common room be a somewhat live end / dead end design with the desk at the dead end and some diffusion in the live end.
LEDE design (Live-End, Dead-End) was a concept from the 1970's about studio design, that is no longer used. It was found to unpleasant to work in LEDE rooms for long periods, and the results weren't that good anyway. Unfortunately, the term found it's way into many books back then, and sort of got adopted by common mythological processes, so it is still circulating as though it was the best things since sliced bread, when in reality almost no professional studios are built as pure LEDE designs any more, and haven't been in many years.
Extensions to LEDE, and modifications of LEDE, is where we are today with concepts such as RFZ, design, CID design, NER design, and other similar 21st century acoustical design philosophies. Rooms based on these concepts work much better than the old LEDE rooms, so it would probably be better if you were to use one of those as the basis for your studio.
I thought I would get the outer barrier walls built and then run REW tests before committing to a design for the inner leaf walls.
Actually, there's no such thing as a "barrier wall". Isolation is accomplished by having a two-leaf wall. The "outer-leaf" and the "inner-leaf". It is not that the outer leaf provides some isolation and the inner-leaf provides some more: very far from it! In reality, both leaves act together as a resonant system to provide the isolation. It's a case of "the whole is greater than the sum of its parts": You cannot simply add up the isolation of the two individual walls and think that this will give you the total isolation: that won't even be close. With this type of construction ("room in a room"), the two leaves do not act individually, as separate entities: rather, they act together, as a combined system. This is very much like the suspension system in your car: it consists of the wheel, the spring, the shock absorber, and the chassis. These parts also do not act individually, but as a system. If you take away the shock absorber, you no longer have a suspension system. If you take away the spring, you no longer have a suspension system. All of the components need to be there in order to work. If you have only a shock absorber but no spring, then you don't have a partial suspension system that sort of suspends... You have nothing. You can't test that to see how well it works, then try to extrapolate from that to see how it might work when you put the spring in, because the spring is necessary for the suspension system to work. Ditto for the shock, wheel, and chassis. It only works when all parts are in place.
The same with your isolation system: if you only have one leaf erected, then you don't have an isolation system: you have nothing. It won't work until you have the inner-leaf in place as well, along with the insulation in the air cavity: only then will you have a complete isolation system, and be able to test it.
Going from a single-leaf system to a two-leaf system moves you from one set of acoustic equations to an entirely different set of acoustic equations: they are very different systems with very different properties, and you cannot use one to predict the other.
That way if I needed a slat wall or hanging bass trap setup for a particular set of frequencies, I'd have an opportunity to build to that.
You seem to be making the very common mistake of confusing isolation with treatment: they are two very different aspects acoustics, and use very different materials and methods. Isolation is about reducing the amount of sound that gets into and out of your studio, and involves large, thick, massive, heavy, rigid, stiff, building materials, while treatment is all about dealing with the sound moving around inside your room, and involves mostly light, softy, fluffy, porous, materials. Isolation is not treatment, and treatment is not isolation. Your two-leaf walls are isolation ALONE. Your slot walls and bass traps are treatment ALONE. Neither affects the other.
Yes, you can incorporate treatment devices into the same walls that are also part of an isolation system, but that's a different matter entirely. You FIRST have to complete the entire 2-leaf isolation system, THEN you can decide what treatment needs adding to the inner-leaf.
In terms of mixing accuracy, I know that you feel strongly about certain aspects based on reading your advice to others, but I'm confident that if I do my best with what I have, I'll be able to create good mixes.
Good luck with that!
I don't mean that in a derogatory manner, but rather a humorous attempt to say that what you expect is not what will happen in reality. You say that you have been mixing in lousy acoustic conditions forever, and you have learned to live with that, but since you've never had a place with great acoustics or great isolation, you don't really know what you are missing! Once you start working in a studio that has vastly better acoustics than what you are used to, you will very quickly start noticing things in your mixes that you never heard before, and you WILL want to fix them... and you'll also want to have even better acoustics, because you'll sense that there is still more in there that can be fixed, but you can't quite make it out....
I have been mixing in poor environments my whole adult life and I know the pitfalls. My goal is not to make a perfect mixing environment, but rather to simply reduce the number of trips out to the car to get a mix done to my liking.
Let me put it this way: why do you want to do that at all? Since you have the opportunity to do this right, and completely eliminate those multiple trips out to your car, why not do it?
In essence, you are here saying: "I know you guys really like prime fillet mignon with a spectacular cream of mushroom sauce and a fine Chilean Cabernet Sauvignon, but really, I think three-day old dry hamburger and a stale coke is MUCH better for me!" ...
The first time you try the steak, you'll NEVER want to go back to moldy burgers and flat coke...
OK, so I understand what you are really saying: "I don't have enough money to eat steak every day". Neither do I. But I sure don't want to eat at McDonalds every day either! And there are cheaper alternatives than eating steak every day, that are still way better than eating McDonalds every day, while still being delicious and nutritious.
