Figure 8 mic

Discussion in 'Microphones (live or studio)' started by Makzimia, Jan 28, 2017.

  1. Makzimia

    Makzimia The Minstrel Well-Known Member

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    Hi guys,

    Not sure how it really happened, but I've never added a figure 8 capable mic to my locker. Still love my original At4033a and my original NT2 Rode. Now I've another Rode, NT2a. Looking forward to testing this as a room mic for acoustic guitar.
     

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  2. audiokid

    audiokid Chris Staff

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    My figure 8 experience is limited to a few. Royer's are great mics. If you can afford them, they will definitely make you happy. Rode K2 is a sweet mic as well.
     
  3. audiokid

    audiokid Chris Staff

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  4. Makzimia

    Makzimia The Minstrel Well-Known Member

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    I put the NT2a through the MOTU turned on its side for figure 8. Recorded my singing and the 12 string. I then layered that with my at4033a nearby directly at me sitting half down between my voice and guitar. The result is the fullest live sound I have yet achieved. I also reverse phased a copy of the NT2 capture per advice I had seen. Panned hard left right, lowered below the at4033a take. That provides the ambient take. It wasn't perfect because I can hear my breathing when not singing even at a foot and a half away. Less hot signal will sort that out I'm sure.

    The point is though, after worrying about no longer having my Orion/RME and the RC500, I'm no longer concerned. The Traveller MK3 is doing a great job, for me.
     
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  5. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

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    I have a pair of KSM44 and pair of Fatheads. Figure 8 opens for great posibility. The side rejection is great...
    When you try M/S or blumlein, it's kind of a revelation that not only the front of the mic has great content.
     
  6. Makzimia

    Makzimia The Minstrel Well-Known Member

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    IMG_1165.JPG
    The business end :).
     
  7. Boswell

    Boswell Moderator Distinguished Member

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    You should find that setting them up as an M-S pair gives you greater control of the sound and the width. With reference to your photo above, I would normally mount the S-microphone upside-down vertically above the M-microphone in order to minimise the vertical separation of the diaphragms. Leaving an appreciable gap between them opens you up to phasing artifacts on sounds that have a significant vertical component such as floor and ceiling reflections.

    The NTR looks a lovely microphone, and I, too, would love to get my hands on one to try.

    Don't forget that you can't use a ribbon (velocity) microphone and a condenser (displacement) microphone as an M-S pair.
     
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  8. Makzimia

    Makzimia The Minstrel Well-Known Member

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    :oops: Thanks Bos, I hadn't tried it that way yet, I was just so excited to even try this. And honestly, it was just so much better even this way, than past attempts. When I did record the Minstrel and Marie the NT2 (not NT2a) was placed upside down on top of the Blue bottle I had at the time. I'm still learning more, nice to be able to tap greater minds on it :).

    Oh and, as I suspected, that is in fact how Bob Sell, guy I saw way of doing it, does it... I just didn't go back and look at his video again...
     
  9. Makzimia

    Makzimia The Minstrel Well-Known Member

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  10. Boswell

    Boswell Moderator Distinguished Member

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    Looks good.

    The other thing I meant to say in my post above is that I try, whenever possible, to mount both microphones on the same stand rather than different stands. The idea is to minimise the separation distance between the mics being modulated by vibration or other movement. It's probably less important when set up in a studio with good, solid floors than on a live stage with musos clomping about, but it can bring about mechanical stability concerns with heavy microphones.

    I often use a Beyer M160/M130 pair of ribbons for M-S recording. These are neat, featherweight units where there is no trouble using them with a spacer mount on a single-stand. On the occasions where I've put up a pair of NT2-As, whether in M-S or one of the stereo configurations, I always have to think carefully about the mechanical stability, and not hesitate to bring out the sandbags to weight the base of the stand.
     
  11. Makzimia

    Makzimia The Minstrel Well-Known Member

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    I get that Bos, with just me though, and those are very solid beyer dynamic stands (heavy). I'll be fine, I'm sure. I appreciate you stepping in and pointing out my error though early. I did only one take, wasn't perfect, now I can move in the right direction totally, with what I have at least :).
     
  12. audiokid

    audiokid Chris Staff

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    Thank you for mentioning this, Bos. Can you please explain why?
     
  13. bouldersound

    bouldersound Real guitars are for old people. Well-Known Member

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    If I recall, it's the drastically different phase response characteristics.

    Generally speaking, I prefer two identical mics, like a pair of 4050s, though I've had good results from an iFet with a U47.
     
  14. Boswell

    Boswell Moderator Distinguished Member

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    A velocity microphone gives an electrical output proportional to how fast the diaphragm (ribbon) is moving through a field created by permament magnets. A displacement or pressure-sensitive microphone gives an output that is a function of the position of the diaphragm as it moves with the incident sound wave. If you draw a sinewave of pressure, then you see that the maximum pressure occurs at the peaks, whereas the maximum change of pressure (velocity) occurs as the wave goes through zero. These two are always 90 degrees out of phase with one another, at all frequencies. This means that if you put a ribbon microphone and a condenser microphone side-by-side in a sinewave sound field, the two outputs you get will be permanently 90 degrees out of phase as you sweep the frequency over the audio band.

