5 min read
How to record two microphones at once, and keep them usable in post
Two microphones only help if they arrive in post as two tracks. Recorded to one summed channel they mostly create phase problems.
Interviews, two handers, podcasts and boom plus lav setups all need two microphones running at once. The technical part is easy. The part that goes wrong is what post receives.
Route them to separate tracks, always
A recorder with two XLR inputs writes a two channel file where input 1 is channel 1 and input 2 is channel 2. That is what you want. What you do not want is a summed mono mix, because once two voices share one channel you can never fix a level imbalance or a rustle on one mic.
Watch the stereo trap
Many cameras and interfaces label two inputs as a stereo pair. Two different mono microphones are not a stereo pair. The file is still two independent channels, but downstream tools may treat it as stereo and pan boom hard left. In post, split it into two mono files and place them on separate tracks.
Level each input independently
- Set gain per microphone, not with a linked stereo control.
- Aim for peaks around minus 12 to minus 6 dBFS on 24 bit.
- Give the quieter speaker more gain rather than fixing it later.
- Use a limiter on the loud one if the conversation gets animated.
Phase and distance
If both microphones pick up both people, keep the distance between them at least three times the distance from each mic to its subject. Ignoring that gives you a hollow comb filtered sound as soon as you mix the two tracks.
Label before you leave
Name the tracks on the recorder if it supports it, so the metadata travels with the file. If not, rename the channels after the split so post gets MARIE and PAUL rather than 1 and 2. Our splitter reads recorder track names automatically and lets you rename anything before export.