Diy AMT

[solhaga]

That´s great news, Bernt.
Did you get any indication if it is orderable and in what quantities?

Just a quick check: Have you considered the Phote resist method?
It would require a pattern on plastic but it can on the other hand be re-used.
Using a wide and shallow bowl, you don´t need the "Etsaggregat".

I used to etch my own circuit boards back in the seventies that way.

 

[båndsei]

Yes i have thought at that.
But i have read about another way of doing that:http://www.diyaudio.com/forums/solid-state/221741-dx-blame-st-together-dx-super-77.htmlPost 764.
Use a laserprinter to print the pattern and a laminating machine to transfer it to the alu/mylar.The machine has to be adjusted to a higer temperature.

Bernt.

 

[solhaga]

Can you try the white benzene on your kapton and let me know how quickly the glue comes off vs the rubber adhesive on the polyester tape?

It took a couple of minutes to remove the adhesive from a 185 mm x 480 mm membrane. I tested some kapton, and it should take the same amount of time.
One problem is that you cannot easily see when the adhesive is removed on kapton.
With the 3M film it is much easier as the polyester is colorless and the adhesive yellow.

 

[SEdwards]

It took a couple of minutes to remove the adhesive from a 185 mm x 480 mm membrane. I tested some kapton, and it should take the same amount of time.

Thanks very much for checking this. I suppose that I'll have to get some of that solvent. This kind of kapton is of course a bit thick and so on, but it's still interesting (and cheap) to play with. I figure that I can use it to much some planar headphones drivers too - the diaphragm of the Fostex T50rp is rather heavy but still performs wonderfully.

I tried printing on Al as well - my laser printer did not leave a perfect trace pattern (had gaps) but that may have been from the foil not being flat enough.

 

[båndsei]

I think I still will do some tests regarding etching of alu/mylar film.
I have not asked the supplier of alu/mylar about quantities yet.Wanted to test it first.
I need some high gloss thin photopaper (80 LB) What is this in gr/m2,or thickness ?I think 12 mill or 30my.
I am not trying to get the AMT to play lower than 1khz.
I am going to make planars to get lower.

Bernt

 

[Rewind]

I have been discussing AMTs as dipoles with StigErik, and he feels the TPL-150 is too tall to be a proper dipole and prefer the smaller Mundorf AMT. The Mundorf has issues with reflections against ceiling and floor because it spreads the sound more vertical. The TPL-150 is very limited vertically, which is a good thing in this case. He ended up with the 2 meter high Bohlender RD75, that solves this problem with reflections. Anyway, what is how I got it explained to me. The RD75 is difficult to get shipped here and is very expensive. How about a 2 meter high planar as a next project? Or maybe a shorter Mundorf version.

 

[JAMESBOS]

Built a 7' high by 2' wide planar speaker, using 50 x 12.7 x 3 mm neos which was full range and didn't need a tweeter! Using MDF for the frame, no need for a crossover. Using 3 mm alu tape, easy peasy.

 

[tyu]

HENRY......Always doing great work for alll us ribbon lovers...have fun.............thanks

 

[Rewind]

Did you get to listen and even compare it to the RD75? That is quite a different design, and probably with different dispersion too. Fullrange, you say, how low did it go?

You made a lot of designs. Which one was your favourite?

 

[JAMESBOS]

I don't have any RD75's anyway. Goes down to 20 Hz. I think overall I prefer the ones with ferrites, the neo ones are a bit top heavy and are harder on the ears. I don't do any measurements as I don't have the equipment or the inclination. As I have 10 of my planars running in all channel stereo at the same time, it is difficult to measure! I am not really a technical person, I just like to build and listen. I never write enough down with all my rebuilds, I can't really be bothered at my time of life (75). I wish I was more organized, but one cannot help being what one is! At this time I am building planar headphones, which is quite fiddly especially the smaller ones. I am just waiting for my EUREKA moment, if it ever comes to get some new ideas so I can build some more speakers. Or I may just start building valve amps again, as I have a few in the pipeline!!??

 

[båndsei]

I have done a lot of planars app 135cm. high .
Here a pic of a curved model I will try to improve:
http://www.diyaudio.com/forums/planars-exotics/155811-diy-planarspeakers-15.html
I will make the res. freq. higher.I used to aim at 50 Hz,but now i think it must be 150hz.

Bernt

 

[jay53]

I have done a lot of planars app 135cm. high .
Here a pic of a curved model I will try to improve:
http://www.diyaudio.com/forums/planars-exotics/155811-diy-planarspeakers-15.html
Bernt

Hi Bernt,

How would you compare the sound of Ribbon Planar with AMT ?

Jay

 

[båndsei]

Jay 53
I have not compared them directly to each other,but the planars have more energy at lower freq.

Here I make alu/mylar foil etching:

It is made with 12/12my alu/mylar using laserprinting on glossy paper,and heating to 170 c.in a modified laminator.
Etched in HCL app. 10% strength.

Bernt

 

[Rewind]

So why not stick with planars?

 

[båndsei]

I will try to make a planar like BG 50 in two parts angeled 10' to get better dispertion vertical.
Planars have a small sweet spot.

Bernt

 

[Rewind]

Does the AMT offer anything better than the planar in its range?

 

[solhaga]

Congratulations to yet another succesful process invented on you, Bernt!
It´ll be exciting to know how it measures and what it sounds like.
I gather it would be able to take a lot of power.

 

[båndsei]

If i had a room for audio only,I would use a 2 way system with planars.But I use my living room:

It is a 3 way system with 2 amt´s angeled 10'
I am running out of 12/12 alu/mylar.I hope to make 2 80x40mm.
I have made a request for a roll at the manufactor.
The alu/mylar is made 25/12 too.It could be used for a double string layout.Like ESS and Beyma .

Bernt.

 

[solhaga]

Can you estimate the practical width that one can have on the strips using this method?

 

[båndsei]

1-2mm I think.I will make a test with 2mm strips and 1mm space.

Bernt