Differences in fiberglass insulation

[mbaylor]

I am going to build some treatments inspired by Jon Risch.

They are going to consist of 4ft x 2ft x 2" wooden frames filled with kraft faced insulation. This will then be wrapped in polyester batting and then finally burlap.

My question is, what are the differences in sound absorption when it comes to different types of roll insulation, like r-11, r-19, r-25 etc.

What is the best to use for low frequency absorption? high frequency absorption?

Thanks in advance.

Mark

 

[kiwiaudionut]

I don't know about the absorption properties of standard household insulation, but good luck getting R25 into a 2" space!
The R value denotes its insulating ability, but it is thicker as you go up the scale to enable that.
Also, the "facing" is typically a paper sheet - Man are you sure about this ?

 

[mbaylor]

I have not set the plans 100% in stone.

I am open to suggestions for DIY panels to keep costs to a minimum. Thanks for the reply.

 

[Glenn Kuras]

When it comes to rolled fiberglass (what you are talking about) you need to stuff the full corner for bass trapping. So it has to be REALLLLLLLLLLLLLLLLLY thick to work.
For the side wall panels you can use rolled fiberglass, but you are going to have to get the paper off the front of it. That will reflect high end which you don't want for early reflection panels. Also it is best to make that thick also.

Maybe look into getting something like OC 703, OC 705 or Mineral wool. These are much more rigid and you can make a bass trap at 4" straddle the corner or a early reflection panel 2".

Glenn

 

[mbaylor]

Thanks for the response. Generally where can these materials be found locally? I don't recall seeing mineral fiber anywhere (in home stores).

 

[Glenn Kuras]

You can try spi http://www.spi-co.com/ or there are places online to buy it. Note that shipping of it is reallllllly expensive so it is best to get local if your building yourself.

Glenn

 

[bpape]

I'm just still trying to figure out the design goal of a 2" panel that has a facing on it.

2" isn't thick enough for bass control but is fine for reflection control. However, for reflection duties, you wouldn't want a facing on it or it will reflect the upper mids and highs.

The 2 things just seem to be at cross purposes to me. Now, if it was a 4 or 6" thick with a facing, that'd be proper.

As for the difference in the different kinds, it's all a matter of how you use it. If you take an R-30 and compress it into a 4" thick panel, you'll have the equivalent density of about 3/4 of OC703. Using R-19 (half as thick) will end up with less density.

If you use them as their full thickness but less dense, then the thicker will reach deeper.

Bryan

 

[mbaylor]

I was going to staple the insulation to the frame from the rear using the facing.

I also had no real intention of bass control with these panels, but was curious what the properties might be. Proper bass control will come along later.

So the layers from front to back would be burlap, batting, non-faced side of insulation, kraft paper, batting, and finally burlap on the opposite side.

I am still trying to understand the concepts of sound absorption, but how does facing behind the insulation reflect sound? Does it come into the insulation, hit the paper, and bounce back out?

 

[bpape]

In that arrangemen, there should be little to no impact. Anything that it would reflect would most likely have already been absorbed on the way in.

The only thing it would change would be if you spaced the panel off the wall. In that case, you'd not get any 'extra' absorbtion by sound coming in from the back side in the mids and highs. That would still extend the bottom end absorbtion though.

Bryan

 

[mbaylor]

Thank you for all of your help!

I am going to try and find some mineral wool local and build them that way.

Would you say 4" mineral wool in panels for the corners at an angle and 2" for the side, front, and back walls.

I assume the most important places to treat are early reflection points?

 

[Glenn Kuras]

Thank you for all of your help!

I am going to try and find some mineral wool local and build them that way.

Would you say 4" mineral wool in panels for the corners at an angle and 2" for the side, front, and back walls.

I assume the most important places to treat are early reflection points?

Yes to all. Here is a layout with our product, but you can go by this to help you with treatment ideas.

Good luck and let us all know how it turns out!!

Glenn

 

[mbaylor]

Thanks a million for your help!