upper floor load limit

[Soundman2020]

So the ceiling slopes. The question is, does the CR finished ceiling need to slope as well? Or should it be flat, meaning the cavity above will be thinner at one end? How much cavity will we need?

The inner-leaf ceiling does not need to slope, but it can if you want it to. It might be beneficial, if it happens to slope in the correct direction. If not, then it might be better to keep it flat, although the slope is not huge. I'd have to do the math and see what makes more sense. But to answer your question, there is no requirement that the inner-leaf ceiling must be parallel to the outer-leaf ceiling (or rather, the "middle-leaf ceiling" in this case... you have a 3-leaf ceiling!)

Having said that, I'd still check with your structural guy to see if you can hang any extra weight form that existing ceiling.

albeit with some steel support, and is probably no where near as strong as a slab

Steel is pretty strong... In fact, concrete has terrible reaction to tensile loads: It is fantastic for compressive loads, but bad for tensile. That's the reason for having all the steel inside concrete slabs, walls, bridges, etc.: the steel is fantastic with tension loads, but lousy for compressive, while the cement is lousy with tension loads, but fantastic for compressive,. Together, steel and concrete are unbeatable, as each complements the other with what it lacks. So if you have steel up there, that's not a bad thing! If it is arranged in the right way, and would be supporting your ceiling in tension, not compression, then it can probably take a pretty decent load....

But you respond that both leafs need to be equal in mass.

For a 2-leaf barrier, yes, but not for a 3-leaf. The best performance in a 3-leaf is when the middle leaf has as much mass as both of the other two combined. In other words: M2 = M1 + M3.

So, as an example, if we are adding 15mm of FC to the drywall off the roof, and 30mm of FC for the inner leaf,

The ceiling, as you describe it, is already two-leaf. It is fully coupled, yes, but still two-leaf. Adding your inner-leaf ceiling will make it three-leaf.

...and leave a 100m cavity, then we have lost 145mm from the ceiling before internal treatments.

Nope! Not if you use my method...

but perhaps it doesn't need to be, after all, there's no one above,

You are not seeing the big picture here: Isolation is all about the full envelope, all around your room, not just parts of it by themselves. It is only as good as the weakest part. If you have walls, floor, doors, and windows all built for 70 dB of isolation, but your ceiling is only built for 30 dB, then your total isolation is around 30 dB. The rest that is built for 70 is wasted. You need to aim for the same isolation on all sides. Sound is like water: one it gets out, it "splashes around all over", following the easiest path. It does not just go in straight lines directly perpendicular to the surface: it wraps around, and goes in all directions. So if your walls are great but your ceiling is lousy, the sound will still get around to being outside your walls....

As for leakage through the ceiling to other neighbours on my floor, it is mainly an issue with the office next to the LR, which will need an extra barrier wall for further isolation.

Not rally. It's the same as above: If you build that wall fantastic but neglect another wall, or the floor, or a window, or the HVAC system, then your neighbors will still hear you. Studio isolation is "all or nothing". You need to think of the entire set of walls, floors, ceilings, windows, doors, HVAC system, etc as one single whole unit that all works together. It is not a set of individual parts that work each by itself. Yes, the individual parts do play a role, but they play an even bigger role as part of the entire system. Your room has only one single isolation system around it, not individual walls. In all directions, that isolation is only as good as the weakest part.

I think you meant that we could fatten the roof/ceiling leaf without the need for an inner ceiling leaf.

Nope! You still need an inner leaf. I guess I didn't explain that too well. I was just proposing to hang that from the outer-leaf, but NOT to eliminate it. You can't leave out the inner-leaf ceiling! That's like leaving the right side wheels off your car, because you only ever plan to turn left...

But surely there is a limit to how many layers of FC the roof will hold??

Yes, and the limit is far, far less than what you would need to create a single-leaf ceiling! (Or a coupled two-leaf, which is similar in many ways...)

I'm assuming the best way to maximise T/L for the floor in 150mm or less is 10 layers of 15mm FC No pads, no cavity, no float...

Nope! That would weigh around 230 kg/m2 (which is 66% of your total load capacity) and it would increase your isolation by roughly 3 dB.

Yup. I do mean three decibels.

The reason is simple: "Mass Law". That's the equation that governs how single-leaf barriers work. Basically it says that when you DOUBLE the mass of a single-leaf barrier, you get an increase of 6 dB in isolation. But that's in a perfect world: in the real world, you get an increase of a bit less than that, each time you double the mass.

But adding ten layers of 15mm FC isn't even double the mass. I would estimate about 3 dB increase. Hardly even noticeable.

Plus, you would not solve the problem of impact noise.... If the FC rests directly on the slab, then there's still a direct flanking path....

Surely the resonant frequency of that floor would be pretty low,

The resonant frequency of a single-leaf floor is not really relevant to the issue of isolation. It only becomes relevant in 2-leaf or 3-leaf barriers.

I get the feeling a damped deck approach will not do enough...

Really? Why?

but what about the way that the double decoupled walls need to stay decoupled at the floor and ceiling?

The walls only need to be decoupled at the ceiling, not the floor. You can try to decouple them at the floor too if you want, but it isn't necessary. If you do decide to do that, here's what you need:

Isosil-anchor-bolt-decoupling-isolation-collar-and-pad.jpg

You could try to do the math yourself, and figure out how to make another type of rubber float, but it's a LOT easier to just buy the correct product.

A slab on top and bottom "short circuits" the inner and outer leafs of the walls.

The inner-leaf walls do not touch the ceiling at all. There's a gap up there. No contact.

Or could the walls also just be "slab" like as well, no cavity, just thick mass.

If there is no cavity, then you have a single-leaf wall. If you have a single leaf wall, then it is subject to Mass Law. See above. There's no getting around the laws of physics: they are the same everywhere in the universe. Mass Law is well understood. It goes like this:

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

Where:
W is the surface density of the panel, and
f is the frequency.

You can do the math yourself, and calculate the isolation for any frequency, and any wall. As long as you know the surface density of the wall (or floor or ceiling, or window) then you can work out how much it will isolate for each frequency. This law is know to be correct for all single-leaf barriers made from typical construction materials.

A designer in Melbourne likes to insist that 2 x 50mm compressed strawboard stuck to each other beats a cavity wall for LF T/L.

Really? I'd like to see the proof of that! Does he have evidence from respected acoustic laboratory tests to back up that claim? Does he have equations to show how it works, and predict the outcome?

In reality, the information I have does not agree with his claims... not in the least! :

Strawboard-STC.jpg

STC-17! : Seventeen. That's all

Not very encouraging.... That's real data from real acoustic tests, not unsupported claims out of nowhere.... The full report is freely available on-line: The note on this specific result says: "Sound Transmission Loss: These results measure the reduction in sound transmission through the [50mm strawboard] when used as a wall or other form of sound barrier." So there you have it. One panel will give you about the same isolation as a cardboard box, and two panels glued together would give you above HALF the isolation of a typical stud wall.

I'd say that perhaps you are not talking to the right people, and would probably not want anyone who makes claims like that to be designing your place.... You can probably ignore any other "advice" you got from that person.

