What can you guys suggest for cheap sound insulation? I do a lot of mixing in my room and hope to be recording some spot FX.My room is small and hard walled.
All the best
Rock wool covered with cloth works well. But you don't want to just make the room dead or you will find that you mix everything a bit too live to compensate.
Are you trying to deaden the room acoustically, or reduce external sounds from outside?
In terms of reducing exterior sounds, 2 materials of different density will provide a good start, as the above answer said.
Also consider the sounds you are recording, and whether you can use dynamic mics which will pick up less room 'sound' and more direct sound. And make sure you record/mix from the right position, to avoid the problems with small boxy rooms and standing waves/bass problems/muddy imaging etc.
As far as treating the room for interior acoustics/reflections, I also second fabric wrapped mineral wool. Just did this for my own bedroom studio, used this product from Lowes:
The eight 2'x4' batts go a long way. They are thicker than the traditional 1" or 2" thick fiberglass traditionally used in acoustic wall panels (which you can also get in panels from your local insulation supplier), but a quick frame made from 4-by (3.5 inch) 3/8" thick craftboard (pine), fabric to wrap it, and a staple gun, makes for some nice lightweight panels. It's really easy to cut with a serrated bread knife. You could use masonite on the back of the panels for a complete finish, but I opted for 1/16" thick cardboard/illustration board (kind of like matte board) instead for less weight.
Another option away from fiberglass these days is the recycled bluejean insulation material. This stuff is so touch friendly that you don't even need to wrap it if you don't want: