John Sayers' Recording Studio Design Forum Archive

Hey all!

It's already a few years since I started looking around on this forum and I finally got to the point that I can start the design and build of my own studio.
I already had a topic on a temporary room I needed the treat for mixing. http://www.johnlsayers.com/phpBB2/viewt ... =3&t=20238

So I finally finished the construction/renovation of my home and can start the design/construction of the studio. I'm currently still in the design stage and wanted to post my current design here so you could comment on it. I've added the sketchup design below.
Some remarks:

* The building has an odd shape and can't be modified. It's entirely built in hollow concrete blocks (14 cm thick). The roof is constructed out of horizontal concrete profiles with blocks in between and has a layer of about 6 cm concrete on top of that. The floor is still just dirt so this can be modified (concrete slabs can be put a little lower or higher depending on the needs)
* The drawing shows the original design on the left and my new design on the right. Note that my design is in no way perfect and is just a rough sketch of what to my opinion seems the best way the construct it.
* For structural reasons some walls or beams can't be changed. So the ones I left in the design need to stay in the design.
* In the file attached the right design contains two coloured rooms. The green one is the control room and the yelow one is the live room. In between there's a corridor with at the end of the corridor a small toilet. The doors or openings to the live and control room are just indicative and can be changed.
* The rest of the building needs to be used as a garage. My wife watches carefully over this

Questions:

* Do you think that the rooms, as currently designed, are workable? I'm especially worried about the control room because the ratio isn't that great. That's why I didn't place the two side walls parallel to hopefully break up the modes a bit. By the way, the rooms as shown are the actual rooms, no acoustic treatment added yet.
* The building resides in a residential area. I'm planning on recording there but also rehearsing with my band. We produce about 110 db of noise. The nearest neighbour is about 8 m away. I'm not sure about how low to go so not to hinder the neighbours but say I want a max of 50 dB just outside the buidling. That's a 60 dB noise reduction. To building is entirely out of concrete (don't know the exact mass though) and I'm planning to put the live room (we will be rehearsing here) on an isolated slab and construct that room out of 14 cm thick concrete blocks with a 10 cm air gap in between. Do you thinks this will be sufficiant? And also, can you point me to some more info on calculating the exact transmission loss through a wall?
* The control room I would put on the same concrete slab as the rest of the building and construct this out of wood skeleton and gyproc plates (2 or 3 layers). This is because the control room won't produce as much dB's as the live room and the sound proofing between the live room and control doesn't need to be as high as between the live room and the outside.

Hopefully I've added enough information.

Thanks in advance,

Thomas

Hi Thomas, and welcome back!

* The building has an odd shape and can't be modified. It's entirely built in hollow concrete blocks (14 cm thick). The roof is constructed out of horizontal concrete profiles with blocks in between and has a layer of about 6 cm concrete on top of that. The floor is still just dirt so this can be modified (concrete slabs can be put a little lower or higher depending on the needs)

Lucky you! That's a great starting point.

I'm especially worried about the control room because the ratio isn't that great.

Did you check the ratio with Bob Golds' or Andymel's calculator?

That's why I didn't place the two side walls parallel to hopefully break up the modes a bit.

That won't work. With such small angles, the modes will still be there, practically no difference. You'd need very much larger angles to have any useful. effect. You are just wasting space like that.

* Do you think that the rooms, as currently designed, are workable?

You are wasting a large amount of space by having that little closet thing and empty hall between the two rooms. That serves no useful purpose that I can see, and wastes space. If you need a closet similar to that for storage, then put it in the triangular section that you cut off, or in the other triangular corner at the rear of the LR. that would allow you to make the LR much bigger. And maybe the CR as well.

About that: You cut a rather large hole in the wall dividing the CR from the LR, so clearly that is not a structural wall, and not one of the walls that can't be changes. If you can safely cut such a large hole in it like that, then you could safely eliminate it completely, which would open up the entire area into one long-but-strangely-shaped space. I think there are many more options open to you if you do that. You can make much better use of that space, and get better shapes/sizes for both rooms.

but say I want a max of 50 dB just outside the buidling. That's a 60 dB noise reduction. ... I'm planning to put the live room (we will be rehearsing here) on an isolated slab and construct that room out of 14 cm thick concrete blocks with a 10 cm air gap in between. Do you thinks this will be sufficiant?

Probably yes. That should, indeed, get you about 60 dB of isolation, and perhaps even a bit more.

And also, can you point me to some more info on calculating the exact transmission loss through a wall?

Sure:

http://www.marshallday.com/media/1341/1 ... n_loss.pdf

For your purposes, equations 4, 5 and 6 on page 2 are plenty good enough. You wont have interconnections, so those are fine.

