If I have to pick the most important factor in sounding live it's linearity. Double the input then the output should double. Triple and etc. And it's true in the entire system, not just speakers. I recall Bud Fried's speakers were linear phase and roughly time aligned but it was their linear changes in sound pressure level that made the sound real. And There are non linear phase and non time aligned speakers that sound real like ATCs and again it's linearity that makes it happen.
