Room Treatments - Where to learn more?

Can you suggest some links to websites with practical advice on how to improve the acoustic properties of stereo listening rooms?

I'm about to do a major upgrade to my mediocre system. After reading Robert Harley's "High End Audio" Chapter 4, I gather that room treatment should be near the top of the list for areas to work on.

This is probably especially true since my room has so many hard surfaces.
Picture of my Room
Suggestions on practical ways to improve the sound of my room would be welcome. My thought for the first step is: install drapes on all those windows. The room size is 21 x 22 x 8 feet with 3 open extensions into other spaces.

What else would you suggest for me?
What has worked for you?
Tobias suggestions are right on and two of four suggestions I would make.

At The Home Entertainment Show in NYC this year, I noticed that the rooms treated with Real Traps sounded noticeable better than other rooms. I spoke with Ethan Winer, the proprietor of Real Traps, who is very knowledgeable and helpful. I purchased some of his products and they have produced a phenomenal improvement in the sound in my room.

Also, "The Master Handbook of Acoustics," by F. Alton Everest, is the bible.
Acoustics circle

Realtraps, Ethan's articles

Ethan Winer: Acoustics Forum

gik acoustics

What kind of bass trap do I need? BBC/DIY

More DIY


Some links that I had lying around. There are more forums and DIY sites, but most of the forums have the same crew of experts.

I'm playing with fiberglas/diy panels, I'm treating a bad (tight) space and experimenting so that I can move on to a family space. It's well worth the effort, unfortunately I am finding the ceiling makes a really big difference in beautiful tone. Simple treatment (corners walls and ceiling err... not simple, sorry) will reward you in great bass (the holy grail).

Even my ridiculously simple attempts have yielded great results. I started off unintentionally deadening the area and learned about what worked and what took the energy away.

Otherwise take a look at some of the more respected names, it's worth the money not to have to build, and they do a better job that glued fiberglass and wood

There is some basic info here
I used Auralex foam products a dedicated room but they may not fit your decor. I wouldn't use them in a living area.
Thanks for your suggestion of "The Master Handbook of Acoustics," by F. Alton Everest, 3rd edition. I just ordered a copy on Amazon for $24. That seems dirt cheap when I gather that many audiophiles don't blink at spending hundreds of dollars on a power cord.

Link to the book on Amazon
Also try Robert Harley's The Complete Guide to High-End Audio......has come to be known as the "Bible" for high-end audio enthusiasts.
Excellent reading. A++++++++
Try it, you won't regret it !!!
Here's some links I had from another post a while back:

This one is for a home theater, but his approach is fairly typical.

This next one is a great resource, scroll down to the bottom for research links:

Here's a DIY approach to bass traps:

Ethan Winer is a great resource (he hangs out over at the Rives forum on AA). He sells "Real Traps", but also tries to educate people...never met the guy, but he looks to be an interesting fellow:

Here's a I guess that he wrote that can get you started:

And his home page:
Thanks, the link to Ethan Winer's PDF was excellent. It is called "Acoustic Treatment and Design for Recording Studios and Listening Rooms" and is packed with good information.

However, I'm still looking forward to reading the "Master Handbook of Acoustics" 3rd edition which is on its way to me now from

Today as a first step, I hung a Pendleton Wool Blankets on the back wall of my listening room. It may not be as effective as Owens-Corning 703 Rigid Fiberglass, but it does look nice.