Compare the resistivity and mass for these materials. For a given resistance you want the lowest mass, at least if you want to use for higher frequencies. Beryllium wins, just ahead of aluminium and magnesium. Copper and silver has double mass or more for the same resistance. Titanium is about 25 times heavier than aluminium. Beryllium is toxic. Magnesium easily go up into flames. Aluminium seems to be the winner in every day use.
Not quite. Halving the thickness of the foil doubles the resistance which all else being equal would halve the efficiency, (-3dB) since it would take twice the voltage to get the same current, but all else is not equal - halving the thickness of the foil also halves the moving mass, which all else being equal would increase output by 6dB. (twice the acceleration and excursion for the same current)
So the net change for halving the foil thickness is a 3dB increase in sensitivity and a 3dB reduction in power handling, (half the thermal mass) leading to the same maximum SPL capability.
Once the foil gets REALLY thin things change though - the air mass load on the foil becomes a large part of the total moving mass, so you just lose sensitivity due to increased resistance and don't gain much increased excursion to compensate. There is a point of diminishing returns as it gets thinner.
On the other hand when the foil is really thin the air mass load is such that the air itself helps to damp any mechanical resonances in the foil - so a thicker foil won't be as well damped as a thin one.
An optimal design balances these factors. Not too thin to throw away maximum SPL capability, but not too thick to throw away damping.
Yep, although quite a bit of the damping comes from the air itself when the foil is really thin...
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If it has a polymer diaphragm it's not a true ribbon, it's a type of plannar driver. Similar, but not the same. A key defining attribute of a true ribbon is that the entire diaphragm mass is directly driven by the magnetic force, as it's all homogenous conductive material.
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I haven't done much calculation, but it seems to me one of the biggest problems, alongside the fact that you're only dealing with a single pass through the magnetic gap, is that the gap is absolutely huge compared to a typical voice coil motor, severely driving down flux density. Since force = IxB, and you need to maximize them both for efficiency, I'd offhandedly say that means every bit of the mass should be conductor. Electrical grade aluminum has half again better mass to conductivity performance of copper, and is therefore the absolute winner of available materials. In other words, forget metallized film. Do everything possible to create maximum gap flux (including minimizing gap width), since no matter what you do electrical Q is going to be too high / back EMF nil. If overall power efficiency is a concern, water cooled electromagnets are out. Several pounds of NdFeBr magnet are probably required. Then you need an amplifer with the usual volt/current delivery reversed, a few volts, and several tens of amps output capacity.
ok.
I had always been confused by the varying types...
I thought planar was a sort of push-pull magnetic system, with a ESL type diaphragm, and wires running in patterns on it. my bad.
right. perhaps a perforated 'straight' ribbon (if it is one) of thicker foil? if you could get the perforation up to a high enough percentage, then you could reduce weight accordingly. As long as the holes are fine enough...
I dont dislike the idea of Aluminium, btw, im just trying to be creative. If it sounds like Kaka ill probably still love it!
Mind you it'd be good if it was half decent
I had always been confused by the varying types...
I thought planar was a sort of push-pull magnetic system, with a ESL type diaphragm, and wires running in patterns on it. my bad.
right. perhaps a perforated 'straight' ribbon (if it is one) of thicker foil? if you could get the perforation up to a high enough percentage, then you could reduce weight accordingly. As long as the holes are fine enough...
I dont dislike the idea of Aluminium, btw, im just trying to be creative. If it sounds like Kaka ill probably still love it!
Mind you it'd be good if it was half decent
Total efficiency-wise yes it would. It might be something to think about one way or another. Some slight improvement may be made there with mechanical and thermal considerations together.
I also wonder if a quasi magnetoplanar approach might be better. With two ribbons and a magnet in the middle (complete with phase plug and outer flares). Possibly this might help increase average gap flux while maintaining area for acceptable lower cutoff point. It would still require the same moose of an outer magnet structure. I'd need software to model it to be sure. But if someone were a ribbon driver purist they would't accept it anyway.. Just some silly ideas..
One problem with that is the polarity of the gap flux would be the same on both sides, so electric series connection requires a very low impedance jumper, somehow.
I also wonder if a quasi magnetoplanar approach might be better. With two ribbons and a magnet in the middle (complete with phase plug and outer flares). Possibly this might help increase average gap flux while maintaining area for acceptable lower cutoff point. It would still require the same moose of an outer magnet structure. I'd need software to model it to be sure. But if someone were a ribbon driver purist they would't accept it anyway.. Just some silly ideas..
One problem with that is the polarity of the gap flux would be the same on both sides, so electric series connection requires a very low impedance jumper, somehow.
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This question of transformerless ribbons pops up every several months. It's very interesting, but getting rid of the transformer and still staying with anything resembling more of a ribbon than magnetoplanar driver will require the special amplifier. In fact, just getting rid of the transformer only requires the amplifer and not any changes to the ribbon driver. For the sake of forward motion, might want to stick to practicality. On the other hand, any attempt to match an actual ribbon driver to an amplifier designed for an 8 ohm load without a transformer is going to wind up fairly sad.
Still, with all that remaining quite obvious for so long, nobody has enough faith in the end result being so far superior to something easier and more common, that they successfuly design the high frequency, good sounding, ultra-low impedance amp. Granted, it seems like it'd be a pain in the butt from every angle.
Still, with all that remaining quite obvious for so long, nobody has enough faith in the end result being so far superior to something easier and more common, that they successfuly design the high frequency, good sounding, ultra-low impedance amp. Granted, it seems like it'd be a pain in the butt from every angle.
Hi,
There is one way of doing it. Imagine a large sheet of aluminium with
thin mylar on the back (and eventually front). Etch it so the "ribbon"
in the gap is multiple parallel conductors, then use the rest of the
sheet with far wider conductors to wire up the parallel conductors
in series. No real reason why it shouldn't be able to be made to
work, or least used to raise the impedance over a single ribbon.
rgds, sreten.
There is one way of doing it. Imagine a large sheet of aluminium with
thin mylar on the back (and eventually front). Etch it so the "ribbon"
in the gap is multiple parallel conductors, then use the rest of the
sheet with far wider conductors to wire up the parallel conductors
in series. No real reason why it shouldn't be able to be made to
work, or least used to raise the impedance over a single ribbon.
rgds, sreten.
Yes bear, i think you are almost right.
Apogee uses Kapton, not Mylar like others do.
Some of their MR/TW ribs are pure ribbons.
Today their *leafs* or *printed ribs* are CNC-Precision-machined, in the beginning handcut, later etched.
And the returns are wires or flat wide aluminiumtraces, installed with different techniques.
Apogee uses Kapton, not Mylar like others do.
Some of their MR/TW ribs are pure ribbons.
Today their *leafs* or *printed ribs* are CNC-Precision-machined, in the beginning handcut, later etched.
And the returns are wires or flat wide aluminiumtraces, installed with different techniques.
well you have to get the returns somwhere. so either the ribbon has multiple connections that are fed back into the bottom of the ribbon, wwith wire or with a loop.
i you can create a ribbon in a loop thats shifts one trace where they are connected ur done.
kindo of a nice idea , but hard dto make
i you can create a ribbon in a loop thats shifts one trace where they are connected ur done.
kindo of a nice idea , but hard dto make
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