# Density and Coating



## MysticDan (Nov 13, 2011)

Hi everyone,
I'm having a few problems before building the basstraps.
The project that I know uses 3 layers of glass wool 50mm thick and with a density of 45kg / m³, plus a layer of 25mm rock wool with density of 60kg / m³.

I have two questions.
1) To have available glasswool 40kg / m³ and 60kg / m³.
What would be the best option?

If I increase the thickness by using more layers of glass or rock wool, improve the efficiency of low frequencies?


Coating->
Most DIY projects that I see the face of the absorber brings is without fabric. This means that wool is exposed.
I could seal with tissue back too? I read that wool loose powder that irritates the skin and itches.
Anyone know about this?

Thanks in advance to all :bigsmile:


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## bpape (Sep 14, 2006)

The thicker you go, the less density you need. The lighter material will actually work better from about 6" and thicker and cost you less money. For the covering, just use something very light and non-reflective unless you want to deliberately limit upper mid and high frequency absorption. Kind of depends on what else is in the room and where these are going and what the room will be used for.

Bryan


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## MysticDan (Nov 13, 2011)

i'm appreciate bpape,
but which option would I go?
glasswool 40kg / m³ or 60kg / m³?
Thanks


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## bpape (Sep 14, 2006)

The 40kg will be fine.

Bryan


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## MysticDan (Nov 13, 2011)

thanks dude 
look what I was talking about.
http://i19.photobucket.com/albums/b176/nurhadi/Finniss%% 20Theatre 20Construction/Panel5.jpg
This photo was taken from the Topic "Making Some New Acoustic Panels"

why I do not use the fabric on the backside of the absorber? 
the part that faces to the wall or to the ceiling also reflect high frequencies?


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## bpape (Sep 14, 2006)

Something is wrong with the link but don't worry about it. You can use cloth on the back if you want but just don't make a full hard back so you can space it out or straddle it effectively.

Bryan


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## MysticDan (Nov 13, 2011)

Thanks bryan.
So I just cloth the front first and then cloth the back with another fabric?
Sorry for my bad english, i just missing something in "so you can space it out or straddle it effectively"


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## bpape (Sep 14, 2006)

Correct on the fabric. 

For the back, I'm just saying not to use a hard back like plywood or MDF. We want to have the flexibility to space the panels off of the wall or put them diagonally across a corner. If you have a hard back, those things no longer give you a benefit.


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## Owen Bartley (Oct 18, 2006)

bpape said:


> The thicker you go, the less density you need. The lighter material will actually work better from about 6" and thicker


Bryan, just a thought on this... in the case of a pretty standard corner bass trap (say 17 x 17 x 24, which I think gives a depth of about 12") would it be better to use "slices" of OC703 throughout like in the usual superchunk corner traps I see, or to face the trap with OC703 and fill the back with the regular soft fiberglass?

Its probably tough to generalize, without a specific frequency to target, but let's look at it as the first step to bass control for a room.


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## bpape (Sep 14, 2006)

Probably easier and about the same cost just to do slices. By the time you do 4" of 703 and bevel the edges to get them to sit nice in the corner at an angle, then buy the fluffy stuff, cost is likely about the same. I think the slices are easier to do.

Bryan


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## ALMFamily (Oct 19, 2011)

bpape said:


> Probably easier and about the same cost just to do slices. By the time you do 4" of 703 and bevel the edges to get them to sit nice in the corner at an angle, then buy the fluffy stuff, cost is likely about the same. I think the slices are easier to do.
> 
> Bryan


Much easier IMO as well - it took me about 4 hours to do my front traps.


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## dguarnaccia (Jul 17, 2008)

For what it's worth, I went to HD and bought R39, which is 12" thickness pink stuff and created the wedges from that. I did them in 24x24x34 format for added depth, but it's pretty much the same. I did notice that the weight of all the fiberglass did tend to compress the stuff on the bottom, so you'll use more than you think, but it was pretty economical. I package did one corner for the most part and they cost me around 50 bucks each. 

Here is a shot of it from my build:


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## Owen Bartley (Oct 18, 2006)

Thanks guys, great info.


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## MysticDan (Nov 13, 2011)

Bryan, THanks for all helps. I was going to build panels with about 6" thick. 
But as my room is small, and I need to treat the low frequencies, I think it could go deeper. I thought about doing a 8 "or 12". So if i choose one of this, what is the density that could use as it can be lower than the rigid Paines? (rigid = 40kg/m3 or more?) (fluffy = 10kg/m3 maybe?)

One more question, I saw that some people build the first reflection Paines thinner. (4 "or less.) If I build them thicker and installs them at points of reflection will also help lower the frequencies right?

Regards.


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