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Jecklin Disk construction? Condenser Microphones
Old 28th March 2008
  #31
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big country's Avatar
 

that is a really nice disk


I'm in the process of designing a new binaural
its cool thats all I will say
Old 30th July 2009
  #32
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Leave it to me to bump a thread that's over a year old.

McMaster-Carr is your friend. They have everything, even 12" diameter circular disks of clear acrylic, .236" thick, already cut and ready to go.

McMaster-Carr

They also have it in .118" thickness.
Old 31st July 2009
  #33
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Hey Chris, nice find! I'm still looking for the perfect 12" circle to put on the plexiglass base I cut. What you found is Acrylic, which I wonder what the sound absorption is? I wish I could find plain black rubber about 1/2" thick and cut a circle out of it but I haven't seen anything like that.

Also, I think I've seen that the revised J-disc is supposed to be 13" round, not 12", and they only have a 12" and a 14" model. But I haven't cut a new piece of plexiglass so I'm okay but I'd like to get a more exact one eventually. Also that's a bit expensive, $16 each??
Old 31st July 2009
  #34
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Plastic/acrylic is not going to absorb sound. That's why you put on another layer of absorptive material. It would be interesting to find like 1" thick rock wool. Jecklin didn't have the Internet with which to research sound-absorption numbers. Maybe that's something to research.

Will you be cutting this material yourself? If so, it might be cheaper to cut some other material yourself (I don't know offhand what Plexiglas costs). This disk would be convenient for me who doesn't have a ready way of cutting a plastic circle. It's certainly cheaper than a $200 Jecklin disk.

I read that the size of the disk affects the frequency at which separation starts to occur. A larger disk results in a lower frequency. Do you think you could hear the difference between a 12" disk and a 14" disk?
Old 31st July 2009
  #35
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Plexiglass is super-cheap so if you know someone who has a scroll saw just buy some and a compass and have them cut it.

I don't know if you could tell a difference between 12" and 14" but I think Jecklin's revised specs was a 13" disc with about 13" separation between the mics. Check out the actual white paper sometime.
Old 31st July 2009
  #36
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I am running the revised Jecklin measurements in my setup: 17.5cm offset from the disc on each side and a ~35cm disc. I figure that the LP with the fake lambs wool is ~35cm. The lambs wool was added by NHK if I remember right. I used it because without it the disc I made is just plain butt-ugly.
Old 31st July 2009
  #37
0VU
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Quote:
Originally Posted by Corran View Post
I don't know if you could tell a difference between 12" and 14" but I think Jecklin's revised specs was a 13" disc with about 13" separation between the mics. Check out the actual white paper sometime.
The original spec was: 305mm (12") disc diameter, 165mm mic spacing with the two mics angled out at 20 degrees to achieve this (using DPA 4006 omnis).

The new spec is: 350mm (13 3/4") disc diameter, 360mm mic spacing with the two mics parallel (both pointing forward, no angling).

The mic capsules are also supposed to be aligned with the centre of the disc, which isn't quite as easy with the new setup as it was with the original.

