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golf ball as diffraction sphere for omni mics ?
Old 16th December 2011
  #31
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sonare's Avatar
 
2 Reviews written
🎧 15 years
This urge to produce homemade APIs must be a virus sweeping the classical recordist community!

I looked into this to the point of sourcing acrylic and wooden juggling balls (NOT available singly), and also talking with a machine shop and then lost interest due to cost. Simon Eadon had some 40mm balls done several years ago but does not recall any details. But to all who really want the hole centered-- talk with a machinist about it- he will bring up a few things that impact his world-- such as drilling heat (you are talking about a LARGE diameter hole) etc.

Rich
Old 16th December 2011 | Show parent
  #32
Gear Head
 
panphonic's Avatar
 
🎧 10 years
Quote:
Originally Posted by fifthcircle ➡️
Ummm... really? Could have fooled me. The MKH20 has a rectangular body below the capsule, but the 8020 is quite definitely a cylinder. It wouldn't be able to screw together if it wasn't.

--Ben

Well, I stand corrected. For some reason I got the idea that they were slightly triangular, like a squashed cylinder, but maybe that was just the shape of the front grille or something. I havent used them for quite a while, and then only hired for a session, so I obviously did not pay enough attention!

J
Old 16th December 2011 | Show parent
  #33
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John Willett's Avatar
 
🎧 10 years
Talking

Quote:
Originally Posted by fifthcircle ➡️
Ummm... really? Could have fooled me. The MKH20 has a rectangular body below the capsule, but the 8020 is quite definitely a cylinder. It wouldn't be able to screw together if it wasn't.

--Ben
Yup - it's a short 19mm diameter cylinder.
Old 16th December 2011
  #34
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🎧 10 years
Doing a 20 mm hole in a wooden ball with a panel cutter bit is not all that difficult. First drill a guide hole all the way through with a smaller bit, then drill half way from each side, hone smooth to exact diameter with coarse sanding paper. Drilling heavy plastic might bring heat and melting problems, with wood a slight burn does not matter. Wood is light (lighter than most solid plastics), and the surface can be made as smooth as you want with paint, varnish, wax, you name it.

Some of you are making it sound more difficult than it actually is. You will not loose many bucks if you have the tools and just try it.
Old 16th December 2011 | Show parent
  #35
Lives for gear
 
🎧 15 years
If you value your time, (my hourly rate is high) you will just order the beautifully and accurately made balls from the respective manufacturers and save heaps of money. I am amazed that these threads exist? You spend hours mucking around with drill presses, bits, trying to cut slots the right size for O-rings, sanding, painting, all to save $100.

Just buy them and go out and do some recording!
Old 17th December 2011 | Show parent
  #36
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🎧 10 years
Quote:
Originally Posted by David Spearritt ➡️
If you value your time, (my hourly rate is high) you will just order the beautifully and accurately made balls from the respective manufacturers and save heaps of money. I am amazed that these threads exist? You spend hours mucking around with drill presses, bits, trying to cut slots the right size for O-rings, sanding, painting, all to save $100.

Just buy them and go out and do some recording!
Some people also have hobbies for their spare time, like small scale woodwork around the house... There is even a recent invention called a "vacation".
Old 17th December 2011 | Show parent
  #37
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John Willett's Avatar
 
🎧 10 years
Exclamation

Quote:
Originally Posted by David Spearritt ➡️
If you value your time, (my hourly rate is high) you will just order the beautifully and accurately made balls from the respective manufacturers and save heaps of money. I am amazed that these threads exist? You spend hours mucking around with drill presses, bits, trying to cut slots the right size for O-rings, sanding, painting, all to save $100.

Just buy them and go out and do some recording!
But Sennheiser do not make a ball for the 8020 and have no plans to do so - too much work for a small number of sales I guess.

So the only way is to make it yourself.
Old 19th December 2011 | Show parent
  #38
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🎧 10 years
Quote:
Originally Posted by panphonic ➡️
Well, I stand corrected. For some reason I got the idea that they were slightly triangular, like a squashed cylinder, but maybe that was just the shape of the front grille or something. I havent used them for quite a while, and then only hired for a session, so I obviously did not pay enough attention!

