How to use mic positions in sample libraries
Posted: Oct 18, 2024 9:53 am
There are a lot of caveats to this post. I am not a mixing engineer. It's very possible that I've got things wrong, and I hope we can correct them in this thread. What I present here is what I have learnt from more than a decade of making mock-ups, reading about recording techniques and being present at several classical recording sessions. However, I am by no means a recording engineer, and I don't even consider myself to be particularly adept at mixing.
Also, I am approaching this through the lens of classical music, the sound of an orchestra playing in a concert hall. So it's different from what most people on this forum probably do. For other genres, such as film music, some mixing techniques will be the same. Others will be different. Perhaps [USER=11252]@NoamL[/USER] can shed some light on this. I don't know anything about recording film music, so I'm not the right person to ask.
Please bear all this in mind.
Recommended reading: ‘Classical Recording: A Practical Guide in the Decca Tradition’ by Caroline Haigh
Ann-Kathrin Dern has a good short explanation on her channel:
Getting started – one library, many mic positions
You may have been in the position of loading a sample library and being faced with an overwhelming choice of mic positions. Spitfire Audio's BBC Symphony Orchestra comes with what, 20 signals? What do we do with them? Should you use them all in your mix? God, no. No, no, no, no! If you use 20 mic signals all at once in your mix, you will get unintelligible garble. A Walla Group of orchestral mixing. So, what should you do instead? In many cases, just using your main mic signal will do the trick.
Selecting your main mic signal for the mix
Sample libraries often come with one or more ready-made mixes. Your first action can always be to try them out. If it works for your track, use it. But if they are not what you are looking for, then you need to create your own. You can do this as follows:
Often a Decca Tree is the main mic signal for a classical orchestral recording. Sometimes outriggers are added to increase the width of the sound. It's not wrong, but unusual, to use two or more stereo arrays in the same mix. If you have several stereo arrays in your library - Decca Tree, ORTF, Spaced Omnis - you will usually choose the most appropriate one for your track. This stereo array will be the only signal for your mix, or at least be the loudest one. You can add outriggers or side microphones if you need more width, and/or some room microphones (often called ‘hall’, ‘ambient’, ‘room’ or similar) for a more reverberant and spacious sound.
A common mistake is to mix in the close mic signals to all your instruments at all times. This is usually not necessary and can destroy the impression of natural depth. Why are you mixing in the close mics? Just because they are in your sample library? Turn them off. Because your mix sounds too wet or blurred? Turn down the level of your room mics instead. Try using your main mic signal without any other mics mixed in. Only if your main mic signal sounds too reverberant and undefined on its own should you consider adding some of the close mic signal. However, this is usually a sign that you have chosen the wrong sample library for your track and should use a drier one instead. The close mics are meant to accentuate specific instruments for specific phrases. They are not meant to be a constant part of the mix for all your instruments. The exception to this is brass and perhaps percussion. If the brass section does not sound clear and defined enough from your main mic signal alone, add some close mic signal. But be aware that often this isn't necessary at all.
Orchestral depth
The perception of distance is based on a combination of factors:
1. The further away a sound is, the more the high frequencies are attenuated. Bow noise, key noise, transients - all of these are reduced with distance.
2. More reverberant sound. More reverberation and less direct signal we interpret as a distant sound.
3. Stereo width. The further away an instrument is, the narrower the stereo width. When a large instrument occupies only a small part of the stereo field, we interpret this as distant. Conversely, if a small instrument occupies a large part of the stereo field, we interpret it as near.
All these aspects should work together in your mix. This will give you a sense of real depth. If they work against each other, you will not get a sense of depth. For example, if a sound source has little direct signal and a lot of reverb, but also a lot of high frequency content and a wide stereo signal, we can't interpret whether the sound is near or far. This can lead to confusion and inconsistent depth in your mix.
If you are using only the Decca Tree signal, you do not need to worry about this. The Decca Tree has a fixed distance to all the instruments in the orchestra. So, the instruments further away from it will have all the aspects mentioned above naturally captured. A French horn at the back of the stage will have less high frequency content than the strings, which are much closer to the Decca Tree.
However, if you add some close mic signal to give the French horn more definition, you now have two conflicting perspectives of depth in your mix. One from the Decca tree, telling your ears that the French horn is far away. And one from the spot mic, which tells you that the French horn is close. To increase the sense of depth, try narrowing the stereo field of the close mic and EQing out some of the high frequency content. I would not add too much reverb to the close mic, as this would defeat the purpose of adding clarity and definition. But keep an ear out for how much close mic you can add before it starts to confuse the sense of depth. Add just enough to add clarity without overpowering the sense of depth. Finding this balance is your job as the mixing engineer. Blending in close mic signal will always bring the instrument or section closer.
