Rockwool for bass traps?

[Nosound]

Okay I gotta a bigger room finally to record and mix in thanks to my understanding wife, My problem now is I need more bass traps I've already have some DYI using rigid fiberboard but with the bigger room I have to much bass on my mixes after A-Z testing just wanted to know if I could use Rockwool insulation 4" 2'x4' slaps for bass traps cut in triangle on each corner wall then maybe more behind the monitors and maybe more on side walls and ceilings? But heard Rockwool only good to 100Hz and above I already know about Ethan's link but no mention of Rockwool only rigid fiber board. Any opinions and info. greatly appreciated.

[Ethan Winer]

Originally Posted by Nosound

I already know about Ethan's link but no mention of Rockwool only rigid fiber board.

Not so. The following is from my Acoustics FAQ.

--Ethan

Now that you know what rigid fiberglass is, where the heck do you buy it? You probably won't find it at your local hardware store or lumber yard, but many insulation suppliers stock it or can order it. Start by looking in your telephone directory under Insulation and also Heating / Air Conditioning Suppliers. You can find the name of an Owens-Corning dealer near you by calling 800-GET-PINK (800-438-7465) or from the Locator page on the Owens-Corning web site. Other companies, such as Knauf, Armstrong, and Delta, make similar products, and they often cost less than fiberglass from Owens-Corning. You can contact them directly to find a distributor near you. In the interest of completeness, here are some other manufacturers that make similar products: Johns-Manville, CertainTeed, Roxul, Ottawa Fibre, and Fibrex.

When assessing rigid fiberglass, it is important to know its density so you can compare equivalent products. Owens-Corning 703 has a density of about three pounds per cubic foot (45 kilograms per cubic meter), and 705 is about six pounds per cubic foot (90 kilograms per cubic meter). Therefore, products from other companies that have a similar density will have similar absorption characteristics at the same frequencies. Note that some companies call their products mineral wool, mineral fiber, or rock wool, but acoustically they are equivalent to fiberglass.

[Nosound]

Okay Ethan you state some companies call it rock wool but rock wool is limp and seems not to be as dense as 703 . According to one suppler that sells rook wool states that rock wool is only good for 100Hz and above is this true? biggest problem I have is budget. I can buy 2 panels of rock wool for the same price as one panel of 703 my question is since I can buy two to one, which also in your info. you claim acoustically that rock wool is equivalent to 703, which would be better the 703 or the limp rock wool according to my Frqz. analyzer I show huge spikes in the 125hz and above in my new room even with 6-703 panels I already made. I now my mixes have that one note bass thing plus I have a weird ringing sound coming out of the monitors when I DI the bass or palm mute a D tuned guitar through a half stack at medium volume. Never heard it before until I moved everything to the new room which BTW was my x-mas gift from my wife.

[Scott R. Foster]

Originally Posted by Nosound

According to one suppler that sells rook wool states that rock wool is only good for 100Hz and above is this true?

No - neither rockwool nor fiberglass is intrinsically superior acoustically - they are generally equivalent but you must choose the grade of either material based on its physical properties.

OC 703 is a 3 lbs. semi-rigid fiberglass board that is a very efficient compromise of handiness [not too floppy, not to flakey], price, weight, and space efficiency [has sufficient gas flow resistance to work as a broadband absorber in corner mountings even with panels as thin as 4"].

To match these attributes in rockwool requires a higher density because of the nature of the material. Generally you could expect similar acoustic performance with a panel about 50% denser in grade [this would approximately match the gas flow properties of 703] which works out to about 5 lbs. per cubic foot or about 60 kg/m3. But even at this density rockwool has inferior handling properties to 703 and yields a heavier panel [no biggy for a hang forget application, but if portability matters this is a flaw].

Bottom line - if price in near equal I would go with 703 [lighter panel, easier to work with] - but if you can gain a significant price advantage use a +/- 60kg rockwool.

You can use lower density rockwool [less than 60kg/m3] or fiberglass [less than 3 lbs. per cubic foot like 703] but in both cases the stuff gets really floppy which means you need to build a more substantial frame, AND you need to increase the thickness of the panels.

Regular pink fluffy insulation will make a great broadband absorber - but you need upwards of upwards of 1.5' of thickness to work low in the band [get broadband performance].

[Nosound]

Thank you so much guess I'll stick with the 703 since it'is easier to work with and I missed quated about my Fqrz. 125Hz and below not above.

[Ethan Winer]

Originally Posted by Nosound

rock wool is limp and seems not to be as dense as 703

Scott already gave you the right answer. Yes, rock wool is floppy, and it can sag and get lumpy over time. But it works and it's cheap!

> According to one suppler that sells rook wool states that rock wool is only good for 100Hz and above is this true? <

Answer 1: No, it's not true. The real issue is most that labs don't measure absorption below 100 Hz, so official data is not available. This does not mean an absorber suddenly stops working abruptly at 100 Hz! It just means that no official data is available.

Answer 2: I don't know why so many people think they're qualified to comment on acoustics and absorbing materials. These days everyone's a damn expert.

--Ethan

[Nosound]

Well Ethan now that's a vote for rockwool which as I stated earlier I can buy 2 to 1 and I planed on making my own slip covers or whatever you want to call it like I did with the 703 using burlap. and thanks about the low down on the lab test that was a main concern I had with the rockwool, now I know. I really don't care how floppy it is because I'm DYI guy and making panel cakewalk but making your own studio desk is a pain in the ass but then again furniture was never easy to make.

[Glenn Kuras]

Originally Posted by Nosound

Well Ethan now that's a vote for rockwool which as I stated earlier I can buy 2 to 1 and I planed on making my own slip covers or whatever you want to call it like I did with the 703 using burlap. and thanks about the low down on the lab test that was a main concern I had with the rockwool, now I know. I really don't care how floppy it is because I'm DYI guy and making panel cakewalk but making your own studio desk is a pain in the ass but then again furniture was never easy to make.

I would go with the rockwool then. Heck even better cut them into triangles (2 or 3 foot face) and stack them in the corners. That will will give you the best over all absorption. It may cost more, but will kick some ass in the low end.

Glenn

[nosebleedaudio]

I second the vote for 703 with respect to easier to work with, if you have to glue rock wool for some reason it will suck, and it will suck as well when used as the finished layer before cloth.
But I have used it behind 703 with fair success.

[Nosound]

Well I decided I'll use both I'll use the triangle ideal for the corner with rock wool then use the 703 for side and ceiling. Dam they need to invent monitors with a built in Frqz adjuster that would auto tune the monitor to any room.

[Glenn Kuras]

They do have something like that but it does nothing for ringing and tell me something how would you ever eq a null. :)

Glenn