Old 04-20-2021, 10:31 AM   #1
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Default Mid/Side Recording

I decided to try out some mid/side recording the other day. I got myself a cardioid (I'm pretty sure) condenser mic for my center channel, and a figure 8 for my sides, and doubled the figure 8, and panned hard left and right. And the results are pretty interesting. But, I find that my mono signal, sounds very mono when soloed, and my figure 8 stereo signal sounds very level in stereo field when soloed, but when I combine the two, the combination seems panned a little to the left. If I invert polarity of the mono mic, it sounds very much to the right.

Is this because of my mic placement or something perhaps? Did I do something wrong? Or is this normal? Seems like it would be an undesirable way for this to work to me.
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Old 04-20-2021, 11:18 AM   #2
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I decided to try out some mid/side recording the other day. I got myself a cardioid (I'm pretty sure) condenser mic for my center channel, and a figure 8 for my sides, and doubled the figure 8, and panned hard left and right.
When you duplicate the figure 8, don't forget to invert the polarity (on the one that you pan hard right). You shouldn't invert the polarity of the "mid" mic, only the right-hand channel of the figure 8.

Also the capsules of your mics need to be as coincident as possible and the sides of the figure 8 need to be exactly 90 degrees from the mid.

A simpler approach is to use the free MSED plugin from Voxengo.
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Old 04-20-2021, 11:37 AM   #3
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I think I did all of those things, but I still notice a bias to one side when I put them all together.

I tried inverting the other side of the figure 8 instead, and still got the same result, but on the other side.

I had one condenser which was sort of like a shotgun style mic. That was the center channel, and I used an AKG c414 as the figure 8.

Maybe I placed the figure 8 wrong? I was thinking one side of the 8 would shoot out the front and the other side would shoot out the back, and that I'd have nulls on the edges of the microphone, but maybe that was a false assumption? But, it looks right, when looking at this

Is there supposed to be a bias like this?

So, the c414 is kind of a flat square almost. I pointed the flat sides perpendicular to the guitar, and then I took the shotgun condenser and set that along the top of the c414, pointed straight at the guitar.
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Old 04-20-2021, 11:41 AM   #4
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Just a sanity check that the Fig-8 mic is aiming L/R in relation to your position. So, it's the front/back of the mic itself, but the mic is turned 90 degrees in relation to the source it is recording. That's why it's called "sides".

Actually, your last sentence makes it sound like you have it correct. Just remember M/S is very directional up close and works better with a little distance. Otherwise, it will pick up the tiniest L/R movements when playing or even left vs right hand or sound "crooked" if too close. When I was doing a lot of singer/player recording with M/S a couple years ago, I didn't like it until I was at minimum 20+" back from the mic, if not 30" YMMV.
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Old 04-20-2021, 12:39 PM   #5
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I don't know about the C414, but lots of figure 8 mics have a level difference between front and back and need a bit of level correction.

Could that explain the bias?
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Old 04-20-2021, 12:42 PM   #6
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Originally Posted by karbomusic View Post
Just a sanity check that the Fig-8 mic is aiming L/R in relation to your position. So, it's the front/back of the mic itself, but the mic is turned 90 degrees in relation to the source it is recording. That's why it's called "sides".

Actually, your last sentence makes it sound like you have it correct. Just remember M/S is very directional up close and works better with a little distance. Otherwise, it will pick up the tiniest L/R movements when playing or even left vs right hand or sound "crooked" if too close. When I was doing a lot of singer/player recording with M/S a couple years ago, I didn't like it until I was at minimum 20+" back from the mic, if not 30" YMMV.
I agree... a bit of space goes a long way to making the m/s technique far more flexible. You're dealing with more room at that point too. I like that for singer-songwriter style recordings. It's one of my preferred ways to capture.
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Old 04-20-2021, 01:11 PM   #7
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I don't know about the C414, but lots of figure 8 mics have a level difference between front and back and need a bit of level correction.
That seems a likely culprit: most multipattern condenser mics and even dedicated figure 8 condensers don't have symmetrical pickups in figure 8. As far as I know the only condenser that truly does it is the Sennheiser MKH 30. Ribbons usually do a better job in that department but you work with what you have....
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Old 04-21-2021, 06:28 AM   #8
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Reason for the tilt in the stereo field is not variation in symmetrical pickup (front/rear of fig8 mic) but the orientation of the entire ms stereo mic configuration not being aligned with the actual "centre of volume" of the source being recorded. This is an error often seen when ms recording acoustic guitars. The ms setup is oriented towards the point between the neck and the sound hole. Not a lot of sound is generated on the neck's side. Almost all of the sound is coming from the body's side, thus, the stereo image picked up will tilt towards the body's side. You have to pan the ms mic config and point it at the level centre of the guitar to get a symmetric stereo image.

