I now have the Kii Three incl. BXT in my listening for more than a week.
The BXT module rounds up the sub-bass in a nearly perfect manner. It is the best bass I heard in my room and maybe everywhere. Even w/o room correction it is amazingly crisp. No booming, it blends in smoothly.
The Kii Three + BXT is one of the few loudspeakers which can give true realism to the full range of drums, kick drums to toms. The Genelec 7360 can't touch them. Electronic music is equally impressive.
If you like sub-bass, you can empty your wallet and be happy. If you can live without that pressure in the lowest end, the BXT won't change the signature of the Kii Three IMHO.
Nevertheless, I am probably going to return the Kii.
Yes, the frequency response is so fine, no coloration.
But in my room (connected by USB) I couldn't make them sing, they don't project a good enough stereo image, no stage.
Music, where it came out well:
- Kleiber w Wiener Phil. (Grammophon), Beethoven 5th: The Genelec make it a feast to listen to, the Kii is quite flat and image is smeared across.
- Tom Waits, Rain Dogs, Traubert's Blues: Mr Waits is somewhere, not in front of me; the violins well played but unlocatable. The song loses its intimacy.
- Belafonte at Carnegie. Besides the hiss of the recording is more than I would like, on other systems I hear where in the audience people were coughing or when Harry walks across the stage. Not with the Kii.
It is a great speaker, the cardoid bass really makes a difference. But listening to music is about creating emotions and "being there" is important to my listening experience.
It is one of these rare cases, where Harman might have been wrong: a single Kii sounds excellent, but the stereo pair is mediocre.