| Screens In front Of Capsules- Necessary? [message #309740] |
Mon, 28 January 2008 06:14  |
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 Bill_Urick
Messages: 1446
Registered: March 2005
Location: Atlanta |
Platinum Member |
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This question concerns mic construction philosophy in general, so I hope it's OK to post here.
Out of curiosity I picked up an Oktava MK-319 this weekend and did a couple of Mike Joly's suggested "mods" -removing the inner grill, and removing the little perforated plastic discs from the capsule.
OK. Then, before comparing it to an AT-4047 that I have, I decided to disassemble the 4047 to remove a dent from the grill. Guess what....the 4047 in addition to having a double grill (I think quite a few mics do, including high end ones) also had very similar perforated plastic discs covering the capsule faces.
So, at least two mic design engineers, Russian and Japanese presumably, think this little disc thing is a good idea, but I don't recall seeing this on any Neumann mics and my Gefell doesn't have it. Any thoughts?
P.S.: Still workin' on that M7 pic, by the way 
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| Re: A general LDC question [message #310028 is a reply to message #309934 ] |
Mon, 28 January 2008 21:20  |
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Klaus Heyne
Messages: 2942
Registered: April 2004 |
Platinum Member |
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Even on the most expensive condenser mics you can find all levels of obstructions in front of a capsule- everything from 3 layers of metal meshes + additional nylon insert (some ELA M251s), down to a single, course, metal mesh (C12.)
It's like car suspensions: the company decides where to place the compromise between performance and convenience extremes.
That means for microphones a point somewhere between susceptibility for immediate popping and capsule contamination, and fool-proof capsule protection, with more or less reduced fidelity on the other extreme.
Klaus Heyne
German Masterworks
www.GermanMasterworks.com
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| Re: A general LDC question [message #310029 is a reply to message #309740 ] |
Mon, 28 January 2008 21:21 |
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Well I hate to say that I preferred my 319 before I did those mods...but now they are done, and I don't really need the mic anyway.
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| Re: A general LDC question [message #310052 is a reply to message #309740 ] |
Mon, 28 January 2008 23:04 |
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I can't speak for the 319, but I have a 219 that was given to me some time ago & I hardly ever used it because I thought it sounded boring & lifeless.
Last year I discovered that I quite liked it on wood snares, so I thought I'd look into the mods to see if I could make it a better mic that I might use more. After searching around the net a bit I read the opinion that the plastic discs were there to compensate for the acoustic effects of the obstructive metal grille (which reduces high frequencies).
The mod was simply to remove the metal grille, one layer of mesh (bringing it down to one layer) & the plastic discs, as well as to fill the body with padding to reduce ringing. I did these mods & the mic seems a little more natural & has a bit more life, so I guess it is more useful to me now.
sleep is not an option
jwhynot: "There's a difference between thinking or acting dogmatically and drawing from experience."
Glenn Santry
http://www.myspace.com/glennsantry
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| Re: A general LDC question [message #310168 is a reply to message #310057 ] |
Tue, 29 January 2008 09:46 |
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Michael.Joly
Messages: 3
Registered: January 2008 |
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Bill -
Klaus has provided accurate and concise thoughts regarding mic grilles in response to your high frequency resonator disc question. But since you've asked the question in the context of my work, I thought I would provide some additional thoughts.
First, I don't advocate "one size fits all" grille or capsule modifications. And I would never suggest radical grille or capsule modifications are appropriate for well-loved microphones that owe a good deal of their popularity to the grille and capsule designs they employ. Microphones of this class were used to record many of the legendary performances of mid-to-late 20th century music and I agree they should be revered and preserved inviolate.
However, circumstances around the Oktava MK-219 and MK-319 are quite different. Rather than being recording icons, I look upon these mics as "stray dogs" that respond well to some love.
Because these mic are not icons that should be be preserved inviolate, I have been free to re-design them to be consistent with a couple of personal audio engineering goals - accuracy and transparency.
My re-design strategy with these mics has been simple - to allow the capsule diaphragm to respond, as much as possible, to the source sound waves with a minimum of acoustical interference (reflection and refraction) and transduce this response accurately into electrical energy. To allow this, I've done a comprehensive re-design of the entire microphone system including circuit topology, part type/value, mechanical and acoustical changes.
In the specific case of the Oktava MK-219 and MK-319 microphones, I have found a low-reflection, single-layer grille and capsule operating without high frequency resonator discs produces a microphone with improved transient response and detail with a smoother high frequency response curve.
While it is true a perforated high frequency resonator disc does do something (in the case of the MK-219 (it adds +4dB @ 10kHz), it is also true there are amplitude and time domain artifacts that result from the use of HF resonator discs (in the case of the MK-219 the HF resonator discs also produce frequency response dips and mar the impulse response accuracy).
To my ear, I prefer to hear the natural response of the capsule when the artifacts of the HF resonator discs are removed. The analogy of a ribbon mic comes to mind. Ribbon mics are highly regarded in part for their natural, low distortion top end response - despite the fact that the amplitude response is flat or in most cases declines below flat at 10kHz. Even though ribbon mics have a soft top they're still used because they "take EQ well" - they are phase-accurate and can offer a low-distortion HF response. The MK-219 capsule operating without HF resonators offers a similar benefit.
To the folks who have removed the HF resonators from their MK-219 and MK-319 mics and found the high frequency response lacking - I would simply say these mics benefit from a comprehensive, rather than piecemeal approach and they will exhibit well-balanced top end response if a comprehensive suite of changes to the mechanical system, circuit topology and electronics parts is implemented.
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| Re: A general LDC question [message #310316 is a reply to message #309740 ] |
Tue, 29 January 2008 17:03 |
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And I trust that my post did not appear to impugn MJ's well received modifications.
I did MY mod (similar in some respects) to one, and was not 100% pleased with what I personally achieved.
I'm sure if I sent it to MJ, he would return it in much better condition!
Best regards.
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| Re: A general LDC question [message #310412 is a reply to message #310168 ] |
Wed, 30 January 2008 03:58 |
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Schallfeldnebel
Messages: 796
Registered: October 2004
Location: Europe |
Gold Member |
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Maybe in case of the Oktava microphones modifying gives a benefit, but taking away grids from well designed microphones will just give the opposite effect, worse phase- and frequency responses. I know some engineers cutted away the outer metal bars from Schoeps capsule housings. Sometime ago I e-mailed mr. Volmer from Schoeps about this, he answered that this was not such a great idea.
Erik Sikkema
Bill Mueller:"Only very recently, has the availability of cheap consumer based gear popularized the concept of a rank amateur as an audio engineer. Unfortunately, this has also degraded the reputation of the audio engineer to the lowest level in its history. A sad thing indeed for those of us professionals."
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