Diy AMT

[ilardi]

How fine a pitch line do you need? You can go pretty fine with an inkjet printer and photoresist. I have not tried it but I think I have heard that 5 mils is doable.

 

[SEdwards]

I expect the relative error to be greatest in the folding, which it seems is always by hand, so the pitch shouldn't be a real issue. I think that planars require a finer pitched trace since it needs to be artificially lengthened for high enough ohms.

Try the IDE cable method that I mentioned for a quick test, you can draw by hand with rather nice precision.

 

[WrineX]

wow , this all looks great, really got my hands itching. i might look for some neo's to!

 

[båndsei]

I am posting in this forum too:HIFI4ALL Forum: Diy AMT
Here my latest

And messurements too.

Green is DIY Blue is ESS Heil amt.

Bernt

 

[SEdwards]

Wow you must be very pleased with yourself. I haven't had a chance to make a diaphragm yet because of my urgent thesis completion, but I have messed around with folding test sheets using cable ties to space the pleats.

Can you share any tips for cutting the aluminium without tears? What is your preferred method? Using water to make it stick to paper seems to help but perhaps there's a better way.

 

[WrineX]

looks stunning, bot in real life photo and on the measurement, you made a better one then the original

 

[ticovski]

I am posting in this forum too:HIFI4ALL Forum: Diy AMT
Here my latest

And messurements too.

Green is DIY

Blue is ESS Heil amt.

Bernt

Great work!

Green FR looks good and promising!

My goal is F3 around 300 Hz. If it is achievable with ribbon then it must be achievable with AMT. But longer one.

What are your listening impressions comparing to original AMT?

 

[SEdwards]

A long AMT is an attractive possibility, since it could be pretty narrow then. Less folds to make but each would be a bit tougher to complete.

 

[båndsei]

Yesterday i was a happy man,mesurements where stunning.
Today...

Red is ESS, blue diy.
Yesteday I mesured at 10cm. distance.
Today at 40cm distance as i usual do,and with a 40cmvide baffel.
Any comments?
I could make a longer AMT,but have to make new tools.

Bernt

 

[SEdwards]

For the ESS it says 'horn' - is there really a horn or just the same baffle?

 

[ticovski]

Yesterday i was a happy man,mesurements where stunning.
Today...

Red is ESS, blue diy.
Yesteday I mesured at 10cm. distance.
Today at 40cm distance as i usual do,and with a 40cmvide baffel.
Any comments?
I could make a longer AMT,but have to make new tools.

Bernt

I think there is a reason for measurement standards such as 1m x 1m baffle, 1m mic distance, asymmetric driver placement in baffle, etc

Since you have all the needed equipment and experience that should not be a problem for you.

Longer AMT- absolutely. I'm thinking to start with 28-30 cm.

 

[WrineX]

its still not bad, just indeed make measurements at 1 m so you wont be disapointed with real results. but also be ware of the room interacting much more so just use it to see really how low it can go, and not so much for the upper frequency response or humps and bumps. also when you see a nsty bump try moving the mic a little to left right front back. to see what happens because it could well be a reflection of some sort. wich has nothing to do with ur driver. outside measurement would be even better. fire it upwards if posible, in a big garden ?

 

[Paul W]

Here is "baffle" I use to take measurements more representative of driver only. Driver is smoothed to carpet floor with sheets of 1/2" wool felt, mic above.

 

[solhaga]

Here is a drawing in femm.shoving magnet polarity:

Bernt

I´m experimenting with another magnetic setup for AMTs based on what I´m been working about making bass panels.

So I´d like to correlate your simulation with the one I´ve done on your setup.

I get this field intensity:

Is it more or less what you get?

 

[båndsei]

Exactly the same.I have made some adjustments to get stronger and more liniar field.

I have used 12x12mm iron.Active diaphragm is 28mm.

Using 12x12 it is posibly to place the frame between the magnets.Frame, 5x4mm wood, is not on drawing.

Sorry square showing diaphragm is named steel , it has to be air.It affekts mesurements

Bernt,

 

[båndsei]

Here the right pictures.

 

[solhaga]

Thanks Bernt! Especially for the last update, it makes more sense with air in the gap and a B.n plot

I understand now that yours is the engine to use.

My idea of using a flat setup for sure has a more linear field, but there is still the back wave to consider.

b.n plot 3 mm in front of magnets:

b.n plot 6 mm in front of magnets:

Of course has the b.t field has to be considered as well:

So I guess that configuration goes down the drain.

 

[båndsei]

What happens if you remove the iron.Air or alu (non magnetic)

Bernt

 

[solhaga]

Not much really.
I have to shorten the membrane to only cover half the width of the magnets in order to get in the vicinety of a b.n/b.t ratio of 10/1.
I don´t think that´s good enough. The membrane will have too much movement "in and out".

 

[solhaga]

Looking at your configuration a little bit, I did this simulation:

The question is if it´s okay with such a large variation over the gap.
That the both sides in a V that produces the soundwave are influonced by slightly different forces doesn´t matter.
Worse is that the soundwaves that are produced in the middle of the gap will have much less amplitude.

b.t field looks well though: