Music Studio Design / Build using Natural Materials

[ryanluckey]

Hello everyone, this is my first post here although I have browsed the forum a bit in the past.

I'm currently about to begin construction of a new house with a music studio inside. I know that makes sound isolation more difficult, but in the region I live in (rural Brasil) this is important for security reasons.

Basically I'm looking for advice in two main areas:

1. Best practices for sound isolation with preferably natural materials (details on construction plans below)

2. Any other specific advice for sound isolation between studio / rest-of-the-house

Here are the project details:

Music Studio - Final Dimensions.pdf

In the floorplan (attached) you can see there are 3 walls that border the rest of the house (my main concern) and 3 that don't. Ceiling is slightly vaulted.

So far the construction plans are cement foundation and burnt cement floor, wooden columns at every corner (covered in plaster), earth walls (probably wattle and daub) with a thicker-than-usual layer of straw in the center of the wall and extra plaster all around, living roof (hardwood ceiling, on top of which is a water barrier, 10 cm of dirt, and plants), double-paned windows (reused from old commercial refrigerators) and a thick wood door.

Some of my specific questions are:

1. Should I decouple the cement foundation from the foundation of the rest of the house? How?

2. Do I need to decouple the wood ceiling, which connects straight into the wood skeleton of the rest of the house? How?

3. Does anyone have tips / experience with earth walls in a music studio? Sound isolation strategies that can be used in this context? Traditional materials that can be incorporated into an earth wall?

4. Would it be better (for sound isolation purposes) to build a thicker wall made of earthbags (~15 inches thick) or two thinner walls (~6 inches each) with a gap in between? Wouldn't the gap created in this second scenario be a resonance chamber that would require serious correction?


It's a home studio, and while I will use it professionally I don't need sound isolation to be 100 percent. But since I'm designing and building from scratch, I want to get it as right as possible the first time around. And the weight of those walls might change the building of the foundation, so I need to plan in advance.

Doubts, questions, comments, advice, all welcome. Thanks!

Ryan

[Soundman2020]

Hi. Please read the forum rules for posting (click here). You seem to be missing a couple of things!

Over the years, we have had many people come here to the forum with intentions of building studios with straw-bale or adobe or other traditional materials. As far as I know, none of them ever actually built their studios that way.

1. Best practices for sound isolation with preferably natural materials

The source of the materials is irrelevant. What matters is the laws of physics. The same laws of physics apply to "natural" materials, as apply to any other material.

(details on construction plans below)

I'm not quite sure what you mean by "music room", but after looking at your initial plans it's clar that this is a rather small room, at only 15m2, and given the shape, it clearly cannot be a used as a control room for mixing or mastering. Therefore I'm assuming that this room is meant only for practicing and rehearsal, not for recording. Is that correct? So I'm assuming that you need isolation for live acoustic instruments and vocals?

2. Any other specific advice for sound isolation between studio / rest-of-the-house

Isolation is always an "all or nothing" situation: Either your studio is isolated or it is not. If it is isolated from the rest of the house, then it is also isolated from the outside world. If it is NOT isolated from the rest of the house, then it is also not isolated from the rest of the world.

You don't say how much isolation you need in decibels, nor what types of instruments and genre you'll be practicing on, so it's impossible to give you any advice on how to isolate. You will first need to determine that number: how many decibels of isolation do you need? Once you can tell us that number, then it's easy to tell you what building materials and techniques you will need to use to attain the number you want. So your first priority should be to get a decent sound level meter and do some testing, to determine that number. There's a huge difference in building a studio to isolate for 50 dB, and building the same studio to isolate for 60 dB.

Ceiling is slightly vaulted.

Height? It is not marked on the plan, and sound is 3D, so height is just as important as X and Y dimensions.

So far the construction plans are cement foundation and burnt cement floor,

Good!

earth walls (probably wattle and daub) with a thicker-than-usual layer of straw in the center of the wall and extra plaster all around,

How thick? What is the density of the earth, and of the straw? What will the surface density of the wall be?

living roof (hardwood ceiling, on top of which is a water barrier, 10 cm of dirt, and plants),

How thick is the "hardwood", and what type of wood is it? What is the density of that wood? And of the earth? What is the total surface density of the ceiling?

double-paned windows (reused from old commercial refrigerators)

How thick is each pane of glass? What is the distance between them? What type of glass is it?

and a thick wood door.

Solid core or hollow core? If it is hollow-core, is it filled with insulation? If so, what type? How thick is the door? How heavy? Does it have any holes in it, such as a hole for mounting a typical domestic lock-set? What type of seals does it have around the perimeter, and how many of them are there?

1. Should I decouple the cement foundation from the foundation of the rest of the house?

Probably not necessary, but impossible to say without knowing how much isolation you need, nor the sound levels in the rest of the house. For example, if you have a loud pump or air conditioner compressor or washing machine bolted to the same floor slab, then yes, you should decouple. Ditto if you have a home theater with earth-shaking sub-woofers, or any other load sound source or vibration source. Also, in the other direction: if you will be playing live drums in there, and also have a bass cab on the floor, plus there's a baby sleeping in the room next door in the same slab, then yes, you should isolate. But without knowing the numbers and the rest of the details, it's impossible to say for sure. But overall, you probably do not need to isolate the slab.

How?

If you do need to isolate the slab, there are several methods, any of which might be applicable... or not! The simplest is simply to pour that slab and its foundations separately from the rest of the building, leaving a gap of maybe 1cm or so all around, then filling that gap with suitable highly resilient and flexible non-hardening expansion joint compound. At the other end of the scale, you could fully float a new slab on top of the basic slab.

2. Do I need to decouple the wood ceiling, which connects straight into the wood skeleton of the rest of the house?

Very probably, yes, but if that's the only surface you isolate, then don't waste your money. As I mentioned above, isolation is "all or nothing". That also means that if you don't isolate ALL sides of the room (including ceiling and floor), then you won't have any isolation at all! Think of this: Imagine there's a guy who wants to have an aquarium in his living room, because he likes to look at fish, so he goes to the store and buys a metal frame to make his aquarium. But then he thinks: "I only need to see them from the front, so I'll just buy one sheet of glass to put on that side, and leave the rest open". How well do you think that aquarium will hold water? Obviously, it won't hold water at all! But that is what you would be doing if you only isolate your ceiling...

In other words, if you do need to isolate your room from anything, then you need to isolate it form everything. You cannot isolate a room in only one direction, just like you cannot build an aquarium with glass on only one side. As soon as you put water in it, the water will simply gush out and splash all over, in ALL directions, even the direction where the glass is, since the water will go over, under, and around that glass. If you only isolate one side of your studio, then when you pour sound into it, the sound will gush out and splash all over, in all directions, including the direction where that one isolation wall was, because the sound will go under, over, and around that wall, as if it wasn't even there.

