What makes speaker's sound big?

To me, there’s really no substitute for size in producing a grand scale and room-filling sound, the best of which by far IME are tall, line-array designs (Pipedreams, Nola, etc) and larger planar or electrostats.  Sure smaller speakers with better dispersion characteristics and some other things can help, but they can’t match the true scale and impact of the larger designs IMHO.  Given what you’re looking for, if I’m you I’d look at dipole, bipolar, or omni-polar speakers.  The only ones off the top of my head in your price range would be the Ohm MicroWalsh Short or the Magnepan LRS or 0.7, but there are probably some others I’m missing.  If you have more of a budget there are smaller models from Boenicke and Nola that are excellent.  Anyway, hope this helps, and best of luck in your quest. 

Audiogon, where the science of audio goes to die ....

For a point source with an unencumbered spherical radiation, SPL reduces by 1/R, or it is 1/2 at double the distance (-20log(0.5) = -6db. Sound intensity (power) reduces by R squared. Human's are sensitive to sound pressure (SPL).   For a perfect line source, SPL reduces by 1/sqrt(R), or 1/squrt(2) at double the distance of -3db.


However, no line source is a perfect line source, and walls, floors, and ceilings contain the spherical distribution so the equations above are guides, and the reality is somewhere in the middle.

And "full" is still a factor of SPL at your listening location, over an extended frequency range, no matter how you achieve it, and what gets to you is a combination of direct and reflected.  Larger room, and the reflected is reduced. Damped room and the reflected is reduced. Line source and there is less direct loss with distance, but less reflected energy to contribute to the arriving SPL.  Larger drivers provide the ability to achieve higher SPL with less cone movement at low frequencies. Multiple small drivers can achieve the same thing.  You still need to move the same amount of air, area*excursion, to achieve a similar pressure wave.

MA,
Wow pull something useful out these comments will require use of a divining rod.
-"Buy a Raven amp. pair with the DIs and die a happy man"!
-"Buy a Maggie"
-"Ohm Walsh!"


Singblues says you can trade 4 ea 15" woofers in for 2 ea 5" Harbeths and with enough placement experimenting achieve
a nirvana similar to his FSMs. 

My experience- Similar room size as yours. I use the Tannoy FSMs now and have tried the Joseph Audio Pulsars to see
how it compared. 
After a few days of "adjusting to Pulsars" you may forget what
you liked about the big boys. i.e. they move a lot of air and you feel it in your chest. 
I let the Pulsars go to another friend and am happy with the Tannoys.

The answer to your question only brings up more questions.
Good luck!!

The things that make a speaker sound big are driver size, cabinet size, and low end capability. You can not defy the laws of physics so when you go to a small speaker with subs you get an uneven wave launch of sound on the mids and highs that does mesh right with the bass unless the three pieces are larger like a big wide baffle mid high tower with a large subwoofer.

^^^ --- Well this is pretty much made up nonsense --- ^^^

Not much else to say. This is just ignorance of how to properly integrate subs.