Diffusors vs. absorbers room treatment

Look here for some good info and DIY recipes:

http://www.geocities.com/jonrisch/a.htm

Here's some bedtime reading:

http://www.decware.com/room.htm

I'm using a TacT RCS 2.0 in my 10' X 17' X 8' room with
excellent results, and minimal diffusion (three
Room Lens clones I built). The TacT allows precise
diagnosis and minimizing of the room nodes, particularly
bass nodes) which are the most harmful to sound quality.
It made a remarkable improvement in my less-than-ideal
sound room.

I agree with the above post as far as placement of absorbers. I've got wall treatments on the sides, rear wall and on the ceiling of my listening room. Many experts will say that diffusors should be placed in the rear of the room and are used to expand your room as they spread out the sound. You really have to experiment to see what suits your room the best. I am using Argent Room Lens clones and CD racks at the rear corners of my room to act as diffusors. Moving the room lenses as little as a couple of inches makes a difference in your soundstage. I've placed the room lenses at the mirror image points to the sides of my speakers and behind each left and right speaker. Both absorbers and lenses are DIY following John Risch's on-line instuctions. You can see pics of my room if you look at my "system".

I like the link Psychicanimal posted. I loved the comment--"with all the complexities of room acoustics it's no wonder I spent my money on a power cord" (or something like that). It is so true! I read this original posting earlier and wanted to point out the complexities--but the problem with that is that it just makes people avoid the room issue altogether, which is the worst thing you can do. We offer services that engineer the entire room without having to go the trial and error route. We also do not sell acoustical treatment--thus there is no incentive for us to tell people to buy something they don't need--in fact most of our designs are more like the John Rische pages (being true designs that can be built), but sometimes people want things that can be simply bought. That being said, we also understand that not everyone can or is willing to pay for a service. Let's face it--you don't get a fancy item in a fancy box--it's all designs. But still our goal is the room. We firmly believe that the room is so often ignored in favor of power cords and other things that have such a small effect on the sound relative to a well designed room or acoustical treatment of room.

Now I'll get off my biased soap box and say for the DIY people--don't be afraid to work on it and try things. How many cables have you tried? How many components? Think of how many things you've done to your system that didn't work out? Guess what--when you get into room acoustics--the same thing will happen. You will try some things and they won't work--but you'll try some other things and they will. Keep in mind--like system synergy the same is true for room acoustics. If you change one thing--it affects others and so sometimes the path to the best sound isn't that clear. For some people they want to get to the end point quickly and relatively painlessly--or they are willing to invest substantially in construction costs in building a dedicated listening rooms. In either of these cases it's crazy to try the trial and error process--you will be frustrated, confused, and possibly out a lot of money without too much to show for it. However, if you are the audiophile that likes to tinker, tweak, try things and see for yourself what the results are--by all means--do it! Some of these links above are great. There are also some books by Alton Everest (Master Handbook of Acoustics and Studio on a budget) that are very good. Most acoustical treatments can be built yourself for little money if you are reasonably handy. The real trick is knowing what to use, where and how much, so that everything works together. For example, every material has a particular bandwidth for both absorption and diffusion. You need to know these to calculate how the room will react with a certain amount of certain material. Some of these calculations are complex--some are very basic. But there are some basic principles that almost always work. Have some absorption on the first reflection points (owens corning 703 wrapped fiber board works well and has a better bandwidth than most foam products), have diffusion behind the listener. If everyone just started there it would be a huge improvement over doing nothing. Then over time, read more, learn more, and listen more. You can hear the difference of every type of absorber and diffusor and just by moving these throughout the room you will learn their effects. This is not a short process--but can be a fun one--if you like doing things like this.

Obviously, we would love to design the listening room, but if we can't we want to encourage and hopefully provide some useful tips on how the DIYer might improve their room. We do have a small tutorial (although the books are much more in depth and highly recommended) at the listening room at http://www.rivesaudio.com. Hope it is helpful.