Recording & Mixing Studio in Argentina

[Soundman2020]

Source of the post Thank you Stuart!

Source of the post I can probably help you with that.

I'll appreciate that very much. The cloud I'm planning to do is about 3.2 m. length, by 3.3 m. width, with the "front" part angled back, and the "back" part, less angled, and almost against the ceiling. Here go some preliminar drawings.

I'm a little slow here: sorry about that!

That's a pretty big cloud! If you have it hard backed, by estimator says the total weight will be around 250 kg. With no hard back, it comes down to around 120 kg. That assumes you build it with 2x4s, for a thickness of about 90mm. You could go with 1x6 instead for about the same weight (125 kg), and you'd get 140mm thick.

Anyway, that's just rough estimation... a lot depends on the internal design. But whichever way you look at it, it's going to be fairy heavy.

Ok. Sure it'll be simpler. Do you mean these corners?

By the way, I'm planning the other treatment for the room. On the side wall panels, I'll use 10 cm. thick 30 kg/m3 fiberglass. Then, if needed, I'll put some plastic on it, or not. We'll see.

If you do use plastic on those, it would have to be very thin: painter's drop sheet would be good. If not, you run the risk of getting high frequency reflections back to the mix position.

On the rear wall I was thinking hangers could be a great option, beside the diffusor, which isn't designed yet. Rear wall treatment would be 40 cm. thick at midpoint, and thicker at corners.

Yup! You mean something like the photos higher up, of the studio I mentioned before? That's what I would do. Consider the LeanFuser for that rear wall: they work very well, and because they are fractal, they cover a broad range of frequencies. Also, I would consider going a bit thicker than 40cm in the rear center: I suspect you'll need more like 50, maybe even 55.

I read somewhere here in the forum that rear wall treatment has to be 0.07 the lowest axial mode wavelength. In that case, being 5.17 m. my length, it is supposed to be 0.72 m. the minimum thick I should take.

Well, that's a "rule of thumb". There's some leeway with that, for adjustment, depending on the what you do with that depth. Minimum useful depth is around 0.06, yes (1/16 wavelength), but more is better: 0.13 is good (1/8 wavelength), assuming plain absorption. But you can get away with less depth if you also include limp membrane traps or other tuned devices

But does it applies to hole rear wall treatment or just corners? I have to get a well treated rear wall losing the less posible space. If the hole treatment has to be that thick, I'll be losing some room, but i'll be ok anyway.

As much area as possible, but generally you can go thinner in the middle... especially if you use some tricks to scatter the very low end (somthing like bass diffusion, but not really diffusion...)

Beside, there is some room I maybe could take from the air gap of the MSM isolation system, which is greater in the back wall only in order to go ahead with room ratio, but reading Stuart's post about ratios, I think it won't harm getting a little out of my "perfect" ratio and wining some room. The room will still be into good dimensions, wouldn't it? What do you think? Keep exact ratio? Get some extra room?

Personally, I'd go for the extra space in the room! Decreasing the MSM gap to get more room length can be a good thing, as it will drive the lowest mode down lower still in frequency... but it's also a bad thing, because it will drive the lowest mode down lower still in frequency... Modal support down low is a good thing, but lower frequencies are harder to damp...

- Stuart -

[Soundman2020]

... I've been thinking if the inner leaf at control room is really necessary in our case, or if it would be better to take advantage of the room it would take, and the money too. I'm just talking about the control room, where our goal is sound doesn't get off from the room, but we don't really care about sound getting in, in small amounts. For the live room, I'm sure we need the inner leaf, since cars noise could harm any recording. ... the outer shelf is 30 cm. thick brick wall...

Hmmm..... Have you done detailed testing to find out how much isolation you really need?

With a 30cm brick wall, you could get maybe 50 dB TL, but you'd have big problems with single-leaf doors and windows to get that much! If you only have one leaf, then your doors, windows, HVAC, and electrical isolation becomes a lot more complicated, because you now have to get all of the isolation from those using just single units. With a two-leaf wall, you have two doors, so it's relatively easy to get good isolation, but with just a single leaf, you need a huge amount of mass in you door slab, and window glass...

I think we could get rid of it, since the outer shelf is 30 cm. thick brick wall, and the location is a really small and quiet town. Another reason is that almost every post I've been reading about isolation, is with other construction methods (wood studs, drywall, etc., but not concret and bricks, except Tom's one: viewtopic.php?f=6&t=32). What do yo think about?

Many studios are built with concrete or brick shells. The classic case is Galaxy, in Belgium: all concrete, both leaves.

In order to know, the studio owner ordered a SPL meter and when he gets it, he will be doing measurements and there we'll know how our isolation is right know.

Does he know how to do that testing? Will he get a meter that has Leq capability, and leave it running for very long periods, recording data all the time?

There will be double windows and doors anyway, even in the case we get rid of the inner leaf.

