Sound Absorption Behind and Between the Speakers?

@rego and others,

Rego pointed out that:

the reason for treatment on the front wall is to control first reflections and then help on the axial direction.

If the time it takes for the first reflection behind the speakers is longer than the time it takes the sound from front of the speakers to my ears, why would I need to treat them?

Smearing is the term of reference that I see used ... the reflections still have energy ... in a room that is very 'bright' this energy is at higher levels longer.
This is about reinforcement and interference interactions.
The reflections do not stop at the first reflection but go on to two, three and lot more.
These are all ripples at many frequencies in the pond that is the listening space ...

Though the drivers appear as though only front firing, the sound produced is somewhat omnidirectional, especially as frequencies decrease. Typically  speakers are placed so that the wall behind them is closest. The ear/brain mechanism can discriminate between direct and reflected sounds so long as there is about 5 ms between them. If the sound bouncing off the wall behind the speakers (typically the closest wall) is too close, then there isn’t enough time between the direct vs. reflected sound and the sound converges to smear the perceived direct sound. Hence, sound treatment behind and between the speakers.

@rego and @unsound 
That helps. I moved my speakers far enough off the front wall so that there'd be enough of a delay and I wouldn't get the reflected sound *before* the direct sound.

Still, Rego's point is valid. The whole room is still full of energy/information and that can get into the mix, even if it's not interfering, initially, with the direct sound.

That's how I understand what you're saying, at least.

^ For most forward facing driver speakers 3>' from the nearest wall will usually be quite helpful for most users towards ameliorating the time smear of direct vs reflected sound perception.