The Room

Wanted to start a discussion about the importance of The Room. I had my system in a room 30x40 feet with concrete floors and 9 foot ceilings. Never felt right. Then because I am a health care provider, I got kicked out of the main house because of COVID concerns and into the guest apartment. I then put my system in the guest house into a 14x25 foot space. Very much different. Actually, a world apart difference. So much better.  Not saying I did it right or wrong. Just saying that it is amazing the difference a room can play. Whether treated of not, the room plays a dramatic outcome in the reproduction of sound.
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I always knew I needed my own place in my house where I could practice in peace and not disturb anyone. Thanks for this post, I will now revisit my office and layout, I don't think there is much room.
Room treatment can be tricky. The first thing you may want to figure is where your listening spot will be. 

Concrete...yikes! Deflections of sound waves from hard surfaces is detrimental to sound quality when using speakers. Acoustic foam and perhaps a floor with carpet are good steps to take.

I may upgrade my basement to have my own private listening room. (Soundproofed) etc. 

Yeah, totally the room you listen in can make a big difference.
I would also say the 2 subs, REL T-7is, are much easier to set in the smaller room than in the bigger room. Not sure if I just wasn't doing it right in the other room but they are completely different (better) in the smaller room.  A nice perk. 
Great article today on this subject on the link below. I read this guys book and spoke to him by phone a few months ago about getting a too big speaker to fit into a small room treated room. We are going to make it work.

Sorry to hear you were put out of the house, so to speak.

BUT look at the better sound room...

A 30x40x9 room is huge. The numbers aren't real good. Have to do a lot of treatment. Sound like an echo chamber, ay?

14x25 is better. Still kinda narrow and a tad to long. If you bass trapped 3 foot from the front wall, Heavy Heavy curtains will work too. then moved the speakers about midway (forward) in the 22 feet that were left.

Seated position (about 8-12 feet from rear wall) almost between the speakers. 2-4 feet from the side walls. You should be able to see the front baffle facing forward (no toe-in), with a head turn.  Then move them toward the front wall. Once there (about half way). They just go away, the speakers disappear.

Then the toe-in, camber (optional) and caster. Just like aligning an 18 wheeler analog style from the 5th wheel position (not the driver's seat).  With string, a measuring tape, and some KNOWN heights.  Takes about a day after a few measurements.. Takes about 20 min for the speaker to settle, after each move.

The only thing better is open back or Ampa Style. Can get pretty big
then...Not trapping and treating all the unwanted noise..Timing, is the only real issue for me. Getting it to arrive at the seated position at the right time..No back or side walls.. things clean up pretty nice.. High back convex wicker chairs work the best, that all the rear wall you need.

Could work in your new room also... The chair... Good wicker has a neet sound... I been using a mimosa tree to break up the HF crap in the back yard... With a wicker chair.. yup yup...

Rooms with dimensions exact multiples of each other are worse. 12x12x12 would be a horror show. 16x24x8 would not be great either.
This is where active room controls play his most important part....The passive way are sometimes enough  but in this case the active way is essential i know because my room is roughly in this case....8 by 8 by 12.... :)

Active controls: various kind of resonators of different size, helmholtz bottles, schumann generators modified...
At one point I had 2 pairs of the same speakers. One set up in the very large, lively, and open ceiling living room. The other in my carpeted and acoustically treated listening room. Yes the electronics were different, but nowhere near enough to account for the vastly different sound. The difference wasn't quite so huge if you compared from the sweet spot but even there it was obvious.

So yes the room makes a dramatic difference. Even how and where the speakers and chair are placed makes a huge difference.

In terms of bass, rooms create standing waves at different frequencies. Rooms with dimensions exact multiples of each other are worse. 12x12x12 would be a horror show. 16x24x8 would not be great either.

Basically everything about the room matters. 
speakers+room+ears are only one not 3 elements.....

This is call the acoustical embeddings of an audio system and must be passively treated(materials) and actively controlled....

The 2 other embeddings are the mechanical resonant dimension...

And the electrical grid of the house....

These simple things must be said because they are lost in translation.... Audio is not only linked to electronic design mainly, but to these 3 embeddings first....