i decided to split this off from the main thread:
http://www.diyaudio.com/forums/showthread.php?t=151474
to simply focus on how it compares to isodynamic because there is a direct relationship.
an isodynamic driver is essentially a metal plate ( a perforated steel mesh in case of many drivers such as magnepan ) through which magnets push flux. the flux has to return through the air and passes the conductors on the way.
we typically think of the flux as originating in the magnets and the steel closing the loop.
i want you to think of a magnepan panel and think of the steel mesh itself as the origin of the flux and magnets as merely exit points for it. now eliminate the magnets. now replace the steel mesh with neodymium mesh.
so far you still have the same exact speaker functionality as magnepan only instead of separate magnets and steel mesh you simply have a magnet mesh. the flux still takes the exact same path but now there is no steel and the magnets are oriented parallel to the ribbon surface, not perpendicular to it.
and now the million dollar question - is there any need for the magnetic field to constantly switch polarity ? the answer is NO. there WAS a reason when the mesh was steel because the field is looking for a shortest path and will short itself out in steel, but in neodymium it won't. in neodymium we can send the flux all the way through the panel in one direction.
you can see then that PLUR is essentially like magnepan except that the field doesn't switch polarity ... ever. so instead of a plastic diaphragm with a conductor pattern etched onto it you can have a uniform piece of aluminum foil.
this is unmistakably an improvement. but it is not THE improvement. the real improvement also comes from the fact that the polarity doesn't switch. when polarity switches as in magnepan it has a way of canceling itself out at a longer distance so field is strong immediately next to the panel but tends to zero rather quickly as you move away from the panel as pluses and minuses cancel.
there is no such cancellation when the polarity is consistent across the entire panel. in fact the neighboring regions of the panel ADD rather than subtract to the field at the distance ! the wider the panel the further away it will project the field.
so basically you can always take a PLUR, slice it up, reverse the polarity on half of the slices and you will have yourself a magnepan. in the process you will have taken a beautiful uniform field that projected perhaps a foot away from the panel and cancelled out 99% of it, and that nonuniformly !
nonuniformly in two directions mind you ! both along the surface of the ribbon and along the excursion range of it.
both magnepan type driver and PLUR can be made single ended or push pull, that is not the difference.
instead the point is that PLUR and magnepan type driver are essentially the same except that one is simple and perfect projecting a huge uniform field and another one goes out of its way to destroy itself by creating an intricate 3-dimensional pattern of cancellations which serve no purpose other than destroying sensitivity and creating distortion.
PLUR is essentially optimal geometry. magnepan ( BG Neo uses the same principle is essentially ANTI-OPTIMAL.
http://www.diyaudio.com/forums/showthread.php?t=151474
to simply focus on how it compares to isodynamic because there is a direct relationship.
an isodynamic driver is essentially a metal plate ( a perforated steel mesh in case of many drivers such as magnepan ) through which magnets push flux. the flux has to return through the air and passes the conductors on the way.
we typically think of the flux as originating in the magnets and the steel closing the loop.
i want you to think of a magnepan panel and think of the steel mesh itself as the origin of the flux and magnets as merely exit points for it. now eliminate the magnets. now replace the steel mesh with neodymium mesh.
so far you still have the same exact speaker functionality as magnepan only instead of separate magnets and steel mesh you simply have a magnet mesh. the flux still takes the exact same path but now there is no steel and the magnets are oriented parallel to the ribbon surface, not perpendicular to it.
and now the million dollar question - is there any need for the magnetic field to constantly switch polarity ? the answer is NO. there WAS a reason when the mesh was steel because the field is looking for a shortest path and will short itself out in steel, but in neodymium it won't. in neodymium we can send the flux all the way through the panel in one direction.
you can see then that PLUR is essentially like magnepan except that the field doesn't switch polarity ... ever. so instead of a plastic diaphragm with a conductor pattern etched onto it you can have a uniform piece of aluminum foil.
this is unmistakably an improvement. but it is not THE improvement. the real improvement also comes from the fact that the polarity doesn't switch. when polarity switches as in magnepan it has a way of canceling itself out at a longer distance so field is strong immediately next to the panel but tends to zero rather quickly as you move away from the panel as pluses and minuses cancel.
there is no such cancellation when the polarity is consistent across the entire panel. in fact the neighboring regions of the panel ADD rather than subtract to the field at the distance ! the wider the panel the further away it will project the field.
so basically you can always take a PLUR, slice it up, reverse the polarity on half of the slices and you will have yourself a magnepan. in the process you will have taken a beautiful uniform field that projected perhaps a foot away from the panel and cancelled out 99% of it, and that nonuniformly !
nonuniformly in two directions mind you ! both along the surface of the ribbon and along the excursion range of it.
both magnepan type driver and PLUR can be made single ended or push pull, that is not the difference.
instead the point is that PLUR and magnepan type driver are essentially the same except that one is simple and perfect projecting a huge uniform field and another one goes out of its way to destroy itself by creating an intricate 3-dimensional pattern of cancellations which serve no purpose other than destroying sensitivity and creating distortion.
PLUR is essentially optimal geometry. magnepan ( BG Neo uses the same principle is essentially ANTI-OPTIMAL.
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ok much of what i have written in this thread turns out to be wrong.
in actuality my PLUR technology suffers from more field cancellation up-close than does isodynamic planar.
out at a distance indeed the behavior is as i previously described, unfortunately what we're really intersted is the "up close" behavior.
the nature of cancellation is hard to explain ( except that it is the opposite of everything i have been saying in this thread ) however the bottom line is:
PLUR should be used for the same ribbon width as regular ribbon motor meaning about 1/3" to 2" wide. NOT for wide panels as i previously said.
for narrow ribbons it offers similar field strength to regular ribbon motor.
for wide panel field strength will tend to ZERO.
more details here:
http://www.diyaudio.com/forums/planars-exotics/155042-i-wrong.html
in actuality my PLUR technology suffers from more field cancellation up-close than does isodynamic planar.
out at a distance indeed the behavior is as i previously described, unfortunately what we're really intersted is the "up close" behavior.
the nature of cancellation is hard to explain ( except that it is the opposite of everything i have been saying in this thread ) however the bottom line is:
PLUR should be used for the same ribbon width as regular ribbon motor meaning about 1/3" to 2" wide. NOT for wide panels as i previously said.
for narrow ribbons it offers similar field strength to regular ribbon motor.
for wide panel field strength will tend to ZERO.
more details here:
http://www.diyaudio.com/forums/planars-exotics/155042-i-wrong.html
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