I´ve just turned one of my rooms into a mastering room this year, which simply means that I´ve done all the treatment that was needed. Don´t be worried! You can fix any problem that occurs. There are lots of basics that needs to be known but there are some good recourses as well. The problem whith those recourses.....they all follow different theories which leads to different constructions. So please don´t get confused. There are many ways how you can treat a room. The question is, are you treating an already existing room or are you building that room from scratch. The smaller the room the more compatible you are to a living room, in reference to early reflections and bass response. So a listening room (especially for mastering) doesn´t have to be necessarily large as many people think. In fact if you manage to control the pressure in the low freq spectrum, there are some benefits over large listening rooms, because the early reflections are shorter than the ones in the sound source you are listening to. I can give you some internet links, but whatever you do should really depend on what you are hearing in that room. You need to walk around in that room and find out what you hear/measure at the corners, walls and ceiling...
http://www.saecollege.de/reference_material/index.html
http://www.saecollege.de/reference_mate ... 0Chart.htm
http://www.roister.com/eng/comp-gen.htm
http://www.tubetrap.com/tt.htm
http://ic.net/~jtgale/diy2.htm
http://www.silentsource.com/diffusors.html
http://www.primacoustic.com/
All those links above are just for basic understanding.......
Personally, I´m no big fan of Auralex´s foam products, although they are much better than ordinary foam....
The best bass absorber will always be the "tube trap". But you will barely find information in the net because ASC has got the monopoly on them. And the theory behind the tube trap is really hard to find in the net. They were invented 1947 and most information has somehow disapeared.
I´m also no big fan of SAE´s membrane absorbers, although they are the only ones that don´t absorb high freqs too much. And when placed strategically right you can minimize their deficit of causing phase problems. I´m using them myself...
An "Anechoic chamber" makes you hear what comes out of the monitors and nothing else, but the sound will suffer severe incompatibilites with the standard living room. (not suited for mastering)
But the hard part is getting rid of those problem freqs whithout loosing the liveliness of the room (that´s why I´m against foam products). Take a look at the absorption coefficient chart and you will notice that most materials do absorb high freqs but only very little bass freqs. They lead to a dead sounding room whith no emotion and enjoyment. Also changing the balance towards the problem freqs. It´s easy to make matters worse! However, the only way to make a room sound livelier again is to diffuse mid/high freqs again. Whether you place them at the back of your room, as official AES papers state, or at the front depends on how you monitors are placed and what you have done to minimize those bass freqs around your monitors.
So this is only my opinion:
You need to walk around and find out how different places in your room do sound. This is the first thing you should do! Move around and find out where those freqs do build up strongest. Ceiling and corners are always the first suspects. It´s also advisable to build such a room whith different kind of surfaces/materials, based on different theories because following only one concept will lead to a mono-"aural" sounding room based on principles that only fits the average control room standards...
-Damp the wall behind your monitors...And set up some kind of diffusion in between and/or above you monitors.
-Treat all your corners whith bass traps. Wether they are tube traps or ordinary corner traps, depends on how your bass response sounds. (Pressure=tube) (frequency=fiber)
-Everywhere where a walls meets the ceiling you need to do something... You could put some 2" thick glass-fiber all along those edges (minimum width of 30cm).
-The worst thing for me is to place monitors into side corners whith side walls minimizing the stereo-field. There is almost nothing you can do to treat that dificit.
-Avoid parallel walls as much as you can to minimize standing waves. There are three types of standing waves. (too complicated to explain now). However calculating standing waves is interesting, but the only way to react to those outcomes is to built Holmholz resonators (diffcult to built and I don´t recommend them) or if your going to build a room from scratch...
http://www.mcsquared.com/metricmodes.htm
-The ceiling shouldn´t reflect high frequencies to avoid flutter echo. Place some kind of thin curtain or whatever to the ceiling. (everything absorbs high freqs). I have even built some tube traps for the ceiling....(at my place the basses built up in the middle of the room at the ceiling).
-A part of my back wall is built anechoic, reflecting absolutely nothing, killing whatever freqs do reach the wall.
-In the middle of the backwall (behind the chair) I´ve built another tube trap... Opposed to SAE college, I think that if a room should be suited for mastering, it shouldn´t diffuse in the middle of the back wall. The sound coming out of your monitors has crossed before reaching the wall and when diffused, will lead to a worse channel separation and dynamic-range, making stereo-field localisation even more difficult.
-On the ceiling behind the chair, you can built some panel absorbers, hanging from the ceiling (similar to SAE´s, just not as large). They prevent waves in the upper part of the room from going to the sides, finally leading the sound to that anechoic places at my backwall. That again did really make a great difference towards the bass response in the corners, leading to a pressure loss in the low freq area.
-Diffusion is the last part of treating your room. Dont´get worried when the room sounds to dead before you`ve done any diffusion. Diffusers are much too expensive IMO. So here are some alternatives... You can build those diffusors yourself, because they don´t have to look like the expensive ones at silentsource...they only have to diffuse. And certain things like steel wool, wooden/aluminium shalousies, bambus carpets, moskito nets, perl chain curtains, or even some plants could do a similar job. The finer the pattern of the material, the finer the sound. The denser the material, the more high freqs and all other freqs will get diffused....
-So, do whatever is necessary based on what you hear/measure and place things strategically right. I´ve always wanted to write down this little summary. It seemed to be the right moment to me....
Regards,
Bernhard
* I can't help to dream about a separate space for a bigger studio up there. I know you guys are well experienced on lots of sound subjects and studio facilites. So If you have ANY information about walls, doors and windows desing, ceilings, wall sound treatment, please let me know. I'm preparing a special rectangular space of 27 square meters (about 250 square feet) I'll split it on the half to build a separate control room and a recording room. Any advice would be much appreciated.
check auralex, 
comments???