- Stuart -

Hey Stuart

Thanks for replying. I'm following you on your comments and did a new design. There's a picture of it below. I've now put the toilet/closet inside the live room. I've also adjusted the dimensions of the control room so the ratio is better. According to the amroc room mode calculator it now fits inside the Bolt-area and also fits the Bonnello-criteria.
The wall that I need to change for that is actually a structural wall but I was already planning on adjusting it. I'm now gonna put a steel beam in place to handle the weight of the roof. I just need to do the calculations
So, better?

Thanks,

Thomas

PS: concerning the equations in the file you pointed me to (thank you btw). The f0 they speak of (mass-air-mass resonance frequency), how can it be calculated? I also need to use equation (2) to calculate R1 en R2. I think in this equation w = omega = 2*pi*f and c = speed of sound through air. But what is the 'eta' in the equation?

That's an improvement, but I wouldn't put a bathroom inside the LR. I thought that was just a storage room, not a bathroom. It's not a good idea to have a bathroom opening directly into the live room (or into the control room) for many reasons (isolation, noise, smells, humidity, water, etc.), so I wouldn't do that.

The other option would be to put that in the "other" angled part, here:
It seems to me there's space to put a bathroom in there, but still keep it outside of the studio.

I've also adjusted the dimensions of the control room so the ratio is better. According to the amroc room mode calculator it now fits inside the Bolt-area and also fits the Bonnello-criteria.

Looks much better.

The wall that I need to change for that is actually a structural wall but I was already planning on adjusting it. I'm now gonna put a steel beam in place to handle the weight of the roof. I just need to do the calculations

Better hire a qualified structural engineer for that! There's a procedure you'll need to follow very carefully to support the ceiling above you while you take out the wall and put in the beam. That's a dangerous job, and you should hire someone who is qualified and certified to do that.

The f0 they speak of (mass-air-mass resonance frequency), how can it be calculated?

Oops! sorry, I didn't realize that the basic equation was not in that paper. Here it is:
By making some simple assumptions about common conditions, that equation can be simplified to:

F0=c[(m1+m2)/(m1*m2*d)]^.5

where:

F0=resonant frequency (Hz)
c=constant (60 for empty gaps, or 43 if filled with insulation)
m1=mass of first leaf (kg/m^2)
m2 mass of second leaf (kg/m^2)
d=depth of gap between leaves (m)

For imperial units the constants are 170 for empty cavity and 120 for cavity filled with suitable insulation.

I also need to use equation (2) to calculate R1 en R2.

No you don't... You need equation (1) to do that (mass law). The small corrections in equation 2 aren't really relevant, unless you want extreme precision or have a rather unusual wall. In most studio walls, coincidence occurs at a high enough frequency that it isn't a problem. Standard mass law is close enough for what you need.


- Stuart -

Hey, I've adjusted my design considering your suggestions. You're probably right about not putting a toilet inside the live room . It's a difficult corner to do something with. The only two options I see now is eighter put some kind of iso-booth in there or just use it as a bass trap. What do you think?
About the structural thing. I've already done a lot of structural changes like this so I'm confident it won't be a problem. But just to be sure I'll call someone to come and check it out.

They already delivered the concrete bricks and bags of cement I need for the changes in the outer shell. I'm planning on starting work on this next week.

Concerning the transmission loss. According to my calculations my f0 (for the live room) is 13.75 Hz. So that seems solid. I'm getting (in theory) 51.21 dB of transmission loss @ 50 Hz. At 70 Hz I'm at 60 dB so hopefully that'll do.
I was also planning on constructing the inner shell of the control room in wood skeleton and gypsum plates. I read somewhere in this forum that this would be better to control the low frequenties in the CR. Is this correct? LR I'll do in concrete bricks (265 kg/m²) to get the transmission loss I need.

Thanks, Thomas

Hey

I've also been doing some calculations on some of the other elements like windows, doors and roof of inner leaf and I've come up with some other questions.

My wall construction seems adequate when it comes to sound proofing. m1 = 155 kg/m² and m2 = 265 kg/m², d = 0.1 m. This gets me a reduction of 51.21 dB @ 50 Hz. The problem is when I get to the roof, door and window. Rob Gervais tells us that we simply need to maintain our mass through the entire leaf to hold up our amount of isolation. My outer leaf already has a solid concrete-like construction and I'm confident that the roof and walls will never be less then 155 kg/m². This means I need doors in my outer leaf of 248 kg (0.8 m x 2 m x 155 kg/m²) . Now this I actually see achievable. I work at a company that makes large press brakes and I could have a steel plate of 20 mm cut to the dimensions of a door, ad some L-profiles to it and make me a 248 kg door...
My problem is the inner leaf. For the wall construction I could use solid concrete blocks that give me 265 kg/m². However, because the outer leaf is already constructed there's no way for me to give this a 265 kg/m² roof. This would be possible if I built the inner room first (in concrete) and then the outer leaf. But that's not the case. Some quick calculations given for a roof with 3 layers of gypsum board (12.7 kg/m² per plate) and beams with a section of 180x60mm spaced 300 mm apart gets me 54.3 kg/m². Seems to me that there's no use in making the walls 265 kg/m² if the roof is only 54.3 kg/m². Also the thickest glass I can get for the window is 20.68 mm thick. Which results in 60.95 kg/m².
So now I'm thinking of making the entire inner shell out of 3 (or maybe 4) layers of gypsum board but spaced 0.2 m from the outer shell instead of 0.1 m in the previous case. This could result in 43.46 dB isolation @ 50 Hz (61.52 @ 100 Hz).

