Why is the ribbon element corrugated?

A

Aaron_Kellogg

New member
yeah so the title basically tells it all. I was wondering why the element of a ribbon mic was corrugated. My initial guess was that it has something to do with giving more surface area for the air and magnets to interact with but thats just a guess. anyway, if someone want to satisfy my curiousity that would be awesome. thanks
 
So that it's stretchy. Otherwise the difference in length between slack and tensioned would be too small to control.
 
apl said:
So that it's stretchy. Otherwise the difference in length between slack and tensioned would be too small to control.
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Are you sure there aren't any other reasons? When I tensioned a flat piece, it seems like most of the highs were pulled out and when I folded it, the highs were brought back in. Maybe I just imagined it...
 
Corrugation the element does 2 things. 1. It allows more freedom for the element to move between the magnets. 2. The corrugation makes the element a "spring" that can be tensioned properly for best frequency response. Thats why they're more sensitive to wind or blowing into the mic. The thin ribbons can easily be stretched, destroying the functionality of the element.
 
And to reiterate what Marik pointed out in his earlier post - ribbon corrugations are necessary to reduce transverse resonance modes in the ribbon that, left uncontrolled, would impart frequency response variations at high frequencies.
 
MichaelJoly said:
And to reiterate what Marik pointed out in his earlier post - ribbon corrugations are necessary to reduce transverse resonance modes in the ribbon that, left uncontrolled, would impart frequency response variations at high frequencies.
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i would also speculate that "Chip lovers have come to know that “R R R [Ribbons] Have Ridges!” The thick ridges of [ribbons] help hold more great potato chip flavors and stand up to the thickest dips."
 
MichaelJoly said:
And to reiterate what Marik pointed out in his earlier post - ribbon corrugations are necessary to reduce transverse resonance modes in the ribbon that, left uncontrolled, would impart frequency response variations at high frequencies.
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Mr. M. Joly,

I am not sure I understand your message or can make anything out of that, as what you are writing does not make any sense... at least to me. If you don't mind I'd like to clarify and bring to your attention a few points:

1) What do you mean by saying "REITERATE my earlier post"? I don't think I ever mentioned anything about "transverse resonance modes", as well as I DID NOT mention anything about "frequency variations at high frequencies".

I would greately appreciate if in future you will be kind enough to be more careful and not put words into my mouth, as it gives wrong impression about what I know, say, think, or write. It also gives a wrong impression (at least to professionals or people who understand something about microphones) about my competency in the field of ribbon microphones, to which I dedicated many years of my life.

2) May I suggest the fact that the "transverse resonance modes" is a completly separate and unrelated issue, and is a topic for completely different discussion.

3) Likewise, "frequency variations at high frequencies" is yet another issue, which BTW, is completely unrelated to the current topic (i.e. "why is the ribbon microphone corrugated"), or for that matter my post. In fact, this is a topic for completely different discussion, as well.

Before you post those nonsenses, I'd suggest you whether educate yourself, check your sources, or even better, make some experiments, putting both, uncorrugated and properly tuned ribbon of the same dimentions (of course, the corrugated one will be slightly longer, however, it is not much of our current concern, in this case and at this point) on so called Gayford bridge and report here what difference did you observe in term of resonances and frequency response, you were talking about.
Let me guess, those experiments might quite surprise you and also give some more understanding as for internal processes, which occure in ribbon microphones.

Best regards, M
 
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Marik,

It appears I've offended you and I apologize for that.

Actually, I intended my statement to be a show of support for your earlier comment, (a very effective metaphor by the way) in which you said a ribbon without corrugations is like a marimba bar that would "resonate like crazy any time sound waves hit it" as you put it.

My use of the word "reiterate" means to "say again" your point about the need to control resonances in the ribbon by means of corrugations.

My intention was to express agreement and not put words in your mouth, but since you feel that I have, I apologize specifically for effect my words had. But I really don't think a single sentence from me expressing agreement with you, using slightly different wording, is going to cause people to question your competency in the field of ribbon microphones. Your long history of informative and helpful posts on this subject far outweighs the single sentence of mine you quote.

Re: Transverse resonance modes - my statement was paraphrase of the BBC Engineering Monograph No. 1 which discusses the development of the microphone which came to be known as the Coles 4038. (I believe you're familiar with this document).

I'll quote now from section 2.3.6 Corrugations - "At the higher frequencies - in the present instance, above about 3 kc/s - the response of the microphone is affected to some degree by transverse resonance modes of the ribbon; the extend to which these modes are excited depends partly on the degree of accidental asymmetry of the the ribbon, and the result is therefore not always under control. Consistent performance can be achieved by using corrugations of fine pitch...the ribbon in the final design was formed with twenty corrugation per inch but these corrugation were pulled nearly flat on fitting; with this arrangement, sagging of the ribbon is prevented, while the production variation in high-frequency response is held within about +/- 1/2 db."

