Hello,
In my system (G68), the 5 speakers (Yamaha DSR112/ERiS E8) are set as 'small'.
My subwoofer is a JBL 4645C (18") pushed by a Crest Audio 8001.
Last time I launched Mconfig, I have seen a column 'Size' with a value set to 0 at the end of the subwoofer line in the calibration page.
The range of value is 0 to 30 (and Max after that).
Set to 0 or 30, i have heard no difference when playing a CD in 2.1.
But yesterday, watching Dunkerque movie with my wife, my subwoofer was producing great big clean basses with a lot of punch (no boomy result).
The size parameter was set to Max.
So, how does the parameter work, what does it do?
I have found only one post on the forum about this with no more explanation

Serge.