Category Archives for Stereo Recording

Stereo recording techniques – stereo mic techniques

In stereo recording, it is important to have a plan for the mic technique. There are several main stereo recording techniques to use; each have variations to try. They differ in the way that they separate the stereo information for the brain to decode. There are 4 main ways:

  • Coincident
  • Spaced
  • Near coincident
  • Baffled or binaural

Coincident mic technique
The word coincident means occupying the same space or time. That is a very good description of the coincident mic technique, since it uses two microphones at the same place, angled differently, to pick up the sound.

The most popular coincident technique is the XY method. To make an XY setup, place the mics so one mic's diaphragm is directly above the other. Angle them 90 degrees apart, and point the middle of the two toward the middle of the sound source.

This requires directional mics, like cardioids. The stereo image given by this technique is based on level differences, or the volume of the one signal compared to the other. When a sound from the far right side of the stage comes to the microphones, the mic pointed in that direction picks it up louder than the other one. The second mic still gets sound, but it's not aimed the same way, and the picked up sound is quieter. When the sound is played back on stereo speakers, the right channel will have that sound louder than the left, so it is perceived as coming from the right.

XY is the most popular coincident miking setup used, but it has its drawbacks. For example, while the XY pattern has excellent localization (the ability to determine where a sound is coming from in the soundstage), the stereo image tends to be narrow. You can help by moving the microphones closer to the sound source and surrounding them with the source, but it just won't sound as spacious as some other stereo recording setups. Another type of coincidental mic setup is called the mid-side technique. It also involves two mics, but placed in a different pattern. A single mic of any polar pattern (omni, cardioid, hypercardioid, ect.) is set up pointing straight on to the sound source. This forms the mid part of the setup. A figure-8 mic is placed in the same area with the null axis towards the middle of the sound source. (The null axis is 90 degrees away from the front of the mic.) This will pick up sound from either side of the sound source, but not in the middle, so it is called the side.

In order to play it in stereo, a decoder is needed. The decoder combines the side signal with the mid signal and separates the left from right so the recording can be heard as stereo. The side mic is the one translating to stereo. The main principle here is polarity -- anything coming from the left side will make a negative signal, while the right side produces a positive signal (providing the mic is pointed to the right). The mid mic is used to sort out the two, and you have a stereo signal. The mid-side technique also provides good localization, but requires the use of a decoder, or some smarts and a few extra console tracks.

The Blumlein pair is yet another coincidental mic technique. It uses a pair of figure 8 microphones, one above the other. They are angled 90 degrees from each other so their figure 8 patters combine to form a cloverleaf pattern. Aim the mics at the sides of the sound source (like an XY technique), and pan them opposite each other. This technique provides excellent localization, but also picks up sound from the rear.

Spaced pair stereo recording technique
Spaced pair microphones are the most basic setup for stereo recording. Two microphones are set up apart from each other to record separate signals for stereo recording.

In an AB setup, you take two mics, usually omni but they can be directional, and set them up side by side, however far apart you want them. The gap is arbitrary, from really close (about 2-12 inches) to far apart, (the width of an orchestra maybe).

The spaced pair uses a different principle of sound to relay a stereo image – time differences. When the microphones are spaced apart, sounds coming from the right side of the soundstage will reach the right microphone first. There will be a slight delay until it reaches the left, but your brain can hear that distance. When spaced pair stereo sound is played back on speakers, the right signals play from the right speaker slightly before the left. Your ears hear this time delay, and can instantly place it in the soundstage.

When you are setting up a spaced pair microphone set, you may find yourself placing the mics further apart to get a better mix of the whole ensemble. This is good, but after a while you start having a "hole" in the middle. Putting a third mic in the middle is a quick and dependable solution to this.

A variation of this setup is called the Decca Tree, named for the tree-like placement of 3 microphones. There is one for each side and one for the middle, but usually the middle one is front further than the side ones. The usual distance is half as far front as the side mics are apart. This option offers good localization with excellent stereo spread.

When you compare coincident to spaced pair stereo recording, you have two different styles. Coincident is sharp on localization, but slightly narrow in stereo image. Spaced pairs have a much nicer sound when it comes to width and ambience, but the image isn't quite as sharp. The wider you place the mics apart, the wider the image becomes, but the localization is a bit fuzzy.

