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Author Topic: The Instability of M7 PVC Capsules  (Read 2571 times)

Kai

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Re: The Instability of M7 PVC Capsules
« Reply #15 on: January 06, 2017, 03:56:15 pm »

Why not ask Mr. Thiersch, he might have information on this topic.
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Dan Popp

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Re: The Instability of M7 PVC Capsules
« Reply #16 on: January 06, 2017, 06:53:31 pm »

At the level of degradation we're seeing in these photos, is the audio noticeably compromised?  How bad does the diaphragm have to look, I wonder, before one can hear that something's not right? 
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klaus

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Re: The Instability of M7 PVC Capsules
« Reply #17 on: January 06, 2017, 09:18:51 pm »

There is no straight-forward, easily identifiable, connection between the level of weather-checking on PVC diaphragms and audible performance deterioration.

All PVC diaphragms develop cracks after a few years, but the bifurcation of the single capacitor plate into many smaller ones, and thereby the deterioration of performance, can only be heard (higher noise floor), measured (loss of capacitance), or triggered into malfunction by strong moisture or SPLs (thunderous discharges which only ebb slowly).

The severe, deep cracks and pointed indentations as part of the cracks J.J.'s Thiersch capsule shows would give me concern, though. But he is good for warranty exchanges, in my experience.
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Klaus Heyne
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J.J. Blair

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Re: The Instability of M7 PVC Capsules
« Reply #18 on: January 06, 2017, 10:38:18 pm »

Good to know, Klaus.  I might hit him up about that. 
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gtoledo3

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Re: The Instability of M7 PVC Capsules
« Reply #19 on: January 08, 2017, 10:05:22 am »

There was a bit where MG had just shifted over to mylar, were delivering mics with M7 that way and weren't really saying much about it. That was a good idea!

Yes, it is an impossibility of physics for that film to sound exactly the same as PVC. However, no one complains when it's on a K47.

For my money, the Thiersch Redline has a sound that is useful and different enough from a Neumann k47 to justify having it available; a certain type of smoothness on the top, perhaps some more lower mids. Bonus, it doesn't disintegrate.
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klaus

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Re: The Instability of M7 PVC Capsules
« Reply #20 on: January 09, 2017, 12:42:29 am »

There was a bit where MG had just shifted over to mylar, were delivering mics with M7 that way (...)

Just to be clear: Microtech Gefell has offered M7 with Mylar and PVC diaphragms since the 1990s.
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Klaus Heyne
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J.J. Blair

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Re: The Instability of M7 PVC Capsules
« Reply #21 on: January 10, 2017, 08:47:31 pm »

So, I decided to A/B the Thiersch M7 against a couple K47s yesterday.  The K47s were both cream ring versions, and were pretty damned similar.

When I got the M7, I remember it sounding a tad darker than the K47s, but warmer, and having a touch more lower mids.  Now, it's maybe a touch brighter than the K47s, but leaner in the bass.  The K47 is more harmonically complex though, and more satisfying.  The M7 seems to suffer from more proximity effect, but a larger margin.  Much less presence and low end from a distance of over 18 inches. 
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gkippola

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Re: The Instability of M7 PVC Capsules
« Reply #22 on: January 13, 2017, 11:59:09 am »

My 1955 Tele U47 polyester M7 is still awesome sounding,  cracks and all----
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klaus

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Re: The Instability of M7 PVC Capsules
« Reply #23 on: January 13, 2017, 12:17:13 pm »

That's quite rare.
And: surely you mean "PVC" as polyester was not yet invented in 1955.
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Klaus Heyne
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boz6906

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Re: The Instability of M7 PVC Capsules
« Reply #24 on: January 14, 2017, 08:29:47 pm »

"Carother’s incomplete research had not advanced to investigating the polyester formed from mixing ethylene glycol and terephthalic acid. It was British scientists – Whinfield and Dickson who patented PET or PETE in 1941. Polyethylene terephthalate forms the basis for synthetic fibers like Dacron, Terylene and polyester.

In 1950, the Dealware property of duPont manufactured another polyester fiber, which they named Dacron.

Later that year, the first polyester fiber – Terylene – was created by Whinfield and Dickson along with Birtwhistle and Ritchiethey. Terylene was first manufactured by Imperial Chemical Industries or ICI.

It was in 1946 that duPont bought all legal rights from ICI. In 1950, the Dealware property of duPont manufactured another polyester fiber, which they named Dacron. Mylar was introduced in 1952. Polyester was first introduced to the American public in 1951 as the magical fabric that needed no ironing! PET and PEN are duPont trademarks that have turned the use and consumption of Polyester around."

http://www.whatispolyester.com/history.html


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klaus

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Re: The Instability of M7 PVC Capsules
« Reply #25 on: January 15, 2017, 04:17:11 pm »

You are correct. I should have been more precise by saying that in 1955 polyester had not yet been invented or used as substrate for capsule diaphragms. That started around 1958, when the first K49 were introduced and used in M49. U47 continued using the M7 until around 1959/60.
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Klaus Heyne
German Masterworks®
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