Choosing the right thickness and density of rockwool

Prorox SL 940 aka RHT 60

PRODUCT      THICKNESS  DENSITY               125HZ 250HZ 500HZ 1000HZ 2000HZ 4000HZ NRC MOUNTING
RHT 60 2"     (51mm)       4.4 pcf (70 kg/m3) 0.26    0.71    1.14    1.09      1.04      1.03      1.00
RHT 60 4"     (100mm)     4.4 pcf (70 kg/m3) 0.92    1.04    1.07    1.07      1.07      1.08      1.05
701, plain 4" (102mm)     1.5 pcf (24 kg/m3) 0.73    1.29    1.22    1.06      1.00     0.97       1.15 (on wall)
703, plain 4" (102mm)     3.0 pcf (48 kg/m3) 0.84    1.24    1.24    1.08      1.00      0.97      1.15 (on wall)
IIG 1280  2" (51mm)       8 pcf (128 kg/m^3)0.32    0.90    1.11    1.07      1.01      1.05       1.00
IIG 1280  4" (102mm)     8 pcf (128 kg/m^3) 1.11   0.91    1.03    1.03      1.06      1.07       1.00

I don't see comfortboard on here www.bobgolds.com/AbsorptionCoefficients.htm

Above 1kHz there is no significant difference (<.15 not significant).  

At 250Hz, OC takes the lead.  At 125Hz you'll be as good as 703.  

I put up RHT 60 2" because I use a 2" variant of IIG1280 doubled up.  I don't know for sure if that yields a 4" equivalent but I know it works.

In the low end thickness seems more important than density.  Ethan did a comparison test demonstrating the difference among panels with varying thickness, density and number.  Basically sheer number of panels is better followed by thickness and then density iirc.  

In other words, you should be good with RHT 60 4".  I'm not sure if the <0.15 not mattering being relevant to total NRC.  If that's the case then Bob (Gold)'s your uncle!  

Interestingly, gapping the OC 70X 16" makes it perform worse at 125Hz according to the chart.  

Anyway, hope that was helpful.

-m

I'm glad you got a good number of panels.  

Framing helps with hanging, protects the edges of the material and can aid in creating a tight finish with the fabric.  

Keep in mind that even with frames like mine, you will lose a certain percentage of the surface area (25% in my design - more for a full wooden frame).  

In general I would say to frame your panels.  You can check this vid on YouTube to see how I've framed mine or see here.  

Remember that adhering a thin membrane (such as paper grocery bags) to the room side surface of non-RFZ panels helps with low end absorption.  Simply, spray gluing paper or thin plastic (like the stuff your panels came wrapped in) to your corner traps helps them work better - verified (though sounds crazy).  If that's confusing then don't worry; you can always do it later.

Congrats on your new insulation

-m

Kill them.

jk. I'm surprised that the less dense material works better at 125Hz. It's effect below there is unknown but so long as you use a lot of them I doubt it'll matter all that much.

-m