Insulation Density

[thedavidlim]

Hey all,

I've done some searches but info is spread out to isolated comments and I'm interested in consolidated information. Or maybe someone can do a better job and point me to an existing thread.

I recently bought mineral wool for bass/multiband trapping and 1st reflection points (mainly 2x4 panels between walls and ceiling, and front wall SBIR). The available baffles were 8# Thermafiber from my local insulation supply. BUT after coming back here, I noticed a few people say 8lb is ineffective (too dense) for trapping, although could be useful for absorbing reflections. According to the manufacturer specs, what I bought is 8lb nominal, actually 6lb. Is that still too dense?

Main questions, then:
1. Is 6lb still to dense for what I want to use these for?
2. What about SBIR, is it still too much?
3. Can piled up pink fluffy be used for floor-to-ceiling bass traps, like super chunks?

I'll leave it at these to start, at least.

Hope everyone is staying healthy and finding things to do while we're all stuck at home!

[DanDan]

1. Is 6lb still to dense for what I want to use these for?

OC 705 has been used in 4" panel/batt traps forever. It may or may not be slightly over the top in density, 703 being better, but it is more rigid and it also benefits a bit from a damped resonant panel effect.
So for thin, 4" trapping, your product should be just fine.

2. What about SBIR, is it still too much?
Hmm, aah, hmmm, in my experience more often than not it measures better to have the speaker kiss the Front Wall rather than placing relatively small relatively think traps between Wall and Speaker. Other SBIR, particularly the Back Wall is best treated with thick low density fibre a foot or more thick.

3. Can piled up pink fluffy be used for floor-to-ceiling bass traps, like super chunks?
The tested actual Studiotips Superchunks were 703, a 3pcf product. I would use that or if you are going for deeper traps go for lower density.
Afaik, boggy's 2 foot deep treatments were slabs of Knauf Ecose at probably about 32Kg i.e. 2pcf.

Bear in mind that the Master Handbook of Acoustics has data showing little or no difference in absorption over a range of densities of 4:1

For some reason, perhaps vested interests, the USA seems to be lagging behind in adopting Polysester insulation. Might be worth a Google though. Caruso Isobond has very high absorption, is fireproof, and intrinsically cosmetically 'finished'

[thedavidlim]

Thanks DanDan.

That all makes sense. My room is 11' wide, so I've been thinking about how to have the speakers in the right places on the front wall while still putting effective bass traps in the corners. Complicating things a little bit is the electrical panel that's centered 18" from the front left corner, so anything I do will have to be movable, both practically and to keep it up to code. I'd put 32"W floor-to-ceiling baffles in the corners at 30º with the 4" 6# mineral wool in them, (open in the space between them and the wall, which is covered in the same 4" 6# insulation) with the speakers backed up to and touching those 30º walls, but still have an SBIR dip at ~125hz. I'm guessing that may be because of the side walls, which are 3' away? They also have 4" insulation on them, but regular fluffy fiberglass at the moment.

[Paulus87]

That 125hz dip is very common with speakers on stands and is usually caused by the floor bounce.

3 solutions you can try;

1. Best solution is flush mount your speakers in the front wall and make sure the floor bounce misses your ears or is blocked by the console.

2. And two subwoofers in the front corners

3. Move the listening position... but that may cause other problems.

It’s all a juggling act

Paul

[thedavidlim]

Cool. I'm planning to try some different configurations this afternoon. I found Barefoot's Wall Bounce Calculator too, so am interested in what it "suggests".

I can't flush mount because I need the front wall and corners to be open (except for the 4" insulation) so I can keep access to the electrical panel open. But I can move the 30º walls I made and see if bumping the speakers right up to the front wall changes anything too.