I wish that was true

So do I! But the manufacturer himself says that is is NOT true! The manufacturer publishes the real data, and makes no such claims.... Because any such claim is ridiculous: it defies the laws of physics. It just is not even vaguely close to reality.

the Neotek console is in fact 40 mono channels with 12 stereo channels, and weighs, I think only around 450 kgs. It's 3.2m wide and around 1.3 deep. So probably not as long or as heavy as you thought,

OK, but it's still a monster! But it can probably fit in, if that's the case.

but still too long for the narrow version of the CR as opposed to the wide,

Not really. You have 4.9 m width. Lose 15cm off each side for isolation, leaves you with 4.6m The console is 3.2. So there will be 1.4m of space. Split two ways, on either side of the console, you will have 70 cm. That's PLENTY. That's about the width of a typical doorway (just a bit less).

as opposed to the wide, which I'm pretty set on.

So you don't want to have a control room with good acoustics? That's fine, but I'm not sure that I would invest all of that money, time, and effort into a place that can only be mediocre at best. But it's your money! If you want to do that, then that's your decision.

Triple leaf effect, I get it, but if the roof is tin, and we build either an outer leaf of single slab leaf right against it, then there's essentially no triple effect, no?

That's probably illegal, and would be rather silly. Tin roofing needs air under it. Tin roofing needs to be ventilated. Or insulated. Check your local building code to find out what is allowable, and what is not.

As for internal treatment, particularly LF absorbers in the back wall, what is wrong with the idea of a wall of diaphragmatic absorbers built into the back wall?

Ummm.... I wish treating a room were that simple! I really do! But it if were, I would be out of a job... However, I still have a job, because designing studios and their treatment is a lot more complex than people think. A diaphragmatic absorber (or "membrane trap") will treat one single frequency, period. You will have MANY frequencies that need treating. You will have at least nine axial modes that require treatment, a dozen or more tangential modes, and probably a couple of oblique modes as well, all below the Schroeder frequency for your room. The rear wall can only treat about one third of those, because the others do not ever even reach the rear wall! Putting a diaphragmatic absorber on the rear wall to try to treat your 0,1,0 mode would be rather silly, for example... The 0,0,1 mode does not involve the rear wall at all. It can be treated in the rear CORNERS, but not on the rear wall. But you can't put a diaphragmatic absorber in the corner....

In addition, a diaphragmatic absorber needs a lot of depth, and a lot of area, and is not very efficient anyway. The space used up by one such trap treats ONLY one single frequency, and that space cannot be used to treat any other frequency. On the other hand, the type of trap I use on the rear wall will treat ALL problematic frequencies at once, across the entire wall. So the square meter that treats the 1,0,0 mode will also treat the 2,0,0, and the 3,0,0 mode, and the 1,0,1 mode, and the 1,1,1 mode, and the 1,2,1 mode, and the 1,2,2 mode, and the 2,2,2 mode, and all of the others, It will treat every single mode that involves the back wall, regardless of frequency.

That is efficiency.

Can't be wasting no space with add-on absorbers inside the finished walls...

It is not wasted space if it does its job! That's like saying "we cant be wasting space to put an engine in the car"! And no, there is not enough depth or space on the rear wall to successfully treat it only with membrane traps. I only ever used membrane traps a last resort, for particularly stubborn, problematic modes.

And a membrane trap won't help at all for SBIR.... But the type of rear wall treatment that I do, will.

The goal with a control room is to have totally neutral response across the entire spectrum, in both frequency and time domains, as well as in phase. It CANNOT be achieved if you put membrane traps across the entire rear wall, because the rear wall is needed for many other things at the some time. For example, it is a large part of creating the ITDG, then following it with the diffuse field at -20 db and +20ms delay. You cannot achieve that if the rear wall is a bunch of tuned reflective devices!

Sorry, but your plan is just not realistic if you want food acoustics in your room.

HVAC- school me! Both my other studios had split systems, so I have no idea ... .

A split system is not HVAC! It is a part of HVAC, but it does not provide any ventilation. It only provides the cooling and heating. You can still use split systems in these two rooms if you want, but in addition to that, you also need ventilation. Well, you need it if you want to have enough oxygen to stay alive....

How much ceiling space do I need, at minimum, to give up to HVAC per room? And where? the front? back? the side?

The biggest issue is the silencer boxes. They take up a lot of space. I normally put those in the ceiling cavity, or in the wall cavities, or build them into the speaker soffits. The size will be determined from the HVAC calculations. You first need to know how many room changes per hour you will need in each room, based on occupancy and building code. With that, you use the room volume to figure out what air flow rate you need. Based on that, and using the rules of thumb for air flow velocity, you can calculate what the diameter of your HVAC ducts will be, and what size your registers will need to be. Based on that, you design your silencer boxes such that the international cross-sectional area changes by a factor of at least 2, at both the entry and exit points. Add to that the thickness of the duct liner, and the thickness of the silencer box walls (which you calculate based on the surface density of your walls), and you arrive at the minimum height and width of the box. Then based on how much insertion loss you need, you can figure out how many baffles you will need, and thus arrive at the minimum length of the box.

I was gonna ask if it's unheard of to construct modular wall units of say, 1.5m2 each.

I guess it is feasible, if you have the budget to do that... but how are yo going to get the doors in? And most of all, how are you going to get the console in? If the console frame is 3.2m long, and the elevator is only 2.2m high... it ain't gonna fit! Sure, you can take the guts out of the console in pieces, but the frame itself ... ???

Also what is the weight capacity of the elevator? Can it handle the type of loads you are thinking of?

I'm also wondering about how happy your musician customers will be, at having to drag drum kits, guitar cabs, amps, and road cases up a flight of stairs, then drag them down again after the session....

A double staggered stack can constitute a wall

I'm not sure what you mean by "double staggered stack": If you build your inner-leaf walls correctly, the will be single stud frames with sheathing on only one side.....

I could even have the modules made off site, so as not to disturb the office neighbours as much during construction. Thoughts??

It is possible, yes, as long as you have the money to cover the extra cost of that. Personally, I think it would be cheaper and easier to pop out some windows and use crane to get larger pieces in and out, but that's just me...


- Stuart -

[princeplanet]

Oh, and another thought that makes me consider the "long" aspect for the CR, maybe if I didn't position the console in the middle but shifted to the right 70 cm ( with the side against the wall), then it's much easier for musicians to walk in an out of the LR and I'd be happy with that. Not ideal given the unbalanced reflective symmetry, but surely that is the lesser evil...? To be clear, the entry door to the studio is from the common area to the reception/lounge. Then from there there should be a door in the middle of the CR's back wall, and another between the soffit mounted monitors at the front of the CR to the LR.



The other thing is, I really don't want to lose much more internal space to absorbers and treatment. Obviously the corners will need work, and maybe some shallow absorption else where, but nothing bulky. I'd rather have a few peaks and dips in the room than have it feel like a padded cell... Besides, the ratios are good - Bolt approved! ...

[Soundman2020]

Oh, and another thought that makes me consider the "long" aspect for the CR, maybe if I didn't position the console in the middle but shifted to the right 70 cm ( with the side against the wall), then it's much easier for musicians to walk in an out of the LR and I'd be happy with that. Not ideal given the unbalanced reflective symmetry, but surely that is the lesser evil...?

Depending on how your walls are designed and built (materials, techniques), you might have a bit more than 70cm on each side. It might be possible to move the console over slightly to one side, but I would not move it over completely. Symmetry is critical for a control room. The left ear needs to hear the same acoustic "signature" as the right ear. If not, then the engineer will subconsciously "compensate" in the mix, so the mixes will be slightly "skewed", and sound strange elsewhere.

