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Mid Side Concept

Discussion in 'Recording' started by Guitarfreak, Jul 16, 2009.

  1. Guitarfreak

    Guitarfreak Well-Known Member

    Didn't want to distract from the point of the other thread. Jack, have some morning juice, you're not making sense yet :D

    So if you isolate the side mic which is the fig 8 mic, since the front end is Ve+ and the back side Ve- then wouldn't panning hard left give you the Ve+ signal and panning hard right give you the Ve- signal? Does it change if you add in the Mid signal and M/S summing? i.e. the M+S and M-S? I'm not exactly clear on this quite yet, or what phase has to do with anything.

    To me, three signals come in, you do what you want with them. Why can't you just keep the fig 8 as a stereo track panned center and the unidirectional mic a mono track panned center? Wouldn't that give you the desired stereo effect? Or are you switching the phase purposely for the fig 8 mic to cancel out the shared frequencies i.e. what the Mid mic is picking up? Because that makes a shred more sense.
     
  2. TheJackAttack

    TheJackAttack Distinguished Member

    We'll start with the phase issue. In a M/S array you are adding the unidirectional center to ONE side of the figure 8 for left and the OTHER side of the figure 8 for right.

    The figure 8 mic itself is generating only one signal and not two so you don't have two signals to work with. However, the ribbon or condenser capsule(s) have a positive (+) element and a negative (-) element to it. + corresponds to the "front" and - corresponds to the "back".

    If you want to combine the back of the figure 8 with something you have to make the (-) into a (+). You do this by flipping the phase 180 degrees.

    If the phase issue starts to make a little sense you will then understand why you have to hard pan the fig 8 tracks.

    http://en.wikipedia.org/wiki/Microphone_practice#M.2FS_technique:_Mid.2FSide_stereophony

    Apparently I can't chase bears in the morning and make sense online at the same time.
     
  3. TheJackAttack

    TheJackAttack Distinguished Member

    And that was bears not beers.
     
  4. Guitarfreak

    Guitarfreak Well-Known Member

    I think I now understand what you have to do, but not why. Dupe the bi track and hard pan both, flip phase on one to create the -side. Then I guess you just leave the one mid track panned center.

    The link said that the result is mono compatible, which makes sense why you have to flip the phase, except, people don't really listen to music in mono...ever. So why does it matter? I personally have done phase switching myself, but found that it results in an off balance stereo image and resolved to leave it the way it was. Mind this was NOT using M/S technique, but rather two separate and unique hard panned tracks.
     
  5. Guitarfreak

    Guitarfreak Well-Known Member

    Actually, I take that back. I just tried phase flipping with a project of mine that has six tracks total and it helped clean out the noises and bass boom from the rhythm tracks. But now when the lead part goes above it it causes problems. Here's the mix:
    All clean tones

    SM57 Lead (Center)
    i5 Lead (Center)

    SM57 Rhythm (Left)
    i5 Rhythm (Left)

    SM57 Rhythm (Right - Phase flipped)
    i5 Rhythm (Right - Phase flipped)

    Phase flipping helped the rhythm tracks not sum eachother's shared frequencies (the low end) and cleaned it up nicely. When the lead comes in with the same tone it sums with the left rhythm. I tried phase flipping only the i5 lead track, but I'm not sure if that is good practice. What would you do?
     
  6. BobRogers

    BobRogers Well-Known Member

    Anytime you listen to speakers that are close together and you are far away - mono - even if the tracks are stereo. So, most radio and television listening is effectively mono.
     
  7. Codemonkey

    Codemonkey Well-Known Member

    "clean out the noises and bass boom from the rhythm tracks"

    By cancelling the whole lot?
    You can have good fun with phase, but you can't turn mics willy nilly into M/S.
     
  8. TheJackAttack

    TheJackAttack Distinguished Member

    Flipping the phase is coincidental (pun) to the mono compatibility. Other coincident stereo techniques can also generate mono compatibility.

    In order for the M/S to work properly, the microphone capsules have to be as close as possible. It is very very difficult to get three cardioid mic's to work properly without normal phase issues. Also, if you are using three separate mic's you will not flip the phase on any of them. You will just combine the proper tracks together.

    Bottom line: your playing with the phase in your mixes is not the same thing as the M/S stereo technique.
     
  9. IIRs

    IIRs Well-Known Member

    Yes they do. A lot of TV sets are still mono. Ditto small bedside / portable radios. AM radio is all mono. FM radio goes mono when the signal is weak.

    I've been recording live sessions for Radio Sheffield recently: I give them stereo mixes, and they broadcast in stereo, but if I stream them from the BBC website they come out resolutely mono...
     
