Emperor-TK
Well-known member
[quote author="Gus"]
I guess we would need to find out what brand and type of PET Neumann and AKG use/used.
[/quote]
That might be very tough to find out the specifics of.
[quote author="Gus"]
Would your points 1,2 and 3 be less of a "problem" with more modern tech?
[/quote]
I'm not sure if I understand the question 100%. The process parameters of the polymer have probably been tweaked over the years to be stronger, cheaper, and longer lasting. Whether or not this adversely affects the sound of a mic membrane is anyone's guess. The steel used on the Titanic was reported to be crap by modern standards and likely contributed to the ship's sinking. It might have be a better material for making resonator guitars though.
[quote author="Gus"]
Point 4 I think the Dupont stuff has two grain directions W and L
[/quote]
Yes. This is a result of the extrusion process. Blown films are made by pulling molten polymer over a hoop with air blowing through it. Think of the polymer as a big bunch of spaghetti. Some of the spaghetti strands line up in the direction that is being pulled, and some of it lines up in a tangential direction to the hoop, since the hoop is pulling the film open at the same time. To further the spaghetti model, PET is semi crystalline, so you can picture some uncooked spaghetti in the mix too. The "uncooked spaghetti" will tend to cluster and orient to the hoop and extrusion stresses too.
[quote author="Gus"]
I believe good capsules are heat treated at 80C to relax the grain 80c is Tg for PET I believe. Whats corona and flame treatment? point 5
[/quote]
That makes sense to me. I'd imagine since the skins are mounted with equal tension at the "lugs", you would want a material that responds the same in each direction. Imagine a sheet of woven glass, like that used in fiber-glass boats. There are two directions that the sheet will not stretch, each along the length of the glass fibers. But if the sheet is rotated 45 degrees, it will give fairly easily.
Regarding corona treatment and flame treatment, these are both oxidation steps done to change the surface chemistry of the films for coating reception. Just another source of variability in PET grades.
[quote author="Gus"]
Would the different PET mixes have different density and mass?[/quote]
My guess is that you wouldn't see significant differences.
All that being said, this is all just intellectual masturbation on my part. As a chemical engineer, I'm just speculating on what some of the differences between old PET and new PET might be. I'm not trying to say that there is definitely a difference or that any such difference matters. I think Dave put out a great argument about reskinning. I'm not going to spend the rest of my day on the internet spouting rules for microphone materials. :green:
-Chris
I guess we would need to find out what brand and type of PET Neumann and AKG use/used.
[/quote]
That might be very tough to find out the specifics of.
[quote author="Gus"]
Would your points 1,2 and 3 be less of a "problem" with more modern tech?
[/quote]
I'm not sure if I understand the question 100%. The process parameters of the polymer have probably been tweaked over the years to be stronger, cheaper, and longer lasting. Whether or not this adversely affects the sound of a mic membrane is anyone's guess. The steel used on the Titanic was reported to be crap by modern standards and likely contributed to the ship's sinking. It might have be a better material for making resonator guitars though.
[quote author="Gus"]
Point 4 I think the Dupont stuff has two grain directions W and L
[/quote]
Yes. This is a result of the extrusion process. Blown films are made by pulling molten polymer over a hoop with air blowing through it. Think of the polymer as a big bunch of spaghetti. Some of the spaghetti strands line up in the direction that is being pulled, and some of it lines up in a tangential direction to the hoop, since the hoop is pulling the film open at the same time. To further the spaghetti model, PET is semi crystalline, so you can picture some uncooked spaghetti in the mix too. The "uncooked spaghetti" will tend to cluster and orient to the hoop and extrusion stresses too.
[quote author="Gus"]
I believe good capsules are heat treated at 80C to relax the grain 80c is Tg for PET I believe. Whats corona and flame treatment? point 5
[/quote]
That makes sense to me. I'd imagine since the skins are mounted with equal tension at the "lugs", you would want a material that responds the same in each direction. Imagine a sheet of woven glass, like that used in fiber-glass boats. There are two directions that the sheet will not stretch, each along the length of the glass fibers. But if the sheet is rotated 45 degrees, it will give fairly easily.
Regarding corona treatment and flame treatment, these are both oxidation steps done to change the surface chemistry of the films for coating reception. Just another source of variability in PET grades.
[quote author="Gus"]
Would the different PET mixes have different density and mass?[/quote]
My guess is that you wouldn't see significant differences.
All that being said, this is all just intellectual masturbation on my part. As a chemical engineer, I'm just speculating on what some of the differences between old PET and new PET might be. I'm not trying to say that there is definitely a difference or that any such difference matters. I think Dave put out a great argument about reskinning. I'm not going to spend the rest of my day on the internet spouting rules for microphone materials. :green:
-Chris
