Broken wire on a coil, any way to fix it ?

[dadafu]

Yes continuity is good

possibly overdriven (900W RMS Amp, subwoofer 450W RMS and 900W Max) but the coil is dark when new too, as you can see on the joined pic, so I'm not sure about it

Tried to add some tin on the original solder, but the new tin doesn't go in the old one

 

[Galu]

Tried to add some tin on the original solder, but the new tin doesn't go in the old one

Did you do as I suggested?
What do you mean by 'tin'? Use a tin and lead flux cored solder.
FE3T mentioned the possibility of the voice coil being aluminium and aluminium/copper joints are notoriously difficult to solder.
Do you know if the voice coil is copper or aluminium?

 

[nigelwright7557]

Before trying the speaker again try to find out why it blew in the first place or you could end up blowing it again !
Maybe amp is putting out DC ?

 

[Galu]

For interested parties, soldering aluminium is discussed in this diyAudio thread:

Soldering Aluminium