Go to the resource section on our site. It has lots of DIY links for acoustical treatment devices. It also has links to many articles on the web and books that may help you as well. The most important aspect is getting the size right--size matters, but it's the ratios of dimensions and what you do within that space that really counts.
Here's a link to our resources:
Rives Audio Resources
Here's a link to our resources:
Rives Audio Resources