A SongCatcher in the Wild - Natural Aural Imagery
- Thread starter mfrench
- Start date
mfrench
Senior Member
That is an extensive array over a true American treasure (not pulling nationalistic pride - but they are american made).
It is over and in front of these guys:
This is The Hutchins Consort
This is an octet of harmonically voice matched violins that cover the entire frequency spectrum of written music, going inaudible at either end of the scale. And is the first ever successful attempt to cover the entire musical spectrum with violins in the history of violin making.
The mic stands in the image are part of the ones in the original post.
The round discs are room tuning for the hall.
In the above image, are:
~ A wide spaced pair of omnidirectional mics at the far left and right top corners of the image. (wide spaced omni stereo)
In the center grouping are:
Another wide spaced omnidirectional pair (spaced omni stereo)
A sub-cardioid directional pair flanking the center (ORTF stereo)
A stereo ribbon mic in the center (mid-side stereo)
So, what we're looking at is 8 microphones that are set up for four, two channel stereo recordings.
It is over and in front of these guys:
This is The Hutchins Consort
This is an octet of harmonically voice matched violins that cover the entire frequency spectrum of written music, going inaudible at either end of the scale. And is the first ever successful attempt to cover the entire musical spectrum with violins in the history of violin making.
The mic stands in the image are part of the ones in the original post.
The round discs are room tuning for the hall.
In the above image, are:
~ A wide spaced pair of omnidirectional mics at the far left and right top corners of the image. (wide spaced omni stereo)
In the center grouping are:
Another wide spaced omnidirectional pair (spaced omni stereo)
A sub-cardioid directional pair flanking the center (ORTF stereo)
A stereo ribbon mic in the center (mid-side stereo)
So, what we're looking at is 8 microphones that are set up for four, two channel stereo recordings.
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mfrench
Senior Member
My world rotates around the bottom three; Omnidirectional, hypocardioid (sub-cardioid), and cardioid; and the top, Figure-of-eight.
Microphones come in two types:
Pressure gradient, and pressure transducer.
Pressure gradient mics are the ones that are directional, and the pressure transducer is the omnidirectional mic.
What does that mean?
To create directionality in a microphone, engineers introduce venting to the backside of the microphone capsule, through the backplate of the microphones diaphragm, in varying amounts. This venting exposes the rear of the mic capsule to the same influences that are effecting the face surface. This difference in pressure is what we refer to as the gradient.
The pressure gradient mic reacts by having the rear of the capsule being effected by similar impulses as the front of the capsule. These shared common influence create phasing anomalies that cancel out rearward influences, creating the directionality of the mic.
The Pressuse Transducer, omnidirectional microphone does not have this gradient venting, and only is influenced by impulse to the face of the capsule. This allows the polar response pattern of a near perfect orb.
Microphones come in two types:
Pressure gradient, and pressure transducer.
Pressure gradient mics are the ones that are directional, and the pressure transducer is the omnidirectional mic.
What does that mean?
To create directionality in a microphone, engineers introduce venting to the backside of the microphone capsule, through the backplate of the microphones diaphragm, in varying amounts. This venting exposes the rear of the mic capsule to the same influences that are effecting the face surface. This difference in pressure is what we refer to as the gradient.
The pressure gradient mic reacts by having the rear of the capsule being effected by similar impulses as the front of the capsule. These shared common influence create phasing anomalies that cancel out rearward influences, creating the directionality of the mic.
The Pressuse Transducer, omnidirectional microphone does not have this gradient venting, and only is influenced by impulse to the face of the capsule. This allows the polar response pattern of a near perfect orb.
mfrench
Senior Member
Directional microphones exhibit the Proximity Effect.
What is that?
Proximity Effect in a microphone is analogous to the standing bass wave in playback. It is a distortion of the microphone capsule, that, to shorten words, is a standing bass wave that forms on the mic capsule. It heavily emphasizes certain regions of bass, and is not a pleasant experience.
