Making a LDC Capsule - Videos

[kingkorg]

We do not polish our backplates, so the extra amount of air viscosity created by unpolished surface and tight spacing is a part of diaphragm damping.

With all due respect i see this comment as misleading. There is no way one can account for that tiny of a difference in volume of air between 800 grit vs 400 vs polished, and claim it makes a difference in diaphragm damping = difference in sound.

You are a knowledgeable man, with great resources, setup... and i am sure you can provide for once some empirical measurements and proof for claims of any of your products. Either capsule which has very unique features not available in any other capsule i am aware of. Or your acoustic lens capsule holders for example.

If anything, you as a manufacturer, can provide some resource material or video about capsule manufacturing process, not revealing proprietary secrets off course. This thread is about that. This forum i hope is still about DIY, not just advertisement and product placement.

 

[soliloqueen]

With all due respect i see this comment as misleading. There is no way one can account for that tiny of a difference in volume of air between 800 grit vs 400 vs polished, and claim it makes a difference in diaphragm damping = difference in sound.

You are a knowledgeable man, with great resources, setup... and i am sure you can provide for once some empirical measurements and proof for claims of any of your products. Either capsule which has very unique features not available in any other capsule i am aware of. Or your acoustic lens capsule holders for example.

If anything, you as a manufacturer, can provide some resource material or video about capsule manufacturing process, not revealing proprietary secrets off course. This thread is about that. This forum i hope is still about DIY, not just advertisement and product placement.

I would be curious to see comparisons too. What he is saying is plausible, there's a theoretical basis for this. He said air viscosity, not air volume. (I think also when he said viscosity he meant effective viscosity, that is to say the level at which the backplate slows the airflow, not material viscosity of the air itself.) It's not about the volume of the air, but the movement of the air. Think of it akin to friction acting on the air from the different surface. Whether it's big enough to make a difference, I'm not experienced enough to say. Intuitively one might say that the surface texture isn't enough to affect the air that much, but remember that we are dealing with minuscule volumes of air flowing over uncountably small distances. A difference in texture might just eat enough of that force to make a difference at that scale. I could absolutely see M being right about this. I don't think it's automatically suspect information just because he brought up his own product. I bring up my stuff in discussions all the time!

You two both do very deep dives into capsules and are very liberal with information, I'm super thankful for that. Both of your posts over the years have really informed me in my design process.

 

[Tim Campbell]

With all due respect i see this comment as misleading. There is no way one can account for that tiny of a difference in volume of air between 800 grit vs 400 vs polished, and claim it makes a difference in diaphragm damping = difference in sound.

You are a knowledgeable man, with great resources, setup... and i am sure you can provide for once some empirical measurements and proof for claims of any of your products. Either capsule which has very unique features not available in any other capsule i am aware of. Or your acoustic lens capsule holders for example.

If anything, you as a manufacturer, can provide some resource material or video about capsule manufacturing process, not revealing proprietary secrets off course. This thread is about that. This forum i hope is still about DIY, not just advertisement and product placement.

I agree with Marik. Air being compressed across a smooth surface would move more easily and damp slightly less than moving across a rough surface. There is quite a bit of difference in smoothness between 400 grit and 800 grit.

My original post that seemed to stir such vitriol wasn't actually about the effect of 400 grit abrasion on a backplate but to debunk this wive's tale that surface smoothness contributes to collapsing of membranes as Eric stated. 400 grit is rough enough that it is hard to insure the backplate is actually flat and raised areas will attract the membrane more easily.

 

[soliloqueen]

I agree with Marik. Air being compressed across a smooth surface would move more easily and damp slightly less than moving across a rough surface. There is quite a bit of difference in smoothness between 400 grit and 800 grit.

My original post that seemed to stir such vitriol wasn't actually about the effect of 400 grit abrasion on a backplate but to debunk this wive's tale that surface smoothness contributes to collapsing of membranes as Eric stated. 400 grit is rough enough that it is hard to insure the backplate is actually flat and raised areas will attract the membrane more easily.

Yeah, that was my take on it. If the membrane is collapsing far enough down to get stuck to the smooth surface the first place, you have bigger problems than backplate finish.

Could a smooth surface, mechanically, make the membrane stay stuck if it sticks (not more likely to stick, which is a different question)? Yeah, but it shouldn't be able to get there in the first place.

 

[Whoops]

This forum I hope is still about DIY, not just advertisement and product placement.

+1

 

[soliloqueen]

Caveat to Mariks point, if that's the way it works, surface finish is more something that affects capsule performance, not something that necessarily makes capsule performance worse or better. Provided that we are talking purely about finish, the surface is still flat and surface finish is consistent throughout, any differences could probably be compensated for elsewhere in the design of the capsule backplate. It's just one of the many tools you can use to affect airflow while designing a backplate. I'm talking purely about finish here, not differences big enough to mess with the viability of the capsule.

 

[pinchemotherloaf]

From what I can say, and imho
(ck12) backplate flatter=better

 

[Recording Engineer]

*Edit - Comment deleted due to not being useful to the topic, unless I can figure out how to delete this whole reply.

 

[kingkorg]

I agree with Marik. Air being compressed across a smooth surface would move more easily and damp slightly less than moving across a rough surface. There is quite a bit of difference in smoothness between 400 grit and 800 grit.

