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Old 14th October 2012, 07:28 AM   #31
ondesx is offline ondesx  France
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Join Date: Apr 2008
Hey Bernt,

do you have an idea of the sensitivity of your build with the ESS replacement diaphragm ?
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Old 14th October 2012, 10:49 AM   #32
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I dont have a calibrated microphone,but in post 13 in this tread i compare it to a speaker i know data of.In my system i use a 5" seas midrange and limitets the Ess clone 8 db.Its difficult to determe sensiliby on a dipole.

Pleace ask for details.

Bernt
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Old 18th October 2012, 08:44 AM   #33
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I have tried to make a diaphragm with a sort of plastic .It is used to laminate a sheet of A4 paper and is app 60my thick.As i heat it to 170 c.placed in a form from heatzink,and cool it ,it keeps its shape.
[IMG]Click the image to open in full size.[/IMG]
[IMG]Click the image to open in full size.[/IMG]
I have made 2 sizes,and they both deforms due testing as temperature goes up.
[IMG]Click the image to open in full size.[/IMG]
Green is the large one,blue the smaller ,and red is Ess .
Sensivity is quite low,it is improved with 2 pairs of magnets extra.
[IMG]Click the image to open in full size.[/IMG]
I got to have other materials to continue,but it seems to be a difficult task to make a diy midrange AMT.

Bernt.
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Old 25th October 2012, 03:27 AM   #34
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Why not just use a ESS Great Heil?
The best ones IMHO are the 17 pleat AMT3 units.
Bullet proof if you cross them properly, and fuse them.
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Old 25th October 2012, 06:26 AM   #35
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If you look at the first page you see i use the one from ESS,i tryed to make one myself to make it able to go lower.

Bernt.
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Old 25th October 2012, 07:58 PM   #36
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Quote:
Originally Posted by båndsei View Post
If you look at the first page you see i use the one from ESS,i tryed to make one myself to make it able to go lower.

Bernt.
Sure, I get it.
I would recommend using a transition driver-such as the ESS AMT3 used.
The Eminence Alpha 6A works well, and the Aura Sound NS6 255-8A as well.
IMHO you are trying to get the Heil to do too much.
Oskar was a brilliant man- I think he probably would have figured it out.
Regardless-good luck!
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Old 30th October 2012, 06:13 PM   #37
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Hi, I'm new to this forum, though I have been watching from a distance on some topics for some time.

I have had an off and on project making a hail tweeter, Mine is a bit different in that my magnetic structure is more like what Adams use in there tweeter. The other difference is I'm also trying to horn load both from the front and back of the unit, the back being for low frequancies.

By loading the back and front, this seems to help with controlling the resonance of the ribbon. Both horns are tratrix in design.

I have the advantage of owning a vinyl cutting machine that I used cutting sign vinyl so making the aluminium traces.

I have changed my ribbon material over towards capacitor film (aluminium coated film) to improve general quality and efficiency of the unit. These films are very thin and I chemicaly remove the excess aluminium from the film.

Also in the next generation of the ribbon is to create special hinges for the pleats helping to allow the trace to move in and out in a linear movement, and possibly using beryllium traces instead of aluminium if I can afford the material. Beryllium is one of those magical materials that has the density of magnesium, conductivity of aluminium and the stiffness of tungsten. This would help keeping the pleats flat while moving, helping keeping the resonance down and again improving efficiency.

Because of the changes to the ribbon each time I change the design, this also changes how my horn parameters are, so I decided to make the changes of the driver first, then concentrate on the horn design afterwards. But all in all I'm trying to create a full range unit and to avoid any type of cross-over.

The interesting point of design in the adams unit is that fact that they don't seem to have any iron in their units - they use rare earth magnets on the front and back of the units shaped in thin bars. And they do sound very nice, just a bit too expensive for me and the fact its only a tweeter (2.5Khz xover)

I will keep you posted on progress. If you want any pics let me know and I will post them .

Steve
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Old 30th October 2012, 06:52 PM   #38
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I ´d like to see some pic´s,
How do you fold them and keep the shape.

Bernt.
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Old 30th October 2012, 08:13 PM   #39
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I'll gather my pics up and post them. to keep them straight I made myself a jig not unlike yours to fold them up.

I have access to a cnc machine so I machined out a male/female piece with the thicknesses of the trace and two layers of film (first prototype) but it was a real pain in the *** trying to fit the ribbon in the jig without tearing it. I would then glue the ends up using silicon adhesive, let set then pull it apart

In my next prototype I will be inserting steel rods where the hinge point will be and weaving the ribbon through. I might leave them in there to see if they will smooth out any magnetic anomalies that exist.

By doing this I can change the mechanical resonance of the ribbon which will change the electrical resonance of the system. Add to that an adjustable bottom piece (where the bottom of the ribbon is attached to ) to fine tune this. I learned this trick from how ribbon microphones are fine tuned.

I'll post them later tonite. I'm not at my pc that has those photos.

Steve
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Old 31st October 2012, 12:42 PM   #40
ondesx is offline ondesx  France
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Hi Bernt,

I did some trials, a couple of years ago, with the AMT from Precide (Switzerland)... I never got less than 700 Hz as a lowest cutoff using LR filters with 24 dB/octave !

Somebody (RayCtech) seemed close to "great Heils" with a very low cutoff frequency... But I wonder if he reached his goal !...
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