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M/S in Protools session - 2 track or 3 track ?
Old 23rd November 2009
  #1
Gear Head
 

M/S in Protools session - 2 track or 3 track ?

Hello all,

I am finishing editing sound for a short film, I some ambience tracks I have recorded with the M/S technique and now I want to import them into my editing session. I see two possibilities:

1. to have one stereo track, two regions and M/S decoding plug-in as insert (potential problem of not having that plug-in in other studios)

2. to have three mono tracks and decode it by inverting phase (thus a heavier session, need to create groups to control levels, manually adjusting the -6 dB difference and pan settings on ALL Side tracks)

Does anyone have any experience with this situation ? Is the mono-compatibility of M/S lost when I de-codify it into 2 track stereo? Am I missing something here ?

Thanks
Old 23rd November 2009
  #2
Gear Nut
 
dsteinwedel's Avatar
 

No, you're doing it right. Just have to decide which method is better for you at the moment. (Also, you do not need to stick with a -6db move on the side tracks, you can adjust their volume to widen/narrow the image to taste.)

-Dave
Old 23rd November 2009
  #3
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danijel's Avatar
Quote:
Originally Posted by gato sapato View Post
Is the mono-compatibility of M/S lost when I de-codify it into 2 track stereo?
Haha, one day I will put it in my sig that MS is NOT mono compatible....
.......I just did it

Anyway, MS can be decoded to LR, and than encoded back to MS, if that's what you're asking. Nothing is lost.
Old 24th November 2009
  #4
Gear Addict
 

M/S Plugin? They have plugins for that? I always liked to have 3 tracks, unless you happen to be recording on 24 track Quantegy.

Now the question of age. How many people here have ever USED Quantegy tape or any tape for that matter? Damn you Digital Audio for creating a cleaner noise floor!


~Nice Signature Danijel
Old 24th November 2009
  #5
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Quote:
Originally Posted by danijel View Post
Haha, one day I will put it in my sig that MS is NOT mono compatible....
.......I just did it
.
Sorry, but this is nonsense. Mono-compatibility does not mean that the result will sound the same when summed to mono. How could it possible sound the same? One signal is stereo and the other is mono. If that´s your definition of mono-compatibility then there is no mono-compatibility at all.

Mono-compatibility means that by summing you will not get a loss of certain frequencies through phase-issues.

As you said summing an X/Y signal that resulted from an MS-mic will give you 100% the M-microphone signal whithout dips or bumps in your frequency response of the overall signal compared to the X/Y signal.

MS is not "maybe stereo". You should read up a little bit on MS before posting such things. MS is an 100% equivalent of X/Y-Stereo.


Regarding the OP´s question: There are plenty of freeware MS-plugins why not install that on the other system when you´re worried about session-compatibility? It´s only a question of convenience. The result wil be the same. No matter how you do the encoding/decoding.
Old 24th November 2009
  #6
Gear Head
 

Dave, apple q - appreciate the help.

I think I´ll do a bit of both actually because the fact that I have three tracks with one going to C (enter) will help with mono ambience, right ? Assuming a 5.1 mix, one M/S 3-track could help smooth out noise differences in dialogue audios, if not by its own, it could help a mono continuity track.

(Regarding the plugins, the problem is I might not be allowed to install anything at the studio I´ll be mixing.)

cheers
Old 24th November 2009
  #7
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Quote:
Originally Posted by gato sapato View Post
Dave, apple q - appreciate the help.

I think I´ll do a bit of both actually because the fact that I have three tracks with one going to C (enter) will help with mono ambience, right ?
Well, kind of. MS turns into XY (so L and R only). It is not possbile to turn MS into LCR you need at least a double-MS mic setup to get a C-signal.

Of course you can feed the M signal to the center but you will not gain any channelseparation between C and L/R since it´s almost the identical signal.

Simple example: One person speaking in the middle of the MS mic decodes to XY with the person in center on a STEREO system (phantom source). Which means the dialog will be equally loud on both L and R. When you now add M to the center the only thing you will gain is the true mono signal of the voice again in the center channel.

A true LCR version would be something different.

Plus you will have level summation effect when you do the downmix. When you sum L+R+M (all taken from the same recording) the result will be 2xM.

