Thats what I thought until I added a 2nd sub. The new 21 inch sub is in the front right corner where my old sub was and I moved the ML BF210 to right behind the sofa for nearfield. The sound is much improved.I run 13a as main speakers and a single bf212.
I have copious amounts of very deep tuneful bass. I have the bass speaker smack bang in between the main speakers. The bass is seamless I can’t in my room see any benefit from more subs but????