Perhaps you’ve rented a rehearsal space and want record your band. Maybe you’re heading into the wilderness to record booming thunder. You may wish to record a few bars in your home studio, or the roaring engine of a sports car.

What’s the best way to capture stereo sound?

It’s not easy to know. Every sound has its own nuance and character. Recording a classical ensemble is very different from capturing a sax solo. So, which do you choose?

Today’s post is designed to help. It introduces four popular stereo recording techniques. First we’ll read about the four stereo placement methods. You’ll learn which microphones they use, how to set them up, and how they sound, as well as their benefits and drawbacks. Then we’ll learn ways to decide which technique is best for you.

Let’s get started.

 

X/Y Pair Stereo Recording

 

x/y pair stereo recording
source: wikipedia

 

The X/Y pair technique is perhaps the most common stereo recording method. Why? It’s simple to set up and get recording quickly. Let’s take a look.

Microphone Selection, Set Up, and Positioning

The X/Y technique aligns two “matched” cardiod microphones at 90 degrees with their capsules at the same place. Of course, it’s impossible to have two capsules at precisely the same position. So, this method typically places the capsules one over the other so they are near the same position without touching.

While a 90 degree angle is most common, it’s possible to change the angle to 120, 130, or 180 degrees to have variations of the same effect. Some also use bi-directional or super-cardioid microphones, although this changes the nature of the sound.

How the X/Y Technique Sounds

The result? A clear and present recording that feels more narrow and focused than real life. Because of this, the X/Y technique doesn’t create spacious recordings with depth or “soundstage”.

Benefits

The X/Y method is simple. It’s easy to align the microphones using an inexpensive stereo bar or inside a windshield when field recording. Due to the microphone alignment, the X/Y technique is a good choice when mono compatibility is needed, or to avoid phase issues. Because of this, it’s a popular method for recording closely, such as single instruments in a home studio, or for specific sound effects where a clear and stable stereo image is preferred.

Drawbacks

Many feel the X/Y method captures recordings that are “too narrow” and lack spaciousness. Also, the sound may lack bass if cardioids are used, and may lose other frequencies when played back in mono. Because of these reasons, the X/Y technique isn’t the best choice for recording subjects at larger distances.

 

A/B Spaced Pair Stereo Technique

Need spacious recordings? The A/B technique will deliver. As the name suggestions, sound arrives at a widely “spaced pair” of microphones at slightly different times, creating a stereo effect.

Microphone Selection, Set Up, and Positioning

Two omnidirectional microphones are the most popular choice for the A/B technique. They arrange the microphones parallel to each other 40-60cm apart. Wider distances are possible, however the trade off is that sound nearer to the microphones won’t be captured as well.

How the A/B Technique Sounds

A/B stereo recordings produce a wide, spacious image. They accurately represent large spaces, and create a realistic sensation of an environment as a whole.

Benefits

Why use A/B?

It’s simple to set up and get running quickly. It provides very good frequency representation, even bass tones, which is something that other techniques lack. It’s best used to capture width, breadth, and depth. Recordings of nature ambiences and entire music ensembles shine with the “spaced pair” method.

Drawbacks

There is one major problem with A/B recordings: the do no work well in model. When attempted, listeners may hear an unpleasant comb filtering effect. There is less distinct stereo separation with this format. Also, the set up is less mobile than other methods, so it can be a pain if a project requires changing recording locations often.

 

ORTF Near-Coincident Stereo Technique

 

ortf near coincident stereo technique
source: wikipedia

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The ORTF method was designed to emulate natural human hearing. Pioneered by the French Office de Radiodiffusion Télévision Française (ORTF) at Radio France, this “Side-Other-Side” method adopts the advantages of the X/Y and A/B methods without their drawbacks.

Microphone Selection, Set Up, and Positioning

This technique calls for two cardiod microphones positioned 17 cm apart facing outwards at 110 degrees. The alignment was carefully considered; the angle was designed to mimic the “shadow” of the human head, and the spacing to match the distance between ears.

