John Sayers' Recording Studio Design Forum Archive

The Lord has blessed me with a ~95 m^2 garage and now I am (with help of a contractor) constructing a studio in it. The previous owner of this property had built it half way ready. Apparently his purpose was to start fixing cars or whatever. Our primary goal now is to have it first finished to a point where it passes the final inspection and then the game is on. Ok, the game is on already. The codename alludes to John Calvin, in commemorating the upcoming 500th anniversary of the protestant reformation.

Here is the basic plan: Here are some pictures from along the way and where we are now: Questions:

1. Out of necessity, the studio floor will be a floating one, because I have chosen electric heating cable as the heat source. This will raise the floor surface for about 150mm. I believe the wall between the studio and control room would be best built straight upon the concrete slab. Am I correct? The heated floors have 100mm insulation to the slab and 50mm to any wall. Will it work or will it have ramifications soundproof-wise? Will it make any/notable difference to, say, isolate the studwork from the slab with some sort of a rubber padding?
2. Of course I want a window between the studio and the control room. I have no idea either where to find a soundproof window or what needs to be taken into account. Also, I am not exactly sure what has a greater effect on what: I mean does the window affect the wall or the wall the window. If with a window it is possible to achieve such and such level if sound isolation, why would I build a wall that exceeds the capacity of the window or vice versa? Am I making sense?

Thanks in advance for any help.

Hi there Simon, and Welcome!

"Code-name Calvin" Gotta love that! Great man, but I won't bother getting into the doctrines he came up with (notably, "TULIP"....)

Anyway, about studios, not theology:

I did the drawing with Illustrator...

I would suggest that you switch to SketchUp: It's a full modeling program, and is free for private use. Very powerful.

Here is the basic plan:

You are only showing one "leaf" of the wall! Studio walls are built as two-leaf systems, not single-leaf, because you cannot easily get good isolation from a single leaf at low cost. So you need to fix your plan to make your studio into a fully-decoupled two-leaf isolation system. So each doorway will have two doors in it, "back-to-back": one in the inner-leaf of the room, and one in the outer leaf.

we have insulated it with 50mm Finnfoam

What type of foam is that? Is it open-cell or closed-cell? You should never use closed cell insulation in studios: it is great thermally, but not much use acoustically.

Here we have finished the insulation of the outer wall. All electric tubes and housings for lights, switches etc. are in place.

Whoooaaaa!!! Hang on there! Why do you have light switches and electrical outlets in your outer leaf??? They will all be covered up when you build your inner-leaf next to that...

All of your electrical installation goes inside your inner-leaf, never on your outer leaf. Also, you should use surface-mounted electrical system: you can't use normal electrical boxes, because that implies cutting large holes in your isolation leaf... If you cut a hole in your isolation, then you have no isolation....

It seems to me that you guys are racing ahead way to fast, with no design and no provision for isolation, or acoustics. You should probably slow down until you have the complete design fully finished, with all aspects taken care of.

Vapor seal in place.

It does not go down to the floor: Why? It seems to stop about 20cm or so up from the floor, so it is not a vapor barrier.

Also, I see that on the wall, but not on the ceiling. There's a section in the far corner where the joists are visible, and clearly there's no vapor barrier up there.

Vapor barriers need to be full seals, around the entire room, creating a "shell" or "envelope" around the room.

1. Out of necessity, the studio floor will be a floating one,

You should probably read this: http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

But what you show in your diagram does not look like a true floating floor.

I believe the wall between the studio and control room would be best built straight upon the concrete slab. Am I correct?

Yes, but not just that wall: All of your inner-leaf walls should be built directly on the original slab. Then you can add the heating and "floating" floor within each individual room.

Will it make any/notable difference to, say, isolate the studwork from the slab with some sort of a rubber padding?

Not really, and there's no need to do that. Floating a wall is just as complex as floating a floor, and just as unnecessary.

I have no idea either where to find a soundproof window or what needs to be taken into account.

Once again, it's not just one window you need, but two: one window goes in each leaf. So you have one frame containing a single pane of thick laminated glass in the first leaf, and another separate frame containing a single pane of thick laminated glass in the other leaf.

Also, I am not exactly sure what has a greater effect on what: I mean does the window affect the wall or the wall the window.

The both work together, and they both need to be designed together.

A studio wall is a tuned system. There are two "leaves" of mass, and they are separated by an air gap, which is filled with porous open-cell insulation. The two leaves do not touch: there is no mechanical connection between them. Each leaf is usually built as a stud frame with drywall (and/or OSB, MDF, plywood/etc.) on only ONE side of that frame (never both sides). The entire system resonates at a specific frequency, often referred to as the MSM resonant frequency. "MSM" stands for "Mass-Spring-Mass", which is the most basic principle in physics of how resonant systems work: a massive support with a spring hanging from it, and another mass hanging on that spring. If you pull the bottom mass and let go, it will bounce up and down at a fixed rate that is governed only by the stiffness of the spring, and the amount of mass. A studio wall is the same in principle. You have a "mass" on one side (the first leaf), a "mass" on the side (the second leaf), and a "spring" in the middle (the air trapped in the cavity). Just like the mass bouncing on a spring, your wall resonates at one specific frequency when the two leaves oscillate due to the "springy" air between them. You have to "tune" the wall such that the resonant frequency is at least an octave lower than the lowest frequency that you need to isolate.

You tune the wall by choosing the correct mass (surface density) for each leaf, and the correct spring (depth of the air gap).

So, to answer your original question: the entire wall must have the same surface density at all points. If the surface density for the leaf needs to be (for example) 25 kg/m2, then you need to make sure that you have at least that much mass on every square meter of the wall, regardless of the building material. So where you have drywall, you need enough layers of drywall to get 25 kg/m2, and where you have glass, the glass needs to be thick enough that it too has a density of 25 kg/m2 (or more). And where you have doors, they also need to have a surface density of 25 kg/m3.

I'm not saying that your walls will need 25 kg(m2 in each leaf!!! I just chose that as an example. You will have to calculate what density you need for your walls, based on your own isolation level and isolation spectrum.