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Old 04-21-2021, 06:41 AM   #9
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I know you know but ^Yea, we can fix that by backing up a bit because it's misusing M/S. When we think of M/S... especially the S pointing 90 degrees in each direction in relation to the center. The closer you get the weirder it is going to be.

M/S is better with some distance. It is far better suited for say recording a semi-circle of instruments - recording singer/guitar is fine but it needs similar distance as M/S is not a close-micing type of configuration design.
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Old 04-21-2021, 07:01 AM   #10
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Originally Posted by karbomusic View Post
...

M/S is better with some distance. It is far better suited for say recording a semi-circle of instruments - recording singer/guitar is fine but it needs similar distance as M/S is not a close-micing type of configuration design.
MS happens to be a coincidental stereo mic technique. No need to back up from the source per se because it's MS. Just make sure you are pointing at the correct spot like the source's volume centre if you wanna get a centered stereo image and make sure that it sounds good. MS isn't always the best technique depending on various circumstances.

Pointing at the source's level centre, you can still pan/lift/lower the entire ms stereo config as a whole to avoid boominess or a thin sound. I'm mostly recording guitars in MS fairly close 1.) to reduce room sound and 2.) to be able to get an extremely huge yet phase-coherent stereo image of that guitar.

If you get very close to the guitar, spaced XY can virtually be considered AB because level differences and directional differences between the mics are much more pronounced than with the same spaced XY setup a few meters away from the source.

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Old 04-21-2021, 07:35 AM   #11
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MS happens to be a coincidental stereo mic technique. No need to back up from the source per se because it's MS.
All coincidental means is the capsules are really close and able to derive a stereo image - that does not mean every type of coincident config behaves identically at various distances. I agree that too close is too close for any config, but M/S's too close is further away than X/Y's for all practical purposes - I'm not saying that's the OPs issue but M/S isn't a close micing solution so I always sanity check someone with similar sounding issues to make sure.
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Old 04-21-2021, 07:54 AM   #12
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All coincidental means is the capsules are really close and able to derive a stereo image. I agree that too close is too close for any config, but M/S's too close is further away than X/Y's for all practical purposes - I'm not saying that's the OPs issue but M/S isn't a close micing solution.
oops, I must have been doing something wrong for the last couple of decades

Joking aside, "coincidental" in this context doesn't mainly refer to the close distance of the mics' capsules. It refers to the situation that sound from any horizontal direction must arrive at both diaphragms absolutely simultaneously which is essential in order to prevent any phase delay between both signals from happening and which in turn results in getting rid of any comb filtering that automatically occurs as soon as the two capsules are not absolutely perpendicular (and also as close as possible!) on top of each other but apart horizontally, even by the slightest amount. Depending on the source, you can get virtually as close to it with MS as with any other mic technique.

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Old 04-21-2021, 08:11 AM   #13
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oops, I must have been doing something wrong for the last couple of decades
Me too Whenever I have some spare time I'll dig up some old or perform some new tests.
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Old 04-21-2021, 11:56 AM   #14
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I'm using my own combined MS-ORTF setup on a single tripod for maximum convenience during tracking and maximum flexibility during mixing through my "5-channel acoustic guitar decoder MS + DI + LR" VST plugin which allows me to use any selection/combination/blend of MS, XY and DI signal after the fact. Plus, all this requires only a single track for the guitar, greatly facilitating editing and keeping track count low!

It also works for small ensembles.





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Old 04-22-2021, 06:34 AM   #15
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Fantastic plugins Mr Axiom. I have downloaded a few and as soon as this damn war is over and work picks up I will send you dinner via paypal. At the moment I am struggling to pay my rent.
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Old 04-22-2021, 08:06 AM   #16
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I want to ask about that plugin. Is the M/S actually decoded to stereo in there? If so then isn’t the M/S stereo width control redundant to the individual M and S trim controls? If not, then kind of same or at least you could do it whenever you do decode them.
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Old 04-22-2021, 09:05 AM   #17
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Originally Posted by karbomusic View Post
Just a sanity check that the Fig-8 mic is aiming L/R in relation to your position. So, it's the front/back of the mic itself, but the mic is turned 90 degrees in relation to the source it is recording. That's why it's called "sides".

