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Jecklin Disk construction? Condenser Microphones
Old 24th September 2010
  #91
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Quote:
Originally Posted by NathanShirley View Post
>>>Kugel is ball or sphere which describes the pattern that the mic hears in.

Right, that's why I was assuming omni, which is also why with the 4 mic technique it gets confusing when it mentions ball and cardioid. I wondered if it meant two omnis in normal position, and two rear facing cardioids (with capsules as close to the omni capsules as possible- to pick up purely reflected sound).
Your assumption is correct. Two forward facing omni's with two cardio's facing the back, placed as near to one another as possible.

I don't understand what the "linearen Diffusfeld-Frequenzgang" means, especially as the B+K mic seems to have an optional extra for that. Could it be this: "for diffuse- or far-field recordings, the black protection grid adds an on-axis 6dB boost centered around 15 kHz." Or this: "an alternate nose cone that ensures true omni performance-even at the highest frequencies"? Both quotes are from:

Mixguides microphones DPA 4006 Field Test-Mix reviews the DPA 4006 omni mic in mixguides microphones
Old 24th September 2010
  #92
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Quote:
Originally Posted by boojum
The old Neumann U50 (?) had the same 50mm sphere
The Neumann (TL)M50 has a permanent APE-style construction, but from what I recall it's of 40mm and not 50. Am I right, Kjetil?


Quote:
Originally Posted by NathanShirley View Post
The two microphones must have a diffuse linear response. Optimally suited for this arrangement, the microphone 4006 of B + K with diffuse attachment (Black). The angular aperture is about 60 degrees (due to superelevation of the frequency response in the microphone axis)
They're not talking about the APE balls, they're talking about using the DD0297 black far field capsule grid. It gives a 6 dB boost at 15 kHz, rendering the mics frequency response flat in a diffuse field (far away from the sound source). When used in the free field (normal main pair distance) the result is increased treble content which can be really useful sometimes.

Edit: I see cyrano preceded my reply.
Old 25th September 2010
  #93
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Many thanks guys. This make perfect sense now.

And the only other question then is what the 60 degrees is refering to?

Google English-

Quote:
The angular aperture is about 60 degrees (due to superelevation of the frequency response in
the microphone axis)
Original German-

Quote:
Der Oeffnungswinkel beträgt rund 60° (Grund: Ueberhöhung des Frequenzgangs in
der Mikrofonachse)
Any ideas here? I'm almost finished with the disc construction. Tomorrow I'll be setting up at the rehearsal and doing a few test recordings, I can post pictures and audio samples for anyone interested. And then the next day I'll record in concert.

Thanks again for the clarifications.
Old 25th September 2010
  #94
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The problem you are having (as is the case with most "Muricans) is the literal translation. Nierenmikrofon" would literally be translated or described as a microphone with "kidney characteristics". This term is almost unnkown in the US literature on this topic. I only found it once where it was referred to in quotation marks. The US term is "cardioid". So, the suggestion that Mr. Jecklin makes is that one should use the "usual" omnidirectional microphones ("Kugelmikrofone" in the German text) together with two additional cardioid microphones that should be directed into the audience. This should result in a "broader" stereo panorama of classical (orchestral) recordings together with more "room", natural "reverbation" so to speak. The cardioid mics in this suggestion should be mounted on the same microphone stands as the omnidirectional mics. This setup can be regarded as an alternative to the "conventional" M/S microphone setup which is "usually" used to capture "room" when recording choirs and symphonic orchestras.
Old 25th September 2010
  #95
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Quote:
Originally Posted by NathanShirley View Post
Many thanks guys. This make perfect sense now.

And the only other question then is what the 60 degrees is refering to?

Google English-



Original German-



Any ideas here? I'm almost finished with the disc construction. Tomorrow I'll be setting up at the rehearsal and doing a few test recordings, I can post pictures and audio samples for anyone interested. And then the next day I'll record in concert.

Thanks again for the clarifications.
the angle refers to the distance between the mics (think of two speakers)
Old 26th September 2010
  #96
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Well that's what I was worried it might be referring to.

There seems to be a discrepancy between that, and the idea that the new disk specs call for two parallel omnis (with 0 angle between them). This is what is stated on Wikipedia, and I have read this here in the forum as well.

So is it parallel or 60 degrees?

I'll quote Wikipedia here-

Quote:
Jecklin's German from his script: "Zwei Kugelmikrofone sind mit einem gegenseitigen Abstand von 36 cm angeordnet und durch eine mit Schaumstoff belegte Scheibe von 35 cm Durchmesser akustisch getrennt."[1] That means: Two parallel omnidirectional microphones having a distance between them of 36 cm (14 3/16") pointing toward the front, separated by a foam-covered disk having a diameter of 35 cm (13¾").
Old 26th September 2010
  #97
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Teddy Ray's Avatar
 

Quote:
Originally Posted by NathanShirley View Post
Well that's what I was worried it might be referring to.

