A few things:
1) Foam, unless it is treated with fire retardant, is very dangerous to put up on walls or ceilings. The old Tasha Records studios in Libis was burnt to the ground in a matter of minutes because the wall and ceiling treatments were all untreated foam. The case of a bar in the US where a band was playing, lighted up some fireworks, got the acoustic foam treatment into flames, and several died.
2) The one that was shown in the picture is from Sonex, not available locally. Sonex is fire-rated and at the same time, has a spray type fire retardant that you have to use on installation.
3) RockWool and Glass Fiber (also known as Glass Wool, Fiberglass, Mineral Wool, etc.) have almost the same absorption coefficients. The difference is the price. Rock Wool is a bit more expensive. Also, their density rating differ. You can get both in 1 inch and 2 inch thickness. Normal thickness used in acoustics is 2". 1" and 2" mineral fibers have differing absorption coefficient. If you want to absorb more LF, go for the thicker one. I have used 4" thick glass fibers to have a better LF absorption and higher abs. coefficient in the HF.
4) In a studio, you use absorption, difusion and reflection to control the frequency response of the room. You compute the RT60 based on the absorption coefficients of different materials. Typical reverberation of studios are .2 to .35 seconds for control rooms and .2 to .7 sec. for studios, depends on how big your space is (volume) and what you want your studio to be used. For spoken word, a short RT60 is preferred. For orchestral, like strings, brasses, and choirs, the higher the RT60, the better.
5) You use bass traps or LF absorbers to control the LF energy of the room. You design these traps to make the bass response in the room tight and punchy. You can either trap the LF energy with big absorptive cavities (these are the real bass traps), or use panel absorbers - combination of wood panels and glass fibers, or Helmholtz resonators, boxes with holes or slats with fibers inside. You just do not put in LF boxes. You have to compute for the room response, other wise, it will just be a waste of money.
These matters will be discussed in our projected seminar on the recording process, just to let you know.
FWIW
