Ribbon (mic) corrugation depth

[GarthElliot]

I would like to know the corrugation depths of some ribbon mics out there.  I do realize that the depth is dependent on the amount the ribbon was stretched before mounting, but an average figure would help.  (I've already checked out the section of the BBC document by Shorter & Harwood that compares corrugation pitches - the production model's corrugation depth is 0.002").

The reason I'm interested in the depth is because I would like to heat-shape a coated mylar ribbon and need to manufacture a jig with the desired corrugation pattern and cannot run it through the (traditional) set of gears.

G.

 

[PRR]

> coated mylar ribbon

You need a maximum of conductor for your mass. Adding Mylar dilutes your conductance/mass ratio.

Corrugations dilute your conductance per unit air-catch area. No corrugations would be efficient; but secondary resonances mess-up the response. Perhaps your Mylar will control that?

I think you are in unexplored territory. Or rather: the Big Boys have probably looked at the idea (it has major production benefits) and found it wanting.

 

[Marik]

As PRR says, you need max conductance for the mass. On top of the mass of the Mylar itself, the Al coating uses deposition process, which has worse conductivity than rolled foil, so the system will be quite inefficient, with high resistance noise.

Best, M

 

[GarthElliot]

Thank you for your replies.  I'm just trying to duplicate the process the Crowley & Tripp (shure) uses.  I thought it was just a heat-shaped aluminum-coated mylar film.

About the corrugation depth and shape of the corrugation: I would like to learn more about the effects the corrugation pattern has on the transduction.  I have a friend with software to simulate the motion of the diaphragm, but I'm not sure that it will be of any help with regards to the expected frequency responce.

Regards,
Garth

 

[Marik]

Thank you for your replies.  I'm just trying to duplicate the process the Crowley & Tripp (shure) uses.  I thought it was just a heat-shaped aluminum-coated mylar film.

No, it is nano-tubes technology.

 

[leswatts]

No, it is nano-tubes technology.

Mark,

I got curious and researched this, and from the patent claims I also think it's just PET or another polymer laminated to aluminum.

While nanotubes have some interesting attributes, I found no properties of the material that might be useful to improve a mic ribbon. As formed it's a rather poor conductor, even though individual tubes show metallic properties. The tunneling from one tube to another kills the good conductivity though.
If it could be formed in full ribbon length parallel strands it would be pretty good, but the ones i've seen are very short.

But I haven't disassembled one of the mics or analyzed their material.

Les

 

[GarthElliot]

My assumptions came from the patent application. And I thought Mylar would be a good candidate because it can be heat-shaped.

G

 

[Marik]

My guess, you just looked at the wrong patent. Also, if you get back to Bob's blog, as well as look at the C&T marketing you will see that was a nano-tube technology.

Best, M

 

[zebra50]

There's a real knack to writing patents - the trick is to protect your thing. without really revealing exactly what it is that you're doing. Consequently they can be less-than-ideal sources of information. When I worked as a research chemist, some of the patents would have deliberate red herrings or non-essential steps added to the process, just to throw the opposition of the scent.

Bob's blog is worth a read, although of course there is less microphone stuff there than there once was.
http://microphonium.blogspot.com/

He posts here sometimes too, so maybe he'll chime in with some info.