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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.
I will take a look at Earl Geddes book. The reason Dennis wants the 2 x 12's all over, is so no additional acoustic panels are needed. I guess I need to post a picture of my current room. It has around 20-25 sound absorption panels on walls and ceiling. The room has a kinda Cathedral ceiling, but there's about a 10' section of the ceiling at the top, that is parallel to the floor. I had a dropped ceiling installed, with about 6" of fiberglass on top of the tiles. It really helped a lot, but the room is still muddy in the lowest lows. I also have 4 ASC "like" bass absorbers placed strategically in the room. The highs and the mids are great, but still lacks in the lower bass frequencies.
The room within a room seems it might be excessive for domestic systems. That may be more justified for recording/monitoring room designs.
A less expensive option might be utilizing 2x4 studs on 2x6 sill plates. Then stagger the studs so every other one contacts an opposite wall (while maintaining 16" spacing).
Not sure I agree with the double drywall either. Yes that may "tighten" the wall and ceiling surfaces but will it be too "dry" sounding?
Lastly, from Jim Smith's book, he recommends installing 2x4s on their side on top of a concrete slab, then overlaying wood floor on that.
A certain amount of flex can support a constructive balance in a room.
Yeah, since bass seems to be your biggest issue I'd have concerns over the proposed design. The double drywall will do little or nothing to absorb long bass waves, which means they will continue to be reflected back into your room. Secondly, since the bass diffusers are located behind the double drywall I don't see how they could solve a problem that would already have occurred inside your room. Seems like that design would possibly help reduce transmitting bass outside (or outside sound getting into) your room but not do much for the sound inside your room.
I must have not done a very good job of describing the room. There won't be any drywall-at all. 2 x 12's on all 6 walls, floor, etc. Sound diffusers and bass traps will be incorporated in the walls where ever is needed. The bass traps are like Hemholtz devices, with the diffusers being vertical/horizontal slats. The outer walls will have material over them. Just look up Dennis Foley, to see his designs.
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