Dual membrane planar magnetic (both active driven)

The average drum used in a brass or symphony orchestra has a main membrane tuning range (natural leather or plastic) in the region of 60-80Hz.
In our membranes, depending on the size, the main resonance is much lower, I think by several octaves.
That is, this range is mainly sub-bass.
So the stretched film only visually resembles a drum, but nothing more.
uhm yes. im not sure what your point is (i think we do not understand each other correctly). when i say drum. i dont want to make it sound like a drum... the working is the same as a drum.. with a main resonance etc. thats the way it is if you strech any membrane suspended you get a drum. sure a drum has a housing etc. but same rules apply. not much output under main resonance.. and huge peak at resonance. now the task at hand here is damp main resonance and or get main resonance as low as possible in this setup. to much damping sounds poo and hurts other frequencies as well. to little and you still have a peak.
if the resonance is to high in frequency the peak is even more anoying. and well you cant go much lower then that. since the dual foil halves the damping from the air it normally gets.. a panel must be wider then usual, or less streched.. less stretch gives other distortion problems, it moves less nicer together with the other foil. my theory, is larger foil and firm stretch.. downside is it gets big. noone likes wide... and making it biger vertical does not do as much, since that direction already is lower in resonance then the main combined resonance of vertical and horizontal. so the only size that dictates the resonance is in this case the width :(
i could try different tensions horizontal and vertical, that might fix some problems of less tension overal.. but i doubt it
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i tried some ribbon kind of foils... yes you can get resonance down, but it will flap all over the place.. so next up will be this design. idea would be restricting movement in the middle while giving the upper and bottom end a bit more movement by making the foil wider and more open area compared to the middle... who knows... pure gamble..

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well this one made a complete mess :) so that does not work haha, i think regular or maybe even more round or oval... might even work better
if i would make it a circle... resonance will get even a bigger problem though :)
If the driver is completely disconnected from the amplifier and you hit your membrane with your finger, what will be the resonance measured by the microphone?
This will be the effect of the drum and its main resonance, and it will also be clear what means to combat these resonances.
Can you record this drummer on a microphone from your subs, it’s not the amount of low frequencies that interests you, but their attack, especially in the bass drum.https://www.youtube.com/watch?v=ues2RBpXQoI&list=LL&index=16
The theme of the drums haunts me:ROFLMAO:.
I had an email with Rob Mackinlay from ERaudio about the subject of introducing central excursion corrective gradients into a planar membrane's drive. At first sight, it appealed to me as to be a very insteresting approach, potentially even rising the overall max. SPL capacity of a planar. Because you could drive it harder until the central parts slam onto the stator/magnetic array. However, one of the conslusions I made after my exchange with Rob is that you go may run into more trouble than you may solve with any driving gradient. Homogenous drive still seems overall way superior.

Several examples of non-homogenous drive methods have already been enumerated here in this tread, such as beating a drum by a stick, adding central weight to the membrane, leaving a central drive hole in the stators/magtnetic array, and the like.

Surprizingly, the most evident and widespread example of uneven drive has not been mentionned yet: The one in standard magnetodynamic cone/dome drivers. A dome is not driven centrally. And a cone is not driver in periphery. So there is a clear drive gradient along the membranes in these examples. All these unevenly driven membranes will break into submodes, as shown in the youtoube videos, and as known from cone and dome breakup in magnetodynamic drivers. Therefore, with a drive gradient, you will basically trade in one of the main benefits of even membrane drive over it's whole aera.

In terms of resonant sub-modes, any drive gradient will to some extent reduce the benefit of magnetostats or electrostats elegant homogenous drive to the potential mess you have with cone breakup issues in traditional cone or dome speakers.

Don't. It would be a pity to treat planars like this ...
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Several examples of non-homogenous drive methods have already been enumerated here in this tread, such as beating a drum by a stick, adding central weight to the membrane, leaving a central drive hole in the stators/magtnetic array, and the like.
well so far none of them gave a better result then just drive them as is , i tried removing some magnets in the middle... makes it worse, i tried damping in the middle, makes it worse, i still want to try tension ed and corrugated at the same time.. hard to do but i give it a shot in the near future. i tried corrugated not tensioned.... no change 7 Hz resonance. and all kinds of other resonances near the edges. it is also is leaky making the edges flap around even more. :( (to some extend it lowered 3th harmonics, but all the gain from res is gone if its 7 Hz haha, witch is also a shame, we need some gain from res)
my best best so far would be ribbon like corrugated membrane with slight tension sideways... then you end up with sort of a apogee kind of foil.. (maybe for a good reason :) i bet they tried some things as well) there slanted style (so not rectangular) might not work as well here, because the air from one foil drivers the other... but i did not try yet, so maybe it does. spreading the resonance out
That's impressive. I'd like to hear the corrugated, low res. freq. version. I agree, that can be buzzy because there are undriven and untensioned surfaces, but the tonal balance can be informative.

25 yrs ago I've built two 70x100cm bass panels with 18Hz res.freq. These were a little bit bass deficient (!), but the bass at nearfield was O.K. Sometimes I've experienced unbeliveable deep voices. After a few months I've tensioned the membrane. The bass became very punchy - but colored and nasty too... The power handling capability was huge (and the sensitivity still sh.t).
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haha, yeah mine are very very very inefficient to :) 78-79 dB or something..... at least down low
i think they could work nice in sort of a planar sub. like the one magnepan makes. except this would be able to go much lower maybe even louder with less distortion. at the cost of enormous power i guess haha
why would you >? normal aluminium enameled would be good enough. you can get small rolls here wires.co.uk
to solder it, either use the cheap flux found on ebay. or an alu solder. expensive... but works rather nice. my new go to. bit dull solder joint but perfect to wett the solder joint then use regular solder. and less smoke and stinky then using the flux (witch is some sort of acid i think, if you dont clean it after... it might corode the aluminium)
Thank you! I thought, the non-corrosive soldering might be beneficial. The newer chinese UTP cables contain CCAW, but isn't enameled. 40 yrs ago I found in soviet color TV's power supply trafo a lot of alu wire, but it was impregnated. (This TV was the Color Star, the famous and beautiful 6P45S was its horizontal sweep tube. Unfortunately, these TVs often began to burn out with huge flames - not only at the day of Sylvester)