getting the least mic "bleed" with the mics I have
Old 29th November 2011
  #1
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getting the least mic "bleed" with the mics I have

I need some mic techniques/tips to help reduce bleeding between mics with the mics I have. When i record (myself) I do things separately (vocals and acoustic guitar) and have been doing this for years, but a friend has recently asked me to record him and was hoping I could get the same results I was getting for my self in his mixs. He insisted on playing his acoustic and singing at the same time and when it came time to mix it became a bit of a headache for me. I have the following mics:

1. Sm7B
2. pair of oktava 012 (1 omni head available)
3. Sm57 and Sm58
4. AKG 414 XLS (Just got her a weeks ago)

We were doing a vocal and acoustic track at once. I recorded him with an Oktava 012 (on his acoustic) and the SM7b (vocals) and that was all I tried. I didn't have the AKG 414 at the time. I know I can't completely eleminate the bleed but reducing it would help. I mainly want the vocal out of the miced acoustic so i can better edit the vocals. Thanks!
Old 29th November 2011
  #2
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Try the figure 8 pattern on the 414. A figure 8 has an extremely strong rejection plane - it is much stronger rejection that any other pattern.

If you can picture where the two pickup zones are (like two cones projecting out of each side of the mic diapragm), then you can picture the rejection zones in between.

Aim the mic on it's side, so one rejection zone is aimed at your mouth, and the other rejection zone is aimed at the floor. Obviously one pickup zone is aimed at the guitar - and the back of mic is aimed into the room.

I've even experiment with rubber-banding some felt or foam onto the back or the mic, to get a dryer room sound. Otherwise, make sure that the room reflections sound good - you might need to organise some diffusion - some convex panels could be good.

The SM7b is ideal for vocals and is pretty dry and upfront. So with this combination you can get rather good seperation of vocals and guitar. With a similar setup I was able to get sufficiently good seperation on a singer/songwriter chick I was working with that I was able to apply a chorus effect on the guitar without affecting the vocal, which may not be what you are going for, but was magic for her stuff.
Old 29th November 2011
  #3
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Thread Starter
Quote:
Originally Posted by Kiwi View Post
Try the figure 8 pattern on the 414. A figure 8 has an extremely strong rejection plane - it is much stronger rejection that any other pattern.

If you can picture where the two pickup zones are (like two cones projecting out of each side of the mic diapragm), then you can picture the rejection zones in between.

Aim the mic on it's side, so one rejection zone is aimed at your mouth, and the other rejection zone is aimed at the floor. Obviously one pickup zone is aimed at the guitar - and the back of mic is aimed into the room.

I've even experiment with rubber-banding some felt or foam onto the back or the mic, to get a dryer room sound. Otherwise, make sure that the room reflections sound good - you might need to organise some diffusion - some convex panels could be good.

The SM7b is ideal for vocals and is pretty dry and upfront. So with this combination you can get rather good seperation of vocals and guitar. With a similar setup I was able to get sufficiently good seperation on a singer/songwriter chick I was working with that I was able to apply a chorus effect on the guitar without affecting the vocal, which may not be what you are going for, but was magic for her stuff.
Thankyou for the suggestion. I have read about his technique before and could not for the life of me picture how to set it up but when you said turn the mic on its side it clicked! Oh man...sometimes its the littliest things. Much appreciated
Old 29th November 2011
  #4
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BTW is tipping the mic down so the top is 90 degrees perpendicular to the singer as effective as tilting the the mic on its side?
Old 30th November 2011
  #5
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As I understand it, the strongest nulling in the figure 8 pattern is in a plane that basically is the same plane as the diaphragm/s.

Typical condenser mics have two diapragms, and in figure 8 mode both are turned on but the rear one is polarity reversed. So any sound that hits both diaphragms equally will get completely nulled. With a ribbon, the nulling is acoustic rather than electrical but the same result. So if you think about the distance from the point source to each diaphragm - the distance is going to be equal anywhere along that whole 360 degree plane.