Another drawback is phase problems. If your target media will always be stereo, like a CD, you don't need to worry about it. But if you expect that it will be listened to in mono, you might want to listen to how it sounds. The microphones might be out of phase with each other, causing phase cancellation when combined to mono.

Near coincident
The third type of stereo recording mic setup we'll look at is called near coincident. While the first two used level or time differences to make the stereo image, near coincident offers both. Let's look at how it's done.

Two directional mics are placed in an xy pattern, but instead of putting the diaphragms at the same spot horizontally, you space them apart about 7 inches. Often they are angled out more than 90 degrees.

This stereo recording technique offers the sharpness found in coincident patterns combined with the width and spaciousness of a spaced pair. It builds a more accurate stereo image using time and level differences, one that is understood by the brain better.

By far the most common near coincident technique is the ORTF. (It's an acronym in French for the French broadcasting system.) It says that the diaphragms must be 17cm apart, (about 7 inches), and angled 110 degrees from each other. You can either use two mic stands for this or get a stereo bar and mount both mics on one stand.

Some other near coincident techniques are NOS and DIN coming from Holland and Germany respectively. The NOS technique specifies the spacing of the mics to be 30cm with an angle of 90 degrees, while DIN specifies a spacing of 20cm and an angle of 90 degrees.

Which of the three stereo recording setups is best? I hope this doesn't surprise you, but there is no best one. What! Yep, if you pressed the question "Which is better, ORTF, NOS, or DIN?" to me, I might respond with "yes!" They each have their own sound. I tend to like the ORTF technique, but don't take my word for it. Go try yourself! But do it in some spare time so you'll know before the recording session what might work better.

Binaural
All of the stereo recording mic setups we looked at so far use either time and/or level differences to create a stereo image. We can get a fairly good stereo image from this, quite impressive actually. But let's think for a bit how we as humans hear.

We have two ears separated by a dense object in the middle. (Hmm, who's is denser, mine or yours? πŸ˜‰ ) Our ears work as omni mics, although separated by the head. The pinnae around our ears reflect the sound into the ear drum, separating the frequencies by where they come from. The [physical] head also does this, filtering out higher frequencies in the ear opposite the sound source.

When our brain hears all these patterns (level, time, and frequency differences) it decodes the information to localize exactly where the sound came from. The time and level differences are close to what is created with a near coincident mic technique. But our natural stereo hearing system uses three principles to form a stereo soundstage -- time, level, and spectral differences. How can we get something that mimics as close as possible the natural stereo hearing we use all day long?

This study is called binaural recording, trying to get a recording that sounds like you were there. There are two main ways of doing this, a baffled omni setup, or actually using a dummy head with microphones where the ears would be.

The baffled omni is easier to set up. Basically it's two omni microphones with a baffle in the middle to separate the stereo image. A Jecklin disk is a common way to set this up – take a 12inch round piece of hard material (plywood or plexiglass) and put the mics on either side.

You can buy some disks that look professional or you can make one that serves the same purpose. When you have this ready, you mount the mics on each side with the diaphragms about at the center of the disk, separate them about 7 inches, and angle them out slightly. This mimics the position of a human head and ears, giving a stereo image based on level, time, and spectral differences.

The other way to get a binaural stereo recording is to use a dummy head and put microphones in the spots where the ears should be. There are dummy heads that closely resemble a human head -- complete with nasal passages -- providing very accurate filtering resulting in superior imaging.

Summary of stereo recording techniques
Phew! That was a long way, so let's tie up the loose ends. Here's a brief summary of each stereo recording technique discussed.

