The magnets are held on to the tweeter hole in th MDF plate by their
own magnetic force, and the fact that you have long strips of
metal plates covering the sides of the hole (don't you....???!!),
thus the north pole of the magnets are on one side and the other side holds
the south pole magnets. This is done so the top row of magnets on the
woofer section of that speaker must have the same polarity as the row
of magnets in the tweeter section closest to the woofer section (sounds
wierd but it's simple, don't worry on what exactly is the N and the S
polarity, just assume that one is the N and the other is the S and work
consequently out of that assumption. When this is done, you are thus
sure that the speakers are working in fase.This diagramme shows the returning conductors made out of the aluminium material , I chose to use wires and make the tweeter conductors not as wide as the original project. You experiment and find out.