All other possibilities or suggestions are welcome

Thanks, Thomas

I think you are overthinking this a bit, Thomas!

Yes, you probably could build a room to get you 50 dB of isolation at 50 Hz, but my question would be: why you'd want to do that? If you are getting 50 dB at 50 Hz, your overall isolation is probably way up around 80 dB or maybe even more, and I really can't think of a good reason why you'd need that much, unless you want to be the next Galaxy Studios! (They get 100 dB of isolation.... but it cost them millions of dollars to do it...) They are located just up the road from you, actually... also in Belgium.

The vast majority of studios, even very well isolated ones, will only be getting around 20-something dB of isolation at 50Hz, perhaps approaching 30 dB in the best of cases. Unless you plan to record live canon fire, the engines of huge ocean liners, or the roar of a full-size waterfall in your place, I can't see why you'd need such high isolation. What instruments are you wanting to put in there that you need to isolate so greatly at such low frequencies?

I could have a steel plate of 20 mm cut to the dimensions of a door, ad some L-profiles to it and make me a 248 kg door...

And you'd need some pretty hefty framing to hold it up without warping, twisting, leaning, or sagging! Plus some rather heavy duty hinges, and a really tough door closer: it would be very unsafe to try to close that by hand...

Once again, that's probably overkill for the average home studio. There might be a need for such a door on a sound stage or mastering room for blockbuster movies with colliding planets and earthquakes, but not for a typical project studio. A door of about one third that weight would probably be plenty.

Some quick calculations given for a roof with 3 layers of gypsum board (12.7 kg/m² per plate) and beams with a section of 180x60mm spaced 300 mm apart gets me 54.3 kg/m².

I'm not so sure I'd like to be sitting under a roof that heavy on such small joists... But yes, that would be a good mass to shoot for on an inner leaf where you need high isolation at low frequencies. And by the way, 3 x 12.7 = 38.1, not 54.3... Your isolation is only as good as the weakest point, which would be where you have nothing but three layers of drywall...

Seems to me that there's no use in making the walls 265 kg/m² if the roof is only 54.3 kg/m².

... unless you have a larger gap in the ceiling cavity, and a smaller gap in the wall cavity, to compensate...

Also the thickest glass I can get for the window is 20.68 mm thick.

That's more than plenty, if you design the windows well... I normally use something like 6+10 for one side and 8+10 on the other.

So now I'm thinking of making the entire inner shell out of 3 (or maybe 4) layers of gypsum board but spaced 0.2 m from the outer shell instead of 0.1 m in the previous case. This could result in 43.46 dB isolation @ 50 Hz (61.52 @ 100 Hz).

Once again, that would work, but the question is: "Why so much?"


- Stuart -

Ok some questions:

1 - If we're talking about sound transmission loss and for example we want a loss of 60 dB. At frequency are talking about then?

2 - This is something I was wondering about. When I started my calculations I did the one for my wall construction. So this was 51.21 dB @ 50 Hz (we're just talking about numbers here not about the physical necessity of it). I then reverse calculated the air space I would need if I could get doors of 100 kg/m² and the number I came up with was 0.41 m. I then drew the sketch below.
However I then started doubting this because there will probably be some flanking problems in the transition from concrete to steel and back. I've seen enough physics during my education to know that the answer wouldn't be that simple. However then you said this:

... unless you have a larger gap in the ceiling cavity, and a smaller gap in the wall cavity, to compensate...

Are you sure that this is correct? Btw, I'm not asking you this in a disrespectful 'doubting you' kind of way but just because I want to know and understand.

3 - The reason I had 54.3 kg/m² is because I added the weight of the structural beams to that part of the inner leaf. Is that not correct? Wel maybe not, but you could say that you have to do the calculations for the part where there's only 3 layers of gypsum with big air gap and superimpose on that the part where there's the 3 layers of gypsum + the structural beam and smaller air gap. And if that's not correct then isn't there something wrong with our reasoning in question 2?

So, probably still over thinking it... But I just want to understand. I started reading the work of B. H. Sharp "Prediction methods for the sound transmission of building elements" but couldn't find anything on the actual cumulated transmission loss of non-homogenous structures (such as a two leaf wall with a door or window in it).
If you think this is taking us to far then don't feel obliged to answer. No problem.