Coincident stereo recording

  • Uses level differences to produce stereo image
  • Provides a sharp image, excellent localization
  • Soundstage is a bit narrow
  • Signals are mono-compatable

Spaced pair stereo recording

  • Uses time differences to produce stereo image
  • Provides more diffused stereo image, localization is a little fuzzy
  • Soundstage or stereo spread can be exaggerated unless a 3rd mic is used
  • Provides a nice sense of ambience
  • Signal may have phase problems when combined to mono
  • Can use omni mics, so low frequency sound can be better

Near coincident stereo recording

  • Uses level and time differences to produce the stereo image
  • Provides a fairly sharp stereo image with good localization
  • Stereo spread or soundstage is accurate
  • Gives more air and depth than coincident methods

Baffled omni stereo recording

  • Uses level, time, and spectral differences to produce the stereo image
  • Stereo image is sharp
  • The stereo spread tends to be very accurate
  • Realistic, more what your ears hear
  • Low frequency sound is excellent

You can use these different techniques for many effects in stereo recording, and I encourage you to try them out. What happens with each one? What are the characteristics of each? Let me know; I'd love to hear from you!

Stereo recording techniques – microphone placement

How is stereo recording done?

Stereo recording uses various stereo techniques to produce a recording, like a CD. There are different aspects in technique to consider when preparing to record stereo, like microphone techniques, placement, choice. 

Each of these sections of stereo technique has an impact on the resulting audio. Some have more, some less, but they make a difference. 

This article is meant to be a basic primer, and will focus attention to the various aspects of it. For an introduction to the idea, such as why we want to record in stereo, see the Stereo Recording Intro.

We will look at:

  • Microphone techniques
  • Microphone placement
  • Microphone choice
Let's look at some of these things... 

(If you're new to recording and want to get a better handle on things, check out the recording process page.)

Also, there is another article on choir recording that you should check out if you are interested.

Microphone techniques

There are a few standard methods of recording in stereo. They operate from a few basic principles of physics, or how sound behaves.

The main difference between any stereo recording technique is whether it focuses on time differences or on volume differences. 

If you set two microphones down, one foot apart from each other, any sound that is not coming from directly on center will arrive at one microphone before the other. Our brains can process these minute delays, forming a soundstage, or image of where the sound originated.

Level differences are different - they require directional microphones (where omni-directional mics work well for time difference). The diaphragms are placed together, as close as possible, but pointed in different directions. When a sound comes from off center, it will seem louder from the mic that is pointed in that direction. This is another way that our brains can decode a stereo recording to make the soundstage.

Branching from here, there are ways of combining the techniques to get better sounds yet, and specific instructions on how to implement them. See Stereo Mic Techniques for more the detailed discussion on this.

Mic placement

Where you place the microphones makes a big difference in stereo, as it does for any recording. It really takes some experience to hear this, so you need to try it on your own, but here are a few principles to keep in mind.

First, the blend. Any ensemble sounds more blended the further you go away from them. The bigger the group, the further away you need to be before you will have a nice blend of everything. The closer you go, the more you risk hearing individual voices, or losing the cohesive whole sound of the group.

Second, the mix. A recording is made in some sort of acoustical environment, and you need to balance the recording between the sound of the source (be it a choir, orchestra, or other ensemble) and the room reverb. 

And don't forget, keep the stereo image centered - don't let the sound become skewed to one side. Your listeners will thank you. πŸ™‚

See Stereo Mic Placement for more discussion on this topic.

Mic choice

You need some large scale framework to select mics. What kind of group will you record? Is it a choir, and if so, what size, and will they be accompanied? Or is it a small orchestra?

It is important to consider what technique you will use, such as time or volume difference (XY, AB, ORTF, etc. - see Mic Techniques ). Your strategy will dictate what mics you have to choose from.

For more on the selection strategy, see Stereo Microphone Selection.



So stereo recording can be a lot of headache, but it is a lot of fun.

Questions?

Do you have stereo recording questions? Trouble making sense of all the jargon or ideas? Trying to decide what equipment to use in which pattern? I'll be glad to help you, however I can. I see every question that comes in, and will do my best to answer your stereo recording questions.

Stereo Recording Techniques – Mic Placement

OK, now you've picked the perfect stereo recording mic technique, but where should you put the setup? Where the stereo mic setup is placed can make a huge difference in the resulting sound.

Don't believe me? Try it yourself - listen to something up close, and then move away. Move around to the sides and up & down too. Can you hear a difference? As you get further away, the sound becomes more unified, together and cohesive. It sounds more like a group. Up and down also has an impact. Higher up tends to get more back-of-the-group sounds, while lower will pick up the front row the best. Somewhere in between is usually a good point. After a point the further back you go, the less difference it makes.

