Magnetic field coil ferrous material for loudspeaker

[berkeman]

I realize that there are many questions to answer and therefore I don't expect to get all the answers but I would like to get the answer to just one question, I don't think I'm asking too much.
what happens if I put two metals with different magnetic saturation but different or equal magnetic permeability in contact?

the metal with higher magnetic saturation is used to generate the magnetic field through the copper coil while the second metal with lower magnetic saturation is used to channel and close the flux of the magnetic field in a toroidal ring so as not to disperse it in the surrounding space.

I would like to know how the characteristics of the magnetic field that passes through two different metals change.

Can you use the "Attach files" link below the Edit window to upload a diagram of this arrangement? How can you have a voicecoil on a toroid? Thanks.

 

[arivel]

if you say this it means that I used the wrong word.
refer to the image of the number 24 .
there it is shown in section but you have to imagine it in three dimensions