To be clear, the entry door to the studio is from the common area to the reception/lounge. Then from there there should be a door in the middle of the CR's back wall, and another between the soffit mounted monitors at the front of the CR to the LR.

That's not the way I would lay it out! I already mentioned that there's a much better layout that I would use...

The other thing is, I really don't want to lose much more internal space to absorbers and treatment.

You won't need to, if the room is designed and built properly. The only part that needs a lot of space, is the rear wall, and that is unavoidable in any studio. You will lose roughly 50cm on the back wall, regardless of how it is treated. You have no choice, if you want a usable studio. The back wall is always, without any doubt at all, the source of the majority of biggest problems, including the lowest modal ringing, SBIR, and the diffuse sound field after the ITDG. If you don't treat the back wall suitably, you might as well not have a studio at all!

Obviously the corners will need work, and maybe some shallow absorption else where, but nothing bulky. I'd rather have a few peaks and dips in the room than have it feel like a padded cell...

So you don't actually want a studio: You want a pretty room with speakers and a console in it, and you don't care if it is actually usable as a studio? That's a strange position to take!

You also seem to be misunderstanding what studio treatment is all about. The first, most basic, and biggest priority of a control room, is neutral acoustics. Take a look at ITU BS.1116-2 and EBU TECH-3276. They define the technical specifications that a room MUST meet in order to usable as a critical listening room. If your room does not meet, or at least get close to, those specs, then it won't be much use a world-class control room. If you do not have neutral acoustics and a symmetrical room, then your mixes will not "translate" well. They will sound great in your room.... but not so great when played back on the radio, in a car, on iPhone ear buds, in a club or church, on a home stereo system, on a "boom box" or anywhere else. The ONLY place they will sound good, is in your room. The way to avoid that is very simple: make the room neutral, acoustically, and symmetrical. And there are very specific ways of doing that.

But don't get me wrong! That does NOT mean that the room has to look bad! A good studio designer will make the room look fantastic, visually, aesthetically, as well as performing excellently, acoustically. Take a look at the rooms that John has designed: I don't think you could say that any of those are "padded cells"!

First priority in a studio has to be acoustics. A close second has to be aesthetics. And right up there with those two, in very close third place, is functionality: the room must have good access paths, good traffic flow, good sight-lines, be comfortable to work in, etc.

If your room does not meet those three needs ( #1 acoustics, #2 aesthetics, #3 functionality) then it isn't a studio: it's just a bunch of rooms where people do things, trying to make mediocre music. In fact, some people would switch around #2 and #3, putting functionality above aesthetics. I would not argue with that....

Besides, the ratios are good - Bolt approved!

You seem to be missing the point of what room ratios are all about. Having a good ratio does not mean that you won't have modal problems: It only means that your modal problems will be evenly spaced! They will still be there, just as big as in a room that does not have a good ratio, but they will be spaced around the bottom end of the spectrum more evenly. That's it. Nothing more. A ratio inside the Bolt area does not guarantee a good room. It just means that it will be "less bad" than it would have been. A good ratio does not affect the treatment much. You will still need substantial treatment for the modal issues, regardless of what the ratio is.

Therefor, your modes will still need treating, just the same as in any other room... So will your SBIR, and diffuse field, and flutter echo, and decay times, and curve shape due to Schroeder frequency, floor bounce, ceiling bounce, etc. If you want a studio that actually works like a studio should, then you need to have it designed and built like a studio should be designed and built.

Did you look at the studio in the link I gave you a couple of days ago, including the acoustic response graphs? If not, here it is again: http://www.johnlsayers.com/phpBB2/viewt ... =2&t=20471



- Stuart -

[princeplanet]

PM'd you.

[princeplanet]

Um, not sure if anyone is still watching this space, but I feel a little embarrassed to update this sorry saga with, erm, some good news! (well, for me anyway...). i Get the feeling my structural engineer was preparing me for the worst, hence my alarmist posts, and my desperate attempts to shore up hope for an impossible build on a light weight floor.

So here we are now in this 3rd and hopefully final stanza of this little "feasibility" adventure, with the news that the structure can support 900kg/m2, and that my floor can actually support 500kg/m2 !! And yes, this is on a 125mm slab on the 7th (and top) floor! My engineer seemed as surprised as I was to find the structural beam support to be as over engineered as it is.

So this of course opens up an entirely different realm of possibilities, and I invite you all, even the nay sayers, to help me explore them. Yes, I have been reading up and even talking to various acoustic folk, but this project just might need some "out of the box" ideas. Main reason is that there is no goods lift, and the lift in service is only 2.2 M high and stops at the 6th floor! A poured concrete slab is surely out of the question, so I must consider the heaviest options that take up the least space that I can get up there.

I'm thinking of steel springs under 7 layers of 15mm FC with a 100mm insulation filled air gap. But what would be great is if I can get the whole added floor system down to just 150mm. Same deal for the ceiling, a loss of only 150 mm means I can have a finished room height of 2.86 m sloping down to around 2,75 m. Not great, but perhaps only just workable?

I don't think I can get carried away and start thinking of using steel plates on the floor (or can I?). I read of such floors where structural support was no issue, but space was. Nice solution. Any other suggestions?

[Soundman2020]

So here we are now in this 3rd and hopefully final stanza of this little "feasibility" adventure, with the news that the structure can support 900kg/m2, and that my floor can actually support 500kg/m2 !!

Great! That is, indeed, good news. It does, indeed, opens up some additional possibilities.

and I invite you all, even the nay sayers, to help me explore them.

Main reason is that there is no goods lift, and the lift in service is only 2.2 M high and stops at the 6th floor! A poured concrete slab is surely out of the question,

Why? There is no problem getting concrete poured at that level:

concrete-pump-delivering-concrete-up-SML.jpg

concrete-pump-to-supply-concrete-mix-up--SML.jpg

concrete-pump-SML.jpg

concrete-pump-4-SML.jpg

latrobe-concrete-pumping-SML.jpg

This is a very common situation: needing to get concrete from the truck at street level up to a higher floor, just is not a problem. Simple, fast, effective. Just pop out a window, and they can pour your slab in a couple of hours. Problem solved. Talk to these guys: http://www.meales.com.au/highrise.html

Renting a pump truck for a couple of hours is going to be far cheaper than hiring a crew of workmen for a couple of days to carry the fiber-cement board up the stairs, even assuming that the building administrators would allow you to commandeer the one and only elevator 100% of the time... That's about two hundred standard sheets of FC you'd need to bring up the elevator, then carry up the stairs. Each one weighs 26 kg. Assume that a pair or workmen can carry two board at a time between them, that's a hundred trips. Assume that a round trip (down to street level in the elevator, load up, ride to the sixth floor, then carry up the stairs, put in place, repeat) takes ten minutes, that's a thousand minutes, which is 17 hours. Consider 6 hour work day (allowing for breaks), that's three days work, three days constant use of the elevator.... Not to mention the minor detail that a standard sheet of FC is 2.4m long, but your elevator can only fit something 2.2m...

I'm thinking of steel springs

What springs? What resilience? How much do those springs need to compress in order to float your FC deck? What resonant frequency will the deck have? How many springs? How will you account for the need for more springs / different springs under high-load areas, such as under your console, vs low.load areas, such as empty floor space with nothing on it?

