Anyone ever try this?
 

While replacing my furnace filter I got to thinking. It's a 20x25x5 box that is mostly open on its flat sides. Temporarily until I get something better I thought I might be able to use these for room treatment. The interior of the filter is basically accordion-shaped pleated paper with a fine wire mesh supporting underneath. I think as they are they could function as diffusors. If I were to fill the interiors and cover them with fabric I think they could function for absorption. Something I have on hand is plenty of styrofoam peanuts and plastic netting that people use in their gardens. It wouldn't cost me anything to experiment so I think I'll give it a go. Do you guys think the styrofoam peanuts are a bad idea? Thinking all of the air pockets between them might create an absorbing condition. All advice appreciated

FWIW, neither will function as room treatments in any context. It was however a great idea. :)

Kind of akin to "The operation was a success but the patient died?" At least it would have been a no cost failure, except for the time wasted that I could have been doing something productive ��

Audio diffusers are actually complex and expensive for the same reason.

If you are looking for a 'less expensive' alternative to the real thing, about 75% of rooms at the most recent Capital Audiofest used some sort of 'egg-crate' foam 3-4" thick at the 1st reflection point and in corners behind the speakers. Ugly would be the first thought that comes to mind. But, the proof being in the pudding, many of the rooms using them provided excellent sound.

I'll bet they'd do something to the sound. Whether you'd like it or not, that's another question. Since it's free, if you don't mind the time I'd try it and find out if you hear anything interesting, good or bad. I doubt there will be much, if any bass absorption. But there may be a mixture of high frequency absorption and scattering. I did an experiment years ago, hanging strips made of office paper sheets - about 5 sheets thick - all over my ceiling. That had a very nice effect on my room's sound, but besides looking odd I deemed it a fire hazard.