Room and Ambient Mics for Recording: Placement, Phase and Mixing
Updated: 2 days ago
Room mics, also called ambient mics, are microphones placed away from the instruments to record the sound of the space they are playing in. On drums they give you size and air, on a band recorded live they are the glue that makes separate instruments sound like one performance, and pushed hard they become an effect of their own. This guide covers the main room mic setups (mono, stereo pairs, far mics and crushed mics), where to put them, how to deal with phase, which microphones work, and how to mix them so the room helps the song instead of drowning it.
We record most bands live in one room, so room mics are not an extra for us. They are often the most important channels in the session. A close mic tells you what an instrument is. A room mic tells you where it was and how hard it was played.
Room mics at a glance
Mono room mic: one mic a few metres in front of the kit or band. Simple, punchy, easy to compress.
Stereo room pair: two mics for width. Spaced pair, XY, ORTF, Blumlein or mid-side.
Far room mic: as far away as the room allows. Big, late, dramatic.
Crushed room mic: a room mic compressed hard, often with an 1176 in all-buttons mode. Aggression and sustain.
Front-of-kit or "trash" mic: a cheap or odd mic near the kit, distorted or squashed for character.
Rule of thumb: sound travels about 34 cm per millisecond, so every metre of distance delays the room mic by about 3 milliseconds.
What room mics actually do
Close mics capture the direct sound of an instrument a few centimetres away, which is not how anyone hears music. People hear instruments in a room, with reflections from walls, floor and ceiling arriving a few milliseconds after the direct sound. Room mics put those reflections back. The result is depth (things sound near or far), size (the kit sounds like it takes up space) and cohesion (the band sounds like it was in the same place at the same time).
Room mics also record time. Because they are further away, their signal arrives later than the close mics. A small delay makes the sound bigger and softer. A larger one starts to sound like a space you can hear. That delay is the tool, and the problem, at the heart of every room mic decision.
Room mic setups, one by one
1. The mono room mic
One microphone in front of the drum kit, usually one to three metres away at about chest height, pointed at the kit or slightly at the floor in front of it. It is the quickest way to make a drum recording sound like drums. Because it is mono, it sits in the centre with the kick and snare and never fights the stereo image.
Try a large-diaphragm condenser in omni or cardioid, a ribbon if you want it darker, or a big dynamic like an AKG D20 or Sennheiser MD 421 if the room is harsh. Move it before you EQ it. Thirty centimetres forward or back can change the sound more than any plugin. More on those mics in the AKG D20 for recording and vintage Sennheiser microphones.
2. The stereo room pair
Two mics give you width and a sense of where things are. The common arrangements:
Spaced pair (AB): two omni or cardioid mics a metre or more apart. Wide and airy, but check mono compatibility.
XY: two cardioids with capsules on top of each other at 90 to 120 degrees. Solid in mono, a little narrow.
ORTF: two cardioids 17 cm apart at 110 degrees. A good balance of width and mono safety.
Blumlein: two figure-8 mics (often ribbons) crossed at 90 degrees. Very natural, captures a lot of room from front and back.
Mid-side (MS): one forward mic plus a sideways figure-8, decoded to stereo. You can change the width after recording.
For a band recorded live, a stereo pair placed where you would stand to listen is often the best-sounding mic in the room. A useful habit is to treat that pair as the main picture and ask what the close mics need to add, not the other way around. More on stereo placement in the hard pan: LCR mixing and the live soundstage.
3. The far room mic
As far away as the room allows: the back wall, the corridor, the top of a stairwell. The most famous example is "When the Levee Breaks", where Led Zeppelin recorded John Bonham's drums in the stairwell of Headley Grange with microphones hung high above the kit. The drums on that song are mostly room.
Another is David Bowie's vocal on "Heroes". Tony Visconti placed three mics at different distances in Hansa's hall and gated the far ones so they only opened when Bowie sang loud enough to reach them. The room literally responds to the performance. We tell that story in About a Studio: Hansa Studios, Berlin.
4. The crushed room mic
Compress a room mic hard and the cymbals wash out while the drum hits and the room tail jump up. It is one of the most exciting drum sounds there is. The classic tool is an 1176 with all four ratio buttons pushed in, but any fast, aggressive compressor works. See our outboard gear favourites for the usual suspects.
