What makes speaker's sound big?

Give it a rest

Martin, no point source speaker is going to produce a life sized image. What you get out of them is a mini sound stage like you are sitting all the way in the back of the hall. Another problem is the sound pressure level of point source speaker drops of at the cube of the distance, very quickly. Linear Arrays or Line Source speakers produce a large image like sitting up front. Sound pressure levels drop of at the square of the distance, much slower so Line source speaker project sound better. In order to perform as line source a speaker has to be tall, preferably from floor to ceiling which unfortunately does not suit many people. Also unfortunately, everything else is just wishful thinking. You can be sitting in front of the biggest Wilson but close your eyes and you get the sound stage of any run of the mill floor stander. This is one of the reasons people love their Magnepans. Except in the bass Magnepans give a more life like sound stage because they function as line sources above 150 Hz.

Low distortion, low distortion on transients, wide dispersion, very low coloration, smooth FR.

many very small 2-way speakers with these qualities have an ability to sound HUGE and effortless.

As mentioned, a great sounding room.

I've owned Tannoy FSM with 2x15" drivers per unit.  Also owned little Harbeth P3ESR.   When I set up the P3 using the "Golden Ratio" (speakers 1/3rd from front wall, listening position 1/3rd from rear wall) the speakers disappeared & the whole room was full of sound.
If I had a dedicated listening room, that's how I would set up.


But I find a major factor is Source Material. Some recording have space.  Some are shut in.