So, therefore, if you do need isolation, then you need the build the same amount of isolation in all directions around your room, and in all aspects: every wall, ceiling, floor, door, window, electrical conduit, HVAC duct, and everything else, must all be isolated to the same level. Acoustic isolation is onl as good as the weakest point, so if you isolate your studio fantastically all around except for the window, then you might as well not isolate anything, because sound will take the "easy" path out through that window...

It is "all or nothing". Many first time studio builders have a hard time understanding this concept, and think they can get away with only isolating some parts of their room, but that simply does not work. The laws of physics apply to everyone the same, even those people who don't understand them, or don't want to accept them!

How?

There's basically only two methods for isolating a typical home studio. You can try to do it with "Mass Law", which is the principle of physics that governs a single-leaf wall built from heavy, dense materials, or you can try to do it as a proper "room-in-a-room", which is more correctly called a "fully decoupled two-leaf MSM isolation system".

If you decide to go with a single leaf wall (door, window, ceiling, etc.), then it is governed by Mass Law. That's a simple equation that tells you how much isolation you will get, based only on the surface density of the wall: how much does each square meter of your wall ( / door / window / ceiling) weigh, in kg/m2? If you know that, then you can predict the isolation for ever single frequency on the musical spectrum, and you can draw a graph that shows exactly what your isolation will be. You can then compare that graph against the spectrum of each instrument that you will be rehearsing with in your room, to see if your proposed wall is going to stop the amount of sound that you need it to stop. If not, then you can increase the mass of your proposed wall, more and more, until eventually you get to the right mass that provides the right isolation for YOUR situation.

The problem with Mass Law is that it is not your friend! The basic physics of single-leaf sound barriers implies that each time you DOUBLE the mass of the wall, you will get an increase of 6 dB in isolation. That's in theory, which assumes your mass is perfect: in practice, with real-world materials, you can expect an increase of maybe 4 or 5 dB each time you double the mass. So let's say you do that math, and figure out that your 30cm thick adobe walls will provide about 40 dB of isolation, but you actually need 55 db of isolation (purely hypothetical: I don't know how much you actually need!). Using Mass Law, you would simply double the thickness of your wall from 30cm to 60cm (to get twice the mass), and that would increase the isolation from 40 dB to 45 dB. Then you would double the thickness again, from 60cm to 120 cm, and that would get you 50 dB of isolation. Then you would double the thickness (and mass) one more time, from 120 cm to 240 cm, to get you to 55 dB of isolation. Simple!

Except that I'm pretty sure you do not want walls that are 2m or 3m or 4m thick!

Clearly, Mass Law is not very friendly, if you need decent isolation. Which is why studios are never built like that! You cannot get decent isolation with a single-leaf wall, because Mass Law prevents it.

So you will probably need the other system: fully-decoupled two-leaf MSM isolation, ore commonly called "room-in-a-room". Basically, that just adds a second set of walls, floor, ceiling, doors, windows, built inside the shell that you already have from Mass Law. The two walls together are NOT subject to Mass Law: they are subject to an entirely different set of equations, because they create a resonant system. And with this system, you get an increase of 18 dB each time you double the mass, which is a much happier proposition! However, there's a drawback: it is a resonant system, so it is no longer just one equation that describes ow the wall isolates. There are several equations, and each one applies to just a part of the spectrum. For the part of the spectrum below the resonant frequency of the wall, Mass Law still applies. For the part of the spectrum around the resonant frequency of the wall and up to about 1.4 times the resonant frequency), resonance applies, and the wall isolates LESS than Mass Law. In fact, the wall can actually amplify sounds at that frequency, instead of attenuating them, so obviously it is important to tune the wall such that resonant frequency is way below the audible spectrum. Above that, you get your 18 dB per octave increase in isolation, which is great.... until you get to the frequency where the wavelength is smaller than the distance between the two leaves of the wall, when internal resonance once again robs yo uof isolation, and you only get an increase of around 12 dB per octave. Then there's also the point where sound waves hitting the wall at certain angles happen to coincide with certain conditions related to the building materials that you used to make the wall, and you get another drop in isolation: this is called the "coincidence dip". And above that, you get an increase of around 12 dB per octave again.

So a 2-leaf MSM wall needs to be designed such that all of this dips and curves and lines and regions match what you need, for your studio. But overall, it will be MUCH cheaper and MUCH more effective to build a wall this way, than to build a single-leaf wall, which is controlled by Mass Law.

3. Does anyone have tips / experience with earth walls in a music studio?

As I said, many on the forum have tried, none have succeeded. (as far as I know). Hopefully, you will be the first. As long as you can find all of the parameters that you need to know about your building materials so that you can apply the MSM equations to them, then it should work. Earth has decent density, so as long as you can figure out how to prevent it from cracking, and how to seal it perfectly, and as long as you know the density, surface density, and resonant characteristics of the final dried mud, then it's relatively easy to plug those numbers into the equations, and predict how your wall will work.

Sound isolation strategies that can be used in this context?

The only "strategy" that matters here is to choose if you want to go with Mass Law, or MSM law.

Traditional materials that can be incorporated into an earth wall?

It makes no difference at all if the materials are traditional, manufactured, or fell out of the sky from Planet Saturn! The ONLY thing that matters is the mass of the materials, and the resilience (related to stiffness, or rigidity), and the self-resonant characteristics of the material. As long as you know those, you can predict the isolation. Sound waves do not care how traditional or non-traditional the materials are, and they don't care about the price tag either. They can't read, and have no ideological nor ecological preferences: they just do not care. The only react to the physical properties of the material, most in regards to mass (density) and resilience (stiffness)

4. Would it be better (for sound isolation purposes) to build a thicker wall made of earthbags (~15 inches thick) or two thinner walls (~6 inches each) with a gap in between?

Once again, it does not matter what materials you use, as long as you know the physical properties of that material. You can build your wall from wood, or drywall, or diamond, or lead, or rock, or earth, or paper, or chicken feathers, or ice, or whatever you want! As long as you know what the properties are, and can put them into the equations, then you can use whatever you want.

And as I mentioned above, it will ALWAYS be better to build a 2-leaf wall than a single-leaf wall, because Mass Law is not much use. ... provided that you do the math, and calculate the outcome.

Wouldn't the gap created in this second scenario be a resonance chamber that would require serious correction?