The most famous accident of this kind happened at London's Townhouse Studios around 1979, when engineer Hugh Padgham heard the heavily compressed talkback mic on an SSL console, added a noise gate and got the exploding gated drum sound of Peter Gabriel's "Intruder" and Phil Collins' "In the Air Tonight".
5. The front-of-kit or "trash" mic
A cheap dynamic, an old PA mic or a lo-fi condenser placed in front of the kit at knee height, then distorted, filtered or squashed. It adds grit and energy that clean room mics do not. Many engineers keep one odd microphone just for this. Our list of unknown microphone brands has some candidates.
Where to put room mics
Walk the room while the drummer plays. Put one ear where it sounds best, cover the other, and put the mic there.
Avoid the middle of the room and the exact centre between parallel walls. Standing waves make the low end boomy or thin.
Corners exaggerate bass. Useful for a dark, heavy room sound, bad for clarity.
Height matters. Low mics get more kick and toms, high mics get more cymbals and ceiling.
Point figure-8 and cardioid nulls at what you do not want, such as a loud guitar amp.
If your room sounds bad, room mics will make that obvious. Some rooms need a few absorbers or a rug before the room mics become useful. We cover that in taming mud and reflections in DIY recordings and on-location recording in a difficult room.
Room mics and phase
Because room mics are further away, their signal is delayed compared with the close mics. When you mix them, some frequencies add up and some cancel. That is phase, and it is why a kick drum can suddenly lose its low end when you turn the room up.
Listen with the room mic in and out, and with polarity flipped. Keep whichever gives more low end and punch.
Try nudging the room tracks earlier to line up with the close mics. The drums get tighter and punchier.
Or leave the delay on purpose. The delay is what makes a room sound big. Aligning everything can make the kit sound small again.
High-pass the room mics if the low end fights the kick. Often 80 to 150 Hz is enough.
No setting is correct in general, only the one that suits the song. Our longer explanation is in the divided bass: phase alignment and the physics of acoustic delay.
How to mix room mics
Start the mix with the room mics, not the close mics. Push up the room pair until the kit sounds like a kit, then add the close mics only until the details you are missing come through. Mixes built this way sound like a band. Mixes built from close mics with room added at the end sound like a sample library with reverb.
Compress the rooms, not only the close mics. A little compression brings up the tail and makes the kit feel bigger.
Parallel-process them. Blend a crushed copy under a clean copy. More on parallel processing.
Automate them. More room in the chorus, less in the verse is an easy way to make a song lift.
Use them instead of reverb. A real room mic almost always beats a plugin reverb on drums.
Room mics in a live band recording
When a band plays together in one room, every microphone hears every instrument. Engineers call that bleed, and many try to kill it. We think that is usually the wrong fight. The room mics are where the bleed turns into the sound of a band playing, and the close mics are there to add focus. The more you lean on the room, the more the recording sounds like a moment instead of an assembly.
Our opinion, which plenty of engineers disagree with: most home recordings do not need more close mics, they need one good room mic and the courage to use it. We explain the whole approach in recording a band live in a room and the room as an instrument.
Room mics FAQ
What is a room mic?
A room mic is a microphone placed away from the instruments to record the sound of the space. It captures reflections from the walls, floor and ceiling, which add depth, size and cohesion that close mics do not.
Where should I put a room mic on drums?
Start one to three metres in front of the kit at about chest height, pointed at the kit. Walk the room while the drummer plays and put the mic where it sounds best to your ear, then fine-tune by moving it rather than using EQ.
Should I time-align room mics?
Try both. Nudging the room mics earlier makes the kit tighter and punchier. Leaving the natural delay keeps the sense of size. Sound travels about 34 cm per millisecond, so a mic three metres away is about 9 milliseconds late.
What is the best microphone for room mics?
No single mic is best. Large-diaphragm condensers are the common choice, ribbon mics in a Blumlein pair sound very natural, and a big dynamic like an AKG D20 can tame a harsh room. Placement matters more than the model.
What is a crushed room mic?
A room mic compressed very heavily, often with an 1176 in all-buttons mode. The drum hits and the room tail get louder relative to the cymbals, giving an aggressive, huge drum sound that is usually blended under the clean kit.
Keep reading
Recorded your band live with room mics and want a mix that keeps the room? We mix indie rock, post-punk and shoegaze for artists everywhere, and live recordings are what we know best. Read how we mix live recordings, then send us the rough mix.
