Using a Jecklin disc: just wondering

Topic: Using a Jecklin disc: just wondering (Read 5560 times) previous topic - next topic

0 Members and 1 Guest are viewing this topic.

Using a Jecklin disc: just wondering

2010-03-03 11:58:26

Hello all,

It has been quite a long time since I last visited HydrogenAudio, and things have changed. I now again have some time to spend on my favorite hobby, music! Since about a month I help with recording concerts of my classical music ... (sorry, I'm not a native speaker, but I sing in a choir, we have an symphonic orchestra associated. I'm not sure what word to use, but I hope you understand what I mean) Anyway, I now know a little bit more about recording, so I have a few questions.

I was searching for miking techniques, and I found this Jecklin disc, which I call "dummy head recording for speakers instead of headphones". There is not much information about this, some DIY manuals, but few comparisons with for example ORTF or A-B. To me using such a disc and adding a 3rd kind of stereo (seperation by coloration) seems better than any other stereo technique, as it uses all 3 kinds of stereo. I have seen some very positive comments, as well as quite negative. I wonder, why isn't this technique used more?

Second (less important) question: our budget is very restricted. Those discs cost about €200, not that much, but we just don't have that money. So I was looking for ways to build it myself, I found quite some DIY manuals, but which dampening material to use is not really clear, while it is very important. I have some polyurethane rigid foam left over here (http://www.puren.eu/industry-products/comp...ials/index.html) and I wondered whether a disc made out of this material (just foam, no hardboard/triplex inside as most DIY manuals suggest) would be a good dampener. Anyone suggestions?

Using a Jecklin disc: just wondering

Reply #1 – 2010-03-03 23:18:28

I am no expert. But from what I understand the disc itself should be solid so that it effectively blocks sound from the opposite side. The 'damping' is to prevent reflections from the disc entering the microphone on the same side, therefore, the damping should be soft fluffy stuff that you could blow through with out too much trouble. Any soft open cell foam should be ok, but if it is hard the is a chance of reflections. You could try old pillows or cushions, maybe even an old towel. You may need to experiment with different thicknesses.

Using a Jecklin disc: just wondering

Reply #2 – 2010-03-04 13:36:35

Well, the disc is not meant to isolate completely, it should function as some kind of low pass filtering above 200Hz, as the original paper says. It should color the sound coming from the other side by damping higher frequencies, just as a human head does, damping sounds coming from the right to the left ear. That means reflection should be as low as possible indeed, but the sound passing through should be damped in a certain way. It seems quite impossible to me to combine these two restrictions.

Anyway, I found something which could be a reason why this technique is not often used: you can't alter the stereo-image afterwards, according to Jecklins own white-paper on this subject. (which can be read here) I quote:

Quote

During the microphone test or the recording, level differences between the two channels must not be balanced out. In the case of one-sidedness, the disc must be turned or rearranged accordingly. A sound control in the conventional sense, balancing at the mixing desk, is not possible; i.e., the sound control is moved from the control room into the studio or concert hall.
(...)
Placing of the Jecklin disc before the sound source is less critical than microphone placement in the case of other recording techniques. Depending on the distance of the disc from the sound source, the recording sounds nearer or more remote without being automatically too close or of too large an auditory perspective. When the disc is being used, the optimum distance from the sound source is larger than it is the case of any other recording technique.

So, recording must be done right, there is no correcting afterwards. (though spot mixed can be mixed in if they are delay-corrected) Could that be a reason this is not used that much?

Using a Jecklin disc: just wondering

Reply #3 – 2010-03-04 15:06:36

I found some interesting material about a Schneider disc, which is a modified Jecklin. The last 3 paragraphs are most interesting:

Quote

If the room isn’t “right” the Schneider might not yield useful results. "You have to spend the time getting the room sound right first." says Saunders. "any good mics, like the omni Schoepps we used, will sound great. Obviously, good preamps will help up front too. In the mix, a little compression goes a long way in bringing out the details of a good stereo room track."

Using a Jecklin disc: just wondering

Reply #4 – 2010-03-05 21:18:07

I have built a DIY Jecklin, but have only experimented with it (I mostly record PA'd music and cannot always choose where I set up my mics). I created mine by cutting a piece of 1/2" thick MDF into a circle (using Jecklin's recommended size) and then gluing a matching size piece of foam on each side. I was initially attracted to the technique because it should provide a better sounding recording when played back on speakers compared to binaural techniques which sound best on headphones.

