Room Treaments - Where To Begin...

I'm constantly amazed that audiophiles can go on at length about VTA, upsampling, damping factor etc. but when it comes to the most important component, the room, they have little or no understanding. This is forgivable to an extent. Without having heard the enormous improvement attention to acoustics brings to the party it is difficult to conceptualise the transformative result.

All rooms need treatment, without exception. Even the Royal Albert Hall required  some monster upside down 'mushrooms' to kill excessive echo.

The second post you received from member @dill provided you with lots of good info and there is tons more. Obtaining your advice from those links is preferable to getting conflicting opinions from ill informed posters here on the 'gon.

Once you have gained some understanding, which you should relish with glee because this is the only way you will ever get to hear your system truly perform, you will soon realise that guesswork does not enter into the requirements of treatment.

You will understand about wavelengths , how to calculate and how to deal with them. You will also learn that a rug, drapes or wall hangings do very little because they only provide narrow-band absorption. Now I expect someone to counter with 'I just placed a rug between the speakers and it made a huge difference" Well yes of course there will be a small improvement and the comment simply comes from them never having heard what a carefully sorted room sounds like.

The biggest thing happens down low in the Schroeder frequency range where bass energy combines, sometimes creating peaks and sometimes nulls. Bear in mind that a full null means zero sound. I repeat, when there is a null there is no sound, zilch, nada. It's MIA and no, no DSP or equalisation can bring it back. Even a partial null, say 15dB below average, could not be corrected because your amp is not powerful enough and the speaker voice coil would instantly fry.

Above the Schroeder frequency, average about 250Hz you have a reverberant field which can be addressed with diffusers and absorbers. This is important: the smaller the room, the more absorption is needed. The bigger the room, the more diffusion is needed. In practice the average size living room need both.

My direct advice after reading the material @dill provided is to read even more and then buy a suitable mic. for less than $100 and download a free program like REW and get started. Even if you get the professionals in you will at least be able to measure the before and after results and so avoid the possibility of being oversupplied which has happened to a friend of mine when he left it all up to GIK.

Imagine now hearing all the missing details in the bass and the fact that unless you act appropriately things will not change. If you want to go all the way then look into a multi-sub addition which will smooth out the lows even more. Can this bass problem be sorted with multi subs only?  Well yes the extra subs will smooth the room nodes but you still have the issue of overly long decay across the full spectrum.  Looking at this another way:  installing multi-subs will smooth out the bass nodes and the addition of bass traps will reduce the long decay. Win win. Your ability to measure T60 yourself will get you to head of the class.

Have fun.

Ethan Winer explains it in detail in Part 4 of his book, The Audio Expert. Well worth the read before haphazardly throwing stuff on the walls. His realtraps.com site also has some good starter articles on the subject.

Yes, Ethan Winer is a good call. His YouTube videos are interesting and informative. 

I forgot to mention, there is also the forum 'gearspace' formerly known as gearslutz, which has a whole section on acoustics with articles on building stuff yourself and on measuring, which is easier than you think even though I don't know what you think, I think. There is a much larger community of experienced guys and well worth a visit.

@lemonhaze such a pity you haven't posted a system page.

Like millercarbon, the best sorted listening room I've sat in and heard music played on a system would be Mike Levine's. In your opinion what percentage of system budget would you expect for a room to come up to the relative performance of the stereo playing in it?

I've been reading where room proportions may matter as much and in some cases even more than just distances between boundaries in a listening room. And if you didn't have the budget to do an entire room all at once, where would you likely start?

Is your stereo in a dedicated listening room, or, living, shared space? 

Sometimes, you must compromise and are limited to what and where you can place things.

Another good all around audio book, which mentions acoustics and treatments is Robert Harleys book. 

You are on the right track!