Same happens when you have a car drive-by on L&R. When you feed M to the center your drive-by will turn into something very mono and center-oriented. Nothing like a real LCR recording (let alone a panned mono signal)

But hey, give it a go and experiment. Rules are there to be broken. But in theory you can not extract LCR from a single MS mic. For that you need at least a third mic in your setup. Either double-MS or a true LCR mic.
Old 24th November 2009
  #8
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danijel's Avatar
Quote:
Originally Posted by apple-q View Post
Sorry, but this is nonsense. Mono-compatibility does not mean that the result will sound the same when summed to mono.
When you sum X and Y to mono, you only lose the localization info, but everything you heard in stereo is still there. With MS, everything off-axis to the M microphone gets severely changed. A bird chirping 90 degrees off-axis will be muffled and several dB softer after collapsing, depending on the directionality of the M mic.

Quote:
Originally Posted by apple-q View Post
Mono-compatibility means that by summing you will not get a loss of certain frequencies through phase-issues.
There, you've said it yourself. By collapsing an MS recording to mono, you lose ALL the high frequencies on the sides of the stereo image, BECAUSE OF THE PHASE ISSUES.

Quote:
Originally Posted by apple-q View Post
MS is not "maybe stereo". You should read up a little bit on MS before posting such things. MS is an 100% equivalent of X/Y-Stereo.
A little bit? I recommend you read Bruce Bartlett's "Stereo Microphone Techniques", instead of its misinterpretations on the Gearslutz. I dare you find a reliable resource stating that "MS is the most mono-compatible stereo technique".

"Maybe stereo" is a phrase I like because it raises awareness on this often misunderstood concept of summing MS-originated recording to mono.

BTW, I often record classical music in MS (my second favorite technique after ORTF), and I love the precise localization that I get with it! Why do you love MS? Other than because it is "mono compatible"?
Old 24th November 2009
  #9
ruy
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ruy's Avatar
unless you are mixing this yourself at your own place. i would recommend you convert the files to stereo once you find a preferred image and treat it as you would any other stereo file. there is usually not a lot of time to fiddle around with ms decoding in a re-recording stage plus you can always use your panners if you need to center it more.

also beware of routing the m and the s tracks to final mix discrete channels. the "m" track works fine for mono but the "s" track is two identical signals out of phase with each other and this will be problematic, specially when working with matrix systems.
Old 24th November 2009
  #10
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Quote:
Originally Posted by danijel View Post
When you sum X and Y to mono, you only lose the localization info, but everything you heard in stereo is still there. With MS, everything off-axis to the M microphone gets severely changed. A bird chirping 90 degrees off-axis will be muffled and several dB softer after collapsing, depending on the directionality of the M mic.
Take that same argument of yours and use it on XY:
When you use an XY-mic none of the mics are pointing at the source in front of you but to the sides. So first of all in your theory the XY-recording is already "muffled" to the front. When you record a bird chirping in front of the mic both cardioids will pick up the bird from the side and therefor what you call "severe" change will happen there as well. This has nothing to do with the stereo technique in general but with the charateristics of real microphones compared to theoretical mics that have an ideal pattern across the whole spectrum
This is the case with ANY real microphones. It has nothing to do with stereo or mono.


Quote:
There, you've said it yourself. By collapsing an MS recording to mono, you lose ALL the high frequencies on the sides of the stereo image, BECAUSE OF THE PHASE ISSUES.
What phase issues? And what about the high frequecies you´re not even picking up from 0 degrees because your XY mics are pointing away fro the source?

Quote:
A little bit? I recommend you read Bruce Bartlett's "Stereo Microphone Techniques", instead of its misinterpretations on the Gearslutz. I dare you find a reliable resource stating that "MS is the most mono-compatible stereo technique".
Thank you, I have that book and I record MS almost daily because of what I wrote earlier.

Quote:
"Maybe stereo" is a phrase I like because it raises awareness on this often misunderstood concept of summing MS-originated recording to mono.
Well when you sum the resulting XY from an MS mic you get the M-signal. No more no less. I have no idea why this would be a misunderstood concept.

Quote:
BTW, I often record classical music in MS (my second favorite technique after ORTF), and I love the precise localization that I get with it! Why do you love MS? Other than because it is "mono compatible"?
Like I said we seem to have different concepts about what "mono compatibility" means. You say that mono-compatibility means that mono sounds identical to the stereo original which is pre se impossible just like a 2D picture doesn´t look the same as a 3D picture and colour looks different than B/W.
Old 24th November 2009
  #11
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Berolzheimer's Avatar
 

I agree with Danijel about MS. When you collapse a XY or ORTF or NOS recording to mono, you aren't changing the ratio of direct to reflected or ambient sound. When you collapse an MS recording to mono you change that ratio radically, as the side mics get cancelled out altogether and you're left with only the shotgun.
Old 24th November 2009
  #12
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Berolzheimer's Avatar
 