If with a window it is possible to achieve such and such level if sound isolation

Yes, definitely! Most studios have windows. As long as the window system is design correctly, it will provide just as much isolation as the rest of the wall.

Why would I build a wall that exceeds the capacity of the window or vice versa?

Answer: You wouldn't! You would design both of them to get the same isolation.

Actually, the window needs a little more mass and a little larger air gap, for one simple reason: there is insulation inside the wall cavity, but obviously you can't put insulation between the two panes of glass in your window! You need to see through the window, so you have to leave the air cavity empty there, and that reduces the isolation for that part of the wall. You can compensate for that with thicker (more massive) glass, and a larger air gap. But all of that needs to be calculated: don't guess!

- Stuart -

Stuart, thank you so much for taking the time.

Soundman2020 wrote:I would suggest that you switch to SketchUp: It's a full modeling program, and is free for private use. Very powerful.

Yeah... let's just say that the T in TULIP started to emerge in me, when I tried it...

You are only showing one "leaf" of the wall! Studio walls are built as two-leaf systems, not single-leaf, because you cannot easily get good isolation from a single leaf at low cost. So you need to fix your plan to make your studio into a fully-decoupled two-leaf isolation system. So each doorway will have two doors in it, "back-to-back": one in the inner-leaf of the room, and one in the outer leaf.

Well, seems I need to make some clarification. Yes, this is supposed to be a recording studio, but more than that, a multi-purpose "man cave". If I still had a band, it would be a rehearsal space too. I work at home as an programmer enterpreneur. So basically the purpose of the studio is:

• That I can play the drums without annoying my wife
• That I can record and mix music without annoying my wife
• That I can watch football without annoying my wife
• That I can work in peace without being annoyed by my wife

What I value most is space, which means I am very hesitant to give up any of it. I don't have much room as it is, since half of the building will be used as a garage. I don't want it to become too crammed. This all means that I have purposefully abandoned the fancy weird-shaped room designs typical to many studio designs you see on this forum. I also have to let go of the ideal room-inside-a-room design. That eats up some valuable space too and I have too many people to convince about it and it's all just a bit too much.

What that means, is that I will have one wall with two leaves and that is the wall between the studio and the control room. I have not drawn it in my plan as such, but that's what it's supposed to be anyway. I am prepared to put effort in it to get a maximum efficiency wall. I do know that the outer wall has only one leaf. As to how much it isolates to the outside, that is not a concern. My yard. Eat me, neighbors! Jk. I do know that sound will travel from the studio to the control room at least through:

• The outer wall The outer wall will have two layers of gypsum per fire safety regulations
• The concrete slab Finnfoam is a dense styrofoam, so it, as you said, probably is a poor sound insulator. However, as also noted, I might not need a floating floor because my concrete slab is 150mm thick. The purpose of the Finnfoam is to insulate heat. If it insulates some noise, good. If it doesn't, I can live with that.
• The air conduits A friend, who builds HVAC-systems for a living, recommended some noise traps and isolation modules. I don't exactly know what yet, but I trust his judgement.
• The wall in between the two rooms The trick with this is to recognize the culprits - or bottlenecks or whatever you want to call them - of the other not so optimal structures, and find a solution that is not overkill. Then again, the difference in cost between building two stud frames instead of one is negligible. Space is what matters to me - every inch counts.
• The ceiling The ceiling too will have two layers of gypsum due to fire safery regulations.

This is a bit of a compromise, I know, but if the sound isolation is at least decent, I am happy. After all, most of the time it'll be just me writing code, practicing drums or recording myself.

What type of foam is that? Is it open-cell or closed-cell? You should never use closed cell insulation in studios: it is great thermally, but not much use acoustically.

Some information about Finnfoam here: http://www.finnfoam.com/finnfoam/

Whoooaaaa!!! Hang on there! Why do you have light switches and electrical outlets in your outer leaf??? They will all be covered up when you build your inner-leaf next to that...

Yes. As I explained, this is the only leaf of the outer wall. It is a compromise, I know, but keep in mind that this is a totally separate building. The only room that needs at least some isolation, is the control room. The yard? Nah.

It does not go down to the floor: Why? It seems to stop about 20cm or so up from the floor, so it is not a vapor barrier.

Because the foundation, which is made from light concrete blocks, is wrapped in Finnfoam, which acts as barrier. It does not let moisture through. After all the concrete itself emits moisture and that is why it has on every side either pressure treated wood or Finnfoam. The Finnfoam is here primarily a heat isolator as well.

Also, I see that on the wall, but not on the ceiling. There's a section in the far corner where the joists are visible, and clearly there's no vapor barrier up there.

Ah, there is a story here. The vapor barrier for the ceiling is indeed in place already, but has a big gaping hole in it. The previous owner had made a mistake in constructing the roof: he had placed the steel roof sheets to overlap too much and that's why he ran out. He apparently also ran out of money, because he didn't buy more, but instead just left the hole there for several years and the elements did their thing. Trust me, that will be taken care of, we are just not at that point yet. But we mended the hole a long time ago already.

A studio wall is a tuned system. There are two "leaves" of mass, and they are separated by an air gap, which is filled with porous open-cell insulation. The two leaves do not touch: there is no mechanical connection between them. Each leaf is usually built as a stud frame with drywall (and/or OSB, MDF, plywood/etc.) on only ONE side of that frame (never both sides). The entire system resonates at a specific frequency, often referred to as the MSM resonant frequency. "MSM" stands for "Mass-Spring-Mass", which is the most basic principle in physics of how resonant systems work: a massive support with a spring hanging from it, and another mass hanging on that spring. If you pull the bottom mass and let go, it will bounce up and down at a fixed rate that is governed only by the stiffness of the spring, and the amount of mass. A studio wall is the same in principle. You have a "mass" on one side (the first leaf), a "mass" on the side (the second leaf), and a "spring" in the middle (the air trapped in the cavity). Just like the mass bouncing on a spring, your wall resonates at one specific frequency when the two leaves oscillate due to the "springy" air between them. You have to "tune" the wall such that the resonant frequency is at least an octave lower than the lowest frequency that you need to isolate.

You tune the wall by choosing the correct mass (surface density) for each leaf, and the correct spring (depth of the air gap).

