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
@jasonbourne52

I have a pair of 8" Kevlar speakers with magnets that are 2/3 the diameter of the speaker, so presumably they will be better at low frequencies than my pair of 8" vintage Wharfdales that only have around a 2" diameter magnet, or is it more complicated than that? I can’t test as they are just the speakers, no cabinet. The reason for the questions is that I have access to a variety of speakers from 8" down, and thought I would do some reading (well a lot) and have a go at building some of them into a cabinet just for the fun of it, then experiment from there.
OP if you have any information on the drivers, that would help YOU build the correct size enclosure.

Second if you don’t have or can’t find the specs on your drivers, there are tools to help figure out certain thing about drivers. Parts Express has some great software and package deals to fix you right up..

Yes magnets wear out. In your lifetime probably not..
Some flake apart, they can loose their mojo, BUT there are some tricks..
There are ways to revitalize the magnets and even change them if you know what your doing.

Sound crazy, but I’m careful around very strong magnets or just a bunch warehoused in tight quarters. Weird vibes so to speak.. LOL

Regards
@oldhvymec3
I’ll have to go with your investigation suggestion as the speakers have nothing on them besides the Wattage and Ohms.

The 8" Kevlars are mental, if you get them stuck together they are one hell of a job to separate.
I believe the stronger the magnet the more efficient the speaker.
Also of interest is a technology called "Field Coil" speakers.
This technology uses the current from your wall outlet to create the magnetic field eliminating the magnet.
From dagogo.com: 
"A field coil speaker uses two coils; the voice coil and a field coil. Instead of a magnet, DC is applied to the field coil creating a magnetic field. This takes the place of the permanent magnet in creating the fixed magnetic field."
I have a pair of 1980s Gale GS302 speakers that have damaged woofers, the tweeters are okay. They are a two way system + a passive radiator. I have stripped them out and they are made of nice thick material with plenty of bracing and doubling up inside.  I may go with them for a first project, I have had thoughts about them before. I had a plan to fit a midrange where the passive radiator was, but inside its own isolated stuffed tube, somewhat like the B&O S45 II. Then make a cut out in the rear and fit a modern passive radiator at the back. Use the 8" Kevlars and a pair of 6.5" for the mid range, then connect them up with a decent quality crossover unit. They would look a little odd as the woofer is mounted in the centre. That means it would go tweeter, woofer, mid range from the top down. I have no idea if swapping the normal woofer mid range layout would have a detrimental effect.