Subwoofer recommendation and wisdom

Your room looks like this... Now, you can see why these old men on audiophile forums touting their apparently "full range" speakers never escaped the physics of bass in rooms. Their "full range" didn’t freaking matter one bit....

Buy 2 of these best bang 4 the buck starke subs, $499 each. Set a crossover of around 90hz. You need that rotary phase knob (not some 0/180 flip switch), which these subs should come with...very (très très très) important.

https://starkesound.com/products/sw12

(If you have 4 subs, you can get away with upto a 120hz crossover.)

Start with placement as follows, sub1 @ 1/4th from left wall, sub2 @ 1/4th from right wall.

Good luck.

2 subs is better in my experience.  I’ve had a positive experience with SVS sealed subs for music.  They just came out with a new SB 3000.  You get 5% off buying two and you get to buy, try for 45 days and return for free if you’re not satisfied.  They also have excellent customer service.  You can call and talk to a real person before, during and after the sale.  

yes, one of the popular myths is that two subs is better than one.

@parkergetdean  Yeah no, it’s not a myth at all and very well documented in research and by the experience of many here.  Todd Welti is a foremost expert on subs and you can read his research and thoughts on why two subs are significantly better than one.  I agree with @jastralfu that if you can only afford one decent sub then do that with the intention of adding a second at some point. 

Hello @stuartbmw3 ,  one question, several answers.  Yes no doubt two is better than one, and I am a huge REL fan, and have pairs of Carbon Specials and Carbon Limiteds.  But sometimes you can get lucky and one sub can work pretty well, especially if you can play with its location.  You don’t node if you don’t node. In my family room I can unplug one and it still sounds great.  In my basement two subs really evens it out, and I still got some booming I handled with corner traps.  Get a good sealed sub and go from there, with the thought you may want another one.  I avoid the DSP complication and appreciate my music least processed.  I do run my basement subs with REL wireless and that allowed me to move them around very easily until they didn’t boom.  It was not where I initially envisioned them!  No one can draw a diagram that is sure to work unless maybe if you have a very very regular room. The REL wireless works extremely well.  And, once dialed in, I find no need to mess with DSP and sub volume from my chair.  Oh, and people that say their speakers don’t need subs, generally have not heard well integrated, musical subs.  They add physical touch, recreate the real music, and support soundstage and imaging; especially two :)

PS - Also try the AM Acoustics Room Mode Simulator, it's amazingly good at visualizing your issues, if any.

The biggest issues with single sub solutions are big, narrow peaks which define the sound.  The peaks can be so bad, up to 20x more power than non-peak output, that you can't turn the sub up.  For ideal integration you want to measure your room and have the ability to clip the peaks appropriately. then you can raise the volume and have what the  OP is describing. 

Also, often  beneficial to plug ported main speakers.