how can I make the back wall transparent?

Wow. This is a great thread. I am going to try the rolls of, sshh, tp. It will be less expensive than real traps or others and I can change the design anytime I want. Wow!! I can paint them the rainbow colors if I want to. Oh now I am getting excited!! Ok now, I have an important question before I go on this journey of no return. How high can I stack them? And does anybody have any specs or ideas on what to expect its effect on the sound will be? And what brand should I use? Yes I will be using brand new rolls if you were wondering.

Charmin! and for best effect hang them on a rope - multi coloured will be high on WAF scale - you can even hang some on the wife/girlfriend and tell them its the latest fashion :-)

I like the hang on the rope idea. Easier to borrow some if you run out in the you know---. I should of guessed 'Charmin' because that is the way I want my system to sound. And by the way that little 'Charmin' doll should try out for American Idol I think. Good one Willie.

In the early 70's my band rented a house and nailed mattresses (back when you could get mattresses cheap at Goodwill) to plywood sheets on the basement walls and ceiling...possibly the ugliest good idea ever. (insert "Yo Mama" joke here).

there are still plenty of cheap brand new mattresses. they're not too good for your bed, but definitely great for acoustic traps.
if you're purchaseing used from Goodwill or from someone, you're under risk of bringing bed bugs to your home.