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Ribbon question
Ribbon question
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Old 12th February 2018, 07:12 PM   #11
lowmass is offline lowmass  United States
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If your going to make a "full range" ribbon then you have a tall order but it can be done. about the best you can do is take a tall (5-6 feet) ribbon with a large open back baffle down to about 80 hz then over to a sub.
I have made them this way and the best result I had was with 2 inch wide ribbons and large magnets. I wouldn't use NEO magnets in this. Grade 5 or 8 ceramics are better. Neos are waaayyy too expensive in this size anyway.
I have taken them "full range" (no subs). With EQ and wide baffle they will go low, quite low in fact BUT really only loud to about 50hz. However it was the best quality bass/mid I have ever heard. Ever.

You need to keep the gap between ribbon edge and magnet face small, about 1mm or less to avoid loss of low frequency sensitivity.

It can be done with a ribbon only 1 inch wide too BUT the 2 inch wide works much better at avoiding ribbon flapping around at low freq. and will play louder. HOWEVER now you may find that the dispersion of a 2 inch is not what you are looking for and you will need another ribbon less wide next to the 2 inch.

Combined surface area of many smaller ribbons will give good low distort, BUT one big ribbon avoids the problems with interference effects of multiples. I do not have enough real world side by side comparison of one long VS many small to say for sure if its better one way or other but I suspect problems at higher freq. with multiples..


The magnet you show is a multi pole magnet and is not suitable for ribbon. You need a more standard rectangular magnet that has one pole per side

I have tried a few strange ribbon configurations. The one you show is interesting and I dont know for sure BUT I suspect its best to stay with the classic ribbon / magnet arraignment.

I would not get too stressed over distortion. Big ribbon will be low, AND I have been building ribbons for 30+ years. The best sounding ones are not always the lowest distortion ones

Last edited by lowmass; 12th February 2018 at 07:21 PM.
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Old 12th February 2018, 07:21 PM   #12
hellokitty123 is offline hellokitty123
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Quote:
Combined surface area of many smaller ribbons will give good low distort, BUT one big ribbon avoids the problems with interference effects of multiples.
Is the interference due to spacing or some sort of mismatch?

I want to start off with a headphone ribbon before I move to speakers, do you have any feedback on that?
Also do you have any feedback on the six arm ribbon? To my eyes it seems to avoid the flaws of normal ribbons, does that seem correct to you?
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Old 12th February 2018, 07:52 PM   #13
lowmass is offline lowmass  United States
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Originally Posted by hellokitty123 View Post
Is the interference due to spacing or some sort of mismatch?

I want to start off with a headphone ribbon before I move to speakers, do you have any feedback on that?
Also do you have any feedback on the six arm ribbon? To my eyes it seems to avoid the flaws of normal ribbons, does that seem correct to you?
Its a spacing issue mostly. BUT look at the Infinity IRS. Some earlyer versions have multiple small "ribbons". I havent heard them but perhaps if enough distance to the listener the multi driver ting is not a serious issue not sure really.

Yes good to start with small headphone ribbon. You will get good hands on experience with making the diaphragm. I have made a few ribbon headphones and even some planer magnetic ones.
I would say just start with the crudest easyest way to throw together some cheap frame carved from any wood and hot melt glue some magnets down. Glue a strap on them so it fits over your head AND then go about making many ribbons of different construction to fit. Keep it simple and crude. Then once youve learned a thing or two you can build nicer ones.

When you say "flaws" what do you mean specifically??

I see little if anything to make me interested in the six arm. I wouldnt bother with that construction.

BTW by far one of the biggest hurdles for a DIY guy and ribbons will be the adhesive type and thickness if making laminated plastic backed type diaphragms. Spay adhesives like super 77 actuall work quite well BUT you need a full can to get the pressure to spray an even coat AND you need to keep the coating very thin. Yes of course it will work if not exact BUT the fidelity and sensativity suffers. And super 77 turns to dust in a year or two.

