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Owens Corning 703 vs. Roxul Safe 'n' Sound?

I'm going to make some sound absorbing panels to place on the wall behind my listening chair. Owens Corning 703 and Roxul Safe 'n' Sound rigid boards are two choices to make them with. Anyone have experience with both, or even one?
128x128bdp24
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One thing to know about the acoustic materials is that you need massive amounts of thickness if you want to absorb a lot of the lower bass frequencies. Yes, putting a space behind the fiberglass will help because the sound will bounce off the wall and back into the fiberglass. However, if you want to absorb the lower frequencies, you’ll need a very thick trap (like the 6-7" bass traps from GIK). If you want to put multiple layers of the fiberglass in, you need to keep them at the lower densities (like 2.5 - 3 lbs).

I chose the 2" thick 8 lb Roxul because I wanted to limit how much mid/high frequencies it would absorb, but I still wanted decent bass absorption. At a certain point, the denser material will start reflecting sound at a thickness level. A 4" stack of the 8lb Roxul will probably not work any better than a 2" stack. However, putting a 4-8" stack of 2.5lb Safe-n-sound will absorb a lot more bass (as well as a lot more mids/highs).

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bdp24 OP
9,966 posts
 

I didn't expect the extra space behind the panel to turn it into a bass trap! Just to lower its effective absorptive range a little. In the specs chart, it looks as if the Rockboard 60 may be a little better at higher frequencies than the 80, though the difference is marginal and perhaps insignificant. I don't want to over think this! But since the listening position has to be right up against a wall (to allow my dipole speakers to be positioned 5' from the wall behind them), and low-frequency eigenmodes run along room boundaries, absorption at as low a frequency as easily possible would be nice.

So I went to Home Depot last night, and though the HD website stated that the branch I went to had Safe 'n' Sound in stock (even the number of packages), I couldn't find any on the shelves. The HD "dude" couldn't even find it in the stores computer, telling me any acoustical product would have to be ordered. I went in to look at the stuff, to see if it is soft and loose like fiberglass insulation, or stiff like OC703. So Monday I'm going to Lowes, whose website indicates it has 2' x 4' Safe 'n' Sound in stock. We'll see!

sbank's avatar
sbank
3,381 posts
 
@bdp24 I feel your pain, with both HD & Lowes the inventory often doesn't match what online says is there. A frequent time waster. 

Your plan sound solid. If you do want more low freq absortion (i.e. bass traps for those front corners, rock wool was what was recommended to me by an acoustics specialist who consulted on my room and built my custom stuff. The 703 for wall and freestanding panels, but rock wool for the corner bass traps to maximize absorption relative to their volume. Cheers,
Spencer
bdp24's avatar
bdp24 OP
9,966 posts
 
Thanks Spencer. I had a session today, and the studio owner had real good acoustical treatment of his walls---a mixture of RPG diffusors and absorbers. I have a couple of spare 9" x 3' ASC tube traps---maybe I'll put them right behind the listening chair, with a couple of 2" x 2' x 4' panels stacked on top, for higher frequencies.
bdp24's avatar
bdp24 OP
9,966 posts
 
I was back near the same Home Depot today with a little time on my hands. I went in and looked for the Roxul Safe ’n’ Sound myself this time, and found it right on the shelf. S’n’S is 3" thick, and soft and loose, very limp, not at all like the OC703 semi-rigid panels, but more like cotton batting. Acoustimac offers empty 24" x 48" DIY panel frames in various depths, including 6". I’ve read that having a space behind the acoustical material will increase a panels ability to absorb low frequencies---a good thing for me due to the listening position being so close to the rear wall, but what if I was to stuff the frame with two layers of the 3" thick S’n’S? Possessing it’s 2.5lb. density, a 6" thickness of S’n’S won’t reflect back much of the mids and highs hitting it, but will that thickness absorb more, or less, lower frequencies than will a single 3" layer with a 3" space behind it? Acoustimac offers the frame both with and without a thin plywood rear back panel. Since my panels will be right against the wall, I surmise that back wouldn’t affect its performance.
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