Because of Proximity Effect, all directional microphones, pressure gradient mics, will roll-off bass response by their very design.
Omnidirectional mics, pressure transducers, do not exhibit Proximity Effect, and, do not roll-off the bass.
What is that?
Proximity Effect in a microphone is analogous to the standing bass wave in playback. It is a distortion of the microphone capsule, that, to shorten words, is a standing bass wave that forms on the mic capsule. It heavily emphasizes certain regions of bass, and is not a pleasant experience.
Because of Proximity Effect, all directional microphones, pressure gradient mics, will roll-off bass response by their very design.
Omnidirectional mics, pressure transducers, do not exhibit Proximity Effect, and, do not roll-off the bass.
mfrench
Senior Member
Now lets look at the polar response patterns in a two dimensional view, as viewed from above:
Omnidirectional:
Cardioid:
Figure-of-Eight:
In this image, you are looking down onto the microphone, from above.
In it, you're assuming that the microphone capsule is directly in line with the crosshairs (or where they would be crossing).
When a microphone is pointed straight forward at the source, it is said to be at 0º of off-axis response.
Pointed straight forward, you get all of the signal impulses offered, without any form of attenuation.
This is the basic starting point for polar response graphs. The one above would very well represent the polar response of an omnidirectional mic; though it is actually not showing anything, its just representing the basic graph.
overview of some of the multiple patterns:
The main thing to think about in this image, ^^, is A: directionality at the capsule, and B) the less round the response, the less bass that you're going to be capturing.
Omnidirectional:
Cardioid:
Figure-of-Eight:
In this image, you are looking down onto the microphone, from above.
In it, you're assuming that the microphone capsule is directly in line with the crosshairs (or where they would be crossing).
When a microphone is pointed straight forward at the source, it is said to be at 0º of off-axis response.
Pointed straight forward, you get all of the signal impulses offered, without any form of attenuation.
This is the basic starting point for polar response graphs. The one above would very well represent the polar response of an omnidirectional mic; though it is actually not showing anything, its just representing the basic graph.
overview of some of the multiple patterns:
The main thing to think about in this image, ^^, is A: directionality at the capsule, and B) the less round the response, the less bass that you're going to be capturing.
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mfrench
Senior Member
sub-cardioid response (look at the polar pattern, not the Freq. Chart):
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~
hyper-cardioid response:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Figure-of-Eight, or, Bi-Directional response:
wire:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~
hyper-cardioid response:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Figure-of-Eight, or, Bi-Directional response:
wire:
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mfrench
Senior Member
The above images are just the basic polar response "shapes". The graphs lines, when viewed from a closer look, reveal what looks like topographical contouring lines.
As example, these are the frequency response curves that I'm referring to. All microphone exhibit this breakdown of frequency response when "viewed with a closer look".
The bending/wavering of the rings/lines is frequency bending, or shaping.
As example, these are the frequency response curves that I'm referring to. All microphone exhibit this breakdown of frequency response when "viewed with a closer look".
The bending/wavering of the rings/lines is frequency bending, or shaping.
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mfrench
Senior Member
Microphones come in multiple varieties, regarding quality.
When you get into the realm of recording and studio work, you have mics that can be utilized as hammers, and others that you hold your breath around, and handle with the softest touch.
These softest touch microphones are a bit akin to pure breds. We refer to this class as microphones of the First Order.
This doesn't necessarily make them weak; these are your pure breds.
Microphones of the First Order have to exhibit the ability to be able to be turned off-axis by as far as 55 degrees, and still retain 100% perfect frequency response, with the only affect being that of attenuation of the impulses amplitude; in other words, perfect freq response, just not as loud.
Turned 55 degrees off-axis with full frequency response, with only an attenuation value of 6dB at that mark.
6dB is a lot in the wild.