  10. IIRs

    IIRs Well-Known Member

    I don't think this is quite correct. As I understand it a figure of 8 capsule is just a single element, but one which measures the pressure difference between the front and back of the diaphragm, rather than just the air pressure hitting the front as in a pressure transducer.

    A dual element mic with switchable patterns acheives its cardioid pattern by mixing the pressure transducer's output (omnidirectional) with the pressure gradient transducer's output (figure 8), so that the negative lobe of the figure 8 capsule cancels out the rear pickup of the omni.
     
  11. TheJackAttack

    TheJackAttack Distinguished Member

    Yeah, I was trying not to get into too much depth.

    A ribbon figure of 8 does operate slightly different than a multi capsule condenser figure of 8. I'm not sure whether there are any true single capsule condenser figure of 8 microphones.

    I figured the image of a ribbon would be the easiest to grasp. For the same reason I left out dual ribbon mic's.

    Also, I didn't even want to whisper about blowing across a ribbon.
     
  12. Guitarfreak

    Guitarfreak Well-Known Member

    No actually it is rather subtle, it just stopped the muddyness in the low end and the cab buzzing is less audible. Neat trick :D I can post clips if you'd like?

    No I understand that completely, this thread just went a different direction when we started talking about phase, then other things came up... have I mentioned that I'm obsessive compulsive? :-?

    And then I started asking for mixing advice to take this song to the next level. So, how would you do it?
     
  13. Guitarfreak

    Guitarfreak Well-Known Member

    OK I got bored of waiting so here's the sound clips.

    First playing around with phase.

    http://soundclick.com/share?songid=7841631
    http://soundclick.com/share?songid=7841632

    Next, tell me if the melody track fights with the rhythm track or if it's just my speaker system being silly.

    http://soundclick.com/share?songid=7841636
     
  14. TheJackAttack

    TheJackAttack Distinguished Member

    You'll have to wait a little longer. I'm not anywhere near my speakers. I'm smack dab in Yellowstone. Someone will comment soon enough.
     
  15. RemyRAD

    RemyRAD Well-Known Member

    Your speaker system is as silly as your clips. You can get many kinds of different stereo affects utilizing 2 microphones. Sure, you can record a MS pair, playing them back as left & right. That's stereo. You can also properly decode the MS pair utilizing a console or within software. Most software includes MS decoding presets. If you do this on a console, be it analog or digital, the side microphone channel must be split into 2 inputs. One is panned left and is in phase. The other input is panned right and is a phase inverted. When you listen to this by itself, it presents a solid out of phase Mono signal to both channels. If you collapsed this, while monitoring, to mono, the signal will electrically cancel out & disappear. While monitoring in stereo, you bring up your Middle microphone, panned to center. When you bring this up, it will cause cancellations in the left Channel & the right Channel and will present itself as a proper stereo image. By varying the middle mono microphones level, you can vary the stereo width. Even if you have a wide stereo image, monitoring this image in mono, will cancel both side microphone inputs. Try it. You'll like it. It's different. This is why it's known as completely mono compatible. The side and microphone completely disappear as and you hear only the middle microphone.

    By monitoring your MS signal as separate left & right channels they will be neither in phase or out of phase. You will however be 90° & 270° apart which gives you a rather random sounding stereo image as you have demonstrated. Depending on the application it can be either pleasing, as you have presented, or completely awful and amateur like depending on signal source.

    When mixing multiple microphones, flipping phases can work for you or against you. As in things will be in phase in front of you or appear out of phase & behind you. I frequently invert phase on bass drums. This causes certain cancellations to occur when combined with the other microphones which are left in phase. This cancellation can be used to tighten up the sound of the drum kit. It can also present you with an entirely different bass drums sound than an in phase bass drum. But when you start flipping phase on microphones willy-nilly, you couldn't be playing with fire. Things will magically disappear if played in mono. If that happens, you've done something wrong. So generally speaking most professional engineers will frequently switch between stereo & mono to endlessly check the continuity of the mix. That's why many of our "old-fashioned" consoles usually had a " mono button". I have as yet to see a piece of software that conveniently allows this sort of monitoring selections. Particularly since the software has nothing to do with monitoring.

    Your guitar part sounds good regardless of phase because you are not decoding the MS pair. And switching phase on either microphone makes no difference. It is in the software you select a MS preset decoder, it will effectively a compilation in the software what I described we do with a physical console.

    When it comes to MS technique, I'm obsessively compulsive.
    Ms. Remy Ann David
     
  16. Guitarfreak

    Guitarfreak Well-Known Member

    Wow, now that's a post :D

    I am flattered that you liked my clips however I did not record this with M/S or anything close to it. I had the SM57 at the edge of the cone against the grille and the i5 3 feet away and I blended them to taste. I guess as you pointed out the phase is irrelevant in this case and was only luck that made this particular case sound good. Thanks for the info and comments :cool:
     

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