Put back in studio construction terms: You are concerned about the extra cost of having a great room, but in reality if you can afford to do what you are proposing in your drawings, then you most certainly can afford to have a very, very good, room, even if it isn't exceptional. It can at least be prime beef BBQ every day, instead of junk food.
In terms of the ceiling height in the drum room, I was thinking I might do the ceiling tight to the joists with a cloud underneath.
I thought that isolation of the drums was the most important issue? What you are proposing provides no isolation for the drums... A ceiling "tight to the joists" does not isolate: rather, it provides a direct flanking path for the sound f the drums to get into the house structure itself, and therefor into every other room... The cloud below will help a bit with the acoustics inside the room, but it won't do a thing for isolation.
Here's an experiment you can try: Get someone to play your drums loudly for you, while you are standing a few feet away. Now take off your jersey and hold it out at arms length between your head and the drums. Hear the difference? That's roughly how much difference the cloud will make to isolating your drums...
I would then decouple the walls and ceiling in the common room where I don't have the concern of comb filtering overheads.
But that isn't what you are showing in your latest drawings! You are showing only partial isolation of the live room, and of course in acoustics, partial isolation is the same as no isolation at all. It's the same as the "fish tank" analogy: you are showing that you want to build an aquarium, but you only want to have glass on two sides of the frame, and leave the other two sides open... how well will that aquarium hold water?? That's the exact same situation you re showing in your current design...
Or, perhaps skip the second leaf in there and trade some bleed through for more absorption and clearance.
If you skip the second leaf, you do not "trade some bleed through...". Rather, you trash your isolation completely.
A single leaf wall is governed by the equations of physics known as "Mass Law", which say basically a single leaf wall is a very, very lousy isolator, especially for low frequencies, and especially for loud sounds. On the other hand, a two-leaf wall is governed by an entirely different set of equations, including the ones called "MSM resonance law", which is a whole different ball game. There is no relationship between the two sets of equations: you cannot derive the MSM equations from Mass Law, because they describe two entirely different principles of physics. A single-leaf wall works in one way, and gives you lousy isolation, while a two-leaf wall works in an entirely different way, and gives you much, much better isolation.
Here are the basic equations for both cases, so you can see the difference. Mass law:
TL(dB)= 20log(M) + 20log(f) -47.2
M is the surface density of the wall, and
f is the center frequency of the third-octave measurement band
There's a simplified empirical version of Mass Law, which goes like this:
TL = 14.5 log M + 23 dB (where: M = Surface Density in lb/ft2 )
For MSM walls, you need to start by figuring out the resonant frequency, from:
F = (1/2pi) * SQRT (Rho * c^2) [(m1 + m2)]^.5 / [(m1 x m2 x d)]^.5
Which gives you the point of minimum isolation, then apply a curve of 18 dB/octave up to the coincidence dip, then a curve of 6 dB per octave beyond that.
It's an entirely different thing.
These are the points where I could use some practical advice.
If you want good isolation for any of your rooms, then it has to be done either as an extremely massive single leaf, or as much less massive 2-leaf MSM system. There are no other options, unfortunately. No magic materials, or esoteric methods... Your only options are one-leaf, and two-leaf. One leaf is lousy (unless it is very massive), and two-leaf is much better, but more expensive. I wish there were better news I could tell you, but sadly there isn't.
I'm not concerned with cars pulling up outside or flushing toilets. It's not a commercial operation where someone is paying me by the hour. If I have to re-do a take because a toilet flushed, it's not a big deal.
OK, then you probably can live with less isolation than a high-end studio would need, so as long as you are OK with that, and don't mind the lousy isolation if a single leaf, and you do realize that there's nothing you can do about it apart from building a second leaf to complete the MSM system, then that's OK. If your music won't be disturbing others, and you don't mind them disturbing you, then lower isolation goals are reasonable.
Thanks again for your help. I'll try to post some pics of the space.
That's actaully a very nice looking space, with some god possibilities!
Here are the requested pics. I hope you can make things out. Excuse the mess. It's become a catchall
Mess? What mess?!?!? That's not a mess... If you want to see a REAL mess, take a look in my shed.... .)
So, after a little more thinking and some revisions, here is my current plan.
It's looking MUCH better! A great improvement.
What I would suggest is turning the orientation of your control room around 180°, so it faces the drum booth. There are several reasons for that: some practical some acoustical. Mostly, it gives you sight lines all ways around you, so you can easily see into (and be seen from) the drum booth and the live room. And acoustically, the room should never get narrower towards the back; it should only ever get wider, or stay the same. You'd have much better acoustics like that.
I would also definitely make the CR more rectangular and symmetrical: there are ways of doing that without the pole being too much of an issue. From the photos, it looks like you might even be able to move that pole. Call in a structural engineer to take a look at that, and tell you how / where it could be moved. It's not such a big deal as it sounds. I've done that for home studios before, and as long as you follow the instructions of the structural engineer, it can work out great. It's worth looking into.
Apart from that, it looks fine.
- Stuart -