A question to the Sound Engineers out there

The usual problem of asking a question about how its done assuming its all done the same. No one can say what "sound engineers" do because they do all kinds of different things. Not only from one engineer to the next but even the same one from recording to recording over time. 

Also the recording engineer pretty much does what the producer and performing artists want, which in turnhas a lot to do with the intended audience/market. 

If you want to know technically how ambience is created in a studio there's multiple options few if any having anything to do with being able to hear in the studio what you're hearing at home. 

I think the studio in the Bricasti video above is probably not like most studios. having said that there are some record labels that go to extremes.

Tacet - a label that goes to extremes when actually recording their live recordings do not have elaborate studios with big monitor style speakers either.

I do have some recordings from Norway that are amazing sound quality - so are their studios it seems - just a tad more extravagant.
norway recording studio images - Google Search

I guess these small speakers we see in the images are actually very good quality and you can't see if theay are coupled with sub's, so the "impression" is, their sound is rather limited. But I have to believe this is not the case

Tannoy seems to have gone to 6" drivers on their Recording & Broadcast speakers, so I guess the industry in general as moved in that direction and probably use sub's to augment the low frequencies.
Tannoy | Catalog | Product Applications

But I'm still confused as to how the sound guys create these cavernous images in such a restricted environment.

Regards - Steve

A studio loudspeaker is a tool to be used by a technician.  It doesn't have to be state of the art or even accurate.  It just has to have a consistent sound.  As an analogy, professional chefs don't need expensive knives and fancy pans to make wonderful meals.

Cavernous sound is created by reverb.  Here's a primer on reverb history and use.  Bricasti was founded by ex-Lexicon designers/engineers.  Lexicon made the most widely used reverb devices, primarily the 480L.

Some do listen on home hi-fi configuration. Two I know are Octave Records, whose releases have to pass final audition at Paul McGowan's music room at PS Audio; and Andreas Meyer in New York who has a mastering/listening room akin to a home set-up.