Quote:
Originally Posted by apple-q View Post
Take that same argument of yours and use it on XY:
When you use an XY-mic none of the mics are pointing at the source in front of you but to the sides. So first of all in your theory the XY-recording is already "muffled" to the front. When you record a bird chirping in front of the mic both cardioids will pick up the bird from the side and therefor what you call "severe" change will happen there as well. This has nothing to do with the stereo technique in general but with the charateristics of real microphones compared to theoretical mics that have an ideal pattern across the whole spectrum
This is the case with ANY real microphones. It has nothing to do with stereo or mono..
Microphones are not laser beams. If you do an XY recording with the mics at 90˚ then any source directly in front is only 45˚off axis. Most decent cardioid mics, once beyond the range of proximity effect- which is usually only a few inches- will sound nearly identical at 45˚ as they do at 0˚.
Old 24th November 2009
  #13
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Quote:
Originally Posted by Berolzheimer View Post
Microphones are not laser beams. If you do an XY recording with the mics at 90˚ then any source directly in front is only 45˚off axis. Most decent cardioid mics, once beyond the range of proximity effect- which is usually only a few inches- will sound nearly identical at 45˚ as they do at 0˚.
I know. I was trying to illustrate that the argument that in an MS setup the cardioid picks up "almost no high frequencies" because the side mic is missing is about as true as my example that you quoted.
The argument was that without without the S-signal a lot of high frequencies are missing because the mid-mic doesn´t pick them up from the sides leading to something that some people like to call "mono incompatibility".
Old 24th November 2009
  #14
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danijel's Avatar
Apple-q, listen to the man whose ears are all XY, unlike most of our poor ORTF pairs!
I'm sure there's a demonstration CD attached to one of the books with sounds recorded at different angles in both MS and XY. All one has to do is sum them to mono, and no need for lengthy posts.
Better yet, I'll do my own test recordings and attach them to my sig, to avoid future waste of everyone's time Coming up this weekend thumbsup
Old 25th November 2009
  #15
Quote:
Originally Posted by apple-q View Post
I know. I was trying to illustrate that the argument that in an MS setup the cardioid picks up "almost no high frequencies" because the side mic is missing is about as true as my example that you quoted.
The argument was that without without the S-signal a lot of high frequencies are missing because the mid-mic doesn´t pick them up from the sides leading to something that some people like to call "mono incompatibility".

The difference here is in M/S, a sound source 90º to the M mic is 0º to the S mic. All directional mics have a drastic reduction at 90º compared to on axis (some more than others). So, if a sound is 90º to the M, it will probably be about 15~20dB quieter in the M mic than it is in the S mic, which is at 0º (directly facing) the sound source. When summing to mono, that 90º off axis sound drops 15~20dB (because the on axis "S" mic is removed, and all you are left with is the M signal), changing the relative balance/blend of sounds compared to the M/S in stereo.

Using an XY with Cardioid mics... since both mics are pointed at 45º angles off-axis to the centerline (direction the M would be facing), a sound at 90º to the centerline is still only 45º off axis to the mic facing it, and 135º from the mic facing the opposite direction, instead of 90º and 0º. Therefore when you sum the XY to mono the sound at 90º centerline won't have a significant drop in volume, nor will it have phase cancellation since it's 15~20dB quieter in the other mic from being at a 135º angle.

With XY, when you sum you still retain all the information from the sides. With M/S you LOSE any information from the sides and are left with just a mono mic facing forward...which by definition IS mono, not mono compatible stereo, since no information from the sides of the stereo image are still present.

One common way to combat this is to try using an Omni mic as the M instead of a cardioid or Fig8. That way, the sound source at 90º to M is just as loud as if it were at 0º (in theory anyway, unfortunately most omni's aren't truly omni through the entire spectrum).

Making sense?
Old 25th November 2009
  #16
Also, maybe this is a moot point since the ambience has already been recorded... but doesn't M/S wreak havoc on Dolby encoding/decoding, especially on ambiances that are panned even partially to the rears?

I've never tried using M/S for ambience, but I've heard it's a pain in the butt.
Old 25th November 2009
  #17
ruy
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ruy's Avatar
Quote:
Originally Posted by Etch-A-Sketch View Post
Also, maybe this is a moot point since the ambience has already been recorded... but doesn't M/S wreak havoc on Dolby encoding/decoding, especially on ambiances that are panned even partially to the rears?

