Graphene Diaphragm

[Recording Engineer]

I remember this article from 2015:
https://iopscience.iop.org/article/...DC354CD91D44977419D.c5.iopscience.cld.iop.org
I remember back then asking Allen Luke of Luke Audio if he ever played with it. He did for a couple years with Shannon Rhoades at Mic Rehab and could never get anything worthwhile; but was encouraged by that article, saying it was great seeing someone making good strides with it.


Have you guys seen Griffon Microphones’ on-going developments now?:
https://griffon-microphones.jimdofree.com/graphene-capsule

 

[Tim Campbell]

I really don't see an advantage in switching to this from what is currently used. You want a conductive material that is as flexible as possible, thin enough to respond but not so thin it is unstable, long lasting, and insulated on one side. Mylar fits this bill perfectly.

Reading his description it is totally false. The mylar never shorts againt the backplate. The mylar itself is an insulator on the side facing the backplate and only conductive on the gold surface. I doubt anyone could show data that moisture absorbtion by mylar membranes changes the sound of a capsule. In moist environments the change in barometric pressure would most likely have a greater effect.

He seems to be using a very thick membrane. It's response may look flat but I can't imagine it sounds better.

 

[Recording Engineer]

Yeah, I personally am never sold on any particular argument and strictly focus on good useable sounds that divert from the traditional standards. Time will tell if it’s a road worth travelled in the end there.

 

[wlinart]

Looking at the pictures the guy from Griffon posted it seems he's using the 25mm aliexpress type of capsule or the typical Chinese "CK12" style capsule and then reskins it with this type of foil. Cheap enough to try.

 

[abbey road d enfer]

Considering graphene is an electrical conductor, how is the diaphragm isolated? I think in any case the inactive part of the diaphragm will add parasitic capacitance, which results in excess noise and distortion. It may not be the case with a nylon capsule.

 

[abbey road d enfer]

I remember this article from 2015:
https://iopscience.iop.org/article/...DC354CD91D44977419D.c5.iopscience.cld.iop.org

Quote: "The widely studied and available nickel has been a dominant membrane material for professional microphones for several decades"
Really?

 

[wlinart]

Considering graphene is an electrical conductor, how is the diaphragm isolated? I think in any case the inactive part of the diaphragm will add parasitic capacitance, which results in excess noise and distortion. It may not be the case with a nylon capsule.

The foil i linked to has a PET foil layer

 

[abbey road d enfer]

The foil i linked to has a PET foil layer

Is it designed to stay permanently? I would think it's disposable.

 

[ccaudle]

Quote: "The widely studied and available nickel has been a dominant membrane material for professional microphones for several decades"
Really?

I believe nickel is common in measurement microphone capsules (the type which use 200V polarization voltage).
According to the Bruel & Kjaer Microphone handbook common capsule material is nickel foil or stainless steel alloy:
B&K Measurement Microphone Handbook

That may give an indication that the expected use case is measurement and not studio microphones. The video at the first link describing a PhD project using graphene shows that the housing of a B&K measurement capsule was used for testing the carbon diaphragm.

The Griffon capsule seems unrelated to the first link from the Serbian PhD student.

 

[abbey road d enfer]

Ah, OK. I had stupidly assumed that recording microphones were professional...

 

[Tim Campbell]

I believe nickel is common in measurement microphone capsules (the type which use 200V polarization voltage).
According to the Bruel & Kjaer Microphone handbook common capsule material is nickel foil or stainless steel alloy:
B&K Measurement Microphone Handbook

That may give an indication that the expected use case is measurement and not studio microphones. The video at the first link describing a PhD project using graphene shows that the housing of a B&K measurement capsule was used for testing the carbon diaphragm.

The Griffon capsule seems unrelated to the first link from the Serbian PhD student.

Well Bruel & Kjærs membrane is pretty far from the backplate and they use a high polarization to compensate. The Achilles heel of most nickel membranes is they touch the backplate and burn holes in the nickel over time making them unusable.

If this graphene is attached to mylar then I really see no point in it.

