There are lots of great ideas here. Some of my favorites I've seen posted so far:
"Elementals"
from pmbuko I like simply 'Element' Series. Combined with the 4 elements, these speakers could certainly be considered the 5th Element
"Open Air"
from whatfurrerAnother great one. I do like the idea of shortening it to either 'Open Series' or 'Aire Series' (spelled how lhulls was suggesting)
"Serenity"
from tmoyakI like it.
Now for some of my own. Once I started thinking, the ideas just started flowing...
Nirvana Series
Utopia Series
Expression Series
Release Series
Escape Series
Perfection Series
Freedom Series
Axiom
Without-Bounds or
"Boundless Axioms"Axiom Anywhere Series
Galaxy Series
Backyard Series
Sky Series
Celestial Series
Axiom SoundWaves