Topic: Panning question

[percoplus]

With a stereo pair in any configuration, do you typically pan the mics 100% or only part of the way? For example, my mics are 90 degrees apart pointing towards a stage. If I pan the left mic 100% left and the right mic 100% to the right, it seems to me I would only be getting sound from the side walls and nothing from the front stage area. Sorry if this is a dumb question, I have been all over this forum and not found one reference to panning.

[JasonSobel]

yes, in a typical stereo recorder, there is no need to "pan", because the left mic goes to the left channel, and the right mic to the right channel.  However, if recording a stereo pair of mics as two mono channels, they should be 100% panned (so that the left channel is only the left mic, and the right channel is only the right mic).  By the very nature of microphone pick-up patterns, the right mic will have some overlap of the audio information that the left mic also records (and vice-versa).  How much overlap of signal between the two mics is controlled by mic pattern (cardioid, hypercardioid, omni, etc, etc...), the spacing between the capsules, and the angle of the capsules.  But there should be no need to pan each channel partially (so that some of the left mic goes to the right channel, and vice verse).

[newplanet7]

In a configuration like din, ortf, nos, etc the mics will not be pointed towards the stage.
Don't picture a microphone like a flashlight. It's not picking up a direct line where it is pointed.
Picture the capsule pick-up pattern and and where it faces in 3-d.
 The two capsules will overlap and the capsules polar pattern be it, card, hyper, omni, subcard) 
will pick up the center of the angle.

Here are some of the different capsule polar patterns



3-d of cardioid pattern

[percoplus]

Thank you. A related question: when you pan hard left or right, are you then getting only one side of the cardioid pattern? In other words, are you losing information?

[JasonSobel]

Thank you. A related question: when you pan hard left or right, are you then getting only one side of the cardioid pattern? In other words, are you losing information?

no.  there is no way to separate just "one side" or a cardioid pattern from the mic signal.  When you pan a mono mic signal all the way to the left or the right, you are sending 100% of the entire signal to either just the left or just the right channel.

[percoplus]

Good. Thanks again, friend

[newplanet7]

The mic capsule will be picking up sound from all around the sides so nothing is lost

Here's a great pdf from DPA that shows quite a few stereo recording techniques that tapers use.
It shows the captured angles and cap spacing in each stereo technique.
http://www.dpamicrophones.com/en/~/media/PDF/Download/stereo.pdf

EDIT:
Not sure why but the pdf opens to page 11.
There are other stereo configurations before and after that.

[percoplus]

Yeah, I read that. The whole thing makes little sense to me. If you have two mics pointed away from each other 110 degrees, then how is the sound directly in front being picked up? Seems like you're pointed at the side walls and not the stage. And does a few centimeters between the mics really make that much difference? Guess I have to read these things over and over until I get it.

And this MicConfig tempate REALLY makes no sense.

[SmokinJoe]

There can be a lot of high level math and physics used to explain this, but let's try to keep it simple.

First the spacing.... 17-20 centimeters is about the width of the head between your ears.   Because sound travels at "the speed of sound" there are slight timing delays when the sound hits the mics, and because it's the same separation as your ears it  "sounds normal" when wearing headphones, like you were there.  It's all "psycho-acoustics".

Now the direction...  If you point  the mics straight ahead, they both pick up the same thing.  For lack of a better term, I'll say "that's boring".  Your right ear hears better on the right, and your left ear on the left, so point the mics that way to some extent.  Make sense?

Now a little bit of science... if you look at the cardioid polar plot,  think of that plot as a "really wide flashlight  beam".  You can see that "directional" mics pick more ahead than they do to the rear, but they pick up a lot to the sides too.  At 90 degrees the "pulling power" drops about 3db, which is some, but not a lot.   So the right mic pointed towards the right PA stack will grab "all of" the right stack, and "about half' of the left PA stack.  So this gives you a little channel separation, but it's not like "a narrow flash light beam" where you can completely get ONLY the right side in right mic.   There are shotgun mics which are more directional than cardioids but even  those  aren't  like  a flashlight.

Suffice it to say,  a lot of  people have tried a lot of angles and distances and these standard ones (DIN, ORTF, etc) tend to be good ones.  Most of tapes have some channel separation,  but not so much that you get a big "hole in the middle" and  have to worry about panning.

[percoplus]

I'm a videographer, so visually I'm looking straight ahead with both eyes (or 2 cameras) creates a different image than with one eye shut. The overlap creates another dimension, but has nothing to do with speed.