Again with all due respect, while i see how this makes sense in theory, i'm dying to see some measurements of this effect in real world application. I will surely test this and measure for my self. I was just wondering if someone has measurements of this effect since you guys seem to be very aware of it.

Increased damping would result in less high and low frequency content. To what degree? What frequency range?

I am asking because when i closed half of all blind holes in a k67 i got about -4db hf content. Im dying to see how much difference surface smoothness would make. But again i will test that eventually.

 

[kingkorg]

I don’t understand why this was deemed necessary.

Welcome, i was expecting you. But i'm not falling for that again. Cheers.

 

[soliloqueen]

I don’t understand why this was deemed necessary.

I think because he thought Marik was talking about volume and not friction, he temporarily misunderstood Marik's point to be a much more ridiculous one and assumed Marik blowing smoke about his own manufacturing process. I think it's just a small misunderstanding. Let's keep this thread rolling

 

[soliloqueen]

Again with all due respect, while i see how this makes sense in theory, i'm dying to see some measurements of this effect in real world application. I will surely test this and measure for my self. I was just wondering if someone has measurements of this effect since you guys seem to be very aware of it.

Increased damping would result in less high and low frequency content. To what degree? What frequency range?

I am asking because when i closed half of all blind holes in a k67 i got about -4db hf content. Im dying to see how much difference surface smoothness would make. But again i will test that eventually.

I do agree that it's unintuitive that surface finish would make such a big difference, but like I said, these are wildly small scales at I could totally see it being a thing. Love to see someone chime in with examples of capsules at different finishes.

You could start with a capsule with the roughest backplate you can find and take it to a precision machine shop to get it lapped and rebuild the capsule and measure it yourself to see if there's a difference

 

[kingkorg]

I do agree that it's unintuitive that surface finish would make such a big difference, but like I said, these are wildly small scales at I could totally see it being a thing. Love to see someone chime in with examples of capsules at different finishes.

You could start with a capsule with the roughest backplate you can find and take it to a precision machine shop to get it lapped and rebuild the capsule and measure it yourself to see if there's a difference

Ok spoiler alert.

I make my own capsules, i mod them, and have carefully tuned measurement rig. I have tested the effect, and when it comes to sound the surface doesn't make any difference.

When it comes to sticking of the diaphragm surface might have effect, but will depend heavily on diaphragm tension, if the capsule is sealed, edge or center terminated, voltage, materials.

I am just trying to tease out if anyone else has measurements showing the opposite. Which i doubt. But i might be doing something wrong.

If i post my own measurements they will probably be regarded as biased and inaccurate. It happened before.

 

[Tim Campbell]

Again with all due respect, while i see how this makes sense in theory, i'm dying to see some measurements of this effect in real world application. I will surely test this and measure for my self. I was just wondering if someone has measurements of this effect since you guys seem to be very aware of it.

Increased damping would result in less high and low frequency content. To what degree? What frequency range?

I am asking because when i closed half of all blind holes in a k67 i got about -4db hf content. Im dying to see how much difference surface smoothness would make. But again i will test that eventually.

kingkorg unless you can set up two capsules that are exact in every respect but this, any variation such as spacing distance or deviation in material thickness might negate it. It is provable I am sure but not quick or easily and the time would be better spent on other things. Let it suffice to say that if you build a more highly mechanically controlled capsule you will get more consistent results. A capsule is a sum of it's parts and very often you can take from one area and add in another and wind up with the same results. My point, not other's, was that it does not contribute to collapsing.


I will also add that in measuring freq. response smoothing throws out more info than it retains and differences may be thrown out in that process.

 

[kingkorg]

Much easier than that. K67 from 797 is mirror polished, and diaphragm is glued to the ring. All it takes is to remove the diaphragm, mess with the surface, reassemble it and measure in the body which was never moved from the testing jig. Exactly what i've done. And measured no difference.

Important thing! I have never tested this with edge terminated capsule. But i can't see why it might make any difference.

I don't use any smoothing in my measurements, you are perfectly aware of how i get my quite precise measurements. I remember us agreeing on that one.

 

[Recording Engineer]

*Edit - Comment deleted due to not being useful to the topic, unless I can figure out how to delete this whole reply.

 

[Tim Campbell]

Does the K67 from 797 collapse because it is polished? No. Will it be a better capsule because it is scratched with 400 grit sandpaper on some flat surface? No. If it was a better method 797 would do it because they are governed strictly by profit margin and it would save them money. Even Neumann's sandblasted backplates are flat to within 2 microns before they are surfaced.

 

[kingkorg]

I think we actually agree on everything here, as usual. Somehow something gets lost in the translation, and some noise gets generated along the way. Thank you for the time you still spent on this forum. All of your posts are greatly appreciated.

 

[soliloqueen]

I'd be curious to see if crossed slot designs have different sensitivities to different imperfections than blind and through hole designs and whether those different sensitivities might make them easier to DIY. I've been working on a true crossed slot LDC for some time now but I kind of ran out of money before I could do any serious testing with it.

 

[kingkorg]

I have an idea to throw your way.
There is real lack of true kk84 type capsules. However mxl603 type capsules can easily be modded by just manufacturing the right backplate and replacing the existing one in 603 model. They cost comething like 10$... can be found everywhere.