I have 2 Alpine ‘S’ types in a dual non ported box, someone has suggested to reverse mount them, Does anyone here no what the + side would be to reverse mounting these subs. When reverse mounting do you also change the wires from ++ -- to +- -+.. if you no what I mean

Yes you do change the polarity on the subs like you mentioned.

Not really any advantage except for the look. Will also mean the subs are workin in a slightly larger enclosure. Not that the sound is going to change a lot at all.

So basically it's more of a show thing. and if you want to take up more space go right ahead.

If your current box is of adequte size don't bother. If its to small then for sure reverse mount and swap your polarity, this will give you just a bit more space

What if you reverse mount one, and "correctly" mount one?

it will effwectively make one sub dal

same thing again. Just creating a little bit more space for the sub to work in. I wouldn't advise doing this when subs share the same airspace.

try taking your box with the subs mounted propperly and turn the whole box arround. see if that sounds any better.