DIYing a planar ribbon tweeter?

Hello all

I've already read Dhenry's Ribbon tweeter building project... and was gonna take on one of my own shortly... however something sort of has me wondering...

the Fountek Neo5DI has a 1 T gap as the specs say over a .6" gap... however in a 6" ribbon has a 102 db efficency

Quite high... those numbers cannot be achieved with a ribbon... in fact it's around 7 db lower for that same gap and field strength with a light mass 5 micron aluminum

It's pretty obvious that the secret is the lighter mass of the planar...

in my current plans I have a .83 T field across a .5" gap.... I would like to utilize this to the best of it's abilities...

honestly it seems quite obvious that planar is the way to go as the Neo2 has 98 db of efficency with a .6T over a freaking .25" gap :whazzat:


What exactly is used for the ribbon in a founteks' ribbon design???


For my 60-80" ribbon I would like to see it have around 109 db of efficency .... it's going to be a linesource

Edit:

Perhaps I should have been more clear.... I'm not looking for the normal planar design... but rather the ribbon design like Fountek uses... only I'm interested in how they get their ribbon so light!!
 
The SAE 8535 planar is one of the most efficient drivers. I've attached the SPL plot with, and without the compact horn. About $550

The Magnepan tweeter ribbon uses 2.5 micron thick aluminum. This is the thinnest I have seen. I have some and I can rip it with a strong breath. A 1T gap field with 2.5u AL over 81" x 0.25" will produce SPL close to 105db/meter at 1 watt. I have used 4u and 5.8u foils, and found 5.8u the thinnest that was robust enough to survive.

DUDE, you just got to drop $2K-$3K on grade 50 NdFeB magnets and 300 lbs of iron. Don't forget stainless steel tools and vises. Don't crush your fingers or erase all your disk drives and tapes.
 

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LineSource said:
The SAE 8535 planar is one of the most efficient drivers. I've attached the SPL plot with, and without the compact horn. About $550

The Magnepan tweeter ribbon uses 2.5 micron thick aluminum. This is the thinnest I have seen. I have some and I can rip it with a strong breath. A 1T gap field with 2.5u AL over 81" x 0.25" will produce SPL close to 105db/meter at 1 watt. I have used 4u and 5.8u foils, and found 5.8u the thinnest that was robust enough to survive.

DUDE, you just got to drop $2K-$3K on grade 50 NdFeB magnets and 300 lbs of iron. Don't forget stainless steel tools and vises. Don't crush your fingers or erase all your disk drives and tapes.


you have a link to that SAE planar?? also what did they do to make it so efficent?

the gap is .5" with a .75T....

I might be able to get ahold of 5 micron aluminum... but it'll cost me...

where did you find yours at??? any certain film/foil capacitors?

right now my final design looks to be a 60" ribbon with a .5" wide gap with .75T (after counting in that 10% loss due to stacking)

Edit: I believe I just found a supplier for N50 magnets for cheaper than stacking them... so now it's a 1T field over a .5" gap
 
Isodynamic planar diaphragms

You can find a number of companies that make flexible printed circuits on Kapton film as well as companies that make flexible resistive heater elements on Kapton. Kapton will probably take more heat than most any other film and is reasonably light. Many dynamic speakers use Kaptom voice coil formers. You could make use of a resistive material for the voice coil in a planar magnetic design as this would give you a nice resistive value voice coil in a small size unit. That way you can keep the resistance in the gap rather than in a load resistor. Good luck in your project. Regards Moray James.
 
Re: Isodynamic planar diaphragms

moray james said:
You can find a number of companies that make flexible printed circuits on Kapton film as well as companies that make flexible resistive heater elements on Kapton. Kapton will probably take more heat than most any other film and is reasonably light. Many dynamic speakers use Kaptom voice coil formers. You could make use of a resistive material for the voice coil in a planar magnetic design as this would give you a nice resistive value voice coil in a small size unit. That way you can keep the resistance in the gap rather than in a load resistor. Good luck in your project. Regards Moray James.


thanks for that info...

Linesource in an old old post said that Kapton was a noisy material to use for a ribbon. He said the best compromise between heat tolerance and weight is Kaladex, however Dupont doesn't make that anymore...

Teflon may work, as would Mylar... however mylar would have to be limited to around 160 degrees farenhedit of heat... which could be a problem with high power situations

Also the nice thing about mylar is that it's about half the mass of Aluminum... with a one micron aluminum lamination on it it would be easy to direct drive... but with that high of an ohm (4 or so) I wonder if it would go over the 160 degree mark...

Linesource?
 
Audiophilenoob.,

Thin aluminum films are sputtered onto mylar in a vacuum chamber. This assures good metal adhesion with the flexibility of the mylar. It can withstand vibration without developing an open circuit. This type of metalized film is used in capacitors. If you glue very thin aluminum onto mylar it is very likely that the aluminum will split from vibration and create an open circuit. The Swedish ribbon thread details how to use 3M spray adhesives to glue 5 micron aluminum onto 2 micron mylar.

I would use 4 to 6 micron pure aluminum.

When you estimated gap magnetic field in FEMM, did you read the center of the gap value to get the worst case field, or 25% away from one pole piece to get an average field.
 
LineSource said:
Audiophilenoob.,

Thin aluminum films are sputtered onto mylar in a vacuum chamber. This assures good metal adhesion with the flexibility of the mylar. It can withstand vibration without developing an open circuit. This type of metalized film is used in capacitors. If you glue very thin aluminum onto mylar it is very likely that the aluminum will split from vibration and create an open circuit. The Swedish ribbon thread details how to use 3M spray adhesives to glue 5 micron aluminum onto 2 micron mylar.

I would use 4 to 6 micron pure aluminum.

When you estimated gap magnetic field in FEMM, did you read the center of the gap value to get the worst case field, or 25% away from one pole piece to get an average field.


yes I measured the center of the gap field... 25% away from the poles it's .95 T
 
out there somewhere

Hi all,

http://www.oselectronics.com/ose_p88.htm
I saw this product and thought that it could be used to coat 6micron (.000 25") foil. Perhaps even thinner foil. I was also thinking of spraying clear urathane on thin foil.

I got one of those thermal emergency blankets and it measured a few ohms / inch. They are aluminum sprayed on mylar. Every time I see aluminum-mylar packageing I think, "could that be the right stuff for a ribbon". It has to be out there somewhere.

Does any one know a source for 6 micron foil? Something thinner than the kitchen wrap.

-Linc