You seem to think I'm being a "nay-sayer" by pointing out all the negative aspects of your plan, but you are totally wrong about that. I'm merely pointing out things that you likely ave not yet taken into account! You seem to think that my purpose is to put you down: Wrong there too! My purpose is to help you do it right, rather than waste many tens of thousands f dollars on doing it wrong.

Floating a floor is not a project that you can take on lightly. It's a big deal. It is complex, it is expensive, and it involves a lot of math and knowledge. You don't seem to have that knowledge (if you did, you wouldn't be asking for it here on the forum! ) But you also don't seem to like the advise you are getting here. You can't have it both ways! I keep on pointing out glaring issues with your plan, and I keep on showing you better ways to do what you want to do, and you keep on ignoring that advice. So I'm sort of at a loss here, as to why you keep on asking!

I'm not sure if you have read this thread, but even if you have, it's probably a good idea for you to go over it again: http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

I'm thinking of steel springs under 7 layers of 15mm FC with a 100mm insulation filled air gap.

Have you done the math? That will give you a surface density of around 160 kg/m2. Over a 100mm air cavity, what is your resonant frequency? At what frequency does the floor isolate? How much isolation do you get, in decibels? Is that enough?

What type of frame will you have under your FC to support it? FC is fragile: it is brittle, and cracks easily. How will you prevent that from happening? Can you afford the 29cm of lost height? Or did you forget to account for the framing that is needed to support your FC, when you figured the height loss?

So many questions, so few answers....

But what would be great is if I can get the whole added floor system down to just 150mm.

A 75mm concrete slab over a 75mm damped air gap would get you a resonant frequency of around 15 Hz. The floor would isolate well from around 28 Hz upwards. Isolation would be around 65 dB. Mason Industries FSN jack-up isolation mounts would do the job nicely. That's 150mm, plus underlay, plus 8mm laminated flooring, and you lose only a tad over 160mm for your complete finished floor

Same deal for the ceiling, a loss of only 150 mm means I can have a finished room height of 2.86 m sloping down to around 2,75 m. Not great, but perhaps only just workable?

You have 320cm total, slab to ceiling. You will lose 16cm for the floor with my method (above), leaving 304 clear height. With my method for the ceiling, making some typical "rule-of-thumb" assumptions, you can lose no more than about 14cm there. That leaves you 290 cm as the acoustic height of your ceiling, and perhaps 270 to 275 visual ceiling height. That's pretty good for a control room, sort of reasonable for a live room. Allowing for typical builder error, measurement error, unforeseen problems, Murphy's law, etc. I would estimate that you can realistically expect a visual ceiling height of around 265 cm, and an acoustic height of maybe 285.

I don't think I can get carried away and start thinking of using steel plates on the floor (or can I?).

From what I can see so far, budget is not a problem here, and there is plenty of money to do whatever it takes. So if you are considering exotic materials and techniques, you could lay some sheet lead and use far fewer layers of FC. Lead is about 8 times more dense the FC, so in theory you could have one layer of 15mm FC, two layers of 5mm lead, and another layer of 15mm FC, which would give your roughly the same mass as seven layers of FC, but in only 40mm thickness, vs. 105mm thickness. Of course, you might have problems trying to get that approved by your local authorities, but it would work wonderfully. That's about it.

You don't have many more realistic options.


- Stuart -

[princeplanet]

So here we are now in this 3rd and hopefully final stanza of this little "feasibility" adventure, with the news that the structure can support 900kg/m2, and that my floor can actually support 500kg/m2 !!

Great! That is, indeed, good news. It does, indeed, opens up some additional possibilities.

and I invite you all, even the nay sayers, to help me explore them.

Main reason is that there is no goods lift, and the lift in service is only 2.2 M high and stops at the 6th floor! A poured concrete slab is surely out of the question,

Why? There is no problem getting concrete poured at that level:

concrete-pump-delivering-concrete-up-SML.jpg

concrete-pump-to-supply-concrete-mix-up--SML.jpg

concrete-pump-SML.jpg

concrete-pump-4-SML.jpg

latrobe-concrete-pumping-SML.jpg

This is a very common situation: needing to get concrete from the truck at street level up to a higher floor, just is not a problem. Simple, fast, effective. Just pop out a window, and they can pour your slab in a couple of hours. Problem solved. Talk to these guys: http://www.meales.com.au/highrise.html

Renting a pump truck for a couple of hours is going to be far cheaper than hiring a crew of workmen for a couple of days to carry the fiber-cement board up the stairs, even assuming that the building administrators would allow you to commandeer the one and only elevator 100% of the time... That's about two hundred standard sheets of FC you'd need to bring up the elevator, then carry up the stairs. Each one weighs 26 kg. Assume that a pair or workmen can carry two board at a time between them, that's a hundred trips. Assume that a round trip (down to street level in the elevator, load up, ride to the sixth floor, then carry up the stairs, put in place, repeat) takes ten minutes, that's a thousand minutes, which is 17 hours. Consider 6 hour work day (allowing for breaks), that's three days work, three days constant use of the elevator.... Not to mention the minor detail that a standard sheet of FC is 2.4m long, but your elevator can only fit something 2.2m...

I'm thinking of steel springs

What springs? What resilience? How much do those springs need to compress in order to float your FC deck? What resonant frequency will the deck have? How many springs? How will you account for the need for more springs / different springs under high-load areas, such as under your console, vs low.load areas, such as empty floor space with nothing on it?

You seem to think I'm being a "nay-sayer" by pointing out all the negative aspects of your plan, but you are totally wrong about that. I'm merely pointing out things that you likely ave not yet taken into account! You seem to think that my purpose is to put you down: Wrong there too! My purpose is to help you do it right, rather than waste many tens of thousands f dollars on doing it wrong.

Floating a floor is not a project that you can take on lightly. It's a big deal. It is complex, it is expensive, and it involves a lot of math and knowledge. You don't seem to have that knowledge (if you did, you wouldn't be asking for it here on the forum! ) But you also don't seem to like the advise you are getting here. You can't have it both ways! I keep on pointing out glaring issues with your plan, and I keep on showing you better ways to do what you want to do, and you keep on ignoring that advice. So I'm sort of at a loss here, as to why you keep on asking!

I'm not sure if you have read this thread, but even if you have, it's probably a good idea for you to go over it again: http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

I'm thinking of steel springs under 7 layers of 15mm FC with a 100mm insulation filled air gap.

Have you done the math? That will give you a surface density of around 160 kg/m2. Over a 100mm air cavity, what is your resonant frequency? At what frequency does the floor isolate? How much isolation do you get, in decibels? Is that enough?

What type of frame will you have under your FC to support it? FC is fragile: it is brittle, and cracks easily. How will you prevent that from happening? Can you afford the 29cm of lost height? Or did you forget to account for the framing that is needed to support your FC, when you figured the height loss?

So many questions, so few answers....

But what would be great is if I can get the whole added floor system down to just 150mm.

A 75mm concrete slab over a 75mm damped air gap would get you a resonant frequency of around 15 Hz. The floor would isolate well from around 28 Hz upwards. Isolation would be around 65 dB. Mason Industries FSN jack-up isolation mounts would do the job nicely. That's 150mm, plus underlay, plus 8mm laminated flooring, and you lose only a tad over 160mm for your complete finished floor

Same deal for the ceiling, a loss of only 150 mm means I can have a finished room height of 2.86 m sloping down to around 2,75 m. Not great, but perhaps only just workable?

