I can't do something like
/playsound random.explode @a ~ ~ ~ it will just play the sound to everyone, no matter how far away they are.
But when I use a command like
/playsound random.explode @a 10 25 -4 it will play the sound coming from the coords specified.
Please note: I do not know how many versions of Minecraft this concerns, but I discovered it in 14w11b. Also, I do not know if this is a bug or if it is just not implemented. If it is not a bug, I would appreciate it if this was added to the game.