Side note: get used to listening to how any room sounds. This way, you can be more intuitive in placing any microphone for recording. End note. πŸ™‚

As you move to the sides, the stereo image gets skewed -- you are not in the middle anymore. If it sounds unbalanced at the spot you want to record, it will be an unbalanced recording.

The closer you get to the sound source with your mics, the louder it gets. This seems fairly obvious, but there is another factor in this equation. Every space has a reverb unique to it, and your stereo microphones will record it. But there is a way to control how much gets recorded.

The room sound gets picked up more as you move the microphones away from the sound source. After a point, it will become loud enough to muddy the recording and lessen the clarity (if you have a big room, like a church). In the same respect, the closer the mics are to the source, the less reverb will be heard on the recording.

As you experiment with mic placement and technique, keep in mind that there is no rule that says you can only use one stereo pair. If you have (or can get!) extra mics and recording tracks, try experimenting with two stereo pairs, maybe different stereo techniques (ORTF, AB, Jecklin disk), and in different placements. This will give you more options while recording, and a fuller sound, depending on how the two stereo pairs are mixed.

When you are finding a mic position, keep in mind this good rule of thumb about placement -- the best microphone placement cannot be seen, it must be found. While you might go to a stereo recording and record with the same position you first set up the mics in, make sure that is the best one. You want to make sure you have a good sound before you start recording.

Take your time when you're doing this; it is a critical part of the recording process, stereo recording or not. It can take a long time to get the best recording position, but you want to make sure you get the best sound. Once you find a good place, you've got a lot of work done! Each recording situation is different, so you can use last time's placement to start, but see where the best one is for the current project.

Make sure you like what you are getting. If you don't, you probably won't end up with what you like either. You can do a lot with EQ and processing, but it just isn't the same as getting it right the first time around. Make sure you like the sound of the ensemble or group, the way they blend together, the way they sound as a whole, the timbre, and the mix of the sound source and the room reverb. Get it right the first time, so you won't have to work with junk you wish wasn't there.

Check out some excellent mics for stereo recording over at aZounds.com: the Neumann KM-184 is an excellent mic for working with stereo recording. I have two pairs of them, and love the way they do choirs.

Stereo Microphone Selection

What stereo microphone should you use for a stereo recording? That is an important question in any kind of recording! I hope I don't surprise you, but there is no right answer. There is no rule in recording that says, "When stereo recording choirs of about 24 voices, use a Neumann KM-184." 

Every mic has a different sound, a unique character that differentiates it from the rest. Some of them work better on choirs, while another might work better for a drum set. If you have several mic sets to choose from, listen to them all. Make a decision only after that. Even if 3 different mics sound good on a certain application, they each will make it sound different. They will affect what the end sound will be. What do you want that to be?

Apart from questions like that, there are a few guidelines for using choosing a stereo microphone.

  • XY setups require the use of cardioid mics, to separate the left and right fields 
  • An MS technique needs a figure 8 plus another of any pattern. 
  • Blumlein pairs use two figure 8s. 
  • A spaced pair sounds best with omni mics. 
  • Near coincident patterns usually require cardioid, again to separate the soundstage. 
  • Binaural recording usually uses omni microphones, because they sound a bit more natural at low frequencies, and that is closer to how our ears hear.

A good rule of thumb I use myself when shopping for mics is the old saying, You get what you pay for. An $800 mic will probably outperform a $100 mic. But above all, listen to them.

If you cannot put out enough money for a good mic set without hearing them first, see if you can rent them somewhere. It'll cost a bit, but what's a half-day's rent compared to the cost of a good microphone for stereo recording?

If there's nowhere to rent near you, you could do what I did - I bought two sets of mics to test. I tried them for a day or two, and returned the one I didn't like. Before you do this, make sure you tell your salesperson what you plan to do! The last thing you want is an extra mic set you don't need!

Something to investigate is the possibility of a stereo microphone. Instead of having two separate mics, you have everything integrated into one. Just something to think about.