You have 320cm total, slab to ceiling. You will lose 16cm for the floor with my method (above), leaving 304 clear height. With my method for the ceiling, making some typical "rule-of-thumb" assumptions, you can lose no more than about 14cm there. That leaves you 290 cm as the acoustic height of your ceiling, and perhaps 270 to 275 visual ceiling height. That's pretty good for a control room, sort of reasonable for a live room. Allowing for typical builder error, measurement error, unforeseen problems, Murphy's law, etc. I would estimate that you can realistically expect a visual ceiling height of around 265 cm, and an acoustic height of maybe 285.

I don't think I can get carried away and start thinking of using steel plates on the floor (or can I?).

From what I can see so far, budget is not a problem here, and there is plenty of money to do whatever it takes. So if you are considering exotic materials and techniques, you could lay some sheet lead and use far fewer layers of FC. Lead is about 8 times more dense the FC, so in theory you could have one layer of 15mm FC, two layers of 5mm lead, and another layer of 15mm FC, which would give your roughly the same mass as seven layers of FC, but in only 40mm thickness, vs. 105mm thickness. Of course, you might have problems trying to get that approved by your local authorities, but it would work wonderfully. That's about it.

You don't have many more realistic options.


- Stuart -

My last post was also posted at Gearslutz and was copied over here. The "nay sayers" were on that forum, not here, sorry!

Not sure how I gave the impression that budget is not a problem, because it is! For example, how much will it cost to get concrete pumped up to the 7th floor for 68 m2, including truck hire, labour and materials? Should I consider only doing this for the Live room and something cheaper for the CR? And as for the lead sheet, surely that's illegal? And if not, too expensive, not to mention toxic?? Are there no other safer, legal and affordable metals? If so, what sizes could they be? Beams or plates?

And what exactly is your method for the ceiling that will lose only 140cm? (or shall I PM for that?). Lastly, with the floor TL you have in mind, will that be greater than the wall and ceiling TL? If so, does it matter in my particular instance (no one above me, but someone directly beside the LR and others directly below?). Also, now that this whole thing starts to seem feasible, I'm now most worried about the office adjacent to the LR, despite a serious decoupled floor, I just cannot imagine enough isolation through the wall there. Why couldn't I consider something like a 1 metre wide 'barrier" wall (along the 7m length) that I could also use as a bass trap / storage area?

[Soundman2020]

My last post was also posted at Gearslutz and was copied over here. The "nay sayers" were on that forum, not here, sorry!

Ahhh! OK. Yes, they do seem to have some of those over there, don't they? The have a few good guys over there, for sure, but some of them seem to be a bit too quick on the trigger, with the "You can't do that" comments, without first getting all the facts... (I'm sometimes probably guilty of that myself, but hopeful not at the same level ...)

For example, how much will it cost to get concrete pumped up to the 7th floor for 68 m2, including truck hire, labour and materials?

Not sure... But how about if you get a quote, so you know for certain? Call the guys in the link I gave you, or their competitors. I found them in a couple of minutes, using Google, so I'm sure you'll be able to find many more if you look harder than I did. Call a few of them, and ask for a quote. Then you'll know if this is feasible or not. And also call your local hardware store, to fund out how much 200 sheets of 15mm fiber-cement board will cost, including delivery to the seventh floor by manually carrying each board up all seven flights of stairs, because the 2.4m boards won't fit in the 2.2 elevator... Compare the two prices, and see which better fits your budget.

Should I consider only doing this for the Live room and something cheaper for the CR?

It might be feasible to do a lower mass system for the CR, yes. I don't know if it would be cheaper, because the cost of carrying every stud, panel, and roll of any type of material that is bigger then 2.2m, up seven flights of stairs, might add up fast.

And as for the lead sheet, surely that's illegal?

Probably, yes. Which is why I wished you luck in getting it approved by your local authorities! But it might be worth checking. It may be allowed, if it is handled properly and encased suitably. After all, it is widely used still in medical radiography, because there's not much else that blocks x-rays and other forms of radiation used in medical procedures. So there must be conditions under which it is allowed. Get a copy of the building code applicable to your area for commercial buildings, and also call your local municipal building inspection office, to chat to the inspector who will be inspecting your place anyway as you progress, to sign off on each stage.

not to mention toxic??

Well, as long as you don't plan to eat your walls, you should be OK on that account!

Are there no other safer, legal and affordable metals?

Next best would be steel plate, followed by aluminium plate, followed by MLV, followed by fiber-cement board, then MDF, drywall, OSB and plywood, in that specific order. That goes from highest density to lowest. Perspective: Lead is twenty two TIMES more dense than plywood. You would need 22 cm thickness of plywood to do the same as one cm of lead. Take that into account when you compare prices. It's not just the cost of one sheet that mattes: it's the cost per kg. If a sheet of lead 10mm thick is "only" twenty times more expensive than a sheet of plywood 10mm, thick, then the lead is actually cheaper.

If so, what sizes could they be? Beams or plates?

Lead foil usually comes on the form of rolls for the thinner stuff, or plates for thicker stuff. MLV always comes in rolls. The rest in sheets. Standard sheet size for many things (OSB, MDF, plywood, drywall, etc.) is 1.2m x 2.4m Other sizes are available, but 2.2m is not a common size.

And what exactly is your method for the ceiling that will lose only 140cm? (or shall I PM for that?)

The concept is not a secret: inside-out construction. But the actual method that I have developed is not something I'd be happy to throw out in public, for free... It has taken a lot of hard work and careful refinement to get it optimized.

Lastly, with the floor TL you have in mind, will that be greater than the wall and ceiling TL?

I would try to make it similar all around. The big problem will be the ceiling, and the HVAC system, not so much the floor or the walls.

If so, does it matter in my particular instance (no one above me, but someone directly beside the LR and others directly below?)

Let me answer your question with a question: If you are in traffic, stopped next to a guy who seems to have the entire sound system for a Grateful Dead concert running in his back seat, and is belting out "music" really loud, and you then open the window on the OPPOSITE side of your car (the side facing away from his car): can you hear the "music" like that? Or can you only hear it when you open the window on the side directly facing his car?

Now, with that answer in mind: does it matter much which side of your studio you have neighbors? Will the one below you still hear the "music" that comes out the poorly isolated ceiling above you?

I'm now most worried about the office adjacent to the LR,

Once again, if you do the layout I have in mind, there won't be any office adjacent to your LR...

I'm now most worried about the office adjacent to the LR, despite a serious decoupled floor, I just cannot imagine enough isolation through the wall there.

Why not? The math doesn't lie.... But I would avoid that layout in any case (see above), and get the noisy part to another location....

Why couldn't I consider something like a 1 metre wide 'barrier" wall (along the 7m length) that I could also use as a bass trap / storage area?

You could if you wanted to, .... if you had enough room to waste! But you don't. Neither of your rooms can afford to lose one meter off the side.