So, to answer your original question: the entire wall must have the same surface density at all points. If the surface density for the leaf needs to be (for example) 25 kg/m2, then you need to make sure that you have at least that much mass on every square meter of the wall, regardless of the building material. So where you have drywall, you need enough layers of drywall to get 25 kg/m2, and where you have glass, the glass needs to be thick enough that it too has a density of 25 kg/m2 (or more). And where you have doors, they also need to have a surface density of 25 kg/m3.

I'm not saying that your walls will need 25 kg(m2 in each leaf!!! I just chose that as an example. You will have to calculate what density you need for your walls, based on your own isolation level and isolation spectrum.

A wealth of information here. I will have more questions of this later, also regarding other wall FAQ threads I found here. I just can't type much more right now. But one thing, of course, would be some more specifics about how to do the calculations. I don't have much of a knack for maths, even though I do programming for a living, if you can believe that! If I want to block at 100 Hz, I need to calculate for 50 Hz. Question is: how?

Soundman2020 wrote:Whoooaaaa!!! Hang on there! Why do you have light switches and electrical outlets in your outer leaf??? They will all be covered up when you build your inner-leaf next to that...

All of your electrical installation goes inside your inner-leaf, never on your outer leaf. Also, you should use surface-mounted electrical system: you can't use normal electrical boxes, because that implies cutting large holes in your isolation leaf... If you cut a hole in your isolation, then you have no isolation....

I have thought of this a little bit more. Let's say some beautiful day I decide the isolation isn't good enough and want better, ie. come to my senses, and construct the second leaf for the outer wall. I still need electricity. I can pry open all the wall mounts and put some lids on them, repurpose some of them as junctions and redo the electrics that way. The outer leaf will have some holes in it, but such is life. But then what? How does the electricity travel to the correct side of the inner leaf? Through what hole where? How does that not compromise the inner leaf?

If I were to do that, I would have to think ahead with my heated floor as well. Now the plan is to insulate it from the outer wall with a 50mm foam. If it's bad to base a stud on the 50mm heated concrete slab, my only option is to somehow leave a gap between the outer wall and the side insulation of the heated floor.

I also have to let go of the ideal room-inside-a-room design.

In that case, you have also let go of any possibility of having usable isolation!

It really is that simple.

Sorry to be so harsh, but that's the simple truth.

So basically the purpose of the studio is:
That I can play the drums without annoying my wife
That I can record and mix music without annoying my wife

Without a decoupled 2-leaf wall, you can forget about both of those goals! Absolutely certain.

I'm not trying to be obnoxious: that really is the way it is.

If you do not have good isolation, you will never be able to play drums without it annoying people around you. It just isn't possible. There's a reason why ALL studios are built with 2-leaf walls, and this is it: for isolation.

Here's some math:

If you take a bunch of average, ordinary people to a really, really quite place, and slowly turn down the volume on some music you are playing while you measure the level, you will find that most of those people will say that it is "quiet" when you get to a level below about 40 dBC, and most of them will say it is "silent" when you get to a level below about 30 dBC. If you then tell them to do some task that requires a bit of concentration, such as reading a book, listening to the TV, writing, doing craft, surfing the internet, etc., then you start turning up the music again, they'll say that it is "annoying" at around 50 dBC, and "loud" at around 60 dBC.

That gives you an idea of where your goalposts are set here, about annoying your wife: You have to get the level down to about 40 dBC or lower, at the location where she will typically be. At the other end of the scale "playing drums" will produce a level of about 115 to 120 dB. That's the typical level of a normal drum kit.

The difference is the answer to the question: "How much isolation do you need?". 120 dB - 40 dB = 80 dB.

So, in order to make your loudest drumming "not annoying" for your wife, and "close to silent", you need about 80 dB of isolation.

80 dB of isolation, is a really, REALLY big deal! HUGE!

Fortunately, sound attenuates naturally over distance (it gets quieter as you move away from the sound source), so you don't actually need 80 dB unless your wife will by just one meter away on the other side of the wall. Assuming she's on the other side of the house, maybe 10m away, you can get by with less isolation.

Also, ambient sound tends to help mask your noise a little bit, so assuming that there's some low level of background noise in your neighborhood and in your house, you can also get by with a bit less.

Realistically, you will need something like 65 dB of isolation to achieve your goals. That's typically what studios are design for. Don't get confused here: I'm not talking about "STC-65" nor "65 Rw+C": I'm taking about 65 dB of actual transmission loss. That's what you need.

So how do you get 65 dB of isolation?

With a single-leaf wall, the answer is dead easy: You don't. You can't. It would be way too expensive, and take up way too much space to be practical. Nobody in their right mind would try to isolate a drum studio to 65 dB using just a single leaf wall.

Here's why:

In physics, there is an equation that tells you how heavy your wall will have to be to do that (how much mas do you need in your wall). It is called "Empirical Mass Law", and this is what it says:

Empirical real-world overall Mass Law transmission loss equation:

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

Where: Ms = Surface Mass in kg/m2

It's a very simple equation. You can plug in some values yourself, to see how much mass you need to get 65 dB of isolation.

I'll do it for you: the answer is 3,900 kg. You might be thinking that "Well, that's not so bad!". But look again. You need 3,900 kilograms PER SQUARE METER! Every single square meter of your wall will need to weight 3,900 kg, if you hope to get 65 dB of isolation from just a single leaf. Concrete weights about 2300 kg per cubic meter, so you could make your wall from solid reinforced concrete, 1.69 meters thick (yes, 169 cm)... Steel is higher density, and weighs about 7900 kg/m3, so you could make your wall from a single solid steel plate, just 49 cm thick. If you wanted a thinner wall, you could use something that is even heavier, such as lead for example. Lead weighs about 12,500 kg per cubic meter, so you could make your wall from solid lead sheeting, 31 cm thick...

Those are the real, solid, true numbers for single-leaf isolation. You can check the equation yourself, and do the math yourself if you don't trust what I am saying.

This is the reason why NOBODY tries to build studios that need high isolation, using single leaf walls: IT is way too expensive, and takes up way too much space. Huge money waster, huge space waster. Calvin would spin in his grave (he was rather efficient, and austere in his personal life... he did not like wastage...)

