How far can be placed - nearfileds

[Niccie]

Hi there, i'm here again since well... long time no see.
I ended up with a question about positioning nearfields.
THe question is: How far is far enough for nearfields to work without losing sound quality, I know about the Angle retionship between the speakers and the listening spot, but i wonder how big can i make that triangle figure to work in terms of distance. Or maybe it depends on the size of the speakers?
Mine are 5" woofers-mid and 1" driver Highs. And it seems like bigger distance gives a little loss in bass freqs, or maybe is a psicological feeling?.

I don't know if i made myself clear, but you know my english is very poor, so i tried my best.

I'll stay around for answers, THanks in advance about any comments on this.

Regards.