Mineral wool rating question.

Posted by: 3Dfan

Mineral wool rating question. - 07/18/06 01:02 PM

I have made my DIY bass traps and mid/high absorbers from 2" thick #8 (or 8lb.) mineral wool panels. Of course I doubled up the panels for the bass traps. Is #8 a good panel to use for these purposes? I've seen some professional panel that are #3. I assumed that the higher the # the better the absorption qualities of the panel. Was I wrong in my assumption??
Posted by: Jason Jones

Re: Mineral wool rating question. - 07/18/06 01:31 PM

Higher density material tends to absorb a little better lower down in the frequency spectrum. This link has lots of comparison data.

http://www.bobgolds.com/AbsorptionCoefficients.htm

Though, on this note, I have a question for the panel. At shallow angles of incidence (for early reflections), higher density material doesn't sound as good to my ear.

Any thoughts on this?

Jason
Posted by: 3Dfan

Re: Mineral wool rating question. - 07/18/06 01:50 PM

So basically a 2" thick 2x4' panel #8 is a better panel for bass traps and mid/high absorbers especially if you double up the panels for the bass traps. Right??
Posted by: Jason Jones

Re: Mineral wool rating question. - 07/18/06 02:03 PM

Quote:
Originally posted by 3Dfan:
So basically a 2" thick 2x4' panel #8 is a better panel for bass traps and mid/high absorbers especially if you double up the panels for the bass traps. Right??
Should be great for your purposes.

Jason
Posted by: 3Dfan

Re: Mineral wool rating question. - 07/18/06 10:11 PM

Unbelievable!
I just found out the the company I bought my mineral wool from told me they sold me #8 panels but they were really #6.
Is there a big difference in how the #6 panels will perform?

Are #6 panels good enough to use for bass traps in an 11x11' room?
The #6 panels are 2" thick so I doubled them up to 4" thick. Is this good enough?
Posted by: Viper_Z

Re: Mineral wool rating question. - 07/19/06 12:17 AM

For bass trap.. the thicker the better.. why not use 6" thick?
Posted by: Jason Jones

Re: Mineral wool rating question. - 07/19/06 08:30 AM

Quote:
Originally posted by 3Dfan:

Are #6 panels good enough to use for bass traps in an 11x11' room?
The #6 panels are 2" thick so I doubled them up to 4" thick. Is this good enough?
6# panels are fine. Don't worry.
Posted by: bpape

Re: Mineral wool rating question. - 07/19/06 03:24 PM

If you're going 6" thick, you can do 4lb and it will work as well or better than 4" of 8lb.

Also, for reflection points, the 4lb will do as good or better. You don't necessarily need a really dense material - save yourself some money.

Bryan
Posted by: 3Dfan

Re: Mineral wool rating question. - 07/19/06 09:57 PM

Actually it is #6 mineral 2" thick, doubled up to 4" thick. I ordered #8 but they sent #6 and I didn't realize it until I'd already built my bass traps.
Posted by: bpape

Re: Mineral wool rating question. - 07/20/06 07:58 AM

6lb will be fine. 6" will still provide additional extension for the bass absorbers.

Bryan
Posted by: 3Dfan

Re: Mineral wool rating question. - 07/20/06 11:07 AM

Now I'm paranoid that I should have made the bass traps 6" thick. It's a bit late now. They're in frames and covered in muslin.
All the plans I saw were for 4" bass traps.
I thought by putting them at an angle in the corners the air space helped absorb a substantial amount more in the bass frequencies.
Posted by: bpape

Re: Mineral wool rating question. - 07/20/06 09:41 PM

It does help. The 3 things that help extend absorbtion are:

- Thickness
- Density (to a point)
- Distance to the boundary (to a point)

4" of 6lb mineral wool will do a pretty good job. If you're really paranoid, stuff some additional insulation back behind them.