What I value most is space, which means I am very hesitant to give up any of it.

Then you better not build a single leaf wall! You will lose a huge amount of space if you do. Assuming you go with something reasonably "cheap", such as concrete, your walls would need to be over 1.5m thick. That's a LOT of space to be wasting!

also have to let go of the ideal room-inside-a-room design. That eats up some valuable space too

No it does not. In fact, it SAVES you a huge amount of space. To get 65 dB of isolation from a 2-leaf wall, you do NOT need to make it 1.5m thick (concrete). Not even 31 cm thick (lead). You can do it in much less space than that.

I have too many people to convince about it and it's all just a bit too much.

I'm not sure where those people are getting their information from, but it is totally wrong. Totally. Completely. Absolutely. Wrong. They should start looking at correct information, or your studio will be a disaster that does not even come close to isolating. Nobody will be happy with the outcome. Not you, not your wife, and not "people".

What that means, is that I will have one wall with two leaves and that is the wall between the studio and the control room.

... which would be useless.

You cannot isolate a studio by isolating only one wall. That's the same as saying "I want to build an aquarium for my fish, but I will only put glass in one side"....

I am prepared to put effort in it to get a maximum efficiency wall.

You would be wasting all of that effort. A studio that has only one isolation wall is exactly like the aquarium that has only one glass side: with the aquarium, water will rush out all over the place in all the other directions, going around that single glass side. With your studio, sound will rush out in all the other directions, through all the other non-isolated walls, going around that one "high efficiency" wall. It would be a total waste of time and money.

I do know that the outer wall has only one leaf.

Then I do also know that you have no isolation! it is that simple. Sound will go around your one good wall, and along it, and inside it it, and it WILL get form the Live Room to the Control Room, via that outer wall, and all the other walls. This is a simple fact. It is called "flanking" in acoustics, and you will have major flanking paths, with very high transmission.

As to how much it isolates to the outside, that is not a concern.

Yes it is: You seem to be missing the big picture here! Sound does not travel in straight lines, so putting a good wall between point "A" and point "B" will not stop the sound from getting through.

Think of this: If you are standing in the ocean, and you want to stop the water getting to you, do you think that you can achieve that by building just one single barrier between you and the direction the waves are coming? Nope. It does not work. You will still be soaking wet, and the waves will still get to you. Sound is waves....

I do know that sound will travel from the studio to the control room at least through:
The outer wall The outer wall will have two layers of gypsum per fire safety regulations

Two layers of gypsum board ("drywall") weighs about 20 kg/m2. You need 3,900 kg/m2. Are you getting the picture?

... make your wall 195 times thicker, and you will get the amount of isolation you need...

The air conduits A friend, who builds HVAC-systems for a living, recommended some noise traps and isolation modules. I don't exactly know what yet, but I trust his judgement.

He's right, but you would be wasting your time and money if you only have one wall and a couple of HVAC silencers. Sound would flank around all of that, doing through the weakest, simplest paths: the other walls, the ceiling, the electrical system, the windows, the doors....

But anyway, here are some examples of silencer boxes that have been built by forum members:
http://www.johnlsayers.com/phpBB2/viewt ... 0&start=45
http://www.johnlsayers.com/phpBB2/viewt ... 9&start=74
http://www.johnlsayers.com/phpBB2/viewt ... 25&start=2
http://www.johnlsayers.com/phpBB2/viewt ... 42&start=5
http://www.johnlsayers.com/phpBB2/viewt ... 61&start=0
http://www.johnlsayers.com/phpBB2/viewt ... 5&start=98
http://www.johnlsayers.com/phpBB2/viewt ... &start=157
http://www.johnlsayers.com/phpBB2/viewt ... =2&t=13821
http://www.johnlsayers.com/phpBB2/viewt ... 8&start=44
http://www.johnlsayers.com/phpBB2/viewt ... 2&start=16

Each of those was specifically designed for the studio where it is used.

The trick with this is to recognize the culprits

... which you are not doing! You are NOT recognizing the culprits. You are recognizing only one single thing that YOU think is the culprit, but in reality it is only one of MANY culprits, and they are ALL responsible, in equal measure.

or whatever you want to call them - of the other not so optimal structures, and find a solution that is not overkill.

Once again, you are missing the big picture. Sound does NOT behave they way you are imagining it behaves. You are assuming that it behaves something like light, and you can create a shadow by just putting up an umbrella. But sound does not behave like light: it behaves like ocean waves. Can you stop the ocean waves by putting an umbrella in front of you?

Then again, the difference in cost between building two stud frames instead of one is negligible. Space is what matters to me - every inch counts.

You keep on saying that space is so important to you, yet you keep on wanting to build a wall that will take up huge amounts of space...

This is a bit of a compromise, I know, but if the sound isolation is at least decent, I am happy.

I hate to break this to you, but you will NOt be happy, because the sound isolation will not be decent. It won't even be "almost decent". It will be "way, far, extremely distant" from "decent".

After all, most of the time it'll be just me ... practicing drums or recording myself.

Let me put that in nautical terms: "After all, most of the time it will just be me and my umbrella ... in the middle of a hurricane. I'm sure my umbrella can stop a hurricane! Even if it doesn't stop it, it will reduce it to acceptable levels, for certain...."

Yes. As I explained, this is the only leaf of the outer wall. It is a compromise, I know, but keep in mind that this is a totally separate building. The only room that needs at least some isolation, is the control room.

???? Huh? That doesn't even make sense! You will have your drums inside the Live Room, not the control room. The LOUDEST room needs the isolation, not the quietest one. You seem to be approaching this totally backwards.

this is a totally separate building. The only room that needs at least some isolation, is the control room. The yard? Nah.

Maybe I'm totally wrong here, but I thought you were trying to isolate the sound so that your wife does not get annoyed? I'm assuming that she is no the house, on the other side of the yard?