- Stuart -

[princeplanet]

OK, I worked out materials cost without labour- all materials calculated to be equivalent in mass to 100mm concrete:


12 kg/m3 gyprock - 200 mm 16mm @ 3.6m2 = $53 divided by 3.6 = $14,7 = $184 m2

17 kg/m3 FC - 150 mm 15mm @ 2.7 m7 = $147 divided by 2.7 = $ 54.4 m2 x 10 = $ 544 m2

24 kg/m3 concrete - 100mm = $ 120 m2

25 kg/m3 glass - 100 mm $109 (12.5mm) m2 x 8 = $ 872 m2

78 kg/m3 steel - 33 mm 14.4m2 x 16mm = $ 2,769 = $ 384 m2

117 kg/m3 lead - 20 mm $145 m2 @ 1.8mm = $1595 m2


..... so yeah, concrete wins! But if I wanna save 67mm in space for the equivalent mass in steel plate, then for 3 times the price steel plate wins. Not sure how you deal with the gaps when laying steel plates? Also, would you expect "ringing" with the steel? Can it sit atop the rubber or metal springs ok? Or does it need a damping material under or over it? This would of course lessen the space advantage...

[Soundman2020]

It looks like there might be errors in some of your base numbers there. Firstly, all your numbers are off by two orders of magnitude: concrete, for example, is around 2400 kg/m3, not 24 kg/m3. But there are also a couple of numbers that don't jibe at all, even allowing for the two missing zeros. Here are the actual typical densities that I use for my rough calculations:

DRYWALL 685 kg/m3
FIBER-CEMENT 1550 kg/m3
CONCRETE 2400 kg/m3
GLASS 2500 kg/m3
STEEL 7850 kg/m3
LEAD 12000 kg/m3

So it looks like drywall is way off, and your FC is slightly off. The rest are close enough.

..... so yeah, concrete wins!

Yup! Glad you did the math, and arrived at the same conclusion I've been trying to tell you!

then for 3 times the price steel plate wins.

Yep!

Not sure how you deal with the gaps when laying steel plates?

You weld them.... which kind of makes disassembly hard in the future...

Also, would you expect "ringing" with the steel?

If I had a steel floor, I would damp it with a layer of suitable rubber matting, then a layer of OSB, and put the final flooring on that. So do consider that in your thickness calculations. You'd still be ahead, but not as much as you are thinking.

Can it sit atop the rubber or metal springs ok?

I would put neoprene pads between the springs and the steel. Steel springs are good for low frequency isolation, but not so much for high frequency. Neoprene is good for high frequencies, not so much for lows. But don't forget that the actual, real "spring" in any floated floor, is the air, not the resilient material. They work in parallel, but the resilient support reduces the total isolation effect. It does not increase it, as some people seem to think. It's the air that does the magic.

Or does it need a damping material under or over it?

Neoprene pad between spring and floor deck (regardless of material). Rubber matting on top of deck (in the case of steel). The rubber matting and extra layer of OSB are only needed for steel, not for concrete.

- Stuart -

[princeplanet]

Haha, yeah, x 100 for those figures obviously, sorry!

And yes, way off with the drywall, this time I got:

16mm fyrcheck = 784kg/m3 means 300mm to be equivalent to 100 mm concrete = $276 m2

still half the price per m2 of the FC - (which was "hardie board"- a little denser than other FC )

Steel plate seems good value until you consider the welding costs and other layers required, but if we go for the 75 mm concrete slab as you suggest with the 75 mm air gap (or is 100mm concrete - 50mm air gap better?), and I'm allowed to get a boom up there for the pour, then I'm sold! Of course will need a quote for the truck, preparation and labour..... Then it's a question of neoprene blocks, vs springs vs jacks. I'm told the steel springs are 3 times more effective than the rubber, and that the jacks are best because they guarantee that the slab is lifted to the required height, without any chance of "bridging". Thoughts?

[Soundman2020]

Then it's a question of neoprene blocks, vs springs vs jacks. I'm told the steel springs are 3 times more effective than the rubber,

Compared with which rubber? There's a huge range of rubber types and characteristics out there... I'd be careful of claims like "steel springs are 3 times more effective that rubber". Sort of like saying "planes are three times faster than cars", without knowing anything at all about the planes are the cars. I could come up with quite a few combinations of cars that are much, much faster than planes.... I could likewise come up with combinations of rubber vs steel where the rubber far outperforms the steel.

I'd suggest you give the guys at Mason Industries a call, and ask for quotes and advice on their floor jacks. They have both steel and rubber versions:

mason-floating-floor-isolation-jack-and-spring.jpg

I'm not exactly sure which one you'd need, as I haven't done any math to figure it out, but I'm inclined to think it would be the rubber version. But I'm sure they can tell you which one better suits your needs, and can figure out how many you will need, where to place them, etc.

I would also suggest that you look into the possibility of floating your entire room, if you really do want maximum isolation. In other words, you'd build your inner-leaf walls on top of the floating floor, and build your inner-leaf ceiling on top of the inner-leaf walls, such that the entire room is floating on those jacks. That's a little more complex to figure out.

Interesting case here:

galaxy-studio-room-float-SPRINGS-PHOTO-4.jpg

That's a view of the springs that isolate Galaxy Studios, in Brussels. That's arguably the best isolated studio on planet Earth, with slightly more than 100 dB of isolation. Note that there is a "sandwich" of different types of rubber on top of the springs, and under the springs. Like I mentioned before, steel has characteristics that are good in some ways, but not others, while rubber has characteristics that "fill in the gaps". So a combination of both is what you need if you want maximum isolation. If not, then you could still get some transmission of high frequency impact sounds through the springs and into the floor below. Even though the springs would isolate the lower frequencies quite well, the sound of something dropped on the concrete slab might still manage to get through, as that would be much higher frequencies. For example, the sound of a kick drum pedal by stomped on....

That was designed by Eric Desart, one of the best acousticians in the world, and a well respected member of this forum, who used to post here frequently. Very sadly, he passed away a while back, but his legacy lives on in amazing places like Galaxy Studios.

I'm pretty sure you won't get 100 dB of isolation in your place (it cost them several million dollars to do that), and you don't need that either. But you can conceivably get 60 or better, and if you want to get it as high as possible, it pays to learn from the masters. There's no better master than Eric. I have learned a huge amount from him, and I'm merely passing on to you some of that. It's probably worthwhile taking into account what he did, and applying that can be applied in your case.


- Stuart -

[princeplanet]

Spoke with the crew at Meales, truck with boom pump = AUD $10k, double on weekend or out of hours. PLUS $15-18k to arrange cessation of traffic etc. That's $38K just for the concrete! Throw in anther $8k for the isolation springs and extra for preparation, labour and floor toppings.... that's an expensive floor! Happily, there may be a way to use a line pump to get the concrete up the stairs via a large hose. The cost of the concrete is likely to be closer to $10k if I can get that to happen.

Hey, when are you gonna tell me your idea about where to locate to CR ? I just can't see a solution that would suit me other than last shown, although I have asked the struct eng to see if there are alternative ways to spread the load of the 2 rooms. I really can't have people entering in and out of the common area without sound locks, and I really can't afford the space to have them. Also, I'm not allowed to alter anything at all in the common area. Along with any other jealously guarded secrets, you can always PM me - I did try to PM you while back, but didn't get a response from it.

Even if you are not willing to divulge all , I'd at the very least love to know what specific things you'd advise on, what TL spec you'd aim for, the estimated cost of materials and labour as well as your own costs as designer / mentor? Oh, I'm quite confused about whether it's better to have a 100mm slab with 50mm gap, or 75mm slab with 75mm gap, or even 50mm slab and 100mm air gap. For some people the slab thickness is paramount, for others the air spring seems more critical...

