I think you are being a bit unrealistic with your sound level estimations!
...by the time it reached their actual living space.
I think you'll find that most noise regulations specify measurement at
your property line, not the other guy's living room.
That's where the cops or municipal inspectors will measure, if they get a complaint. Not in someone else's kitchen or bathroom: it will be measured at your property line. Your responsibility is what leaves your property, not what arrives at some other guy's refrigerator. It is not his responsibility to have sound-proof walls: it is YOUR responsibility.
Next to closest neighbor's wall: 70 max
If I were getting a level of 70 dB at my front wall from my neighbor, you can bet I'd have the cops over there in five minutes! That's darn loud. That would be downright annoying during the day, and totally unacceptable at night.
Assuming the neighbor's wall is similar to my own wall structure, there would be an additional 40dB reduction by the time it reached their actual living space.
His wall is irrelevant: What if he likes to leave his doors and windows open all the time? What if he likes to sit out in his garden without being disturbed by your noise?
You CANNOT take into account anyone else's construction. What matters is the loudness of the sound as it pass over YOUR property line.
...
So assuming the property line is about half way between your house and theirs, that puts it at about 8 feet from your wall. So you need a total reduction of 115-40 dB = 75 dB (assuming your local noise regulation specifies a limit of 40 dB). You might get 3 dB at 8 feet, so call it 72 dB. That's what your wall needs to give you: 72 dB of isolation.
So that places your isolation goal at 72 dB.
Obviously I want to make this number zero
Actually, you can't do that, nor do you need to. A level of zero decibels means that the sound is just audible in total silence. It represents a pressure difference of 0.0022 pascals, which is the theoretical threshold of human hearing. So it is possible to have sounds that quieter than that, and as far as I know the quietest room in the world was recently measured at -9 dB (yes, negative 9 decibels, or about half as loud as the quietest sound anyone could possibly hear). But in reality, that doesn't occur in nature, nor in residential communities. The ambient level will be substantially greater than that, probably around 30-something at the quietest time of night. It's normally hard to distinguish sounds that are more than 10 dB below ambient, so if you really wanted to get things "silent", you'd only need to get it down to 20 dB.
What do you guys think? Does this seem reasonable given the studio is properly built?
I think you CAN get 70 dB of isolation, if you do it right, and I also think that 40 dB of isolation is totally insufficient, if you want to keep the cops away!
Stuart, in regards to the bathroom being in the iso booth, this is because the toilet and sink location are fixed. ... Also the door/load-in needs to be on the bottom right
OK, that makes sense: so those are fixed. Main entrance at bottom right, bathroom at bottom left.
Is that a logical assumption?
Yup! You don't want to have to cart heavy equipment and instruments around the back of the building, and then have to walk through other rooms to get to the LR. So yes, it makes perfect sense to keep your main entrance door close to the parking area. Which means it makes most sense to have the entrance to the LR at the bottom right.
But you could still rotate your CR 90° right, and then put the iso booth in front of it, or on the other side if you do a corner CR. That would not reduce the size of the LR, and might even improve the layout.
I have posted a new layout below
I see that you have added the missing wall for the CR, but you are still missing one wall between the iso booth and the bathroom. There's only one leaf there, which means that the bathroom is actually located in the air cavity between the CR walls! (acoustically speaking)And also the cavity between the LR walls. and also the cavity between the iso booth walls.
Is 15º enough of an angle on the control room walls to allow for a proper RFZ?
It might be. Or it might not be. The only way to find out for sure is to ray-trace. It's a pain, but there's no other way.
and is it vital that the ceiling be 15º as well or will an angled cloud provide the same function?
A cloud will suffice, if you have no choice, provided that the cloud is hard-backed and also angled steeply enough. But a hard backed cloud angled steeply enough is pretty much the same as just angling the front of the ceiling...
Also, how important is it that the rear of the control room be symmetrical? Can slight asymmetry be fixed with proper acoustical treatment?
Rear symmetry isn't critical, unless you are doing surround sound (5.1, etc.). So from that point of view, the slight "kink" in the rear would not make much difference. You could do that.
However, I don't understand the reason for moving the door to that location: Why not just put it in the middle of the CR side wall? If sight lines is your concern, then put glass in the door and windows on either side. The location of that door right now is right where your rear bass traps should be in the control room. That is prime real estate, the best possible location for bass traps. If the door is taking up that location, then where do you plan to put the bass traps?
Also, you do not need to splay the entire walls: you only need to splay enough to guarantee that the RFZ is complete. Usually, that would mean that you only need to splay the walls as far back as your head (once again, unless you are doing surround: that makes things a bit more complicated). That would allow you to have a greater angle at the front, and a much wider room at the back.
in a soffit mount configuration...I can't find any recommended distance in the user manual so does anybody have any suggestions in how I should set them up? Is there an ideal distance for 8" speakers?
It's not so much the size of the speakers that matters (although for very large cabs, it is important), but rather the geometry of the room. EBU recommendation is for the speakers to be on the circumference of a circle where your head is in the middle, and the radius is 2 to 4 meters (roughly 6.5' to 13'). In turn, your head should also be roughly 38% of the room depth (distance from front wall to rear wall), and both your head and the speakers should be 1.2 meters above the floor. When I say "your head" that actually refers to "your ears". And when I say "height of the speakers" that actually refers to the acoustic axis of the speaker, not the top, bottom or center of the speaker. The acoustic axis is an imaginary line that pokes straight out the front panel of the speaker, at the location from which the sound appears to emanate. It is always located on another imaginary line that joins the center of the woofer to the center of the tweeter, and is generally much closer to the tweeter. The exact location might be in your speaker manual. Some manufacturers are smart enough to publish that data.
The speakers should be angled such that the axes intersect a few inches behind your head
I would assume its really up to me as long as I have the correct equilateral triangle that allows for a good mix position (approximately 38% from front wall) within the given room dimensions...is my thinking correct here?
Welllll......, yes and no. It is "up to you" in the sens that you'll have to fiddle and nudge things around to make them all fit, but you'll find that you don't have a lot of options, once you take into account all of the above!
When you start trying to make all that work, you'll start to run into issues that will have you banging your head against the wall, since some requirements will be in direct conflict with others. So you have to compromise: you might need to angle the speakers more than 30° to make the geometry work, and that's fine. You might need to move away from the famous 38% location, and that's fine too. You might need to bring the speakers closer together or further apart, or move your head. It ain't easy to make all that work out! The best you can do is to find a location that is a good compromise on all of the above. But you won't have much freedom to chose the listening distance.
If you are interested in the math, here's the diagram from the EBU recommendation:
5.1-EBU-layout.jpg
(That's for 5.1, so just forget the center speaker and the two surrounds.)
where it shows double sided doors there will actually be single reinforced "superdoors" instead...
Are you SURE you want to do that? Superdoors are HEAVY, and EXPENSIVE to make. And they force you to compromise your isolation by tying together your leaves at the door frame. They have their place, but I think you'd find that a pair of back-to-back doors would be easier.
the drawing program just doesn't let me do that.
Try switching to SketchUp! It's 3D, not 2D, and allows you to any damn thing you like!
- Stuart -