Just another two analogies about mic selection. Think of each mic as colors on a palette, and you are ready to use each as it suits your purposes. Or think of it like a craftsman chooses special tools to complete a work of art. That's really what mic selection is all about.

Introduction to Stereo Recording

Stereo recording is a multi-faceted approach to recording that posits very realistic recordings in reward for distinctly challenging situations. It's not something we do or think about consciously, but basically any recording uses stereo in some sense. 

First, let's examine this thing called stereo recording by dividing the term in half. We know what recording is all about, so we'll focus now on the stereo part. 

Stereo means sound that comes from two sources or speakers to surround the listener and make him think it's coming from more than one place. It's basically the first version of surround sound, but with only two speakers. That's why they call the playback systems stereos.

Think of it this way - you have two ears, and they give you an incredible amount of detail. Try closing just one ear for a minute, and pay attention to all the sounds you hear. Pretty boring, isn't it? The second channel of information gives you detail in time and loudness that make the whole aural experience much richer than if you had two noses and one ear. 

These small cues in time and loudness difference help us to pinpoint the location of sounds on a 3D level. We can point to a source in a 360 degree plane around us horizontally and vertically, and we perceive depth. All with two ears. This is why the recording world uses two channels (or more) in basically all recording releases. 

With two speakers placed a small distance apart and a stereo track (remember, two channels here, left and right) you have a soundstage. Stereo recording exploits the sound stage by filling it up with voices/instruments at different places.

The most basic form of this is recording the tracks and mixing them to different positions in a stereo mixdown. This creates an articifial stereo experience, because everything was tracked separately and mixed together - it's not real. Stereo recording tries to emulate and reproduce a real sound, a real soundstage. Whether it's a choir/orchestra combination or a single classical guitar, we go for real. A real sound like that is pleasing to listen to, and it accurately reproduces the original performance. 

Apart from the realness factor, logistical factors necessitate using stereo. For example, take a choir scenario: you have a 36 voice choir to record. There's no way you can get 36 mics in to record each person individually, unless your studio has bottomless funding. You have to do some sort of grouping and mixdown. You can learn more on the choir recording page. 

So we use stereo in recording to reproduce a real, life-like, you-are-there aural experience that sounds pleasing to the ear. We do it because we have to sometimes, but because we like the sound. 

How To Do Choir Recording

Choir recording can be potentially frustrating or very rewarding. It is different than recording solo vocals or duets. There are new things to think about, different problems to face. We'll look at the challenges unique to recording a choir. I'll be targeting specifically a choir of voices, but you can use these techniques for instrumental ensembles too (orchestra, band, or other ensemble).

Here is a bird’s eye view of what we are going to look at:

  • Stereo recording 
  • Room sound 
  • Mic choice 
  • Microphone technique
  • Mixing choir recordings
  • Special effects - EQ, compression, reverb, etc. 

What about stereo sound?

Stereo recording is a sister subject of choir recording, something you need to know a bit about. I'll do a quick primer, but you should mosey on over to the stereo recording page to learn more about it. 

A stereo track is simply two coordinated mono tracks played on two independent speakers, arranged on either side of the listener. They can be either speakers or headphones, but the have to be two separate sound sources or tracks.

To record stereo, you record two separate tracks, one for the left output, and one for the right. They don't necessarily have to be placed in a left/right pattern, but they will be panned out in the mix. When you play this back (on a stereo sound system) you will hear a soundstage. It gives dimension, or depth and width to the field of sound you are hearing, a feeling of "being there." 

When you record one voice, stereo doesn't make so much sense (although you easily can). With one track, it can be panned wherever you want - you can make it sound like it's coming from the left or right. But with a choir or chorus, there is a sense of depth and location - and spatial positioning.

Have you ever listened to a recording in mono that should've been in stereo? Didn't it just seem to lack depth, clarity, and sparkle? I think stereo adds so much to a choir recording that I wouldn't do without it.

Room Sound

If you were to record a choir, where would you do it? Can you get 25 people in your bedroom or living room? (25 people is a medium sized choir.) You might be able to do it, but space sort of comes at a premium then. If you did it, you might notice that the group sound is just not what it should be. This comes from any number of things, but the room in which a choir is singing will have an impact on how they sound. 