Now, trying to make a corrolation.  In terms of speed, it takes a bit longer for the left "stack" to reach the right ear than to the left ear, and vice-versa. The little time shift adds to the stereo effect. I think I get that. But if that's true, then why use a coincident mic placement? And shouldn't the time differential diminish as you get further from the sound source?

Now, the angle thing mystifies me. I know the ears stick out the sides of the head, not out front. But, why specifically 90 degrees or 110? Shouldn't the angle be dictated by the triangle created by the mic placement and the width of the sound source?

I think I understand that the narrower the angle between the mics the greater the stereo angle - according to the above chart. The stereo angle is the overlapped portion of the signal, correct?

What exactly is a "sweet spot"?

[SmokinJoe]

That's a lot of questions at once.

Your eyes are an extremely narrow beam compared to a microphone.  I will over simplify and say the angle that an eye can look at is about 1 degree, and a microphone is a full 180 degrees.  That width difference is why you can't draw similar analogies between eyes and ears.

Why run coincident mics?  Because you want to remove that timing element and leave only the directional element.  It's a personal choice.  I generally listen with ear buds, and I like some near-coincident timing in there.  My friend Nick has a super gee whiz stereo system in his living room, and he prefers XY.  To each his own.

As far as angles go... I'll just say that people have tried a lot of angles and 90 and 110 have stood the test of time, but people run other angles.  There is no right or wrong answer.

The "Sweet spot" is loosely "the best sounding spot in the room".  It varies by room, but typically it's dead center, and a distance from the stage where the left stack is 45* to your left, and the right stack is 45* to your right, so the included angle is 90 degrees.  Hence when you are running DIN, your mics are pointed right at the stacks.  It's not always right there, but you get the idea... dead center... not too close to the stage, and not too far from the stage.

The other thing to remember is that these standard patterns (XY, DIN, ORTF) weren't originally designed/chosen for tapers at rock concerts recording a L/R stack PA.  They were largely chosen for recording an orchestra with a stage full of unamplified instruments.  In this case, you are trying to create a balanced field with the instruments and some room reverberation.  Think of the nice old opera houses... they were designed so a person with an unamplified violin could be heard throughout the room.  That's a bit different that Phish in a room designed for playing hockey.

I suggest you go to a bar where a friendly band will let you record/experiment, and do the following.  It will be a learning experience.
- Set up a pair mics at XY and record a song.
- Change it to DIN and record a song.
- Change it to ORTF and record a song.
- Change it to NOS (12" x 90*) and record a song.
- Change it to both pointing straight ahead (AB) and record a song.
- be sure to write down what songs were recorded at which settings.
- go home and listen.
- draw your own conclusions and use what you like.

[percoplus]

Thanks for the very practical advice, Smokin Joe. That's pretty much what I have been doing, but I have to get it right before I can take a paying gig with a clear conscience.

And the explanation of a sweet spot. Unfortunately, that spot 45 degrees from each speaker is on the dance floor in most cases. Talk about a short career. Lol!

[SmokinJoe]

And the explanation of a sweet spot. Unfortunately, that spot 45 degrees from each speaker is on the dance floor in most cases. Talk about a short career. Lol!

Sometimes I can clamp to an overhead beam, or drag a table/chair out close to the sweet spot.  Not always, but usually I can figure out something.

[stevetoney]

I'm a videographer, so visually I'm looking straight ahead with both eyes (or 2 cameras) creates a different image than with one eye shut. The overlap creates another dimension, but has nothing to do with speed.

Light isn't sound.  Eyes are a similar analogy to ears, but different.  Your eyes see in dimensions because of the parallax difference created by your eyes being in two different locations.  The brain knows how to interpret the parallax to allow us to see in 3D (unless you go blind in one eye).

Your ears hear directionally because our brain understands that sound takes longer to get from one ear to the other and the fact that our ears point in opposite directions.  You can somewhat prove directionality to yourself by plugging one ear, closing your eyes and then have someone talk to you from a distance (but not while they're walking around you...make them stand stationary).  Try to figure out where they are in the room and you MIGHT get it right because of the psycho-dynamics of sound (if they're on your left and your right ear is the hearing ear, your brain will understand and interpret how this sound is more muffled therefore you'll assume through analysis that the sound is coming from the left, but not through directionality), but if the sound is direct, you won't be able to tell where they are in the room even though you can hear them through one ear.  It's totally harder to locate them if you're outside and there's no reverb soundwaves to help you diagnose where they are directionally.

So, stereo hearing allows you to directionally locate where the sound is coming from...and stereo mic'ing allows you to directionally locate where a sound source is coming from.  The incident angle and spacing influence this directionality and, if the angle and spacing are inconsistently set-up to the dimensional qualities of the taping environment (distance from the stage, spread of the speakers, etc.) the directional imaging of the sound will be shifted on the recording from reality.  That is why angles and spacing between stereo mics can matter so much. 

An important concept to realize is that the sound recorded on each of the mics themselves don't create a stereo image.  It's how our ears hear the sound and then how our brain interprets the interaction of sounds that fools our brains into telling us what directional location a sound is coming from.

Now, trying to make a corrolation.  In terms of speed, it takes a bit longer for the left "stack" to reach the right ear than to the left ear, and vice-versa. The little time shift adds to the stereo effect. I think I get that. But if that's true, then why use a coincident mic placement? And shouldn't the time differential diminish as you get further from the sound source?

Your first question has already been answered by someone else in a previous response.

The answer to the second question is that the time differential does NOT diminish the farther you get from the sound source because the distance between the mics does not diminish.  Sound travels through air at a constant speed, therefore the time it takes to travel the distance between your two ears is the same whether you're 10 feet from a stage or 100. 

What DOES diminish the farther you get from the stage is the stereo effect created by the time difference.  Obviously, as you move farther away from two sound sources, these sources move closer and closer in angular spacing relative to the mics (the angle created by the PA speakers takes up less of the angle between the mics).  Stated another way, the farther back you get, the left mic 'sees' the left PA speaker alot more towards the center of the soundfield, while the right mic 'sees' that same speaker in nearly the same place.  Conversely, the closer you get the two mics 'see' these mics in VERY different angular locations relative to each other.  From a distance, since the sound source is shoved towards the center of the soundfield, there's far less ability of the mics to create a stereo image.  Close up, since a sound source is in a very different angular location in one mic versus the other, there's a large potential for angular location of the sound source relative to the two mics.

Now, the angle thing mystifies me. I know the ears stick out the sides of the head, not out front. But, why specifically 90 degrees or 110? Shouldn't the angle be dictated by the triangle created by the mic placement and the width of the sound source?

The answer to this question depends totally on what effect you want your recording to have.  There are no rules.  The important point is to start to understand the WHAT and WHY behind stereo imaging.

You've GOT to understand the basic concepts here in order to apply them.  When we hear a recording, the stereo image is interpreted by our ears/brains by one of two principles; 1) differences in sound pressure, and 2) differences in timing.  Most of the time, both principles are affecting how we interpret the stereo image, but in order to fully understand why stereo angle and spacing matter, you have to contemplate the differences separately.  In the case of your question posed above, the reason the recording angle makes a difference is because differing angles contributes to stereo imaging due to diffs in sound pressure, but not differences in timing.  It's only when you separate the mics, that timing difference comes into play. 

So, let's elaborate on the concept of difference in sound pressure.  If one mic is pointed to the right and the other is pointed 90 degrees away towards the left, it stands to reason that one mic will 'hear' a sound coming from one side with greater volume than the other.  This volume difference is the difference in sound pressure we're talking about.  If you could only hear the sound through one mic, there's no way to directionally locate where the sound is coming from.  So, with two mics, the volume difference allows our brain to interpret the same sound to give us a sense of directionality...STEREO!

As you increase and decrease the incident angle of the mics, you're altering the dynamics of the relationship of direct (from the front of the mic) to reverberant (from the side of the mic) sound. 

What exactly is a "sweet spot"?

I define the sweet spot simply as the best sounding spot in a room. 

Next show you go to.  If you can, walk around the room and pay attention to how the sound changes...particularly as you move forward or back.  Pay attention also to the tonal balance between bass and treble tones.  It's not always intuitive to locate the sweet spot in a venue and it can oftentimes change as a function of the volume level.  If you've never paid attention to this, I think you'll be surprised how much the sound can change as you walk around a room...not just the obvious (you can hear L better on the L side of the room) but in terms of overall clarity of the source.  It's not always best to be close to the stage either.  There are TONS of venue's where I've found the sound WAY better back by the soundboard.  This could be because of the way the sound engineer is mixing or it could just be room dynamics.  Obviously, the goal for the audio people in the audience is to find and record from the sweet spot.

[Chuck]

Unfortunately, that spot 45 degrees from each speaker is on the dance floor in most cases. Talk about a short career. Lol!

Yeah, don't let that fact stop you.
If you are determined, you can often overcome that problem. Maybe you can wear the microphones on your body and just stand there. Maybe you could mount the mics in the ceiling. Maybe you could put up a mic stand and have guard it so that it doesn't get hit... I find that figuring stuff like that out is part of the fun of recording.