Make: Noise — Discuss this article

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• Condenser Mics Need Power - Wiring Should Be Identical
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  This is a fun post. Binaural recording is a really fun technique, and while there is some good information in this post (Especially using a mannequin head), there are a few errors and oversights.
  
  First, Just to confirm, what other commenters have said, the polarity on the mics should not be flipped.
  
  Second, On the podcast video, Kip Kay ties the positive and negative leads together, effectively creating a two element monaural mic. Not only will this not create a binaural recording, but phasing issues between the two mics are going to cause negative effects, including flanging, and comb filtering.
  
  Third, condenser mics need a power supply to operate. Unlike dynamic mics, which effectively act as tiny generators, and need no power supply, dynamic mics are just variable capacitors, and will not create an electrical signal. Condenser mics have two elements; either two metallic diaphragms, or a single diaphragm and a static back plate, which act as the two plates of a capacitor. The air between the two plates is the dielectric, and varying the distance between the two plates, changes the capacitance, causing variations in Z. This is translated to an analog audio signal Without a dc power supply, these mics won't work.
  
  Another helpful note - While a mannequin head will work for a binaural mic, it really helps if the surface of the head is soft. The hard surface of a mannequin head causes unnatural reflections. The purpose of binaural recording is to recreate the natural human hearing experience, with recorded and played-back material. A human head is soft, and usually has hair. Both of these characteristics are important in recreating the natural experience, because the soft skin and hair act to dampen high frequency sound.
  
  Keep up the good work.

  Posted by Garritt on May 01, 2009 at 11:42:52 Pacific Time

• Condenser Mics Need Power - Wiring Should Be Identical
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  Hello, this Bill Byrne, author of the original article.
  
  Before Kip did the video, I built it both ways, with the wiring swapped, and with it identical. I found that swapping the wires produced similar results to the un-swapped wires. So, to correct what I wrote, I was mistaken in saying that it was needed to preserve the stereo image. I did not have any phasing issues.
  
  As far as needing a power source, the cheapo Radio Shack mic elements I advise to use in the article don't seem to need one for this application.
  
  wb

  Posted by painfulleginjuries on May 04, 2009 at 14:17:06 Pacific Time

• Stealth mic wiring
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  The article says to wire the two mic capsules out of phase. This is incorrect. Imagine the source of the sound is directly in front of the recordist. A positive sound wave hits both mics at the same time, and should be recorded as a positive signal to both left & right channels to preserve the centered position information. If the same sound is recorded positive on one channel & negative on the other, it will play back sounding diffused & impossible to locate left-to-right.
  The two mic capsules should be wired identically.
  Sounds arriving at the mics from off-center will hit each capsule at slightly different times (phase difference,) and also have their amplitudes affected by the recordist's head, and that's the information that, when played back, allows the listener to perceive position information.

  Posted by Glurpo on March 29, 2009 at 12:47:05 Pacific Time

• Stealth mic wiring
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  I think glurpo is right, although it says in the PDF:
  Here’s the trickiest part: in order to have
  the correct stereo image, the wires on 1 of the 2
  mic elements should be reversed. So, for one mic
  element, the red goes to a plug terminal, and the
  blue to the plug’s ground; on the other mic element,
  the blue goes to the second plug terminal and the
  red goes to the ground (Figure D).
  
  This sounds odd, i never wire my speakers that way.. Can you please post a correction for this?

  Posted by GoodSamaritan1982 on April 17, 2009 at 14:53:43 Pacific Time