Preliminary Mixing room Design Stockholm- Sweden

Hello Everyone! I have been snooping around this incredible site and have been extremely impressed with the large amount of information that is accessible. I am in the preliminary stages of designing a mixing room that is going to be used for mixing down music. As far as the loudness it is not an issue in this case since I will be mixing in low volume. The studio will be located in Stockholm Sweden inside a private residence. My primary concern is that the room is as “true” as possible, in other words, that the mixes translate well in different listening environments. The design I have provided is a preliminary sketch and does not contain bass traps at the corners at the end of the room facing the studio monitors. The right hand of the room is connected to my neighbors. The front part faces the outside while the back and the left side of the room are connected to the rest of the residence. The roof is concrete (painted white) and the untreated walls are regular drywall. My intention is to use 2 inch 48 kg per cubic meter isolation inside the wood frames with the isolation facing the studio. The wood frame is made out of 145 mm by 45mm “2 by 4’s”. The isolation will be covered with cloth. There are two leafs (I hope I got the terminology right) since there are two separate walls which are separated by air in the front-end corners of the room. I also plan to use a ceiling cloud right on top of the mixing position. Questions; 1) I wonder if drywall is a good choice for the inside part of the wood frame that supports the isolation? If No, what materials are preferred and why? If yes, should I use different thicknesses on the connecting walls that contain the air pockets? (This question relates to the air spring in the front corners of the two leafs). 2) Should the bare walls be treated with additional acoustic panels without making the room too “dead”? I would also be very happy to hear any suggestions on how to best place the bass traps at the back of the room. Any input on how this design can be improved would be appreciated. Sincerely yours, Useg Diaz-Granados (Since I don’t know if you can see the dimensions of the room in the sketch I decided to include them. Height 2.45 M, Wide 2.7 M, Length 5 M.)

Useg, My friend, that will not work. Acoustic isolation is only as good as it's weakest link. It looks real cool, but you have just lost a lot of space in that room and have done nothing for your isolation. or for your acoustics for that matter. :wink: At Height 2.45 M, Wide 2.7 M, Length 5 M, you already have a small room. Are your neighbors complaining? How much isolation do you really need? STC what? or OITC what? Well, how much loss you want the partition to have in decibels? If your walls are concrete you may already have a TL of around 42 - 55db. Flanking paths are probably the main concern and can be very tricky to remedy. I would need more information about your structure and location to advise. Cheers, John

Thank you for your reply and observations. After some searching on the web since I believe that OITC would be the more relevant although I am not sure. I base this on the fact that the site I visited claimed to measure frequency ranging from 80 to 4000 hertz where as STC affects the 125 to 4000 hertz range. A lot of the music I will be mixing will be bass heavy (40 and below). My main objective is to make the room as “accurate” as possible (Flat frequency response across the spectrum). Although I respect your experience in this field I do not see how a total 4 inches of isolation Rockwool (30 kg cubic meter/density) would have no impact on the isolation or the sound in the room. Could you be kind and clarify in greater detail what you mean. I read somewhere in this forum that adding a layer of plastic on top of the Rockwool would improve the sound in a room since the plastic would reflect back some of the high frequencies instead of over-absorbing them. Do you believe this to be accurate ? If No, could you explain why? As far as the material in the room are concerned, all of the walls are drywall except the front of the room and the roof which are made out of concrete. The floor is made out of laminated wood. I was under the impression that the double isolation (partitions) would improve the sound characteristics of the room by limiting the reflection back into the mixing position. Since I do not have your great experience and knowledge I do not understand how the DB loss would impact the accuracy of the room. I will re-design the room (60 degree angle for the main monitor position etc.) and will include the bass-trap design for the back of the room (and post it when I am done). I look forward to your observations and any further suggestions on how to make the design work. Sincerely, Useg Diaz-Granados

Although I respect your experience in this field I do not see how a total 4 inches of isolation Rockwool (30 kg cubic meter/density) would have no impact on the isolation or the sound in the room.

Because contrary to popular belief (and contrary to myth-based "acoustic" web sites) insulation does not stop sound. Insulation and isolation are two entirely different things. Isolation (preventing sound from getting from "A" to "B") can only be accomplished in two ways: 1) Remove the medium through which sound travels between them, (ie create a total total vacuum between the points, by removing all the air and everything else between "A" and "B"), and 2) Place enough air-tight mass in the path between "A" and "B" that the sound energy is totally dissipated before it can get through. 4 inches of insulation does not accomplish either of these. Not even 4 FEET of insulation will do the job. (Maybe something like 40 feet would help.) Insulation is good for room TREATMENT, but does practically nothing for room ISOLATION. To isolate, you have to create a physical barrier that prevents sound waves from getting through, which implies a total air-tight seal, and lots of mass (since it is impractical to put a vacuum around your room, all you have left is mass), and decoupling. Insulation serves to attenuate sound energy, but does not eliminate it. One way you can think of sound waves is as a constant complex interchange of energy between velocity and pressure. Insulation works on the velocity portion of sound waves, but does nothing at all to the pressure portion. Mass works on both. So your 4 inches of insulation would indeed help to treat the room, changing the internal acoustics, but will do practically nothing to isolate the room. And even then, having so much insulation on such a large wall area might not produce the acoustics you want...

