Most rooms don’t need acoustical treatment.

There are two basic issues in rooms: absorption and reflection.

Yes. And timing. Three basic issues. And the relationship of direct to indirect sound. Okay four basic issues. Well, and the timing and relative volume of reflected sounds. Dang alright five basic... what? Aww come on, you got to be kidding me! Construction of ceiling, walls, and floor. But that's the last basic issue! No kidding! I am drawing the line at 6! Noise? What do you mean, noise coming in? Or noise going out?! Crap! No freaking way. Plug up the outlets, seal up the door, whatever you do make believe we didn't just go to 7 basic issues.....

There are two basic issues in rooms: absorption and reflection.

A room is not a passive set of walls where we put reflecting or absorbing surfaces sorry... Save for sellers of acoustics panels publicity...You even forgot the diffusive surfaces...

A room is a living animal resembling to a violin when a musician plays it...Any room speak his own language translated for human ears  in a universal meaning by acoustic....

I cannot go further because i will type too much words.... Some people hate me already for my long posts and too numerous posts.... 😁

My metaphor is so right and good i will stay with it at the risk of being completely not understood...

I go back to music anyway....


Chopin Mazurkas by Jakob Flier....

Setting up a system in a nearly empty room, once you have studied and obtained a theoretical grasp of acoustics, is a great way to learn the science and the art.  And you don't need to spend a lot of money to experiment ..... piles of boxes, wool and cotton blankets, large pieces of foam can all be used for the experimentation.  Once you've figured out how to optimize to that three-dimensional image we all strive for along with natural ambiance, if the room is to be a listening room, then make the dollar committment.  And you won't waste any, so you'll know exactly what you need.

Once you've got those experiences under your belt, in my experience, it is fairly easy to arrange a living room or family room so that it works acoustically.  If you've moved a couple of times, you can even get to the point of visualizing the acoustics as you lay out the room patterns, and won't have to change much once you have things in place.  Setting up in multiple rooms over time also has the advantage of teaching you what imperfections you can tolerate and which you can't.  Ah, it's good to be an old geezer! :-)

Tooo damn complicated.  Brilliance is the ability to paint complex things in simple terms.  Very few succeed. 
And then enter all the variations of recording qualities that endlessly frustrate.  If only 60s and 70s music were produced presently.  So we fall back and listen to just a few names that bring us comfort over and over again.

Right. Well said. There are simply too many notes. 

https://www.youtube.com/watch?v=Vci4wM6jDDM