So - First Order can be turned 55º with no freq.. altering only amplitude, w/ difference of 6dB
Any other microphone out of this class, especially one of unknown heritage (off-axis freq. response), you don't know how far you can turn them off-axis. This limits you to 45º of off-axis response with lesser microphones (to be safe).
look to the graphs above, and find 45 and 55 degrees - they are literally suggesting that off-axis response.
When you get into the realm of recording and studio work, you have mics that can be utilized as hammers, and others that you hold your breath around, and handle with the softest touch.
These softest touch microphones are a bit akin to pure breds. We refer to this class as microphones of the First Order.
This doesn't necessarily make them weak; these are your pure breds.
Microphones of the First Order have to exhibit the ability to be able to be turned off-axis by as far as 55 degrees, and still retain 100% perfect frequency response, with the only affect being that of attenuation of the impulses amplitude; in other words, perfect freq response, just not as loud.
Turned 55 degrees off-axis with full frequency response, with only an attenuation value of 6dB at that mark.
6dB is a lot in the wild.
So - First Order can be turned 55º with no freq.. altering only amplitude, w/ difference of 6dB
Any other microphone out of this class, especially one of unknown heritage (off-axis freq. response), you don't know how far you can turn them off-axis. This limits you to 45º of off-axis response with lesser microphones (to be safe).
look to the graphs above, and find 45 and 55 degrees - they are literally suggesting that off-axis response.
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What a great thread! I gotta sit down tonight and really go through it. I had no clue there were so many microphone options, or what was involved in getting the best out of them!
mfrench
Senior Member
All of the above has been about the response characteristic of a single microphone.
A single mic is fine, if you have a single object directly in front of it, or, off-axis to it, as suggested above.
Examples of off-axis response, is a guitarists that turns his microphone slightly sideways to his cabinet, because he likes whatever that turning off-axis did to the sound.
Now, if you have a duet for example, and you want to capture a natural aural image. Or, if you have an orchestra, and a wide aural image that is presented to you. How do you cover that with a single mic?
You can go far back into what we call the diffuse field environment, this is the wilds; Or, you can try to broaden your mics response by choosing a less directional pattern.
Or, you can introduce a second microphone.
Two microphones can be used to create a wide monaural image.
A single mic is fine, if you have a single object directly in front of it, or, off-axis to it, as suggested above.
Examples of off-axis response, is a guitarists that turns his microphone slightly sideways to his cabinet, because he likes whatever that turning off-axis did to the sound.
Now, if you have a duet for example, and you want to capture a natural aural image. Or, if you have an orchestra, and a wide aural image that is presented to you. How do you cover that with a single mic?
You can go far back into what we call the diffuse field environment, this is the wilds; Or, you can try to broaden your mics response by choosing a less directional pattern.
Or, you can introduce a second microphone.
Two microphones can be used to create a wide monaural image.
I've learned quite a lot about recording through this thread. It's funny, we will talk about how important the quality of the rcording is but most of us have no idea what goes into making one.
How is a "typical" studio recording mic'd?
How is a "typical" studio recording mic'd?
mfrench
Senior Member
Any luck with the capturing of the duet with a single mic?
You probably can, but, you're seriously dealing with the off-axis response characteristic of the mic.
If your duet is at 10 and 2 on the clock, with 12-o'clock being straight forward, you are at the boundary edges of what a single directional microphone can handle. Its because the image presented to that single microphone exceeds its design limits, and you're entering into frequency bending, and severe amplitude attenuation, due to its off-axis response, or, rejection.
This is where we were saved by an audio deity, from many decades back; Alan Dower Blumlein.
He was faced with this very situation.
OK,.... folks, if you thought that we were dealing in the abstract to this point, get ready, because it only gets far more weird from here.
Hint: terms like variable phase alignments, phase cancellations, phase. All the nasty P's
You probably can, but, you're seriously dealing with the off-axis response characteristic of the mic.