Blending in close mic signal
As described above, if you need to use close mics, add just enough to get the detail and punch you want, while still maintaining a sense of depth. Be aware that often the close mics are not needed at all, or only at certain points in the track. If you do need the close mics, it is perfectly fine to automate their level subtly throughout the track. If an instrument has a solo, bring the close mics up for it if necessary, and then fade them down again. Avoid sudden large changes in gain. If you raise the close mic by 6db all at once, the instrument will suddenly sound much closer. This sounds unnatural. Instead, increase the signal slowly so that you have the amount you need at the start of the solo. If you can hear a close mic as such in your mix, the close mic level is too high. Bring it down.
Panning the close mics
Close mic signals are not naturally panned. The microphone is placed in front of the instrument, about 1m to 1.5m away. The resulting sound will naturally be centred. To compensate for this, you need to pan the close mic signal. People often start by panning according to an orchestra seating plan. This is a sure-fire way of blurring the positioning of your instruments. Do this instead:
Listen to where your instrument is placed in your main mic signal (for example, the Decca tree). Slowly bring in some of the close mic signal. You will hear the image move towards the centre, as the close mic signal is not panned. Now pan the close mic signal towards the position in your main mic. Bring down the close mic signal. Slowly raise it up again. Does the image still move towards the center? Pan more. Does it move away from center instead? Dial back the panning. Repeat these steps until you don't hear any movement in the instrument position when you raise the close mic signal. Your close mic is now panned correctly for this mix.
This is quick and easy on a mixing console where you have one hand on the fader and the other on the panpot. With a mouse, it takes a little longer because you can only change one parameter at a time. But the results are the same.
Note how the correct panning can change depending on what your main microphone signal is. If your main signal is the Decca Tree you will need different panning than if it is the Outriggers. Using an orchestra seating chart will lead you to believe that one panning is correct for every situation in every mix. This will lead to fuzzy positioning and unfocused sound. Instead, use your ears and the method above to maintain the natural positioning of your main mic signal.
On to the next stages
If you have gone through all these steps, you have decided on the main mic signal for your track. You have decided if you need any extra mics (Outriggers/Wide/Sides to add width, Hall/Room/Ambient to add spaciousness). And you have decided if and where to use the close mics. Your close mics will be panned correctly if required.
From here, you can proceed to the other steps of mixing, such as volume automation, adding reverb, EQ, compression, etc.
What is your workflow regarding microphone positions? Any corrections, additions, other tips and tricks?
Also, I am approaching this through the lens of classical music, the sound of an orchestra playing in a concert hall. So it's different from what most people on this forum probably do. For other genres, such as film music, some mixing techniques will be the same. Others will be different. Perhaps [USER=11252]@NoamL[/USER] can shed some light on this. I don't know anything about recording film music, so I'm not the right person to ask.
Please bear all this in mind.
Recommended reading: ‘Classical Recording: A Practical Guide in the Decca Tradition’ by Caroline Haigh
Ann-Kathrin Dern has a good short explanation on her channel:
Getting started – one library, many mic positions
You may have been in the position of loading a sample library and being faced with an overwhelming choice of mic positions. Spitfire Audio's BBC Symphony Orchestra comes with what, 20 signals? What do we do with them? Should you use them all in your mix? God, no. No, no, no, no! If you use 20 mic signals all at once in your mix, you will get unintelligible garble. A Walla Group of orchestral mixing. So, what should you do instead? In many cases, just using your main mic signal will do the trick.
Selecting your main mic signal for the mix
Sample libraries often come with one or more ready-made mixes. Your first action can always be to try them out. If it works for your track, use it. But if they are not what you are looking for, then you need to create your own. You can do this as follows:
Often a Decca Tree is the main mic signal for a classical orchestral recording. Sometimes outriggers are added to increase the width of the sound. It's not wrong, but unusual, to use two or more stereo arrays in the same mix. If you have several stereo arrays in your library - Decca Tree, ORTF, Spaced Omnis - you will usually choose the most appropriate one for your track. This stereo array will be the only signal for your mix, or at least be the loudest one. You can add outriggers or side microphones if you need more width, and/or some room microphones (often called ‘hall’, ‘ambient’, ‘room’ or similar) for a more reverberant and spacious sound.
