The Secret of Big Speakers
Kii's mission for the THREE was to break the sonic mould of compact speakers. Powerful small speakers with deep bass have been around for a while now but none so far sounded like a big speaker. The THREE is built to fix that.
Basic acoustics tells us that a classic box speaker only directs sound towards the listeners from the midrange up while bass frequencies are radiated all around. The frequency where this change happens depends on the size of the box front (the "baffle"). The smaller the baffle, the higher the frequency at which bass is still radiated all around instead of directed towards the listener.
That in short is why big speakers have so far delivered much more precise timing and detail in the bass and low mids than small speakers: the room gets less chance to interfere. And that is what Kii has now managed to make a compact speaker do.