The isolation will be covered with cloth. There are two leafs (I hope I got the terminology right) since there are two separate walls which are separated by air in the front-end corners of the room.

I'm not sure I understand you: Are you considering that the cloth is one "leaf", and the drywall is the other "leaf"? Is that what you are saying?

1) I wonder if drywall is a good choice for the inside part of the wood frame that supports the isolation? If No, what materials are preferred and why? If yes, should I use different thicknesses on the connecting walls that contain the air pockets? (This question relates to the air spring in the front corners of the two leafs).

Maybe you could draw a diagram to show where you plan to install that drywall, and what you mean with the term "air pockets".

I would also be very happy to hear any suggestions on how to best place the bass traps at the back of the room.

Bass traps work best in corners, due to the boost that you get from the surrounding surfaces: 12 dB for the corners where two surfaces meet, 18 dB for corners where three surfaces meet ("tri-corners"). Bass traps need to be large and deep in order to work well.

Any input on how this design can be improved would be appreciated.

I think I'd go for a more traditional, proven design, such as using proper MSM walls for isolation, and the currently popular RFZ concept (Reflection Free Zone) for basic layout. Since you have the space, I reckon I'd also go with soffit-mounted (flush-mounted) speakers. I'd also check that the room is based on one of the known-good ratios, and that the layout (speaker location, mix position, geometry) follow the usual guidelines for such rooms. - Stuart -

Thank you for taking out the time clarifying these terms and outlining how they function. My main objective is to treat the room. I am not considering the cloth or the Rockwool a leaf, only the “hard surfaces” (drywall etc.) that the sound has to penetrate through or reflect from. I have made a new sketch trying to explain what I assume to be a leaf and an air-pocket and included a design for the bass-traps. I know the bass-traps are not that deep because of the door being to close to one of the corners. Do anyone have any suggestions on how to deal with this problem and the untreated area? I thank you for the recommendation regarding the soffit-mounted monitors and wonder if this is when the monitors are “baked into” the wall? Sincerely, Useg Diaz-Granados

I still don't understand what you are trying to accomplish with that. It makes no sense either as treatment or as isolation. It will not treat the room since there is a massive barrier (the drywall) between the "air pocket" and the room. And it will not isolate the room because you are only building it in one small section of the room. I don't see the point.

As far as the loudness it is not an issue in this case since I will be mixing in low volume.

Are you sure that is good enough? What do you mean by "low volume"? What actual physical sound level, in terms of decibels, do you mean when you say "low volume"? And how quite does that have to be n the other side of the walls? Also, you dn0t seem to ave considered sound coming the OTHER way through the wall: What about loud sounds outside the room that could disturb your record/mixing sessions?

The right hand of the room is connected to my neighbors.

And they don't make any noise at all that could mess up your mixes? And you won't make any noise at all that could disturb them? What type of music do you mix? If you plan to mix rock, pop, or anything else that involves rums, bass guitars, and electric guitars, then it's hard to see how you could mix at a high enough level to do a decent mix while also mixing at a low enough level to not disturb your neighbors. 85 dB is the usual level for mixing. Any lower than that and you won't be able to clearly hear the subtleties. How loud is your noise on the other side of the wall when you are playing rock music at 85 dB in that room right now? Did you even measure any of this with a sound level meter? If not then you really need to do that BEFORE you start designing the room.

the untreated walls are regular drywall.

In that case my guess is that your mix at 85 dB on your side of the wall is going to be somewhere around 55 db on the other side of that wall. 55 db is annoyingly loud to most people, especially if they are trying to sleep or relax!

There are two leafs (I hope I got the terminology right) since there are two separate walls which are separated by air in the front-end corners of the room.

So what is the point of doing that on only part of the room, and especially if you say that you don't actually need any isolation at all?

My main objective is to treat the room.

Well, if you only want to treat it, then why are you planning an MSM isolation wall at the front? That wont treat anything. And it wont isolate either, since it does not cover 100% of the room.

a design for the bass-traps

As you say, those are way too small. I understand the issue with the door on the right, but why can't you make the one on the left bigger? You could also make a "bass trap on wheels" that you can roll in front of the door while mixing.

