There are 2 speakers up next to the head rest of the chair and there are 2 more down by your legs. If these speakers make no sound, then it is because they don’t. For some very unusual reason they decided to add what look like speakers to the bottom, but they are actually just place holders. This is incredibly pointless, but this is how the chair has been designed.
There is a 4.1 model of the X-Rocker Pro that does have speakers present at the bottom area, but this chair seems to be quite difficult to find. There is a good chance, that if you are unsure of the model you have its the 2.1 model and these speakers do not exist and cant be wired up to create sound.