J
You're partially right, the top of the 8020 has a sort of 'wave' around the top, so instead of being a flat top on a metal cylinder it has 2 small peaks and 2 corresponding valleys. You can see it reasonably well here: Sennheiser MKH-8020 Compact Omnidirectional Condenser Microphone with MZX-8000 XLR Module - Microphones - Shopping.com and I think the MKH8040 is the same. In terms of lining up a sphere with the 'top' of the mic body I suppose it adds a little more variability, but not sure how important that is anyway (since the mesh cover sticks out above the barrel top as well ? The cross section of the mic body barrel itself is certainly cylindrical, not triangular.
Old 19th December 2011 | Show parent
  #39
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boojum's Avatar
 
1 Review written
🎧 15 years
Quote:
Originally Posted by studer58 ➡️
. . . I suppose it adds a little more variability, but not sure how important that is anyway (since the mesh cover sticks out above the barrel top as well ? . . .
My understanding is that the sphere must be flush with the microphone diaphragm. If the diaphragm is recessed in the barrel, hmmm, I wonder if the sphere would work correctly. I kind of doubt it. Look at the old Neumann M50 and that is plain: http://cdn-images.recordinghacks.com...50-capsule.jpg. DPA also stresses the "flush" aspect in setting up their spheres. See also Schoeps: Sphere Attachments KA*40 - Overview - SCHOEPS.de

As for what my time is worth, when I was working I was not paid when I was not working so my time would be free to tinker. I built some amps, a pre-amp and a tuner. At my "billing rate" it would have been cheaper to buy them built. But I enjoyed the job of "rolling my own" as it were. Self-employed would have meant "just about always on the clock" so that is different than a salaried job.

Last edited by boojum; 19th December 2011 at 09:20 AM.. Reason: additional thought
Old 19th December 2011 | Show parent
  #40
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🎧 10 years
Josephson SPB40 Baffle for the C617s - Interview at AES 2011 - YouTube

here is a video where David Josephson explains the problems with making such a sphere and size/frequency response issues etc.
Old 19th December 2011 | Show parent
  #41
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Bibster's Avatar
 
🎧 10 years
Quote:
Originally Posted by boojum ➡️
My understanding is that the sphere must be flush with the microphone diaphragm. If the diaphragm is recessed in the barrel, hmmm, I wonder if the sphere would work correctly.[/url]
(To me it) looks like your answer's here:
(Seeing the barrel pop through the ball)

Quote:
Originally Posted by amfortas2006 ➡️
here is a video where David Josephson explains the problems with making such a sphere and size/frequency response issues etc.
You forgot to introduce the obnoxious yes-nodder to to us! heh
Old 19th December 2011 | Show parent
  #42
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🎧 10 years
Quote:
Originally Posted by Bibster ➡️

You forgot to introduce the obnoxious yes-nodder to to us! heh
Don't ask...
Old 19th December 2011 | Show parent
  #43
nkf
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🎧 15 years
Quote:
Originally Posted by amfortas2006 ➡️
Josephson SPB40 Baffle for the C617s - Interview at AES 2011 - YouTube

here is a video where David Josephson explains the problems with making such a sphere and size/frequency response issues etc.
That is a good video (except of the interviewer of course). As already mentioned, I too cannot understand all this DIY motivation. And I expect the fit and size of such diffraction spheres very precisely measured and carefully manufactured for such a precise tool these microphones are.
Just read the article "A Pressure Microphone with Spherical Acoustic Surface" of Mr. Peus from Neumann, which you can find here:
Georg Neumann GmbH - Products/Current Microphones
If the shapes are not optimal all kind of 'effects' and weirdness can be 'achieved'.
This is a close up detail photo of one my own km133d with a sphere attached, it seems to me like a very precise fitting and the shape of the mic capsule is conical inside the sphere.
Old 19th December 2011
  #44
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🎧 10 years
AKG D109 omni had a clip for lavaliere operation
This could could produce a variable lip for the transducer and increase presence and mid band.
An elastic band around the top of a omni would have similar results.

My STC apple and biscuit 4021 from 1935 had a biscuit which diffracted HF
Nothing is new......
Old 12th January 2012 | Show parent
  #45
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🎧 10 years
Here is a quite detailed and studious Schoeps elaboration of the sphere/ball accessory, with helpful graphs showing it's effect on the pickup spectrum....as you'll see it's not just HF that's affected !
http://www.schoeps.de/documents/Scho...40_03-2008.pdf
Hope you find it interesting !
Old 12th January 2012 | Show parent
  #46
Gear Guru
Golf balls are too soft. Take one of those shaker "eggs" they give away at Namm. Cut it in 1/2. Take the non-pointed end, drill a hole in it, fit a rubber gromet and slide it over the mic.