However, the second drawing I added before has the toilet out of the LR. Seems the best way like that. What would you do with that sharp upper right corner? Bass trap or some kind of booth inside the LR?

Thank you very much for answering my questions by the way? It's been extremely helpfull.

Thomas

1 - If we're talking about sound transmission loss and for example we want a loss of 60 dB. At frequency are talking about then?

At all frequencies, in general, overall! In other words, in a hypothetical building such as the one you describe that provides 60 dB of isolation, if you set up a full-range speaker system inside and played loud rock music at a level that measured 120 dBC on a hand-held sound level meter inside the room, then you went outside and shut the doors, the sound level meter would show you a level of 60 dBC outside. That would be 60 dB of isolation, which is the difference between 120 dBC inside and 60 dBC outside. If the meter was actually reading 80 dBC, then you'd know that you only have 40 dB of isolation, not 60.

However I then started doubting this because there will probably be some flanking problems in the transition from concrete to steel and back.

Right. That's why we say that the practical limit for isolation in typical home construction is about 70 dB, absolute maximum: you can't go more than that, realistically, because that's the flanking limit for typical slab-on-grade floors, best case. In reality, the limit is more like 60 dB in most cases. If you want more than that, you have to start thinking about isolated foundations, floated floors, very high density (high mass) building materials, which is out of reach for the typical DIY home studio builder. The cost goes way up, and it gets to be beyond the abilities of the average DIY builder. 40 dB is simple, 50 dB is harder but do-able, 60 dB is really hard (and really expensive), and 70 dB is pretty much the limit, even for large budgets and skilled work. Flanking won't let you go beyond that. And I'm not sure that you'd need to, anyway!

3 - The reason I had 54.3 kg/m² is because I added the weight of the structural beams to that part of the inner leaf. Is that not correct? Wel maybe not, but you could say that you have to do the calculations for the part where there's only 3 layers of gypsum with big air gap and superimpose on that the part where there's the 3 layers of gypsum + the structural beam and smaller air gap. And if that's not correct then isn't there something wrong with our reasoning in question 2?

Any isolation system is only as good as the weakest part. For example, if your walls, floor, and ceiling are built to 60 dB but your doors are only built to 50 dB, then your total isolation is around 50 dB, certainly not 60. The same applies to parts of the walls: while you might have 55 kg/m2 where the joists are, you only have +/- 33 kg/m2 where there is only drywall, so that's the weakest part. You use the lowest numbers for calculating isolation. You still need to know the full weight for your structural calculations, but only use the weakest part for the isolation calculations.

I started reading the work of B. H. Sharp "Prediction methods for the sound transmission of building elements" but couldn't find anything on the actual cumulated transmission loss of non-homogenous structures (such as a two leaf wall with a door or window in it).
If you think this is taking us to far then don't feel obliged to answer. No problem.

He came to the same basic conclusion: the weakest part of the isolation system sets the limit. the simplest demonstration of this principle is this: open the door! You can have the best isolated studio on the planet, and you hear nothing at all standing outside the door when it is closed, but as soon as you open it, you hear everything. The "weakest part" in this case is the empty hole where the door was, before you opened it. even though the rest of the room is isolated to amazing standards, having the door open means that there is no isolation at all....

The weakest part always wins.

However, the second drawing I added before has the toilet out of the LR. Seems the best way like that. What would you do with that sharp upper right corner? Bass trap or some kind of booth inside the LR?

Maybe a mic closet, or something like that. It's a very strange shape, and not very useful for storage. It could also be a bass trap. Or it could be both! I once designed a small studio with a storage room, such that opening the door to the storage room changed the acoustics of the rest of the room...

Thank you very much for answering my questions by the way? It's been extremely helpfull.

- Stuart -

Hey guys

I just wanted to post back here because I still haven't started building the studio yet. I'm currently still working on the outside aesthetics of the building and garden so the wife is content ...
I stuck with the main design I made a few months back but now I'm wondering about something. I've posted a design below which makes it almost possible to work in the studio as if it were one big room. I see some advantages in this design:
- A bigger room for tracking. Less reflection.
- More direct contact with what you're tracking. It will probably be mostly my own band or just myself.
- For mixing it would put my back wall about 7 m farther then it would be in a seperate room. So again, less reflection.
- I would incorporate a double door that can be closed when necessary to get some isolation between the control room and tracking room.
- Soundproofing to the outside world would not be compromised only the seperation between control and tracking room would.
- This design needs only one access point to enter from the outside world (door in tracking room). The door will be the weak point so better just one then two.

Disadvantages:

- Less seperation between rooms.
- Designing a double door that has some soundproofing skills...
- Not really one big room (some separation)

I really like this design though...

What are your thoughts?
Regards, Thomas