Zu Druid MK IVs vs. Essences

I own Druid Mk 4-08 in one of my Zu-based systems, and directly A/B'd Essence with them in my room.

I've written before here that I consider Essence the least-Zu speaker. It was a successful speaker for Zu in part because it has some characterisitcs appealing to what I'll term the hi-fi buyer rather than the music listener. Essence sounds more like the average hi-fi buyer expects a loudspeaker to sound, while still delivering the essential qualities of a Zu cross-overless design: holistic tone, high efficiency, transient speed and articulation, and excellent octave-to-octave balance.

There are two problems with the Essence that resulted in Druids remaining in my secondary system, and both pertain to the ribbon tweeter. First, because of the supertweeter's relative inefficiency, the FRD had to be dialed back for the two to be in balance. The result is a 4db loss in efficiency in Essence relative to Druid, and it's quite audible. Essence is less bursty, plays with audibly less dynamic life at a given power and generally sound comparatively constrained. Now, if your only prior reference is a less efficient crossover-based speaker, then Essence will sound lively compared to that. But against Druid, Essence sounds a trifle flat. Second, the essential tonal quality of the ribbon supertweeter is mismatched to the tone density of the FRD, and for me it is distractingly zippy and bothersome. There is audibly less unity between the FRD and the handoff above 12kHz.

So for the latter, some people aren't bothered, but then I've yet to hear a ribbon tweeter I can live with. The former issue of detuned dynamic performance to accommodate the ribbon in Essence is real for anyone who has a chance to hear both. I am specifically recommending Druid Mk4-08 over Essence, though less so the earlier versions of Druid.

Of the current Zu speakers, Superfly costs less than Essence and trounces it on dynamics, musicality, tone density and for being generally musically convincing. Superfly is a sensational speaker worth amplification of considerably greater cost. If you have a large room to load sonically or you just like a spatially bigger sound at some expense of ultimate precision and focus, Omen Def is also preferable in my mind to Essence.

Phil

>>You can't seriously expect these speakers to be accurate.<<

Yes, you can. Look, it's simple: Druid's design *requires* a floor immediately beneath the speaker for it to operate correctly. Changing the floor gap by millimeters alters bass response and if it is set up wrong to be too tall, the midrange can begin to be affected. Dial it in right, and Druid's tonal response smooths out. Within a practical adjustment range, the floor gap can be used to tune bass response to room characteristics or subtle specific user preferences. The speaker in use sounds nothing like the graph from Soundstage's mid-air test.

Essence, Superfly and the Omen series also have varying levels of Zu's proprietary acoustic impedance loading scheme that open the cabinet to some degree on the bottom. All have been engineered to sharply reduce the floor gap sensitivity that was elemental to Druid, with Essence specifically having a double plinth to enforce its own "floor."

Definition 1, 1.5 and 2 were sealed cabinet speakers. The upcoming Definition, Experience and Dominance models do not vent through the bottom, so floor effects are not a factor.

If you set up a Griewe loaded Zu speaker correctly, it will test and sound like the relatively neutral speaker it is.

Phil

>>Is that all? Those measurements suggest way more issues than that...<<

Druid, at then $3600, was not as linear as the later $11,000 Definition, Zu's second speaker. But then no one expected it to be. It has a somewhat warmer overall tone than Definition, Superfly and Omen Def. But it was accurate as loudspeakers go, and smooth rather than ragged in its response. The lack of a floor under the partial Griewe loading scheme affects the full range driver's performance well into the midrange.

Most speakers yield a test graph more ragged than they sound, BTW.

Phil

>>The floor excuse just doesn't cut it.<<

If you don't understand how Zu's proprietary acoustic impedance model works, and how their full range driver is affected by it, then your assessment of the "floor excuse" is invalid. This isn't a multi-way speaker with a cardboard tube port we're discussing, so it doesn't behave like one. Hear it properly installed and you'll also hear that the speaker doesn't sound like the graph. And certainly no speaker/room combination in normal domestic construction has flat response. The speaker and the room cannot be divorced from one another. Attempts to measure speaker response in a non-interactive room are irrelevant to what you'll hear if the test is conducted with the speaker in a position where one of its critical working elements is removed.

More important, no current production Zu speaker has so completely an unmitigated dependency on being placed on a floor to perform well, though to varying degrees some kind of resting surface is advised.

Phil

>>shows that the Zu Druid is a Paul Voight type design<<

It isn't. In Druid there is no interior taper and no progressivity in managing the rear wave. Also, the driver is placed at the top of the tube, which is not the usual Voight approach. It's also not a transmission line, though the speaker might externally resemble that. Druid was the first instance of Zu's proprietary acoustic impedance matching model, and it is only a partial implementation, relying on both a specific cabinent interior volume as well as precise distance from driver to the floor via the floor-facing vent and the user-adjustable plinth-to-floor gap. The result is that the floor gap has much more than 3db effect on the free-space frequency anomalies. The speaker does not sound like the free-space test curve. If it did, no one would have bought it.

In later Zu models that are not sealed, the Griewe acoustic impedance model is complete, though slightly differently implemented in the straight cabinet and tapered cabinet speakers. In those cases the free-space (off-floor) performance is far closer to the on-floor performance, because the Griewe model is enforced within the cabinet rather than nakedly dependent on a user-adjusted gap between cabinet and floor. However, in Druid, the user adjustable floor gap does give the listener a valuable tuning device for managing the always problemmatic speaker/room interactions in the bass frequencies, in normal domestic construction.

Phil