Rather than my original statement being nonsense, I view it as a concise summary of the BBC paper regarding the use of corrugations to control transverse resonance in the ribbon and thus a relevant answer to the original poster's question "why is the ribbon element corrugated?" I do appreciate your suggestion that I conduct Gayford bridge experiments myself, but I'm going to trust the good work the BBC did back in 1951 on this subject and leave it at that. best, MJ
 
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MichaelJoly said:
Marik,

It appears I've offended you and I apologize for that.

Actually, I intended my statement to be a show of support for your earlier comment, (a very effective metaphor by the way) in which you said a ribbon without corrugations is like a marimba bar that would "resonate like crazy any time sound waves hit it" as you put it.

My use of the word "reiterate" means to "say again" your point about the need to control resonances in the ribbon by means of corrugations.

My intention was to express agreement and not put words in your mouth, but since you feel that I have, I apologize specifically for effect my words had. But I really don't think a single sentence from me expressing agreement with you, using slightly different wording, is going to cause people to question your competency in the field of ribbon microphones. You're long history of informative and helpful posts on this subject far outweighs the single sentence of mine you quote.

Re: Transverse resonance modes - my statement of was paraphrase of the BBC Engineering Monograph No. 1 which discusses the development of the microphone which came to be known as the Coles 4038. (I believe you're familiar with this document).

I'll quote now from section 2.3.6 Corrugations - "At the higher frequencies - in the present instance, above about 3 kc/s - the response of the microphone is affected to some degree by transverse resonance modes of the ribbon; the extend to which these modes are excited depends partly on the degree of accidental asymmetry of the the ribbon, and the result is therefore not always under control. Consistent performance can be achieved by using corrugations of fine pitch...the ribbon in the final design was formed with twenty corrugation per inch but these corrugation were pulled nearly flat on fitting; with this arrangement, sagging of the ribbon is prevented, while the production variation in high-frequency response is held within about +/- 1/2 db."

Rather than my original statement being nonsense, I view it as a concise summary of the BBC paper regarding the use of corrugations to control transverse resonance in the ribbon. I do appreciate your suggestion that I conduct Gayford bridge experiments myself, but I'm going to trust the good work the BBC did back in 1951 on this subject and leave it at that. best, MJ
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First of all, for better and deeper understanding all the processes in the microphones, as a designer, researcher, or just a person who services ribbon microphones, I am used to question and check for myself every single point I read, even in such a comprehensive document as BBC Monograph. That's the reason I took a liberty to suggest you to check the motional impedance of the ribbon on the Gayford bridge for yourself, as I thought you would be interested to know what is going on there...

Of course, I am familiar with BBC paper (although have to admit haven't looked at it in awhile).
The problem is that although they say a lot, they do not say EVERYTHING or for some reason DO NOT WANT to say everything, and as always evil is in details.

Since you quoted it, let's get back to the BBC statements:

the response of the microphone is affected to some degree by transverse resonance modes of the ribbon

Little detail here--they do not specify WHAT RESPONSE.
Another little detail--they write that response is affected to some degree.

Next sentence--the extend to which these modes are excited depends partly on the degree of accidental asymmetry of the the ribbon, and the result is therefore not always under control.

Please observe the language they use to point out subtle influence of the modes, i.e. "depends partly", "degree of accidental", "not always".

At this point let me make a short comment on all that part.
The response they refer to should be read as TRANSIENT one (not frequency), and is affected by transverse modes QUITE A BIT.

Next sentence (you put it in bold)-- Consistent performance can be achieved by using corrugations of fine pitch

I am sorry, but I fail to see how in relation to transverse modes using corrugation of fine (or any other) pitch would affect consistancy of the performance. Transverse modes are a result of improper ribbon INSTALLATION and are independant of fact whether ribbon corrugated, or not.
For example, there are quite a few commercial ribbons which are not corrugated in the middle part at all (just a couple pleats at the ends) and are free (providing proper installed) of transverse modes and their performance is quite consistant.

The last sentence of the quote--while the production variation in high-frequency response is held within about +/- 1/2 db--in relation to transverse modes does not make any sense at all, as it is a common knowledge that while transverse resonances do affect transient response, they DO NOT affect frequency one.

All those statements look more like generic ones, when they just don't want to give away some certain information.

In light of all of the above, your statement that ribbon corrugations are necessary to reduce transverse resonance modes in the ribbon that, left uncontrolled, would impart frequency response variations at high frequencies. is innacurate and gives the folks here wrong information.
I think it is undestandable why I do not want this statement being linked to my words, as it is not what I meant, not what I wrote, and definitely is not "slightly different wording".

To reiterate, I was refferring to the resonances of the ribbon itself. I did not mean anything about those resonances as a function of transverse modes, which they are NOT.

Hopefully it does not leave any more confusion.

Best, M
 
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