Acoustical Treatments Master Thread - Page 285

Originally Posted by Docj04

Acoustic Performance

Acoustic Performance

Random incidence
absorption coefficient
acc. to EN ISO 354 125 250 500 1 000 2 000 4 000

at 10 mm 0.02 0.04 0.08 0.19 0.53 0.44

at 32 mm 0.08 0.17 0.51 0.56 0.25 0.24
This is the absorbtion table (i think) from the armaflex website that my local SPI insulation warehouse manager recommended. It's supposedly nice and rigid, requiring no frame, and is fairly cost competitive with other options. Can anyone evaluate this table an comment on the effectiveness of this product???

Sorry that the table is out of alignment, at 125, the 0.02 and 0.08 should be directly underneath

Originally Posted by robc1976

Figured I would update with some pics, I have 4 QRD's to be ordered and placed or rear side walls to complete the room.




Right MLP:




Left MLP:




Rear wall:




QRD diffusor:

Originally Posted by myfipie

You are going to want to make those no less then 100mm thick and straddle corners if you want to use them as broad band bass traps. Honestly I would recommend thicker then that if you can.

Originally Posted by Brad Horstkotte

No, not as good - does that material have a paper facing? Not sure why else the absorption would be so bad at the top end.

703 1" (25mm) on wall 0.11 0.28 0.68 0.90 0.93 0.96
Armaflex 32 mm (1.26") 0.08 0.17 0.51 0.56 0.25 0.24

I think myfipie's comment applies regardless of the material - 4"+ and air space behind at a minimum for bass trapping.

Originally Posted by pepar

More volume, too, right?

Originally Posted by Brad Horstkotte

Do you mean you'd need more volume of mineral wool? My understanding is that that's more impacted by density than the material type - i.e. ~3 pcf mineral wool performs similarly inch for inch compared to ~3 pcf rigid fiberglas. Maybe you meant lighter density, like pink fluffy?

Originally Posted by localhost127

Docj,
do you have any photos of your space you're willing to share? would assist with recommendations on placement and approach -

Originally Posted by Docj04

Well, I got a 6-pack of 2'x4x1.5"', and a roll of burlap to cover it...

HATE the mineral wool. $30 for the panels,and $60 for the burlap = lessoned learned about the mineral wool.Too floppy and easily torn/damaged.

I'll end up keeping the mineral wool for odds and ends, and getting some 703 instead.

Originally Posted by HKman

They may be a stupid question but I used this DIY method to make some cheap acoustic panelling:

http://www.amateurhometheater.com/di...ic_panels.html

I used pretty much the same duct board. Obviously, fiberglass isn't good for you and every time I handled it, there is usually a slight irritation if it comes in contact with skin.

Now that the project is done and the panels are up, I'm beginning to worry that this may not be good to breathe in and if there are any asbestos type concerns. I know it would be a huge waste of time and money if I take these down and throw them out but health is first. I'm assuming that because they are covered in speaker cloth, they should be fine.

Any re-assurance or warning bells?

Originally Posted by nezff

I didnt use fiberglass for this reason.

Originally Posted by localhost127


http://www.gearslutz.com/board/bass-...rs-review.html

Using the Whealy calculator, I tried a few different depths. A 24" face corner trap has a maximum depth of 24 inches (if sound were to enter at a very oblique angle almost parallel to the large 24" face).

Originally Posted by HKman

Is the fact that the the surface of the fiberglass has been spray-glued (to fix to the speaker cloth) and is fully covered by speaker cloth make any difference?

Originally Posted by myfipie

Good stuff but
When you straddle the corner it is much more effective then what you posted. I did a quick test of our lab/test room with 8 Monster traps. 3 corners floor to ceiling and 2 on the back wall. Pretty much follows the results we got from Riverband Lab when we tested there. Which shows a great deal of absorption below 100 hz. Note I would want to put in even more treatment but it is pretty close to a 10 db window which is pretty impressive with a great deal of improvement at 67hz.

Originally Posted by nezff

So blue jeans and newspaper shouldn't be in our homes but metal slag and glass fibers are ok because they will break down.

Originally Posted by localhost127

fiberglass is a porous material - it works by converting kinetic energy of the soundwave traversing through the series of porous ducts within the insulation into heat (friction). by coating the face of the insulation with a spray or glue, you are blocking the porous holes, restricting flow through the absorber - yielding unexpected results (reflection due to impedance change). you do not want to use spray or glue to coat the face of the insulation to bond fabric. maybe a small dab of 3M spray in the corners...

Originally Posted by sukumar

Is rockwool same as pink stuff? I read from localhost127 posts that it is best to absorb/pass waves.

Originally Posted by sukumar

Unless there is air gap on the back, does it make difference if sound waves hit glue or wall to reflect back? Also, if it is just meant for high frequency absorber instead of basstrap, the material should absorb all of it by the time it reaches back right?

I just want to clarify if the reason is not valid.

Originally Posted by localhost127

if no air gap and the panel is flat against rigid boundary, then it will not make a difference. but by not utilizing an air-gap, you are eliminating your "free lunch".

Originally Posted by localhost127

what is your definition of a "high frequency absorber"? in the specular region, the lower frequencies have longer wavelengths with inherently more energy content. thus, attention for broadband panel absorbers generally needs to be with regards to the lower end of the specular region.