DIY ribbon mic w/ Mylar as a ribbon material?

[ijvanl]

Hey all,
Has anyone (in the DIY space or elsewhere) ever done a ribbon mic which uses metallized Mylar film (the kind of stuff they use for condenser mic diaphragms) as a ribbon material instead of 2µm aluminium foil?
It seems the perfect material on paper:
it looks to be far more durable than the 2µm foil that seems to be the standard for ribbon mic use,
it's lightweight and flexible enough (at, say, 6µm) to pick up small high-frequency transients (at least when it's under tension, as in condenser microphones; I don't know how good it would be otherwise),
it holds corrugation well,
and it seems to be much more readily available to DIYers than 2µm aluminium foil, which I've only ever seen coming from neat little cardboard boxes special-ordered from Japan, while 6µm aluminized Mylar can be pulled out of most any metallized-film capacitor – already in convenient long strips!
The only issue I can really think of is that the thin coating of metal on the Mylar might not produce enough of a disturbance in the magnetic field to get a good signal level.
That being said, has anyone given a Mylar ribbon mic a go? What have your experiences been?

 

[k brown]

For one thing, I think Mylar would only retain corrugations if heated to a certain (minimum) temperature.

 

[gyraf]

..resistance of alu-coated mylar would most probably be way too high for ribbon mic - remember that we need really low source resistance at the primary side of the transformer - coated mylar measures in the range of hundred'ths of ångstrøms metal, the 2um for the thin foil equals 20000 (!!) ångstrøm

tl:dr - it's not enough that its conductive like in condenser mics, it must also have really low resistance

/Jakob E.

 

[ijvanl]

..resistance of alu-coated mylar would most probably be way too high for ribbon mic - remember that we need really low source resistance at the primary side of the transformer - coated mylar measures in the range of hundred'ths of ångstrøms metal, the 2um for the thin foil equals 20000 (!!) ångstrøm

tl:dr - it's not enough that its conductive like in condenser mics, it must also have really low resistance

/Jakob E.

Hmmmmm. You're probably right. I didn't think of that.
Makes me wonder if it's possible to adhere a thin metal foil (~1–2µm) to a Mylar film (~4µm, maybe?) such that it's both durable enough to survive extended periods and low-profile enough to maintain its flexibility. That way, you'd keep the low electrical resistance of the thick metal foil, but with the added durability of the Mylar as a backing.
Any ideas?

 

[Barry Hufker]

I encourage you to think differently. When I was younger, I wanted to create an optical ribbon microphone. Using a reflective ribbon with a focused light shining on it, the sound would cause the ribbon to move, modulating the light onto an optical sensor. I had some luck with it but didn't know enough to take things farther. I feel as tho' the metal ribbon has been done to death. Personally, I yearn for something new. Maybe you can think of it and take us in a new direction!

 

[k brown]

I encourage you to think differently. When I was younger, I wanted to create an optical ribbon microphone. Using a reflective ribbon with a focused light shining on it, the sound would cause the ribbon to move, modulating the light onto an optical sensor. I had some luck with it but didn't know enough to take things farther. I feel as tho' the metal ribbon has been done to death. Personally, I yearn for something new. Maybe you can think of it and take us in a new direction!

What do you see as the limitation(s) of a metal ribbon?

 

[Barry Hufker]

I'm not sure I see limitations as much as I see a "known direction" -- something that has been explored extensively, maybe to the exclusion of other avenues because this path is so familiar. That's not to say great ribbon mics aren't being made. There have been advances in magnets (neodymium) and ribbons (Roswellite), but is there something we can do better by thinking differently?

As a reference: https://service.shure.com/Service/s/article/What-is-Roswellite-Ribbon-material?language=en_US
I think the layman's term might be an "aluminum foam" if I recall correctly...

 

[k brown]

I was surprised this sort of thing wasn't developed further.

https://www.coutant.org/m88rp/index.html

 

[Barry Hufker]

That's an excellent point and a great resource for this design.

 

[C.B. - Boudio]

I encourage you to think differently. When I was younger, I wanted to create an optical ribbon microphone. Using a reflective ribbon with a focused light shining on it, the sound would cause the ribbon to move, modulating the light onto an optical sensor.

Have you got more information about that? It sounds very interesting (to make myself)! (or maybe open another thread)

 

[gyraf]

Makes me wonder if it's possible to adhere a thin metal foil (~1–2µm) to a Mylar film (~4µm, maybe?) such that it's both durable enough to survive extended periods and low-profile enough to maintain its flexibility

Why not reverse the order of things, and try coating an aluminum ribbon with some high-strength polymer - like powdercoating or similar process where application layer thickness can be well-controlled?

Would probably add too much to the mass of the ribbon anyways - but perhaps worth pursuing anyways?

