DIY directional microphone for DSLR

Made from a salvaged electret microphone, an earphone cable and 4€ worth of hardware store materials.

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I recently bought a new DSLR camera (a Nikon D5500). Now I can make video with it, and it's cool. Unfortunately, the stereo internal microphone is lame. You hear noises when focusing, zooming, pressing buttons, etc... So I looked for an external microphone. But I don't have 100$ to put in a microphone just for filming parties and bithdays.
Having an old cassette DV camera laying around, I tore it appart for the microphone and decided to built my own external directional microphone.

What and why ?

I wanted a directional mic. The most simple solutions are : directional electret mic, parabolic mic and interference tube mic.

Since I only have an omnidirectional electret mic and wanted something as compact as possible, I went for the interference tube solution.

How it works.

An interference tube is a tube with the mic placed in one end, facing the other, wich is open. From the open end, to the front of the mic, there is slots regularily spaced. These slots let the side and rear sound waves propagate in the tube. But inside, the waves have different path lengths from the slot they entred by to the mic. The result is that the waves cancel themselves.

The side frequencies that are filtered depend directly of the sloted part length.
f = 340 / length (length is in meters)

Interfacing the microphone to the camera.

The camera has a 3.5mm jack input. The internal circuitry is capable of driving standard electret mic. There is nothing special to do, it's perfect for me.

I simply soldered an old earphones cable on the electret mic and the plug goes to the camera. It works like a charm.

  • 1
    Step 1

    Take a PVC tube of approximately 14cm and 20mm of diameter. (All dimentions are approximate, I took what I had or were cheapest, nothing is exact, this is ALL guessing).

    Do a mark each centimeter for 10cm.

  • 2
    Step 2

    Cut the slots, and do the same on the other side. I did two cut with the hacksaw to make larger slots. I am not sure if this is usefull.

  • 3
    Step 3

    Cut an earphone cable so if makes approximately 20cm.

    Don't forget to tin the end. Join the right and left channels (usualy, brass color is GND and the rest is right or left channel)

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Enjoy this project?



stephen_m_rea wrote 08/04/2017 at 17:49 point

Thank you... Glad I Googled DIY DSLR mic.. The RODE and Schneiders look great $$$$$  but I can't wait to build my own..  Hmm I know there is an old stripped Canon Video Camera in the loft..... thank God !

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Rendell Valles wrote 07/31/2016 at 16:20 point

hello i am wondering can i use an old dynamic mic as the microphone for this build will it sound better?

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Muphins wrote 08/01/2016 at 17:24 point

Hi, I don't know sorry. The best thing to do would be to run tests with both dynamic and static mic. I guess it depends on the audio input of your device.

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ben biles wrote 09/04/2015 at 03:45 point

looking forward to instructions. want to have a go at making a mic for
my dslr :)

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Muphins wrote 09/04/2015 at 07:21 point

Hi, thanks for your interest, the mic comes from a salvaged DV camera so
I don't know its specifications like the frequency response. It has a
diameter of 6mm.

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