Part 5 - How to make a simple Rubanoide tweeter - Finish it !

[@Stelios.Posantzis]

04:45 : I don't know if you're familiar with Fertin loudspeakers but the guy who bought the company from Michel Fertin developed the drivers a bit further and used a suspension that was basically thin rods (made of carbon?) that went across the cone and attached to the diametrically opposed edge of the cone. Not easy to describe with words,, just imagine a 3 point star to begin with and then extend the lines past the centre until you get a 6 point star. Each rod attaches to the frame on one end and to the edge of the cone in the other. I think a piece of foam (?) is used in the centre where they all cross.Anyway, back to the matter at hand: I think if you can find a suitably stiff but thin wire it might do the trick. Hmmm... it would have to be non magnetic though. I can't think of where you could find something suitable right now. I just thought I'd let you know - you might find it useful if you come across something suitable in the future.

[@joppepeelen]

well thank you ! i for once think the whole shape is kinda not working along to create a nice looking curve. but ill post a music video tonight , since they sound rather oke. but hell not owrth it in my opineon even if i can fix some problems, another kind of speaker does it better in all ways i can think off

[@joppepeelen]

some nice input by the way ! you got your stuff sorted !, i wish i had a guy near me with that much of intererest and knowledge. would make some funny projects !

[@Stelios.Posantzis]

Hmm.. I keep wondering, if it's that "easy" to make, how come there is only one company that has ever made them? They must have a drawback. I guess, construction-wise, they are harder to assemble en masse than cone drivers but there are much harder drivers to make out there. Still, perhaps the industry has just passed them by. Nevertheless, it's good you're publishing these curves as now we know what we're dealing with!

[@garethsmith7628]

what if you make the arse checks asymmetrical? any cancelling might change

[@joppepeelen]

Well asymmetrical is a good idea for the phase issue. Less for keeping the voice coil straight:( with more guidance that might work though

[@garethsmith7628]

@@joppepeelen yeah, you would need a force balancer of some kind, or maybe an adjustable offset in one side position.

[@-martintheengineer-7465]

Hi. Would you like make a video how the rubenoids sounds?

[@joppepeelen]

yeah i could spin a tune real quick ! doing as we speak ;)

[@seejayfrujay]

The diaphragm material must be shaped exponentially to minimize comb effects--semi spherical contours are trouble.

[@joppepeelen]

true , thats why all rubanoides are usually trouble. there will be comb filtering in any case. maybe less so in exponential lobs. not a fan of these drivers to be fair :)

[@seejayfrujay]

@@joppepeelen Really enjoyed the video!

[@dpro369]

how about a different material such as thin Mylar.. yeah it must be out of phase on that frequencies...

[@joppepeelen]

it must have some stability , like thicker micron that will hold shape in an arc works. or at least should. just like the comercial linaeum tweeter

[@allankvist6741]

Thinner stiffer "paper" maybe?

[@Stelios.Posantzis]

17:00 : I kinda lost you there: which tweeter/planar are you comparing it to? Is it something you've bought or is it a driver you built? I'd say, from watching your videos, I think rubanoides seem far easier to build for diyers than other types of drivers, especially electrostatics. Perhaps they may be more work but conceptually at least seem easier to understand, so maybe this is their main advantage.

[@joppepeelen]

i personal think any speaker is more simple then a rubanoide. i know i etched the coils and such and this is not something any guy can do if they dont have the equipment. but since i do... a planar is more easy. even an esl is more easy. but then again money is spend in trannies.. with the ruba it is spend in metal/magnets/ and the ability to make some coil. and its dangerous to make a big one

[@Stelios.Posantzis]

Well, with ESL's you have the resistive layer, the high voltage, the transformer... it's a lot. The stretching.. that alone has a few secrets. I hadn't realised planars were that easy to make until I watched you videos. I think that if I watch them again, it might even alter my opinion of them (very slight chance but you never know)!

