Sia's version of her hit song "Chandelier" is pretty good, but it doesn't touch this a capella version, at least in my humble opinion.
A group called Twisted Measure recently hit it out of the park with a cover of the song.
The video is a little dark, and it's shot in black and white. But, it doesn't really matter.
You don't watch an a capella video for the visuals. You just need to hear the excellent singing, and I assure you there is nothing wrong with the sound quality.
Check out Twisted Measure's rendition of "Chandelier" above.