How the ORTF Technique Sounds

The result of the ORTF method is the creation of a realistic stereo field across the horizontal plane, similar to natural hearing. The cardioid microphones used do reject off-axis sounds, so less of the spaciousness of the area is captured (although wider than X/Y).

Benefits

Another simple stereo technique, ORTF is a good choice to recreate realistic human hearing. It is a good choice for mono compatibility (although not perfect), and for mobility too.

Drawbacks

Because the ORTF method uses cardioid microphones, it may not represent bass as well as techniques using other microphones. Cardioids also reject off-access sounds, so less of the “room” is captured using this method. Some engineers also noice notice a “hole” can be created in the centre of the stereo field.

 

Mid-Side (M/S) Stereo Technique

 

Mid-Side (M/S) Stereo Technique
source: wikipedia

 

In 1954, Holger Lauridsen, head engineer of the R&D department at the Danish State Radio, invented a technique while researching spatial audio. It is called mid-side stereo recording, and is a flexible – although complex – method of recording stereo sound.

Microphone Selection, Set Up, and Positioning

The M/S method uses two different microphones: a cardiod microphone (the “mid” channel) and a figure-of-eight or bi-directional microphone (the “side” channel). The technique positions the cardiod facing forward while the bi-directional records sound to the side. This recording must then be decoded. How? The method takes the bi-directional sound, inverts its phase, and copies it to a third channel. The result is three channels of audio: left (bi-directional), centre (cardioid), and right (phase-inverted bi-directional).

Software or mixing performs this decoding automatically. Or, it can be done in an audio editor manually.

How the M/S Technique Sounds

The result of this complex engineering? A stereo recording with a variable width. Raising or lowering the gain of the sides makes the stereo recording seem wider or narrower. Prefer a mono recording? Simply drop the side channels and use the cardiod channel by itself.

The M/S technique creates a solid middle image, and places elements well within the stereo soundscape.

Benefits

The M/S technique is prized for its flexibility. Attenuating the side channels allows a single recording to be transformed into a stereo soundscape with multiple widths, both during and after recording. It is also known as a “safe” stereo recording method that avoids phase problems.

It’s a compact, mobile stereo arrangement that uses its strong middle image for capturing instruments in a home studio and specific sound effects, and ambiences with detailed soundstage.

Drawbacks

What’s the downside to this method? Well, monitoring mid-side stereo while recording is tricky. It’s difficult to know what is being recorded unless the audio is being decoded at the same time. A similar concept applies when working with M/S files later, too: they must be decoded to be used, and not everyone has software – or the knowledge – to work with mid-side recordings properly.

 

The Best Stereo Recording Method

So, which stereo recording method is best?

To decide, consider the subject you’re recording. Is it a single guitar? Are you gathering field recordings of a barking dog? Perhaps you’d like to capture something more spacious, such as a symphonic performance or rainfall. It’s vital to consider the breadth of the recording needed as well as the distance to the subject. Close subjects may demand M/S or X/Y recordings. Ambient subjects are well suited to A/B recording.

It’s also important to consider mono compatibility. Will the recording be played back through a single source? Methods that reduce or eliminate phase are the best choice. ORTF works well here, and M/S is unmatched.

Do you need to be mobile? Some microphone placements are easy to pack into a windshield and carry from place to place. Other projects don’t need this and are better arranging microphones once and leaving where they will remain all day. A M/S, ORTF, or X/Y arrangement is favored for mobility.

Not everyone has the time to arrange complex microphone placements or work with unconventional channel layouts. So, ease of use bears consideration, too. If that is the case, M/S recording is best avoided.

Finally – and most importantly – consider the sound you need. Do you mind losing a bit of bass when using cardioid microphones? Prefer to mimic human hearing? Do you need to choose between a tight, focused recording or a spacious, atmospheric sound?

When you consider each of these five tips wisely, you’ll have the tools to find the stereo technique that’s best for you.