(for the optical approach, these always tends to be too noisy to be really useful as front-end transducers - somehow the at-least-1000:1 ratio (60dB-ish s/n) is really hard to reach with light. Just look at (listen to) optical film sound, that's probably how far you can go in that direction)

/Jakob E.

 

[Barry Hufker]

That was one of my problems — keeping “errant” light out of the sensor. The other was the light sensor wasn't linear. I don't know how much has changed in the fifty years since I tried the design. There have, of course, been attempts at optical microphones over the years by others. I'm sure an internet search would turn them up.

 

[Barry Hufker]

@C.B. - Boudio: it's been 50 years since I tried anything and the records I had are long gone. I appreciate your interest. An internet search on optical mic should turn up similar/other ideas. Another idea I had was a “sensitized sphere” which had a cardioid pattern imprinted on it that would pick up sound only in the sensitized region. An explanation here is too complex and lengthy. And I didn't get as far with it as I wanted…

 

[sr1200]

I encourage you to think differently. When I was younger, I wanted to create an optical ribbon microphone. Using a reflective ribbon with a focused light shining on it, the sound would cause the ribbon to move, modulating the light onto an optical sensor. I had some luck with it but didn't know enough to take things farther. I feel as tho' the metal ribbon has been done to death. Personally, I yearn for something new. Maybe you can think of it and take us in a new direction!

I love this. Years ago i played around with a liquid microphone using ferrofluid and a magnet suspended in a tube. Picked up bass like a sub kick but was the size of a chapstick tube.

At one point I had also played around with some tensioned coil wire between a pair of magnets as well. I couldn't get the spacing quite right on that though. It passed audio, but wasn't very good sounding.

Don't see why gold coated mylar wouldnt work, besides trying to crimp it. As long as the gold is making contact at both ends it should "work", how it sounds is a different story. Transformer can be selected based on the load its expected to take, don't have to use traditional parts, no?

 

[sr1200]

That was one of my problems — keeping “errant” light out of the sensor. The other was the light sensor wasn't linear. I don't know how much has changed in the fifty years since I tried the design. There have, of course, been attempts at optical microphones over the years by others. I'm sure an internet search would turn them up.

This was done quite well using a laser. They were able to listen in on a room by hitting a window pane with the laser and measuring the microscopic movements the sound in the room was imparting on the glass. Some james bond style stuff there. Something a bit more toned down might be able to work with a reflective surface and the sensor picking up the dimming from the reflective surface vibrating. If the sensor was filtered to pick up a specific wave length (that of the laser) wouldn't have to deal with errant light coming into the assembly as much, and, you could then make a device that has the reflective surface suspended with a non light permeable membrane (like a speaker with a rubber surround... just flat and shiny lol)

 

[Philbo King]

I think the optical mic idea has merit. Check the link.
https://www.sciencedaily.com/releases/2022/06/220622101415.htm

 

[k brown]

Optical Mike: my optometrist.

 

[Biula]

I love this. Years ago i played around with a liquid microphone using ferrofluid and a magnet suspended in a tube. Picked up bass like a sub kick but was the size of a chapstick tube.

At one point I had also played around with some tensioned coil wire between a pair of magnets as well. I couldn't get the spacing quite right on that though. It passed audio, but wasn't very good sounding.

Don't see why gold coated mylar wouldnt work, besides trying to crimp it. As long as the gold is making contact at both ends it should "work", how it sounds is a different story. Transformer can be selected based on the load its expected to take, don't have to use traditional parts, no?

No, metalized mylar does not work as ribbon material: too high self-resistance... pure aluminium for a 5 cm long and 1-2 micrometer thick ribbon tipically used in mikes has 0.01 to 0.1 ohm self-resistance, permitting the few microampere current developed by it to circulate in the step-up transformer primary winding.

 

[Biula]

People are often intimidated by the tiny thickness of the aluminium ribbons, hence their supposed fragility: I assure you that, with the standard care you use for a vintage condenser mike, it could withstand years of hard studio work before a ribbon change is needed. I speak from experience... ah, and of course NEVER blow strong air on it! (BTW, why do you ever have to do this to an expensive microphone?)

 

[Biula]

Why not reverse the order of things, and try coating an aluminum ribbon with some high-strength polymer - like powdercoating or similar process where application layer thickness can be well-controlled?

Would probably add too much to the mass of the ribbon anyways - but perhaps worth pursuing anyways?

(for the optical approach, these always tends to be too noisy to be really useful as front-end transducers - somehow the at-least-1000:1 ratio (60dB-ish s/n) is really hard to reach with light. Just look at (listen to) optical film sound, that's probably how far you can go in that direction)

/Jakob E.

In fact, I think this is the way Roswellite ™ ribbons are made...