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Jecklin Disk construction?
Old 14th February 2003
  #1
Gear nut
 

Thread Starter
Jecklin Disk construction?

Hello,

I'd like to play around with a Jecklin Disk between my Earthworks TC30ks for stereo recording, so I thought I might try to build one, instead of buying one, since I just want to try it out. From what I can tell, the basic requirements are the it's wood covered by foam, round, and about a foot in diameter. Anything else I should take in account? Or does it sound so bad I shouldn't even bother ? Does anyone actually sell them? I can't find anyone who makes them.

Thanks!

-Dave Wallingford
Old 15th February 2003
  #2
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Remoteness's Avatar
Where is Scott Dorsey or Mike Rivers when you need them...

Many recordists have built their own rigs. Various types of material can be used. What do you have laying around? All kinds of stuff have been used in the past; plywood, cardboard, sheet metal, PVC or other kinds of plastic, etc. It's really not that critical.

Even a couple of mouse pads can be glued to the above mentioned material instead of foam. It's all good. Try it out and see (hear) what works the best for you.

The AES Journal on stereophonic techniques had the original Jecklin paper. Josephson website has information on the topic too. Check it out here > http://www.josephson.com/tn5.html

Also check out Scott Dorsey's info called, "About Our Mics" > http://www.techwood.org/kludge/mikes.html

I hope this helped...
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Jecklin Disk construction?-jdisk.jpg  
Old 15th February 2003
  #3
Gear maniac
 

I always wanted to build one of them.

This thread got me interested again.
Old 18th February 2003
  #4
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cleantone's Avatar
 

I made a Jecklin disk to use with my TC30K's too! I laughed when I read that, I don't see TC30K's too much, only omni's I have though.

I used a 1 inch thick peice of Foam with sinthetic wool around it. I used cut bic pens to make a strap-on mount. I used it twice and decided that I would rather make another with a clamp for mounting. I haven't started it yet though. I recorded a couple live fusion bands close to the stage and the seperation was really only heard during applause. It would be a great tool for a choir or ochestra! Even a trio in the right situation.

Have fun, good luck.
Old 24th February 2003
  #5
Gear nut
 

Thread Starter
Thanks for info, guys! I finished 2 over the weekend. The pics are of the version with 1 inch foam. I also made one with 1/2 inch foam to see how it effects the center image. I haven't actually used it on anything yet, but just from messing around with it around the house, I quite like it.

-Dave
Attached Thumbnails
Jecklin Disk construction?-jecklin-1.jpg  
Old 24th February 2003
  #6
Gear nut
 

Thread Starter
also the 1" version
Attached Thumbnails
Jecklin Disk construction?-jecklin-2.jpg  
Old 25th February 2003
  #7
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Nice Job!
Old 25th February 2003
  #8
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Supposedly (from research I did for mine) the capsules should be centered and I think it was 8 inches apart from eachother to get the good 'image', 8" is from my head, it couls have been 6", think ear drum distance, the seperation is outta control through headphones. Also, it is said to be best completely round with the caps centered. I guess the way the high end would almost creep arounf the corners could be effected. It's all about the placement too anyway. I can't wait to try it on a trio with centered drums and organ (or guitar) left and bass right, thats ideal for this!!
Old 25th February 2003
  #9
Gear nut
 

Thread Starter
Yeah, I've been centering them on the disc, and just kinda using my head as a rough guide for the width. I've heard some stuff about the disc being round, but most that I've seen actually aren't. I put together a rough round one before deciding on that shape, and compared it against a rough version of the one I ended up with, and there wasn't enough of a difference to go to the trouble of cutting a 1' perfectly round disc. The rectangle with rounded corners fits a lot better in my mic case, too. Anyway, I know a round disc is the more proper way to do it - but when Jecklin first made his they were covered in lambskin, and I didn't have any of that laying around.

And yes, it sounds great on the headphones! heh Still sounds very good on the monitors, but the phones are really great. Similar to a binaural head, but I think I like it better. Cheaper, too! heh

-Dave
Old 25th February 2003
  #10
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PlugHead's Avatar
 

FWIW,

www.dpamicrophones.com

Lots of various info on mics and recording: hink there is a link to Jecklin disc, and the appropriate distances for the mics...
Old 12th February 2008
  #11
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wyndrock's Avatar
a jecklin disk, if i remember correctly, is a 35" disk, covered in absorptive material, with two spaced omnis, centered on the disk, 36" apart. the general idea of these measurements was that to have the acoustic shadow just right, you'd have to space the mics just so, and have the disk just so big around with the right material plastered to it.

i'm gonna make one with my naiant msh-1 pair. something small and cheap, so if i screw it up, i'm not out a bunch of money. can you buy a jecklin disk?
Old 12th February 2008
  #12
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Schneider disc fun in the woodshop

