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Author Topic: Thin Capsule Diaphragms: Better or Worse?  (Read 13601 times)

Bill_Urick

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Thin Capsule Diaphragms: Better or Worse?
« on: March 16, 2008, 05:43:00 pm »

Thanks for all the input on the SDC vs LDC thread.
I'll try to be more precise in this question.
Is a thinner skin on a capsule preferable?
If so what are the characteristics of thinner capsule skins that make it so? Is there an optimum thickness and are there any trade-offs?

Thanks for putting up with all the questions!
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Klaus Heyne

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Re: How bout' them microns?
« Reply #1 on: March 16, 2008, 07:54:26 pm »

There are both fans and opponents of thin (3
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Klaus Heyne
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Bill_Urick

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Re: How bout' them microns?
« Reply #2 on: March 16, 2008, 09:46:25 pm »

Klaus, you sound as though you're not a fan of the thinner capsules. I don't know enough to have a prejudice, just seeking opinions of those more knowledgeable.
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seedyunderbelly.com

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Re: How bout' them microns?
« Reply #3 on: March 16, 2008, 10:20:23 pm »

The thinner Capsules are not as good in my opinion.  I guess some people like them.  

Tim Campbell

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Re: How bout' them microns?
« Reply #4 on: March 17, 2008, 09:15:27 am »

David Josephson has stated many times his preference for 3 micron diaphrams when they're properly implemented. Maybe we could get him to contribute.

I also remember a discussion with others including Stephen Paul where one particular designer felt that proper dampning would negate most of the effects of a thinner diaphram.

I myself prefer 6 micron membranes on the types of capsules I've produced or repaired.
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Bill_Urick

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Re: How bout' them microns?
« Reply #5 on: March 17, 2008, 07:19:04 pm »

Are there other common thicknesses besides 3 and 6 microns? Does it matter whether we are talking about LDC's or SDC's?
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Good sense is, of all things among men, the most equally distributed; for everyone thinks himself so abundantly provided with it, that those even who are the most difficult to satisfy in everything else, do not usually desire a larger measure of this quality than they already possess.

Klaus Heyne

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Re: How bout' them microns?
« Reply #6 on: March 17, 2008, 09:39:01 pm »

Bill Urick wrote on Mon, 17 March 2008 16:19


Does it matter whether we are talking about LDC's or SDC's?


Yes. The electrostatic attraction of the diaphragm to the backplate is much more an issue with large diaphragms than with small ones.

Thin skin capsules have a harder time withstanding that attraction, because the diaphragm tension which, among other functions, determines the low end response of the capsule, cannot be easily increased to prevent collapse, without choking off low end at the same time.
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Klaus Heyne
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Bill_Urick

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Re: How bout' them microns?
« Reply #7 on: March 18, 2008, 12:17:21 am »

Klaus, in your opinion, what is the optimum thickness for a LDC and for a SDC? Hopefully this is a reasonable question.
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Good sense is, of all things among men, the most equally distributed; for everyone thinks himself so abundantly provided with it, that those even who are the most difficult to satisfy in everything else, do not usually desire a larger measure of this quality than they already possess.

Klaus Heyne

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Re: How bout' them microns?
« Reply #8 on: March 18, 2008, 01:35:48 am »

My preferences have been expressed here and on other forums repeatedly:

The golden balance between speed, yet rich mid range texture, resolution, and long term mechanical stability is 6
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Klaus Heyne
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Schallfeldnebel

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Re: How bout' them microns?
« Reply #9 on: March 18, 2008, 07:45:10 am »

Klaus wrote:"On SDCs it's a bit more complicated. Most of the Mylar capsules I like are around 4
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Oliver Archut

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Re: Thin Capsule Diaphragms: Better or Worse?
« Reply #10 on: March 18, 2008, 12:37:41 pm »

Hello Erik,

if you mentioning weight of metal, please also keep in mind that the tensioning is way higher with metal than with Mylar.
That adds a force with a result similar to a higher weight.
One of the biggest issues, the impulse capability of an capsule is mostly due to the air volume trapped, that volume is also differnt for a pressure vs. a gradient design with reference to impulse.

Best regards,
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Schallfeldnebel

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Re: Thin Capsule Diaphragms: Better or Worse?
« Reply #11 on: March 18, 2008, 06:00:04 pm »

Thanks Oliver, yes I read about that.

Klaus is mentioning membrane thickness and diameter without making distinction between 1. real pressure microphones or pressure-gradient microphones, either 2. made from metal or plastic. Comparing the thicknesses that way is like comparing apples with pears.

Erik Sikkema

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Klaus Heyne

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Re: Thin Capsule Diaphragms: Better or Worse?
« Reply #12 on: March 18, 2008, 08:30:44 pm »

As I was concentrating my remaks on LDCs (which are a largely unexplored territory for omnis) and as omnis are just a minute segment of condenser recording mics in general, I assumed we were talking about cardioids.

Sorry, I did not make this clear up front.
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djosephson

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Re: Thin Capsule Diaphragms: Better or Worse?
« Reply #13 on: March 28, 2008, 06:51:26 pm »

To respond to the earlier comment, yes it's true that at one time I thought that 3 micron diaphragms were preferable for LDCs, and possibly a bit thinner for SDCs. I have since come to a different conclusion, that 6 micron is in general a better compromise, along the lines of the balances and tradeoffs that Klaus mentions. I had convinced myself that 3 micron was better, and worked for several years to produce repeatable and good sounding diaphragms with that material. When I reached what seemed to be a limit, I started working on 6 micron material (and everything else from around 0.4 micron to 12 or so) and found that 6 really did work out better for most mic designs. The differences are minor, once the stability issues are solved, and it really makes very little difference, within reason, because the dominant mass is not that of the diaphragm, but that of the air load on either side of it.

However we should be clear that the thickness is not the issue at all, it's the mass. Nickel weighs 6.4 times as much as mylar does per unit volume, so it's no surprise that a nickel diaphragm of about 1/6 that of an otherwise equivalent mylar diaphragm works out best. The nickel diaphragms on our C617SET omni microphone are 0.9 micron, made by Gefell the same way they were for the KM53/54/56 microphones. The equivalent mics from Bruel and Kjaer in years past were also nickel of the same thickness (now they are mostly rolled steel).
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Klaus Heyne

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Re: Thin Capsule Diaphragms: Better or Worse?
« Reply #14 on: March 28, 2008, 06:55:35 pm »

djosephson wrote on Fri, 28 March 2008 15:51

... we should be clear that the thickness is not the issue at all, it's the mass. Nickel weighs 6.4 times as much as mylar does per unit volume, so it's no surprise that a nickel diaphragm of about 1/6 that of an otherwise equivalent mylar diaphragm works out best...


Excellent point! That's why it makes sense to compare the effect of diaphragm thickness on sound and other capsule performance parameters only within the same material choices.
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Klaus Heyne
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