A couple of questions about mid-side recording

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brassplyer

brassplyer

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Isn't mid-side creating "fake" stereo? I.e. the stereo field is created by inversion of the side mic copies.

Instead of using a figure-8 mic for the side mic, why wouldn't a mix of two mics aimed 180 deg apart work?
 
brassplyer said:
Isn't mid-side creating "fake" stereo?
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No.

brassplyer said:
I.e. the stereo field is created by inversion of the side mic copies.
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The stereo field is essentially there already, it's just captured by the mics. Copying/inverting the side mic is how M-S works.

brassplyer said:
Instead of using a figure-8 mic for the side mic, why wouldn't a mix of two mics aimed 180 deg apart work?
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You could get something sort of similar with that but cardioid or even super-cardioid mics don't have the deep null at 90° like a figure-8 mic. You might as well do an X-Y setup.
 
bouldersoundguy said:
Isn't mid-side creating "fake" stereo? I.e. the stereo field is created by inversion of the side mic copies.
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No.

The stereo field is essentially there already, it's just captured by the mics. Copying/inverting the side mic is how M-S works.
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Isn't virtually all of the "width" you hear from phase inverted copies of the mono figure 8 mic? You can get a faux stereo effect by phase inverting copies of any mono mic.

As I understand it the main reason to use mid-side is to be mono compatible.
 
Well, the phase inversion is there to essentially undo the inversion of one of the side signals that happens at the mic, and to cancel out the center signal from the sides. It is not at all the same thing as copying the signal and inverting. In that case the center signal is cancelled entirely and both sides have exactly the same content except that one speaker pushes when the other pulls. That's fake stereo. With M/S, the left and right channels actually do have different content.
 
There's nothing fake about it.
Mid side takes a figure 8 mic and kinda compares it to the centre mic.

When set up, pressure from 45 degrees left results in + voltage from the mid and side mics simultaneously. They are 'in agreement'.
This is, say, your left audio.
Pressure from the other side results in + from mid and - from side, which will cancel to some extent.

When you bring in an inversion of the the side mic, you're creating the exact opposite scenario, which gives you the other half of your stereo image.

Using two mics in place of your fig8 won't work anywhere near as well.
The fig8 allows cancellation so <thinking out loud> to replicate it I guess you'd have to pan
left mic left
right mic right
left mic inverted polarity right
right mic inverted polarity left.

Even then, it won't be anywhere near as accurate.
 
brassplyer said:
You can get a faux stereo effect by phase inverting copies of any mono mic.
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Nope.

Simple test.....try what you are suggesting above, and record to a pair of tracks....then collapse them to mono.
Then record a pair of tracks using M/S...then collapse them to mono.

You will hear why they are two different things.


As others have said...it's true the in M/S the figure-8 mic is technically a "mono" mic....but each of its lobes is picking up something slightly different and when summed within the M/S matrix, you get a true L/R stereo image that also collapses perfectly to a mono image because there's no cancellation between the L and R sides.
 
brassplyer said:
Isn't virtually all of the "width" you hear from phase inverted copies of the mono figure 8 mic? You can get a faux stereo effect by phase inverting copies of any mono mic.
Click to expand...

The width of mid-side comes from the capturing something about the sound that's already there. Proper mid-side micing creates a mathematically and geometrically accurate representation of a stereo sound field. A copied and inverted signal from a single mic does not.

brassplyer said:
As I understand it the main reason to use mid-side is to be mono compatible.
Click to expand...

Mid-side is mono compatible because it's a coincident pair. An X-Y pair is also coincident and mono compatible.
 
If you add a fig.8 and an omni (both pointing forward) you get a cardioid.
Do the same with two fig.8s and an omni - you get a hyper-cardioid.
Do the same with one fig.8 and two omnis - you get a wide-cardioid.

This is all elementary and how all polar-patterns are made.

Now - turn the fig.8 on its side and add a cardioid pointing forward and you get a hyper-cardioid pointing half left.

Polarity-invert the fig.8 and the hyper-cardioid now points half right.

You can widen or narrow the stereo image by the relative levels of the two mics.

This is the essence of MS.
 
John Willett said:
You can widen or narrow the stereo image by the relative levels of the two mics.
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...To a certain extent. The "true stereoness" depends on the interaction between the two mics. If you change the relationship by too much you end up with either mono, or the "fake stereo" which collapses to silence.
 
bouldersoundguy said:
Isn't mid-side creating "fake" stereo?
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No.
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Here's an example. Its seems the "width" is only there because of the phase inverted side mic tracks as shown by the point in the video where they invert the side mic channels. They demonstrate the mixing of the two starting about 1:00. Bringing in the mid mic seems to just bring fullness to the middle of the field.

If this isn't so I'd appreciate it if you could explain why it isn't so.

FullOnDrums.com ep22 - The Mid/Side Technique - YouTube
 
brassplyer said:
If this isn't so I'd appreciate it if you could explain why it isn't so.
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What exactly are you questioning...that Mid/Side is really a true stereo technique....or you simply do understand the reason why it is stereo....?

No, the Mid mic doesn't just bring fullness to the middle....it's also combining it's signal with each of the sides of the Side mic.
The answer is in that math....Mid + (+ Side) and Mid + (- Side).

It works because the signals are combined into the final stereo image. By raising ot lowering the level of the Side mic...you increase or decrease its portion of the combined stereo signal, and that controls the width of the stereo image. If you go to high....the middle drops out, if you go too low, you hear mostly the Mid mic, and it sounds more mono.
 
miroslav said:
What exactly are you questioning...that Mid/Side is really a true stereo technique....or you simply do understand the reason why it is stereo....?

No, the Mid mic doesn't just bring fullness to the middle....it's also combining it's signal with each of the sides of the Side mic.
The answer is in that math....Mid + (+ Side) and Mid + (- Side).

It works because the signals are combined into the final stereo image. By raising ot lowering the level of the Side mic...you increase or decrease its portion of the combined stereo signal, and that controls the width of the stereo image. If you go to high....the middle drops out, if you go too low, you hear mostly the Mid mic, and it sounds more mono.
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I have never had the opportunity to try M-S recording and only know what I have read about it.

I have always assumed that it is the acoustic equivalent of the matrix system used for the Zenith GE system used for FM stereo radio? Colour TV (PAL I) is a much more complex version of the same system.

Sum and difference signals are much more robust for transmission and storage than pure stereo.

Dave.
 
I've used M/S for drum overheads for awhile now...I put the mics a couple of feet up and sort of over the drummer's head.

I even used it on some guitar tracks...or dual figure-8 mics in a Blumlein configuration.
Kinda cool sounding.
 
brassplyer said:
Its seems the "width" is only there because of the phase inverted side mic tracks
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Right, because one mic can't capture a stereo sound field. Sound arrived at the given point in space from various directions and the mics, placed at that point, captured that information. There's nothing "fake" about it.
 
There is nothing fake about it. A sound coming from the left will actually be heard on the left if the recording. If done right, it is an accurate representation of the sound field that was recorded.

Another reason it is mono compatible is because the figure 8 Mic cancels completely in mono, leaving only the center Mic being heard.
 
Farview said:
There is nothing fake about it. A sound coming from the left will actually be heard on the left if the recording. If done right, it is an accurate representation of the sound field that was recorded.
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That's part of what I'm talking about. You've got two mics stacked vertically, which all the m/s setups I've seen are. One is aimed center, one is taking info from the sides but in a mono fashion. Where is the true Left / Rightness coming from?
 
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