After all the concrete itself emits moisture

Why???? What is wrong with your concrete???? If your concrete has damp issues, then call the contractor immediately and get them to fix it! Concrete should NOT EVER "emit moisture". Here's the most important piece of advice I can give you so far: if your concrete slab is suffering from damp problems DO NOT BUILD A STUDIO ON IT! Don't. Just don't: Don't even think of doing that. Properly poured and properly cured concrete should not ever, under any circumstance, be constantly damp. If yours is damp, or seems to be emitting moisture, then it has a BIG problem, and before you do anything else you need to get that fixed. I can't stress this enough! Get it fixed. do not build on a damp slab. You will end up with serious health issues, and serious structural issues.

It does not go down to the floor: Why? It seems to stop about 20cm or so up from the floor, so it is not a vapor barrier.

Because the foundation, which is made from light concrete blocks, is wrapped in Finnfoam, which acts as barrier. It does not let moisture through.

You seem to be misunderstanding the point. I'm not talking about your moisture barrier, which goes on the outside surface of the wall. I'm taking about the vapor barrier, which goes on the inside surface of the inner leaf. The moisture barrier does not stop vapor, and the vapor barrier does not stop moisture. They are two very different things, with very different purposes, and they go in very different places in the wall. If you do not put them in the correct place, installed correctly, then you will have problems with mold, humidity, rot, structural failure...

What I'm talking about is the vapor barrier visible in that photo: it is not done correctly, since it is not sealed, and does not reach the floor. if you don't fix that, then you WILL have all the problems that vapor barriers are designed to prevent.

The Finnfoam is here primarily a heat isolator as well.

Then it is also in the wrong place. For very cold climates, such as Finland, where the ground itself freezes, you should have thermal insulation on the outside of the foundations, not the inside. The insulation goes between the ground and the concrete, to prevent the concrete from "heaving" as the ground freezes and thaws to different levels.

A wealth of information here. I will have more questions of this later, also regarding other wall FAQ threads I found here. I just can't type much more right now. But one thing, of course, would be some more specifics about how to do the calculations.

The equations for two-leaf MSM isolation are a bit more complicated than for Mass law, but not hard at all. Mass Law is very simple, and very lousy for isolation, which is why studios are never done like that. Way too expensive, way too much mass, way too much waste of space.

Two-leaf MSM walls, on the other hand, need a LOT less mass (you can get 65 dB of isolation with much less than 1/10th the mass you'd need from Mass Law), and a a LOT less space (much less than 1/5th the total wall thickness). Which also makes it MUCH cheaper. Which is why studios are built this way, almost exclusively...

The outer leaf will have some holes in it, but such is life.

You might want to look at this graph: Look at the top line on that graph: that shows the isolation for a wall that is designed for 60 dB of isolation, which is similar to what you need. Now look at the point on that curve marked with the arrow: That shows how much real isolation you get from that wall, if you have a hole in it that represents just 0.001% of the total area. Assume your wall is 5m long by 2 m high, so it has a surface area of 10m2. That's 100,000 cm2. If you have one single hole in that wall, that is just 1cm2 in size, then you totally destroy the isolation of the entire wall. Instead of giving you 60 dB of isolation it will give you only 48 dB of isolation: Just one tiny little hole will completely, totally, utterly eliminate all of the isolation. Your holes are MUCH bigger than 1 square cm...

Are you SURE you want to have holes in your wall?

But then what? How does the electricity travel to the correct side of the inner leaf? Through what hole where? How does that not compromise the inner leaf?

Through conduit. Like this: Ordinary electrical conduit with a gap that is wrapped in rubber. Simple. Effective.

If I were to do that, I would have to think ahead with my heated floor as well. Now the plan is to insulate it from the outer wall with a 50mm foam. If it's bad to base a stud on the 50mm heated concrete slab, my only option is to somehow leave a gap between the outer wall and the side insulation of the heated floor.

So put down your sole plate for the inner-leaf wall now, even if you don't build the wall yet! Simple.

It seems to me that you are rushing ahead with this studio build, yet you don't have the necessary acoustic or construction knowledge to do it, and you don't have the experience, and you don't even have a design! You should first learn how to do it, then design it, and only then start building it. The forum is full of threads from people who came here in similar situations. Some of them stopped, took the time to learn, then carried on building and ended up with great studios, Others did not stop, and carried on anyway, convinced that they were right, we were wrong, and they would end up with excellent results by using their own method.... we never heard from those people again. They never came back to show us how well "their method" worked... I wonder why? I can accurately predict how their studios ended up, even though they never told us, because the laws of physics are true everywhere, for all people. The equations work, and they show what the outcome will be for those people. The equations work, even for those people who don't like them, or don't agree with them, or don't understand them. Not even Calvin himself could build a studio based on "other" equations that predict "different" laws of physics. When God created the universe, he also created all those laws of physics and all the equations that describe them. As far as I know, nobody has ever been successful in convincing Him to waive those equations for their studio...

I'm hoping you will be one of the smart ones, who stops, learns, designs, then does it right. Not one of the "others", who goes ahead and does it wrong, wasting a lot of time, money end effort, hoping that the equations and laws won't apply to them.... then getting really lousy results.


- Stuart -

In that case, you have also let go of any possibility of having usable isolation!

It really is that simple.

Sorry to be so harsh, but that's the simple truth.

I appreciate you being honest. I hope I'm not annoying you with too many "yeah buts", but what you define as usable might be very different from what I define as usable. The stucture I am aiming for might not get me 65 dB, but what I am interested in at this point, is not what it can't do, but what it can do. Surely the isolation won't be 0 dB, so what can be achieved this way and what would it sound like? For instance, would I be comfortable without hearing protection in the control room when somebody else plays the drums in the studio? Could I have a conversation with somebody in the control room without having to yell over the noise to be understood? How about somebody speaking or yelling on the other side? You might come to visit my studio when it is finished and say: "man, the isolation is very very bad", but I might reply: "why? I think it's fine." Our definitions for what is "good" or "enough" may be very different.

So basically the purpose of the studio is:
That I can play the drums without annoying my wife
That I can record and mix music without annoying my wife

Without a decoupled 2-leaf wall, you can forget about both of those goals! Absolutely certain.

