Superchunks in an odd shaped corner and what material to use

[pinksoir]

Hi there, first time poster but I'd really appreciate some help.

The Corner
-----------------

I need to do some superchunking but one of my front corners is a weird shape:

room corner.JPG

This is a view as if you were looking from above. As you can see it's got another sort of protruding corner in it. Also, the window is not flush with the wall, but sits at a 5" recess. The window is about 10" from the floor and 12" from the roof, so it's most of the front wall. However, it's about 7.75" from the side wall, if you understand me. If I were making 34" superchunks, what should I do about this corner?

So 34" triangles have 24" sides, 16" of one of the sides will not be flush with the window but will have a 5" gap behind it. Also, I'll have to cut a square out of the back of the chunk to account for the protruding corner. So of that one side, only 2.75" will actually be in contact with the wall. Furthermore, it won't ever be very deep, and where it should be deepest (in the middle) it will only be ~10" deep. And the deepest it can be is ~13".

Will this still be good?

If I were to do 24" chunks (keep costs lower) for this corner that'd give me 4" at the shallowest and 8" at the deepest. Would that be ok or should I go for 34"?

The corner over the other side is normal except for also having the window recess gap.

The Material
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What would be most effective in a floor to ceiling 34" superchunk; RW3 or fluffy rockwool?

I currently have 6 slabs of rigid RW3 which would be enough to superchunk two corners of my studio in 24" faced triangles. A pack of 4 4" slabs is ~€40 (3 slabs needed to do each corner in 24", 6 slabs for 34") and one bale of (2 x rolls) 4" fluffy is ~€25 (1/2 bale needed for one corner in 24", one bale for 34"). For me money is pretty tight so I'd be aiming for the cheapest option that gives me the best results.

I want to be treating around the 60Hz and 120-130Hz ranges.

From all my searching I've not found a definitive answer, so I hope someone can give me a clue!

Cheers.

[pinksoir]

I'd really appreciate a bit of guidance on this...

I've built my frames, I just need to find out what material to fill it with. B&Q has these as a 3 for 2 at the moment (so 3 for €50) - it's fluffy Knauf glass wool, though I can't find the density anywhere...

http://www.diy.com/nav/build/insulation ... m-11127503

Would this stuff do the job?

Thanks.

[Soundman2020]

Hi "pinksoir", and welcome!

Your basic plan looks good. The only thing I'd add is to stuff the gap between the glass and the side of the superchunk with insulation too.

The "kink" at the back doesn't matter at all. No problem there.

On the 24" vs. 34": More is always better, but you do what you have to do and live with the results. If you can't do 34" for whatever reason, then 24 is still good, just not as good as 34. But don't go less than 24.

What would be most effective in a floor to ceiling 34" superchunk; RW3 or fluffy rockwool?

What matters is gas flow resistivity. That's what sound waves "see" as they pass through it. But most manufacturers don't test for that, unless they are specifically making acoustic absorption, since it isn't needed for thermal specs. Some thermal insulation still has good gas flow resistivity, but the problem is, you don't know which! Fortunately, there is a very rough, ball-park correlation between gas flow resistivity (which manufacturers don't provide) and density (which they normally do provide). For mineral wool insulation, it turns out that the optimum density is around 50 kg/m3. For fiberglass insulation, optimum density is around 30 kg/m3. So go for stuff somewhere around those numbers, and you'll be fine.

I want to be treating around the 60Hz and 120-130Hz ranges.

60 Hz. is pretty low to be treating with pure absorption, if you have major issues in that range. You might need some other form of bass trap if 60Hz is a big problem. Absorption by itself isn't very effective down that low, unless it is REALLY thick.

Maybe you could run some tests of your room with REW, and post the results here, so we can see what you are dealing with.

- Stuart -

[pinksoir]

Thanks Stuart, I appreciate the help.

I went ahead and started building my chunks. I'll post up my REW results once I have my main treatment done.

[Soundman2020]

I'd suggest that you do a test with REW right now, BEFORE you put in any treatment! That way, you'll have a baseline to compare against, so you'll now how well your treatment worked, in what areas of the spectrum, and what still needs to be done afterwards.

Do one test with the room empty, and additional tests at each step of the treatment. And it is VERY important to get the mic in the exact same position every time, for each test. Accurate to within a cm or so.



- Stuart -