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The diaphragms of all cone drivers are driven at one end and only held in place by thin flexible membranes.
The Planot plan is to fix the diaphragm and the voice coils “exactly” in place at the pivot points. With the Planot only linear movement is possible!
While driving a cone at its apex (which seemed a good idea at small excursions) the cone is increasing restrained. The further the cone travels the more the surround and spider compress and deform the cone.
If you make the surround and spider system less stiff then the cone can not be supported and centered in the magnetic gap. If you make the cone stiffer and heavier then you will need a stiffer surround and spider system which will be less compliant and require more amplifier power.
In a cone speaker the surround spider system is constantly being asked to perform opposing functions. One function resists the other.
The Planot plan is to separate those functions into their own individual systems and optimize each. Separate and not equal because each is different.
Rigid and fixed...
The Planot driver is a perfect compromise of minimal proportions. At the high end of the frequency range, for the first time, is a true rigid tweeter diaphragm. This is no "delicate silk dome" or aluminum dome held in place by a soft and elastic surround. The diaphragm is held rigidly in place by the bearings that maintain the diaphragm and the voice coil exactly where they should be and will always be regardless of the music being played.
Never before has the full frequency range been held to such tight tolerances. There is no wobbly rubber "surrounds" or cloth "spiders" attempting to hold the diaphragm; instead there is the steely grip of the Planot.
Other diaphragm technologies can not approach the linear movement of the Planot diaphragm. If you look at plots of the “response” of speaker surrounds you will see that their compliance is not uniform. Also it is not uniform when comparing both the out and in extremes of its’ travel.
The magnetic homing of a Planot driver applies minimal damping during the limited travel at high frequencies but damping increases linearly at lower frequencies when there is a corresponding longer travel of the diaphragm.
Other technologies brag that their "cones" flex. They say all diaphragms flex, but they "utilize" the flexing to control dispersion at the high frequencies! If your design has an inherent weakness, you can attempt to capitalize on the weakness but you can't fool everyone all of the time.
The Planot driver does not flex as all traditional drivers do. The forces acting on the diaphragm differ in a critical way. The forces are torsional, as opposed to the tensile forces acting on other diaphragms. The main inertial forces in the Planot speaker are dissipated down its length and don't cause the diaphragm to flex as a cone does.
In the Planot design the driving force is applied to the end of the diaphragm. The whole diaphragm is turned as one piece and not pumped back and forth in a cone/dome speaker causing the driver to flex.