how can i make my own earphones that are high quality?

By its nature, this is an incomplete description of what is needed,

but it should be sufficiently informative:

You will need to study the properties of rare-earth magnets,

then find and acquire some that will suit your purposes.

Then you will have to machine the magnet structures (the parts

of the magnetic assembly that are not the magnets themselves).

You will need some method of molding plastic parts

or carving very small pieces of wood.

The speaker diaphragms need to be made of microscopically

thin plastic that will be rigid at all of the audio frequencies

you want to reproduce. Got any of that handy?

To make the voice coils, you will need to hand-wind the hundreds

of turns of wire that is too small to see without a magnifier

(I would use an Optivisor with a # 5 or # 7 lens).

Still seems like a fun idea? Have at it.