Also, anything needs breathing space to sound good. Try going into a closet or other very tight space, and sing a few notes, or play a song on your guitar. Now go into the living room, or other bigger space (but not outside). Does it sound different? How? This is a good exercise to experiment with, as it will give you an understanding of how room sound works. 

A big group or choir needs a big space, but proportional to its size. Also, a choir will sing better (and love it) in a pleasing acoustical space - it helps their blend and the reverb reinforces their singing. 

When you're placing mics for a choir in a larger room (or any size really), the distance you stay away from the group will make an impact on the mix between voice and reverb sound. But that's a topic for the mic technique section. 

Mic Choice

One difference between recording solo vocals and a choir is the microphone situation. Obviously, you can't have a Neumann microphone for each choir member. Besides breaking the bank, you would have to separate the choir, and have a royal mess of mic cables. And could your recorder handle that many tracks?

Even if you went to all that trouble, and tracked each individual voice, you wouldn't have the "choir sound" that we want. The blend wouldn't be there - you would have to blend them electronically. Have you ever heard of the saying "The whole is more than the sum of it's parts"? This is one case where that is true!

Instead, use a stereo setup. A pair (or several) of mics placed at strategic spots will will do well. What spots? See below.

So when we record the choir as a whole, we need to make sure the mix is right. No one person should stand out above the rest; everyone should be on pitch and well blended. If you do your choir recording without checking these things, you might be disappointed with the results.

In other words, you need to mix the choir as you record.

Mic Technique

Well now, this cannot be covered in a few short paragraphs! But we'll do our level best, reserving a whole other page for further discussion on this matter. 

I tend to like to use stereo recording for a choir recording. As you will see later, stereo is a 2 track attempt at reproducing the sound as closely as it can, giving you a "being there" kind of sound. Stereo stuff uses 2 or 3 mics placed in predefined patterns, like XY, ORTF, Mid-Side, DIN, AB, and so on. Each of these placements has particular blessings and difficulties, or else there would be one grand accepted method. There isn't. 

Another popular way of recording a choir us seperating the parts (soprano, alto, tenor, bass, or SATB) and tracking each one separately.This gives more control in the mixing environment, like if the soprano overpowers everyone else on a line, you can pull them back. This method will give you 4 tracks (or however many you use) to play with, rather than the 2 or 3 with stereo. I've had good results with this when mixing these 4 tracks with a stereo pair of the whole choir.

Like I said earlier, I prefer the stereo recording strategy, because of the more accurate sound I get. But I do say that with understanding - it is slightly less flexible when it comes to mixing. I recommend you read my article on choir mic technique that goes into more detail on this subject. 

Mixing

Mixing a choir recording is unique from a multi instrument/vocal recording. In one sense, it is easier, but in another it has new challenges that complicate it further. 

With a stereo recording you have two tracks, that need to be panned far left and far right. That's simple enough, but all the other mixing needs to be done during recording. If a voice is standing out in a certain position, move that person back, or beside a person that blends a bit better. If you need more alto sound, switch some alto singers front and the overpowering parts back. A solo needs to stand out in the front, not too far that they dominate, but not back far enough that they are drowned out. 

If you record each part separately, you have more options for panning the material. For this, I'll save the goodies for the specialized mixing for choirs page. 

When working in the post-recording environment, you want to avoid bold or indiscreet plugins or processors. You don't have other tracks to mask the silly sounding stuff - choirs, chorales, choruses, orchestras, instrumental or vocal ensembles, etc, need a natural sounding recording. For this most of the fun weird stuff is out, like extreme echo, flanger, pitch modulation, etc. All your processing will do it's best to remain discreet, indistinct. Unless you are going for a purposefully distinct sound, use caution. 

Special Effects - EQ, Compression, Reverb, etc. 

These are fun aspects of choir recording, simply because of what you can make a choir sound like. Combined with the study of mic placement and technique, you can make a choir sound like what you want to! That said, it is your job to make sure they sound their best. 

I use EQ some on choir recordings, to help me make up for the mistakes made in mic placement. But your goal is a natural sound, right? Lot's of EQ will start to make the recording sound articifial, a no-no in this world. The rule is easy does it! EQ can be a life saver, but it needs to be used sparingly on choir recording. That said, it is almost essential.

