# Roxul "Cavity Rock" any good?



## bjs (Jun 12, 2008)

I've been trying to source Roxul's Rockboard 40/60 in Vancouver area for my dedicated HT/music room. So far no joy. It can be special ordered but minimums are 50 times what I want!

However a Roxul product called "Cavity Rock" is available in all sizes from 1" up to 5". From the Roxul website I can't see any difference between Cavity Rock and Rockboard 40 but I'm a little concerned about the comment regarding the "mineral wool structure effective for drainage".

I would appreciate expert opinions on:

1) Is Cavity Rock as good as Rockboard 40? The links are:
a) http://www.roxul.com/graphics/RX-NA/Canada/Product Literature/Tech Data/RockBoard40-5-15-08.pdf
b) http://www.roxul.com/graphics/RX-NA/Canada/Product Literature/Tech Data/CavityRock-4-28-08.pdf

2) What will I lose by doing all my trapping with 4lbs pcf material? Or should I keep trying to source the 6lb stuff for some of the traps? 

Note: I've actually found some Rockboard 80 (ie 8lbs) but perhaps that is too dense for anything since no-one seems to mention it on these sites?

3) It doesn't have FSK coverings. I'm thinking this will be a problem (correct?) so can I add something equivalent myself (if so what?).

Note: They will sell me FSK separately but it costs as much as the insulation!


If I go to all the trouble of treating my room I don't want to cheap out or get lazy at this stage and regret it later! So...the big question...should I be happy with Cavity Rock or do I keep on phoning! 

Input please!


----------



## bpape (Sep 14, 2006)

Using all 4lb density will be just fine. Don't sweat it. For your bass control, try to use 6" thick or chunk style.

8lb is good for places where you can't do 6" thick for bass control but other than that, save your money.

FSK as much as the insulation?????? I have it for $1 per linear foot at 42" wide. You can try a heavy packaging paper. It won't reflect quite as much in the upper mids but it'll be close if you bond it with spray adhesive. Just remember, you only want it on things in the rear of the room bass only absorbers. Nothing on the front wall nor on the reflection absorbers on the side should be faced.

Bryan


----------



## bjs (Jun 12, 2008)

Thanks for the help Bryan! The FSK price is due to the minimum size of the order. I'll pursue it further if I find my room too dead and worst case use heavy paper or something similar.

My initial plan is to chunk floor to ceiling in all four corners using 24"x17"x17" triangles plus 2" thick reflection absorbers on walls/ceiling. After that I'll stop, review results and decide the next step (if any).

I'm surprised Cavity Rock doesn't get more press since it seems to be cheaper and more readily available than Rockboard. I hope I'm not about to learn the difference the hard way...!:crying:


----------



## bjs (Jun 12, 2008)

Further to this...I emailed Roxul and asked for the difference between Rockboard and Cavity Rock. Here's their reply:

"Thank you for your inquiry. With regards to your e-mail, CavityRock is specifically designed for cavity walls and rainscreen systems as it has better water repelling properties. RockBoard 40 is a general purpose insulation board. This is to say that CavityRock could be used in a RockBoard application but not the reverse. The mineral wool fiber structure is the same."

Good enough for me. And the water repelling properties may come in handy when I look at my first REW plot after spending all this money on acoustical treatment... :heehee:


----------

