LET THE FUN BEGIN - NEW STUDIO CONSTRUCTION - EUROPE

Ouch! That's what I suspected. So I do have some bad news for you: the OSB and the two layers of drywall will probably have to come off the inside

:shock: I am afraid this would run the construction project of my budget limits. Second problem, the OSB boards are there also as vapor barrier, can't take them off even if I wanted to. We have to search/find another way (cheap if possible) to thicken the walls from the inside without adding the 3rd leaf effect. So far the loudest sound of the cars don't penetrate the room. I don't think it's really that bad situation, is it?

By looking at this photo.. Can't we just make the outisde walls to look like STC50 example?

How about adding the STC63 example to the existing outside wall structure?

Seems like a good time for an inside out wall backed directly up to the inner boundary of the exterior perimeter.

English is not my native language. My head already hurts by reading so many threads :shock: Any chance to see some illustration of your suggestion? Please :D

Can't we just make the outisde walls to look like STC50 example?

Yes, but do realize that STC is NOT a good way of measuring isolation for studios. STC is good at measuring isolation for voice, not for music. It deals with the area of the spectrum where voices live. not where modern music lives, and certainly not where heavy metal and car engines live! The way STC is calculated does not consider any frequency band below 125 Hz. So no bass guitar, no kick drum, no toms, no lower octaves on keyboards, no other stuff in the low end... All of that is simply off the chart in STC. And "all of that" is exactly where you have the biggest issues with three-leaf walls. A three leaf wall is really, really good at isolating high frequencies, but really, really bad at stopping low frequencies. It is BETTER than a 2-leaf for highs, and WORSE than a 2-leaf (worse even than mass law!) for lows. So, knowing that, the sequences of images you show tell you nothing at all about low frequencies, since the method used to calculated STC does not even consider low frequencies. OK, if you want to get more technical, all of this is because a 2-leaf MSM wall is a tuned system: it has a resonant frequency, which is governed mainly by two things: the mass on each leaf, and the depth of the air gap between the leaves. A good MSM wall is tuned such that its resonant frequency ls way lower than the lowest end of the audio spectrum that we humans can hear. In other words, it is tuned well below 20 Hz. In fact, ideally it should be tuned lower than half of the lowest frequency, so a really good MSM wall is tuned to somewhere less than 10 Hz. When you do that, it isolates well from 20 Hz on upwards. But if you add a third leaf next to it, with another air gap, then you RE-TUNE the entire system! You actually force the resonant frequency of the entire system to go up, to a much higher frequency. How much it changes depends on about one zillion and thirty seven factors (!), but chances are you will drive the resonant frequency up high enough that it is into the low end of the human hearing range, meaning that the wall now passes sound in that range, instead of blocking it. (Worse still, it can actually amplify sound passage through the wall....). But you won't see any of that by comparing the STC ratings of walls. You'd have to compare the transmission loss (TL) ratings to see that. OK, so, what to do? Like I said, the tuning depends mainly on mass and air gap. So if you DO have a 3-leaf system, and there is nothing you can do about it to make it back to 2-leaf, then you can compensate by adding mass to the leaves, and also putting in a much larger air gap than you would need otherwise. So, to cut a long story short, you can build your inner-leaf, and the complete system will look like the "STC-50" case, but you will need much more mass on the leaves, and a much larger air gap to drive the frequency down again to a point where the wall performs well once more at the low end. Short answer? You can do it, but it is going to cost you mass and floor space.

How about adding the STC63 example to the existing outside wall structure?

You don't have the STC-63 structure! That is what I was trying to get you to by removing the OSB and drywall. What you actually have right now is the STC-36 structure... (except that you have more mass on it, and a bigger air gap, so it will be a bit better than STC-36). The difference is that the two sides of your existing wall are coupled by the studs. Any vibration in one leaf is transmitted through the studs directly to the other leaf, which then vibrates in sympathy. To get isolation, you have to break that direct connection between leaves. This is called "decoupling". Since you don't have that and can't get it, you have no choice but to build a 3-leaf that is much more massive and has much larger air gaps. Or you could just move the vapor barrier to the new wall.... - Stuart -

Sounds like I am in a real trouble here :cry: Let me ask you another thing. Just need to draw it first.