Yes, the gap between the leaves certainly does create a resonant system, which is what makes a 2-leaf wall so very useful, acoustically! If it is resonant, then you can tune it any way you want it, and you can also damp it. That's the secrete here: a 2-leaf MSM wall works so well, because you can control the conditions and the isolation simply by selecting the correct mass for each leaf, the correct depth of the air cavity, and the correct insulation to fill it.

It's a home studio, and while I will use it professionally I don't need sound isolation to be 100 percent.

Good, because that's impossible! Any sufficiently loud sound will get trough any conceivable barrier. 100% isolation is a physical impossibility, because that implies an infinitely dense barrier that is infinitely rigid. That's why studio designers never talk about "percentage" and never talk about "soundproofing", because it cannot be achieved in this universe. The loudest sound ever heard by humans on planet earth, traveled around the world, and was clearly heard, loudly, thousands of kilometers away. It cracked concrete 400 km away. You cannot build a barrier to stop sounds like that. You can only build a barrier that will provide "X" amount of isolation, measured in decibels which is why you need to determine how many decibels of isolation you need, before you do anything else. Everything else will fall into place, fairly simply, once you determine what level of isolation need, in dB (and also after reading the forum rules again! )


- Stuart -

[ryanluckey]

Hi. Please read the forum rules for posting (click here). You seem to be missing a couple of things!

Sorry about that and thanks for responding anyway!

I'm not quite sure what you mean by "music room", but after looking at your initial plans it's clar that this is a rather small room, at only 15m2, and given the shape, it clearly cannot be a used as a control room for mixing or mastering. Therefore I'm assuming that this room is meant only for practicing and rehearsal, not for recording. Is that correct? So I'm assuming that you need isolation for live acoustic instruments and vocals?

Uh oh ... yes it's fairly small, but big enough for 2-4 musicians to play comfortably in, with gear, which is the most I'm expecting. But what concerns me is your comment:

it clearly cannot be a used as a control room for mixing or mastering.

... Is that because of L-R imbalances that will be created by the asymmetrical design? Or something else? We did that on purpose to avoid parallel walls and to have the greatest diversity of angles and wall sizes.

So your first priority should be to get a decent sound level meter and do some testing, to determine that number.

It's amazing how logical that is and yet I did not thank about that at all. I will try to track down a meter, but I'm in rural Brasil so it won't be easy or fast. I primarily need to be able to isolate at night, so I can keep work with really loud instruments (drums I'm looking at you) for during the day. My own compositions are primarily "electronic" (digital) so keyboard and synth based (easy to control volume levels), but I want to be able to record vocals, some percussion, bass, guitar, horns, etc. Like I said, noisier work can be kept to daytime, in which case isolation is not as important.

Height?

Good point. I've attached an additional image, but basically the ceiling height goes from about 3.42 m to 3.65 m.

How thick? What is the density of the earth, and of the straw? What will the surface density of the wall be?

The walls will be about 14-15 cm thick. I looked up the density of cob, which is basically straw mixed with mud, and got the figure of 1400-1700 kg/m3. That would be comparable to the "inside" of the wall, maybe 10 cm thick, with 2-3 cm of mud plaster covering that on both sides, which seals the wall and provides a smooth finished surface. The plaster is primarily clay, I found a link that says dry clay has a density of 1600 kg/m3. Does that help? I'm really not too clear how to calculate sound isolation based on the density figures.

How thick is the "hardwood", and what type of wood is it? What is the density of that wood? And of the earth? What is the total surface density of the ceiling?

The hardwood planks are tropical hardwoods, ranging from 4-6 cm thick, and I could definitely use the thicker ones over the studio. These planks are very heavy! They are multiple species in the range of 800-1000 kg/m3. Then comes 10 cm of dirt at around 1250 kg/m3. There is a layer of thick plastic in there, as well as some other materials, but I'd be more than happy calculating based on the wood and the dirt layer.

Solid core or hollow core? If it is hollow-core, is it filled with insulation? If so, what type? How thick is the door? How heavy? Does it have any holes in it, such as a hole for mounting a typical domestic lock-set? What type of seals does it have around the perimeter, and how many of them are there?

I haven't purchased or built the door yet, I have a lot of wood on hand, and skilled craftsmen in town. I'm guessing from the rest of whats you've said that A two-leaf door with an isolating material in the middle would be better than just a solid wood door. I would like it to be lockable from outside or inside, that might be an issue, are there easy solutions for that?

Very probably, yes, but if that's the only surface you isolate, then don't waste your money. As I mentioned above, isolation is "all or nothing".

While I get what you are saying, (I don't know exactly how much isolation I need but...) I do know that more isolation will make my life and my family's lives better. My question then is what is going to be my weakest point, I should take care of that first before doing anything else. Using your aquarium analogy, plugging the lowest holes in the aquarium will assure some water stays in there, even if some of the water leaks out from the holes at the top. Some water is better than none: could be the difference between life and death for the fish. In my case, could be the difference between being able to work comfortably at night or having to really lower volume after 8:00-9:00 pm.

I have a hunch the weakest points for sound isolation will be the door and the windows, followed by the structural wood connections and finally the walls themselves and floor. Does that sound about right?

Phew, lots of different threads inside this. I appreciate your taking the time out to engage me on this -

Ryan

[Soundman2020]

Sorry about that and thanks for responding anyway!

But what concerns me is your comment:

it clearly cannot be a used as a control room for mixing or mastering.

... Is that because of L-R imbalances that will be created by the asymmetrical design? Or something else? We did that on purpose to avoid parallel walls and to have the greatest diversity of angles and wall sizes.

It's unfortunate that you made the walls non-parallel, for several reasons. Firstly, yes, that's the reason why it would be no good for mixing: there's too much asymmetrical geometry there. And secondly, it's a myth that you need non-parallel walls on the first place! Let's deal with that second one first, since I'm sure that it has you scratching your head, and thinking I must be nuts or stupid... I mean, everyone "knows" that you MUST make your walls non-parallel in a studio, right? Everyone knows that! And they all keep on saying it! Except that it isn't true. The only thing that non-parallel walls will do for you acoustically, is to prevent flutter echo. That's it. And flutter echo can be treated very easily, in much less space and at much less cost than building strangely angled walls. But if you really did want to splay your walls in order to treat flutter echo, you would have to do it at an angle of at least 12°, because that's the minimum angle that is effective. In other words, the left wall of the room would have to be angled 12° more than the right wall, and also the front wall would have to be angled 12° more than the rear wall. If you do it less than 12°, then you won't be killing flutter echo either!

