I gave my old 12" sub to a friend when I upgraded my car stereo
its a alpine vr 12 thats about 10+ years old.    in my car it lived in a ported bass tube
bought years ago,   and it sounded ok to me -  but distorted a little at volume

I showed my buddy this site - and he decided he wanted to put the 12" in a db-12
just to see how it did ( he liked my db10 )

box was built to specs - slider piece was amazingly hard to move up and down in the box.
12" sub was put in and wired up to his amp
320w rms ( 100rms 200wmax labeled sub ) gain turned way down

testing out the new box design in his 2003ish ford explorer
box port facing the rear hatch - box all the way up against the rear seat

it sounds simply amazing.
its loud - clear - and loud -  and it shakes the seats in his truck.
when you get in and crank up the tunes - you would swear there is 3 big subs back there
making all that sound.
its realley awesome.