Well, not really. She's going to be in a totally different building. The garage I'm building the studio in is a separate building from my house and is located at the opposite side of the yard. Those two goals are practically achieved as soon as the heat is turned on in the garage. No sound isolation necessary for those. See, my current situation is this: I have a single room where I have my desk and my drums. I have recorded drums there. I have recorded other people playing drums there. The room is only slightly bigger than the control room in my plan. Compared to that, anything is an improvement.

I'll do it for you: the answer is 3,900 kg. ... This is the reason why NOBODY tries to build studios that need high isolation, using single leaf walls.

Yeah, I get the picture. I'm not suggesting absurdities, I just want to know what is possible and not only what isn't. I'm not saying I need such and such isolation and it needs to be single-leaf. It's more like here's what I've got and I'd like to know what I can achieve with it and whether or not there is anything I can do to max it out. If indeed becomes apparent later that I just can't live with this (or hunger grows while eating, dunno if that idiom works in english), I can make preparations in such a way, that I can build the second leaves when time and budget allow. For now the goal is just to move my work and my noisy hobbies out of the house and into the garage.

Regarding future proofing, I came up with something like this: With the second leaf in place it could look like this: When I discussed with my contractor about the heating floor, he told me that putting vertical thermal insulation (the blue ones) is not necessary. I was under the impression, however, that they would be beneficial by "floating" the heating slab off other structures. Seeing now that that isn't really what a floating floor is all about and realizing that most likely I don't need one, as has been pointed out in this thread and many many many many others, I wonder, if it could look like this:

I do know that the outer wall has only one leaf.

Then I do also know that you have no isolation! it is that simple. Sound will go around your one good wall, and along it, and inside it it, and it WILL get form the Live Room to the Control Room, via that outer wall, and all the other walls. This is a simple fact. It is called "flanking" in acoustics, and you will have major flanking paths, with very high transmission.

Thank you, this was very helpful. Is there a way to get a grasp on how much the transmission would be? Will the sound not dissipate at all, when travelling along a wall? When you say "no isolation", you don't really mean 0 dB, or do you really honestly mean, that it is exactly the same as being physically in the same room or that it is absolutely the same as your average wall in an average house, not sealed air tight, big air gaps in doors etc...? When you write using such extremes, I have to wonder if it is just your style of writing and what do you really mean by what you say.

???? Huh? That doesn't even make sense! You will have your drums inside the Live Room, not the control room. The LOUDEST room needs the isolation, not the quietest one. You seem to be approaching this totally backwards.

I'm sorry, I wrote in a way that caused you to misunderstand. I only wanted to communicate that the birds and the frogs and the occasional snake don't care (ok, maybe they do, but I don't ). Only the guy sitting in the control room cares. So the control room is the only place that needs less noise to come in (which is what I mean by "isolation", wrong term to use here, which caused you to misunderstand). You are totally right about the loudest room needing the isolation. The quiet room needs the "results" of the isolation. We are on the same page here.

Are you SURE you want to have holes in your wall?

Yeah, but ( ) again, the noise that escapes through those holes goes outside. The snakes and the birds and the frogs don't care. Or are you suggesting that having a hole in the outer leaf somehow also amplifies flanking?

So put down your sole plate for the inner-leaf wall now, even if you don't build the wall yet! Simple.

If some of the illustrations I provided is good in your opinion, this will not matter, but what do you mean by "sole plate"?

Others did not stop, and carried on anyway, convinced that they were right, we were wrong, and they would end up with excellent results by using their own method.... we never heard from those people again.

It's not my intention to come across arrogant like that. I'm not saying you are wrong and I'm right. The thing is, Stuart, we talk a bit past each other. You think I expect wonders out of something that can't produce any, when that is not the case. I have small and humble goals and I'm willing to accept the facts if need be. I'm not imposing anything or being stubborn on purpose. I just want to know what to expect.

I did this drawing today. How would this work? The outer wall is about 25cm thick, I think. In this drawing the inner leaf is based on a 10cm/4" wide base plate and the gap between it and the outer leaf is 5cm, thus the air gap in total would be 15cm. In the wall between the studio and the control room the total air gap is 25cm in this drawing, mainly because it was easy to draw it in such a way. Any comments?

Howdy how! My studio project is taking steps forward.

I still have some unanswered questions here though.

This is my latest plan for the inner walls: I decided that I will get annoyed at some point of having to always exit the building and enter again through a different door. So I added a couple of doors to my plan and a wall to form a sort of lobby where people can take off their coats and hang them on the wall. The wall between the garage and the reset of the building is almost finished. Next up will be building the studio walls.

I am going to layer two different thickness sheets of drywall. I have available for instance:
http://www.gyproc.fi/tuotteet/43/levyt/ ... rikoiskova 12.5mm thick, 9.9kg/sqm
http://www.gyproc.fi/tuotteet/43/levyt/ ... 15-lapikas 15.5mm thick, 15.4kg/sqm, question: Sold as designed for floors. Is it a problem?
Question: Will this do? Or is this overkill? Have I understood correctly that the top layer needs to be glued and not screwed or nailed? I do not see emphasised in other threads that the drywall sheets should be different thickness. Is that not important then?

I will not be using green glue. It is not available here and I would have to import it by the caseload. I am intrigued by the idea on this page http://johnlsayers.com/Recmanual/Titles/Acoustics3.htm (at the bottom) of putting fiber board in between the layers. Question: Is it worth it?

There will be a window. I found a dealer online who stocks two different thicknesses of laminated glass: 4mm + 1.5mm + 4mm and 6mm + 1.5mm + 6mm. They have both treated and untreated available. Question: Will treated glass make a difference? Are these good thicknesses? The thicker glass should go on the control room side, right?

I spotted an issue:
If I do a room inside a room, I need to sort out this ventilation issue. The air vents and ducts are already there. Question: How do I solve this? If I just penetrate the inner leaf and extend the duct, I end up compromising the isolation.

I am going to layer two different thickness sheets of drywall. I have available for instance:

Why? There's no real advantage to that. Better to make both layers as thick as possible.

I do not see emphasised in other threads that the drywall sheets should be different thickness. Is that not important then?

Correct: It is not important.

Have I understood correctly that the top layer needs to be glued and not screwed or nailed?

No, you have not understood correctly. You should never glue layers of drywall together. You should only ever use nails or screws to attach the drywall.