Link at DPA: Stereo Techniques

"two Type 4003 or 4006 omnidirectional microphones spaced 17.5 cm and a special acoustic treated disc with a diameter of Ø35 cm placed between the microphones"

I took some measures of my Schneider and this is what I found:

The disk is 35cm in diameter with a 17cm diameter ball in the center. The PVC disc material is almost 1cm thick. Foam approximately .75cm thick covers each side of the disc and ball. The picture of Core Sound's model is useful. The "ball" diffusor on each side is not perfectly half-round. It appears flattened some, kinda like a slice was sectioned out of the center before being glued down to the disc like roundish bubble.

Core Sound — Jecklin Disk and Schneider Disk microphone mounts

I don't have a woodshop so I bought mine from Coresound. I decided to get the Scheider instead of a Jecklin for it's "ball" diffusor. I use it with great success on orchestral, choral, large to small ensembles. The room and the mics have to be good. Close placement is needed because disc shadowing that generates a stereo image exists only inside the critical distance. For this reason you may need to raise the disc higher than you would, say an ORTF pair, to ensure that coverage from the front to the back of an ensemble is even.
Old 12th February 2008
  #13
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Old 12th February 2008
  #14
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boojum's Avatar
Using Jecklin's latest specs I built one from an old Oral Roberts LP. I covered it with 1/2" foam on either side using spray adhesive to hold it in place. I then got some synthetic white lamb's fleece and made a cover for the foam. I was using a pair of OKM II's to play with so I stuck them on the ends of a bar that passed through the spindle hole of the LP. Some bent wire elevated the mics and gave them the proper angles. Yes it works and works well. I am going to remodel it now for a pair of DPA 4006 TL's.

Jecklin is a good thing to have.
Old 12th February 2008
  #15
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What do these guys who sell it for over 200 and much more put in these disks: a 24/192 recorder? heh

Jesus, its just a board covered with wool.

And anyone can make one thumbsup
Old 12th February 2008
  #16
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Brand name thumbsup. ...and the engineers made some effort and the CEO has to get his cut. ...then there's marketing

...then they have to pay for the website, shipping, a two week vacation package to the azores, manufacturing, a maserati with all the trimmin's and the coke.. ...don't forget all the coke.
Old 12th February 2008
  #17
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Haha, makes you wonder how much is your recording setup REALLY worth!
Old 12th February 2008
  #18
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Omicron_9's Avatar
 

Hello,

Actually, I recently built a very nice one for about $25. in parts. I called a local glass shop, and ordered a 12" diameter, 1/4" thick cut of plexiglass: $10. I used the bottom half of a Shure mic clip, and drilled a mounting hole in the disk; the Shure clip is the perfect size. Can't recall the model, but it's the clip for the SM-81, et. al., $5. For the covering, I went to a local saddle shop and bought a saddle pad which is 12" round and hollow; in other words, two thick round fleece pads sewn together. I cut just enough of the seam to fit it (perfectly!) over the disk, and then re-stitched it. $10. I then attach it to a mic stand or boom or gooseneck, and position it between a stereo pair on a stereo bar.

There is a photo of mine in this thread:

https://www.gearslutz.com/board/remot...-cardioid.html

Cheap and effective. Try it!

Regards,
-0.9
Old 12th February 2008
  #19
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I´ve done my own disc as well. Not quite comfortably placing it in front of professional world class soloists, but then I seldom get to record those for major labels. My run is more like my local amateur orchestra, and then what counts is the result.

So, yes, if I had London Symphony orchestra hired for the recording, I would not hesitate to buy a ready-made Jecklin disc.

The diameter 35 cm is oddly close to a standard LP record. And lambs fleece used to be quite readily available -- I sort of believe mr Jecklin got an idea and simply took what was available around. This approach is generally a good start in my world, anything after that is mostly minor changes, and not always to the better. Because to my experience what is better is dependant on so many factors. All from what music I am recording, to the players and their instruments and the hall. And up to what ideal sound I am striving for. Listening and modifying on location is always needed, never have I been able to get the perfect setup on first try. So far at least.