Basically plastic backed ribbons come alive when the plastic backing and the adhesive are less than about 8 microns. There really isnt anything commercially available to get that thin but a very light coat of super 77 spray and mylar backing around 6 -8 microns will get you there

Last edited by lowmass; 12th February 2018 at 08:10 PM.
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Old 12th February 2018, 08:00 PM   #14
hellokitty123 is offline hellokitty123
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Quote:
When you say "flaws" what do you mean specifically??
In my limited knowledge, I understand that corrugation is the cause of resonance frequencies in the typical ribbon. The 6 arm ribbon doesn't look like it needs corrugation at all. Aside from that it is in the magnetic field of 12 magnets controlling all sides of the center "transducer" which should give extremely good control and response.
Which leads me to believe it can be used to produce a larger range of frequencies than typical ribbons. Tell me if I am wrong.
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Old 12th February 2018, 08:26 PM   #15
lowmass is offline lowmass  United States
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Originally Posted by hellokitty123 View Post
In my limited knowledge, I understand that corrugation is the cause of resonance frequencies in the typical ribbon.

The size of the corrugations can influence the response in the treble region. Small corrugations will bend more easily and therefore the resonance will be at a lower freq than larger stiffer corrugations. This usually is seen as a small glitch in freq response in treble. You can play around with the size and often come to a point where the glitch is smooth enough.
That said this "problem" is mostly an issue with wider foil only ribbons. Plastic backed versions usually will be made with very small corrugations and are very flexy designs BUT they are much better damped than foil only.




The 6 arm ribbon doesn't look like it needs corrugation at all. Aside from that it is in the magnetic field of 12 magnets controlling all sides of the center "transducer" which should give extremely good control and response.
Which leads me to believe it can be used to produce a larger range of frequencies than typical ribbons. Tell me if I am wrong.
I doubt it. I see all sorts of problems with that theory. Its a complex arraignment and Im not even sure the "center" part will have proper magnet flux orientation.
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Old 12th February 2018, 08:30 PM   #16
hellokitty123 is offline hellokitty123
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I don't understand what you mean by the center not having a proper magnetic flux orientation.
If you treat the arms as 6 separate "conventional" ribbons then the center should simply act as a piston.
The equal distribution of opposing magnets around the center should cancel out the motive force from the flux in the middle I think. If not just add enough arms so that you can carefully pick the current paths until you create a field cancelling effect in the middle.

Last edited by hellokitty123; 12th February 2018 at 08:42 PM.
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Old 12th February 2018, 09:13 PM   #17
hellokitty123 is offline hellokitty123
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For a 6 arm ribbon this direction of current seems like it would do a reasonable job of flux cancellation in the middle
7Ud4qDw.png

The currents would probably be more accurately described as this I think.
9OVbb9Y.png

10 arms would give a much more even distribution of opposing currents. I don't know if it is required to go that far. The center axis is missing one symmetrical opposing current path in the 6 arm version.

Last edited by hellokitty123; 12th February 2018 at 09:37 PM.
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Old 13th February 2018, 12:50 AM   #18
lowmass is offline lowmass  United States
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Well far be it from me to hold someone back from trying strange new designs. To be honest some of the better ideas Ive stumbled on were from trying strange ideas .

However I see a few issues here.
1- its complex. complexity can make the fragile ribbon very difficult to get right. It may be a looooong process of trial and error experaments to get the bugs worked out both in construction and performance.
2- maybe theres somthing im missing BUT I do not see that senter section being driven uniformly by a clean magnet flux. I see the center section as dead weight.
3- i suspect even if it does work you will have limited horizontal dispersion due to the width.

