Wide on headphones, hollow in the venue
You set up two microphones in front of an acoustic guitar, move them a fair distance apart and hit record. On your headphones the result sounds big and spacious: exactly what you were after. A week later you hear that same recording through the mono speaker of a phone, or through a venue system that sums left and right. The low midrange has vanished, the guitar sounds hollow and tinny, and the width you loved so much is nowhere to be found. Nothing is broken; something simply happened that you did not account for when placing the microphones.
Two microphones deliver two channels, and that is not yet stereo. A stereo image only arises when those two channels differ in a consistent way in time and in level, exactly the way your ears naturally do with each other. Which of those two differences plays the leading role is up to you, through the geometry of your setup: how far apart the microphones stand, at what angle they sit and which polar pattern they have. And that same choice determines whether your recording holds up when someone sums it to mono.
What you learn in this chapter
- You recognize time and level differences as the two building blocks of every stereo image.
- You distinguish XY, spaced pair, ORTF and other near-coincident variants, Mid/Side and Blumlein, and know what each setup costs and delivers.
- You keep phase and polarity apart and recognize comb filtering by its sound, not just by a graph.
- You check mono compatibility with a fixed routine instead of on hope.
- You frame the 3:1 rule as what it is: a heuristic against bleed interaction, not a guarantee of the most beautiful stereo image.
Who this chapter is for
For anyone who records acoustic sources, whether that is a singing voice, a guitar or a room. Chapter 25 on polar patterns and placement is a pleasant preparation, but not a requirement. Two microphones are ideal, and a matched pair is not needed to learn: part of the listening experiments you do with a single mono recording and your DAW, without buying anything. If you work on headphones in a small room, that is no handicap, provided you take the mono check seriously.
The core idea in one paragraph
All classic stereo techniques sit on a single axis: from coincident capsules that produce only level differences, through near-coincident setups that combine time and level, to widely spaced microphones where time differences dominate. The further you move toward the spaced end, the more spacious the recording usually becomes, but the more vulnerable the sum to mono becomes to comb filtering. This chapter teaches you to make that trade-off deliberate, so that your setup becomes a choice instead of a gamble.