I've never tried using M/S for ambience, but I've heard it's a pain in the butt.
i like m/s for ambience and group adr.

i once recorded a short film completely with m/s as an experiment, and it is one of the most natural sounding film mixes i have experienced till now, specially the natural reverb. however, the director actually listened to my suggestions and made the crew behave while shooting. during post, we collapsed all the dialogue to mono for the center channel (except a few group scenes and on set walla) and we used different recordings for front and surround BG's. when we did the mix at a dolby certified stage, we made sure to check everything through the dolby stereo matrix before printing. a couple of the tracks tended to move to surround unless we panned them a little bit to the side.

editing was pretty complicated so i don't recommend it unless you are extremely patient and enthusiastic...
Old 25th November 2009
  #18
An interesting read... so the OP should use two stereo tracks: one for Mid and one for Sides?
Old 25th November 2009
  #19
Gear Nut
 

sorry, but if you keep only the M channel as recorder and throw away the S channel (before decoding) gives you a pure mono channel. Does this not count as mono compatibility?
Old 25th November 2009
  #20
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Quote:
Originally Posted by Etch-A-Sketch View Post
The difference here is in M/S, a sound source 90º to the M mic is 0º to the S mic. All directional mics have a drastic reduction at 90º compared to on axis (some more than others). So, if a sound is 90º to the M, it will probably be about 15~20dB quieter in the M mic than it is in the S mic, which is at 0º (directly facing) the sound source. When summing to mono, that 90º off axis sound drops 15~20dB (because the on axis "S" mic is removed, and all you are left with is the M signal), changing the relative balance/blend of sounds compared to the M/S in stereo.
20dB?! A cardioid has a 90° level of -6dB compared to 0°. The resulting polar pattern of an MS-setup is IDENTICAL to a XY setup (when you use cardioids). When you drop the S-Signal you will be left with the polar pattern of the M-Mic (cardioid, or what ever you used for the M)


Quote:
With XY, when you sum you still retain all the information from the sides. With M/S you LOSE any information from the sides and are left with just a mono mic facing forward...which by definition IS mono, not mono compatible stereo, since no information from the sides of the stereo image are still present.
The S-channel carries the directional information that you need to get the L & R channels. Depending on your room this is not the same as "reflections" that someone stated earlier. When you drop the S-signal you lose the directional information which is not surprising when you turn stereo to mono.
Old 25th November 2009
  #21
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Quote:
Originally Posted by Etch-A-Sketch View Post
Also, maybe this is a moot point since the ambience has already been recorded... but doesn't M/S wreak havoc on Dolby encoding/decoding, especially on ambiances that are panned even partially to the rears?

I've never tried using M/S for ambience, but I've heard it's a pain in the butt.
Only when you turn up the S component too much. Phase reversed sound will go to the surrounds (no matter where is comes from). When you keep the S-signal in reasonable ranges it won´t be an issue. You can easily see that on a vectorscope.

The same can happen with AB or other spaced stereo signals that are very uncorrelated. So a phase meter is generally a very important tool when mixing for matrix surround.
Old 25th November 2009
  #22
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Quote:
Originally Posted by fasma View Post
sorry, but if you keep only the M channel as recorder and throw away the S channel (before decoding) gives you a pure mono channel. Does this not count as mono compatibility?
The argument is that when you throw away the S-channel the spectral content of the mono signal changes compared to a real XY setup.

I think we all mean the same thing in one way or the other. I think we need to settle on what "mono compatibility" means.

Danijel says that MS is not mono-compatible because the sound of the S-capsule is dropped and therefor one can not speak of mono-compatibility.

My point is that provided that you are using closely matched mics for M and S so they do not sound extremely different on their own then information you are droping when collapsing MS is the directional info. But in mono there is no directional info anyway.
So I think that if there is a spectral difference between the stereo and the mono of an MS setup it could be because one is using very different mics (like a dual diaphragm mic switched to 8 (like a C414 which actually uses two cardioids summed) plus a MD421 to give an extreme example. Of course this will sound different than a real XY setup using two MD421 or two c414 summed to mono.

