Phase Relationships
Vocabulary
Phase (Drums)
When multiple microphones capture the same drum hit from different distances, the sound arrives at each mic at a different time. When these signals are summed, the time differences cause frequencies to cancel (destructive interference) or reinforce (constructive interference). Phase alignment is the first step in any drum mix.
Multi-mic drum recording creates phase problems. The snare mic and the overhead mics capture the same snare hit at different times (because they’re different distances from the drum). When summed, the time offset causes cancellation at certain frequencies — the snare sounds thin, hollow, or strange.
Check phase between every pair of drum mics: kick and overhead, snare top and snare bottom, close mics and room mics. Flip polarity on one mic and listen — if it sounds fuller and fatter with the polarity flipped, leave it flipped. If the timing offset is too large for polarity to fix, nudge the tracks in time to align the transients.
Start with the overheads as your reference. Everything else aligns to them.
Building the Kit
One approach that works consistently:
- Start with the overheads. Get a balanced stereo image of the kit. The overheads are the foundation — they should sound like a complete drum kit by themselves.
- Add the kick mic. High-pass the overheads to remove their kick content. The close kick mic provides the punch; the overheads provide the context.
- Add the snare mic. Check phase against overheads. The snare mic adds crack and body.
- Add room mics. These add size and ambience. Compress them hard for a big room sound, or use a transient designer to control the sustain.
- Add toms last. Gate or expand to remove bleed. Toms are typically the least present element in the kit — they appear for fills and specific moments.
This overheads-first approach works because it starts with the most complete picture and adds detail. The alternative — building from kick and snare up — can work but risks losing the natural kit sound as you stack close mics that have different perspectives.
Processing Individual Drums
Kick
The kick needs two things: low-end weight and upper-mid click. The fundamental lives around 50–80 Hz. The beater click lives around 3–5 kHz. Scoop the boxy frequencies between 200–400 Hz if they’re clouding the low end.
Compress with a medium attack (5–10ms) to let the beater transient through, then grab the body. A transient designer can add click without compression artifacts.
Snare
The snare’s crack lives around 3–5 kHz. Its body is around 150–250 Hz. The wires (rattle) are in the 5–8 kHz range. A common issue: snare bottom mic adds wires but also adds bleed. Gate it or blend carefully.
Compression shapes the snare more than any other processing. Fast attack kills the transient (rounder, further back). Slow attack preserves it (snappy, forward). Parallel compression on the snare bus adds sustain without losing snap.
Toms
Gate toms to remove bleed between hits. Use the gate parameters from Chapter 6 — hold and release are critical for keeping the full sustain without choppy cutoffs. EQ to taste: toms often need a low-mid cut around 300–400 Hz to remove boxiness.
Overheads and Room Mics
High-pass the overheads aggressively (100–200 Hz) so they provide shimmer and width without low-end mud. The close mics handle the punch.
Room mics are the secret weapon for big drum sounds. Compress them hard (10:1, fast attack) and blend underneath the close mics. The heavy compression brings up the room ambience and creates sustain. Adjust the room mic level to control how “big” the drums feel.
Bus Processing
On the drum bus, a gentle compressor (2:1–4:1, slow attack to preserve transients) adds glue. The shared compression makes the kit breathe as one instrument. Add a touch of saturation for warmth. High-pass at 30–40 Hz to remove sub-bass rumble.
Programmed Drums
Drum machines and programmed beats skip the phase and mic-bleed problems of live drums but bring their own challenges. They can sound stiff, sterile, and disconnected.
Add life by:
- Varying velocity on individual hits
- Using a groove template or quantize offset for swing
- Processing through saturation and room reverb to give them a sense of physical space
- Using parallel compression to add the sustain and room ambience that programmed drums lack
What to Practice
- Check phase on a multi-mic drum recording. Flip polarity on the snare bottom mic, then the overheads, then the room mics. Note which combinations sound fullest.
- Build a drum mix from overheads down. Get the overheads sounding like a complete kit, then add close mics one at a time. Notice how each addition changes the overall picture.
- Set up parallel compression on a drum room mic. Crush it hard and blend underneath the close mics. Find the level where the room adds size without taking over.
- Gate the toms. Experiment with hold and release times until the full sustain comes through without choppy cutoffs or bleed artifacts.