I recall your formula: F = 60 / SQRT (M * D) , but I don't understand how that accounts for the original slab underneath it all (125mm on condeck)...?

[Soundman2020]

It seems to me that you want a freebie! You keep on asking and asking and asking, and I keep on giving you more and more, and yet it isn't enough: you still want more, even down to actual design and layout details, and yet you don't seem to be working on your design at all! It looks like you are wanting someone to design your place for you, for free. I've already given you a huge bunch of info, more than I do with most forum members, but when I do that with most forum members, they use it to get stuck into designing their studios, themselves, which is the purpose of this forum. We help those who make an effort to help themselves. The progression with most forum members is that they take the info we give them, and work on their designs, coming up with a basic layout, geometry, rough estimate of materials for isolation and treatment, then they post their preliminary designs, ask questions about things they are getting stuck on, and we are happy to keep on helping them along, providing the bits and pieces they need at each point to keep on doing their own design, refine it, improve it, paths to research, places to look, ... And their threads evolve, step by step, into a feasible studio design, developed by them, with help from the forum. But that isn't the way things are going on your thread. So far, there's one very basic but unworkable layout, and no progression at all with design, calculations, layouts, geometry, etc. Just more and more questions, with not-too-subtle hints that you don't seem to trust our advice, so you are also asking other acousticians, designers, engineers, and forums for the same thing (freebies), ... yet you always come running back here when you get conflicting information from "them"!

So I guess I'm just a little confused here! Are you planning to actually design the place yourself, with help from the forum, or are you wanting someone to do it for you? If it is the former, then great! No problem. Let's see your design so far, based on everything I have said so far, and we can help you correct it, adapt it, improve it, optimize it, etc. But if you want someone to do it for you, you should probably be asking for quotes, not freebies. If that's the case, I'd suggest that you contact John Sayers himself, and ask him to quote you for a complete design for your place.

If you plan to do the design yourself, then it's clear that you are going to need to read up a bit on both acoustics and construction, so I'd suggest two books: "Master Handbook of Acoustics" by F. Alton Everest, and "Home Recording Studio: Build it Like the Pros", by Rod Gervais. They are both available on Amazon. Highly recommended.

But I'll give you the benefit of the doubt, assume you are on the level, and provide some brief answers to this last round of questions:

Hey, when are you gonna tell me your idea about where to locate to CR ?

Flip the rooms around. Invert.

I just can't see a solution that would suit me other than last shown,

You say you are talking to the guys over at GearSlutz, and some mysterious other unidentified people, so it's surprising that none of them has suggested alternative layouts.

although I have asked the struct eng to see if there are alternative ways to spread the load of the 2 rooms.

Where are the support beams that you mentioned? Mark them on your basic outline, accurately.

I really can't have people entering in and out of the common area without sound locks,

As I said, you do not need any doors into the common area is you don't want that. If I were to design that space, I would still put doors there, but they would be mainly just for load-in and load-out, and for convenience, not the main doors. Think it through: There's more than enough info in there to figure out what I'm talking about.

and I really can't afford the space to have them.

You don't need them.

Also, I'm not allowed to alter anything at all in the common area.

You don't need to.

I did try to PM you while back, but didn't get a response from it.

I'll go check: there was a forum glitch a few days ago, so perhaps I didn't get the notification.

Even if you are not willing to divulge all , I'd at the very least love to know what specific things you'd advise on, what TL spec you'd aim for, the estimated cost of materials and labour

So you want the design specs for free too, along with the free layout, and also a free BoM and a free cost estimate? Wow! Most of my paying customers don't need all of that! I'm not a building contractor, I don't live in Melbourne, so I can't quote you for actually building the place. The best I can do on that front is to say that my clients in Australia tell me that building costs are in the range $ 500 to $ 1500 per square meter, for a typical build. Yours might be in that range, or it might not. I would suspect higher in your case, due to the need to hand-carry all the materials and tools up the stairs, and your need for very high levels of isolation. Only a General Contractor in your city would be able to give you a more accurate price, and only AFTER he sees the final design. Trying to estimate the cost of a studio without first knowing anything at all about the studio (other than that it is on the seventh floor and the elevator only goes to floor 6), is unrealistic.

I'm quite confused about whether it's better to have a 100mm slab with 50mm gap, or 75mm slab with 75mm gap, or even 50mm slab and 100mm air gap.

There's no need to be confused: just use the correct set of equations, and you can figure it out for yourself.

For some people the slab thickness is paramount, for others the air spring seems more critical...

Then you are listening to the wrong people! (Again... ) The equations are quite clear, and the problem is quite clear: You need to calculate the combination of mass and depth and infill for a damped, partially decoupled two-leaf MSM floor, with an air spring that is downgraded by the mechanical spring, that will give you the amount of isolation that you need (in decibels), at the frequencies where you need it (as measured by yourself in a typical session), and probably taking into account the Fletcher-Munson curves regarding the human perception of sound. So you will use the equations to draw a set of several isolation curves for various combinations of mass and cavity depth, and you will compare those curves to the one that you want to achieve, and also to the Fletcher-Munson for the levels you are likely to achieve outside the room, to see if you are achieving the goal or not. If none of your initial curves achieves the goal, then you'll have to increase the mass, or the cavity depth, or change the damping infill, and draw new curves until you do reach the goal.

Then you can translate that mass into the type of building materials, and start designing the rooms based on that. As you progress with the design, you will need to check many times to ensure that your proposed total mass is still close to your design goal, and adjust the design as necessary at each point, by either adding more mass, or taking mass away, or going back to the start and adjusting the cavity depth. And you need to do this while also checking that the design does not overload the structural capacity of your floor.

While you are doing all of that, you will also be adjusting the dimensions and shapes of the rooms to optimize the acoustics, such that the control room meets (or gets close to) ITU BS.1116-3, or EBU Tech-3276 specs, taking into account the monitors that you plan to use, and the equipment and furniture that you plan to have in the room.

You will also need to adjust the locations of doors and/or windows for optimum sight lines, traffic flow, accessibility, and isolation, while making sure that this does not interfere with the acoustic response of the room, or produce unforeseen structural issues.

At the same time as you do all of the above, you will also need to do the calculations for the HVAC system, to ensure that you are providing enough fresh air to keep the musicians, engineer, producer, WAGs, etc. alive and comfortable: the rooms will be double sealed, hermetically air-tight, twice over, so it's sort of important to get oxygen in there, and remove CO2. So you'll need to design the HVAC system to provide the correct air flow rate (volume) for the occupancy and dimensions of each room, at a speed (velocity) that is low enough to enable you to achieve NR-15 (or NC.15, if you prefer), which is the typical recommendation for high-end studios. Once you have the flow rates and flow velocities figured out, you can calculate what size ducts you will need, and based on that (along with the usual rules of thumb for insertion loss involving impedance mismatch, absorption, baffles, turns, etc.) you can design your silenter boxes, which are critical parts of th HVAC system, and even more so in your case, due to the need for high isolation. Based on all of the above, you can finally figure out your static pressure, so you can correctly dimension the fan(s) that will move the correct volume of air at the correct speed when faced with the amount of resistance imposed by the ducts, filters, silencers, registers, dampers, HRV, etc. If your calculated static pressure is to high (above about 1" WG), then you'll need to go back and re-design the whole system to make it lower.