Gunnar
Old 12th February 2008
  #20
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hughesmr's Avatar
Quote:
Originally Posted by boojum View Post
Using Jecklin's latest specs I built one from an old Oral Roberts LP.
That's some sort of sin, I'm sure. tutt
Old 12th February 2008
  #21
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zenmastering's Avatar
Here's a link to the Marion Jones/Roger Clemens version of the Jecklin Disc:

isomike gallery

Graemme
Old 14th February 2008
  #22
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stuntbutt's Avatar
 

Quote:
Originally Posted by zenmastering View Post
Here's a link to the Marion Jones/Roger Clemens version of the Jecklin Disc:

isomike gallery

Graemme
Holy moly.
Old 14th February 2008
  #23
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Old 14th February 2008
  #24
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boojum's Avatar
I loved what my hokey attempt at a Jecklin did for me. The big downside is what it looks like. People are quite used to seeing tube-like things with wires coming from them on stands. Small furry discs are another story. I do have to get that four inch extension so that my Oral Roberts Jecklin will work with the 4006 TL's and try some more recording. I think that is what Juerg had in mind. The mics, not Oral Roberts.
Old 27th March 2008
  #25
Gear maniac
 

Question c617's for Jecklin Disk?

Anyone with any experience or opinions on using a Josephson c617/mk221 pair with a Jecklin disk?

(Aside from the fact that Josephson sells both, and virtue of the Jecklin disk concept notwithstanding.)

At issue here is the high frequence rise, or lack of it, in the Gefell mk221 capsule. Jurg Jecklin's paper and common practice suggest a mic with high fequency rise. I believe the photo on the Josephson web page shows the former 606 series, which had a slight rise as well.

Assuming good hall acoustics, would ensemble size or proximity be a factor in your decision?
Old 28th March 2008
  #26
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I spent the $$ on a M-B disc (sold in the US by Core Audio) and the reason it costs $239 is that it is precision made of 1 inch thick plexiglass, the mounting angle is adjustable, it's easy to get the capsule distance correct, and thanks to the Rubbermaid cake container I found at Target, it should last a long time. I wanted THAT one because I really liked the results that Simon Eadon obtained with his Takacs Quartet CDs. From all my research I concluded that the surface material does make a difference in sound, and the M-B covering is 1/4-inch foam rubber.

As for rising HF I have had good results with Schoeps MK2S and DPA 4003/trapezoidal grills, which have a flat graph.

Rich
Old 28th March 2008
  #27
Gear maniac
 

Thanks, Rich.

In theory I would think that you shouldn't need any more HF response than you would normally need without the disk, since the unattenuated sound (same side) is still direct. In the diffuse field you would still need diffuse field response mics. The paper and discussion seems to imply a need for more than usual, which I have never seen the need for. Your experience here is helpful.

The foam rubber thing still seems odd, though I don't deny the results of others. Foam rubber should still reflect a noticable amount of sound in the upper/mid frequency range, as opposed to the spec'd fleece. You make me want to experiment with a more solid center plate, though. It seems that the M-B designers were more concerned about LF resonance than M/H reflection.
Old 28th March 2008
  #28
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Well I gave it a try. :P

3/16" aluminum disc as base
1" of sound isolation foam on each side
covered with fleece sleeve

I made mine from the common specs I found on the net. A 30 cm disc with the mics separated 16 cm. I've seen a bunch that have sizes all over the place. Can someone enlighten me as to how that works?
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Jecklin Disk construction?-6p7190033.jpg   Jecklin Disk construction?-7p7190028.jpg  
Old 28th March 2008
  #29
Gear maniac
 

The red sure makes a statement! A jecklin disk draws enough looks as it is.

In theory, the size of the disk will affect the amount of separation between the channels, or more precisely the frequency cutoff at which attenuation of the opposite side will occur. Lower frequencies will be picked up by both mics. As the frequency rises above the critical point, there will be increasing separation in the channels. Diffraction will also occur depending on disk design and frequency. Jurg Jecklin's original design has separation starting between 200Hz and 1kHz, depending on who you listen to.

A larger disk will allow greater separation at lower frequencies. Jurg Jecklin described in his paper OSS technique which he considered "optimal" stereo signal. I believe he updated the design more recently with a slightly larger disk. "Optimal" in this case is trying to approximate the human head in a quasi-binaral configuration. The follow-on Schneider disk improves the binaural-ness by adding a central sphere. Optimal in other cases may not replicate a binaural arrangement, as most classical recording presents more of a super-stereo "pleasing" arrangement or even a down-right manipulated sound-stage.

In theory, a larger disk will also allow greater separation between the mics, with greater phase separation, which is something I am playing with. I recently calculated a nearly 60cm disk, but I don't want to end up with an Iso-Mike. Varying the disk orientation to the mics can also vary the separation from certain directions.

I still can't find a good reason to need greater than normal HF response mics in a Jecklin disk, unless we are discussing a purely diffuse sound field.
Old 28th March 2008
  #30
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springer's Avatar
 

I used my Jecklin (KONG) for a bass baffle the other night - the little guy just keeps on givin!!! Kept most of the ride cymbal out of my re20.
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Jecklin Disk construction?-jen_mics.jpg  
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