A common mistake is to mix in the close mic signals to all your instruments at all times. This is usually not necessary and can destroy the impression of natural depth. Why are you mixing in the close mics? Just because they are in your sample library? Turn them off. Because your mix sounds too wet or blurred? Turn down the level of your room mics instead. Try using your main mic signal without any other mics mixed in. Only if your main mic signal sounds too reverberant and undefined on its own should you consider adding some of the close mic signal. However, this is usually a sign that you have chosen the wrong sample library for your track and should use a drier one instead. The close mics are meant to accentuate specific instruments for specific phrases. They are not meant to be a constant part of the mix for all your instruments. The exception to this is brass and perhaps percussion. If the brass section does not sound clear and defined enough from your main mic signal alone, add some close mic signal. But be aware that often this isn't necessary at all.
Orchestral depth
The perception of distance is based on a combination of factors:
1. The further away a sound is, the more the high frequencies are attenuated. Bow noise, key noise, transients - all of these are reduced with distance.
2. More reverberant sound. More reverberation and less direct signal we interpret as a distant sound.
3. Stereo width. The further away an instrument is, the narrower the stereo width. When a large instrument occupies only a small part of the stereo field, we interpret this as distant. Conversely, if a small instrument occupies a large part of the stereo field, we interpret it as near.
All these aspects should work together in your mix. This will give you a sense of real depth. If they work against each other, you will not get a sense of depth. For example, if a sound source has little direct signal and a lot of reverb, but also a lot of high frequency content and a wide stereo signal, we can't interpret whether the sound is near or far. This can lead to confusion and inconsistent depth in your mix.
If you are using only the Decca Tree signal, you do not need to worry about this. The Decca Tree has a fixed distance to all the instruments in the orchestra. So, the instruments further away from it will have all the aspects mentioned above naturally captured. A French horn at the back of the stage will have less high frequency content than the strings, which are much closer to the Decca Tree.
However, if you add some close mic signal to give the French horn more definition, you now have two conflicting perspectives of depth in your mix. One from the Decca tree, telling your ears that the French horn is far away. And one from the spot mic, which tells you that the French horn is close. To increase the sense of depth, try narrowing the stereo field of the close mic and EQing out some of the high frequency content. I would not add too much reverb to the close mic, as this would defeat the purpose of adding clarity and definition. But keep an ear out for how much close mic you can add before it starts to confuse the sense of depth. Add just enough to add clarity without overpowering the sense of depth. Finding this balance is your job as the mixing engineer. Blending in close mic signal will always bring the instrument or section closer.
Blending in close mic signal
As described above, if you need to use close mics, add just enough to get the detail and punch you want, while still maintaining a sense of depth. Be aware that often the close mics are not needed at all, or only at certain points in the track. If you do need the close mics, it is perfectly fine to automate their level subtly throughout the track. If an instrument has a solo, bring the close mics up for it if necessary, and then fade them down again. Avoid sudden large changes in gain. If you raise the close mic by 6db all at once, the instrument will suddenly sound much closer. This sounds unnatural. Instead, increase the signal slowly so that you have the amount you need at the start of the solo. If you can hear a close mic as such in your mix, the close mic level is too high. Bring it down.
Panning the close mics
Close mic signals are not naturally panned. The microphone is placed in front of the instrument, about 1m to 1.5m away. The resulting sound will naturally be centred. To compensate for this, you need to pan the close mic signal. People often start by panning according to an orchestra seating plan. This is a sure-fire way of blurring the positioning of your instruments. Do this instead:
Listen to where your instrument is placed in your main mic signal (for example, the Decca tree). Slowly bring in some of the close mic signal. You will hear the image move towards the centre, as the close mic signal is not panned. Now pan the close mic signal towards the position in your main mic. Bring down the close mic signal. Slowly raise it up again. Does the image still move towards the center? Pan more. Does it move away from center instead? Dial back the panning. Repeat these steps until you don't hear any movement in the instrument position when you raise the close mic signal. Your close mic is now panned correctly for this mix.
This is quick and easy on a mixing console where you have one hand on the fader and the other on the panpot. With a mouse, it takes a little longer because you can only change one parameter at a time. But the results are the same.
Note how the correct panning can change depending on what your main microphone signal is. If your main signal is the Decca Tree you will need different panning than if it is the Outriggers. Using an orchestra seating chart will lead you to believe that one panning is correct for every situation in every mix. This will lead to fuzzy positioning and unfocused sound. Instead, use your ears and the method above to maintain the natural positioning of your main mic signal.
On to the next stages
If you have gone through all these steps, you have decided on the main mic signal for your track. You have decided if you need any extra mics (Outriggers/Wide/Sides to add width, Hall/Room/Ambient to add spaciousness). And you have decided if and where to use the close mics. Your close mics will be panned correctly if required.
From here, you can proceed to the other steps of mixing, such as volume automation, adding reverb, EQ, compression, etc.
What is your workflow regarding microphone positions? Any corrections, additions, other tips and tricks?
!!!