Most rooms don’t need acoustical treatment.

I am by nature a skeptic. And many things (IMHO) in the audiophile world are indeed snake oil.
That said, in my 13x16 living room, couch chairs and all… I bought two 24x24 box difusor’s and sat them on top of a chair back, which sits between my speakers, no doubt about it, hands down, immediately beyond a reasonable doubt completely changed the room dynamics for the BETTER. The sound stage suddenly had depth and basically a larger presence.
I was truly amazed.

my rooms have furniture and clutter.  These rooms don’t really have a need for treatment.  It’s snake oil, voodoo science.  

If your furniture addresses all the acoustical issues in your room, yes. However, that is somewhat doubtful. Many home theatre setup have auto IQ systems precisely because very few rooms are acoustically neutral. 

I'm normally a person that scoffs at measuring equipment as my ears almost always proves the measurements to be of no value, but acoustics is an area where measurements by and large correspond with our hearing. 

If you take a simple sound pressure meter (i.e. decibel meter), you can feed different frequencies into your system and measure the sound pressure (volume). You will see swing of 20db, 30db, sometimes even more across the audible frequency range, and these swing will be differ in different areas in your room. 

Addressing some very simple things, like the first reflection point will dramatically increase the focus and sound staging of your sound system. The changes are not subtle. You'll be bowled over by just how good your system really sounds.

Ps. A little stone or clock in the corner of the room isn't going to do it. Have a look at what the pro audio guys do. 

@deep_333

It is kinda funny when guys spend thousands of dollars on power cables and such, but refuse to spend a dime on the room.

If we were smart, we’d spend 50% of our budget on our rooms. But we aren’t smart (myself included)

Even though I know it works as I have experience of it, I loath to spend $500 on diffusers but will happily spend $2,000 on power cables. 😂🤣

Not sure I agree with you there- that it doesn't matter.  While its true those of us without direct studio or live music experience have an extreme challenge knowing for certain what is sonically  "correct", I think the goal of many audiophiles is a piano needs to sound like a piano.  Many of us have heard a real ones so not the impossible target. 

Some room treatments are ill advised and don't help, but it is true that the speaker and room are a bonded pair.  One influences the other in more ways than most understand including most manufacturers.  The science of acoustics and sound is not simple, easy to explain or linear.  Just trying to explain a decibel gives most us a brain freeze, and the entire subject of how a the environment influences a speaker can be a lifetime of study.  It truly is a rubik's cube.