Sorry, those links dosen't work.
C800G
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dukasound
Well-known member
[quote author="Gus"]Yes that is the tube[/quote]
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Marik
Well-known member
Some more updates. Last night I measured spacers in K67 and Chinese 6um. The K67 was 0,0015", and Chinese 0,001". I did it with digital caliper, as I could not find my micrometer at the moment, but later will give more presise measurements. BTW Tim, have you ever had chance to measure spacers between diaphragm and backplate for both capsules?
I cut a slot in Chinese spacer exactly like in K67 and gave it a listen. The bass and midbass changed noticably. I could not find any information about mechanism of that, but would think it works as an equalizing tube in dynamic mics. It is probably similar in principle to function of a port in bass reflex speakers.
I cut a slot in Chinese spacer exactly like in K67 and gave it a listen. The bass and midbass changed noticably. I could not find any information about mechanism of that, but would think it works as an equalizing tube in dynamic mics. It is probably similar in principle to function of a port in bass reflex speakers.
I took a closer look at my mxl2003 capsule. This is the 797 style with a plastic backplate. The backplate does not have blind holes only thur holes. The thur holes seem to be the same diameter as the larger holes in front plate.
The capsule in the MXL 2001,1006,v67,v69s use the same plates for front and back. I might open up the thur holes a little if I can find a small drill in the backplate and mybe the front plate.
I am also going to take a caliper and measure the diameter id the inside of the rings in both styles. The thickness of the backplate washer should have something to do with the air volume.
Could the V67,2001,1006,V69 capsules have a little to much air resistance? so maybe there is just a little to much "drag" resistance between the front and back skins.
I would be cool to figure this out. maybe .001 is to little and .0015 to much. I want to understand this! I keep thinking we should be able to get the capsules to sound great.
The capsule in the MXL 2001,1006,v67,v69s use the same plates for front and back. I might open up the thur holes a little if I can find a small drill in the backplate and mybe the front plate.
I am also going to take a caliper and measure the diameter id the inside of the rings in both styles. The thickness of the backplate washer should have something to do with the air volume.
Could the V67,2001,1006,V69 capsules have a little to much air resistance? so maybe there is just a little to much "drag" resistance between the front and back skins.
I would be cool to figure this out. maybe .001 is to little and .0015 to much. I want to understand this! I keep thinking we should be able to get the capsules to sound great.
Tim
The shim stock would be .001" etc for the washer between the backplate and/or the skin spacers.
I found a telescope mirror coating companys web site that does Al ,Ag and Au.
Anyone know what the proper way to evaporative coat PET? What I mean follows
Do you first heat treat at 80 C to relax the stresses in the PET or do you heat treat after coating and tuning in a jig. 80C is about the glass transition temperture. google glass transition, very interesting.
Do you use a different metal to help bond the Gold to the PET? How thick is the coat(s) in angstroms
Do you use a plasma to clean the PET beforre coating
Do you coat the PET under tension?
Can or will anyone tell how Neumann etc do this?
I have been reading and thinking about this and the way I would try do it is
1) heat treat the pet
2) mount The PET in a tuning jig
3) tune the PET
4) clean and coat the PET still in the jig
5) retune and glue to the mounting ring
Problem with this order is it is alot of work and time. Why I would try to do it this way is because if you tune after coating when not under tension the bonds between the metal and PET might be weakened. Also the change in the PET should be less with the capsule life time.
I have not coated a skin nor do I know how it is done by the microphone companys and/or supplies. This is just my best guess at this time.
The shim stock would be .001" etc for the washer between the backplate and/or the skin spacers.
I found a telescope mirror coating companys web site that does Al ,Ag and Au.
Anyone know what the proper way to evaporative coat PET? What I mean follows
Do you first heat treat at 80 C to relax the stresses in the PET or do you heat treat after coating and tuning in a jig. 80C is about the glass transition temperture. google glass transition, very interesting.
Do you use a different metal to help bond the Gold to the PET? How thick is the coat(s) in angstroms
Do you use a plasma to clean the PET beforre coating
Do you coat the PET under tension?
Can or will anyone tell how Neumann etc do this?
I have been reading and thinking about this and the way I would try do it is
1) heat treat the pet
2) mount The PET in a tuning jig
3) tune the PET
4) clean and coat the PET still in the jig
5) retune and glue to the mounting ring
Problem with this order is it is alot of work and time. Why I would try to do it this way is because if you tune after coating when not under tension the bonds between the metal and PET might be weakened. Also the change in the PET should be less with the capsule life time.
I have not coated a skin nor do I know how it is done by the microphone companys and/or supplies. This is just my best guess at this time.
dale116dot7
Well-known member
I haven't done evap coating yet, I'm just finishing my evap jig. Got the vac pump and heaters but they're not mounted or hooked up yet.