Dont underestimate the value of simply making really crude, slaped together ribbons to get your mind thinking and give you real world knowladge of what practical to do. Of course dont be afrade to try all sorts a different ideas, but I find untill I have an awful lot of knowladge that its best to take what I got and build somthing crude that wont last but will give me a better view of the possabilities. Then things become much clearer

Last edited by lowmass; 13th February 2018 at 12:52 AM.
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Old 13th February 2018, 07:39 AM   #19
hellokitty123 is offline hellokitty123
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Quote:
its complex. complexity can make the fragile ribbon very difficult to get right. It may be a looooong process of trial and error experaments to get the bugs worked out both in construction and performance.
Yeah I was considering using kitchen foil for the 6 armed experiment. Easy to source and cut and a lot less fragile.
Quote:
maybe theres somthing im missing BUT I do not see that senter section being driven uniformly by a clean magnet flux. I see the center section as dead weight.
The middle isn't supposed to be driven by flux. The purpose of the "arms" isn't to produce sound, it's to move the center up and down like a piston. The center is supposed to be the actual transducer, like a dynamic driver shaped ribbon.
The "arms" are effectively a bunch of conventional ribbon mechanisms attached to a slab of foil in the center. So when the ribbons move the center foil vibrates up and down producing the sound.

Last edited by hellokitty123; 13th February 2018 at 07:54 AM.
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Old 13th February 2018, 01:06 PM   #20
lowmass is offline lowmass  United States
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Originally Posted by hellokitty123 View Post
Yeah I was considering using kitchen foil for the 6 armed experiment. Easy to source and cut and a lot less fragile.
The middle isn't supposed to be driven by flux. The purpose of the "arms" isn't to produce sound, it's to move the center up and down like a piston. The center is supposed to be the actual transducer, like a dynamic driver shaped ribbon.
The "arms" are effectively a bunch of conventional ribbon mechanisms attached to a slab of foil in the center. So when the ribbons move the center foil vibrates up and down producing the sound.
"kitchen foil" is fine and cheap. BTW I advise using the standard foil, not the heavy duty foil . Standard kitchen foil is around 17 microns thick, heavy duty foil around 24 microns.Many who haven't built and refined a lot of ribbons generally believe that you must use much thinner foil than what you get from the grocery store. While there are certain advantages to going thinner, there are also many disadvantages AND in the end, within reason, its largely in the execution. Heres an example, the Apogee Stage tweeter ribbon uses foil the same thickness as standard kitchen foil.

OK I see what your saying on the arms and center section. Yes it will do as you say. However the biggest reason a ribbon sounds the way it does is because the entire surface area of diaphragm is driven directly. With this arraignment the main part of the transducer is not driven directly anymore, AND the "motor" (the arms) are will be sending mechanical waves into the center from all directions where they will meet and ether cancel or add likely resulting in a ragged freq. response.

There are designs that are in a way opposite of the six arm in that instead of the energy propagating into the center , they start with the drive force in the center and the energy propagates out away from that point and is absorbed in a "lossy" mechanism of some kind, usually just a large surface area film planer with graded damping. This to avoid waves reflecting off a boundary and propagating back into the driver. Basically even a cone is made this way where the surround construction will absorb the unwanted energy.

There was a design a number of years ago that was a large, tensioned , mylar film like an electrostat BUT no drive forces over the film area. Right in the center of this large film was a small aluminum dome maybe 1-1.5 inches diameter with a long travel coil motor. The large surface area around the dome was the suspension and I believe it was damped in a graded fashion with acoustic resistance out to the edge.

Basically you had a small point source with a freq response of about 50-20khz. Anyway the energy propagates out away from the drive point and is absorbed.

Another design was a planer magnetic midrange about 2 by 3 inch square, BUT it too was rideing in the center of a much larger tensioned film that was in very close proximity to a solid unmovable surface.This close proximity damped larger motions holding the driven section in its proper place and allowing the vibrations at center to dissipate out away from that area.


NOW, having said all that and admitting that I hardly know everything ha, I would say hey give the six arm a try if for no other reason than to learn. And like I said, just about every good idea I've ever stumbled on was from trying strange things. Not that the strange thing worked BUT that what was learned brought me to something valuable that I never would have expected.

Last edited by lowmass; 13th February 2018 at 01:14 PM.
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