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Bedroom Studio
Old 1 week ago
  #1
Here for the gear
 

Bedroom Studio

TL;DR Due to rabid hypochondria, looking for a way to encase fibrous insulation for first reflection panels without causing unfavorable HF reflection, or a better solution

Hey guys. I'm trying to transform as much of my bedroom into a home studio as I can. During this process, I'm going to use this thread to ask for advice on any problems that I cannot find solutions to from my own research/intuition. Let me know if there is already a thread that I should use for this kind of process.

I'm now ready to start working on acoustic treatment. I'm going to talk to GIK about what I need, but I plan on doing DIY panels and need advice on construction in general. I have concerns of escaping fibers from the mineral/rockwool insulation (I'm looking at Knauf Earthwool). From scanning through the years of posts regarding this concern I know you guys are likely tired of posts asking about it, I'm sorry to bring it up again. But I'm a hypochondriac and have family members that tend to be allergic to a lot of things, and I'd rather not have this stuff getting around the house.

After a few days of looking into this issue, I'm stuck on how to handle absorption panels at the first reflection points. I wanted to encase the insulation with either super-thin plastic (which I've found differing opinions on whether or not this will fail to be adequately transparent) or polyester batting (on which I'd like some reassurance about it's ability to contain fibers...). I will use the plastic on the bass traps/corner traps since HF reflection is less of a problem for these, as I've read. This is the kind of solution I'd like to invest in, but I wanted to ask if there are others.

Also, I've already looked into some alternative insulation (UltraTouch, Basotect/Melamine foam, sheep wool) and crossed these out for various reasons.

If anyone can offer some insight, I would GREATLY appreciate it. This is unfortunately a huge hold up for me, since I'm literally going to be sleeping beside these materials.
Old 1 week ago
  #2
Gear Addict
 

You're concern is HF reflection. Here is a logical strategy (acoustic strategy I have no idea... beyond my pay grade):

1. Wrap the panels in sealant (plastic or whatever). That will keep the fibers trapped and inert.
2. Glue 1" acoustic pyramid foam to the front and sides of the panels. That will give you HF absorption and HF diffusion.
3. Wrap each of these new creations in acoustic fabric. Attach the fabric to the creations using velcro. That will make things look nice, and you can periodically remove the fabric for cleaning. You can also change the fabric color when you want to change the look of the creations.
Old 1 week ago
  #3
Here for the gear
 

Thanks for the suggestion. After some more reading, I guess I will try to add a HF absorption layer to the front of the panel. Do you think diffusion is all that necessary? If a layer of foam in front of the wrapped insulation is a proper solution, my next problem is deciding on 2" or 4" insulation. According to users on here, 4" is better, but I might not have the space to fit a 1 x 4 x 8 frame plus pyramid foam that juts out. Might look weird when wrapped in fabric too.
Old 1 week ago
  #4
Lives for gear
 

Pyramid foam works best when the corrugations are turned to the wall.
It won't give you any diffusion and you prolly don't want diffusion in such a small room anyway.

If you wrap mineral fiber in a thin plastic foil as is used to cover/protect stuff when people are painting you will have hardly any reflections; if you wrap this construction in fabric this will more than compensate for the eventually HF reflections.
Old 1 week ago
  #5
Here for the gear
 

That's pretty much exactly the answer I was hoping to get, Bert. But would a build like that really be good enough for taming any HF problems? I'd be using this painters plastic, and it seems to be the thinnest I can find at 0.31 mil.
Old 1 week ago
  #6
Gear Addict
 

Quote:
Originally Posted by Halica View Post
Thanks for the suggestion. After some more reading, I guess I will try to add a HF absorption layer to the front of the panel. Do you think diffusion is all that necessary? If a layer of foam in front of the wrapped insulation is a proper solution, my next problem is deciding on 2" or 4" insulation. According to users on here, 4" is better, but I might not have the space to fit a 1 x 4 x 8 frame plus pyramid foam that juts out. Might look weird when wrapped in fabric too.
An interesting thing to look at is frequency response charts. This web page has one:
https://www.buyinsulationproductstor...tic-board-2-3/

Look for the section on the web page:
Owens Corning 703 fiberglass board datasheet

An absorption coefficient of 1.0 means it is absorbing a lot of that frequency. A number like 0.15 means it is absorbing very little.

So at 125hz, the 4" insulation has an absorbtion coefficient of 0.95, which is excellent. 1" insulation has an absorption coefficient of 0.11 at 125hz, which is poor.

All of these thicknesses work great at 1000hz and above. It is when you go to the lower frequencies that the thicker insulation performs significantly better.

This page has an incredible amount of absorbtion coefficient charts:
https://www.bobgolds.com/AbsorptionCoefficients.htm

It's tough to get everything out of one panel type. Even 4" is not that thick for low bass absorption. Bass gathers at corners. So you can do ultra-thick absorption in the corners. If you did that, I think 3" rigid fiberglass with 1" of foam in front will do fine for the panels you are talking about. That would fit in the 4" frame and address the HF reflection concerns you have regarding wrapped fiberglass panels. You can create 3" rigid fiberglass by spray gluing a 1" panel to a 2" panel. Because you are encasing these in frames and wrapping the frames in fabric, you don't have to worry about the stress on the spray join.

This data sheet implies that 3" 703 exists, but I don't know where to buy it:
https://dcpd6wotaa0mb.cloudfront.net...=1582773799000

There is a fairly technical read that you might find interesting: ethanwiner.com/density.html

An important takeaway from the reading is to have many acoustic panels working on any particular problem. One "super panel" is not the best idea. You might also like the foil wrapping on the 703 in the photos.

Regarding whether diffusion is necessary, that's better handled by a QA with experts.

Last edited by gearstudent; 1 week ago at 04:38 AM..
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