Topic: Potential New M/S Technique

[SonicSound]

I have been thinking about trying something different utilizing the mid-side concept. 
Has anyone ever tried creating a mid-side recording by placing a figure-8 onstage [side] and mono feed sound board [mid] to make a mid-side recording?

[hummat]

This idea occurred to me a few years ago too.  I posted almost the exact same question here. I can't remember why it won't work, but I am sure I will be reminded if I keep an eye on this thread 

-jay

[SonicSound]

Did you actually try it? 

I am sure that there are some phasing challenges to overcome but it might just work.

This idea occurred to me a few years ago too.  I posted almost the exact same question here. I can't remember why it won't work, but I am sure I will be reminded if I keep an eye on this thread 

-jay

[stevetoney]

Seems to me that creating the stereo effect in mid-side is all about the phase relationship between the two mics...which is why you want to get the mid capsule as close to the side capsule as possible.  I thought that it was the overlapping soundfields of the two microphones that causes the stereo effect and by increasing and decreasing the level of the mid channel in post, you're sorta canceling out what's going on in the side components of the figure 8 and that's what varies the amount of stereo separation that's heard. 

If you use a source that has no phase relationship to the Figure 8 because it was recorded in another part of the room or from the SBD, I don't understand how the concept can work.

[Todd R]

I would say that it depends on if there is any noticeable propagation delay thru all the "soundboard" equipment.  If that is negligible (<0.1ms?), then I think it isn't that there is no phase relationship, it would just be unknown.  So the soundboard might be out of phase from the stage and when you decoded the M+S you might be swapping left and right channels.

If there is some unknown level of propagation delay, then I'm with Steve -- you'll be left with junk.

If it were to work though, the soundboard channel would essentially be a omni source (not a directional, cardioid source as MS generally specifies).  You can look up what happens if you use an omni as your mid mic, but basically regardless of the M level used or S level used, you end up with an effective pair of some type of directional mics facing 180 degrees apart from one another.  Depending on the levels used you could effectively have subcards, cards, or hyper/supercards, but they will always have an effective included angle of 180 degrees.

I'd still be curious to hear how this played out in practice.

[SonicSound]

According to what I have read, the following results are achieved with changing the polar pattern [assuming a 50/50 mix]:
Omin = two cardioids oriented directly left and right [180deg of eachother]
Cardioid = two hypercardioid orientated 66deg +/- centerline
Figure-8 = results in a blumlein pair

The more I read about the m/s technique the less confident I am about this approach working.  I am still going to try this the next time I have access to the sound board.  It will probably turn out like crap but it’s worth a try.

If it were to work though, the soundboard channel would essentially be a omni source (not a directional, cardioid source as MS generally specifies).  You can look up what happens if you use an omni as your mid mic, but basically regardless of the M level used or S level used, you end up with an effective pair of some type of directional mics facing 180 degrees apart from one another.  Depending on the levels used you could effectively have subcards, cards, or hyper/supercards, but they will always have an effective included angle of 180 degrees.

[boojum]

Here is one link which will help:  http://www.wikirecording.org/Mid-Side_Microphone_Technique

There are many others.

[notlance]

You might get something that sound like "stereo", but I don't expect that the image will be anywhere near accurate.  Relative to what is required for the mind's perception of direction there will be huge timing differences between the "M" and "S" microphones.  Your "M" mics will be inches from the sound source, and the "S" mic will be several feet away, if I understand your proposal correctly.  Think about how far spaced omnis are from each other.  If you get them more than a couple of feet apart the stereo image has a big hole in the middle.

I guess you could delay the M signal to get it to coincide with the S mic, but how much delay would you use since the delay to the S mic varies depending on where the musicians are?

In addition, you will be mixing the M and S signals that are not coincident so expect to get some comb filtering.

But seriously, give it a try.  It’s easy to do these mental experiments, but there is nothing like going out and actually trying it in the real world.

[DSatz]

M/S recording works because the signals from the coincident M and S microphones are matrixed like this:

M + S -> Left
M - S -> Right

This relationship can work only if M and S are at the same distance from the direct sound sources, causing sound from any one sound source to arrive at both microphones exactly simultaneously. Any difference in that arrival time between the two microphones will cause various cancellations and reinforcement at different frequencies ("comb filter" effect). So not only would the stereo image not work, but the frequency response would be all bumpy as well.

Sorry.

--best regards