Saturday, June 23, 2007

Polyester Leisure Suit Materials


There are a lot of people who remember, but won't admit they ever owned, a leisure suit. The 70's were like a messed up transitional version of a decade-long alcohol, sex and drug hangover from the prolonged party of the late 60's. Historians will note that the funked, stoned, greasy yippie unwashed student mob eventually found showers, shampoo, and some new clothes,and succumbed to the throb of disco beat and mixed drinks, thereby getting close to many persons of the desired sex on a regular basis with no effort.

I did not ever have a leisure suit. But, I had several polyester shirts. One had a pattern like a chainlink fence on it. I remember this because a nice young lady who is now a rather well known astrophysicist pointed that out to me, as I stood next to a chain link fence near General Cinema. Polyester shirts pick up other chemicals, and I smelled like cigarette smoke (people smoked everywhere at that time and it didn't matter if you smoked or not, your polyester shirt would still stink like coffee, cigs and cream-filled cruellers from spending 35 minutes at a Dunkin Donuts.)

The feel of polyester on skin isn't very nice, which explains why pure polyester clothing isn't very common but blends with other more comfortable fibers, such as cotton, are in most wrinkle free fabrics. Cotton is a favorite material for the microphone maker, as it hardly changes over time, a fact noted by the Egyptians several thousand years ago as they prepared the dead for the afterlife.

Had the Egyptians used polyester, all of those mummy wraps seen on The Discover Channel would have lost any pliability by now.

Most, but not all condenser microphones, use polyester diaphragms in the capsule. But which form of polyester is used, and how does it change over time? How does the sound of a mic change over a long period and do the vintage mic capsules still in service today sound like they did when they were new?

Variously referred to as Mylar (which is just one type of polyester film out of hundreds) this material is a thermoplastic with many uses such as plastic bottles, film sheeting, product packaging (that tough untearable stuff manufacturers use so you have to destroy the package, which reduces store returns) and numerous medical devices, such as catheters. It is very tough!

But polyester has a dark side too. It sometimes aborbs water unless post processed, and it can age harden, be embrittled by heat, damaged by UV, and it picks up a lot of environmental chemicals and smoke films very readily.

DuPont makes many chemicals including this as described by them:

  1. When you're looking for the ultimate combination of stiffness, temperature performance, maximum dimensional stability, and a high-gloss finish in glass-reinforced resins, Rynite® PET thermoplastic polyester resin is the most cost-effective answer. It unites the best properties of reinforced polyethylene terephthalate (PET) with easier processibility to produce high-performance parts that can be molded conventionally.
  2. Rynite® PET is formulated with a unique rapid crystallization system. It also has a 20°C heat deflection advantage over PBT. It can be processed over a broad temperature range.
So, which of the many forms of polyester are used in Neumann TLM-103s, or Feilo or Alctron or 797 Audio? Do Oktava buy "off the same roll" as AKG?

Ribbon microphones missed the Polyester Revolution. Ribbon mics were mostly out of production by the time Polyester appeared under the disco ball. Harry Casey (KC and the Sunshine Band) is arguably one of the more important musical artists of the 70s.

1 comment:

Anonymous said...

right right right

KC got the disco ball spinnin and the world gags