, sustain and aggression (especially when compressed). The main problem is phase: overheads and room mics receive the same hits as the close mics, delayed (≈ 2.9 ms per meter), and the sum can reinforce or cancel kick and snare.

Recording and configurations

• Spaced pair / A-B: two condensers 1–1.5 m above the kit. Wide and airy but with phase risk; make sure the snare and kick are equidistant from the two mics (measure with a tape or a string).
• XY / ORTF: coincident or near-coincident, narrower image but mono-compatible.
• Glyn Johns: one mic above the snare (about 1 m) and one near the floor tom pointed at the snare, at the same distance from the snare; plus the kick mic. Natural, full-bodied image.
• Recorderman: two mics at the same distance from kick and snare, one over the drummer's shoulder.
• Room: pair at 2–5 m, or a mono mic in front of the kit; "trash" mics (distorted dynamic, squashed ribbon) for color.

Sound On Sound points out that the overheads are often late and sometimes of opposite polarity relative to the close mics: check every pair (kick-overhead, snare-overhead).

Gain staging and alignment

• First of all, check the polarity of each close mic against the overheads (invert and listen for where kick and snare have the most body).
• Time alignment: you can move the overheads back a few ms to align them to the snare (in FL move the audio clip in the playlist with snap off, or trim the start of the sample in Edison), or leave the natural delay if it gives depth. Tools: Sound Radix Auto-Align, MAutoAlign. Don't align the room mics: the delay is their purpose.
• Levels: peaks −12/−8 dBFS on the overheads.

Corrective EQ

• HP on the overheads: it depends on your philosophy. If the overheads are "the drums", use a low HP (40–60 Hz) and keep the kick; if they are only for cymbals, HP at 150–400 Hz. An HP that is too high makes the kit small and "tinny".
• Mud 200–500 Hz: wide cut of 2–4 dB (the small room builds up here).
• Cymbal gong 400 Hz–1 kHz, and harshness 2–5 kHz: moderate cuts; dynamic EQ for loud crashes.
• Room: HP 60–100 Hz, cut 300–600 Hz (room box), LP 6–10 kHz if they are too bright.

Creative EQ

• Air on the overheads: shelf +2/+3 dB at 10–12 kHz (Pultec, Maag Air).
• Snare in the overheads: +1/+2 dB at 200 Hz if the overheads have to carry the body.
• "Dark" room mics: LP at 4–6 kHz and a boost at 100–200 Hz for a big Led Zeppelin/Bonham sound.

Compression

• Overheads: light and slow (VCA or opto, ratio 2:1, attack 20–30 ms, release 100–300 ms, 1–3 dB) to control the crashes; often none. Fast compression on the overheads raises cymbals and bleed.
• Room — the "crushed room": FET (1176 all buttons in, "British mode") or Distressor, 10–20 dB of GR, fast attack, medium-fast release (60–150 ms) set to tempo: the kit "breathes" and becomes huge. The classic example is the compressed room of "When the Levee Breaks". Blend it under the close mics.
• Drum bus: SSL G-Master Buss / Fruity Limiter COMP 2:1–4:1, attack 10–30 ms, auto release, 2–4 dB.

Transient shaper

• On room and overheads, Release + increases the sense of room (an alternative to compression).
• Attack − on the overheads softens cymbal hits that are too hard.

Saturation and distortion

• Parallel distorted room mics (Decapitator, Distructor, Fruity Blood Overdrive) for garage rock, indie, grunge: HP 100 Hz and LP 6 kHz after the distortion.
• Tape on the drum bus (Studer A800, Kramer Master Tape, J37) to round off cymbal transients.

Delay

None on the overheads. On the room, an artificial pre-delay (shifting it 10–30 ms later) increases the sense of distance.

Reverb

• If the room is good, the room mics are the reverb. If it is small or bad, use an artificial room reverb (LuxeVerb, Fruity Convolver with room IRs, Valhalla Room) on a send from the close mics, 0.6–1.2 s.
• Don't reverb the overheads (you double the cymbals); if needed, reverb only the snare and tom close mics.
• For modern mixes: very low natural room + plate on the snare.

Modulation

None (a slow phaser on an overhead in a psychedelic breakdown is an effect, not mixing).

Stereo and panning

• Overheads hard L/R (or 70–100%) for a spaced pair; XY can sit at 100% with no losses.
• Consistent perspective: if the hi-hat is on the right in the overheads, the hi-hat close mic goes right; toms panned as they appear in the overheads.
• Snare centering: the snare must appear in the center in the overheads; if it is shifted, adjust the L/R balance or the alignment.
• Wide room mics, but check the correlation: room mics out of phase with each other narrow the low end in mono.

Sidechain

• Room mics ducked by the vocal or the snare in very dense mixes (1–3 dB).
• Sidechain gate: in '80s sounds, the compressed room is "gated" with the snare signal as the trigger (natural gated reverb).

Automation

• Room mics louder in choruses and fills, lower in verses.
• Overheads lowered by 1–2 dB in passages with continuous crashes.

Differences by genre

Common mistakes

• Not checking phase and polarity: "hollow" kick and snare that you try to fill with EQ.
• HP too high on the overheads: small kit, tinny cymbals.
• Fast compression on the overheads: cymbals and bleed at maximum.
• Inconsistent perspective between close mics and overheads: toms that "jump" from one side to the other.
• Room mics used at constant volume: the kit loses dynamics between sections.