Anyone listen to Zu Audio's Definition Mk3?

Well, the Def4s have arrived, and I'm still taking stock of them, so my considered response will take the form of a few postings. I thought I'd leave a few initial impressions. First aesthetics; I'm SSSOOOO glad my girlfriend made me go for Cosmic Carbon, it's such a good match with the Aluminium driver rings and tweeter lens, and fits my loft decor perfectly. This finish never seems to work in photos but is to-die-for in the flesh.
So, the sound. Yes, it is a cliche, but it really sounds like a different speaker, but the same. In a nutshell, it shares all the DNA of my previous Def2s with a definite increase in sophistication common to spkrs much further up the price scale.
This is most noticeable in a quantum leap improvement in transparency. There is a real "hear thru" quality to the sound, but maintaining the Zu tonal density. But now, instead of a concentration of musical energy into a sort of wall of sound, there is a more layered quality to the presentation. It's the same, but very different. This increased transparency really allows music to breath more easily than the old Def2s, which seem coarse by comparison. This is the only area where I disagree with Roy Gregory in his Audio Beat review, IMHO there is no "harmonic leaness" (about the least accurate criticism to be levelled against Zu).
But don't be fooled if my words make you think that we now have a polite, twee sound. No , nothing of the sort, and I'll explain more at my next post...

Ok, time for the second part of the early listening experience with my new Def4s. At present I'm only listening to cd, and as an analogue fan, any extra enjoyment when listening to the necessary evil that is digital is a massive plus.
I previously referred to the more sophisticated sound of the 4s compared to the 2s, summarised by a massive increase in transparency and delicacy, no doubt a direct result of the improved full range nano drivers. Initially this appeared to be at the expense of tonal weight, but on further analysis I just wasn't used to the massive speed of these drivers. The old drivers in the 2s sound earthbound on reflection.
The great thing is that once adjusted to this extra speed, you realise the delicious full bodied balance of the 2s is maintained into the 4s, and the ante is really upped by this lightning fast transient response. So now we can have tonally dense, the trademark Zu sound, in combination with a lot of what electrostatics have to offer. I'm not sure I've heard such a magic combination even in uber spkrs like Wilsons and Magicos. I was really fearful the Zu sound might be "tamed" in the 4s, but this extra transparency really has just enhanced all that the 2s had to offer.
So, that's a summary of 90% of what these marvels have to offer. Next I'll discuss the bass, and fear not, there'll be LOTS to discuss here...

"Initially this appeared to be at the expense of tonal weight, but on further analysis I just wasn't used to the massive speed of these drivers. The old drivers in the 2s sound earthbound on reflection."

I had the same concerns at first with the nanotech drivers, but as I grew more acclimated and juggled a few tubes to compensate for the new signature, I arrived at the same conclusion as you. The weight and body is there--the speed and nimbleness is just initially misleading.

Absolutely, Gopher. So, I've covered the all important FRDs. Now onto the bass. Any reservations as to 4 x 10" woofers being replaced by a single 12" dedicated sub were blown away by the rapid realisation that the full bass extension of the 2s had been retained with a greater speed, agility and tonal differentiation in the 4s. Finally I'm able to integrate the bass much better into my room, and vitally, it integrates itself much better with the FRDs. This really makes for a seamless mid-low spectrum, and much more spatial and temporal microdynamic presentation, especially revealing of bass ambient clues (eg the edge of organ notes as they reverb in the recording space) and bass impact (eg differentiation of individual kick drum/piano hammer strikes). The boogie/party factor is all present too, with fantastic PRAT. Rest assured, the bass of the 4s is of a whole magnitude better than the 2s, and you will not find it wanting. I'm sure the more substantial weight/bracing/plinth of cabinet is making a major contribution here.

Sorry A'goners for my delay in my last posts re the Def4s, but "real life" intruded over the last week. I've found that as I've gotten older, and family/business issues become more serious and intrusive, I more and more really crave the serenity that a great audio system gives me, and my stress can melt away while listening to my regular diet of 3 albums a day.
Anyhow, covered the FRDs mids and bass, last thoughts are on treble. Here I'm a little less decisive in raving about the 4s. This is only since previous comments stated it to be qualitatively a leap beyond the 2s whereas in my room it is more of an evolution.
What I always loved about the 2s was the absence of the sort of spotlit treble evident in so many high end spkrs, and I do feel this characteristic isn't changed dramatically by the 4s. Now I know that this is a flavour imposed by the FRDs, and since the mids are SO much more transparent and delicate in the 4s this is likely what I'm experiencing with the treble. Again, high frequencies aren't overt until dominant in the program material, and then the music soars into the ether.
So my final conclusions. This is an AMAZING speaker, and a leap beyond what the 2s were able to offer. Most importantly, the new FRDs really introduce an electrostatic like transparency and delicacy to the addictive tone dense sound that we all love about the 2s, with no down side.
Bass is really impactful, more tuneful and much more integrated into the whole. Treble is less noticeable as a step up, but this may be the point: the FRDs covering it are so brilliant on mids on up that this character into the highs is all part of a subtle blend.
I was SO fearful upgrading sound unheard, but all has been allayed. The 4s are an absolute giant killer, imho really treading onto the territory of uber spkrs over 4x the price, but maintaining and enhancing the addictive tone dense Zu sound that no other spkrs seem to approach.