Some people will than say: "Yes, but... ROOM MODES! You have to angle your walls to get rid of the modes". That too is a myth. It is impossible to "get rid" of room modes, by any method. The only method that works, is called a "bulldozer"! Drive a bulldozer through the studio, make sure to knock down all the walls, and then your room will have no modes. Of course, there wont be a room at all! But that's the price you have to pay to get rid of modes. In simple terms, the modes will ALWAYS be there, and you CANNOT get rid of them by any method: all you can do is damp them with suitable treatment, but you can't make them go away. If you angle your walls, it does not get rid of the modes: you just move them to a different frequency, but they are still there. If you angle the wall at a very large angle, you might be able to mess things up enough that you force an axial mode to be converted into two or more tangential modes, but you didn't make the mode go away: you just changed it to a different type.

So, if angling your walls is no use for modes, and is overkill for flutter echo, then what other acoustic reason is left for doing it? Answer: none!

People who say that studio walls MUST be angled, are simply repeating a myth that has no basis in real acoustics. Yes, it can help a bit, but the small benefit you get is not worth the huge effort and expense. Angling the walls also makes the room smaller than it would have been, but its pretty much always better to make the room as large as possible, so angling the walls actually makes the room worse acoustically, not better.

There are only three valid reasons for angling walls in a studio: 1) For a control room, some design concepts rely on carefully crafted angles on some of the walls, as part of the concept. 2) If there's some type of structural feature in the existing building that can best be dealt with by angling a wall around it. 3) Because it looks cool! Some people just like the look of non-parallel walls... and it also helps to shut up the uninformed, ignorant critics, who would other wise be horrified that you DIDN'T angle your walls!

Yes, it's sad that you already built the place, and took some decisions based on a myth, but it's already built, so there's not much you can do about it. The angled walls probably won't do any harm to the acoustics (apart from making the room smaller than it could have been), so there's no real penalty for doing that. Especially considering that it is not a mixing room, and is only a rehearsal room.

I will try to track down a meter, but I'm in rural Brasil so it won't be easy or fast.

In the mean time, you could download an app onto your cell phone. It will not be accurate, of course, because a cell phone mic and audio circuitry is way deficient for acoustic analysis, but it can give you a rough idea, while you wait for your real meter to arrive. Just make sure that the app you use is able to be set for both "A" and "C" weighting, as well as both "fast" and "slow" response. Do these measurements with "C" and "Slow".

I primarily need to be able to isolate at night, so I can keep work with really loud instruments (drums I'm looking at you) for during the day.

Drums can easily put out 110 - 115 dBC, and even more if you have a heavy-handed drummer on a big kit. So assume your peak is going to be around115 dBC.

but basically the ceiling height goes from about 3.42 m to 3.65 m.

That's pretty good. Nice!

, and got the figure of 1400-1700 kg/m3. ... density of 1600 kg/m3. ...

Great! That sounds about right, and will certainly give you pretty decent isolation, as part of a two-leaf wall.

Does that help? I'm really not too clear how to calculate sound isolation based on the density figures.

There's a very simple equation in physics, which is often referred to as "Mass Law", since it describes how much isolation you will get from a barrier that consists of a single "leaf" of just mass. In other words, a solid wall, with nothing hollow inside. Here's the equation:

TL(dB)= 20log(M) + 20log(f) -47.2

Where:
M is the surface density of the panel (mass per unit area (kg/m²)
f is the frequency that you want to know the isolation for.

So with that it's easy to pick a bunch of frequencies, calculate the isolation for each one, and plot them on a graph. It will give you a pretty accurate prediction of how well a single-leaf barrier will isolate.

But that's for individual frequencies: there's a simplified version, called "Empirical Mass Law", that gives you a rough estimate of the overall isolation from the wall, in general, without considering frequencies. That equation looks like this:

TL = 14.5 log (M * 0.205) + 23 dB

Where: M = Surface density, in kg/m2

But for high mass walls, where the surface density is above about 150 kg/m2, there's another equation:

TL = 37.5 log (M) - 42 dB

So, if you take your material density figure, and use the wall thickness to figure that into actual surface, density, then you can plug that number into the above equations, and see how things look. For example, lets' look at your figure of 1400 kg/m3, and you mentioned that such a wall might be 15" thick. Let's say you want to know how much isolation your wall would get you for the bass guitar, because the guitarist has a huge amp and you are concerned about that... Let's say it's a 6-string bass, which goes down to about 35 Hz. So:

1400 kg/m3 *0.38m (to figure out the surface density of a 15" wall) = 532 kg/m2


TL(dB)= 20log(532) + 20log(35) -47.2
TL(dB)= 54.5 + 30.8 -47.2
TL(dB)= 38.1

Allowing for imperfections, you'd get about 35 dB of isolation for the lowest note on that bass. So if you assume that the bass player is pumping it out and 110 dBC, then it would be about 75 dBC outside the wall.

And your total isolation would be:

TL = 37.5 log (532) - 42 dB
TL = 60.2

So your wall would give you roughly 60 dB of isolation, overall. In other words, with the entire band in there bashing away at a song that covers most of the spectrum, and hitting 120 dBC, the level outside would be around 60 dBC.

That's actually pretty decent isolation.

However, all of the above only applies to single-leaf barriers. If you build another wall inside that outer shell, then Mass Law no longer applies, and you need to use a very different set of equations, that's a little more complex.

I'm guessing from the rest of whats you've said that A two-leaf door with an isolating material in the middle would be better than just a solid wood door.

Actually, it's the other way around! I guess I didn't explain that too well... You should never use a hollow-core door in a studio, since the empty space inside is basically just a resonant cavity, and at its resonant frequency it will AMPLIFY sounds, instead of stopping them. So you should only ever use solid doors. But you do need two of them, back to back, with a large space in between them. One single door will never be able to give you enough isolation by itself, because you just can't get enough mass on it and still have it easy to open and close! Imagine if you had a single door that has the same mass as your wall: 532 kg/m2. A typical door is about 1.8 m2, so that door would have to weigh about a ton. Literally, one ton! More exactly, it would be 957.6 kg! You might find it hard to buy hinges that can hold a door that weighs as much as a car!

Instead, you need two "lighter" doors, back-to-back, and in that case you'd use the MSM equations to figure out the isolation. They doors would still need to be heavy: maybe around 100 kg each, but that's a LOT better than a thousand!

I would like it to be lockable from outside or inside, that might be an issue, are there easy solutions for that?