Actually, your last sentence makes it sound like you have it correct. Just remember M/S is very directional up close and works better with a little distance. Otherwise, it will pick up the tiniest L/R movements when playing or even left vs right hand or sound "crooked" if too close. When I was doing a lot of singer/player recording with M/S a couple years ago, I didn't like it until I was at minimum 20+" back from the mic, if not 30" YMMV.
Oh ok, this might be exactly what it was. I was indeed pretty close to the mic, like maybe about a foot away.
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Old 04-22-2021, 09:08 AM   #18
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I don't know about the C414, but lots of figure 8 mics have a level difference between front and back and need a bit of level correction.

Could that explain the bias?
I don't think so, because the c414 on its own sounded even in the stereo field. And the other condenser sounded straight down the middle. It was when I combined them that I got the bias, and that might be because of some phase cancelation happening. It may very well be that it's just because standing in that spot, there would be a natural bias like that. But you don't really hear it when each mic is alone, since it's just one mic, and not two, so there's no real way to have any bias there. But once you mix them, then it adds that sort of possibility for 3D, and the phases cancel out to give the directional information. This is my guess so far, anyway, and going with what karbo said, I think that makes good sense. When you're further off, I could see this being less obvious, but up close a real factor.
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Old 04-22-2021, 09:11 AM   #19
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That seems a likely culprit: most multipattern condenser mics and even dedicated figure 8 condensers don't have symmetrical pickups in figure 8. As far as I know the only condenser that truly does it is the Sennheiser MKH 30. Ribbons usually do a better job in that department but you work with what you have....
Well, maybe I'm wrong then lol.

Actually, to your point, it looks like here: https://www.akg.com/on/demandware.st...r_Patterns.pdf The polar pattern doesn't appear to be perfectly symmetrical. So, maybe you're right about that. This isn't the exact model I used, but it's a modern version of it, so I think they should be similar in this respect.
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Old 04-22-2021, 09:12 AM   #20
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Originally Posted by SonicAxiom View Post
Reason for the tilt in the stereo field is not variation in symmetrical pickup (front/rear of fig8 mic) but the orientation of the entire ms stereo mic configuration not being aligned with the actual "centre of volume" of the source being recorded. This is an error often seen when ms recording acoustic guitars. The ms setup is oriented towards the point between the neck and the sound hole. Not a lot of sound is generated on the neck's side. Almos all of the sound is coming from the body's side, thus, the stereo image picked up will tilt towards the body's side. You have to pan the ms mic config and point it at the level centre of the guitar to get a symmetric stereo image.

.
This is what I feel it is, and because it's mic'd so close, you can really hear that.
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Old 04-22-2021, 09:15 AM   #21
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Originally Posted by SonicAxiom View Post
I'm using my own combined MS-ORTF setup on a single tripod for maximum convenience during tracking and maximum flexibility during mixing through my "5-channel acoustic guitar decoder MS + DI + LR" VST plugin which allows me to use any selection/combination/blend of MS, XY and DI signal after the fact. Plus, all this requires only a single track for the guitar, greatly facilitating editing and keeping track count low!

It also works for small ensembles.





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Pretty cool looking rig and routing plugin!

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Old 04-22-2021, 12:01 PM   #22
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Fantastic plugins Mr Axiom. I have downloaded a few and as soon as this damn war is over and work picks up I will send you dinner via paypal. At the moment I am struggling to pay my rent.
Glad if the plugins are useful to you, Tom, and hope that you manage to get through this pandemic sh...!

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Old 04-22-2021, 12:16 PM   #23
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I want to ask about that plugin. Is the M/S actually decoded to stereo in there? If so then isn’t the M/S stereo width control redundant to the individual M and S trim controls? If not, then kind of same or at least you could do it whenever you do decode them.
The plugin takes LR stereo and encodes it to MS. The trim sliders trim the M and the S channel separately (for example to account for inproper M or S recording levels). MS output trim trims the entire MS stereo signal as a whole without changing the stereo width. MS stereo width gradually adjusts M vs. S level from pure M (S level = -inf.) to M level = S level to pure S (M level = -inf.).

Actually, MS stereo width is not redundant since the trim sliders can not trim either signal down to - inf but only by +-20 dB. The trim sliders are kinda fine tuning sliders on top of the width slider which in turn gives the convenience of adjusting width via a single slider.

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Old 04-22-2021, 03:02 PM   #24
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The trim sliders are kinda fine tuning sliders on top of the width slider whwich in turn gives the convenience of adjusting width via a single slider.
Ah. Makes sense. Thanks
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