You can't just take open back headphones and close them up, it will sound terrible. And conversely you can't open up a pair of closed headphones without the sam

You can't just take open back headphones and close them up, it will sound terrible. And conversely you can't open up a pair of closed headphones without the same problem. If you could make a headphone that can do both and sound acceptable, it would probably much more expensive than just buying a two pairs, one open and one closed.