How does human hearing calculate "big"?
Sure, louder things tend to be bigger but how does the human ear know that the stampede of elephants a mile away is "big"? It might not be loud but your ancestors started runnng, climbed the biggest tree they could find or hid in a cave to prevent being flattened.
From what I gather, it has to do with the quanity of reflections as one elephant wold have a few reflecions but a hundred of them would have far higher amounts. Run, Forest, run! The brain calculates what "big" is specifically to prevent us from being a foot supply, getting crushed by elephants or landslides as "big" generally means "bad". Low frequencies have the same effect, very low frequencies are never a good thing in nature--we equate low frequencies with very large and pote3ntially dangerous things. (you weak and puny human!)
Wide dispersion speakers tend to sound "bigger" than narrow dispersion speakers because of more reflections--look at bipole speakers, they reflect off the back walls of the room and mix it with the direct sound creating a larger effect for this reason. The Bose 001 when firing into a corner had the same effect--it has a large soundstage. You give up accuracy and clarity when you do that but for some people, they will give up accuracy for a large soundstage.
Other things that sound "big" are just large speakers--a PA stack of speakers will sound big because it is big! Blame your brain for that one, it is tuned to figure out if something is big and will it use us for lunch. Those massive front loaded horn bass bins and subwoofers sound HUGE because they couple for effectively to the air by using a low pressure "mouth" or horn exit which will get larger slugs of air moving more efficiently. I've heard those things called "air transformers" as they sure give that effect. Now couple four of them together, they will act as one and sound really, really big--such as rock concerts.
Around six years ago, I was able to purchase crates of speaker drivers and built a pair of 3-way line arrays. 48 tweeters, 20 three inch mids and 12 five inch woofers in each box (with subs to match) Each line is 6 feet tall and my MLP is at 11 feet. They sound huge--almost cartoonish when listening to a solo flute player player her---6 foot tall flute!
They have less than 10 degrees vertical dispersion and sit on 2 foot tall subs in my garage--no floor/ceiling reflection at my MLP. Step back 20 feet and you start to get reflections and the sound does change as the line starts to revert to point source and other such things. The horizontal dispersion is over 120 degrees because 3 inch midranges tend to be wide dispersion. I toe them in and position them to prevent side wall reflections and do "time-intesity trading" to keep the soundstage wide across several seats but prevent too much reflections from the side walls. It's a garage, not a studio so I play the cards I'm dealt. Those arrays sound big, they sound the same if I'm sitting down or standing up as the line is positioned to be on axis at heighs of 2 to 8 feet. They sound huge when in the garage but once I leave the garage in open space, they start to sound smaller--100 meters away they sound like a point source with decent treble respons.
Some people that build those types of arrays custom build them so they stretch from floor to ceiling to get maximum reflectivity and a larger than life sound.
I'm sure you can build thm that way on an infinite baffle or open back to create a dipole to get rear wall reflections thrown in to really go nuts (and people have) I've had fun building, rebuilding, tuning and measuring my line arrays and for garage use--they work very well! They always throw big sound because that would be a side effect of over 160 speaker drivers firing per pair--the brain hears all that and it triggers the big criteria.
Back in the day, I had a pair of 5" two-way bookshelfs and a sub, it sounded and measured well but did not sound big or had high SPL abilities. For rockstar mode, I purchased a pair of 3-way 15" woofer PA speakers with horn loaded midrange and horn loaded tweeters. They sound much larger than my bookshelfs even at the same volume. A 5 inch driver could not compete with a 15 inch driver in bass as the poor 5 incher could not compete with a 15" wide X 12" tall horn for the mid. My preference was for the bookshelf/sub system for most use because of the accuracy and I didn't need high/massive SPLs most of the time. I did notice the "scale" of the music was different, very interesting effect.
If you want to play around with that, just turn your speakers backwards and fire them into a corner--it won't sound good but it sure does sound different. If you want to play with large, high efficiency speakers you can rent them from pro sound rental places and have a good time for a weekend. (during the week rates are much cheaper FYI) Those JBL "sticks" that are line arrays would be fun to play around with, rent 4 to 6 of them to reach floor to ceiling or close to it. All sorts of cool speaker technology available for rent from pro sound places, sometimes it is better to rent the cow.
I'd throw out that SPL has a large factor in our perception of "bigness". Large, high efficiency speakers have very high, low distortion SPL capability so it would sound more naturally big. The other thing is what your eyes tell you, if you see a line array sitting in a room it is a big speaker (ask my wife, she'll tell ya!) The eyes tell the brain to prepare for some big sound just as your eyes tell the brain where the sound will be coming from when watching movies in surround. You can throw that in the mix if you like.
My line arrays do sound larger than my HT speakers in my living room when operating in 2 channel mode. The sense of bigness really expands when using multi-channel surround though--kind of the point of all those additional speakers and processing.
BE careful with "big sound" sometimes it sounds bizarre when listening to something that is very small and you hear it as larger than life big--sometimes too much of a good thing turns into a bad thing. Be careful out there!