@lemonhaze Great advice on room response. Some don’t have tools to use to dial in the sub or subs if more then two so they play it by ear. Luckily I have REW but I use more with DIv2 a Rational Acoustics software and for this purpose it is great. For my situation, I have Vandersteen 2ci speakers which has the bass couplers that has enough bass so one sub for me is more then enough to reinforce the lower bass response.
I have read the links that was posted earlier and really has some great information. Peaks are easier to tame then nulls as long the nulls aren’t more then 3 db difference.