taking 38% of that, I get 6.27, or about 6'-3". I measured that to ~ mid chair, as I tend to sit forward while working. These were just starting point measures. New walls have not been built, just trying to rough this out. Are my calculations or approach incorrect ?
OK, sounds right to me! As long as you did the math and got things roughly right, that's fine. It's probably just an optical illusion that makes the char look further back.
definitely consider this. But to keep it interesting, I'm also thinking of a new monitor system to put in this room.
I'd start by selecting your monitors, then build the room to suit them. What new monitors did you have in mind? It would be good make sure in advance that they can be flush mounted successfully!
I'd like to improve the isolation from the upstairs [living room], but it appears that I can only do so much.
You should be able to get reasonably good isolation, but it will cost you a little bit of height, something around 2", or maybe a bit less, depending on how much you need. Have you done any testing yet, to see how loud you are in that room, and how quite you need to be upstairs? I mean, using a sound level meter to measure the actual levels, not just guessing...
By the way, you probably already know this, but just to make sure: isolation is an "all or nothing" proposition. You can't just isolate your ceiling... you have to do the walls too.
The only reasonable thing I could think of is line a layer of 2" ridged fiberglass up there first, then fill the rafters to the bottom with fluffy pink, and then fabric cover to the rafter bottom.
That won't isolate much at all: it will
treat the room very nicely, but it wont help to
isolate it. Two different things...
I'm thinking that your best bet is with either resilient channel or with Rod's technique of interspersing your new ceiling joists between the existing floor joists, and aiming to get the top of your drywall just a half inch or so below those existing joists. That would eat the least amount of height possible. One other option is "inside-out" construction for your roof, but that might put the joists too low for comfort.
I've enclosed 2 photos of the 'center load bearing beam'. This is the main dividing point between the CR wall and the rest of the basement.
When you say that you have "ceiling height: 7'9"" and "floor to rafters: 7' ", what exactly are you measuring? To the bottom of your "'center load bearing beam'", or to the bottom of the joists above, or to the underside of the floor above?
I've been kinda talked out of that, and now have the pump located in the rear-right corner. I was concerned about corner symmetry, especially for corner bass traps at the front.
I think your orientation is fine like that, with the pump at the rear. I wouldn't change it.
Located 'outside' this new room are the typical basement 'stuff'. Washer/dryer, dehumidifier, sump pump and plenty of water pipe on THAT side. I certainly would like to have good isolation from those things AND try to keep my 'noise' from becoming an issue in the rest of the house. My typical monitoring level is ~75-83 dB. And, of course, when ya get a nicely controlled room, it can be nice to turn it up at times
Yup! OK, so I imagine you are looking at peak levels of around 90 to 95 dB, for argument's sake, but it would be good to check that with an actual sound level meter. Then also measure how quite you need to be in the rest of the house (and how loud that "basement stuff" is, when it all runs at once!). That will give you a rough goal for how much isolation you need.
My contractor thought that the two new walls would be 2x6.
Probably right, but I'm assuming he knows how to build an MSM wall? When he says "2x6" does he mean 2x6 on each leaf, or is he talking staggered studs? You might find that 2x4 is enough of you are talking two-leaf walls, but staggered 2x4s on a 2x6 base would be a reasonable second choice.
The two concrete walls using 2x4" as furring strips [insulation in between].
Bad idea: that will not decouple the inner leaf from the outer leaf! The inner-leaf frame cannot be attached to the existing concrete walls at all! It has to be built as a separate, free-standing stud frame, and cannot touch any of the existing structure at any point (except the floor, of course). Anything that bridges the gap between inner-leaf and outer-leaf will destroy (or at least seriously compromise) your isolation. the inner leaf has to be totally decoupled from the outer leaf, if you want good isolation.
However ... after reading Gervais book on interior walls, I think we'll be changing that. For the new walls: the 2 separate frames [2x4] with 2 layers of drywall, and each wall filled with insulation may give better results.
Yup! absolutely. Two-leaf MSM is the way to go. Full "room-in-a-room" design. Fully decoupled.
oh ... that pump area needs to be open from the other side of the basement.
Another reason to put it outside of your wall, not inside...
Question: That other room at the bottom of your diagram, directly in front of the window from the CR: Is that going to be a vocal booth, or a storage area, or what?
Here's a wild idea: How about of you rotate your CR 180°, slide it back so that it uses the space occupied by that "booth" room, then put the "booth" room at the other end, next to the sump pump, and make the "booth" room a bit smaller so that the pump sits just outside the door...
Not sure if I explained that well...
- Stuart -