There seems to be a discrepancy between that, and the idea that the new disk specs call for two parallel omnis (with 0 angle between them). This is what is stated on Wikipedia, and I have read this here in the forum as well.

So is it parallel or 60 degrees?

I'll quote Wikipedia here-

it is angled.
Old 26th September 2010
  #98
0VU
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Quote:
Originally Posted by Teddy Ray View Post
The cardioid mics in this suggestion should be mounted on the same microphone stands as the omnidirectional mics.
The cardioid mics need not merely to be on the same stands, their capsules should be as close as possible to those of the omni mics, hence the suggestion in the paper that cardioid mics with side incidence capsules will be needed.

Quote:
This setup can be regarded as an alternative to the "conventional" M/S microphone setup which is "usually" used to capture "room" when recording choirs and symphonic orchestras.
Could you please clarify what you mean here? OSS4 doesn't sound or work like MS and I'm not aware of MS being the 'usual' choice of 'room' mic for recordings of orchestras and choirs but I might be misunderstanding your point.


Quote:
it is angled.
Could you you explain where this comes from?

My understanding (based upon a conversation with Jecklin in 1995 about his original disk and angles, and 15 years fairly extensive use of the various Jecklin and Schneider disks) of the 60 degree thing referred to in the specs of the revised* OSS (not OSS4) setup is that it refers not to the physical separation angle of the two microphones, which are now parallel (to each other and to the disk) but to the approximate stereo angle produced by the technique when a pair of DPA 4006 mics with the black (diffuse field) grilles are set up paralel to each other, capsules 36 cm apart, with a 35cm disc equidistant between them. The actual stereo angle varies with frequency due to the variation in mic polar pattern with frequency and obviously changes when different mics (hence different on-axis frequency responses and differently varying polar patterns) are used.

(* The original OSS spec (to which the commercial MB disc is manufactured) was for a 305mm disk, 165mm separation and 40 degree physical angle between two DPA4006/diffuse field grille mics.)

But I could be completely wrong (it'd be far from the first time!) and misunderstood the original conversation as my German isn't very good, though I did have a Swiss radio engineer translating for me at the time and, after a lot of listening to these disks, it sounds about right to me.
Old 26th September 2010
  #99
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Teddy Ray's Avatar
 

Quote:
Originally Posted by 0VU View Post
But I could be completely wrong (it'd be far from the first time!) and misunderstood the original conversation as my German isn't very good, though I did have a Swiss radio engineer translating for me at the time and, after a lot of listening to these disks, it sounds about right to me.

so if you are saying the original MBHO disc(of which I have one...!!) was manufactured with a 40 degree seperation between the mics, why then is it some vast leap to see a 60 degree angle between mics in the new version??

Do you read German? If so, you know *exactly* what im talking about. I was offering a literal translation. Not adding my own interpretation . heh. thumbsup

I have no horse in this race, and havent used OSS in some time. I was merely offering the translation.

Of course, if i'm wrong, im sure one of the local German gents will come along to bust my chops. heh
Old 27th September 2010
  #100
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Quote:
...it refers not to the physical separation angle of the two microphones, which are now parallel (to each other and to the disk) but to the approximate stereo angle produced by the technique...
That's good news, I sure hope you are correct here. No offence Teddy, it's just that I already built a disc with mount according to the parallel mic orientation, and I'd have to do some pretty nasty modifications to get the mics positioned correctly if they were angled out!
Old 27th September 2010
  #101
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Teddy Ray's Avatar
 

Quote:
Originally Posted by NathanShirley View Post
That's good news, I sure hope you are correct here. No offence Teddy, it's just that I already built a disc with mount according to the parallel mic orientation, and I'd have to do some pretty nasty modifications to get the mics positioned correctly if they were angled out!

no offense to me at all, hell if yall want to go against the correct german translation more power to you. thumbsup (Translated by me and verified by my very german mentor) as I said, I dont use the jdisc anymore, and don't have a horse in the race. make the cussed things out of a cheesecake and some duct-tape for all I care. heh
Old 27th September 2010
  #102
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You'd think maybe Jurg could just draw a sketch on the back of a napkin and post it here to end the speculation heh !
Old 27th September 2010
  #103
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It seems that the J-disc has evolved over time and may yet still evolve. This makes it difficult to define what is the "correct" J-disc. I understand that the distance between the mics has doubled since the original design. All this makes me think that the J-disc is not the result of some irrefutable engineering or physics laws but from constant experimentation and refinement by Jecklin, among others. Will the real J-disc please stand up.
Old 27th September 2010
  #104
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Quote:
hell if yall want to go against the correct german translation more power to you.
Ha ha, well I'm just trying to make absolutely sure which way it is before I go modifying what I've got now (which I will if I'm 90% convinced).

