# Room treatment



## archaicworld (Jan 25, 2013)

I am going to be treating my ht room with Roxul AFB and I was wondering of using cardboard as a backer would ruin the acoustic properties? The plan was to use 2" panels mounted 2" from the walls and ceiling and doubling up on the panels for all the corners where three surfaces meet. If the cardboard is fine as a backer, would it even be worth mounting 2" from the wall, or would the cardboard act just as the wall would? The reason I'm considering cardboard is because I can get as many 4'x4'x0.5" cardboard pallets with 2" legs as I want from work.


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## Tonto (Jun 30, 2007)

So the cardboard is 1/2" thick, thats some heavy duty cardboard. I think that would definatly reflect high frequencies so I don't recommend it. Wrap them in muslin, you can buy it from fabric stores & it's not expensive. You could cut the palets into 4" strips and build the box's to hold the Roxul. That would cut the expense of lumber. Is the cardboard solid or corrugated?


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## archaicworld (Jan 25, 2013)

Corrugated with chambers facing front to back so it's 2 pieces of paper at .005" thick separated by 0.5" of air. Like placing two pieces of paper at both ends of a tube. They're lightweight and very rigid, I've got 300sqft of a something we call milt cloth that's basically a nylon and Kevlar woven speaker cloth. I was thinking of using a fire resistant adhesive to back the mineral wool with the cardboard and then wrap and staple the cloth. I could use the cardboard to build a frame but I was thinking it would be easier and stronger to use it as a backer. But if that doesn't work I might very well just frame it, if I can get the mineral wool to stand up inside the frames, it's pretty floppy stuff.


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## Kal Rubinson (Aug 3, 2006)

archaicworld said:


> I am going to be treating my ht room with Roxul AFB and I was wondering of using cardboard as a backer would ruin the acoustic properties? The plan was to use 2" panels mounted 2" from the walls and ceiling and doubling up on the panels for all the corners where three surfaces meet. If the cardboard is fine as a backer, would it even be worth mounting 2" from the wall, or would the cardboard act just as the wall would? The reason I'm considering cardboard is because I can get as many 4'x4'x0.5" cardboard pallets with 2" legs as I want from work.


A solid reflective backing, like that cardboard, negate much of any advantage for spacing the Roxul from the wall. Might just as well put it on the wall if you include the backing.


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## archaicworld (Jan 25, 2013)

Ok, I figured it might negate the spacing. My question now is; what exactly does the spacing do for the acoustics? Is it really necessary?


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## Tonto (Jun 30, 2007)

You have to picture the waveform of the sound frequency. After it traverses the Roxul, if against a boundry, it returns with a matching amplitude. By adding a space, the waveform has a distance to change, thereby increasing absorbtion. That is why I did not recommend using the cardboard.


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## archaicworld (Jan 25, 2013)

I see, would it adversely affect the Ruxul if I used a 1" piece of the cardboard as a brace to hold the Ruxul up inside a frame?


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## Tonto (Jun 30, 2007)

1" wont have much effect, but wrapping it in speaker cloth, front & back, would also work. This will also help keep fibers from drifting/falling off/out.


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## archaicworld (Jan 25, 2013)

Yeah, they'll be wrapped up nice and tight. Thanks for the help.


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## Kal Rubinson (Aug 3, 2006)

archaicworld said:


> I see, would it adversely affect the Ruxul if I used a 1" piece of the cardboard as a brace to hold the Ruxul up inside a frame?


Not much but backing with any stiffness or lack of porosity will have an effect. Frame is probably OK but I prefer using inherently stiffer material that does not require any support other than the covering fabric.


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## archaicworld (Jan 25, 2013)

Kal Rubinson said:


> Not much but backing with any stiffness or lack of porosity will have an effect. Frame is probably OK but I prefer using inherently stiffer material that does not require any support other than the covering fabric.


True, Corning 703 would be my first choice, but at easily twice the price of mineral wool I can't justify the price for such a small gain. Someday when I've got a room really worth it's salt, I'll save and spend the money to do it right, but for the temporary I'll settle for second best.


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