The way speakers give you dimension is as follows:
The speakers should be about 8' apart
When music plays, 1 channel is out of phase with the other.
When the speaker plays on one channel it will reach one ear slightly before it hits the other. For example your left ear hears the left ear first, then your right ear. Part of the indication for distance in a recording is based on one ear hearing it first(of course if it is straight forward both ears hear it at the same time, indicating it is front of you) hearing it first, and the slight delay before being sensed by the other ear, as the wave also picks up contours of your face as it passes to the other ear. These contours of your face and the shape of your outer ear helps determine the direction of the sound source. The out of phase that speakers do is to blend each channel to each other, so it can give a sense of space. This helps give you left to right separation, and the mix from each channel will help separate how far apart each sound is left to right. The front to back separation is determined by the volume of each separate instrument. So a mid left instrument that they want to be a little behind the group will have the instruments volume a little lower in each channel, with more of the instrument mixed to the left and less to the right. This combo would make it sound like the instrument is on your mid left to center, a little further back than other instruments.
Hope this clear description for you.