yes that is my biggest concern in general !! since its like a drum. it will never move like a flat stiff plate ! we already knew this before we tried it 
but besides that there are tiny things like more damping at some spots etc, that will work against the idea. (things like open area becomes a real thing, since some parts might actually be damped more because it has less open area, or tension is different etc) so this panel has random holes i did not line up magnets to achieve best open area, or consistent open area, and that might come back to bite me when using MFB on it
my idea today was using a bigger area to reflect light to achieve more of an overall response (having a measurement of a bigger surface area), and already worked out better then 2 days before. i could compensate now far more then we could at our first try
but besides that there are tiny things like more damping at some spots etc, that will work against the idea. (things like open area becomes a real thing, since some parts might actually be damped more because it has less open area, or tension is different etc) so this panel has random holes i did not line up magnets to achieve best open area, or consistent open area, and that might come back to bite me when using MFB on itmy idea today was using a bigger area to reflect light to achieve more of an overall response (having a measurement of a bigger surface area), and already worked out better then 2 days before. i could compensate now far more then we could at our first try
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Joppe i was thinking if you could use the al foil as a mirror and put the reflective tape close to the light source? That way you would get the double distance and higher resolution. Also you get to fixate the sensor very tight to the speaker with a cross member. Do you know the phase shift of the sensor? What is the bandwith? And what is the dynamic range? When it comes to MFB it make sense for subwoofers but for your planars? Do they really have that much distortion?
hmm that mirror thing might be interesting ! well do planars have distortion. yes ! and no less if not even more then a regular driver. in the low end espoecially when using single ended magnets (magnets on the back only) but to me there are only 2 things that might be interesting lower from a panel that is actually not wide enough (so has to high resonance) and damping the main resonance. without felt.. that was not possible in this design but im sure it can do better with more controll by using different magnets or more coil
espoecially when using single ended magnets (magnets on the back only) but to me there are only 2 things that might be interesting lower from a panel that is actually not wide enough (so has to high resonance) and damping the main resonance. without felt.. that was not possible in this design but im sure it can do better with more controll by using different magnets or more coil
Not really, there is only one point of application in the drum, the point at which the beater strikes the diaphragm.
In your case it is a foil glued on the membrane and activated by magnets, yes - there are non-activated areas of the foil, maybe even 50% or less.
But in electrostatics the whole foil is activated, over the whole area, so to call it a "drum".....
It may have its own resonance, but it is damped not only by the electric signal, but also by the mass of the applied air, and we remember that the mass of air in case of large area is almost always greater than the mass of the membrane itself.
So in this regard, a conventional cone speaker driven at the center by a coil and magnet is much more of a drum.
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The problem of reproducing low frequencies for film emitters is that the driver himself must have a decent mass of the moving part, and this mass a priori is not present in the film emitter. Partly for this reason, I took the path of creating a whole package of membranes in order to increase the mass on one side and add up motor forces on the other handhmm that mirror thing might be interesting ! well do planars have distortion. yes ! and no less if not even more then a regular driver. in the low end
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Sorry, this is a serious misinterpretation. The air mass can't make damping alone. Please, realize this already! The air mass only decreases the resonance frequency. The air's acoustical resistance makes damping, lowered the total Q factor. The air mass alone is only inductive component of load impedance.
neodymium
It all depends on the total area of the emitter; if the area is small, it will be as you write.But in this case we are talking about a bass driver where a large area is implied.
Further, the thickness and mass of the membrane, a thick membrane with aluminum coils glued to it, will certainly have a greater inertial mass, which means the air damping will be much, much less.
In this case, the strength of the membrane-controlled motor will be of great importance; this is also part of the damping, and not just the air mass.
Ok, but I haven't seen your evidence to the contrary.
Let's consider a regular subwoofer on a cone diffuser; they may have a different (relatively) mass of the moving system, which includes: the mass of the coil, centering washer, supply wires, diffuser and rubber corrugation.
All together this can reach...let it be a few grams, maybe 10, maybe 20.
We put this speaker in a tightly closed box and fasten it with bolts.
What do you think dampens the mass of the moving system, except for the electrical part, from the point of view of the developers of this subwoofer, who are well aware of the “basics of physics”, is air involved there?
Let's consider a regular subwoofer on a cone diffuser; they may have a different (relatively) mass of the moving system, which includes: the mass of the coil, centering washer, supply wires, diffuser and rubber corrugation.
All together this can reach...let it be a few grams, maybe 10, maybe 20.
We put this speaker in a tightly closed box and fasten it with bolts.
What do you think dampens the mass of the moving system, except for the electrical part, from the point of view of the developers of this subwoofer, who are well aware of the “basics of physics”, is air involved there?
Maybe you can look at the output of the feedback circuit to see 'what it does', rather then try to separate it from the input and output signals.well but how do people measure that ? since its doing things it could not before to begin with.
biggest problem i think is not having enough controll over the foil
Jan
What is your statement?
Terminology! The mass can't dampenable, only the mechanical resonance. If your terminology are inaccurate, can kill the conversation.
However, there are non electrical damping elements: the suspension's viscous (lossy) character, and acoustical load's resistive component (air load), on front and behind membrane. These factors are weaker, than electrical damping (at dynamic woofer in closed box, of course).
neodymium
But you yourself started talking about the “fundamentals of physics”, the terminology here is almost secondary, you need to understand the basics.It turns out that you admitted that the acoustic load works as a damper, right?
Now let's figure out the mass of the moving system, its area and, accordingly, the mass of air attached to this area.
In the case of a regular sub and a closed box, we have a small volume of air in a tightly closed space, which means that the diffuser cannot move this air into a more open space and, as a result, this closed volume of air produces “pressure” on the moving system, thus damping it (by air).
In the case of a light, I would even say extremely light, moving system and its very large area, the matter of damping is simplified; the mass of the moving system is lighter than the mass of the connected air.
I just told all this to my wife, she said that she understands what is happening with damping, maybe she was playing along with me on purpose
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You have a good and nice wife!I just told all this to my wife, she said that she understands what is happening with damping, maybe she was playing along with me on purpose
Of course, that's right with small refinement: the acoustic load's ohmic component works as a damper.
You wrote as damping by air, but isn't damper, only spring. Damper function can be only small proportion, if the air compression and expansion isn't fully adiabatic.
Both of states are true, but they aren't causal connection. The larger area (at lower frequencies) increases the moving mass of air / surface area AND increases the radiation impedance. The second thing are the key for damping. Notice! The membrane movement reduction isn't same as damping!
well even if its driven over the entire area the tension on the foil wont allow it to move as far over its complete surface area.. like a drum. on the sides and top and bottom excursion will never hit the stator. it will in the middle.
The fact of the matter is that in the case of an electrostatic device, in which the motor is very weak, a large mass of air attached to a large area of the membrane acts as a pure damper, but not a “spring” at all.But if you attach a “spring” to the electrostatic device, it will stop working altogether
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