The difference between the two disc sizes is definitely audible, albeit more subtle on some sources than on others, but throw in the more than doubling of the mic spacing recommended for the larger disc and it's pretty obvious on anything.
Old 31st July 2009
  #38
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Thanks for the clarification - I can't remember where I had read 13" but the more exact mm measuring is probably better anyway.
Old 31st July 2009
  #39
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I've got an order in to McMaster-Carr for the 12" plastic disk and two 12" squares of wool felt for my Jecklin DIY kit. From what I gather on their web site, the $250 Core Sound disk is likewise 12" in diameter. My disk will be slightly off the latest spec but I'm sure I'll be satisfied with it.
Old 31st July 2009
  #40
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Mine was giving off some comb-filter anomolies until I covered it in gorilla fur from the local JoAnns fabrics store. Just look for KONG on GS for more details.
It is a circle of 703 covered in felt covered in faux gorilla fur.
Old 4th August 2009
  #41
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I've been wondering whether mass/density of the Jecklin is a factor at all...wouldn't mass tend to absorb lower frequencies from travelling from one side of the disc to the other, by acting as a 'frequency sink' for LF sounds ? Surely the intention of the disc is to act as an acoustic shadow to prevent mid and high frequencies mixing and merging and washing out out the stereo imaging ? For those purposes I can see that lambs wool or fake fur would help in cutting down on diffraction effects and comb filtering,between each side of the disc independently and it's respective mic ? However I don't think that mass or weight per se is necessarily useful or desirable, since the shadowing occurs due to physical dimensions (disc diameter, and thickness of the disc) and to the distance between the source and mics, and I'm sure the width of the musical ensemble becomes a factor here too ? That said, I sourced some sheets of 5m cork floor tiles and cut and glued them to both sides of the plexiglass disc, and that seemed to deaden procedings without adding undue mass.... increased its width by 1cm also. Anyone care to comment about which factors are more relevant than others in the disc's construction ? Would more mass added to the disc simply make it more likely to transmit LF rumbles directly between the mics, since they share a common mounting rod ?
Old 4th August 2009
  #42
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First of all - don't mount them to the disk. Mine is just a baffle between the mics on a stereo bar - isolated.
Second I think the only directional frequencies it is designed for are HF. LF is non-directional (for the most part).
Old 12th August 2009
  #43
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Inspired by this thread and just for the sake of experimenting I'm going to make a Schneider Disk,

Core Sound — Jecklin Disk and Schneider Disk microphone mounts

I've just brought one of these,

1 x Large Solid Foam Ball (8") Football/Play Parachute on eBay (end time 29-Aug-09 09:12:21 BST)

I'm going to use 1/2" MDF and cut out a 13" circle with a 7 3/4" hole in the middle for the ball, cover the rim in foam and work out how to mount my 2 Naiant mics. I'm kinda making this up as I go along, but will update this thread with how I get on!
Old 12th August 2009
  #44
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Gonna need a pretty hefty mic stand to get that bad boy in the air...
Old 12th August 2009
  #45
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Quote:
Originally Posted by TornadoTed View Post
Inspired by this thread and just for the sake of experimenting I'm going to make a Schneider Disk,

Core Sound — Jecklin Disk and Schneider Disk microphone mounts

I've just brought one of these,

1 x Large Solid Foam Ball (8") Football/Play Parachute on eBay (end time 29-Aug-09 09:12:21 BST)

I'm going to use 1/2" MDF and cut out a 13" circle with a 7 3/4" hole in the middle for the ball, cover the rim in foam and work out how to mount my 2 Naiant mics. I'm kinda making this up as I go along, but will update this thread with how I get on!
I really hope you bought a truly gaudy ball for this! May as well make it known!
Old 12th August 2009
  #46
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Quote:
Originally Posted by Walling1 View Post
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
Here you have it

Regards
Attached Files
File Type: pdf osiskonstruktion[1].pdf (89.6 KB, 942 views)
Old 13th August 2009
  #47
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how to build your own jecklin disc
<http://www.klankschap.nl/ndotb.pdf>
Old 13th August 2009
  #48
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Quote:
Originally Posted by boojum View Post
I really hope you bought a truly gaudy ball for this! May as well make it known!
Oh yeah it's going to be bright
Old 13th August 2009
  #49
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Quote:
Originally Posted by hbphotoav View Post
Gonna need a pretty hefty mic stand to get that bad boy in the air...
It's being mounted on the wall in the hallway between the live room and the isolation booths. The hallway sounds great and I often put up some mics in there when I'm recording drums in the live room. It is a pain carefully avoiding mic stands in a major walk way though!