[@joppepeelen]

@@Stelios.Posantzis it sure has problems as well, some are the same as the esl's tension wise. and maybe even a few extra. but in general the construction is easy. of course there are all kinds of tiny thing you have to keep in account but that goes for all speakers im afraid. i just think these are the most basic in materials ,money. on the other hand an esl; might have more components... the result if usually rather good whatever you do. but if you want to replicate something or want to reach a certain goal. things might go to shit. like matching output etc. as well as reliability

[@Stelios.Posantzis]

Yeah, it's hard comparing apples to apples with these things: too many factors differ. Usually, the only goal that remains the same doesn't offer much help, i.e. "sound" per pound spent. Different speaker technologies have sound characteristics which are different enough to make this comparison impossible.

[@fullranger3435]

First off, you're doing amazing work. It's really mind-refreshing watching your videos. Let me insist on something: The rubanoide is a quirky sort of a dynamic driver, where the magnetic gap, from a cylidrical slot has been made into a one-plane, flat slot and the cone/foam(front suspension) have been merged (perhaps including the coil former too) into this ass-cheeky paper curves. So, do expect quirky measurements. The new "cone", also, is terminated only at the sides, leaving the moving edges up and down free. I shall, from a theoretical perspective, insist on your, rather, trying to bring it closer to what it really is and is supposed to be: A simplified dynamic driver! Make a normal, stiff, flat former to cary your coil, glue it straight onto (one or two) flat driving surface(s) and terminate the periphery conventionally, with a softer material (foam or mylar might be tried). I think Sony had made one such driver in the past, it was square, pistonic and used two parallel vertical "voice coils".

[@joppepeelen]

:) in short you mean it is a dymamic driver with a few handicaps? Or that i made it different ? Since i think i made what you described. About the idea with the flat service and flat coil :) i kind of made that in the past. kzbin.info/www/bejne/hX-yqZZnpZWLeKs But a 90 degree angle straight on the coil is never a good idea to transfer movement in my opineon in terms of stiffness. That the beauty of a classic cone shape no 90 degree bends in there. Yeah you could make one extra pole piece and use a rectangular sort of coil. But then ur back to a conventional driver with worse magnetic field compared to the conventional method :) i simulated both once in femm.

[@fullranger3435]

@@joppepeelen Exactly, it's a sort of a dynamic driver with a few handicaps. No, you made it correctly for a rubanoide. Perhaps it can sound decent or even great, after more or less tuning and refinements. I saw your DML(what does it stand for?) video (but very briefly) AND I was surprised to see you've already made almost what I meant!! My comments: 1) The flat boards/sides are perhaps too thick/heavy. 2) their termination/suspension at their far left/right edges is...nonexistent! I'd expect a rigid square frame and some foam or even paper tape (like in the middle line), holding the outer rims of the boards onto the frame, like the circular rubber or foam suspends the cone from the circular frame of a conventional driver. The possible advantage of such a design of a dynamic driver would be the implementation of a slim and...loooong (tall), dynamic, one driver, almost fullrange line source. You could also make the central connection of the former and narrow sides in a stiff "Y" pattern, turning the thrust/pull into a more pistonic one. (as it is now, it's like the central, long "piston" moves the sides like doors, forth and back. Think about it. You've almost done it, partly at least. Now, for the limitations of the magnetic gap (big) width, well, I think the goal is to make a prototype that demonstrates the potential of the design. Refinements and further developements are usually done at another (industrial) level. I believe the gap can be brought close to that of a conventional midrange cone-driver, at an industrial level of production. Light and stiff materials could be used to ensure a thin, long, and absolutely flat former/coil carrier. (I also saw it measures very well already).

[@joppepeelen]

Well dml stands gir distribute mode loudspeaker. That is the reason why there is no suspension. Since it creates resonances that mske up the whole response. Also the reason why both panels ate not exactly the same to create mire modes and thus flatter response. Its the same as those exciters do or nxp except that thd narrow strip in the middke supplys 15k and up since thats where they ususkky fail

[@fullranger3435]

@@joppepeelen So, I see, bending wave transducer, in other words, like the Manger and Goebel. Thus the stiff, non-parallel, asymmetrical "terminations". If it works good this way, OK. But why not try it as it's rather supposed to be?

[@allankvist6741]

Print some lines for aligning

[@joppepeelen]

yeah on the sides maybe. the coil itself has lines for aligning. did not print on the outer flaps.