My understanding is you heat the sample (mylar) to about 80C or so, then evap about 5 angstroms of Nickel, then the remainder (100 to 300 angstroms) of gold. The nickel is required as gold doesn't like sticking to Mylar. I haven't dont this yet.
-Dale
My understanding is you heat the sample (mylar) to about 80C or so, then evap about 5 angstroms of Nickel, then the remainder (100 to 300 angstroms) of gold. The nickel is required as gold doesn't like sticking to Mylar. I haven't dont this yet.
-Dale
Hi Gus,
there is a recent book about Neumann mics called 'Neumann the microphone company" published by ppvmedian. ISBN 3-932275-68-3. It has some photographs of capsule dipahragms undergoing gold vacuum coating. I could try to scan these if you're interested. The book is good for pictures but not so good on hardcore technical information.
Stewart
there is a recent book about Neumann mics called 'Neumann the microphone company" published by ppvmedian. ISBN 3-932275-68-3. It has some photographs of capsule dipahragms undergoing gold vacuum coating. I could try to scan these if you're interested. The book is good for pictures but not so good on hardcore technical information.
Stewart
Marik
Well-known member
Gus,
Yes, it has do a lot. Last couple weeks I went through a lot of experiments, screw-ups, and frustration.
The general observation--the thicker spacer--more bass--less HF.
In fact, I am thinking quite opposite. In theory, more acoustical resistance should give more uniform frequency response. There is, however, a very fine line between acoustical resistance (air cution between diaphragm and back plate) and air volume trapped between backplates, when response is flat. So far, with spacers I was able to tune the capsule so, that I have whether good bass, or good HF. IMO, more acoustical resistance will help to equalize those two. If I had means of reskining capsule I would try drilling in the backplate more blind holes. It would be cool to see what it affects.
No doubt we will get there.
Tim,
I checked very carefully and holes in MXL2001 and K67 look the same.
Mine has this split and no tape. Also, it has a little hole in the front skin, and back skin is warped. Still it sound wonderful. I made the split in 2001 spacer and it sounds like crap.
As far as I know, the gold evaporated when mylar is already pretentioned in the jig.
I have uploaded some scanned pictures from the Neumann book which show the gold coating process and tensioning of their membranes. I'll leave these up for about a week so grab them whilst you can.
Stewart
http://omnipressor.com/Other/NeumannBook/
Stewart
http://omnipressor.com/Other/NeumannBook/
I have been lookin at the pictures.
DIY thoughts
Maybe a stainless steel bowl that fits inside a bell jar.
The square pieces and Xs hold the pretenstioned PET and ring in place and the holes form the target
Looks like the "Bowl" is held at a voltage different to attract the Hot gold atoms.
I can't tell what the heater boat metal is maybe Tungsten?
Is it a High vacuum? I can't tell if there is a thermocouple probe in the bell jar.
is it sputtering or evaporation?
Is it gassed (argon etc.)filled to plasma clean the PET before coating
Looks like just gold is loaded in the heater boat.
Also looks like the rings mount in another jig maybe to center the cental gold spot and to final tune via res freg or weight.
I need to find some of the Scientific American amater scientist articles from the 50's to 70's IIRC there were writeups for making vacuum pumps, sputtering, cold traps, difussion pumps lots of stuff.
DIY thoughts
Maybe a stainless steel bowl that fits inside a bell jar.
The square pieces and Xs hold the pretenstioned PET and ring in place and the holes form the target
Looks like the "Bowl" is held at a voltage different to attract the Hot gold atoms.
I can't tell what the heater boat metal is maybe Tungsten?
Is it a High vacuum? I can't tell if there is a thermocouple probe in the bell jar.
is it sputtering or evaporation?
Is it gassed (argon etc.)filled to plasma clean the PET before coating
Looks like just gold is loaded in the heater boat.
Also looks like the rings mount in another jig maybe to center the cental gold spot and to final tune via res freg or weight.
I need to find some of the Scientific American amater scientist articles from the 50's to 70's IIRC there were writeups for making vacuum pumps, sputtering, cold traps, difussion pumps lots of stuff.
For info on the gold evaporating/sputtering, also check info about electron-microscopy.
Every sample viewed in an electron microscope has to be metallized first - so if you find a place near you that has such a microscope, they'll be able to help you with pouring gold on your diagphragmes...
Jakob E.
Every sample viewed in an electron microscope has to be metallized first - so if you find a place near you that has such a microscope, they'll be able to help you with pouring gold on your diagphragmes...
Jakob E.
Thanks Stewart!
That series explains a lot..!
Jakob E.
That series explains a lot..!
Jakob E.
[quote author="Gus"]The cap value at working voltage might be a different way to test tension.[/quote]
The capacitance at working voltage will be a great indicator of sensivity, and front/back halves needs to have matched sensitivity in order to deliver predictable pickup patterns..?
Jakob E.
The capacitance at working voltage will be a great indicator of sensivity, and front/back halves needs to have matched sensitivity in order to deliver predictable pickup patterns..?
Jakob E.
