John Sayers' Recording Studio Design Forum Archive

Most advice I read on this and other forums suggests that 4" 703 is the way to go for building bass traps, but my local Specialty Products outlet says that neither 703 nor 705 is made in that thickness (2.5" is the thickest). I know you can double up 2" panels but does anyone know of a competing product that's made in thicker panels (I assume it must be cheaper than buying twice the amount of 2" 703, which is $1/s.f.). And would 5" (2.5" x 2) be even a better bass trap material?

Both ARE made in 4" thickness. you can use JM, Certainteed, Roxul, Thermafiber, Fibrex etc with a desnity of 2.5-5 p/cf.

Thanks, I suppose the clerk I spoke with was simply uninformed (though I insisted to her that the existence of 4" 703 was widely known among studio construction experts). I'll ring them up again and ask them to dig a little deeper in their records to find pricing/ordering info.

As a follow up question, how does the density (lbs/sf) affect absorption? I assume the denser material, having more mass, would be more effective but I just want to find the best value of bass absorption per s.f.

Cojonesonasteek wrote:Thanks, I suppose the clerk I spoke with was simply uninformed (though I insisted to her that the existence of 4" 703 was widely known among studio construction experts). I'll ring them up again and ask them to dig a little deeper in their records to find pricing/ordering info.

As a follow up question, how does the density (lbs/sf) affect absorption? I assume the denser material, having more mass, would be more effective but I just want to find the best value of bass absorption per s.f.

Ialready gave you the practical answer 2.5 - 5 pcf. IF you want dissertations, that can be arranged. For what you are doing, 2.5 - 5 pcf.

Andre

Going much above 3 PCF for exposed traps can cause problems with uneven absorption - since very few sound waves in a room are perpendicular to the walls, you need absorption that's even at wider angles of incidence; the denser the material, the more sound will "graze" off the surface instead of being absorbed.

As to what thicknesses 703 is available in, this from Owens Corning -

http://www.owenscorning.com/comminsul/d ... Series.pdf

Check under Availability for available thicknesses, feel free to print this out for your doubting debutante... Steve

AVare wrote:

Cojonesonasteek wrote:Thanks, I suppose the clerk I spoke with was simply uninformed (though I insisted to her that the existence of 4" 703 was widely known among studio construction experts). I'll ring them up again and ask them to dig a little deeper in their records to find pricing/ordering info.

As a follow up question, how does the density (lbs/sf) affect absorption? I assume the denser material, having more mass, would be more effective but I just want to find the best value of bass absorption per s.f.

Ialready gave you the practical answer 2.5 - 5 pcf. IF you want dissertations, that can be arranged. For what you are doing, 2.5 - 5 pcf.

Andre

Thanks, Andre, no dissertation needed. I just wanted to know if 5 pcf density 703 is more effective as a bass trapping material versus the cheaper 2.5 pcf version. No sense spending extra money on the denser version if there are diminishing returns beyond a certain density. I have a fairly large room to treat so am trying to get my arms around costs for our rebuild budget. Knightfly posted a useful response to that question so I'll take his advice and stick with the 2.5 pcf, which I already have several boxes of from a previous studio.

Cojonesonasteek wrote:

AVare wrote:

Cojonesonasteek wrote:
Thanks, Andre, no dissertation needed. I just wanted to know if 5 pcf density 703 is more effective as a bass trapping material versus the cheaper 2.5 pcf version. No sense spending extra money on the denser version if there are diminishing returns beyond a certain density.

No insult intended, but ask what you want, not a general query. If anything, 705 is slightly WORSE at lf than 703 at thicker sizes. Add to that Knightfly's remarks about HF grazing absorption of 5 pcf glass wool. The absorption of rock based mineral wool is slighter shifted to heavier materials. EG 3pcf glass wool is most similar to 5pcf rock wool. Hence the generic 2.5- 5 range.You are now starting to get the disseratation that you didn't want!

Don't forget, ANY brand in that density range. In other words what you buy additionally base on price, not name.

Andre

AVare:

703 - can be used on side wall first reflections without grazing angle reflection (i.e. it still absorbs)

705 - may work barely perceptibly better on the rear wall for axial modes and first reflections, although not as good at oblique modes. Since it's denser, it's much easier to edge bevel successfully. It shouldn't be used on side wall first reflections due to increased grazing angle reflections.

Both - we tend to use relatively small orders (a normal order of 703 is an 18 wheeler full i.e. about 2000 ft^3 or $30,000.00) so finding such a small quantity of two models in stock for a reasonable price is just one more hassle. Add to that the hassle of keeping the two separate at the job site and running out of one or the other.

I believe these comments are portable to Rockwool and other materials. Rockwool is denser for the same absorbtion, so perhaps a mid range Rockwool might be an optimal choice for edge bevel cuts, but I don't know.

Z60611:

I'm not clear as to why you addressed the comments to me. Your comments and my comments are basically the same.

Ever so easily confused;
Andre

AVare:
Sorry about that. I started writing to you, and then a couple of edits later it wasn't the same post. Of course you know all that. Heck, you wrote some of it in the prior post.

Thanks to both of you guys for the useful info.