Air Motion Transformers (Heil's) and New Diaphragms

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C

cyclecamper

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Joined 2010
need more info about stacking Heils

cdfr said:
and a picture of my AMT1E Monitors with 2 Heils
Click to expand...

This stacked AMT speaker is extremely interesting and directly relevant for me.

I'm going to attempt a center channel speaker using the same 2 stacked Heil AMTs under an OLED flat panel TV.

Is this your own experiment, I assume?

Did you just run big threaded rods thru both units to mount them stacked?

How is the vertical pattern?

Thanks for any info you can share from your own experience...if you're still on this site (the post I reply to is pretty old).
 
L

lowmass

Member
Joined 2016
Nelson Pass said:
As I recall the original Heil diaphragms were polyethylene,
not Mylar or Teflon. These later materials were tougher,
but never sounded as good.

The original, best sounding material was made from the
packaging material for airline peanuts, and may still be
in use in the food packaging industry.
Click to expand...

Peanut package , hmmm, interesting. Bextrene ??

I think this is right. Polyethylene is better damped than the mylar thats often used now and this becomes important with a design like the AMT where the moving sections each represent quite a small dimension that must flex. I suspect however that they got away from the poly due to heat issues.



These designs could see better sound down twards 1khz if we could take care of that issue but its a fundamental problem with such a small diaphragm area(not total area, the small sections that flex).
Some claim to take them down that low but I think there are noticeable color their.
 
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VaNarn

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Joined 2010
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The current diaphragm is a constructed using a soft mylar material. The shape of the pleats is more uniform than the original polyethylene version and it can withstand more heat without deforming. The polyethylene diaphragms were coated with a damping layer and this allowed them to be crossed over at a lower frequency than the current model that uses the flexible gauze screens attached at the front and rear of the pleat apexes.
 
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lowmass

Member
Joined 2016
VaNarn said:
The current diaphragm is a constructed using a soft mylar material. The shape of the pleats is more uniform than the original polyethylene version and it can withstand more heat without deforming. The polyethylene diaphragms were coated with a damping layer and this allowed them to be crossed over at a lower frequency than the current model that uses the flexible gauze screens attached at the front and rear of the pleat apexes.
Click to expand...

"soft mylar" ??
I never heard of this. Can you give a link to a manufacture/distributor?

I played around a while back with different backing materials. by far the most nutral was teflon in its very soft forms, like used for pipe thred sealant tape.
Structurally is not good and some special tratments needed to adhear foil but it gave the smoothest response... while it lasted.

In my experiece all polyester films (mylar) are low loss materials.
 
L

lowmass

Member
Joined 2016
Thanks VaNarn

I have actually talked with Tekra a few times . They tell me they dont do the thinner films (below 1mill) wich are nessasary in these designs.
I have also looked into the Teonex film. This was driven mostly because in a design we have now under development the polyester films cannot handle the heat stress. The problem with Teonex is availability in smaller quantities.
There is a resurch facility that will sell the Teonex to you in small amounts. I think they want about 6-700$ min order.
 
C

Carl_Huff

Member
Joined 2004
kadproducts.com
I really like the big ESS HEIL AMT drivers but struggle with the inconsistent and ragged frequency response. In my experience the new diaphragms are more of a problem than the old ones from a decade ago. No two measure exactly alike and I'm not keen on the idea of measuring thru a pile to find a pair that are similar. Anybody here have any thoughts or experiences to share?
 
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