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How to make a DIY parabolic microphone

 

Written in July 2021
This is a small DIY project/experiment that turned up very well, so I decided to share it.

Some theory first: "A parabolic microphone provides a natural mechanical amplification of about six times, due to the characteristics of the collector dish. The special shape of the parabolic dish collects the incoming pressures (sound waves) and focuses them onto a single point (the microphone)... The level of amplification is consistent over the entire area of the parabolic dish. The microphone will pick up some ambient noise from the rear of the mic, but the amplification provided by the dish makes the non-amplified sounds, coming from the back side of the mic, insignificant. The peripheral sounds outside the dish are not amplified and are blocked by the dish itself. This provides the directionality of the parabolic microphone." (BHPhotoVideo)

Parts that I used:

  • Radom plastic antenna shield - 44 cm diameter (cca 15 €)

  • 14 cm mic gooseneck with 3/8" screws (cca 6 €). Alternatively, a very short distance pole can be used to avoid gooseneck bending.

  • Mic clamp with 5/8" female to 3/8" female adaptor (cca 6 €)

  • 3/8" male to 5/8" female mic stand adaptor (cca 3 €)

  • Optional: 5/8" female to 3/8" female mic stand adaptor (cca 3 €)

How to:

  1. Screw the mic clamp to the top (male screw) of gooseneck

  2. Move the bottom of the gooseneck around the inner side of the dish to find the right spot where the mic clamp faces the middle of the dish

  3. Mark the ideal position of the bottom of the gooseneck

  4. Use a 3/8" driller (or a slightly smaller) to make a hole through the shield at the marked spot

  5. Screw the gooseneck to the dish with the 3/8" to 5/8" adaptor (you might also use some spacers)

  6. Optional: If the dish is moving or bending too much, use nylon thread to fix the edges to the tip of the gooseneck

  7. Now your parabole is ready to be mounted on a stand or a grip

  8. After mounting you should find a perfect spot where the microphone picks up the sound accurately and loud enough.

Tips:

  • The best option for me was to mount the parabole to a photographic stand which can be easily turned to any direction and which is very stable. That required adding 5/8" to 3/8" and 3/8" to 1/4" adaptors to fix it to the stand plate that has the standard photographic 1/4" screw.

  • I found using the mic clamp with a tightener useful because it holds any mic quite well and you can also clip a small lavalier mic (like Mikroucho or Clippy) on it. Also, you can easily adjust the distance between the mic and the bottom of the dish.

  • I decided to use a gooseneck to hold the mic clamp because it is lighter and thinner than the distance pole. If it's too loose and tends to bend, it can be fixed simply by taping any straight metal or wooden piece on it  to keep it straight. The gooseneck I used doesn't bend at all.

  • If the mount is too far from the spot (the spot is too deep in the parabole), the microphone can be inserted in a foam tube held by the mic clamp to make it closer to the bottom of the parabole (not pictured).

How does it work?

Long story short - it works great. I tried using it with various mics (dynamic, small membrane condensers, lavalier), and the amplification level is amazing. Of course, the low frequencies are less audible. Super easy, super cheap and super helpful.

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