Would this solve anything? Dampen the whole front area with rock wool from top to bottom and in this way avoid creating the 3rd leaf. I just saw Lou's control room where he kept the front walls fully insulated and covered with fabric. Somehow I have to find an affordable solution.

Would this solve anything?

It won't "solve" anything, and you pretty much have to do that anyway: the areas you point to are the cavities behind your speaker soffits, and they certainly do need to be damped with insulation. But that is not related at all to the isolation issue that you have. The soffits are not even part of the isolation: they are a totally separate thing. They are INSIDE the inner leaf, not part of it.

Dampen the whole front area with rock wool from top to bottom and in this way avoid creating the 3rd leaf.

You would still have a third leaf. Rock wool does nothing at all to eliminate or create leaves. The only way to create a leaf is to put a massive surface over an air gap. The only way to get rid of a leaf is to remove either the massive surface or the air gap. Filling the air gap with rock wool does not remove the air gap: it only damps it. Rock wool is nowhere dense enough to do that. If you were to fill it with concrete, that would work! So, you need to decouple your wall and create that third leaf (if you cannot move the vapor barrier, which I think you actually can do), Your diagram does not show the decoupling that you will need between your outer an inner leaves (regardless of how you build them). You MUST have total decoupling between your inner leaf and outer leaf, as shown (very roughly!) here: See how I created a white area inside the walls? That represents your air gap. It is your decoupling. It MUST be totally disconnected (mechanically): No part of the inner leaf can touch the outer leaf at all (except at the floor). It doesn't matter too much how the outer wall is built, and how the inner-wall is built: In your case, the outer wall will be a two-leaf coupled system (what you have already), and the inner wall will be a single-leaf on a stud frame. So you will have a three-leaf system, which is bad like I said before, but you can compensate for that by adding more mass to both the existing wall, and also to the the new inner leaf, plus by making the air gap (the white area on my rough sketch, above) bigger than it would have to be normally. Usually, for a two-leaf wall, you need at least a 4 inch air gap (10cm). For your three-leaf wall, you will probably need something more like 8 inches (20 cm). This is what I mean by decoupling, and air gap, and 2-leaf. I'm not sure if I'm explaining myself clearly, but I hope so! These are not easy concepts to understand the first time you see them, but sooner or later I'm sure you'll get the idea. But I'm still thinking that it would be much easier to take off the OSB and drywall, and the vapor barrier, then move the vapor barrier to the new wall, the inner leaf.... Yes, you obviously do need a vapor barrier, and yes it does need to go on the inner surface of the wall in the country where you live. So you would simply put a new vapor barrier on the new inner-leaf wall, right behind the first layer of drywall, just as you have it now. The only difference is that it will be on a different set of studs. It shouldn't be a big deal to move your vapor barrier, as long as it stays in the right place. In fact, if you DON'T move it, then I suspect that you might run into problems: if you leave it where it is and then build that third leaf, then the vapor barrier will no longer be up against the warmest surface: it will be in the middle of the wall, and I suspect you might get condensation problems. (In any event, I don't think that the OSB actually is your vapor barrier: My guess is that the vapor barrier is right behind the OSB). So maybe you need to talk to a local building contractor, and he can tell you how to move your barrier while still complying with local building regulations ("code"). Or maybe you can ask Brien (xSpace) how to do that, since he understands vapor barriers and building techniques much better than I do. If you can do that (move the vapor barrier to the new wall), then is solves a lot of issues for you, and simplifies your build greatly. It also makes it much cheaper... - Stuart -

Thank you Stuart very much for offering such a strong and patient help. I don't know how I can advance otherwise. :o you might even convince me to take all off :lol: I just need a few days to sleep over this idea. It's not what I was prepared to do. I think I understand the problem. Even if we put the rock-wool inside the cavities we still have a coupled 2 leaf wall, right? What I don't understand is where do you see the 3rd leaf? My idea was to keep the wall with monitors open, covered with fabric only. In this case we would have a 2 leaf coupled wall, which is not the best solution I know, so what am I still missing here? Another question. Do we need to remove the inner leaf only at the area where the CR will be or also in the recording room? I would prefer to do it only in the CR. Less pain :wink: The only thing I will crank from time to time will be guitar cabinets. I think I can live with not having a super quiet recording room. Also the cost would go pretty hi if we do 2 room like this, right? Regarding the vapor barrier. My house is built in such a way that the OSB boards make the vapor barrier. Check this photo. You will notice green air stop tape which makes the OSB boards a vapor barrier through out the house.