So far we have a fluent German speaker arguing for 60 degrees (and his German mentor) on one end. And on the other we have someone who knew Jecklin, and has lots of OSS experience (along with Wikipedia, for what that's worth) on the other end.

I've searched the internet as far as I can, and there isn't much info on the new specs (in English). But the 3 or so times I've found it mentioned, it states parallel, with no mention of 60 degrees. However, I was curious so I looked at Jecklin's German document and found mention of 60 Degrees, so I wanted to make sure. My Google translation would make me think Teddy is correct, as the mics being parallel doesn't come through (but how good is a computer translation anyway?).

So Teddy, here's my last question for you- "OVU" has offered an explanation for what "60 degrees" refers to (not being the physical angle of the mics). So, how do you translate this section?-

Quote:
"Zwei Kugelmikrofone sind mit einem gegenseitigen Abstand von 36 cm angeordnet und durch eine mit Schaumstoff belegte Scheibe von 35 cm Durchmesser akustisch getrennt."
Wikipedia translates it as-

Quote:
Two parallel omnidirectional microphones having a distance between them of 36 cm (14 3/16") pointing toward the front, separated by a foam-covered disk having a diameter of 35 cm (13¾").
And I'm sure the Jecklin Disk can be very effective in different arrangements, but I'm simply trying to understand exactly what Jecklin means here, and either confirm the English interpretation, or clear up some misinformation!
Old 27th September 2010
  #105
Gear Head
 

J-disc w/AEA stereo bar

Here's my DIY J-disc/AEA stereo bar design which allows me to easily adjust the distances and angles between the mics and the disc. The disc is notched to fit down over the bar. When mics are installed on the bar, their capsules are aligned with the center of the disc. (Note: the mic positioners shown in these pics aren't arranged for using the J-disc. They were already on the bar from a recent gig.)
Attached Thumbnails
Jecklin Disk construction?-p1010044.jpg   Jecklin Disk construction?-p1010045.jpg   Jecklin Disk construction?-p1010046.jpg   Jecklin Disk construction?-p1010050.jpg  
Old 27th September 2010
  #106
Exactly the same, but different

Quote:
Originally Posted by Teddy Ray View Post
The problem you are having (as is the case with most "Muricans) is the literal translation. Nierenmikrofon" would literally be translated or described as a microphone with "kidney characteristics". This term is almost unnkown in the US literature on this topic. I only found it once where it was referred to in quotation marks. The US term is "cardioid". So, the suggestion that Mr. Jecklin makes is that one should use the "usual" omnidirectional microphones ("Kugelmikrofone" in the German text) together with two additional cardioid microphones that should be directed into the audience. This should result in a "broader" stereo panorama of classical (orchestral) recordings together with more "room", natural "reverbation" so to speak. The cardioid mics in this suggestion should be mounted on the same microphone stands as the omnidirectional mics. This setup can be regarded as an alternative to the "conventional" M/S microphone setup which is "usually" used to capture "room" when recording choirs and symphonic orchestras.
Yes, I realize if something's exactly the same, it can't be different (it's just something I like to say when comparisons are being made between things)...but I'll use that oxymoron as a springboard for a technique that I have found to work quite well with orchestral and choir material.

Similar to the Jecklin + 'backwards' cardoids as discussed, I often situate an ORTF configuration in close proximity to the mannequin head mic that I use, only I point the cardiods forward rather than backwards, and this then allows for some interesting mixing possibilities. The cardioids are not in the shadow of the mannequin head, so they operate as ORTF. Moreover, the cardoids actually give me better rejection of audience / room sounds that a binaural mannequin head microphone can often pick up, so in this case, the binaural mic functions a bit like the 'modified Jecklin' configuration, only in such an instance, it's the mannequin head that gets more of the reverberant / audience perspective and the cardiods more of the direct perspective.

Of course, much depends upon placement and distance issues (and of course, the characteristics of the hall), but this approach can really present a very full sonic rendering.

