That's a strange qualification for a "good speaker". Reliable, maybe. Good - I don't know, but it sounded like crap in that video (maybe just a bad recording).

That's a strange qualification for a "good speaker". Reliable, maybe. Good - I don't know, but it sounded like crap in that video (maybe just a bad recording). Less mass to move means less inertia. For precise playback of high frequencies, this is what you want. So having no moving parts in a tweeter is a great start. As a next step, one could figure out how to reduce the distortion that makes it "sound like crap".