I have the ring covered in foam and the ball should arrive today, I'm getting some threaded rod to mount it to the wall and mount the mic clips tomorrow so hopefully will have pictures by the weekend/early next week.
Old 14th August 2009
  #50
Gear Head
 

Here are a couple photos showing the layered construction of a few Jecklins of various sizes I built a couple years ago. I used a multi-ply thick cardboard baffle (stiff, lightweight) with a layer of pile carpet (good mid damping) covered by a layer of felt moving blanket (eats reflected highs) and some faux-fur to kill wind turbulence since I used these outdoors. The photos show the layers for one side of the cardboard baffle, which are duplicated on the other side of course. I ended up with that combination by listening for reflections off the surface of the disk before & after adding each layer of material. I found embroidery hoops work well for neatly securing the layers of damping material and the rigid central baffle board and a strip of gaffer tape covers the hoop just for appearances. Stand or bar attachment is made at the clamp portion at the bottom of the hoop. I used oval hoops to try and get some increased separation from mic'ing position a bit farther back, and just because they look cool. Details and additional photos are in this thread over at Taperssection.com. (not sure if you need to register there to see the photos or not). [edit to add a photo of the larger disk before the damping layers were applied]
Attached Thumbnails
Jecklin Disk construction?-jecklin-layers-02.jpg   Jecklin Disk construction?-jecklin-layers-01.jpg   Jecklin Disk construction?-jecklin-disk-oval-01.jpg   Jecklin Disk construction?-jecklin-disk-oval-02.jpg   Jecklin Disk construction?-jeckin-disk-large.jpg  

Old 15th August 2009
  #51
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All done!

I used 12mm MDF covered with some spare 1" foam and a strip of carpet tile to cover the edge. The mounting bar is a piece from an old broken keyboard stand. The only thing I brought were the ball and the threaded rod so just over a £10.

The bars can easily be shortened or lengthened for different mics and also adjusted closer or further from the wall. The disk is 13", the ball is 8" and the mics are 360mm apart.

Any disadvantage to using thicker foam rather than 1/2" like the commercial models seem to use?
Attached Thumbnails
Jecklin Disk construction?-disk-front.jpg   Jecklin Disk construction?-disk-side.jpg   Jecklin Disk construction?-disk-under.jpg  
Old 15th August 2009
  #52
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boojum's Avatar
Quote:
Originally Posted by TornadoTed View Post
All done!

<snip>

Any disadvantage to using thicker foam rather than 1/2" like the commercial models seem to use?

We are counting on you to tell us.


Looks good. I may try one myself. I would go for a really gaudy ball, though. You have shown remarkable restraint. LOL
Old 15th August 2009
  #53
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So... how does it sound? I have a smaller (9") Jecklin-type device that I occasionally use with DPA 4061s out at 7" or so. It seems to work better in close than back in the room... could be related to the size.

I'd also be interested in just what part the huge reflector behind the disk plays (the wall). Seems like there will be a not insignificant amount of (would it be flutter?) echo slapping off that surface, with the mics being out 8-10" or so (it appears in the photos). Do tell!
Old 16th August 2009
  #54
Gear Head
 

Nice lookin'. One thing on the foam ball, some of the typical open-cell, unskinned foam balls block hardly any sound except extreme high frequency. Sonically they are similar to a big foam windscreen. If you want more of a damping or refractive contribution from the ball you may need a different foam. I say this after sacrificing myself for the good of all DIY inclined recordists by looking like a true weirdo hanging out by the ball bin in the toy store and holding each ball up to my ear to listen through the foam. I'm also a hit with the old women in the fabric store-ac after I old one clerk at the fabric store what I was doing, I got her listening through swatches and she tually found some good faux-fur for me.

Anyway, I selected a heavier, denser 7" skinned-foam ball (orange and purple small basketball) when I was making a sphere baffle with flush capsules to form a sort of DIY Schoeps KFM6/360, but in that case I wasn't concerned about surface reflections just maximal damping/shadowing by the sphere with minimal weight.

