Blumlein Question

So if I’m recording with the Blumlein set up, do I need to set the pans to the hard right and left and switch the polarities like you do with the mid-side technique or is it something different?

The Blumlein technique only requires two figure of eight pattern microphones, placed as close together as possible (usually one right on top of the other), and angled at 90 degrees from each other, and angled to the sides of your sound source (the midpoint between the two capsule’s front should be aimed at the source).  It’s basically the same as the X-Y technique, but you are using figure 8 microphones for the Blumlein and cardioid pattern microphones for X-Y.  You do NOT want to reverse the polarity/phase of one of the microphones or channels.  With Blumlein, you get more room ambience since figure of 8 patterns pick up sound equally from the front AND rear of the microphone.  With X-Y, you get more of the source you are recording and less ambience since the cardioid patterns mostly pick up sound from the front.

Found this quick link for brief descriptions of stereo recording techniques, along with some photos and diagrams:

http://audio.tutsplus.com/tutorials/recording/6-stereo-miking-techniques-you-can-use-today/

So, if I understand you correctly. I just set the mics up in the 90 degree configuration and I do not have to worry about duplicating another channel and switching polarity.  Sounds great and easy.

Thanks again you are the best!

Yes, that’s correct.  If you use cardioid mics, it’s called the X-Y technique.  If you use figure of eight mics, then it’s Blumlein.

You’re Welcome…

One last question. . . sorry!

do you pan the two signals or leave them in the middle.  It seems that if you leave them in the middle, they just sort of sit there.  But I guess it’s the room ambiance you’re really shooting for anyway, right?

Thanks for your pateince and help.

It’s a stereo technique, so you want to pan them hard left and right in the mix to get the full effect.  Of course, if that’s too wide sounding for some reason, you can always tuck in the panning a bit more towards the center.  But, if it’s mono you want, just use a single microphone, and you won’t have to worry about alignment and phase issues at all.

OK, so I’ve been putzing around with Blumlein.  I’m trying a couple of Cascade Fathead mics.  When I look at the phase analysis of what I’ve recorded, sometimes it’s OK and other times it’s waaaay off and when I hit the mono switch, it sounds pretty weak.  Is this because my mics could be better aligned or is there something else going on?

Thanks!

It could be any number of things:

  • Theoretically, the capsules need to occupy the same physical space, but that’s not possible, so you have to get them as close together as possible.  That usually involves one microphone upside down directly on top of the other microphone (right side up).  The size of the microphone head/grill is going to determine how close the capsule can actually be to each other, which will then be a factor in the phase relationship of different frequencies.
  • How close your source is to the microphones can also make a difference in the phase relationship of different frequencies.  If you have a guitar, for example, and are very close to the microphones, then the relative difference in distance from one microphone to the other to different parts of the guitar will be greater than if the guitar was further away from the microphones.
  • Walls, floors, ceilings, and other surfaces cause reflections which will have phase interactions with the direct sound as well.
  • Those microphones are also very cheap for ribbon microphones, and I’m willing to bet that the frequency response varies quite a bit from one unit to the next, which is also going to cause problems.  With many higher end microphones you can buy “matched pairs” in which they find pairs of microphones whose frequency response and other characteristics are very closely matched.  With cheaper companies, you can often record the same source from the same distance at the same time into two of the same model microphone, and clearly hear the difference between them.

Basically, though, don’t use your eyes by looking at phase meters… trust your ears.  If things don’t sound right to you, move the microphones around.  Sometimes just a few inches can make a huge difference in the sound!  Position is everything!  Be aware of walls and other boundaries as well, and play around with different positions of the source you are recording as well as the microphones, until you find the best position for both.  Taking the time to set up microphones and find the best position will save you a LOT of time and headaches later trying to “fix it in the mix”!

Steve

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