DIY: A Jecklin Disk for Stereo Recording with Omni’s

What’s a Jecklin Disk?
A Jecklin Disk is a device that helps to record the most natural sounding stereo image that I have been able to achieve. It is a 12 inch circular disk with acoustically absorptive foam on both sides. Omni-directional microphones are mounted on both sides of the disk. The foam acts much the way your head works to block high frequency sounds from being picked up by both microphones equally. The sound is delayed as it tries to get around the disk and high frequency sounds are absorbed.

For instance, if there’s a sound coming from your left side, sound travels first to your left ear and then to your right ear. The delay that occurs between the left and the right helps us to determine directionality of the sound source. Additionally the sound gets partially absorbed by your head. So you get more high end sound on the side of your head that is closest to the sound source. The Jecklin Disk emulates this. Our friends at Mercenary Audio have a great version of the original article by Jürg Jecklin. (http://www.mercenary.com/opstsirewije.html) If you aren’t interested in making a disk yourself, you can easily order a really nice commercial model at Mercenary!

This is what a Jecklin Disk looks like in use with a pair of Earthworks TC25 omni’s:

Now that you know that you want one, but you don’t have $260 here’s how to put one together:

First step is to get out your trusty compass and set it for a 6″ diameter, which will create a 12″ circle. Compasses are really great for working with measurements and drawing circles in specific distances from the edge of a flat surface.

Stick the point of the compass as close as possible to the corner of a piece of 3/8″ nice-on-both-sides plywood and mark out 6″ on both the edges of the plywood. You can just draw an arc across the whole board if you want. I put the lines on the plywood already so you can see what I’m doing.

Next, you stick the point of the compass at the edge of the board where you drew the arc. This point is 6″ away from the corner. Draw an arc on the board where the center of your disk will be. Now move the point of the compass to the other point where your first arc intersected with the edge of the board and draw another arc where the center of the disc will be. Where these two arcs intersects is the center of your disk.

Now you can draw out your 12″ circle by pointing the compass in the center and making a complete circle.

Now it’s time for POWER TOOLS! Be sure to use hearing protection and eye protection. You never get you hearing back when it’s damaged. I prefer to use a saber saw (also called a Jig Saw) for cutting arcs and circles. You want to use a smallish blade with small teeth designed to cut wood, not metal.

Carefully cut the circle out of the plywood. Don’t worry about small imperfections in the cut because you will be sanding the edges smooth.

Now that you’ve cut the circle out of the plywood, take the rest of the plywood over to the table saw. We’re going to cut out 5 of squares of plywood to make the base of the Jecklin disk. These will all get sandwiched together to make the base that the mic stand threaded flange will attach to. Rip the first rectangle from the edge of the cut circle so that the disc will nestle perfectly in the base.

After cutting out all the little rectangles, you can see the odd one with the arc cut into it. This will be the middle piece of the sandwich.

Get your clamps, wood glue and blocks ready to glue together and clamp.

Glue is art. The glue is a abstract representation of the emptiness of the skulls of our nations leaders. After you get all the pieces together, clamp them after making sure all the pieces line up as smoothly as possible.

Go ahead and put the base aside to dry (give it at least an hour or so). Now go to the drill press to putting the mounting holes through the disc. This will be where you’ll mount two microphone stand flanges on either side of the disc. My drill press has lasers! Jealous?

After you get the disk drilled out and the base is dry. Go ahead and glue the disk into the slot in the base that you left with the arc cut out. Notice the two mic flanges on the table saw to the right of the disk. After the glue dries, you’re going to need to thoroughly sand the entire surface of the disc and the edges of the base as smooth as possible.

Fit self-sticking foam to the disc in preparation to attach it permanently.

After you have your foam cut correctly, you can go ahead and seal the disk with a few coats of Polycrylic, a latex version of polyurethane. Polycrylic is great for furniture that isn’t going to be walked on, but it really sucks for floors because its just not hard enough.

Notice that the wood grain is coming out more with the layers of clear finish.

After the Polycrylic dries, go ahead and attach the self-sticking foam to the disc and trim all the excess off with an hobby knife.

The last step is to bolt on the mic flanges through the disk. You will mount your mic clips onto the flanges.

Here’s a close-up of the base of the Jecklin Disk.

Now add a couple of omni’s and you’re good to go. Two omni’s on a Jecklin Disk, a few feet in front of a drum set, make for a wonderfully natural drum sound. A great inexpensive omni mic is the Audix TR-40, which sounds wonderful and almost as good as mics costing 5 times as much!

6 Responses to “DIY: A Jecklin Disk for Stereo Recording with Omni’s”

  1. John Says:

    Nice article! I have built a much simpler version.

    Can you post a short sample recording?

  2. ITD(II) – experiências in loco « oPus D Says:

    […] temos uma imagem do que foi feito, juntamente com um “disco” Jecklin improvisado (pois ainda estamos construindo um aqui em casa); este anteparo de espuma permite uma […]

  3. Boidnoise » Blog Archive » Wind in Black Bamboo Says:

    […] that was creaking and clacking in strengthening gusts.  I set up my home made Jecklin disc http://www.studiy.tv/?p=22 […]

  4. Bernhard Kroeger Says:

    Hi,
    just want to thank you for the simple and excellent plans for the Jecklin disc and the humor. Having fun with it and love the results.

    Barney

  5. Hendrik Gideonse Says:

    Thanks Barney. If you send me a photo, I will post it to the Jecklin Disk page…

    Best,

    Hendrik

  6. Goran Says:

    A nice one! Very informative. I will give it a go building something like this. I am curious to hear the results of this recording technique.
    Cheers!
    G

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