The Neil Davis Heil AMT

[kenpeter]

Originally Posted by c2cthomas

I'm with kenpeter's approach on this one - some big Neo's on the sides

My interdigital comb geometry would be entirely wrong for a magnetic field.
Magnet field must pass front to back, so the pleats can move side to side.
Static field(s) need to be parallel to those pleats to coerce similar motion.
We can't be talking of the same thing. Or can we???

I envisioned a comb of plates that intrudes fully into the pleat. One from the
front, oppositely charged one from the back, and double duty as the zigzag
support structure that forms a flat ESL ribbon into AMT pleats.

[paulfx]

Wow! From the mists, another large Heil, covered with silicon glue and with a custom diaphragm to boot! My wife would just have a stroke if I cut holes in the wall. Neil, I like the way you say "back when I etched diaphragms" as if you've recovered. Modern meds are beautiful...
Viewers to this thread, Neil is the dean of DIY Heils, the philosopher of flux, the prof of pleats. I am merely an NIB buff.

[paulfx]

I've really gotta get cracking and get this driver stuffed and mounted and get you all some measurements.

[paulfx]

An electrostatic AMT would mean no diffractive pole pieces in front of the diaphragm! It would also entail potentially deadly high voltages, which equals cool.
Maybe have a plasma flame coming out the top of the system?

[kenpeter]

On second thought, perhaps static combs could intrude from the sides?
Or top and bottom, take your pick....

Would automatically expose the front and back of the pleats to open air!
A pair of aluminum heatsinks is perhaps already in the correct shape???

But wether to insulate the ends of the fins that might touch the ribbon
and form the AMT pleat shape, or physically separate insulating support
structure for the pleats? Then how to assure the combs touch nothing???
Might be better the combs touch the ribbon in a known place than fiddle
with some critical alignment....

Devil is always in the details. Probably a reason if its not been done.

[c2cthomas]

I was thinking of a electromagnetic arrangement similar to this very basic concept. (Neil is most likely banging his head on the desk or wall and mumbling something like !@$!@$@#%^ didn't you read my stuff??)

This does not show extra iron plates used for shielding the assembly.

[kenpeter]

OK, then the assembly I am describing might look almost like that.
But the comb teeth pushed fully together, and interwoven, but not
touching...

The pleats would have to be running horizontally, as the ribbon
would be folding over the front edge of one plates of one comb,
and behind the rear facing edge of of the other.

Part of the gap between pleats would be taken up by the thickness
of the comb plates, but I don't think this gets in the way of AMT...

I am assuming your plate structure angles inward from both sides like Heil?
Mine would probably be flat faced, as there is no magnetic field to conduct.
And the ribbon will want a flat structure for folding upon anyway...

Thats assuming my idea isn't completely ridiculous to begin with...

[cuibono]

Paul - I can't find your magnets on the forcefield site...

Does post #16 show the proper pole orientation for magnets in dipole orientation? Paul's pictures make it look like the magnetic force lines pass from front to back of the assembly.

[paulfx]

Looks like they're out of stock of the flatside rectangle magnet I used - however there is another tempting model here:

http://www.forcefieldmagnets.com/cat...products_id=87

I would use one for a small diaphragm and two for a 4 inch. The problem is that these are just insanely powerful. Getting two of these in parallel on the inner pole piece instead of the one I used would require finding and marking each nominally North and South on each flat side. Keep them apart as if they were subcritical U235! Maybe a compass you don't mind ruining could find the actual north and south. Or, find attraction and repulsion by keeping one disk inside an unused 3/4" thick speaker box, the 3/4" walls keeping the magnets from sticking forever. Then perhaps glue the first magnet onto your inner pole piece, let it cure, then the next day clamp the assembly such that the second magnet cannot swing around explosively and snap together in a permanent series stack as you are assembling it.
I would cut dummy magnets out of wood and rehearse how I would clamp and glue them so either N-N or S-S was glued to the inner pole. They are that dangerous. You would need these test jigs anyway to grind down the inner pole piece so the components fit inside. When the inner assembly is dry, then you can "feed the alligator," fit it inside the outer pole.
Neil used 4 smaller NIB cubes in series-parallel in each small AMT and saved money. Four of these in a pair of tweeters would be some $120. My single one cost $40.
I feel it's worth it to nail the diaphragm gap with a bunch of flux.
And yes, the Davis design flux goes front to back and then back around to the front.

[paulfx]

Went to see "Julie and Julia" with my wife last night - and I couldn't help noticing a parallel with Neil and Oskar. Sure, wrong genders, no "Mastering the Art of German Transducers," and no TV show. And instead of a dish a day, more like a magnet assembly a month.
Has anyone here ever coresponded with Dr. Heil before his death?