If your duet is at 10 and 2 on the clock, with 12-o'clock being straight forward, you are at the boundary edges of what a single directional microphone can handle. Its because the image presented to that single microphone exceeds its design limits, and you're entering into frequency bending, and severe amplitude attenuation, due to its off-axis response, or, rejection.
This is where we were saved by an audio deity, from many decades back; Alan Dower Blumlein.
He was faced with this very situation.
OK,.... folks, if you thought that we were dealing in the abstract to this point, get ready, because it only gets far more weird from here.
Hint: terms like variable phase alignments, phase cancellations, phase. All the nasty P's
mfrench
Senior Member
Alan Dower Blumlein was an electronic engineer, who worked in the world of audio and audio recording. He passed from this realm in WWII, but his contributions are immense.
Blumlein was faced with capturing a broad aural image, that of an orchestra. He did so with two microphones. He created a technique that we refer to as a Coincidental Array.
A coincidental array has two microphone capsules in direct vertical alignment over each other.
Now a coincidental microphone array that has both microphones pointed straight forward does not help with the duet, or a wider scenario. It creates a monaural image with two microphones that are sharing 100% of both timing cues, and, amplitude cues. Both mics are exposed to the exact same influence, at exactly the same moment of time (coincidentally timed), and at the exact same amplitude. This is is an absolute phase alignment of all the impulse variables. When mixed together, all of this information is sent into the electronic stream, and in the end there is a natural summation of all of the balanced signal_+'s, and signal_-'s This is perfect phase alignment, and true balance. But it produces a summed mono signal, with the pinched forward view of O-degrees of combined_off-axis response.
New term -> Combined off-axis response
IMPORTANT.
This is what we call two microphones in angular relation to each other. If both are vertically aligned and pointed straight forward, we have 0-degrees of combined off-axis response.
Now, with a first order microphone, we can turn that microphone outwardly to 55-degrees.
What Blumelin presented us with is two microphones in vertical alignment, and, he turned one capsule to the right by 45-degrees, and the other capsule to the left- by 45-degrees.
This gives us a combined off-axis response of what we refer to as 90-degrees of combined off-axis response.
In Blumleins day, they had available to them; Figures-of-8, omnidirectional, and cardioid microphone polar response patterns.
With these pattern, he presented us with a technique that looks like a perpendicular X, with the X points being lobes, more like a clover-leaf (and squarely perpendicular to each other). When this is done with a pair of vertically aligned Figures-of-8, we call this Blumlein.
This is what Blumlein looks like, viewed from above:
Now, what you're looking at here is the clover-leaf. At the points where the lobes overlap, we get summations of variable phasing. This creates minute phase alignments and cancellations within the processing of the signal (natural filtration processes, the physics of acoustics). These phase alignments create ghosting images in the areas, the null points, between the lobes. These ghosting images are presented as if there were a third microphone in that region; one that receives all of the frequency response of both microphones, and is also receiving an attenuated amount of centered amplitude.
These ghosting images are only there due to the natural phase alignment assignment of the natural filtration processes; those of timing and amplitude cues.
In terms of phase alignment, they are so severe in Fig-of-8 Blumelin, that the rear of the right capsule is capturing the left rear field image, and, vice versa.
What does that mean?
As a recordist, if you have, for example, a noisy audience member behind you to your left, in playback, he is going to completely change side by 90-degrees, and you will hear him in the right channel in playback.
These rear lobes of Blumlein give you the cues of just how large/small, or, how reverberant the hall is. The rear lobes capture 100% of what is going on behind the mic array, in reverse phase.
Problem: pinched off bass. It carries the bottom of a string bass, in a rolled-off fashion.
Blumlein was faced with capturing a broad aural image, that of an orchestra. He did so with two microphones. He created a technique that we refer to as a Coincidental Array.
A coincidental array has two microphone capsules in direct vertical alignment over each other.
