# Dual membrane planar magnetic (both active driven)

#### WrineX

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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#### neodymium

Good job! Your dual membraned model gives a chance for measuring of averaged membrane speed (one driven, one sens), without parasitic electric coupling.

#### neodymium

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.

#### TNT

Paid Member
Good going!! Hifi-Cat approves

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#### havun

We are waiting for the third membrane, come on, break the stereotypes😮‍💨.

#### WrineX

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.
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

#### WrineX

We are waiting for the third membrane, come on, break the stereotypes😮‍💨.

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

Planar isobaric.

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#### havun

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.
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:

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#### neodymium

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
Unfortunately, you are right. Perhaps the two membranes are still good at very small excursion.

#### WrineX

Planar isobaric.
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 magnets

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#### WrineX

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.
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:
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

#### WrineX

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

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#### WrineX

I made a second panel so i needed to hear how they sound with 2 i made the second wider to see where the resonance lands when using 2 foils unfortuately higher then i wanted. so i might need to change out my damping

1 users

#### neodymium

Grandious soundstage! What does show LRS at same circumstances?

#### pardon

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 so i can add some more magnets View attachment 1299247

Could you explain what's the idea behind covering the magnets with Vliseline?

#### WrineX

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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#### WrineX

Grandious soundstage! What does show LRS at same circumstances?
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

#### solhaga

Great work, Wrinex!

So the trapped air inside the membranes couples the membranes so that the distortion gets lower?

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