Spaced microphone pairs are excellent for capturing a wide stereo image in the studio and elsewhere.
What is a spaced pair of microphones? A spaced pair is a miking technique utilizing two identical microphones separated by several feet (usually one-third to one-half the width of a sound stage) that point directly at a sound source. Spaced pairs yield wide stereo images but typically have poor mono compatibility.
Spaced pair miking techniques include:
- Spaced Cardioids
- Spaced Omnis
- AB technique (sometimes)
In this article, we’ll further define what spaced microphone pairs are and take a closer look at each of the spaced pair techniques mentioned above.
Before we get into spaced pairs specifically, you may want to check out my article Top 8 Best Stereo Miking Techniques (With Recommended Mics).
Definition Of A Spaced Pair Of Microphones
Let’s break down the term “spaced pair” for a better understanding.
We’ll start with the simple “pair,” which means that there are two identical microphones. Theoretically, two microphones with very similar specifications (polar and frequency response, sensitivity, etc.) could also work well. The point is that we want both microphones to act the same to sound pressure in the acoustic environment.
The term “spaced” means that the microphones are spaced apart from one another.
How far apart? Typically any spacing between one-third to one-half the width of a sound stage or acoustic environment.
Spacing the microphones within a foot from one another would generally be referred to as a near-coincident pair rather than a spaced pair. So any spacing greater than a foot could be called a spaced pair.
Applications Of Spaced Pairs
Why would we want to utilize a spaced pair microphone technique?
The immediate answer is to record a wide stereo image of an acoustic space. This is common for miking drum rooms, full bands, and for capturing general “room sound.”
It’s best to position a spaced pair of microphones symmetrically in the acoustic space to avoid an overly different diffuse field in each mic. The diffuse field refers to the reflected sounds in an environment rather than the direct sound from the sound source. For example, a mic in the middle of a room will pick up a drastically different sound than a mic in the corner of the room.
It’s also advised to position a spaced pair of microphones equidistant from low frequency sound sources like kick drums and bass guitar cabinets. Although this isn’t absolutely necessary, it will help centre the bass in the mix, which is often preferred.
The distance between the spaced pairs will determine the width of the stereo image they capture. We as humans hear stereo naturally with our two ears. The distance between a spaced pair of mics is greater (often much greater) than the distance between our ears and so the stereo image will sound wide (especially if we hard pan the mic channels to the left and right).
Why would we want a wide stereo image?
A stereo image creates realism, width, and depth in a mix. As mentioned previously, we naturally hear sound in stereo and so it’s natural for us to hear music (whether live or recorded) in stereo as well.
Having a spaced pair of microphones can add width and depth to a mix particularly when combined with spot-miking of certain element in the acoustic environment as well. In this mix scenario, we have “close up” sounds (which can be paned across the stereo field if need be) as well as distant sounds and sounds to the left and right.
Having the same sound sources within the same acoustic environment reacting with a properly set spaced pair will allow for enough differences to create a wide stereo image while still sounding cohesive.
The thing to watch out for with spaced pair setups is mono compatibility. When setting up your spaced pairs, it’s always a good idea to sum them to mono in order to test the phase of the mics within the room.
Summing to mono causes any phase discrepancies to cause deconstructive interference within the audio signals. This can seriously thin out a mix and should be addressed if it is an audible issue. Low frequency sound sources are particularly affected by this and should be placed equidistant to both microphones for the best phase coherence in the low-end, as mentioned previously.
For more information on microphones and phase, check out my article Microphone Polarity & Phase: How They Affects Mic Signals.
Common Spaced Pair Miking Techniques
Let’s now take a look at some common spaced pair miking techniques:
- Spaced Cardioids
- Spaced Omnis
- AB technique (sometimes)
Spaced cardioids is a spaced pair stereo miking technique that positions a pair of cardioid mics several feet from one another, pointed them both directly at a sound source. Spaced cardioids yield a wide stereo image and maintain some isolation from sound sources to the rear.
Spaced cardioids are great for capturing a narrow and/or wide stereo image of a sound source (depending on the spacing) without capturing too much of the room acoustics in the environment.
Since cardioid mics are unidirectional, its best to point them toward the intended sound source, so it’s common to find spaced cardioid mics at an angle.
When positioning spaced cardioids, try to make them equidistant from the intended sound source if possible especially if that sound source has a low of low-end frequencies. This will help tremendously in phase coherence when it comes time to mix the spaced cardioids.
As the diagram suggests, play around with the spacing between this stereo pair until you find the right phase coherence and stereo width for your project. As mentioned in the beginning of this article, try one-third to one-half the width of a sound stage.
For more information on the cardioid polar pattern, check out my article What Is A Cardioid Microphone? (Polar Pattern + Mic Examples).
Spaced omnis is a spaced pair stereo miking technique that positions a pair of omnidirectional mics several feet from one another and points them both directly at a sound source. Spaced omnis provide a wide, natural sounding stereo image to help accentuate a stereo mix.
Spaced omnidirectional mics will offer a more natural capture of the acoustic environment. This may cause a “muddier” capture (with much more reflections that the spaced cardioids) or a more realistic capture of the room.
Note that it is still advised to point the fronts of the omnidirectional mics toward the intended sound source. Even omnidirectional microphones become somewhat directional at higher frequencies.
Just like the space cardioids, it’s advantageous to take the time during set up to test different mic positions and spacings to get the phase coherence and stereo image you want. As mentioned in the beginning of this article, try one-third to one-half the width of a sound stage.
For more information on the omnidirectional polar pattern, check out my article What Is An Omnidirectional Microphone? (Polar Pattern + Mic Examples).
AB technique (sometimes)
The AB miking technique is for stereo applications and has two identical omnidirectional microphones at equal height, facing forward, and spaced 12 to 48 inches apart. At 12 inches, AB could be considered a near-coincident pair, while at 48 inches, AB is certainly a spaced pair technique.
The AB techniques is essentially the same as the spaced omnis. Its microphones, however, point straight forward and the spacing between the mics is more limited.
What is a stereo microphone? A stereo mic is a microphone designed with at least two capsules in a stereo configuration. Analog stereo mics output two (or more) mono signals (one from each capsule) that must be panned properly for the intended stereo image. Digital stereo mics tend to configure the stereo signal within mic before the output.
For more information on stereo microphones, check out my article Do Microphones Output Mono Or Stereo Signals?
What is a condenser microphone? A condenser mic is an active microphone that converts sound to audio via electrostatic principles. Condenser capsules act as parallel-plate capacitors that, when properly charged, will output an AC voltage (mic signal) that coincides with the movement of the mic’s diaphragm.