Yet another Planar Magnetic Line Source, the SMAPPP


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A challenge for you: Shouldn't it be possible to have some (small amount) of iron in the membrane in the proper location and let that hold up the membrane by magnetism. In that way it should not have to be suspended on any side and not need for any corrugation... it must be possible... ;-) and then induce the (music) signal by induction so that no wires is attached to the membrane... a compleatly floating transducer.. (I'm probably a April fool :) )

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except that metal does not hover above a magnet but will end up in/on it , hehe damned i read april fools to late haha i was thinking like wtf TNT i've seen you so many times before saying interesting stuff this cant be happening haha
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well i am not sure if you watched the latest videos :) but i did use some coils out of phase. to lower resonances of the foil where it is not driven. oooooor use DC on those coils, both work... but its a waste of power at the same time :) i removed allot of flapping... but cant compare to just a stretch foil :( unfortunately
Ok, let's discuss the suspension:

Who's the sad one in the middle?

i am not sure at all, since it was gifted to me an creality Ender 5 pro. to me any 3d printer is, well a 3d printer. :) i believe a modified Ender 3 has the benchy record ;) looks like poo, but hell she did it with a affordable 3d printer that should have no potential to be the fastest :) hehe
she just came along and Nuked the previous record :) super cool !
well i think i need to use something 3d then...... i guess 360.... but to be fair i hate drawing in 3d :( but have to learn somewhere along the way :)
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Got the magnets:

So how correct is the FEMM analyzis?

I put two magnets on a 1.5 mm steel plate:

Set it up in FEMM:
MWSnap629 2024-04-05, 14_32_01.jpg

MWSnap630 2024-04-05, 14_32_18.jpg

Magnetic flow density between the magnets 1 mm above the magnets:
MWSnap631 2024-04-05, 15_29_53.jpg

Magnetic flow density between the magnets 2 mm above the magnets:
MWSnap632 2024-04-05, 15_30_05.jpg

I then measured the reality, the Hall sensor is about 2 mm from the edge of the probe.
With a distance of 1 mm in the first parts of the video the Hall sensor is barely over the magnets.
The density shifts heavily as in the first graph above. Perhaps it has to do with that the magnets are not symmetric on the steel plate.

With a distance of 2 mm in the last part of the video, the Hall sensor is right where the membrane should be.
Compare with the second graph above.

So I'd say that the FEMM simulations can be trusted.
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I hope test these membrane types/thickness:

BOPP 20 µm,
PEN 12 µm (Teonex),
Mylar 2 µm,
Mylar 5 µm,
Mylar 7,5 µm,
Mylar 10 µm,
Mylar 12 µm, (3M 74 film with glue),
Mylar 5 µm, (one side metallized),
Mylar 10 µm, (one side metallized),
Mylar 12 µm, (one side metallized).

The thinner membrane might be tested in a sandwich manner; mylar/aluminium/mylar.