If I can get permission to post some excerpts I will do so as I think the technique does work quite well. I suspect that were a BS-3D sphere used in lieu of a mannequin head, similar results would be achieved.
Old 27th September 2010
  #107
Gear Addict
 

Quote:
Originally Posted by boojum View Post
...All this makes me think that the J-disc is not the result of some irrefutable engineering or physics laws but from constant experimentation and refinement by Jecklin, among others...
I don't think people should fixate on this angling (40 deg vs 60 deg vs ...) between the mic bodies. There is no theoretical acoustical spadework underpinning that. It is really just the angling that is needed to achieve the desired intercapsule spacing - the more important parameter.

The angling will of course depend various factors: (a) length of the mic bodies; (b) attachment position of mic clips on disk; (c) how close you demand the capsules aligned to disk centre; (d) how squeamish you are for clips afixed too close to capsule (acoustic interference?), or, at other extreme, atop the xlr connector (less interference, but unstable?)

My original MBHO disk, now ca. 30 years old (albeit with a foam refurbish) needs my Schoeps Mk2s to take an inter-body angle of ca 30 - 40 deg. But a short stubby mic such as a Neumann KM 83 would need a wider angling.

Concerning the early evolution of the Jecklin disk geometry, I have a 1984 Hi-Fi magazine article (with photo's)* on Jürg Jecklin which gives the following info:

- 1st version: Disk diam. 28 cm. Mic spacing ? cm. quickly surpassed by:
- 2nd version: Disk diam. 30 cm. Mic spacing 16.5 cm. (<- basis of MBHO commercial disk)
- 3rd version: Disk diam. 35 cm. Mic spacing 21 cm.

This 3rd version was shown with a smart double-disk construction: two disks, with a gap of ca. 1-2 cm., adjoined by a centre axle. The double disk construction was not for acoustical reasons, but simply to permit a more convenient disk rotation (the mic stand now being attached to the central axle rather than to a choice of fastening points around the disk perimeter, as in the MBHO model.

Of possible interest also is Jeckin's book**
[Much cited equipment now of course outdated, but with 219 pages technical German to salivate on, Teddy :-)].
This has little on disk construction but many of examples of application OSS and its combination with other mic techniques.

* Hifi Video Test (Netherlands), 8, p62-63 (1984)
** Jürg Jeckin: "Musikaufnahmen" Grundlagen - Technik - Praxis, Franzis-Verlag GmbH (1984) ISBN-7723-6702-X
Old 27th September 2010
  #108
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Quote:
Originally Posted by Tom McC View Post
I don't think people should fixate on this angling (40 deg vs 60 deg vs ...) between the mic bodies. There is no theoretical acoustical spadework underpinning that. It is really just the angling that is needed to achieve the desired intercapsule spacing - the more important parameter.
I see your point about the capsule spacing being more crucial than the physical mic angle. But the angle differance in question is pretty large (60 degrees vs. 0 degrees). And these omni mics are pretty much all more sensitive to HF on axis (at least this is what I keep reading over and over). Of course I'm sure everyone else here has more experience/knowledge than I do, and I really appreciate the opinions, but I'd still like to know for sure if Jecklin is calling for parallel mics, or mics angled at 60 degrees.
Old 28th September 2010
  #109
Gear Addict
 

Quote:
Originally Posted by NathanShirley View Post
.....But the angle differance in question is pretty large (60 degrees vs. 0 degrees). And these omni mics are pretty much all more sensitive to HF on axis.....
but I'd still like to know for sure if Jecklin is calling for parallel mics, or mics angled at 60 degrees.
True, but many high quality omnis, when used without any special "beaming" nose cones, have a respectably modest, off-axis HF fall-off through the segment of say + /- 30 deg. And in any case, on the inner "disk flank" of each mic this HF fall-off is likely being dwarfed by that from the shielding effect of the disk - which after all is the whole raison d'être of a boundary plate.

I haven't been able to unearth any specific references where Jecklin or others have pronounced on the desired mic angles. But surely that would always have to be qualified with a mention of the mics involved? For example:

For Mic brand A, use angle X; for Mic brand B, use angle Y; for Mic brand B, with nose cone B1, use angle Z

FWIW however, I do have Dutch magazine article pics from 1983 and 1984 in which Jecklin himself has been "caught red-handed" using his disks :-). The 1983 pics had him with his 30cm/16.5cm version, and the 1984 pics - during a workshop he gave in Amsterdam - had him with his then "new" double disk of 35cm/21cm. In all pics there was clearly an angling of ca. 40 - 60 deg? between the mics. (If needed, I guess I could try to upload these....alas poor quality re-scans of a b/w paper photocopy of.original articles.)

