What makes speaker's sound big?

Wide baffles seem to help.
Classic-shaped Spendor and Harbeth speakers for instance sound richer and fuller than most.
And certainly the Devore O series speakers sound way bigger and richer than their size would imply. 

IMHO, you can't get a bigger sound than when a speaker completely disappears.   I've never heard a 15" driver that imaged well or disappeared and they sound flat & lifeless at low volumes.

Have a play with placement.

http://www.cardas.com/room_setup_rectangular_room.php

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.

It is precisely why an array of 18 Helmholtz tubes and pipes can do marvel in modifying the sound pressures zones where they are located making possible a better synchronization of the speakers and the specificity of the room...

The measured sound pressure coming from a pair of speakers in a particular room could change much in frequencies range if we implement the H. grid with the appropriate ratio volume/ neck...

I did it with great result for my speakers point source : a soundstage filling the room and not coming from the speakers but completely encompassing them...A better timbre perception also... . In 2 listening position, different but astounding results...

The room is not only a passive set of walls where waves are boucing or absorbed or diffused only, it can be ACTIVATED with heteregenuous zones pressure distribution , modulo the varied locations of the Helmholtz pipes and tubes...

This is concrete science easy to verify....

Then your analysis is correct in a STATIC room with a definite homogenuous pressure atmosphere but you forget to say that we can compensate, increase or decrease the sound pressure levels at will with more active acoustical tools... Helmholtz bottles engines grid are only one type of these tools.... I use others also....

Acoustic is way more than what it is speak about in most audio thread by most people....

Most people have no idea because many acoustic tools are not suitable at all for a living room....

And most acoustic companies sells what is EASY and esthetical to sell, not what could be an optimal or more powerful tool but less easy tool to install with a complex set of experiments to deliver the results... Bass traps and passive surface materials are supposed to be all there is to do for most.... This is not true....


The room is not a set of walls, it is a pressure ENGINE....Helmholtz dixit.....

And "full" is still a factor of SPL at your listening location,

To conclude with your opening remark, we cannot complety change each characteristic of the different type of speakers, your post is clear and very right about that, but we can adapt them optimally to the room and adapt the room optimally to them.... That was my point....




My best to you......

I don't think anything you had posted previously had influence my response Mahgister. I think for the most part we agree.

I think I will try a pair Magneplanar 1.7i and a pair of gr research servo dipole subs

just to try something new