If you search, you will find alot of other DIY designs such as plexiglas sandwiched by mouse pads, etc. There are a few recordings you can sample if you search the LMA (Live Music Archive) on www.archive.org. There are some Jecklin recordings of classical available commercially too. Here is an AES article on the subject.

If you have the ability to place the Jecklin anywhere you want, you will be able to get very good to excellent results within your Hall. I think that is more important than the actual stereo technique. All techniques can yield stunning results when the recordist takes the time to place the mics where they sound best for that particular space.

Let us know if you build your own and please post your findings in the uploads forum!

John

Using a Jecklin disc: just wondering

Reply #5 – 2010-03-09 17:57:26

Ah, yes, well, actually we place mics now not by experimenting, as we don't have time. The guy who owns the mikes is really, really careful with them, so the stand is extremely well anchored to the ground before the mikes are actually placed on the stand, we never experiment with the placing. This had resulted in quite flawed recordings recently, as you never know how it sounds up there until you try. We're just a couple of audiophiles which do not really know anything about acoustics (well, to a certain extend of course) We usually place them about 4 meter high, 5 meter behind the director.

I just got a German book from one of those companions, which says Jecklin give 'ausreichend' directivity. (good enough, but not perfect) It says: the better you can pinpoint a sound-source (Lokalisation/Ortung), the worse the sense of space (Raümlichkeit, I don't know the best way to translate). They lined up the techniques XY, MS, ORTF, Jecklin, AB, from best sense of space (and worst localisation) to worst sense of space (and best localisation) I'm not entirely sure how this relation works: locating sound sources is quite a big part of sense of space, isn't it? Strangely, that book says it is a disadvantage a Jecklin-disc separates the high frequencies more than the low, but that is the whole idea of a Jecklin disc: a human head does exactly the same.

Using a Jecklin disc: just wondering

Reply #6 – 2010-03-10 08:22:36

If your placement options are limited to the location you describe, then I would suggest the ORTF, DIN or NOS techniques with cardioids. If the mics are higher than the ensemble, make sure to angle them down toward the center riser row. Optionally, a pair of omnis on outriggers outside of the cardioids will enhance the fullness of the ensemble.

If you can, use some sound-isolating headphones to monitor the ensemble's sound prior to recording (during rehearsal). You say that you place the mics by experimenting; that is the best way to achieve what you want. Otherwise you are leaving it to chance.

Have fun and let us know how it goes.

Using a Jecklin disc: just wondering

Reply #7 – 2010-03-18 07:17:56

Hi, there is a lot of material out there on "how to" and much by the inventor, himself, auf Deutsch wenn dass hilft eein bischen. I made one from an old LP covered with foam and then faux lambs wool. It works fine. I run it with the DPA 40006 TL's which it was designed with/for. I was not overly excited with the few tests I did with it and need to do more. If I can help you further let me know, offline is probably best.

Cheers/Tschuss

Using a Jecklin disc: just wondering

Reply #8 – 2010-06-29 15:31:09

Finally, I have done some experiments and I have some questions.

The idea of the disc is to absorb sound, in other words, as few reflections as possible, as reflections colour the sound. The original disc is a hard plywood disc covered with just a few cm of sound-absorbing material. As 2cm of damping material doesn't damp that much, still quite a lot of sound is reflected.

So I did some test and I think the disc colours too much. I tried quite some materials and came up with an idea. Very hairy stuffed toys reflect virtually no sound and absorb quite well, so why not make a disc out of that material, about 5 cm thick? It certainly isn't rigid enough to hold microphones, so you have to mount the mics directly at a stand instead of via the disc, but the disc should be able to support it's own weight.

Now I was wondering, am I missing things, is there another purpose for the plywood disc? Will a "Teddy-Bear-disc" work or do I overlook something?

Using a Jecklin disc: just wondering

Reply #9 – 2010-06-29 21:57:44

I'm skeptical of using something as hard as plywood, even with foam. Your "Bear disc" would probably work, though the conductor might object to the appearance. Try using a child's toy foam ball, perhaps an even better simulation of a human head. Experiment and find what works best for you.

A possible source for more information:

http://taperssection.com/index.php?topic=1...5566#msg1415566

Quote from: ktf on 2010-06-29 15:31:09

Finally, I have done some experiments and I have some questions.

The idea of the disc is to absorb sound, in other words, as few reflections as possible, as reflections colour the sound. The original disc is a hard plywood disc covered with just a few cm of sound-absorbing material. As 2cm of damping material doesn't damp that much, still quite a lot of sound is reflected.

Notice