Originally Posted by Guz
Hello everyone, long time lurker here !
You guys have decided me to build some basstraps for my basement/rehearsal room.
I've got everything covered except for what kind of rockwool I should use.
I can get 5.5" Rockwool Delta 212 at a decent price and I was wondering if that would be good for a broadband absorber (I need to focus mainly on the bass, but other frequencies need to be tamed too).
I tried to search the subjet but nothing useful came out.
If that particular kind of rockwool isn't good, what would you guys recommand ? I'd like to stick with the brand Rockwool, I'm in no way affiliated with them, but that's the easiest brand to get around where I live.
I have to say in the UK I have never heard of that particular "Rockwool" product?
I have attached a Rockwool datasheet for the most popular products used for porous absorption in the UK, of which RWA45 and RW3 are arguably the most used and most useful.
The data you really need is gas flow resistivity (GFR) which is generally not given by the manufacturers. You can make an estimate
from density data however, there are other factors (porosity, tortuousity for a start) that affect gas flow.
I would say you are better off using a product for which there is
plenty of test data by searching out gas flow resistivity on this forum. As a general guide for bass absorption with porous material you are looking at thick, low GFR (ie not too heavy density) material spaced off the wall to give an air gap behind. By reading around this forum you will find that 6">8" "pink fluffy" loft type insulation has apparently produced reasonable results. Take a look at this calculator which gives indicative comparison between different options: Multi-layer Absorber Calculator
Repeating advice that I normally offer, the right way to approach your problem is to measure the room with an analysis package like Room EQ Wizard (free from hometheatreshack). Then treat the space accordingly by identifying the problem walls and, importantly, the correct areas
of walls/ceiling to treat. If you are trying to treat axial mode issues in particular you maybe better off looking at pressure
based, panel type absorbers.