Topic: Baffled sub-cards question

[Jimna]

i poked around last night looking for the answer with no luck, can anyone tell me what position i want my caps according to the j-disc?  same as omni's (20-30*toe out and tight against the baffle)?  im planning to run these tonight for the bridge in harrisburg, love new trying configs.  im loving all the options the cap assortment these busmans give me too.


thanks for the help!

[KLowe]

I don't know the "Official" word...but I toe them out a bit also.  (point at stacks).  There is some info about better high frequency pickup with the toe out.

Where is DSatz? 

[Jimna]

I don't know the "Official" word...but I toe them out a bit also.  (point at stacks).  There is some info about better high frequency pickup with the toe out.

Where is DSatz? 

makes sense, but the more i toe out the farther i will get from the j-disc (small diaphragms).   how important is the distance from the j-disc?  i know omni's need to be close to get the desired image.

[RebelRebel]

They are placed about 165 mm apart (calculated to give the proper time difference between the two channels). The idea is that as frequency increases, so does the percieved seperation of the microphones.. At around 200 Hz, the microphones pick up the same but above this, frequencies are attenuated by the acoustic damping properties of the disc.

[Brian Skalinder]

how important is the distance from the j-disc?  i know omni's need to be close to get the desired image.

Same concept applies for subcards.  The subcard has a bit of rear attenuation, but the distance from the j-disc will still have a significant impact on your stereo separation.

[Jimna]

just the info i needed.  thanks fellas.  T's

[Jimna]

...to bad the actives arent ready for these yet, that would allow me to get maximum angle while still keeping them tight to the j-disc. 

[Gutbucket]

What they said.  Correct spacing is important.  

Of course many people deviate from the Jecklin standard, personally I prefer a bit wider spacing for more separation at lower frequencies but that becomes difficult because you either need to get closer to the source or use a larger diameter disk to keep the same angle between the edge of the baffle and the mics.  From what I've read, it seems Mr. Jecklin modified his technique latter in a similar way (spaing approx. 15" with a 15" in disk if I remember right). Going the other way, Moke's mini-jecklins need the mics closer to the surface for effective baffling given the small size of the baffle.

I've thought of using two small disks and spacing the disks apart to increase the low end separation to avoid needing a Kimber ISO-phone size monster disk.  Idea being to keep the angles right and the mic to disk space small enough to be effective with a small disk. Just another untried wacky idea for now - baffled A-B, I guess.

[Jimna]

my j-disc is 15" X 15" square.  maybe ill try a slightly wider spread and minimal angles.  maybe not, maybe ill just run the 165mm and as much angle as i can, which wont be much given the thickness of my j-disc.  humm, decisions decisions...

[Gutbucket]

Using a mic with a freq. response that favors diffuse-field recording will also help.

Excellent point.  The baffle seems to reduce a bit of the top end response to my ear vs the same mics without.

[Church-Audio]

Using a mic with a freq. response that favors diffuse-field recording will also help.

Excellent point.  The baffle seems to reduce a bit of the top end response to my ear vs the same mics without.

What the hell is that goofy guy wearing in your avatar I have wondered this for quite some time..

[Gutbucket]

What the hell is that goofy guy wearing in your avatar I have wondered this for quite some time..

A sound collection and amplification device.

I ran across him looking into the history of Alan Blumlein's work.  Blumlein's early radar research (which brought upon his untimely death by plane crash) lead me to a bunch of really interesting info on sound amplification and collection devices used to listen for approaching aircraft before the electronic era.  You may have seen photos of giant arrays of victrola-like horns pointing at the sky or the huge concrete sound reflecting walls and parabolas built in along the english channel designed to amplify and discern the direction of approaching planes.  Militaries also wanted portable units and that poor sap is just a hapless inventor type who had a great idea, but lacked the grounding in reality to build something that actually worked. 

I have a soft spot for those who actually try and follow through on with seemingly ridiculous ideas.  Years spent tinkering in the garage and dreaming up all sorts of cool stuff that I never have time to develop make me envious of those sorts that put so much effort into things that I would dismiss as totally unpragmatic.  I love the poetry in their eyes.  In a similar vein, here's my current desktop (linked from a recent desktop thread here, apologies for the size but it's all in the eyes)-

[Alexandru Petrescu]

Using a mic with a freq. response that favors diffuse-field recording will also help.

Excellent point.  The baffle seems to reduce a bit of the top end response to my ear vs the same mics without.

What the hell is that goofy guy wearing in your avatar I have wondered this for quite some time..

"1960 Maritime acoustic radar"... and others at http://www.oobject.com/category/incredible-listening-devices/

There exist acoustic amplifiers even for mp3 players.

[Gutbucket]

^^^
Nice find. Lots of even crazier headgear there!

 I also just like that he looks like some absent minded mad scentist in an over-engineered tinfoil hat.

[Alexandru Petrescu]

I also just like that he looks like some absent minded mad scentist in an over-engineered tinfoil hat.

Edit: sorry, results of further Internet searching may imply that inventor's name is Jean Auscher and he may be the one in the picture:
http://www.flickr.com/photos/47218773@N00/2335680028/  he seems to be famous in a well developped field (and life-saving during times of war) prior to arrival of electronic radars http://acusticaweb.com/index.php?option=com_content&task=view&id=86&Itemid=6