Hey guys I am looking to build a set of absorption panels for the first reflection points in my music listening room. I will add bass traps later and for now I want to focus on the absorption panels. I have some general questions that I was hoping you guys could answer for me.
1. Is this roxul material good, 47 inch high x 23 inch wide x 5 & 1/2 deep? Or what dimensions should I get?
2. Is an air gap needed between the roxul and the back of the panel?
3. As far as the frame goes, would it be ok to build a frame using 2 x 4's as the top, bottom, and sides, and then use some light plywood on the back? Is regular mdf or plywood ok to use for the backing? Or does the backing need to be some sort of other materal?
4. How thick do I need to get the roxul? Is 3 inch thickness ok or should I shoot for 5 & 1/2 inch thickness?
5. I what to use Seersucker fabric to cover these with, is that ok? Does the fabric need to be any certain kind or does it not matter? I wasn't sure if some sort of acoustical fabric is needed?
From the dimensions you've given, I assume you're talking about the Roxul "ComfortBatt". I don't know if there is any STC (Sound Transmission class) ratings for that insulation. I just finished making some absorbers using Roxul "Safe n' Sound". That stuff does have STC ratings and it can be quite cost effective when compared to the price of the rigid compressed panels, assuming you can even find that in your area - I couldn't.
From the research I did - and I encourage you to do some yourself - the low-density batts, like Safe n' Sound, can be really useful with low frequency problems. You just have to use a
lot of it - like a double layer of 3" insulation, as a
minimum. That said, I don't know if I'd use it for first reflection points, because of the bulk. In fact, I only found it used for bass traps, which is what I'm using it for. I have mine behind an acoustically transparent false wall and projector screen, so the bulk can't be seen. I used a lot to make "superchunk" bass traps in the front corners and a pair of 6" think panels behind my main speakers.
Another thing is, with low-density material, don't use an air gap behind it. Air gaps are used with the compressed, higher density material. For a mounting frame, I used pegboard, like Jeff R. did, but I didn't use a perimeter frame. I just wrapped the insulation with fabric and stapled it to the pegboard. Because the insulation is soft, the edges and corners compress a little bit, giving it a bit of a pillow appearance, but I didn't care about that, as it's hidden behind my false wall. If you want to make a perimeter frame, you certainly don't need to use 2" lumber! If you are going to wrap the whole thing in fabric, I would just use 1/4" plywood for the whole thing - back, sides, top and bottom. Don't make it heavier than necessary! Just paint the perimeter a colour similar to the fabric, to make it less visible. If you want to just cover the insulation and leave the frame exposed, I'd use 1/4" MDF and paint it whatever colour strikes your fancy - it all depends on what you want. just remember that it doesn't have to be heavy lumber!
As for the fabric, I don't know what seersucker is. But, for first reflections, we're talking higher frequencies, so the fabric should breath easily. Hold a piece up to your face and if you can breath through it easily, it should be good.
I got some good info at
Studio building / acoustics - Gearslutz.com
Good luck with your project!
