What makes speaker's sound big?

A few years ago, in our prior house, I moved my audio system from our 13'x24' living room to a 24'x26' family room and my then pair of Totem Fire monitors and Velodyne sub woofer with a 10" driver just didn't fill the new room.  I ended up replacing the Totems with the Focal Sopra No2's and the Velodyne with a pair of JL Audio F113V2's and they did fill the room up.

We recently moved into a new home with a 14'x19' listening room and my setup definitely fills the room.  I find I'm setting the volume level on the preamp a few percentage lower.

I auditioned the Focal 1038's driven by a McIntosh MC452 (450 wpc) power amp in a speaker room that was about 22'x22' and was blown away at how they filled the room.  I would have "pulled the trigger" and bought those, but one of my audio buddies let me know that the Sopra line was about to hit our shores, so I waited a few weeks and ordered those.

Easiest answer ever:

MAGNEPAN

I realize that every manufacturer is not making tall speakers--wonder where they got THAT idea??

Try the best and the original.  Jim Winey was a pretty smart engineer, I guess.

Cheers!

Even though I know you guys like to shyte on MC, as an owner of a pair of Double Impacts I gotta say adding just one subwoofer so far has made a huge improvement. The sound got bigger and I think it brought out the mids and highs as well.
Been looking for a new house with a dedicated audio room. I plan on 2 subs when we get there.
From what I understand it will get even better.

My experience with the DIs are that they are big and they sound even bigger than they look. I dont think any small speakers are going to rival that aspect of sounding big. Different and possibly better. Sure .. but a sound coming close to rivaling them in sounding large, I doubt very much. 

A small room!

OK lots of good answers and some not so good.  There are a number of key factors making speakers sound bigger:

1 - Design - many speakers that sound big have cabinets that are narrow allowing the music to flow around them.  Flat faced speakers not as much in my experience.

2 - tweeter position - top - middle etc., will sound different along with a rear firing tweeter.

3 - bass drivers add to a bottom and do aid in the perception but not always

4 - Equipment - how does you amplifier impact the sound.  In building amplifiers, I experienced an amp driving a pair of old AR speakers from the 70s or 80s come right out of the box.  More open sounding than many high end systems completely filling the room with sound.

5 - I have heard a customer who owns both the DI speakers and also the Spatial Audio speakers.  Guess which one sounds more open and room filling with depth to the soundstage?

Happy Listening.