Bryan
Posted by: 3Dfan

Re: Mineral wool rating question. - 07/20/06 10:22 PM

Thanks for the tip. Also that rating chart was nice Jason.
Does anyone know of a chart that shows the rating on 4" mineral wool #6 that is spaced off of the wall in the corner??
I've seen some ratings for Lenards bass traps and they are higher than the 4" mineral wool so I was wondering how much the rating of mineral wool are increased when the panels are straddling the corners. Any ideas??
Posted by: bpape

Re: Mineral wool rating question. - 07/21/06 05:47 AM

Take ANY rating in a corner with a grain of salt. There is no set of standards as to how to do it.

All one can do is extrapolate how similar materials work in A mount and J mount testing and then couple that with knowing the additional bennies of the corner mount and the hump at 100Hz that is still not fully understood.

Bryan
Posted by: 3Dfan

Re: Mineral wool rating question. - 07/21/06 10:32 AM

What do you mean by hump at 100 Hz? Does corner mounting cause a hump at 100 Hz?

Would you say that my bass traps (4"thick, #6 mineral wool)straddling the corners will out perform Auralex acoustic foam bass traps?
Posted by: 3Dfan

Re: Mineral wool rating question. - 07/21/06 11:11 AM

What if I took some polyester batting and stuffed it behing the corner traps in a couple of the corners?? Polyester batting is basically pillow stuffing. Would this help absorb a little more bass. I'm out of mineral wool panels and if possible I'd rather not buy more after the last order was screwed up. If some polyester filling would make a difference I have some of that. What do you think? Keep in mind this room will be for recording acoustic guitar and vocals. Bass and drums will be recorded direct.
Posted by: Jason Jones

Re: Mineral wool rating question. - 07/21/06 12:09 PM

Quote:
Originally posted by 3Dfan:
What if I took some polyester batting and stuffed it....
Don't think that would help at all. You could stuff the cavity with regular pink insulation from Home Depot or get some Ultratouch cotton.

The cotton is pretty inexpensive and no fiberglass to work with. Check out http://www.bondedlogic.com and search for a distributor in your area.

Jason
Posted by: bpape

Re: Mineral wool rating question. - 07/21/06 01:42 PM

You can even use standard 'pink stuff'. It will help some.

The 'hump' I was referring to was a hump in absorbtion. All absorbers mounted in a corner (straddling or solid) seem to produce a hump in absorbtion around 100Hz. It's not fully understood why yet. It just happens and it's not a bad thing.

Bryan
Posted by: 3Dfan

Re: Mineral wool rating question. - 07/21/06 02:50 PM

Thanks for the link Jason. What exactly kind of ultratouch cotton do you recommend for this application? There is a dealer in Akron so I'm interested but I need to know EXACTLY what kind will be best. Thanks again.
Posted by: bpape

Re: Mineral wool rating question. - 07/21/06 04:50 PM

The UltraTouch is all the same density - about 1.2 lbs/cu ft. It's just a matter of if you want it in 16 or 24" wide and 3.5 or 5.5" thick (R-13 or R-19)

If you are just stuffing it behind panels, either will work - just a matter of getting the right amount and with the least cutting. It doesn't cut nearly as easily as 703 does. Think electric carving knife at a minimum. Some people use a table saw.

Bryan
Posted by: 3Dfan

Re: Mineral wool rating question. - 07/21/06 08:09 PM

If I decide to go for the pink insulation what kind would you recommend?
Any ideas on how to keep it behind the traps?? Should I put it in cloth bags?
Could I just roll it up the wall behind where the bass traps sit and then use a couple of nails to hold it to the wall and then put the trap in front of it?
Posted by: 3Dfan

Re: Mineral wool rating question. - 07/21/06 08:31 PM

Whether I go with the cotton or pink insulation, could I just unroll it and attach it to the back of my bass traps and then put the bass traps back into the corners?? Would that be enough or do I need more behind the traps?
Posted by: Jason Jones

Re: Mineral wool rating question. - 07/22/06 01:34 AM

Quote:
Originally posted by bpape:
The UltraTouch is all the same density - about 1.2 lbs/cu ft. It's just a matter of if you want it in 16 or 24" wide and 3.5 or 5.5" thick (R-13 or R-19)

If you are just stuffing it behind panels, either will work - just a matter of getting the right amount and with the least cutting. It doesn't cut nearly as easily as 703 does. Think electric carving knife at a minimum. Some people use a table saw.