Compression is another handy tool, but again, to be used with caution. (As a matter of fact, anything you use on a stereo recording or choir recording should be used with caution!) A compressor will start to suck away the dynamic range of a choir, taking away their work on subtle dynamic nuance. I generally use a touch of compression, but keeping a good deal of breathing space for the group. 

Reverb is another tool I love. You can record in good sounding spaces, but somethimes you need to fill things out just a tad. A reverb (set to a gentle sound, remember!) will do wonderfully. The problem is that many times it is very difficult to get a pleasing sound. With so many knobs to turn, a reverb plugin can be frustrating when you don't know which one to turn to get the sound you're looking for. But take heart, you will find it eventually, though it may take you a while at first. πŸ™‚ 

Any other special effects are touchy - if you try weird stuff your choir recording may end up sound, well, weird! I use a de-esser sometimes, and a smidgeon of stereo positioning (but only to correct errors that happened previously), and a few others occasionally, but the bread and butter stuff are the EQ, dynamics, and reverb. 

Choir recording is a stretch for a recording engineer, but a rewarding one nonetheless. It fills my ears with joy when I sit back and listen to a wonderful choir recording - you know what I mean, right? I enjoyed this survey of choir recording, and I hope you did the same. 

I am always thinking about ways to make this more helpful to you as a choir recording engineer, so if you have any ideas to help me or questions you would like addressed, do send your input on choir recording.


Decca Tree Stereo Recording Setup

A Decca tree stereo recording setup involves three mics that mix together to give a pleasing, accurate stereo image. Half of the name came from the Decca recording label, who invented the technique, and half came from the how the setup looks - kind of like a tree. 

The first part of the Decca tree stereo recording setup is two omni-directional microphones, in a spaced pair configuration. They are usually placed between one and six feet apart. This provides the foundation of the stereo image for the recording. 

The second part is a third omni mic, placed in the middle of the first two, and slightly front. This mic adds clarity and a lot more placement information in creating a soundstage in the mix. 

The general rule of thumb for placing the third mic is not hard. Exactly in the middle between the outer two mics, and slightly in front. To determine how far front, take the distance between the two side mics, and divide by two. For example, if the left and right microphones are two feet apart, put the center mic one foot in front. 

This configuration looks and works a lot like a simple AB spaced pair stereo recording mic setup. The difference of the third mic adds precision in pinpointing the "location" of sounds when you listen over a stereo system. 

When you mix a the tree stereo pattern, pan the outer mics to hard left and right, and leave the center mic panned to the center. Remember, the rules are not absolute - you are free to modify as needed to suit your purposes. 

As with any spaced pair stereo recording pattern, you don't want to let the mic spread get too big. The further apart the omni mics are, the more "gaps" you will notice in the final product. If the microphones are just too far apart, the mix won't sound unified - it will seem disjointed and far apart. 

What microphones work best with a this recording setup? The only requirement is that they be omni-directional. You can use cheap ones, or you can use expensive ones. I use a pair of Earthworks QTC-40 omnis for the sides, and an Audio Technica AT4050 for the center. The AT4050 is switchable between omni and cardioid, so that works well for me. 

I really like the quality of recording that these mics give me when working in a Decca tree format. The stereo image is superb, and overall, it's just a lot of fun! 

In recap - the Decca tree stereo recording setup uses three omni mics, two sides, and one center, slightly in front of the sides. It offers a precision stereo image, and works with all kinds of omni microphones. Keep the setup close enough together, and you'll have great results. I love the sounds I get from my Earthworks QTC40s and Audio Technica AT4050. 

Photo of Rode NT4 Stereo Mic

What is a stereo microphone?

Simply put, a stereo microphone is two regular studio microphones in a single unit.

Really, it’s that simple! They are arranged in various ways to achieve different results or sounds, but the unit is the same – a stereo mic is two diaphragms or capsules on one microphone body.

They are distinct from a matched pair of mics. Various models available come in a set, advertised as a stereo pair, but it is not a stereo microphone. A stereo pair is two separate mics, a stereo mic is one integrated mic.

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