Many of the lessons learned that I have had over the years are about the room. I started putting in dedicated outlets in 1989. I started using bass traps in the early 90s. One thing I learned back then is that a little damping is good but too much is bad. I was doing work back then in a hemianechoic chamber as an engineer analyzing noise in cars. So I tried adding more and more damping material to my purpose built listening room until I killed the sound. Room reflections are a necessary part of good stereo. Too many reflections is bad but so are too few. Isn’t that what makes this hobby so fun? Some computer programs exist to calculate how much and where to put sound absorption materials. But the best instrument you have is the ears on your head and with some effort and patience good results can be achieved using simpler tools like sound meters and your head.
Corner bass traps are a must. One of the crazy things is when the bass sounds better in the back of the room versus in your listening spot. I found that is caused by the speakers being too far away from the front wall. I always liked the speakers out away from the walls to get a bigger, more airy soundstage but the tradeoff is bass response. Typically a compromise for most speakers.
A stiff floor improves the sound and imaging. Years ago I had the stereo in a large, carpeted living room over a basement. I tore out the carpet and put in a 7/8" Hickory hardwood floor. I was amazed at the improvement in the sound. The only catch is, now a wool rug is needed to tone down the highs because the wood has no damping. But now the room can be tuned by finding that right size and thickness wool rug. Don’t use polyester- everything will sound like digital. :) No really, wool is the ideal material.
Some dispersion materials are needed on the side walls but where to put the panels. The trick is to use a mirror. Have someone slide the mirror on the side wall while sitting in your listening position. When you can see the tweeters, that’s where the dispersion panels should go. Not too much. Season to taste as they say. You can do the same for the ceiling if you want.
Windows are bad news, some treatments are a must to tone down the reflections. The same goes for the front wall. I find a few dispersion panels on the front wall are good but too many can be bad.
One last thing, the Wilson Sasha DAW speakers are my first ever ported speaker in my stereo system. Ported speakers are much more picky about placement than sealed enclosures. The distance from the walls for ported speakers is critical down to 1/8". That’s right. It takes patience to dial things in. What I found is the bass response can have peaks at certain frequencies until the speakers are in that just perfect position from the front wall and side walls. Ported speakers use the room to help generate those low notes. What is cool, I found is once dialed in the bass sounds the same anywhere I stand in the room. I never achieved that with my sealed baffle speakers.