They have both treated and untreated available. Question: Will treated glass make a difference?

What do the mean by "treated"? In what way has the glass been "treated"?.

Are these good thicknesses? The thicker glass should go on the control room side, right?

No. For each leaf, the surface density of the glass should be the same as, or greater than, the surface density of the leaf itself. You would only need thicker glass on one side if the leaf on that side had a higher surface density that required it. As long as the surface density of the glass is sufficient, there is not really any need to have differing thicknesses. Coincidence is unlikely to be a major problem, in typical home studios. If you have isolation problems at coincidence, then you will have even bigger problems lower down the spectrum.

If I do a room inside a room, I need to sort out this ventilation issue. The air vents and ducts are already there. Question: How do I solve this? If I just penetrate the inner leaf and extend the duct, I end up compromising the isolation.

Right. Which is why you need to build a silencer box for each penetration of each leaf. silencer boxes like like this:

http://www.johnlsayers.com/phpBB2/viewt ... 0&start=45
http://www.johnlsayers.com/phpBB2/viewt ... 9&start=74
http://www.johnlsayers.com/phpBB2/viewt ... 25&start=2
http://www.johnlsayers.com/phpBB2/viewt ... 42&start=5
http://www.johnlsayers.com/phpBB2/viewt ... 61&start=0
http://www.johnlsayers.com/phpBB2/viewt ... 5&start=98
http://www.johnlsayers.com/phpBB2/viewt ... &start=157
http://www.johnlsayers.com/phpBB2/viewt ... =2&t=13821
http://www.johnlsayers.com/phpBB2/viewt ... 8&start=44
http://www.johnlsayers.com/phpBB2/viewt ... 2&start=16

But you also need to do the math: You need to ensure that the cross sectional area of each part of your HVAC system is correct, such that you are delivering the correct air flow rate (room changes per hour, CFM, M3/h, volume per unit time) at the correct air flow velocity (fpm, M/S, distance per unit time), while keeping the static pressure low enough that the AHU or HRV fan can handle it, while also ensuring that the cross sectional area changes by a factor of at least 2 at the entrance and exit of each silencer box, and that the final path into the room is long enough that the turbulent flow is minimized at the register, and also ensuring that the surface density of the silencer box walls is sufficient to maintain the level of isolation required for the room...

It's quite a challenge! It takes a bit of math and ingenuity.

Also, your control room does not appear to be symmetrical: That's a critical issue, and should be corrected.

Another thing: Your control room is not isolated. The inner-leaf walls on two sides connect directly to the outer leaf walls of the building on the other two: = very poor isolation.

And one more: Your sound lock has no inner leaf wall. That also need to be corrected.

I would also suggest putting a window in the wall between the CR and LR. Visual contact is important for musicians and engineers.



- Stuart -

Soundman2020 wrote:

I am going to layer two different thickness sheets of drywall. I have available for instance:

Why? There's no real advantage to that. Better to make both layers as thick as possible.

[/quote]

This is what creates doubt in me. I want to learn and I try to gather information, but the information I gather is contradicted right away. This page http://johnlsayers.com/Recmanual/Titles/Acoustics3.htm says:

Adding another layer of gypsum which is glued (not nailed) to the first sheet and should be a different thickness than the first sheet. i.e. 16mm (5/8") and 12mm (1/2") (emphasis mine)

I'm fine doing it either way, but this isn't very encouraging to me.

What do the mean by "treated"? In what way has the glass been "treated"?.

To make it harder, as in bullet proof glass. In Finnish it is karkaistu lasi and I think it means safety glass, according to this page: http://fi.linguee.com/suomi-englanti/k% ... +lasi.html

So does it make a difference to have safety glass as opposed to regular glass?

Right. Which is why you need to build a silencer box for each penetration of each leaf. silencer boxes like like this:

http://www.johnlsayers.com/phpBB2/viewt ... 0&start=45
http://www.johnlsayers.com/phpBB2/viewt ... 9&start=74
http://www.johnlsayers.com/phpBB2/viewt ... 25&start=2
http://www.johnlsayers.com/phpBB2/viewt ... 42&start=5
http://www.johnlsayers.com/phpBB2/viewt ... 61&start=0
http://www.johnlsayers.com/phpBB2/viewt ... 5&start=98
http://www.johnlsayers.com/phpBB2/viewt ... &start=157
http://www.johnlsayers.com/phpBB2/viewt ... =2&t=13821
http://www.johnlsayers.com/phpBB2/viewt ... 8&start=44
http://www.johnlsayers.com/phpBB2/viewt ... 2&start=16

But you also need to do the math: You need to ensure that the cross sectional area of each part of your HVAC system is correct, such that you are delivering the correct air flow rate (room changes per hour, CFM, M3/h, volume per unit time) at the correct air flow velocity (fpm, M/S, distance per unit time), while keeping the static pressure low enough that the AHU or HRV fan can handle it, while also ensuring that the cross sectional area changes by a factor of at least 2 at the entrance and exit of each silencer box, and that the final path into the room is long enough that the turbulent flow is minimized at the register, and also ensuring that the surface density of the silencer box walls is sufficient to maintain the level of isolation required for the room...

It's quite a challenge! It takes a bit of math and ingenuity.

Right. This I could really use some expert help for.

I did some more drawing. Here's one idea:
I took some cues from John's corner control room plan. I started with a 3.5x3.5m square and shaped into a diamondy shape. The longest two sides are 2.93m each. Is that a decent size? I have absolutely no idea if this is a good shape/size and what sort of acoustic treatment it's going to need.

Then I got another idea: what if I flip the whole thing?
I think this one has some very clear advantages space usage wise, but also some challenges HVAC-wise. Not that the one above doesn't have those, though.

Okay, some things are starting to click here.

I borrowed (stole) this picture from this thread: http://www.johnlsayers.com/phpBB2/viewt ... 16#p129758 I get it what he is doing here. He has basically inverted the inner leaf, so that the dampened side faces inwards. Then he covers the whole wall with fabric. But now, because the space is acoustically pretty much dead, he must make it resonate and reverberate, which is what the slats are for. So you either build a lively space and treat it to tame down the resonance and reverb, or you build a dead and dampened space and make it resonate and reverberate. Did I get it right? The problem for me, though, is that if I were to put the inner leaf frame at 50mm distance from the outer leaf and invert it like he did, I would have just 50mm of air between the leaves. I don't know if that would be enough.

