What is a full-range driver?
A loudspeaker driver is an individual transducer that converts electrical energy to sound waves --generally incomplete without the supporting enclosure and tuning system that together make up what is known as a loudspeaker system (or “speaker” for short.)
The loudspeaker driver is nearly always of the electrodynamic type, consisting of a frame that supports a magnetic circuit, a cone, suspension system, and voice coil.
In usage, Harry F. Olson helped define the term full-range driver as:
Any loudspeaker drive unit capable of quality reproduction of bass through treble (musical terms, musically defined) with usable dynamic range when matched to the supporting acoustic space such as the speaker cabinet or mounting baffle.
Traditionally, single drive units capable of covering the bandwidth of roughly 60 Hz to 8 kHz have -- for over six decades -- been distinguished and marketed as full-range.
Zu specifically defines its use of the term full-range in its marketing efforts as having an in-room bandwidth capacity of 35 Hz to 12 kHz -- roughly eight and a half octaves.
The super-tweeter covers the top octave, harmonics on muted trumpet, pan flute, a bit of shimmer on cymbals, and burnish on strings.
For more info and perspective on full-range driver terminology and history, please see "Wannabe Curation Communication" listed under "Forum Claptrap".