One sub is very hard to put in a musical synergy with the speakers...
But if someone want only boom boom sound , it is very easy to plug it...
I plug mine few minutes and sold it... 😁 because i could not think how i would make it "musically integrated" ... i think that it must takes 2 ...
A balance sound is not a boom boom sound added...
But my short experience with ONE sub ( Kreisel K9 ) was not happy and i could not figure out a way to integrate it "musically" ...
But once this is said i am not a sub woofer specialist at all...But i love music and i hate boom boom... Perhaps i am wrong and there is a way in some room to do it musically with ONE sub... We must ask to a sub-woofer specialist for confirmation or debunking ...My intuition is location and room dimensions are very important for this problem then there is no absolute rule and in some case one sub can do the job perhaps... In most general case i think it takes more than one...