Placement of subwoofers

I have two Rel T5/x paired with my Dynaudio Special 40 bookshelves.

My first experience with subwoofers, I initially followed Rel's guidance and put them in the corners of the front wall.

That produced lots of bass boom, prompting an all-day exercise, moving them all around my listening space (a living room like yours) to try to get upright bass transients clean and clear.

I ended up with them out in the room, on either side of the couch where I listen.

Strongly suggest (as others have) a room mode calculator like this one to try to understand where bass is piling up: Acoustic calculator: Room modes

That and a tape measure per Hans' room correction recommendations helped show me where to cut out certain bass frequencies below 300 hz with eq, in my case using Roon's eq feature. Roon eq is really useful because from your listening chair you can turn on and off the frequency band stops you assign based on your modes and room measurements and see how the sound changes.

Free basic room correction - YouTube

Can't say I've got a lot of boom now.

I also have the gain and crossover settings, that I set by ear, quite a bit lower than Rel's recommended starting point. This is likely due to my mostly square room, which I believe really accentuates the bass for me.

I'm no expert, just my experience. Happy listening.

Subs in corners? LMAO!

@dcpillai : I am certainly nowhere near an expert in subs or their placement.  That being said, I have always found sound systems incorporating them, especially in a two-channel system, sound best when they are placed exactly between the left and right channnel speakers but not forward of those speakers.  A little behind them is OK, as long as the sub remains in the center between them and there are no obstructions in front of the sub. Kind of like why the drummer(s) in a band are usually always center stage and behind the other musicians, I guess. This would certainly complicate things in your room placement. You'd have to move your rack & components.

@dcpillai You have a very nice rig and have invested quite a few $$$.  This being the case, spending a little more on bass traps makes sense.  Adding the traps will do two key things.  It will give you much more flexibility in placing the subs.  Also, it will clean up the midrange of the mains.  Good luck and cheers.

IMO, you should try them at different locations and angles.  I have two subs and found the best sound (so far) by having one facing the same direction as the speaker and just to the outside of the speaker.  The other sub is at the outside of the other speaker but angled at about 60 degrees inward (toe in).  This removed the bloat in base that I was getting when them in the corners or facing forward for my listening positions.  Seems very room/furniture/equipment dependent.   It was a very noticeable change.  The big base sound is still there, but in the right amount.