Studio doors are usually too heavy to be closed safely by hand, so it is common practice to use an automatic door closer for that. The door closer is spring loaded, and has a sort of "shock absorber" mechanism inside, that slows the spring down, and will close the door gently, slowly, then apply extra pressure after it is closed, to keep the seals pressed properly. This means that you don't need a handle mechanism that goes all the way through the door to latch it closed, which is a good thing, because if you did need one of those, then you's have to drill a big hole in your door to mount it.... and drilling a hole would destroy your isolation!

That's a long explanation as to why you can't have any type of lock that needs a hole drilled through it. But you CAN have an elector-magnetic lock on our door, that does NOT need holes drilled all the way through...

My question then is what is going to be my weakest point, I should take care of that first before doing anything else.

The weakest points in most studios are usually: Bad sealing of the wall, floor and ceiling surfaces; cracks and gaps around walls/floor/ceiling; doors; windows; the electrical system; and the ventilation system. Roughly in that order.

Using your aquarium analogy, plugging the lowest holes in the aquarium will assure some water stays in there, even if some of the water leaks out from the holes at the top.

Ahh, but there's the thing! If "some" water leaks out, then you still get wet! Your carpet will get soaked just as much from a small leak, as it will from a major leak. And sound is a bit different from water: if you have a small crack under your wall, for example, then that will let some sound out. But once it is out, the sound waves expand out in all directions from that gap, and go everywhere...

Some water is better than none:

But you are looking at it from the wrong perspective! You are not trying to keep some water inside the tank: that's not the goal. You trying to stop any of it from getting out!

could be the difference between life and death for the fish.

Yes, but musicians won't die if some sound leave the room! On the other hand, the neighbors might not be too happy, and come knocking on your door, with a flaming torch in one hand, and a pitchfork in the other...

The fish tank analogy is not about the fish, or about keeping a bit of water inside the tank: it's about NOT letting water get out and ruin your living room!

Phew, lots of different threads inside this.

Welcome to the wonderful, convoluted, non-intuitive world of acoustics!

(And you are only just getting started, with the simple stuff:: it gets more complicated, later... )


- Stuart -

[ryanluckey]

Hey Stuart,

Thanks again for the responses! The calculations for sound isolation are very helpful, I will download an app and play around with decibel levels... the door tips too, I can do two solid wood doors no problem. Good wood is plentiful here.

Here's the main thing: I am actually interested in doing some mixing in this studio, which is the bad news given your assessment. The good news is, this studio is not built yet!! I guess maybe I misspoke in my first post? Construction begins soon, but there's still time so we could re-design it right now!

If I were to redesign, there are two walls I'd really like to keep in place, the wall with the door in it, and the wall just below that, the smaller one on the bottom left corner of the image. Moving either of those would significantly change other areas of the house. The three walls on the right side have no physical limits and can be moved as needed, and the wall on the bottom would be *easier* to maintain as is but could be adjusted if necessary. Given those restraints, do you have any specific recommendations in the format of the room?

So far I have been thinking not to separate a true 'control room' but perhaps build a small recording booth for individual vocals or instruments if needed. I'm hesitant to split this space into 2 parts since as you pointed out it's not too big to begin with. However I could consider splitting in 2 if it were beneficial for the geometry (acoustics) - and I have no idea what sort of proportions I would want in that case.

Basically I see 3 options:

1. Build the current design, test, and live with the limitations. Probably end up doing final mixes for elaborate projects elsewhere.

2. Change the format of the studio now to be better for mixing, maintain 1 main space and maybe build an isolated recording booth inside.

3. Change the format of the studio now to be better for mixing, and divide into a live room and a control room.

Looking forward to hearing your suggestions... Thanks in advance - Ryan

[ryanluckey]

I guess in addition to those specific and practical questions above is the more fundamental question: Can a 1 room studio fulfill the triple purpose of being a good recording space, a good mixing space, and a nice place to listen to and enjoy music? That is what I want, but I'm starting to doubt if that is a realistic expectation... that's why I am all of a sudden considering splitting the studio into two spaces, something I had ruled out from the beginning...

[Soundman2020]

Here's the main thing: I am actually interested in doing some mixing in this studio, which is the bad news given your assessment. The good news is, this studio is not built yet!!

That sure is good news! It means you have time to design it right, so it can be used for mixing as well.

Construction begins soon,

Hmmmmm.... Probably not a good idea! If you look around the forum, you'll find a few threads where people started building before they had a complete and detailed design in place.... and it didn't work out too well for them! We ALWAYS suggest holding off on construction until you have finished the entire design, in full detail, all aspects, complete. And that takes time. First you need time to learn how to do it (I'd suggest two books: "Master Handbook of Acoustics" by F. Alton Everest (that's sort of the Bible for acoustics), and "Home Recording Studio: Build it Like the Pros", by Rod Gervais), then you need to learn the software for doing the design (we suggest SketchUp right now, although that recommendation might change soon due to the ugly new policies of the manufacturer...), then you need time to actually do the design work yourself, and check it. Realistically, all of that can take you six months to a year, until you are properly ready to build. And like I said, building before you have a complete design ready, is always a mistake. If you can't wait that long, or don't want to go to all the trouble of learning all of that stuff, then you could hire a studio designer to do it for you. If you want to go taht path, I'd suggest that you PM John Sayers himself, and ask him to quote.

but there's still time so we could re-design it right now!

So far I have been thinking not to separate a true 'control room' but perhaps build a small recording booth for individual vocals or instruments if needed

What instruments do you need to record in there? In general recording an acoustic instrument in a small booth will give you a small, "boxy" sound to the recording. Small rooms don't give good acoustics for tracking most instruments. You do have the advantage of the high ceiling, which is very nice, but you also do need decent floor area.

I'm hesitant to split this space into 2 parts since as you pointed out it's not too big to begin with.

Right.

However I could consider splitting in 2 if it were beneficial for the geometry (acoustics) - and I have no idea what sort of proportions I would want in that case.

Two things to consider here: 1) "Bigger is better". In general, a bigger room will almost always have better acoustics than a smaller room, and this is closely related to the second thing: 2) Room modes, and room ratios... :

Room ratios is a whole major subject in studio design. It works like this: The walls of your studio create natural resonances in the air space between them, inside the room. This is totally different from the MSM resonance of the walls themselves: this is all about what happens INSIDE the ROOM, not what happens inside the walls. Two totally different things.