Bryan
Oh c'mon, I cut this stuff with some scissors from the craft store. \:D Just cut the top couple of inches and then cut the bottom portion - takes a couple of minutes.

I would recommend that you get 24" wide. I'd probably get the 3.5", though NOT a big deal either way.

Then roll it up and stack it in the corner. Then put the bass traps back in front (where they were originally) and you're done.

Jason
Posted by: bpape

Re: Mineral wool rating question. - 07/22/06 07:58 AM

You must have one heck of a pair of scissors. But then and again, I guess you're not looking for perfect cuts either.

I know when guys cut this into triangles to make solid chunks, 99% of them tell me that it's easier on a table saw.

Bryan
Posted by: 3Dfan

Re: Mineral wool rating question. - 07/22/06 09:21 AM

If I treat just two of the corners this way will it make a big difference? I have a door in one of the corners so I use a portable bass trap there and I can't put anything in that corner.

Also, would it help if I put some of it behind my bass traps that are hanging in the horizontal corners?

About how much do you think I'll need? I'll probably have to drive a couple of hours to get it and I don't want to end up not having enough.

Also, my floor to ceiling traps are 8' tall and so is the height of the ceiling. I had to wedge the traps into place by pounding on the edge of the frames with a hammer and wood block. They are really snug in the corners. Could having them this snug in the corners reduce the effectiveness for absorbing bass?
Posted by: bpape

Re: Mineral wool rating question. - 07/22/06 12:38 PM

Better plan on taking a truck. The bundles are pretty big. With the price of gas and a 2 hour each way trip with a truck, it might not be much cheaper than buying and shipping.

2 corners is better than none and you might as well do the horizontal ones too.

Bryan
Posted by: Jason Jones

Re: Mineral wool rating question. - 07/22/06 02:45 PM

Quote:
Originally posted by bpape:
You must have one heck of a pair of scissors. But then and again, I guess you're not looking for perfect cuts either.

I know when guys cut this into triangles to make solid chunks, 99% of them tell me that it's easier on a table saw.

Bryan
My scissors aren't anything special. But, for my purposes, I don't need perfect cuts (stuffing mid/high absorber panels or rolling up and stacking behind bass traps.)

I wouldn't cut it into triangles like that, though, unless I had a gun to my head. \:\)

Jason
Posted by: 3Dfan

Re: Mineral wool rating question. - 07/25/06 09:54 AM

ANother concern I have is that on two of my 8' corner traps I built the panels glued FSK to the front and then wrapped them in landscape fabric (which is like a hybrid of paper and fabric) and then wrapped them with a layer of muslin.
I'm wondering if the landscape fabric is possibly hindering them from absorbing as much bass as they could without it. The landscape fabric is black and when I hold it up to the light I can see the light through the fabric pretty easily so it's not very thick but I'm wondering if I should have not used it.
At first I was just going to wrap all the bass traps in it but after doing a couple of them I didn't think it would be as good as just using muslin. Instead of removing the landscape fabric I just covered it is muslin.
Could this be hindering my traps ability to absorb bass?
I'm going to buy the ultratouch cotton this afternoon. Hopefully this stuff will really help my room sound a lot better.
Posted by: bpape

Re: Mineral wool rating question. - 07/25/06 08:27 PM

I doubt it. The landscape fabric won't do diddly to stop the bass. All they might potentially do is change the membrane effect of the FSK - but the muslin tightly wrapped will change it a bit on it's own.

Bryan
Posted by: 3Dfan

Re: Mineral wool rating question. - 07/25/06 11:13 PM

Does it matter if the muslin is not wrapped really tight? It is pretty tight but it's not perfect. Does that matter?

I put the ultratouch cotton behind the bass traps and it seems to have tamed the bass a bit more. On the horizontal bass traps I just took a piece of the ultratouch cotton and folded it over and stuffed in in the air gap. I had to manipulate a bit to get it past the nylon ties that the traps are hanging from but it seemed to work ok. Just having a few more inches of ultratouch behind the traps where the air gap was will make a big difference in bass absorption, won't it?? Thanks again for the input!