Eldartford...from the Apogee forum regarding the Apogee magnet layout:
"Apogee bass panels are single-ended...(Magnets on one side only) As the panel moves backward toward the magnets,
the magnetic field gets stronger. As the panel moves away from the magnets - the magnetic field gets weaker. Therefore, there is an asymmetry to the reproduction of the compression waves vs. the rarefactions.
If the panels had TWO sets of magnets; one in front and one in back - then there would be
no asymmetry. As the panel moved away from the back magnets - it would be moving closer to the front magnets and visa-versa. There would be no asymmetry in the production of the compression waves vs. the rarefactions."
"The classic or "true" ribbon like the Apogee MRTs is "double-ended". There are magnets
on both sides - left and right - of the MRT and as the ribbon moves forward and backwards
there is no asymmetry in the magnetic field that the ribbon experiences.
In essence, the MRT ribbons look / work the same if you turned them around front to back.
Thats not the case with a single-ended driver like the Apogee woofers. The compression /
rarefaction asymmetry changes if you flip them around"
"the trapezoidal shape is for control of resonances or vibration "modes"
Because of the shape - the width of the ribbon is not constant with height.
Therefore, the resonant frequency is not constant with height. So resonances are "spread out".
Dave