So you have resonant waves inside the room. We call those "standing waves" or "room modes". Those "modes" (resonances) occur at very specific frequencies that are directly related to the distances between the walls. They are called "standing waves" because they appear to be stationary inside the room: they are not REALLY stationary, since the energy is still moving through the room. But the pressure peaks and nulls always fall at the exact same points in the room each time the wave energy passes, so the "wave" seems to be fixed, static, and unmoving inside the room. If you play a pure tone that happens to be at the exact frequency of one of the "modes", then you can physically walk around inside the room and experience the "standing" nature of the wave: you will hear that tone grossly exaggerated at some points in the room, greatly amplified, while at other points it will sound normal, and at yet other points it will practically disappear: you won't be able to hear it at all, or you hear it but greatly attenuated, very soft.

The peaks and nulls fall at different places in the room for different frequencies. So the spot in the room where one mode was deafening might turn out to be the null for a different node.

Conversely, if you have a mode (standing wave) that forms at a specific frequency, then changing to a slightly different frequency might show no mode at all: for example, if a tone of exactly 73 Hz creates a standing wave that is clearly identifiable as you walk around the room, with major nulls and peaks, then a tone of 76 Hz might show no modes at all: it sounds the same at all points in the room. Because there are no natural resonances, no "room modes" associated with that frequency.

That's the problem. A BIG problem.

Of course, you don't want that to happen in a control room, because it implies that you would hear different things at different places in the room, for any give song! At some places in the room, some bass notes would be overwhelming, while at other places the same notes would be muted. As you can imagine, if you happen to have your mix position (your ears) located at such a point in the room, you'd never be able to mix anything well, as you would not be hearing what the music REALLY sounds like: you would be hearing the way the room "colors" that sound instead. As you subconsciously compensate for the room modes while you are mixing, you could end up with a song that sounds great in that room at the mix position:the best ever! But it would sound terrible when you payed it at any other location, such as in your car, on your iPhone, in your house, on the radio, at a club, in a church, etc. Your mix would not "translate".

And you also don't want major modal issues in a tracking room, for similar reasons: As an instrument plays up and down the scale, some notes will sound louder than others, and will "ring" longer. The instrument won't sound even and balanced.

OK, so now I have painted the scary-ugly "modes are terrible monsters that eat your mixes" picture. Now lets look at that a bit more in depth, to get the real picture.

So let's go back to thinking about those room modes (also called "eigenmodes" sometimes): remember I said that they occur are very specific frequencies, and they are very narrow? This implies that if you played an E on your bass guitar, it might trigger a massive modal resonance, but then you play either a D or an F and there is no mode, so they sound normal. Clearly, that's a bad situation. But what if there was a room mode at every single frequency? What if there was one mode for E, a different mode for D and yet another one for F? In that case, there would be no problem, since all notes would still sound the same! Each note would trigger its own mode, and things would be happy again. If there were modes for every single frequency on the spectrum, and they all sounded the same, then you could mix in there with no problems!

And that's exactly what happens at higher frequencies. Just not at low frequencies. Because of "wavelength"

It works like this: remember I said that modes are related to the distance between walls? It's a very simple relationship. Remember I said the waves are "standing" because the peaks and nulls occur at the same spot in the room? In simple terms, for every frequency where a wave fits in exactly between two walls, then there will be a standing wave. And also for exactly twice that frequency, since two wavelengths of that note will now fit. And the same for three times that frequency, since three full waves will now fit in between the same walls. Etc. All the way up the scale.

So if you have a room mode at 98 Hz in your room, then you will also have modes at 196 Hz (double), 294 (triple), 392 (x4), 490(x5), 588(x6), 686(x7) etc., all the way up. If the very next mode in your room happened to be at 131 Hz, then there would also be modes at 262 Hz(x2), 393(x3), 524(x4), 655(x5), etc.

That's terrible, right? There must be thousands of modes at higher frequencies!!! That must be awful!

Actually, no. That's a GOOD thing. You WANT lots of modes, for the reasons I gave above: If you have many modes for each note on the scale, then the room sounds the same for ALL notes, which is what you want. It's good, not bad.

But now let's use a bit of math and common sense here, to see what the real problem is.

If your room has a mode at 98Hz, and the next mode is at 131 Hz, that's a difference of 32%! 98 Hz is a "G2". So you have a mode for "G2". but your very next mode is a "C3" at 131Hz. That's five notes higher on the scale: your modes completely skip over G2#, A2, A2#, and B2. No modes for them! So those four notes in the middle sound perfectly normal in your room, but the G2 and C3 are loud and long.

However, move up a couple of octaves: ...

There's a harmonic of your 98Hz mode at 588 Hz, and there's a harmonic of your 131 Hz mode at 524 Hz. 524 Hz is C5 on the musical scale, and 588 Hz is a D5. They are only two notes apart!

Go up a bit more, and we have one mode at 655 and another at 686. 655 is an E5, and 686 is an F5. they are adjacent notes. Nothing in between! We have what we want: a mode for every note.

The further up you go, the closer the spacing is. In fact, as you move up the scale even higher, you find several modes for each note. Wonderful!

So at high frequencies, there is no problem: plenty of modes to go around and keep the music sounding good.

The problem is at low frequencies, where the modes are few and far between.

The reason there are few modes at low frequencies is very simple: wavelengths are very long compared to the size of the room. At 20 Hz (the lower limit of the audible spectrum, and also E0 on the organ keyboard), the wavelength is over 56 feet (17m)! So your room would have to be 56 feet long (17 metersn long) in order to have a mode for 20 Hz.

Actually, I've been simplifying a bit: it turns out that what matters is not the full wave, but the half wave: the full wave has to exactly fit into the "there and back" distance between the walls, so the distance between the walls needs to be half of that: the half-wavelength. So to get a mode for 20 Hz, your room needs to be 56 / 2 = 28 feet long (8.5M) . Obviously, most home studios do not have modes at 20 Hz, because there's no way you can fit a 28 foot (eight meter) control room into most houses!

So clearly, the longest available distance defines your lowest mode. If we take a hypothetical dimensions as an example (typical of home studio sizes), and say the length of the control room is 13 feet (4m), the width is 10 feet (3m), and the height is 8 feet. (2.5M) So the lowest mode you could possibly have in your room, would be at about 43 Hz (fits into 13 feet or 4M perfectly). That's an "F1" on your bass guitar.

The next highest mode that you room could support is the one related to the next dimension of the room: In this case, that would be width, at 10 feet / 3M. That works out to 56.5 Hz. That's an "A1#" on your bass guitar. Five entire notes up the scale.

And your third major mode would be the one related to the height of the room, which is 8 feet /2.5M, and that works out to 71 Hz, or C2# on the bass guitar. Another four entire notes up the scale.