Experiment with some headphones, and it becomes clear where the nulling is strongest. I think mounting the mic on it's side is a tidy way to do it, because you can rotate the mic to any angle. If it's in normal upright position, you would have to tilt it probably 45° so the null plane is pointing to the singers mouth. It's more important where the pickup zones are pointing, so whatever arrangement works is good.
Old 30th November 2011
  #6
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Quote:
Originally Posted by fender4593 View Post
BTW is tipping the mic down so the top is 90 degrees perpendicular to the singer as effective as tilting the the mic on its side?
yep

the patterns are three dimensional, try to visualize it looking at the response diagram as if the diaphragm is standing up on the x axis with the front facing the top of the chart, back facing the bottom. now imagine the pickup pattern being circular as the diaphragm.

or you could better demonstrate and analyze this by simply hooking up your mic and speaking into it while rotating it around. should give you a pretty good idea of what the off axis frequency response will sound like as well, at least better than just looking at charts.
Old 30th November 2011
  #7
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Thread Starter
Quote:
Originally Posted by Kiwi View Post
As I understand it, the strongest nulling in the figure 8 pattern is in a plane that basically is the same plane as the diaphragm/s.

Typical condenser mics have two diapragms, and in figure 8 mode both are turned on but the rear one is polarity reversed. So any sound that hits both diaphragms equally will get completely nulled. With a ribbon, the nulling is acoustic rather than electrical but the same result. So if you think about the distance from the point source to each diaphragm - the distance is going to be equal anywhere along that whole 360 degree plane.

Experiment with some headphones, and it becomes clear where the nulling is strongest. I think mounting the mic on it's side is a tidy way to do it, because you can rotate the mic to any angle. If it's in normal upright position, you would have to tilt it probably 45° so the null plane is pointing to the singers mouth. It's more important where the pickup zones are pointing, so whatever arrangement works is good.

Thank you both and for the explanations..All makes much better sense. Ill give it a try tonight.
Old 30th November 2011
  #8
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Imagine it's like a torch, with two back-to-back lamps and reflectors. It's going to light up the room from the front and the back in two cones shapes (aka figure 8 or hourglass). There will be a zone of darkness where the light doesn't shine which is where you want the vocals to hide.
Old 30th January 2012
  #9
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Im trying to do the figure 8 separation of acoustic and vocals...really unclear without a drawing..mic on it's side like how? im also having a great deal of trouble with mic placement on the guitar as far a boominess. In order to reduce bleed the guitar mic needs to be near the sound hole rather than near the 12th fret (like when just recording an acoustic alone with a reg condenser). any help on the placement or other ideas? Im using 2 cadm179 mics switched to fig 8...the 2 mics are independently aimed at guitar and vocal with the non pick up points of the figure 8 pattern side by side to each other.. and about 2-3 feet from each other. thank you
Old 1st February 2012
  #10
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Quote:
Originally Posted by NoPro View Post
Im trying to do the figure 8 separation of acoustic and vocals...really unclear without a drawing..mic on it's side like how? im also having a great deal of trouble with mic placement on the guitar as far a boominess. In order to reduce bleed the guitar mic needs to be near the sound hole rather than near the 12th fret (like when just recording an acoustic alone with a reg condenser). any help on the placement or other ideas? Im using 2 cadm179 mics switched to fig 8...the 2 mics are independently aimed at guitar and vocal with the non pick up points of the figure 8 pattern side by side to each other.. and about 2-3 feet from each other. thank you
I have had really good success (since this post) using my 414 in figure 8 mode. I place it horizontally (on it side) with a slight downward tilt about 12- 16 inches from the acoustic and slightly above the guitar. This distance avoids the boom your referring to at least with this mic. I still point the mic around the 12th fret but hedging slightly toward the sound hole in term of angle. I use the Sm7B for vocals and get almost no bleed (there is always some). Most acoustic player/ singers tend to look down toward the guitar more often then not so the tilt basically makes the vocalist mouth project right into the side (dead part) of the mic. I personally play standing up which may be giving me some more separation.

lets put it this way. The vocal is separated enough that if I need to make a small pitch edit on the vocal I can do it without trouble which is what I want. If, however, big edits are needed. It just won't fly in my experience..probably better off separating the performance IMHO.
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