Topic: MS Miking vs Post-Recording MS

[Breeze]

There's free audio plugins now (like this) that will take a stereo recording and derive the MS signals which can then be processed as a standard MS recording. So my question  is: if I record stereo using an XY coincident pair and then use such a plugin to do MS mixing/eq/etc, what is the advantage of recording MS in the first place?   

Of course there's bound to be differences, but would they be significant? Thanks.

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There's free audio plugins now (like this) that will take a stereo recording and derive the MS signals which can then be processed as a standard MS recording. So my question  is: if I record stereo using an XY coincident pair and then use such a plugin to do MS mixing/eq/etc, what is the advantage of recording MS in the first place?   

Of course there's bound to be differences, but would they be significant? Thanks.

There are differences (mainly in how the more on-axis mid sounds compared to a standard xy pair that is more off-axis or vice versa), but unless you are trying to milk that last mile of quality out of your recordings, it generally doesn't matter. If you don't have a figure 8 on hand, it's something to consider when you need to make stereo angle adjustments later, but I found it didn't work as well as running an MS pair did (at least in my experience, ymmv).

[Will_S]

Another advantage of "real" M-S with a card mid and a figure 8 side is that if mixes down if 1:1 you get something like hypercardioids at 110 degrees.  More mid yields a tighter angle between virtual mics with a fatter pattern, more side yields a wider angle between virtual mics with a narrower pattern.
If you use XY cards, a 1:1 mix gives you back cards at whatever angle you used.  Again, more mid means a narrower angle and even fatter virtual mics and vice versa. 

Because you can't change the virtual angle between mics without also changing the virtual pickup pattern, it's important that you pick the right starting point that will give you back useful virtual mic patterns.  For me, hypercardioids at 110ish degrees gives you lots of usable room on either side.  If you start with say cards at 90 degrees, any increase in mid is just going to give you a really monoish recording in my experience.  And even boosting the virtual side, you'll have a hard time getting a really wide image out of it.

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Another advantage of "real" M-S with a card mid and a figure 8 side is that if mixes down if 1:1 you get something like hypercardioids at 110 degrees.  More mid yields a tighter angle between virtual mics with a fatter pattern, more side yields a wider angle between virtual mics with a narrower pattern.
If you use XY cards, a 1:1 mix gives you back cards at whatever angle you used.  Again, more mid means a narrower angle and even fatter virtual mics and vice versa. 

Because you can't change the virtual angle between mics without also changing the virtual pickup pattern, it's important that you pick the right starting point that will give you back useful virtual mic patterns.  For me, hypercardioids at 110ish degrees gives you lots of usable room on either side.  If you start with say cards at 90 degrees, any increase in mid is just going to give you a really monoish recording in my experience.  And even boosting the virtual side, you'll have a hard time getting a really wide image out of it.

Do XY > MS first, then adjust and you get a similar effect.

The problem is your doing 2 sets of mixing where you only do 1 with MS and when you create the MS pair out of the XY cards, it doesn't have the same sound that you would if you did MS natively (again, in my experience). Yes, you can adjust it, but your not really adjusting mid/side information in the same fashion. If you've got some XY recordings you can definitely try it in post, but they have to be true XY recordings where the diaphragms are stacked properly, otherwise you just introduce more phase cancelation in when you do the 2 mixes. If you try, make sure to listen to micro details and placement in the soundstage.

[Will_S]

Do XY > MS first, then adjust and you get a similar effect.

Depends what you mean by similar.  You can vary the width in post, yes.  But the polar pattern of the virtual microphones is not the same (just like you get different results depending on the pattern of the mid mic in a traditional M/S setup), nor is how the pattern width trades off with the angle between the virtual mics.

[tbrown4]

I'm really curious about this software.

So, if I record something and I wish to use the virtual M/S processing, should I record using cards at X/Y? Before I get in to experimenting on my own, what are your experiences and recommendations?

[page]

I'm really curious about this software.

So, if I record something and I wish to use the virtual M/S processing, should I record using cards at X/Y? Before I get in to experimenting on my own, what are your experiences and recommendations?

For it to work you need a coincident pair. Doesn't need to be 90 degrees necessarily, but it does need to be coincident.

If someone wants a set of raw MS files to get used to MS processing first, I can post a sample from when I ran that. Once you play with it, taking a standard coincident pair and going to MS first (I swear it's L+R and L-R gets you there) is the only additional step.

[Gutbucket]

I'm really curious about this software.

So, if I record something and I wish to use the virtual M/S processing, should I record using cards at X/Y? Before I get in to experimenting on my own, what are your experiences and recommendations?

You can use any coincident pair, doesn't have to be cardioids.  For the reasons Will_S mentions above, I'm not a big fan of cardioids in X/Y, so I'd prefer super/hypercards or figure-8s if you have them and the situation calls for it.  Two crossed Figure-8s is an interesting case in that it is the only one which does not change the microphone pickup pattern pattern when varying the M/S ratio, only the virtual angle between mics changes.  The 1:1 sum & difference of two figure-8s at 90 degrees is one virtual figure-8 pointing straight ahead and one pointing directly left.  Same thing the other way around, recording M/S with figure-8s (one mic pointing straight ahead, the other 90 degrees left) matrixes 1:1 to Blumlein L/R 90 degree crossed 8s.  I understand that is how Mr Blumlein himself prefered to do it.. but he was also doing some other frequency specific M/S manipulations to the signal so starting with M/S mic setup eliminated a conversion step.

Do XY > MS first, then adjust and you get a similar effect.

The problem is your doing 2 sets of mixing where you only do 1 with MS and when you create the MS pair out of the XY cards, it doesn't have the same sound that you would if you did MS natively (again, in my experience). Yes, you can adjust it, but your not really adjusting mid/side information in the same fashion. If you've got some XY recordings you can definitely try it in post, but they have to be true XY recordings where the diaphragms are stacked properly, otherwise you just introduce more phase cancelation in when you do the 2 mixes. If you try, make sure to listen to micro details and placement in the soundstage.

A practical limitation is the mic diaphrams are never perfectly coincident, which introduces some aliasing errors in the virtual patterns at the first matrix step.  In practical mic arrangements, the capsules are arranged to be horizontially coincident wth one positioned directly over the other.  M/S setups have a slight advantage in that the resulting errors are symetrical to the left and right of center.  An otherwise identical X/Y setup produces the same amount of error, but it is not manifested as symetrically left to right. As Page notes, when listening, the difference between the different manisfestation of errors may be subtle. 

More important is the differences between the actual mics used, the differences between their actual patterns, and where they are pointed, due to most mics becoming less accurate off-axis.

Personally I think about what virtual pattern I want and then how to get it by manipulating the patterns of mics I have access to.  This came up yesterday in the Team ADK thread, where I decided to try a M/S setup with a hypercardioid mid so that I can derive a virtual pattern somewhat closer to the fig-8 end of the continuum than a cardioid mid would provide.
 

[Gutbucket]

BTW, many DAWs use M/S processing as stereo imaging or width controls, often as extentions of the simple pan function.

I've noticed that more and more stereo plugins like EQs and compressers feature M/S modes as well.  In that mode the plugins do a M/S matrix at the input, do their work on the seperate mid and side components instead of left and right, then re-matrix to L/R again at the output.

[capnhook]

I like the results and control I get using msed with my LSD2, using coincident cardioid setting, set at 90'.