Now a coincidental microphone array that has both microphones pointed straight forward does not help with the duet, or a wider scenario. It creates a monaural image with two microphones that are sharing 100% of both timing cues, and, amplitude cues. Both mics are exposed to the exact same influence, at exactly the same moment of time (coincidentally timed), and at the exact same amplitude. This is is an absolute phase alignment of all the impulse variables. When mixed together, all of this information is sent into the electronic stream, and in the end there is a natural summation of all of the balanced signal_+'s, and signal_-'s This is perfect phase alignment, and true balance. But it produces a summed mono signal, with the pinched forward view of O-degrees of combined_off-axis response.
New term -> Combined off-axis response
IMPORTANT.
This is what we call two microphones in angular relation to each other. If both are vertically aligned and pointed straight forward, we have 0-degrees of combined off-axis response.
Now, with a first order microphone, we can turn that microphone outwardly to 55-degrees.
What Blumelin presented us with is two microphones in vertical alignment, and, he turned one capsule to the right by 45-degrees, and the other capsule to the left- by 45-degrees.
This gives us a combined off-axis response of what we refer to as 90-degrees of combined off-axis response.
In Blumleins day, they had available to them; Figures-of-8, omnidirectional, and cardioid microphone polar response patterns.
With these pattern, he presented us with a technique that looks like a perpendicular X, with the X points being lobes, more like a clover-leaf (and squarely perpendicular to each other). When this is done with a pair of vertically aligned Figures-of-8, we call this Blumlein.
This is what Blumlein looks like, viewed from above:
Now, what you're looking at here is the clover-leaf. At the points where the lobes overlap, we get summations of variable phasing. This creates minute phase alignments and cancellations within the processing of the signal (natural filtration processes, the physics of acoustics). These phase alignments create ghosting images in the areas, the null points, between the lobes. These ghosting images are presented as if there were a third microphone in that region; one that receives all of the frequency response of both microphones, and is also receiving an attenuated amount of centered amplitude.
These ghosting images are only there due to the natural phase alignment assignment of the natural filtration processes; those of timing and amplitude cues.
In terms of phase alignment, they are so severe in Fig-of-8 Blumelin, that the rear of the right capsule is capturing the left rear field image, and, vice versa.
What does that mean?
As a recordist, if you have, for example, a noisy audience member behind you to your left, in playback, he is going to completely change side by 90-degrees, and you will hear him in the right channel in playback.
These rear lobes of Blumlein give you the cues of just how large/small, or, how reverberant the hall is. The rear lobes capture 100% of what is going on behind the mic array, in reverse phase.
Problem: pinched off bass. It carries the bottom of a string bass, in a rolled-off fashion.
mfrench
Senior Member
Now, in Blumleins day, he took this Coincidental Array, and he would mix it to mono. Today, we utilize it in full stereo glory, that can be mixed to mono.
Coincidental arrays only share amplitude differences. They do not share any timing differences due to the vertical alignment, and the instantaneous, coincidentally arrived signal impulse.
Of the two largest effects of live music audio recording, timing and amplitude, timing is eliminated from the sequence. This allows for the coincidentally timed array to be mixed to mono.
A.D. Blumlein also gave us two more coincidentally timed arrays that he would mix to monaural: XY, and Mid-Side.
All are utilized today to create stereo recordings that can be mixed to mono.
XY is quite similar to Figs-of-8 Blumlein, without the rearward lobes.
XY is done with the heart shaped cardioids, and is the two capsules in vertical alignment, and angled outwardly by 45-degrees each. This is very similar to a V, but at 90-degree combined-response.
This gives the recordist a 90-degree forward look across the ensemble, and it creates a wonderful floating ghosting center image.
Cardioid XY:
Now, you can see the combined response region, as the created small lobe in the null region at 0-degree. That is the ghost center image region. That area that is created without the third 0-degree microphone to represent it. This is the magic of true two channel recording; its very essence.
