That tiny little box, downfiring no less is gonna limit output especally on a 500W amp. You can even put on a hard top and it'll probably just keep underwhelming you. Even adding power too probably wont be enough imo.
Trying to save space on lower powered bass almost never works out well.
If you end up redoing it even a small ported will make better use of your power. Personally I'm not a sealed box fan and small sealed is even worse. Add no cabin to gain & its gotta be maddening to have spent what you did on the sub and have it perform how it is currently.
If you do decde to rebuild the box how much space is going to be too much?
I ask because I've done Demon 12 boxes as small as 13t x21w x 16.5"d. Even a small ported will be a big improvement on your power I think.
Trying to save space on lower powered bass almost never works out well.
If you end up redoing it even a small ported will make better use of your power. Personally I'm not a sealed box fan and small sealed is even worse. Add no cabin to gain & its gotta be maddening to have spent what you did on the sub and have it perform how it is currently.
If you do decde to rebuild the box how much space is going to be too much?
I ask because I've done Demon 12 boxes as small as 13t x21w x 16.5"d. Even a small ported will be a big improvement on your power I think.