...regarding the soffit-mounted monitors and wonder if this is when the monitors are “baked into” the wall?

I've never heard the term "baked into the wall" before for soffit mounting, but it sounds like you have the basic idea. I'd strongly suggest that you spend more time reading trough this forum, looking at the designs here, looking at the build threads of people who have completed their studios already, and researching the basic principles of acoustics, but it seems you have a lot of doubts and confusion still that you really should clear up before you start designing your studio. - Stuart -

This is a response to Stewart’s last post; 1) The accuracy of the room is my main priority. Naturally I have considered how this could potentially be “annoyingly loud to most people, especially if they are trying to sleep or relax!” This is and should remain a personal choice and has been taken after considering all of the relevant factors (including cost) that affect the project. If there is a cost effective way of treating and isolating the room I am all ears. 2) No, the noise the neighbors (or the outside) cause is not a factor in this case. You have assumed that I have not considered the noise “coming the OTHER way through the wall” I have. I humbly thank you for reminding me once again of this particular issue. Personally I find the tone of your responses a little bit sharp at times. I do not see how that constructively helps the communication in between us. I appreciate the expertise of the people who have tried to shine light into the questions I have asked. As a matter of fact I have spent a considerable time reading the posts in this forum although I obviously do not have a grip (at this time-period) of some of the fundamentals of sound treatment and Isolation. After reading some other posts I think that others also are having difficulty absorbing all of the knowledge that this wonderful forum has to offer. 3) Let me ask you this Stuart…… If I replaced the drywall with another material that the sound can travel through. Would that improve the frequency response within the room? If yes/no: Why? There is a spin-off of the Rockwool franchise that specializes in acoustic absorbers. http://www.rockfon.se/Startsidan Since this site is in Swedish I assume that you might have as great of a difficulty in understanding the text as I have understanding some of the terms concerning absorption and acoustic treatment. Could you be so kind as to look at the absorption charts and tell me if it could help me achieve my objective? http://produkter.rockfon.se/?alttemplate=product_config#7848:7900:7749: http://produkter.rockfon.se/?alttemplate=product_config#3881:6135:5275: 4) Thank you for giving me suggestions on how I can solve the door/bass trap issue(s). After reading an article that Ethan Winer published I wonder if a Hemholtz Resonator might be the answer for the untreated area of the room? If yes,can it be used as an effective remedy for absorbing frequencies under 40 hz? Once again, I thank you for responding and hope you have greater patience with the ones of us who might not be as knowledgeable in this area as you are…… Sincerely, Useg Diaz-Granados

Useg, Stewart doesn't mean to be 'sharp' he really is just trying to help. I do agree with his observations and comments. --- And please don't feel bad about not having a grip on this subject, I have spent the best part of 40 years doing this and I learn something new all the time. :wink: Please have a look at the pdf's that I posted here. One titled ISOLATION is just that. The next is an example of 'ACOUSTIC TREATMENT'. You can turn 'layers' on and off in the pdf to view better details... In your case, as you have said several times, isolation may not be a problem (though I seriously doubt it) and you should focus only on room treatment. BUT! you also said that the music that you mix is bass heavy and OITC applies. Then have a look at the ISOLATION pdf. The drawing shows an example of STC67 to STC70 isolation design - and STC77+ with green glue in both walls. The insulation fill in the wall cavity is simply fluffy pink stuff - or maybe yellow stuff in your part of the world. Just get the cheapest stuff for wall cavities because the more expensive insulation is just that.. more expensive and you don't get more benefits. :wink: Your ISOLATION is only as good as your weakest link and if you have a wall that is isolated half-way... you might as well NOT have a wall at all. And don't forget the flanking paths through your floor and rigid connections. You have to isolate the ceiling as well, adding clips or channel to the ceiling and a couple layers of gypsum board... There's a lot to it. I have just scratched the surface here. I hope this is helpful and that you can get some ideas from the pdfs. Cheers, John

Thank you for your response, information and recommendations. John, trying to get a grip on how to tackle the problems you and Stuart mentioned I wonder if this wall-design would work better? (It is only for the inner walls) Sincerely, Useg Diaz-Granados

Useg, No, it won't. Sorry. Have a look again at the ISOLATION pdf. You will see that the new inside wall goes all the way around. You must isolate all the surfaces including the ceiling.. and possibly the floor as well because it will be a flanking path for sound. Cheers, John

You will see that the new inside wall goes all the way around. You must isolate all the surfaces including the ceiling..