A.D. Blumlein would take this two mic array and mix it to mono.
Coincidental arrays only share amplitude differences. They do not share any timing differences due to the vertical alignment, and the instantaneous, coincidentally arrived signal impulse.
Of the two largest effects of live music audio recording, timing and amplitude, timing is eliminated from the sequence. This allows for the coincidentally timed array to be mixed to mono.
A.D. Blumlein also gave us two more coincidentally timed arrays that he would mix to monaural: XY, and Mid-Side.
All are utilized today to create stereo recordings that can be mixed to mono.
XY is quite similar to Figs-of-8 Blumlein, without the rearward lobes.
XY is done with the heart shaped cardioids, and is the two capsules in vertical alignment, and angled outwardly by 45-degrees each. This is very similar to a V, but at 90-degree combined-response.
This gives the recordist a 90-degree forward look across the ensemble, and it creates a wonderful floating ghosting center image.
Cardioid XY:
Now, you can see the combined response region, as the created small lobe in the null region at 0-degree. That is the ghost center image region. That area that is created without the third 0-degree microphone to represent it. This is the magic of true two channel recording; its very essence.
A.D. Blumlein would take this two mic array and mix it to mono.
mfrench
Senior Member
The final of the early two channel techniques is mid-side.
Again, vertically aligned capsules, as with the other two coincidental techniques.
In the image below, the horizontal mic would be pointed forward 0-degrees, at the source.
In this image, you are viewing the stereo array from the side.
Mid-side has variants. One being a cardioid mic and a figure-of-eight. The other being a pair of figures-of-eight.
The above image with the cardioid, could very well have the fig-8 mic take its place. The capture is different, but, ultimately, the technique is the same.
With all of that said, I'm not so big on this technique, as it requires post-editing to be correctly decoded. Yes, it requires a decoding, if you really want to milk it for everything that you can. It can also be done on the fly, but, with wildly variable results.
This one is a mashup of phasing assignments.
The mid mic is looking straight forward, and is presented 100% in the mix (unless you choose to use less; typically 100%)
The side mic is the variable, and is what assigns the phase alignments. The more you bring that into the mix, the wider you image will spread. The less that you use, the deeper the reach will be.
This is an extremely generalized explanation, but covers the basics.
I don't like processing, therefore, this one is not used very often; but purely for personal reasons. Its a great technique.
Up next,.... the world moves towards stereo gear in the home, and stereo recording in the wild.
We also introduce the timing variable, and near-coincidental techniques. This is pure stereo recording in the wild.
No chance to fall back on mono.
Phase alignments go crazy.
Again, vertically aligned capsules, as with the other two coincidental techniques.
In the image below, the horizontal mic would be pointed forward 0-degrees, at the source.
In this image, you are viewing the stereo array from the side.
Mid-side has variants. One being a cardioid mic and a figure-of-eight. The other being a pair of figures-of-eight.
The above image with the cardioid, could very well have the fig-8 mic take its place. The capture is different, but, ultimately, the technique is the same.
With all of that said, I'm not so big on this technique, as it requires post-editing to be correctly decoded. Yes, it requires a decoding, if you really want to milk it for everything that you can. It can also be done on the fly, but, with wildly variable results.
This one is a mashup of phasing assignments.
The mid mic is looking straight forward, and is presented 100% in the mix (unless you choose to use less; typically 100%)
The side mic is the variable, and is what assigns the phase alignments. The more you bring that into the mix, the wider you image will spread. The less that you use, the deeper the reach will be.
This is an extremely generalized explanation, but covers the basics.
I don't like processing, therefore, this one is not used very often; but purely for personal reasons. Its a great technique.
Up next,.... the world moves towards stereo gear in the home, and stereo recording in the wild.
We also introduce the timing variable, and near-coincidental techniques. This is pure stereo recording in the wild.
No chance to fall back on mono.
Phase alignments go crazy.
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