Of coarse the foam absorbs high frequencies, but ALL CD devices have to be EQ anyways so I just EQ in this loss. No problem.

I believe that I could model he rough walls. I know that I can model, and have done so, an absorptive wall, as well as an absorbtive internal medium. A rough wall just have a different kind of boundary condition.

You will also have to be more specific about "theres usually better ways to fix a problem such as rough frequency response than this". I am not new to waveguide design and usually know all of the techniques involved, but I am not sure what you are refering to here. If you are refering to the use of the foam, I strongly disagree that there are better ways. If there were then I would use them and not have to "invent" the better solution.