On the thickness of the Jecklin baffle-
After using mine I found the thick baffle was not a problem. In fact, because I found myself preferring slightly wider mic spacings and thinking in terms of the shadow effect of the baffle and the relationship between mic-baffle distance and baffle size, I considered using two smaller baffles spaced apart. That way I could keep the mic-baffle distance manageable and use a normal sized baffle with the wider A-B spread I wanted. I even considered using two separate, smaller baffles- conceptually splitting a normal Jecklin disk and moving each mic/baffle pair apart to get the desired spacing. That would also allow to play with angling the baffle. Most of wanting that additional spacing was related to not being able to place the mics as close as i'd like, since close is where the normal Jecklin seems to work best for me.

All that gets pretty far from the 'typical' Jecklin disk, but is conceptually closely related.. sort of like all the Decca tree variations.

As for the back wall-
I've placed baffles behind to limit rear reflections and I've been making some interesting 4 channel surround recordings using four DPA 4060s baffled for Left/Right and Center/Surround.
Old 1st September 2009
  #55
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I finally got the time to wire the mics to the mic patchbay in the control room. I had to feed the cables down a 20' x 2" cavity which took some new fibre glass rods and a lot of patience!

I tried it out on a quick recording session at the weekend and it gave me a nice stereo ambience to mix in with the drum kit, not the most hi-fi recording but certainly as good as I had hoped for this application. I will try it out some more as I have a 10 day session in the studio from next weekend.
Old 22nd November 2009
  #56
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Quote:
Originally Posted by 0VU View Post
The original spec was: 305mm (12") disc diameter, 165mm mic spacing with the two mics angled out at 20 degrees to achieve this (using DPA 4006 omnis).

The new spec is: 350mm (13 3/4") disc diameter, 360mm mic spacing with the two mics parallel (both pointing forward, no angling).

The mic capsules are also supposed to be aligned with the centre of the disc, which isn't quite as easy with the new setup as it was with the original.

The difference between the two disc sizes is definitely audible, albeit more subtle on some sources than on others, but throw in the more than doubling of the mic spacing recommended for the larger disc and it's pretty obvious on anything.
Is there any 'official spec' from Jecklin about the thickness of the disc...or does it really matter ? I'm guessing if I make one from plexiglas and then cover it in sheepskin it could get to be about 1-2 cms wide ? I wouldn't expect any edge diffraction effects from that sort of width.
Ray
Old 22nd November 2009
  #57
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I'm lazy...

I got mine from:

http://www.mbho.de/pdf/oss_discs.pdf

I believe those are the same ones that Len sells (Core Sound).

I *REALLY* like the Schneider disc I own, but it's not the kind of setup I use daily...


all the best,
ave.

PS: some nice custom made ones here in these posts!
Old 22nd November 2009
  #58
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Smile

Quote:
Originally Posted by avebr View Post
I'm lazy...

I got mine from:

http://www.mbho.de/pdf/oss_discs.pdf

I believe those are the same ones that Len sells (Core Sound).

I *REALLY* like the Schneider disc I own, but it's not the kind of setup I use daily...
I did the same as you - I have both the Jecklin and Schneider disks.

The nice thing about this method is that you can unclip the mics and use them for other things when not using the disks.
Old 22nd November 2009
  #59
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I have made both 30 and 35 cm disks with 17 and 35 cm mic spacing. From my experince so far I actually prefer the smaller one. The bigger one seems to loose too much highs to my taste. Smaller one with 20 cm mic spacing gives very nice stereo and balance for small ensembles and even organs.

On the bigger one I have fluffier fleece, this might also be the reason for lost highs.
Old 25th November 2009
  #60
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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
I somehow doubt that the reason for the extravagant over-the-top design is entirely scientific. I think as much as for sound quality the sheer shock value of rolling in with that apparatus must make a client feel that they are really getting their money's worth.

That said it is a high quality, beautifully designed set of baffles.

Too bad you probably could come away with a better recording simply by hand selecting various mics and patterns from that 'infinite' mic closet and trial and error at different placement points.

I think that for every engineer with a strong opinion about the best way to record something you will find 1000 others with stronger opinions as to why they are wrong.

Then again, you can just use a 25 dollar home-made Jecklin disc.
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