    The equations for resolving the outputs from an M-S captured field into L-R component signals implicitly rely on the phase responses of the M and S microphones being the same. They simply do not work if you use a pair of microphones that are always 90 degrees out of phase with one another.

    As an example, if you were to take a correct M-S pair and put an acoustic sinewave source at 45 degrees left of centre, you would get outputs from the M and S microphones that were identical in both amplitude and phase. If you were now to move the sound source from that point through centre to 45 degrees right, you would see the M output increase in amplitude by sqrt(2) as it went through centre and then decrease to the original amplitude as you got to the 45 degrees right position. By contrast, the S output would reduce, go through zero and come up again 180 degrees out of phase (inverted) compared with the starting position.
     
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  15. audiokid

    audiokid Chris Staff

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    Thank you, Bos. You are the best. I'm going to include this as a reference to M/S micing. What would we title it as?
     
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  16. rmburrow

    rmburrow Active Member

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    The attached pdf from Georg Neumann GmbH has its origins many years ago and directly explains the M-S sum and difference method. I don't believe there are any other copy right restrictions on it. I haven't used M-S much; I prefer the matrix transformer method. An op-amp matrix can be built for a lot less money than a transformer matrix. The schematic of the transformer matrix explains the derivation of the sum and difference components (and their reconstruction).
     

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  17. John Willett

    John Willett Active Member

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    If you want to learn about MS - THIS is probably the defining paper on the subject:

    "M-S Stereo: A PowerfulTechnique for Working in Stereo"
    By: Wes Dooley and Ron Streicher

    It's excellent and highly recommended.

    I use MS a lot, though the mics I use are the single diaphragm Sennheiser MKH 30.
     
  18. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

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    Forget my ignorance or limited english understanding but figure of 8 microphones need to have dual diaphragm. One to capture the front and one the back sounds of the mic. So to be a figure of 8 mic the MKH30 must have 2 diaphragms. (of course in one capsule like they most do)
    Ok unless you have MKH that are not figure of 8.. it changes my assumption.

    So if I'm not wrong about this, using 2 MKH 30 don't qualify as M/S because the technic needs a cardioid and a figure of 8 and you use 2.
    2 figure of 8 would qualify for blumlein technic which is also great for capturing, but are you using it from the side of the array ???

    upload_2017-2-25_17-57-38.png then M/S : upload_2017-2-25_17-58-5.png
     
  19. John Willett

    John Willett Active Member

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    Oh dear - I'm sorry - you are completely wrong.

    A figure-8 microphone is a pure pressure-gradient device and only needs a single diaphragm.

    The original figure-8 microphones were ribbons with a single ribbon diaphragm and the best condenser figure-8 microphones have just a single diaphragm.

    Speak from the front and you get a good signal - speak from the rear and you also get a good signal, but polarity reversed - speak from the side and the sound pressure is equal both sides of the diaphragm and you get no signal - hence a figure-8 pattern.

    This is the best figure-8 as the front and rear are captured in the same place.

    A switchable-pattern microphone has two cardioid capsules. They have two separate diaphragms back to back.

    If you add the two together you get an omni - if you only use the front you have cardioid - if you subtract the rear from the front you get a figure-8.

    The best figure-8s have a single diaphragm: Sennheiser MKH 30, Neumann AK 20, Schoeps MK 8, etc.

    But some manufacturers find it easier to stick two cardioid capsules back-to-back to make a figure-8 as they can use the same basic capsule as they use for a cardioid mic., but this method is not as good as having a single diaphragm.

    If you look at the polar-pattern of the MKH 30 and compare it with any dual-diaphragm figure-8, you will see how much better it is, as having a single diaphragm is far more accurate - with separated diaphragms the high frequency polar response is not so good.

    Probably the best dual-diaphragm figure-8 is the Microtech Gefell UMT 70S which, although it has two diaphragms, only has a single backplate - so the two diaphragms are closer together than microphones that use two cardioid capsules back-to-back.

    The Gefell uses the Georg Neumann M7 capsule, which is the only dual-diaphragm capsule I know of that has a single backplate. These are more difficult to manufacture as front and rear responses have to be the same - it's easier to make separate cardioid capsules, match them as pairs and use matched capsules front and back - but this then has two backplates and teh diaphragms are further apart.

    But the best method is a figure-8 with just a single diaphragm.

    I hope this all makes sense to you and you understand now.
     
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  20. John Willett

    John Willett Active Member

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    To answer your second point.

    The mid mic of an MS rig can be any polar-pattern you want - anything from omni to figure-8.

    Cardioid is the most popular, but you can use any pattern you want.

    The Dooley and Streicher paper I linked to above explains all this and shows the resulting stereo array using omni, cardioid and fig-8 as the mid mic.

    And Blumlein himself used two figure-8 microphones in MS rather than crossed many times aas you can steer the image in MS (see Dooley and Streicher paper).

    I hope this makes it clear.

    I have recorded MS many times, though my preferred rig was the Sennheiser MKH 40/30 combination - this clips together easily and can be fitted into a single mic. clip and even used outdoors in a Rycote basket wndshield.
     

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