45 to 50 db of isolation for the single leaf walls will be ok.
You really should take another look at the equations of Mass Law: To get 50 dB of isolation from a single-leaf wall, they would have to be of solid reinforced concrete, 18" inches thick! The equation for empirical mass law is very simple:
TL = 14.5 log (Ms * 0.205) + 23 dB
Where: Ms = Surface density in kg/m2
The density of concrete is roughly 2000 kg/m3. Surface density for a 46cm thick (13 inches) solid concrete wall (high-density reinforced concrete) is roughly 900 lg/m2, which works out to a bit over 55 dB.
So if you want to do all your walls with single-leaf, then you should increase your budget even more, to account for all those truck loads of concrete...
On the other hand, if you do proper 2-leaf MSM walls, you can do it in much less space with just simple timber framing and drywall, for a fraction of the cost, and get the same or even better isolation.
Double walls would be my choice for all the interior walls but I only need that much isolation between the control room and the live room.
I think you don't have a good grasp of how isolation works: you cannot have a 2-leaf wall around only part of your room. Isolation is "all or nothing". Trying to isolate only one wall of a room is like trying to build an aquarium with glass on only one side, and using paper for the other sides. The basic concept of isolation is that the entire room has to be done to the same level, all over, because sound will always take the easiest path out. If you build three marvelous walls and a marvelous ceiling, but didn't bother with the fourth wall, then you wasted a huge amount of money on the ceiling and the other walls, because sound will go through the weakest wall, totally ignoring the other walls. And if you do all your walls and ceiling perfectly but just use ordinary glass for the window, then you wasted a huge amount of money on all the rest because the glass is the weak point, and that's where the sound will get out. And if you put in proper laminated glass on the windows too, but skimped on the rubber seals around the doors then you wasted money on the entire room, because the sound will get out through the air gaps around the door.
The isolation of any room is ONLY as good as the weakest point, whatever that is. Right now, you are wasting a lot of money, time and effort with that "double wall in one place only", because sound will ignore it, and go right around it, over it, and under it.
In the Philippines they don't use drywall,
How about plywood? OSB? MDF? HDF? Fiber cement board? There are many alternatives to drywall. We normally recommend drywall because it is cheap, but if you can't get it then there are several other options.
Mix position should be about 10 feet from the front block wall.
No. For a room 31 feet long, the mix position should be roughly 12 feet from the front wall. 10 feet away puts your ears too close to the modal nulls, and probably also within some of the SBIR artifacts coming form the rear wall.
"Speakers are custom,.. "
OK, fine. Please post the dispersion plots for them, and the frequency response curves, phase response, and crossover details. Without that, it's going to be very hard to design a room for them! Are they active or passive? Photos would be good, too. How big are the speakers, and what is their power rating?
When I design control rooms, the speakers are the starting point. It is imperative to have all of the technical characteristics of the speakers so that the room can be designed around them.
Sight lines are bad... and might be fixed by adding 2 more windows to the 4' sections of the front control room wall.
Not really, because those are your speaker soffits! Unless you build your isolation walls from glass and have the speakers flush-mounted in that, there's really not any way to have windows in the soffits. It is possible to do that (make glass isolation walls), and some really high end studios have actually done that successfully, but its rather complex to figure out and build, and pretty expensive to do. Thick laminated glass is very expensive, even in small pieces, and to use it as a soffit infinite baffle, it would have to be custom made with the exact right size and shape of hole in the middle, to fit the speaker through.
Unless your budget is pretty large, that isn't really feasible. The soffits will have to be done in the normal way, with thick wood on a very rigid, strong frame.
That's a Double Wall between the CR and Live Room..
... and as mentioned above, that's a waste of time, money, effort and space, since the rest of the walls are not isolated at all.
The brown lines are framed walls, 2" 703 with slat wood covering
Then there seems to be a mistake on your diagram, since it shows the speaker soffits as "brown lines"!
Soffit mounting requires a very massive, very rigid, very solid front baffle, with no holes, slots or gaps. Some people use concrete, some use several layers of thick plywood, OSB, or MDF. Some use brick. Some even use stone. But you can't build a soffit where the front baffle is a slot wall! It would not remove the speaker from the room in any acoustical sense at all (which is the entire purpose of soffit-mounting to start with), and indeed mounting speakers in a slot wall would very much color the sound unpredictably. So I hope that was just an oversight in the drawing, and the soffits are actually going to be something far more substantial than slot walls!
As for the separate slabs... that's the way they do it here.. they build the walls.. then pour the floors.
So there are no floors inside the building until the walls are up? That's a strange way of constructing. NOthing wrong with it structurally, and good for isolation, certainly, but it makes for a very uncomfortable, inefficient construction site, and I bet most slabs crack before too long... slabs should be poured on undisturbed native ground, suitably covered with DPC, sand, gravel etc. Pouring over a surface that has been mashed by construction equipment just doesn't seem smart, and the slabs will crack sooner or later like that, due to the lack of firm support below.
So you will have seven separate slabs (one for each room), and a network of foundation walls running in between them? I look forward to seeing photos of that, since it's unusual, and it would be good to have examples on the forum of how construction happens in other countries.
HVAC is not really available here... I will use 'Split Type' air cons and a fresh air system
Actually, that's exaftly what HVAC means! It stands for "Heating - Ventilation - Air Conditioning": The mini-split takes care of the Heating and the Air Conditioning, and your paired ducted systems with silencers take care of the ventilation.
What would be the proper angle for the side walls ? More or less angle on the walls?
More, for sure. The actual angle varies, according to each individual room, and the only way to figure it out is by "ray tracing", but you'll definitely need larger angles on the parts of the side wall between the speaker soffits and the mix position. From there back the angle is not so critical.
And the proper angle for the speakers and soffits
Speakers need to be angled inwards by about 30°, and the front baffles of the soffits need to be at the same angle, of course. Once again, the exact angle is different for every room, and it can be adjusted as needed, to a certain extent. You can go down to about 25°, or up to about 45° maximum, but you do have to be careful because changing the angle has a direct effect on the size and location of the sweet spot, and it also has a direct effect on where the mix position can be, how the walls need to be angled, and where the treatment goes (and even what type of treatment).
Control room design is all about making "trade-offs" and compromises. That's why it takes so long to do it. A small change in the speaker angles can actually mean that most of the room needs to be re-designed, and even something as simple as moving a window slightly, or putting the client couch in a different location can have an effect on how the speakers need to be set up, and angled. Control room design is very "iterative": you go around and around and around, tweaking and adjusting everything, until it is as close to neutral as you can get it. If you want a world-class control room, then that can take many days or weeks of work to get right. It depends on the basic design concept too: RFZ with soffit-mounted mains is not the same as CID with the mains on stands. It also depends on room size: many things are done differently for small rooms vs. large rooms. In very large rooms, speakers can be successfully mounted on stands far away from the walls, but for small rooms that is not an option: they must be up against the front wall. Large rooms can have diffusion as part of the treatment, small rooms cannot. Etc.
Control room design takes time, patience, and care, but for people who really want a world-class studio, it is very much worth the effort.
- Stuart -
