Bass Driver Size - how much better is an extra inch?

Room fullness makes all the difference in the world, and with no distortion these simple things will rank a speaker very highly.  

High end brand names take notice.

Im not sure that Im tracking that last post...??

Anyhow, yes, 6” drivers, especially dual, can produce a good amount of bass if high quality.  But a high quality 6” driver vs the same high quality 10” driver, and the larger driver will put out more bass.  This is just physics, right?  More cone surface area...

I went from two way monitors with a 6" woofer to two way monitors with a 8" woofer. Not only is there more bass but the quality of the bass changed. It seems more tuneful and resonant for lack of a better description.

I use a pair of 18" drivers in a 14 x 27 x 8 1/2 ft room.  No complaints.  An extra inch would basically take the drivers up to 20" or 21".  Not sure that would make much difference.

It is an engineering compromise, just like almost everything is in life. It is basic physics.

The larger cones move more air and hence provide a much more realistic and voluminous bass. However, the larger the cone gets, the less rigid it becomes, affecting the sound negatively.

If you could find an infinitely rigid material, which would never lose its shape regardless of how much air pressure it was exposed to, then you could build infinitely large speakers. But real life has limits :-)

There is also one more very important factor as to why most drivers (and hence the speakers) are smaller these days.  It is the WAF :-)