Typhoon,
The things you are considering will be good for sound isolation.
Modifying your ducting for an "S" shape is recommended by alot of theatre enthusiasts and seems to work well. The more curves sound has to travel through, the less it will persist through the curves. 4 Products from
Owens Corning should be sufficient for duct silencing.
Concerning your resilient channeling. There is a better method that has spread like wildfire on the DIY theatre called green glue.
It is more effective blocking LFE than resilient channeling.
If I had known about this product prior to putting up my drywall, I would have used it. When I started my basement 3 months ago, I didn't know anything about sound proofing. I just started the drywalling and THEN i started researching. Should have done it the other way!
In any case, go
here for a comparison of green glue vs resilient channeling. It yeilds better STCs and cost benefit is very high. Go down about half way for the GG vs RC discussion.
Double 1/2" drywall on each side of the wall with resilient channel on one side with insulation will yield 45 STC.
Single 5/8" on one side and double 5/8" with GG on the other side with insulation will yield an STC of 52. And its much easier to use I think. Just regular drywalling with a double layer of drywall with GG sandwhiched in between on the sound side.
Check out that website for all the info you needs, its really quite an amazing product.
Below is a chart of the 2 comparisons.
"A comparison of resilient channel and Green Glue assemblies with 3 total layers of 5/8” drywall, taken in the same lab.
The RC was verified by the lab to be 25 gauge (which is appropriate), and it was properly installed.
Note that while the RC, like GG, yields a very good STC, its low frequency performance is far worse. Remember that, in theory, doubling the mass of the wall would cause a 6dB low frequency performance increase, all other things equal.
If the channel was not properly installed, this difference is likely to be even larger"