What I really like about his design, is how he mounted the silencers. I could not see from the photos, whether or not the silencer box touches the drywall of the inner leaf. Does it? Should it? Should it not? Also, his silencer box is before the penetration. Would that also work when the resonant side of the inner leaf faces inside? That would result as a big clunky box mounted on a wall, I know, but technically, would that work? Essentially, is it always imperative that the silencer box is after the penetration or can it be before the penetration, without significantly compromising the isolation?

Also I noticed he has an air pump. I take it that the ducts and cables for the inverter unit are small enough in diameter and insulated in such a way, that he just appears to have poked a hole through and sealed it with caulk. At least I can't see any other kind of special attention being paid to those. You can correct me if I am wrong. It just means that it wouldn't be absolutely necessary for me to think that much ahead at this point about a heat pump. As I've said before, I want a heated floor. But if the first summer proves the space to be hot and uncomfortable, I might want a heat pump too, because it can act as a cooler unit, but I don't know that yet.

Oh well. So much to think about. So many difficult decisions to make.

I went and took some pictures, so you can see better, what kind of space I am working with here. It is a space approx. 7.3m long and 5.6m wide, with a ceiling height of about 3.3m. I also recorded a short video, maybe it can give you a better sense of the space: https://www.youtube.com/watch?v=JyHnek9X0WA

BIG QUESTION: As you can see, the outer leaf is unfinished, ie. not caulked, not sealed, not sanded, not anything. Is it essential that both leaves are as air tight as possible or is it only the inner leaf? I'm not that worried about sound escaping outside, it's the control room I don't want noise to come in. If it is importand to caulk the outer leaf too, I'll know what to do for the next several weeks. But what should I use? Acoustic caulk for everything? Or the basic stuff one is supposed to use when isolation is not a factor? What should I do with the existing electrical cups? The electrics can be rerouted and extended, but those are pretty big holes...

I borrowed (stole) this picture from this thread: http://www.johnlsayers.com/phpBB2/viewt ... 16#p129758

slats3.jpg

This actually one of my builds

I get it what he is doing here. He has basically inverted the inner leaf, so that the dampened side faces inwards. Then he covers the whole wall with fabric. But now, because the space is acoustically pretty much dead, he must make it resonate and reverberate, which is what the slats are for. So you either build a lively space and treat it to tame down the resonance and reverb, or you build a dead and dampened space and make it resonate and reverberate. Did I get it right? The problem for me, though, is that if I were to put the inner leaf frame at 50mm distance from the outer leaf and invert it like he did, I would have just 50mm of air between the leaves. I don't know if that would be enough.

This is John Sayers infamous inside out wall, or at least where I learned its existence.
You are correct on taking a dead space and putting some live acoustics back in the room. The aesthetic feel can change the overall appearance of the room. Plus protecting the fabric from gear and people leaning against it. Your outer leaf I am assuming is 90 mm deep with insulation. and your inner leaf is 50 mm away from it. Then in fact you would have a 140 mm air gap. Which is what I did, and ended up with great isolation.
In my last build I did a combination of in side out and hard wall surfaces http://www.johnlsayers.com/phpBB2/viewt ... 1&start=15

What I really like about his design, is how he mounted the silencers. I could not see from the photos, whether or not the silencer box touches the drywall of the inner leaf. Does it? Should it? Should it not? Also, his silencer box is before the penetration. Would that also work when the resonant side of the inner leaf faces inside? That would result as a big clunky box mounted on a wall, I know, but technically, would that work? Essentially, is it always imperative that the silencer box is after the penetration or can it be before the penetration, without significantly compromising the isolation?

The silencers are mounted on the interior leaf and are connected to the outside vent via a rubber flex pipe. Maximum TL loss would be to have a silencer on both leaves. However the amount of sound escaping the the outside is not audible at 10 feet away from the structure. And even right next to the exterior vent it is very minimal.

Also I noticed he has an air pump. I take it that the ducts and cables for the inverter unit are small enough in diameter and insulated in such a way, that he just appears to have poked a hole through and sealed it with caulk. At least I can't see any other kind of special attention being paid to those. You can correct me if I am wrong. It just means that it wouldn't be absolutely necessary for me to think that much ahead at this point about a heat pump. As I've said before, I want a heated floor. But if the first summer proves the space to be hot and uncomfortable, I might want a heat pump too, because it can act as a cooler unit, but I don't know that yet.

A mini split (in my opinion) is the best way to go. Cost effective in the long run. No vents to worry about. Air movement is very quiet in these units and yes the only penetration are the Freon tube and humidity line that need a place to drain too. We did have to add a humidifier to keep the room at a perfect level for his guitars. The mini split will dehumidify the room.

Hope this helped
Peace
T

Thanks for hopping in, Tom!

TomVan wrote:Your outer leaf I am assuming is 90 mm deep with insulation. and your inner leaf is 50 mm away from it. Then in fact you would have a 140 mm air gap. Which is what I did, and ended up with great isolation.
In my last build I did a combination of in side out and hard wall surfaces http://www.johnlsayers.com/phpBB2/viewt ... 1&start=15

No, not unless I totally misunderstood you now. My outer leaf has a hard surface, it is zero mm deep. It means I should put the inner leaf surface at least at the minimum distance, which is 100mm.

The silencers are mounted on the interior leaf and are connected to the outside vent via a rubber flex pipe. Maximum TL loss would be to have a silencer on both leaves. However the amount of sound escaping the the outside is not audible at 10 feet away from the structure. And even right next to the exterior vent it is very minimal.

Very helpful, thank you. This is probably the way to go for me.

A mini split (in my opinion) is the best way to go. Cost effective in the long run. No vents to worry about. Air movement is very quiet in these units and yes the only penetration are the Freon tube and humidity line that need a place to drain too. We did have to add a humidifier to keep the room at a perfect level for his guitars. The mini split will dehumidify the room.

What is a mini split? You lost me there, I'm afraid.