Speaker magnets


Three questions:
1) The coil in a speaker when fed with current from the amplifier will produce its own magnetic field, presumably 4 layer coils more so. Over time does this ever have any effect on the characteristics of the speaker magnet?
2) Modern speakers have massive magnets compared with most vintage speakers. What advantage do they give a modern speaker over a vintage speaker?
3) Does the magnet in a speaker deteriorate to any noticeable amount just due to age?
chris_w_uk
While most big woofers have large motor structures, it’s not the sole determination on quality and output. The 8” woofers used in the KEF 104/2 look like anything but impressive, yet their low end is output and power handling is remarkable. It’s the same with Hafler 300 speakers with two 6.5” woofers. Out of the cabinet, their not impressive yet they manage to pump out a tremendous low end quality and volume. 
Did you folks know that a big sub magnet, juduciously placed,  will trigger a hotel safe to unlock it. 
Passive radiator rings CNC cut, drilled, painted and passive radiators fitted. URL as above.
Anisotropic Alnico magnets are theoretically the best magnets for subwoofers but they are more expensive so Ferrite magnets are much more common. Ferrite magnets work well and are harder to demagnetize they just have to be larger.