I've been doing loads of research into how to soundproof my eventual basement HT. HT is in the basement and will be rectanglar. At this point I have not got the size 100% defined, but it shouldn't matter at the moment. The HT will be in one corner of the basement so 2 of the walls will be exterior walls and the other 2 will be freshly constructed interior partitions. I plan on the following soundproofing approach: 1. fill ceiling and walls with Roxul Safe N'Sound insulation 2. use sound isolation clips with resilient channel on both walls and ceiling 3. 5/8" drywall on resilient channel (will use 5/8" on opposite side of interior partitions as well) 4. acoustic caulk where required My question is given that 2 of the walls are exterior walls, do I have to put the same effort (i.e. isolation clips and resilient channel) into them, or will the cement wall act enough as a sound dampener? I'm concerned about the sound going upstairs of course. Appreciate any input!! Any comments about my plan would be great as well!! Maybe I don't have the best approach in mind!?