Maybe that clarifies what I mean.
Old 25th November 2009
  #23
Here for the gear
 

Sanken CMS9 - what does that give you..

sory to hijack post and digressing slightly.. but wondered.. seein as we are on the subject.

what is the difference, in terms of what is on each channel, from recording MS with a sanken CMS9 and a shortgun+fig8 mic.

the latter obviously will be a single mono and a single side, to do with as suggested above, but the what does the Sanken (which supposedly decodes internally to stereo) give you..

if it is standard left and right can that bounce to mono effectively and can it be returned to MS?

just a thought.. as never tried it.
Old 25th November 2009
  #24
Gear Maniac
 

When people talk about M/S being mono-compatible they are usually referring to the fact that there are no comb-filtering artifacts that can be produced when you sum a non-coincident pair stereo technique. XY is (nearly) coincident, so XY doesn't have that problem either. Of course XY is really hard to get into a zepplin, and MS is really easy.

http://www.takomamedia.com/stuff/ms_..._mono_test.mp3

Here is a recording that I did a while back of auto race from about 20ft away from the track. It was recorded M/S and then I decoded it to stereo. In this experiment I played the track back and summed it to mono every few seconds. The recording for the most part still retains most of it's character and level. It's not exactly like the stereo, but neither would any other stereo technique summed to mono.

Cheers!

-Richard
Old 25th November 2009
  #25
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Quote:
Originally Posted by rhumphries View Post
When people talk about M/S being mono-compatible they are usually referring to the fact that there are no comb-filtering artifacts that can be produced when you sum a non-coincident pair stereo technique. XY is (nearly) coincident, so XY doesn't have that problem either. Of course XY is really hard to get into a zepplin, and MS is really easy.

http://www.takomamedia.com/stuff/ms_..._mono_test.mp3

Here is a recording that I did a while back of auto race from about 20ft away from the track. It was recorded M/S and then I decoded it to stereo. In this experiment I played the track back and summed it to mono every few seconds. The recording for the most part still retains most of it's character and level. It's not exactly like the stereo, but neither would any other stereo technique summed to mono.

Cheers!

-Richard
Richard,

thanks for this. It sums up what I was trying to say.
Old 25th November 2009
  #26
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danijel's Avatar
apple-q, here's the recording:

http://www.danijelmilosevic.com/MSvsXY.mp3

Every clip that you hear will be immediately repeated summed to mono (dual mono). Tell me your observations about voice colour and loudness, and also about ambiance and reverb.
Old 25th November 2009
  #27
Quote:
Originally Posted by apple-q View Post
When you drop the S-Signal you will be left with the polar pattern of the M-Mic (cardioid, or what ever you used for the M)
Exactly... so it's just "mono". Not "mono compatible stereo".
Old 26th November 2009
  #28
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Berolzheimer's Avatar
 

Quote:
Originally Posted by apple-q View Post
The S-channel carries the directional information that you need to get the L & R channels. Depending on your room this is not the same as "reflections" that someone stated earlier. When you drop the S-signal you lose the directional information which is not surprising when you turn stereo to mono.
think of it this way. in a somewhat reflective environment, like many normal acoustic environments we find ourselves in, the ratio of direct to reflected sound reaching our ears, or our mics, gives us important psychoacoustic cues as to the distance that teh sound source is from us. Keep in mind that the reflections are coming from all around us. So you place something in the mix so that it sounds like it's in the background in your stereo mix. If it's an XY or ORTF recording, when summed to mono it will still have those same distance cues & will still appear to be in the background. IF it's an MS recroding, when summed to mono a lot of the reflected signal from the sides & back will get cancelled out, and you'll be left with a much dryer, & therefore CLOSER, sounding source. It messes with your spacial placement in a big way.
Old 26th November 2009
  #29
Gear Head
 

(Thanks to everyone for contributions, recordings and links, this was my first post , it is being very interesting.)

About the potential problems with Dolby:

I have most of my ambience tracks recorded with MS ( Rode NT2 and KM184, I know, very different mics, what I had available...), so if I downmix it from 3 tracks to 2 tracks in Protools will I still be running into trouble regarding phase issues and the Dolby matrix ? Will my ambiences all go to the back ? Or once it`s in two tracks the Mid mic information that goes to L and R prevents it from happening ?
Old 27th November 2009
  #30
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I've got to say that this discussion is extremely esoteric. To my mind, MS doesn't buy me anything but more hassle.

If a track is recorded properly using XY or ORTF, then I can easily fold it down to mono or create a stereo center by collapsing the track using only panners. Why in the world would I want to bother with MS? All it does is add unecessary complexity. I've got enough things to deal with without bothering with a format that does little more than complicate my work flow for minimal, if any benefit.

Let's get real here. If you are recording things in a way that slows down or complicates the process without appreciably improving the outcome, then you aren't an artist, you are an obstacle, because every job I do has strict time restrictions that require incredible efficiency in order to turn out good work. Every unnecessary extra step or complicating factor just means I have less time to devote to making it sound good.
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