Then you will also need to calculate the sensible heat load and latent heat load of each room, compare that with the climate tables for Melbourne, and come up with the correct cooling capacity for your AHU, in BTU/HR, or tons, or kilowatts, or kj/hr, or whatever system is used locally to measure HVAC capacity where you live.

Based on all of that, you can then actually include the various parts of the HVAC system into the design, accounting for the weight of all that, and going back to your original starting point to ensure that you are still within the load range for the springs and/or rubber on which your studio is floated, and making adjustments in other places as necessary.

Once you have all of this basic stuff in place, you can start fleshing out the actual design, double-checking that you are meeting the criteria. For example, if you chose to go for an RFZ style room, then you'll want to do manual ray-tracing to ensure that your angled surfaces really are producing the correct deflections to the right parts of the room, to achieve the design goal, which is a diffuse field that is 20 dB down from the direct field, delayed by 20ms (the ITDG), followed by even decay across the entire spectrum, at the correct decay rate for the room volume and treatment, while still being accurate to within +/- 0.05 seconds between adjacent 1/3 octave bands. If your surface angles don't work to achieve that, then you'll need to adjust them, and repeat the exercise.

At the same time as all of the above, you'll need to be considering how to deal with the modal issues, and what effect your treatment will have on the Schroeder frequency, which is sort of a circular problem that chases it's own tail...

Then you can start thinking about interior decoration: What finish materials to use, what colors, styles, etc.

So the process is not that complicated, once you know what you are doing. It's just a bit tedious, with lots calculations along the way, and lots of repetitive iterations of doing the same stuff over and over, as you have to continuously compromise one thing to improve another.

(I forgot to mention the electrical system, which is something else that needs a lot of care in designing for a studio with high isolation).

I recall your formula: F = 60 / SQRT (M * D) ,

That's actually the equation for panel traps (membrane traps), or for light-wight walls backed by a very massive wall, such as drywall on studs backed by a 80cm thick reinforced concrete foundation wall.

The equation you want is:

Fc=c[(m1+m2)/(m1m2d)]^.5

Where:
c=constant (Varies between 90 for empty cavity and randomly incident sound, to 43 if the cavity is 100% filled with very suitable insulation for normally incident sound. A good guess would be around 50)
m1=mass of first leaf (kg/m^2)
m2 mass of second leaf (kg/m^2)
d=depth of cavity (m)

That's the basic equation, which gives you the MSM resonant frequency of the two-leaf wall (floor, ceiling, window, door, etc.) Consider that "equation #1", and the result it gives you "f0"

You will also need the mass law equation, to apply to the individual leaves for the part of the spectrum outside of the MSM resonance range:

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


Where:
W is the surface density of the panel
f is the frequency

Then based on all of that, you can calculate your isolation for each of the frequency ranges, using these equations:

Full-spectrum-TL-isoaltion-equations.jpg

R1 and R2 are the results of your two mass law calculations.

Or if you don't want to go to all that trouble, and you don't mind a bit of inaccuracy, then you can go with the simplified version of the above:

three-regions-simplified-transmission-loss-equations.jpg

In that case "f1" = 55/d, and everything else is the same.

Or you could cheat a bit, and combine some of the above with the following graph to help you get the answers a bit easier, using educated "guesstimates" from experience:

MORE-THAN-FOUR-REGIONS-of-isolation-TL-mass-law--NOHDR.jpg

but I don't understand how that accounts for the original slab underneath it all

Plug that into the above equations, and you'll see how it works.

And since you seem to be getting wrong "information" about springs, here's the math for that too. ("spring" in the sens of physics, where the spring can be anything that exhibits resilience, such as steel, rubber, air...):

The natural frequency of a spring is dependent by the stiffness of the spring, K, and the mass of the load that the spring is supporting (M), and can be determined by the following equations:

f = 1/2 pi * SQRT (K/M)

Where:
K is the stiffness in newtons per meter (N/m)
M is the mass in kilograms (Kg)


If you don't now the spring constant, then another way of getting to the same answer is by measuring the static deflection of the spring under load:

f = 1/2 pi * SQRT (G/d)

Where:
G is the acceleration due to gravity (9.8 m/s2)
d is the static displacement in meters

But that's undamped resonance, of course. It's different with damping.

That should be enough to get you started on the design. More than enough, actually!


- Stuart -

[princeplanet]

Stuart, I'm sorry and a bit embarrassed that I come across like I'm fishing for free design work! The last studio I built was 17 years ago and I paid Graeme Thirkell and David Flett (2 of the most respected guys in Oz) to do the design. Graeme has since passed on and David doesn't do much these days, regardless, back then I was instructed to build walls featuring plaster/caneite/plaster on both sides of both walls separated by a 50mm gap. Imagine my surprise to find , like Rumplestiltskin awaking after 20 years, how much the world has changed regarding Studio Acoustics!

Seems like I did so many things "wrong" last time for way much more cost and time than what was required, that I thought I should be more careful this time. One thing that is truly remarkable about this new online age of disseminating ideas and advice is that there are incredibly well informed and generous people like yourself happy to give away some of what they know on Forums such as these, for free! I think I get it (although not really sure), I guess it's about building up credibility and trust in a public forum which engenders relationships and contacts that lead to paid gigs, or something. And that's great, I think it can be a wonderful way to seek out those professionals who have the right vibe for each of us...

So, starting a coupla months back, off I went in the hopeful search of some up to date information. Let's see, we have Gervais, Alton Everest and Phillip Newell, which one to buy, oh, I know, let me read snippets of their books and get a feel for their take on things.... oh, hang on, they don't really cover what I might want to do, or if they do, they don't exactly agree.... ok, let's see f I can find other peeps out there, that build lots of studios, yeah, they're the guys I need to speak with, maybe they can tell me from experience what has and hasn't worked for them....

OK, well you can guess the rest- it's surely the same lament regarding all aspects of internet information, there's so many differing opinions out there that one needs to be an expert to sort the wheat from the chaff - but even there, what is wheat and what is chaff will depend on perspective, one man's ceiling is anther man's floor, and all that...

I wish it was as easy as paying one man to "project manage" the whole thing, but It's not, is it? How would I know if it's possible to project manage from another country without being able to get a feel for the subtleties of a space? How do I know if a local guy who can visit the space often, has enough experience in my kind of build to get it right? How do I know if it's possible to reach a compromise b/n what "works" and what feels good to sit in the middle of each day?

Well, questions, questions, questions! I mean, as long as people keep answering them, I'll keep asking! As for your question- Am I looking for a professional designer, or do I want to design the space myself? - I think the answer is both! I'd love to have something designed around my idiosyncratic needs...

I'm a musician, producer, and studio manager - in that order. One thing I am not, and that is an acoustic engineer, nor am I an architect, electrician or HVAC consultant. While it's ok throw up a bunch of equations and say " the numbers don't lie"- it must certainly seem an insult to your profession to think that a musician could down his own tools for a few months and learn to be a studio designer by receiving guidance on a single internet forum.

But I will try to do as you suggest, only that, if I can't deal with it, could I engage your service on a professional level?
If so, then please PM me with details.

Thanks again for your (free) help. FWIW, it's the best I've had, by far!....