I wouldn't agonize too long for bang-on-the-button perfection for your first JD. Once the mice in the garage have eaten the foam, you have to start anew to tune all the parameters anyway :-). And the JD is not the pinnacle of all techniques. My experience has been that, in a good hall, it's hard to make a bad recording, easy to make a good recording, but elusively difficult to make an excellent recording.
Old 28th September 2010
  #110
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These all seem like very good points you make Tom, thanks for the input.

In the mean time, I was just looking back over Jecklin's document, and noticed that there is actually a diagram which for some reason I completely missed before. Unless this diagram is incorrect, it clearly shows the two mics being oriented parallel to each other. I might be overlooking something here, but now I think I'm about 90% sure of Jecklin's intended angle (or lack there of).
Old 28th September 2010
  #111
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Quote:
Originally Posted by NathanShirley View Post
These all seem like very good points you make Tom, thanks for the input.

In the mean time, I was just looking back over Jecklin's document, and noticed that there is actually a diagram which for some reason I completely missed before. Unless this diagram is incorrect, it clearly shows the two mics being oriented parallel to each other. I might be overlooking something here, but now I think I'm about 90% sure of Jecklin's intended angle (or lack there of).

There is more than one Jecklin document out there. Maybe he is just excercising his Swiss sense of humor on us. Could be.
Old 28th September 2010
  #112
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Teddy Ray's Avatar
 

Quote:
Originally Posted by NathanShirley View Post
These all seem like very good points you make Tom, thanks for the input.

In the mean time, I was just looking back over Jecklin's document, and noticed that there is actually a diagram which for some reason I completely missed before. Unless this diagram is incorrect, it clearly shows the two mics being oriented parallel to each other. I might be overlooking something here, but now I think I'm about 90% sure of Jecklin's intended angle (or lack there of).

here are some pics of my early *official* JD. clearly angled. not paralell...the mounts were fixed at that angle. OOPS! sorry for the extra pic. wrong pic attached
Attached Thumbnails
Jecklin Disk construction?-oss-1.jpg   Jecklin Disk construction?-studio-1.jpg   Jecklin Disk construction?-oss-2.jpg  
Old 28th September 2010
  #113
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The document I have referred to was published in 2003.
Old 28th September 2010
  #114
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Quote:
Originally Posted by NathanShirley View Post
The document I have referred to was published in 2003.

anyway, i think you are getting too wrapped up in the particulars.

just use it and adjust to taste.
Attached Thumbnails
Jecklin Disk construction?-jdisk.jpg  
Old 28th September 2010
  #115
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eh, what is the right size for that plastic ball at the end of the string? Should the string be of cotton or what?

:-)
Old 28th September 2010
  #116
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Quote:
Originally Posted by Petrus View Post
eh, what is the right size for that plastic ball at the end of the string? Should the string be of cotton or what?

:-)

ive always wondered what that string is for. what is it?
Old 28th September 2010
  #117
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Jecklin Disk construction?

Quote:
Originally Posted by Teddy Ray


ive always wondered what that string is for. what is it?
The string is for positioning the microphones and the balls stop it being pulled through.

So - pull the string out and adjust the mic. so the string touches the front end. Then pull it through and do the same for the other side.

It makes sure that the two mics are exactly the same distance from the baffle.

Simples. ;-)

Sent from my iPhone using Gearslutz
Old 28th September 2010
  #118
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Yes I think you have all made your point. I was simply following the specs as close as I could, and could not figure out for sure if these new specs called for 60 degree angling, or no angling at all. I figured it was worth making sure since I went to all the trouble building it to the new specs.

And yes Teddy, I'm well aware of the angling used in the "original" specs, but I'm not sure what that has to do with the "new" specs, which seem to have been changed significantly, larger disc, much, much wider diaphragm placement. But anyway after seeing the diagram I am satisfactorily convinced that the mics are meant to be placed parallel to one another.

And one more thing- I thought you guys were supposed to be gear slutz?? But now all this "who cares about the details?" stuff! I mean it's not like I'm asking what the thread count should be for the faux lambs wool. Oh, and I just dug up an old thread from a year ago discussing the same angling vs. non-angling confusion... so it's not just me.

I do appreciate all the input though, so thanks again.
Old 7th October 2010
  #119
Gear Addict
"Zwei Kugelmikrofone sind mit einem gegenseitigen Abstand von 36 cm angeordnet und durch eine mit Schaumstoff belegte Scheibe von 35 cm Durchmesser akustisch getrennt."

... would translate into English as:

Two omnidirectionalmicrophones arranged with a distance of 36cm between each other and acoustically separated by a foam covered disk of 35cm in diameter.
Old 7th October 2010
  #120
Gear Maniac
 

Could jecklin disc users tell us what distance is usable ? 16,5cm, 21 cm or 36 cm ?
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