Ok so I wanted to post this because I think that some people out there may find it useful. I recently purchased some energy desktop speakers and a dayton audio desktop amplifier, to be used as computer speakers. I had a heck of a time figuring out how to get the speakers to sound good, situated on a desktop, and near the back wall. I was getting bass boom, and unattractive reflections because of where I was placing the speakers. Now I know that placing speakers on a large hard surface, near a back wall is not ideal, but this is where I wanted my speakers to be. After searching for tips online, I sort of discovered my own solution. Using FoamOnline.com I was able to purchase blocks of foam and isolate my speakers from the wall, window, and desk pretty well. They sound much better, almost like they are on a speaker stand a few feet from the wall.
So as you can see in the images I made an L shape with 2 pieces of foam. With shipping the foam cost around $20. You can also see that I have my speakers on some audioengine desktop speaker stands, that give the speakers some tilt. I had already purchased these to try to get the speakers to sound better, but they didn't help in my situation. Since I already had these I did not buy a triangular piece of foam, but you could do that if you want some tilt to your speakers as well. I ordered the supreem foam, and just used some foam friendly glue to hold everything together. I used 2 inch thick foam behind the speakers, because I heard that is a good thickness to help with base frequencies; and I used 5 inches under the speakers, just to push them up off the desk a ways.
I think these look pretty good, but you may need to get the wife approval factor first
I found that this really helped the sound of my speakers in this particular arrangement. I was able to keep the speakers on the desktop and push them up close to the back wall, which is what I wanted for my computer speakers.
So if you find yourself in a similar situation as me, I hope this helps. I spent a lot of time surfing the web and as far as I can tell there really isn't a better way to be able to place nice desktop speakers in tight situations like this without affecting sound quality. This idea helped me to get it to work great. Feel free to ask questions, or let me know how this goes for you if you try it.