No. On either count.
Car seat-belts are more than "nice to haves".
I would refer you to comments in the post by
@S-Man above, which is/are precisely what I was alluding to.
Speaker protection boards, complete, ready-built, are freely available and generally need no more than some screw terminals tightening onto the appropriate stripped wires. They are around 10 x 8 x 3cm high. All the ones that I have seen have been stereo, so in mono-blocks, just half the board is used. Input voltage, to actually power the protection circuit, is generally a huge range, AC or DC.