There are NO other fundamental modes in that room. So as you play every note going up the scale on your bass guitar (or keyboard), you get huge massive ringing at F, A# and C#, while all the other notes sound normal. As you play up the scale, it goes "tink.tink.tink.BOOOOM.tink.tink.tink.tink.BOOOOOM.tink.tink.tink.BOOOOOM.tink.tink...."

Not a happy picture.

There are harmonic modes of all those notes higher up the scale, sure. But in the low end, your modes are very few, and very far between.

So, what some people say is "If modes are bad, then we have to get rid of them". Wrong! What you need is MORE modes, not less. Ideally, you need a couple of modes at every single possible note on the scale, such that all notes sound the same in your room. In other words, the reverberant field would be smooth and even. Modes would be very close together, and evenly spread.

So trying to "get rid of modes" is a bad idea. And even if it were a good idea, it would still be impossible! Because modes are related to walls, asI already mentioned, the only way to get rid of modes is with a bulldozer! Knock down the walls...

That's a drastic solution, but obviously the only way to get a control room that has no modes at all, is to have no walls! Go mix in the middle of a big empty field, sitting on top of a 56 foot (17 M) ladder, and you'll have no modes to worry about....



Since that isn't feasible, we have to learn to live with modes.

Or rather, we have to learn to live with the LACK of modes in the low end. As I said, the problem is not that we have too many modes, but rather that we don't have enough of them in the low frequencies.

Obviously, for any give room there is a point on the spectrum where there are "enough" modes. Above that point, there are several modes per note, but below it there are not.

There's a mathematical method for determining where that point is: a scientist called Schroeder figured it out, years ago, so it is now known as the Schroeder frequency for the room. Above the Schroeder frequency for a room, modes are not a problem, because there are are lots of them spaced very close together. Below the Schroeder frequency, there's a problem: the modes are spaced far apart, and unevenly.

So what can we do about that?

All we can do is to choose a "room ratio" that has the modes spaced out sort of evenly, and NOT choose a ratio where the modes are bunched up together. For example, if your room is 10 feet long and 10 feet wide and 10 feet high (3m x 3m x 3m), then all of the modes will occur at the exact same frequency: 56.5 Hz. So the resonance when you play an A1 on the bass, or cello, or hit an A1 on the keyboard, will by tripled! It will be three times louder. The nulls will be three times deeper. That's a bad situation, so don't ever choose room dimensions that are the same as each other.

You get the same problem for dimensions that are multiples of each other: a room 10 feet high (3m) by 20 feet wide (6m) by 30 feet long (9m) is also terrible. All of the second harmonics of 10 feet will line up with the 20 foot modes, and all of the third harmonics will line up with the 30 foot modes, so you get the same "multiplied" effect. Bad.

In other words, you want a room where the dimensions are mathematically different from each other, with no simple relationship to each other.

That brings up the obvious question: What ratio is best?

Answer: there isn't one!

Over the years, many scientists have tested many ratios, both mathematically and also in the real world, and come up with some that are really good. The ratios they found are named after them: Sepmeyer, Louden, Boner, Volkmann, etc. Then along came a guy called Bolt, who drew a graph showing all possible ratios, and he highlighted the good ones found by all the other guys, and predicted by mathematical equations, plus a few of his own: If you plot your own room ratio on that graph, and it falls inside the "Bolt area", then likely it is a good one, and if it falls outside the "Bolt area", then likely it is a bad one. Sort of.

So, there are no perfect ratios, only good ratios and bad ratios.

It is impossible to have a "perfect" ratio, simply because that would require enough modes to have one mode for every note on the musical scale, but that's the entire problem with small rooms! There just are not enough modes in the low end. So you can choose a ratio that spreads them a bit more this way or a bit more that way, but all you are doing is re-arranging deck chairs on the Titanic, in pleasant-looking patterns. The problem is not the location of the deck chairs; the problem is that your boat is sunk!: Likewise for your studio: the problem is not the locations of the modes: the problem is that your room is sunk. No matter what you do with the dimensions, you cannot put a mode at every note, unless you make the room bigger. It is physically impossible.

But that does not mean that your room will be bad. That's the common perception, and it is dead wrong.

All of this leads to the question you didn't ask yet, but were probably heading for: What can I do about it?

Here's the thing: Modes are only a problem if they "ring". The wave is only a problem if the energy builds up and up and up, with each passing cycle, until it is screaming, and then the "built up" energy carries on singing away, even after the original note stops. That's the problem. If you stop playing the A1 on your guitar, and the room keeps on playing an A1 for a couple of seconds,because it "stored" the resonant energy and is now releasing it, then that's a BIG problem! The room is playing tunes that never were in the original music!

If a mode doesn't ring like that, then it is no longer a major issue.

So how do you stop a mode? You can't stop it from being there. But you CAN stop it from "ringing". You can "damp" the resonance sufficiently that the mode dies away fast, and does not ring. You remove the resonant energy and convert it into heat: no more problem! In other words, it's not good if you own a large angry dog that barks all the time and bights your visitors, but it's fine to own a large angry dog with a muzzle on his mouth, so he cannot bark and cannot bight!

You do that with "bass trapping". A bass trap is like the dog muzzle. It doesn't get rid of the problem, but it does kep it under control. You use strategically placed acoustic treatment devices inside the room that absorbs the ringing of the mode, then that it cannot ring. There are several ways to do that, with different strategies, but the good news is that in most rooms it is possible to get significant damping on the modes, so that they don't ring badly, and don't cause problems. Note that the bass trapping does not absorb the mode: it just absorbs the ringing. Some people don't understand this, and think that the bass trapping makes the modes go away: it doesn't. All it does is to damp them. The modes are still there, and still affect the room acoustics in other ways, but with good damping, at least they don't "ring" any more.

And that is the secret to making a control room good in the low end! Choose a good ratio to keep the modes spread around evenly, then damp the hell out of the low end, so modes cannot ring. It's that simple.

The smaller the room, the more treatment you need. And since those waves are huge (many feet long), you need huge bass trapping (many feet long/wide/high/deep). It takes up lots of space, and the best place for it is in the corners of the room, because that's where all modes terminate. If you want to find a mode in your room, go look for it in the corner: it will be there. All modes have a pressure node in two or more corners, so by treating the corners, you are guaranteed of hitting all the modes.

As I said, there is no single "best" ratio, but there are good ones. You can use a "Room Mode Calculator" to help you figure out which "good ones" are within reach of the possible area you have available, then choose the closest good one, and go with that. And stay away from the bad ones.

Arguably, Sepmeyer's first ratio is the "best", since it can have the smoothest distribution of modes... but only if the room is already within a certain size range. Other ratios might be more suitable if your room has a different set of possible dimensions. So there is no "best".