I just talked to my constructor (good friend) and he said it's possible to take off all OSB boards from the outside walls. I am getting very inspired now to actually do it :P So we do this only in the CR or is necessary to do it also in the RR? We could even save most of the OSB boards. They can be used again on the new decoupled wall with air stop tape to create the vapor barrier. Is this what you had in mind? Stuart, what about the ceiling? Can we leave it like this and just build underneath what ever is needed? Please don't tell me I should take off the OSB boards from the ceiling, too. :lol:

I think someone asked what those tubes in the floor are for. They are there to run the cables from rear rack cabinet to the front patch bay section. I put a few also to connect the recording room to the control room.

Purusha, Before you get together a demo crew, some things to think about. The very first one this. You need to do some sound testing in this room. This is a heavy room! I think that some of the properties of the walls and ceiling are being missed in the examination. Particularly the OSB. With your stucco and that dense material it is installed to (which is the actual vapor barrier) and almost 8 inches of framing and rockwool, more OSB (with the absence of an interior barrier allows the wall to dry towards the inside of the room) and sheetrock, this surely must be a very quiet room for sure! The ceiling may come into question but even that, as a sound barrier, is pretty thick and most likely will stop a significant amount of sound. The brick wall with framing and sheetrock, there again, good wall design with the ability to produce a satisfactory TL / STC. Your country has a high humidity year round from what I have read, so this is in part the reason for this type of wall design. Essentially what gets wet on the outside, stays to the outside and what does pass thru the wall is allowed to enter the interior envelop to be extracted by heat and air system. But I would really look into doing some sound tests in there...with your family in the house doing whatever they do , day to day living. These are things that can alert you to just how well that house is designed and if there is a deficiency, the information to be better equipped to approach it accurately. Great thread, Brien

Thanks Brien. OK, I'll put my main monitors in the studio room, crank them and check how much sound penetrates the outside walls and above to the living room and so on? I can do that on Monday. I will try the same thing with my electric guitar. So you are suggesting that "maybe" there is no need to take down those OSB boards from the outside walls?

I am saying you have a very good starting place with the existing structure but need accurate sound level testing to help in this build. I would also suggest renting or purchasing a sound pressure level meter to get accurate levels from both sides of the walls. The human ear and time of day can fool us in to hearing what we want to hear and believing things that may or may not be true. Get some testing equipment, hire someone to do it for you, but get some numbers you can read.

OK, let me ask around if I can find someone with such equipment. Are these measuring devices used in some particular industry environments or is it strictly used in pro audio business? There is also one thing to consider if I do these sound tests. I don't have doors yet on the entrance to the studio room from my hall. This will surely let some of the sound to escape up through the stairs into the upper floor and possibly also to the outside through the main entrance which is near my studio entrance. If this device doesn't cost much I can also buy it. Can you give me a link to what we are looking for?

Wow...no door. That will be an issue, You need some type of sound barrier in the door frame opening to have this work in your favor. A sound pressure level meter. That is what you would look for just to get a sample of the sound levels in various places. Most here in the USofA would suggest going to Radio Shack to get one. In your part of the world, you have to use whatever is comparable to an electronics store there. The actual equipment to do very detailed testing can be expensive, at least for a good mic, and is also another learning curve to consider. You will have to talk to people that are either involved in acoustic measuring in your country, ask around.

All clear now. Will arrange for measuring and report back ASAP. Thanks!

Just to be sure. Would this toy (from 50---126 DB) serve the purpose? EBAY LINK This one looks better but also at higher price (from 30-130db) EBAY LINK