That one was free.
Old 12th January 2012 | Show parent
  #47
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12ax7's Avatar
 
🎧 10 years
Quote:
Originally Posted by Rolo 46 ➡️
[...]
My STC apple and biscuit 4021 from 1935 had a biscuit which diffracted HF

Nothing is new......
Nope, nothing.

And yup, a pretty ingenious little device it was (especially for the time):
Just imagine the price you'd have to charge if you machined and assembled a mic like that today!
.
.
Old 12th January 2012 | Show parent
  #48
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🎧 15 years
Quote:
Originally Posted by studer58 ➡️
GS contributor 'd_fu' wrote about these items some time ago:
Just for the record, only the first sentence is mine, the rest was posted by JEGG. Original posting here...


As for the dimples on a golf ball, if you were to calculate what actual audio wavelength/frequency they represent, you'd probably find it is somewhere really high up there...
Old 12th January 2012 | Show parent
  #49
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12ax7's Avatar
 
🎧 10 years
Quote:
Originally Posted by Jim Williams ➡️
Golf balls are too soft. Take one of those shaker "eggs" they give away at Namm. Cut it in 1/2.

Take the non-pointed end, drill a hole in it, fit a rubber gromet and slide it over the mic.
That one was free.
Best DIY tip yet.

Thanx, Jim!
.
Old 13th January 2012 | Show parent
  #50
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🎧 10 years
Just musing on the "1/2 shaker egg" idea.... does it have to be a sphere at all, why not a hemisphere ? Isn't it the front half sphere (interfacing with the mic diaphragm) that's going to determine the directionality and mid/HF behaviour, not the rear half of the ball ? So why not indeed just have a half sphere..or would that flat circular face (looking backwards) tend to obstruct the incidence of 'rear of mic' sounds more than if it were curved (ie a full sphere) ?
Old 13th January 2012 | Show parent
  #51
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boojum's Avatar
 
1 Review written
🎧 15 years
Quote:
Originally Posted by studer58 ➡️
Just musing on the "1/2 shaker egg" idea.... does it have to be a sphere at all, why not a hemisphere ? Isn't it the front half sphere (interfacing with the mic diaphragm) that's going to determine the directionality and mid/HF behaviour, not the rear half of the ball ? So why not indeed just have a half sphere..or would that flat circular face (looking backwards) tend to obstruct the incidence of 'rear of mic' sounds more than if it were curved (ie a full sphere) ?
A hemisphere responds differently. The Pole who does sound work at McGill published some papers on a series of different shapes and how they affected sound. I am not sure I have the links. But, the sphere is what worked best and that is why it is used.
Old 4th February 2013 | Show parent
  #52
Gear Maniac
 
🎧 10 years
I just stumbled across

those

nice black 50mm Delrin balls...
Old 4 weeks ago
  #53
Gear Head
 
I love this topic! The golf ball thing. I wanna see someone drill a hole big enough in a golfball (without going to the hospital). For me, what’s very interesting is the variety of dimple patterns on the market that may cause various reflections not only of acoustics but frequencies? Which ball do you play? But really now, the truth is in the compression- and the amount of layers. A four of five piece ball will generally be softer relative to a two piece ball. The multi layer ball will be softer with transients and a two piece will transmit much more energy and possibly a brighter sound. And now I think I’ll hit myself in the head with a 2 iron!
Old 4 weeks ago | Show parent
  #54
Gear Maniac
 
wtf is this thread about?
Old 4 weeks ago | Show parent
  #55
Lives for gear
 
🎧 10 years
Quote:
Originally Posted by seby ➡️
wtf is this thread about?
The elite sport of golf....perhaps even as DH Lawrence saw it pertaining to the Englishman ("...tramping his thirty miles a day after partridges, or a little rubber ball") ?

https://sites.udel.edu/britlitwiki/h...e-bougeois-is/

Last edited by studer58; 4 weeks ago at 11:56 AM..
Old 4 weeks ago | Show parent
  #56
Lives for gear
 
🎧 5 years
Quote:
Originally Posted by seby ➡️
wtf is this thread about?
I'd say it's about had it.
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