But that's not the entire story: So far, all the modes I have mentioned are only related to two walls across the room, opposite from each other. I mentioned modes that form along the length axis of the room (between the front and back wall), others that form along the width axis (between left and right walls), and others that form on the height axis (between floor and ceiling): Those are the easiest ones to understand, because they "make sense" in your head when you think about them. Those are called "axial modes", because they form along the major axes of the room: length axis, width axis, height axis.

However, there are also other modes that can form between four surfaces, instead of just two. For example, there are modes that can bounce around between all four walls, or between the front and back walls as well as the ceiling and floor: those are called "tangential modes". And there are other modes that can form between all six surfaces at once: they involve all four walls plus the ceiling and the floor. Those are called "oblique modes".

The complete set of modes in your room consists of the axial modes, plus the tangential modes, plus the oblique modes.

That's what a good room mode calculator (a.k.a. "room ratio calculator") will show you. There are bad calculators that only show you the axial modes, which is pretty pointless, and the good ones show you all three types.

Use one of these Room Ratio calculators to figure out the best dimensions for your room:

http://www.bobgolds.com/Mode/RoomModes.htm

http://amroc.andymel.eu/

Both of those are very good, and will help you to decide how best to build your room. They give you tons of information that is really useful to help figure out the best dimensions.

However, modes aren't that important, despite all the hype they get: Modes are one aspect of room design, but there are many more. It's wise to choose a ratio that is close to one of the good ones, or inside the Bolt area, but you do NOT need to go nuts about it! There's no need to nudge things around by millimeters or smalls fractions of an inch, hoping to get a "better" ratio. Just stay away from the bad ones, get close to a good one, and you are done. End of story.

1. Build the current design, test, and live with the limitations. Probably end up doing final mixes for elaborate projects elsewhere.

Probably not a good option at all!

2. Change the format of the studio now to be better for mixing, maintain 1 main space and maybe build an isolated recording booth inside.

3. Change the format of the studio now to be better for mixing, and divide into a live room and a control room.

You missed one option: Change the current design to make it as big as possible, designed to do both!

Can a 1 room studio fulfill the triple purpose of being a good recording space, a good mixing space, and a nice place to listen to and enjoy music? That is what I want, but I'm starting to doubt if that is a realistic expectation... that's why I am all of a sudden considering splitting the studio into two spaces, something I had ruled out from the beginning...

Here's the thing: For mixing, the room must have a very specific, well defined, acoustic response. Basically, it must be "neutral": it must have no sound of its own, it must not add anything to the sound coming from the speakers, and it must not take anything away from that sound. It must only allow the speakers to tell you the perfect truth, without "coloring" that sound in any way. So it must have flat frequency response, and "flat" response in the time domain as well, in the sense that all frequencies decay at the same rate, which is the "correct" rate for that sized room. It must also not have any sharp spectral reflections at the mix position, and must produce a diffuse reverberant field. TO get the full set of specs, take a look at the ITU document, BS.1116-3. Here's an example of a room that meets that spec perfectly, and is actually BETTER than the spec in some aspects: http://www.johnlsayers.com/phpBB2/viewt ... =2&t=20471 .

However, a tracking room, or rehearsal must NOT be neutral! Rather, it must have "character" and "vibe". It must be pleasant to play in, and enhance the sounds of the instruments. That's a very different situation from what a control room needs. The opposite, in fact.

So, it's basically impossible to have a single room that is fantastic for mixing and also fantastic for tracking. Some people then think: "OK, I'll design it to be a bit of both, sort of part way between"flat response and a nice vibrant sound". Bad idea! All that you get is a room that is bad for BOTH! It's no good for precision mixing because it isn't flat, and it's no use for tracking/rehearsing because it has no real character, just sort of half-hearted, mushy muddy sound.

However, there is a solution: You can make your room variable. You can design it with acoustic devices that can be changed in some way to modify the room acoustics to be good for both. So you would have several panels on the walls that can be flipped, slid, rotated, opened, closed, turned around, or whatever, with one side providing the treatment for making the room neutral, and the other side having the treatment to make it "warm".

It is possible. The design is more complicated, of course, and so is the construction. Lots more calculations to do, in order to get the acoustics right for both situations. It's not easy to accomplish, but it cab be done. I have designed a few rooms with variable acoustic devices, and they do work.

So that might be your best option, and that's the way I would do it, if that were my room. I would design it to be as large as possible, moving all the walls as far back as they can be moved, then arranging them for good symmetry, then checking the modal response and perhaps adjusting for that, then laying it out mostly as a control room, and adding a bunch of variable acoustic elements on the walls and ceiling to be able to modify the room sound from "flat" to "warm".

- Stuart -

[ryanluckey]

Hi Stuart,

Thanks for the very thorough response! I imagine everything you just summarized in there is really useful to a lot of people like me who are just starting out. I "get" room modes much more now... In my case, since the room is an irregular polygon, I think there's no way to calculate the room modes with a system where the inputs are width, length, and height. In that case I would have to build and then test, measure responses and then design the treatment, right?

Your feedback pushed me to go back and review more clearly the purpose of this studio, needs and expectations. When you say:

So, it's basically impossible to have a single room that is fantastic for mixing and also fantastic for tracking. Some people then think: "OK, I'll design it to be a bit of both, sort of part way between"flat response and a nice vibrant sound". Bad idea! All that you get is a room that is bad for BOTH! It's no good for precision mixing because it isn't flat, and it's no use for tracking/rehearsing because it has no real character, just sort of half-hearted, mushy muddy sound.

That makes perfect sense. And the option of having a specialized design and build that allow for switching back and forth makes sense, if that is the only option, but it sounds really complex. What I'm thinking now is that I can build a control room in the future, as an annex to this studio, separating the two functions for a more ideal environment for each. That means I can focus on this space serving primarily for composition, rehearsal, recording and production, treat the room to get the best sound I can for those purposes (a nice, vibrant sound as you call it), and then either mix and master somewhere else or build the control room in a year or two.

The modification I am planning in that case is to expand the outer limits of the studio, which I can do pretty easily, which seems to be totally worth it as the long-term benefits mean less treatment for a better sound, more space for more gear + people, and more flexibility on studio arrangement. I'm basically considering just pulling out the three walls on the right side of the design, adding another 5m2 or so, which would mean a total of 20m2.

Those are my current plans. I have a meeting with my architect tomorrow so we can discuss this and probably start the modification process.

Your feedback has been extremely helpful and clarifying, thanks a lot for putting the time in to these responses!

-Ryan