Diy AMT

[paulfx]

These nude pictures actually look better than the Duchess sunbathing.

 

[båndsei]

I have made a diaphragm myself.It messures not too good:

Blue is diy ,Red ESS.I have increased level 8-9 db. for diy model.

Sounds ok.
Bernt.

 

[brunob]

This is the first time I am seeing a home made AMT diagphram. This is not bad for a first try. My first one did measure awful and I abandoned it.

I think that you could improve the sensibility by using many more aluminium stripes since the magnetic field is present everywhere along the diagphrame.

Bruno

 

[båndsei]

The 3 stripe you see on the picture are 30 my and made for keeping membrame in shape and resonance damping.

This picture shows the "coil"

Bernt.

 

[båndsei]

I have been asked wich parts and material i used for my Diy AMT.
Diaphragm is from parts express:ESS Heil 1107 AMT-1 Replacement Tweeter Diaphragm 264-602Diaphragm messures :140x40x4mm.
Frame is a bit longer. I placed some rubber/foam in top and buttom.
Magnets are from Hyab in Sweden:HYAB Magneter: Block N36 70x10x6mm Ni - M5780 Neodym-magneter/BLOCK 70x10x6mm. neodynmium
Steel 10x10x143mm. Alternative angeled steel 15x15mm. or simmular.
Magnets have to be placed with correct polarity
I have a tread in a Danish site:http://www.hifi4all.dk/forum/forum_posts.asp?TID=94738&PN=1 Pleace note that there is two different models.
Pleace ask for further details.
Bernt.

 

[båndsei]

Here is a drawing in femm.shoving magnet polarity:

Bernt

 

[Grumpy_Git]

Very nice bernt.

I have also made diy diaphragms, but you r work is much more professional than mine.

I used thin aluminium foil for the "coil" and two different thickness of mylar for the skin of the diaphragm, from memory it was 2 and 5 micron but i would have to check.

What material have you used for the coil and skin?

Nick

Then i bought a house and had a child so i never got to test them. I will one day.

 

[båndsei]

I used alu/paper: alu 7my = 7/1000mm. and paper 10-20my.
"Skin" microporre tape.´
It is a quite hevy and performs not as i hoped,so i am trying with microwaveoven skin and alu foil.

Bernt.

 

[RK1]

perhaps it will be of topic - but:
- I'm not sure the distribution of magnets for the best EM field distribution
- I'm not sure whether this membrane system - magnets - is appropriate.
- Can see the design on this page www.dahlbergaudiodesign.se
(http://www.dahlbergaudiodesign.se/del1/del1.htm)
Have a nice day

 

[båndsei]

I have tried with soft skin,microwaveoven ,and it did not work:

It was too soft and the coil shorted as i messured it.
I have seen this magnetsystem before ,and i think it is only for ribbons.Thoug it could be used with a different magnet polarity.

Bernt

 

[ondesx]

Hey Bernt,

do you have an idea of the sensitivity of your build with the ESS replacement diaphragm ?

 

[båndsei]

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

 

[båndsei]

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.

I have made 2 sizes,and they both deforms due testing as temperature goes up.

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.

I got to have other materials to continue,but it seems to be a difficult task to make a diy midrange AMT.

Bernt.

 

[automaticmojo]

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.

 

[båndsei]

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.

 

[automaticmojo]

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!

 

[Steevb]

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

 

[båndsei]

I ´d like to see some pic´s,
How do you fold them and keep the shape.

Bernt.

 

[Steevb]

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

 

[ondesx]

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 !...