Smart advice from xSpace! Very solid. That cheap meter MIGHT work, but I'm skeptical: A half-decent meter costs around US$50-100 (new), a decent one costs maybe US$ 100-300, and a professional one with all the bells and whistles can cost many times that. So something for under ten bucks raises some questions in my mind! You are right to call it a toy! There are hundreds listed on e-bay right now: http://shop.ebay.com/?_from=R40&_trksid ... evel+meter I own 2 right now. One is a cheap one, something like this (but not that exact model) http://cgi.ebay.com/SL-824-Digital-Soun ... 3efe28b15a And the other one is a Phonic PAA3 bit fancier, more of an audio analyzer, than a simple meter: http://cgi.ebay.com/NEW-Phonic-PAA3-Han ... 45f13c51f3 You probably don't need the PAA3 (but it will tell you a lot more about your room than the simple one!), but you do need something reasonable. the good old Radio Shack meter that Brien mentioned is just fine for most people: http://cgi.ebay.com/RADIO-SHACK-SOUND-L ... 4cee602b9e You can pick up those (used) for around US$20-50. But you do need something to test with! - Stuart -

I would prefer to go with something cheap if possible. Call me a miser if you want :oops: Stuart, so the 30-130db (cheaper one), like yours would be good enough?

Yep, that should be plenty good enough for what you need. Let us know once you have it, so we can give you some pointers on how to set it up for taking measurements. - Stuart -

Great! Will buy it from the evilbay now.

Waiting for the sound level device to arrive... mean while I can ask a few questions. I am really interested to understand why some people when soffit mount go with soft front wall (fully stuffed with rock wool, covered with fabric only), and some use hard wall (gypsum, wood) layer around the monitors? Is there any specific reason why should one go or not go with one or the other option, or both work just fine? Personally I prefer the first option. My speculation is that one will get less standing waves coming from the nearfield monitors mounted on the stands. Second speculation is, if monitors planned to be soffit mounted are not really designed or tested for this kind of installation, there will be no bass boost effect or big change in the response curve. Please enlighten me. :idea:

I am really interested to understand why some people when soffit mount go with soft front wall (fully stuffed with rock wool, covered with fabric only), and some use hard wall (gypsum, wood) layer around the monitors? Is there any specific reason why should one go or not go with one or the other option, or both work just fine?

Are you talking about the soffit panels themselves (the panels that surround the speakers, and are angled at about 30 degrees across the corner of the room), or are you talking about the panel in the middle at the front, between the two soffits? If you are talking about the actual soffit panels, then they MUST be large, flat, solid, hard and dense. A soffit panel that only has wool covered with fabric is useless. The entire purpose of soffit mounting ("flush mounting") is to increase the apparent size of the front baffle on the speaker, to try to make it act like an infinite baffle, which in acoustic terms just means a panel whose dimensions are very large with respect to the longest wavelengths emitted by the speaker. Of course, to create a true infinite baffle you'd need to make them at least 17 meters wide ( :shock: ), since that is the wavelength of the theoretical lowest note that humans can hear, but you can still get a very decent effect with soffits just a meter or two wide. I wish I could find it again, but I recall reading somewhere that the soffit panel works well when it is a quarter wavelength of the lowest frequency, so a soffit that is 2 meters wide will work fine down to about 40 Hz, and even at just 1 meter wide will still work down to about 80 Hz. But in order to be an "infinite baffle", the panel MUST be just as solid and dense as the front panel of the speaker itself. So surrounding the speaker with rock wool just will not work. It has practically no effect at all as an infinite baffle (except for very, very low frequencies). Make your soffit panels as large and as dense as you can get them. The also need to be exactly flush and perfectly lined up with the speaker. So if you ave to angle or tilt the speaker to aim it correctly, then you also have to angle and tilt the entire soffit panel. Just remember that the soffit panel is supposed to be an extension of the speaker box front panel. Use heavy, dense materials for your soffit panel, such as thick HDF, MDF or plywood. I am going to use concrete for mine. Now, if you are talking about the panel

between

the soffits at the front of the room, then that can be either solid or soft, depending on what you need for your room. Personally, I prefer to make that soft, such as a thick layer of rock wool for example, in order to help reduce flutter echo and first order reflections, plus also provide absorption at the front of the room, since there isn't really anywhere else to do that in a small room. But that's just me: others prefer to keep that part solid as well, just like for the soffit panel itself. But you do still need to stuff the entire area behind the soffit panels with wool: it is just like the inside of a speaker, basically: You need to damp the cavity to control resonance. However, if you are going to use active speakers, then you also need to cut a vent path through the rock wool, and put vents in the top and bottom of the soffit panel, so that there is plenty of cooling air flow past the back of the speaker. If not, then it will overheat and suffer damage. - Stuart -