Proper Room Acoustics/Designs

Is Dennis' room dimensions recommendation in the 1.0 X 1.6 X 2.6 ratio?

Actually 1:1.6:2.33, but those can vary, depending on the size of your low frequency drivers. He advocates building a room inside a room, with all 6 parameters to be 12 inches deep (front, back, sides, floor and ceiling). He then builds Carbon filters/diffusers as well as absorption devices in the walls. It will be an ambitious project, but if I can get it right, it will be well worth the money. For the first time, I will be able to hear ALL of the notes attack, as well as decay. I have so much energy in my room right now, with 2 JL Fathom 13 subs turned on at low levels and low roll-off points it sounds muddy. All these years, I've been utilizing tube traps etc, to try to clean up my room to no avail. He has some interesting Youtube videos you may want to check out.

I'll look Foley up. J. Gordon Holt specified that 1:1.6:2.3 ratio long ago, which I took as Gospel for years. Then everyone (Cardas, etc.) starting recommending 2.6 for the last figure. 2.3 seems better to me, being a prime number. I would gladly take either, but if you're building you get to choose.

I'm no expert, but I took a quick look at Dennis' wall construction and I'm not sure all this is needed to build a very good sounding room. Unless you're also very concerned about sound getting out of the room, a room within a room may not even be necessary. Seems to me a couple slabs of Sheetrock sandwiched together with something like Green Glue and then attached to the studs using resilient channels (all very cheap by the way) may accomplish much the same thing without having to do all that extra construction and/or having to buy all those presumably expensive charcoal bass traps and diffusers. I'm not saying Dennis doesn't know his stuff or that his method doesn't work, but also consider he's in the business of selling sound absorption products and there are other proven ways to go. As I mentioned on your other post, read Premium Home Theater by Earl Geddes -- invaluable information to know regarding room design and sound optimization, and I consider it a must read before taking on a project of this magnitude.