Chazzbo,
The appeal of Zu speakers is in their holistic representation of music. Frequency accuray is sensational on Definitions, and very good on Druids. Phase coherence is about as good as you have experienced and far better than most speakers. Top-top-bottom consistency of transient behavior is uniform. And detail is revealed without sacrificing body in the tone. Add to that the ease of driving 101db/w/m speakers with relatively benign impedance curves and you have speakers that are unusually communicative of expression and intimate, but which scale spatially and dynamically to ambitious music.
I have two systems, one built around Druids and the other centered on Definitions. After over 30 years of serious involvement in hifi as hobby, and the music interests behind that, Zu speakers are among the top handful of genuine advances in fidelity I've heard in that time.
A key characteristic that drives the unusual tonal excellents and coherence to the Zu sound is absence of crossovers. You don't have to accept the tonally disruptive effects of crossovers, and the dynamic constriction they inevitably cause. Being free of crossovers can take some getting used to, as can the phase linearity of the full-range driver design, but the behavior of these design attributes is startlingly reinforcing of your illusion of musical reality from recorded performances. The jump factor of very high efficiency combined with a strong-motor driver that is as dynamically engaging as real instruments only adds to the value of Zu's speakers in an overhyped market.
Last, don't discount the contribution made by having speakers able to be driven forcefully by modest output amplifiers. Able to choose power amplifers on the strict merits of sonic signature and not on power, Zu owners have unusual latitude to find their sound.
Phil
