Zu def 4 are they the best speaker made?

Best speaker .I would rephrase it most musical Louddpeaker, Hardly 
Not even in the top 20. There are way too many  high quality
Reference speakers out there.

I’ve owned druid mk3, omen, and now the definition pro with upgraded drivers and tweeters. the older druid’s didn’t work for me, not sure why, i think zu hadn’t really figuired out the design of the version of the driver they were using at the time it or possibly was a mismatchwith my tact millenium and I wasn’t willing to give up my millenium at the tim. omen’s were fine but at that pricepoint you can’t expect too much. My definition pro’s are just about a perfect match with my First Watt Sit-2 amp and ps audio perfectwave dac. have owned them for a few years and and will keep them for many more. The newest generation of the drivers that Zu is using today are pretty spot as far as transparency and detail is concerned.

I heard the Druid MK VI’s recently and they sound really really good. One negative I could discern, and this is something that I remember from my old druid’s, is that to me, snare’s just don’t sound right. There’s a grit and courseness to snare drum’s that doesn’t sound natural. Bottom end extension with no accompanying subwoofer was impressive. I actually thought they were running a sub and they weren’t. Was told they spent quite a lot of time dialing in the speaker placement. They can’t touch my Definition Pro’s tho’. not even close.

With all that, what I truly don’t understand are the price increases that have occured over the years. Mk3/4 druid’s retailed at $3500(I paid 1900 on sale and they were worth 1900 not 3500 imo), MK 5 was something like 6500? And MK6 are now a whopping 10K! which is older Definition territory. I want to know what kinda special sauce they are putting in that s--- to justify the steep increases. Def’s are now 17K! Zu used to be about somewhat affordable audio, no longer it seems.

Yes

Unless you are playing them outside, the room has the most impact on how a system will perform. That's the bottom line.

maybe these speakers just work with the op's set up.  I've had a few speakers in my systems over the last 30+ years.

I currently run a fully modified and upgraded pair of SoundLab A1's augmented with a pair of Sunfire Subrosa subs.

so far, that's been "the best" speaker set up I've had. Before that it was a pair of Carver Amazings... so as someone else pointed out.. it is all about room interaction and context, plus your personal preferences..

Love the Zu guys.
Something very appealing about the "live" quality of their high sensitivity speakers. I have had Druid in and out of my setup several times. But they are currently sitting disconnected in the hallway. Because for me tonal balance is a priority. Check the response curve:
http://www.soundstage.com/measurements/zucable_druid/
They are very fun listening, but not an everyday solution according to my preferences.
PS. That curve is for an older version. I hope someone can post a link to measurements for a more current model. It probably looks a lot better. Of course measurements aren’t everything.