Big speakers, are they really the best way to get great sound?

Boomieness happens when someone hasn’t run REW on their system and confirmed the (size/dimension driven) room modes - and corrected for them.

The reason big speakers appear to produce them, when smaller, speakers don’t in the same room- is it a small speakers roll off sooner, so may benefit from the additional reinforcement below 100 Hz- even if peaky.

And although not everyone has room correction DSP in their pre-amp, if you’re using Roon, you can add it there- or more importantly, for this conversation “subtract it there”

Narrow Q cuts aligned with your measured room Modes do wonders for full range  speakers and subs - anyone who would invest big dollars for a truly full range speaker - should also set aside the time for this step (And room treatments)

TLDR boomieness isn’t inherent in big speakers - it’s a function of your room - and it is revealed by them.

While I agree that room treatment is extremely important, the system i was listening to in my OP had been treated. The demo was done by folks who I believe actually do know how to set up a room! ( I am not sure why folks here many times come to the conclusion that room acoustic set up is something that experienced a’philes and dealers fail to do??). The question, and I believe this is where I was going with my OP, is such a large and ambitious speaker with the ability to easily override a room really what we want in our listening room? To that, is it possible that even with room treatment ( and a very large room) that a speaker can still sound too large? I believe the speakers in question ( which admittedly I have only heard this one time) could possibly have a design flaw that actually appeals to some, and not others (like myself).

@baylinor Your post is interesting. Every time I have heard PBN’s, and I have heard them many times, since they are a local company to me, they do nothing for me at all. This tells us that in this hobby, everyone has a different taste and expectation of what is right to their ears. Clearly, the Montana’s work for you, and you appreciate their sound.

In the right room, yes, large speakers are the best way to get the most accurate sound. 

I have had quite a few opportunities to hear large speakers: Von Scheikert Ultra 11, large Wilson's (can't remember which), Acapella Audio CAMPANILE, Acora  Acoustics VRC-1, Estelon Forza, and others. 

Their ability to reproduce realistic scale, cannot be equaled with smaller speakers.

Having heard the Von Schweikert Ultra 11's quite a few times, I have heard them reproduce a full orchestra at realistic scale as if I was sitting 12-15 rows back at Disney Hall, then be able to reproduce a solo singer with a guitar, also at accurate size and scale, is hard not to be impressed with. 

OP,

The Montana XPS do need a long burn in period, minimum 400 hours, and they need to be playing at least at 70 db to do them justice. 75 db is my sweet spot. And of course it is totally system dependent. I do appreciate your gentle approach to my comments even so PBN is not yourcup of tea.

Most of us have had that experience - go to a show or dealer, listen to an ostentatious 6-figure dollars (or more) huge speaker, and think to ourselves "god this sounds mediocre or even outright BAD; I vastly prefer my own system!"

This IS a good representation of how hard it is to get a large-speaker system right. It can be much harder than with more moderately sized speakers. This IS NOT a good representation of what a truly well crafted mega-budget large system CAN do. The upper limit is much higher, but getting there is the trick. Amp matching is also crucial at this level.

Two of my major "meh" moments were with Focal Utopias a few years ago - Stella III and Grande III. Driven by electronics deep into 6-figures themselves (Soulution). But then I really dug the much cheaper Sopra 3’s in the next room (VAC Statement tube amps)! Maybe Utopias are just the wrong speaker for me, or maybe I just haven’t heard them yet in the right system. Another time, much longer ago (15 years), I had a "meh" experience with very large Wilsons (Maxx?). I sort of remember enjoying them more than I did the Utopias, but still not nearly enough to justify their expense. In another room at that same event, there were huge McIntosh line arrays which I though sounded VERY good (of course driven by Mc amplification), and at least made a good run at justifying their cost!