Originally Posted by Jay5298
Would 4" thick 705 unfaced be sufficient enough for the bass traps, or does the FRK backing make a difference.
I thought that 2" thickness would be enough for the mids and highs.
I want to keep the ceiling treatments as thin as possible due to fairly low ceilings.
In general, the goals are:
1) Control reflections, but don't go too far and lose all of them.
2) Absorb across a wide range of frequencies, typically by having thicker panels.
The reason for the FRK, mostly, is that you want as much bass trapping as possible, BUT you also don't want to absorb too much of the mid and high frequencies. The FRK acts to reflect the mid and high frequencies, so you don't "overdamp" your room (make it sound lifeless and inert).
So if you use the FRK, it doesn't really help with bass trapping, but it prevents problems with other frequencies.
That said, you can probably be okay without it in your scenario, if you need to not put it on/use it.
2 inch thickness is better than 1 inch, but not as good as 3" or 4" in most situations. In fact, getting too thin arguably causes more harm than good at some point, since it only absorbs a very limited range of frequencies and the other frequencies are inconsistently tamed. If you can do 3" or set the 2" panels off the wall with an air gap, that's better than just a 2" panel on the wall. But a 2 inch panel on the wall is better than no panel at all.
I understand room limitations. Most of us have those issues. So if you have to compromise on the ceiling because of that, don't sweat it. Just remember to be judicious with how much surface area you cover. Hit the key points, and don't just swath it around everywhere.