Well the CD rack is a diffuser but foam eggshell is an absorber. So which is it?
Anything like your staggered CD solution will work to scatter reflected sound. Anything soft and porous will work to absorb, ie convert acoustic energy to heat.
If you weren't so cheap I would recommend Owens Corning 703 as that is extremely effective, readily available, and easy to work with.
Its actually good however that you are cheap. Because the best way of saving money is spending time. Time spent listening. Trying different things. Like for starters you drape some fabric over your CD rack. Let what you hear be your guide. If you hear a difference then that will direct you to better solutions. If you hear no difference well then so much the better as then you don't need to do anything.
Anything like your staggered CD solution will work to scatter reflected sound. Anything soft and porous will work to absorb, ie convert acoustic energy to heat.
If you weren't so cheap I would recommend Owens Corning 703 as that is extremely effective, readily available, and easy to work with.
Its actually good however that you are cheap. Because the best way of saving money is spending time. Time spent listening. Trying different things. Like for starters you drape some fabric over your CD rack. Let what you hear be your guide. If you hear a difference then that will direct you to better solutions. If you hear no difference well then so much the better as then you don't need to do anything.