Exactly. That's part of what I was trying to say. Think of it this way: If you only put half a piece of glass in the front of an aquarium, it will not hold water. Even if you put glass around three sides, on the floor, and on the roof but leave out the glass in just one side, it still will not hold water. You have to put glass all around the entire aquarium, on all sides, for it to hold water. The same happens with sound: Like john said, in order to isolate, you have to treat all six sides of the room, or at least the most important five of them: the four walls and the ceiling (assuming you you happen to have a massive and well damped floor, such as a thick concrete slab on grade). Isolation is an "all or nothing" proposition. Either do the entire room, or don't do it all. Just doing part of it will not help. - Stuart -

Thank you for the help :D Sincerely, Useg Diaz-Granados

Soundman2020 wrote:

Think of it this way: If you only put half a piece of glass in the front of an aquarium, it will not hold water. Even if you put glass around three sides, on the floor, and on the roof but leave out the glass in just one side, it still will not hold water. You have to put glass all around the entire aquarium, on all sides, for it to hold water. ....Isolation is an "all or nothing" proposition. Either do the entire room, or don't do it all. Just doing part of it will not help. - Stuart -

Excellent analogy Stuart! Thank you. --- I'll have to remember that one. Cheers! John

Excellent analogy Stuart! Thank you. --- I'll have to remember that one.

:) Sure! I didn't patent it! :) (In fact, I can't even claim it as mine: I seem to remember reading it somewhere else...) - Stuart -

Thank you for guiding me in the right direction! :wink: I will isolate the room before treating it. I have made some sketches (isolation only) based on the pdf that John sent over. Could you be so kind as to let me know if I got it right? The insulation should be in between the studs like it is on the pdf. What about the resilient-channel John? They are not included in your pdf files…… Are they irrelevant in these case(s)? I also have a question concerning the roof. On the pdf this problem is resolved by using ceiling cloud traps. Is that sufficient when isolating? I realize that this is a design forum and not a construction forum but as I’ve learned here the two go together. It’s been hard for me to dig in and find the information I need in order to accomplish my objective so I have compiled I list of links that might be useful. This is a totally new realm for me. For that reason I cannot guarantee the accuracy of the information. If the information happens to be inaccurate please let me know. http://www.johnlsayers.com/phpBB2/viewtopic.php?f=2&t=328 http://www.johnlsayers.com/phpBB2/viewtopic.php?f=2&t=17 http://www.greengluecompany.com/ http://www.youtube.com/watch?v=cAROdRNSavI http://www.youtube.com/watch?v=lj82eXwSAhs&feature=channel http://www.johnlsayers.com/phpBB2/viewtopic.php?f=3&t=13875 http://www.youtube.com/watch?v=Bf5syq09qa0&feature=related http://www.youtube.com/watch?v=s-gpqY89XYI&feature=related http://www.acoustiguard.com/ http://www.johnlsayers.com/phpBB2/viewtopic.php?f=3&t=363 http://www.tubetrap.com/articles/db1191.htm http://www.customaudiodesigns.co.uk/help.htm http://www.johnlsayers.com/phpBB2/viewtopic.php?f=3&t=1714 http://www.johnlsayers.com/phpBB2/viewtopic.php?f=2&t=573 http://www.johnlsayers.com/phpBB2/viewtopic.php?f=2&t=1231 http://www.johnlsayers.com/phpBB2/viewtopic.php?f=2&t=5715 I want to use my old updated design (even if I have to tweak it t get it right) for the treatment of the room (the one used when Stewart explained the water-tank analogy). I was thinking of having the inside wood-frame (look at the Studio JPEG) that is going to contain the sound treatment for the room as a fake wall, in other words it would not be screwed into the drywall.I was thinking of using 6,2 mm thick masonite boards to hold up the Rockwool flexibats. Since I want the sound to travel through “airpockets” I will drill holes through masonite board (no drywall stopping the sound). Does this make sense from a sound treatment perspective??? As far as the portable bass traps go I found a link that interest me. http://www.gearslutz.com/board/bass-traps-acoustic-panels-foam-etc/375094-my-diy-gobo.html Do you have any comments, suggestions or thoughts on how this might work with my design taking into consideration that frequencies around 40Hz and below are going to be a problem? There are some sound treatment questions that I asked you earlier that remain unanswered. The first one is …… ” After reading an article that Ethan Winer published I wonder if a Hemholtz Resonator might be the answer for the untreated area of the room?” …… And the second one is …… “I read somewhere in this forum that adding a layer of plastic on top of the Rockwool would improve the sound in a room since the plastic would reflect back some of the high frequencies instead of over-absorbing them. Do you believe this to be accurate ? If No, could you explain why? If you have time to guide me with regard to these questions it will make my day. :mrgreen: Sincerely, Useg Diaz-Granados