You could easily make mylar conductive by rubbing it with graphene powder or even many soaps as they used to do for some electrostatic speakers.

 

[ccaudle]

Bruel & Kjærs membrane is pretty far from the backplate and they use a high polarization to compensate

What is a typical separation for a mylar diaphragm? B&K mentioned 20um as typical for measurement capsules. That sounds like a small separation to me, but I don't have any reference for comparison.

 

[Tim Campbell]

What is a typical separation for a mylar diaphragm? B&K mentioned 20um as typical for measurement capsules. That sounds like a small separation to me, but I don't have any reference for comparison.

Please post this reference. That info is not included but you can see that their membranes are tuned from 8kHz up to 160kHz which would make them very stiff and not useful for cardioid.

 

[abbey road d enfer]

I don't have a reference either, but knowing that a typical 1" capsule measures at about 70pF, using the formula
C=epsilon zero. A/d, with epsilon zero (permittivity or dielectric constant of air), A the area and d the distance
I get d= epsilon zero.A/C and d=37. 10E-6 meter or 37 microns.
Now Ni diaphragms probably don't collapse as easily as mylar...?

 

[Tim Campbell]

I don't have a reference either, but knowing that a typical 1" capsule measures at about 70pF, using the formula
C=epsilon zero. A/d, with epsilon zero (permittivity or dielectric constant of air), A the area and d the distance
I get d= epsilon zero.A/C and d=37. 10E-6 meter or 37 microns.
Now Ni diaphragms probably don't collapse as easily as mylar...?

Well that is obviously true. If you were to set the distance to backplate on a 1" mylar membrane tuned to a typical resonance freq. at 37microns and begin to polarize it it would most likely collapse before 90v. These B&K capsules are polarized to 200v, These high resonance freq. help control this but for a cardiod capsule to work well the tuning freq. must be in the mid bands.

 

[Gus]

What about the Shure ribbons?

 

[ccaudle]

Please post this reference.

It was in the B&K microphone handbook I linked in my earlier post.

 

[Tim Campbell]

It was in the B&K microphone handbook I linked in my earlier post.

" The distance between the backplate and the diaphragm is typically 20 μm ( ± 0.8 μm).
The nominal distance may vary between microphone types from about 15 to 30 μm."

So you are right that is not a large gap. The stiffness of the diaphram must be the only thing keeping it from shorting against the backplate.

 

[Harvey Birdman]

Well Bruel & Kjærs membrane is pretty far from the backplate and they use a high polarization to compensate. The Achilles heel of most nickel membranes is they touch the backplate and burn holes in the nickel over time making them unusable.

If this graphene is attached to mylar then I really see no point in it.

You could easily make mylar conductive by rubbing it with graphene powder or even many soaps as they used to do for some electrostatic speakers.

Neumann had nickel diaphragms in KM88 & KM56. I had a pair of KM88’s, never had a problem with them, used them on vocals, piano & acoustic guitar. They are a small diaphragm capsule. I still regret selling them!

 

[Tim Campbell]

Neumann had nickel diaphragms in KM88 & KM56. I had a pair of KM88’s, never had a problem with them, used them on vocals, piano & acoustic guitar. They are a small diaphragm capsule. I still regret selling them!

I own 3 KM56's. The single most common fault with Neumann nickel diaphrams is burning holes in the diaphram from them touching the backplate. Thiersch makes a good deal of his living from these repairs as he is one of the few who does this work. I have seen at least a dozen of them with this problem. You were lucky or gentle with them.

I believe Danmarks Radio was the largest single purchaser of KM56's.

I would recommend anyone buying KM54/56 microphones to examine the diaphrams before you buy them.

Klaus Heyne
…[When] the diaphragms were repeatedly overloaded with SPLs to a point that the metal diphragm bottomed out against the electrically charged backplate, a tiny (arc) hole [can burn] into the diaphragm at the point of contact.

Klaus Heyne
Weaknesses: super-fragile nickel capsules with tendency to develop arc holes from contact between metal diaphragm and metal backplate.