I haven't heard the VS DB99s. And specs seem sketchy. I own Zu Druids and Zu Definitions in two different systems, placed in two different rooms, but I have directly compared both Druids and Definitions in the same rooms, using each system and moving the required speakers around. So I can answer some of the matrix of questions here.
A little preamble: The DB99 is described as a 3-way, implying that it uses passive crossover elements in the signal path to all the drivers. If this is true, it would likely be the primary weakness compared to the Definition. Until I got Druids and then Definitions, I had not ever heard a full-range-driver-based speaker that I could also describe as being tonally accurate or natural. But once you get the combination of full-range driver + tonal accuracy, the presence of a passive crossover -- even in speakers I formerly enjoyed -- is very hard to accept ever again. A crossover just asserts itself, squeezing life out of the music and disintegrating the holistic sound you've now become accustomed to. It's that holistic difference that SET adherents cite over push-pull amps, made large. Obvious. Anyone can hear it. We've all been living with this limitation for eons and now we don't have to. The holism and tone of the Zu designs is the first reason to make the effort to consider them.
Certainly the VS and the Zu Def are evenly matched as marketed items, costing close to the same, having pretty much the same design objectives, and consuming very similar footprints.
How does one describe a Zu speaker to someone who hasn't heard one before? It's a fully integrated, holistic sound. As a former Quad ESL owner, Druids most remind me of what was compelling about Quads -- intimacy, quick & uniform transient behavior, excellent octave-to-octave balance, beautiful tonal accuracy. But they add true dynamics and high sustained SPLs on very little power. You have huge latitude for amplifier preferences, everything from 2 watt 45s to McIntosh solid state monster monoblocks. No worries.
As usual, someone speculates that the Zu FRD must beam problemmatically. This is not a practical issue. The 10.5" FRD rolls off naturally at 12kHz and its directionality is much less constricted than a Quad ESL-57, and somewhat more than, say, an Anthony Gallo or a Spendor S3/5. I have one system on the short wall of an oblong room and the other system on the long wall of a less oblong room. I have absolutely zero seating positions where I cannot maintain a dimensional soundstage with convincing frequency response. And the swet spot is a good 3 bodies wide for Druids and more for Definitions.
The Definition is specifically designed to reduce floor and ceiling effects and improve horizontal disperson over the Druid, partly as a nod to mixed-use (video HT / serious music) systems. The MTM array on front, while not strictly a D'Appolito configuration by the placement math, acoustically controls the upper mid and treble response of both the FRD and the super-tweeter. Here, in any practical domestic room I can imagine, beaming is simply not in evidence and dispersion is both quite unlumpy and controlled for excellent practical use. The Definition is easy to set up and pretty much a drop-in for an existing system, from which point you may wish to re-optimize based on your inevitably new satisfaction criteria.
Again, absence of crossover is a commanding, compelling attribute. As I've written before, it turns out that when you eliminate crossovers in the meat of the music range, and retain phase linearity, lots of affordable sources are perfectly fine. I think a lot of what audiophiles have been wrestling with in endless upgrades has been traceable to the "pinhole" effects of crossovers being assigned to dissatisfaction elsewhere in the system. My point is, if you get any Zu speaker and are the type of person to put 40% of your system funds into your disc player or TT/TA/Cart, you will want to stop that right now and realize that the fulcrum of fidelity in your system has just moved to the power amp. With Zu speakers in place, your power amp selection will now have the largest effect on your system other than moving further up the Zu line or finding something else to exceed them.
As for playing loud, any Zu speaker is up to the task of caving your skull in, if you ask it to. Even Tones. Druids can put you awash in cell-squashing SPLs in normal rooms, on a relative handful of watts. Don't underestimate what one Zu FRD can load a room with. The Griewe model in the tower gives you quick, tuneful, articulate and full bass down to a little below 40Hz before it smoothly rolls off. The Druid is deceptively simple, but compared to most speakers, scales just fine.
One look at Definitions and you expect them to scale. They do. That 16Hz - 40Hz range missing from the Druids? There are 4 ten-inch light-paper-cone drivers fed by an in-built amp to take care of that. The lower range is present and accounted for as claimed, but unlike the vast majority of subwoofers and other deep-bass speakers on the market, this array on the back of each Def does more than indistinctly rumble and slop around. It retains the speed and articulation that are hallmarks of the main drivers. The dual FRDs perhaps sacrifice some of the Druid's ultimate focus and single-driver intimacy, but they burst with startling realism, projecting sound into the room multidimensionally and laying out a soundstage as captured in the recording. They do, in my experience, require at least 9' - 10' of listening distance for the soundfield to fully integrate in your mind, compared to the Druids which can be used relatively near-field. Of the recording is up to it, you will feel the power of a full symphony orchestra in your skeleton. The SACD of DSOM will be clean and clear right up to the dynamic limits of your room. Definitions live up to their name, being stellar in their ability to keep simultaneous sounds and musical events distinct as density, intensity and SPLs rise.
In Zu speakers you can find both truth and beauty. As even Zu admits, the Druid is less perfect than the Definition, which is why there's a Definition. The Druid is discernibly less linear as you'd expect being less than 1/3 the cost of the Definition, but has superior small-scale intimacy. It is a seductive, beguiling speaker and a true revelation the first time you experience it. I'll suggest further that in your home is the very best way to have your first Druid or Zu experience. The retains compelling if not-quite-Druid intimacy, and improves everything else across the board. These are not euphonically colored speakers. Definitions in particular are ruthlessly revealing of any hash, grain, or general unpleasantness elsewhere in a system. Get the power amps right for your purposes and everything else is pretty easy to sort out. Pianos will sound correct. vocals will include the person instead of being disembodied. Dynamics and transient uniformity will be responsive to the music and you will hear an aliveness to performances that is seldom achievable in home audio.
Certainly, there are many people who revere the VS DB99, citing some of the same attributes. Different people are sensitive to different properties in our highly imperfect devices for sound reproduction. What I can see about the VS online does not give me confidence it can achieve the holistic sound of Zu that is vital to me, but I'd have to know more and hear them to be sure. Here's what we do know: with a Zu speaker today, your amp signal goes to the driver(s) producing the 40Hz - 12kHz range without passing through a crossover network. No RC. That FRD rolls off naturally on both ends, and the supertweet rolls in on a simple filter. Do you hear the holistic sonic character made possible by that, without giving up real highs and bass? If so, you're likely to prefer Zu. If not, your preference may drive a different outcome to your decision.
Since owning Zu speakers, I've had more moments of being startled by a moment of "live" sound, than in all the previous 30 years I've been buying audiophile-grade gear.
Phil
