I had this idea for a looooong time, no steel and higher X max, and hoping for more linear movement, by the looks of it you can increase xmax allot while still have it more linear then normal single ended (2e order droped allot). in this case i went from my regular 3mm xmax to 6mm 
and some music see if we can hit the magnets... no luckl so far, res to high and xmax as well
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The membrane speed is proportional with the induced EMF (B*l*v). The voltage shows the velocity profile of membrane at lower frequency. Our can calculate the total Q-factor. If you have two panels... If you connect the second, identical bass panel and take the side by side both of speaker, I guess, the induced EMF will decreasing, because the acoustical coupling increases, if they work in phase. The better coupling means higher acoustical impedance.
Of course, I don't give a lot of works, only I see a lot of very interest theme, which gived by your new construction.
Of course, I don't give a lot of works, only I see a lot of very interest theme, which gived by your new construction.
i think, a dual coil one foil construction might be better as a sensor, since it moves in the exact same field. here front foil might be moving towards the magnet the other foil will move away from it
but how would it be driven ?
adding another layer of mangnets without joke 2 is actually the most rewarding. i got more linear response from only a single ended magnet structure, and a bigger xmax.
now i am gone try some damping see what it does 
Do you know how I came up with 6 membranes (?), first I made two drivers (for stereo) with 3 membranes each, listened to them for a while, and then the idea came to connect them with clamps, I tried it, it was a completely different effect, so I had to make another one channel for stereo but already 6 membranes.but how would it be driven ?
without joke 2 is actually the most rewarding. i got more linear response from only a single ended magnet structure, and a bigger xmax.
In your case, you can make another driver exactly like this with 2 membranes and... connect them together through a small spacer, and lay damping material between them, it works 100%. This is packaging material in two layers:
Attachments
Unfortunately, you are right.i think, a dual coil one foil construction might be better as a sensor, since it moves in the exact same field. here front foil might be moving towards the magnet the other foil will move away from it
Perhaps the two membranes are still good at very small excursion.
multiple people say this but actually its not, i know they are quite similar , but in this case i used a single motor. (magnetic structure at least) both foils use the same magnets and i think not so much like isobaric abnormalities are canceled but in this case the fact a single ended has a weak magnetic field at its xmax outward, and max magnetic field inward. in this each foil has one of these problems. combined the idea is they both benefit from each others position towards the magnetsPlanar isobaric.
in any case when putting multiple panels behind each other they still share the xmax (so max spl remains the same). for my duty making this panel just larger would be far more easy and less problems. the way i made these i was able to extend the x max from 3 mm to 6... i might go back to 5mm or so to get some efficiency back. its not huge difference. but i am not able to make the foil slam against the magnets, not that i want to but that indicated the xmax might be a bit to big for the size of panel and or resonance
I added one super thin piece of Vliseline non woven stuff on the magnets. here a measurement before and after.
Here dual panel without any damping
And here with one vliseline layer (thinest variant) on top of the magnets. you can see it actually might damp a bit to much.... so i guess i need to find the ideal Q ? maybe ill shop for some of those nylon meshes see how that fairs. one thing to note its an open baffle of course, so it might work fine if i had a baffle to begin with... its now just standing on the floor next to a LRS. i am verry curious how it will perform if i make the panels wider with a lower resonance and more tension on the foil. so it can use the max xmax, then... how it would sound if they where a usefull size, i thought about using 81-90 magnets in a bigger version instead of the 28 used now. should be pretty hefty. i saved some money on metal so i can add some more magnets
Here dual panel without any damping
And here with one vliseline layer (thinest variant) on top of the magnets. you can see it actually might damp a bit to much.... so i guess i need to find the ideal Q ? maybe ill shop for some of those nylon meshes see how that fairs. one thing to note its an open baffle of course, so it might work fine if i had a baffle to begin with... its now just standing on the floor next to a LRS. i am verry curious how it will perform if i make the panels wider with a lower resonance and more tension on the foil. so it can use the max xmax, then... how it would sound if they where a usefull size, i thought about using 81-90 magnets in a bigger version instead of the 28 used now. should be pretty hefty. i saved some money on metal
so i can add some more magnets
I added one super thin piece of Vliseline non woven stuff on the magnets. here a measurement before and after.
Here dual panel without any damping
View attachment 1299246
And here with one vliseline layer (thinest variant) on top of the magnets. you can see it actually might damp a bit to much.... so i guess i need to find the ideal Q ? maybe ill shop for some of those nylon meshes see how that fairs. one thing to note its an open baffle of course, so it might work fine if i had a baffle to begin with... its now just standing on the floor next to a LRS. i am verry curious how it will perform if i make the panels wider with a lower resonance and more tension on the foil. so it can use the max xmax, then... how it would sound if they where a usefull size, i thought about using 81-90 magnets in a bigger version instead of the 28 used now. should be pretty hefty. i saved some money on metal
I was just watching your video on YouTube before I found your post on here!
Could you explain what's the idea behind covering the magnets with Vliseline?
the idea was to get rid of the main resonance , else we got a huge peak, i can dsp that away. but normally i think doing it without is neater. in this case it might damp to much. so i either have to play with less wide vliseline or.. change it out with something a bit more open. like silk screen mesh. i bought a few sizes to see what it does.
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well i dont know did not listen to this song with them
but they wont go as low. maybe if i force them. but they might end up hitting magnets. in any case my room favors low end so. keep that in mind 