How would you do that? I don't see a lot of point in have two windows that are both attached to the same leaf... or two doors. Would you be able to get enough cavity depth to get the MSM frequency low enough?

Meanwhile, does anybody know how isolated a thick brickwall is?

Mass law: Brick has a density of around 2000 kg/m3 (roughly! varies by type of brick), so surface density for 30cm is around 600 kg/m2. Empirical mass law says:

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

Thus: 14.5 log (600 * 0.205) + 23
= 53 dB

Theoretically! But there's a number of factors that could make it considerably less. For example, the quality of the brick laying.... if the bricklayers didn't do a really good job with the mortar, leaving gaps, cracks, pinholes, voids, and varying thickness, then that could cost you several dB in isolation.

And if you have no inner-leaf walls, what will you do for your inner-leaf ceiling?

- Stuart -

[ericwisgikl]

Hi Stuart! I appreciate very much your time and effort answering. Your words are wisdom here

Source of the post That's a pretty big cloud! If you have it hard backed, by estimator says the total weight will be around 250 kg. With no hard back, it comes down to around 120 kg. That assumes you build it with 2x4s, for a thickness of about 90mm. You could go with 1x6 instead for about the same weight (125 kg), and you'd get 140mm thick.

About the cloud, maybe I could make a smaller one, hard back, which will take care of redirecting reflections tough back wall, and treat the rest of the ceiling with a comercial acoustic ceiling, like the one in Studio 3, and fluffy insulation above it, in order to reach our RT60 goal.

Source of the post You mean something like the photos higher up, of the studio I mentioned before? That's what I would do. Consider the LeanFuser for that rear wall: they work very well, and because they are fractal, they cover a broad range of frequencies.

Great! That will be then. What materials can we get here in Latin America in order to replace Homasote for the hangers?

And about de Leanfuser, I like it very much. I was reading about it in Tim's website and wanted to download the instructions for building it, but I couldn't. It seems to be a mailing list problem, or something like that. Anyway, I figure out how to make them reading a post in GS that Tim made some time ago, so it's already designed and waiting to be make.

Source of the post Minimum useful depth is around 0.06, yes (1/16 wavelength), but more is better: 0.13 is good (1/8 wavelength), assuming plain absorption. But you can get away with less depth if you also include limp membrane traps or other tuned devices

Ok, perfect. I assume that after taking some extra length making the back wall gap smaller, I'll use that room for thicker back wall treatment.
What do you think about a limp membrane trap in the front wall, under the window? There is some room there, but I think I will make one only after measurements and if it's really necessary for taming the axial length mode.

Source of the post Hmmm..... Have you done detailed testing to find out how much isolation you really need?

Not yet! The studio was constructed without doing any measurement of background noise and real needs of isolation. So, I think it's a good moment to make some measurements and find it out.

Source of the post Does he know how to do that testing? Will he get a meter that has Leq capability, and leave it running for very long periods, recording data all the time?

Mmmm... haha. By now, our idea was running some pink noise and music program inside the studio, at 100db@1 m. and then take measurements outside, in some locations, and in different hours with variations of background noise. Also taking some background noise samples, to figure out how quiet or noisy is inside and outside.

Source of the post I don't see a lot of point in have two windows that are both attached to the same leaf... or two doors. Would you be able to get enough cavity depth to get the MSM frequency low enough?

Interesting... I was assuming that more mass=more isolation, but it seems to be more complicated than that. With 2 doors or windows in the same leaf, I have to do the math, in order to see if is there enough cavity depth for a low resonant frequency, and probably not... So there will be a frequency (or a range) were sound will pass trough like hot knife in butter right? Do I have this issue with a single leaf too? Is there a resonant frequency if there is not MSM?

Source of the post And if you have no inner-leaf walls, what will you do for your inner-leaf ceiling?

For sure, without inner walls, there will not be inner ceiling...

Source of the post With a 30cm brick wall, you could get maybe 50 dB TL, but you'd have big problems with single-leaf doors and windows to get that much! If you only have one leaf, then your doors, windows, HVAC, and electrical isolation becomes a lot more complicated, because you now have to get all of the isolation from those using just single units. With a two-leaf wall, you have two doors, so it's relatively easy to get good isolation, but with just a single leaf, you need a huge amount of mass in you door slab, and window glass...

I'll give that a serious thought. That's absolutely right. My fear is making all the inner shell, caulking and that, and end up with similar results as we had before doing all that.

Anyway, I'll keep studying, designing and doing the math

Thanks again Stuart!!!
Cheers,

Eric

[Soundman2020]

About the cloud, maybe I could make a smaller one, hard back, which will take care of redirecting reflections tough back wall, and treat the rest of the ceiling with a comercial acoustic ceiling, like the one in Studio 3, and fluffy insulation above it, in order to reach our RT60 goal.

The cloud in Studio 3 is done in several sections, and only some of them are hard-backed. The "wing" modules out to the sides are open backed:

You could do something similar. In fact, there's probably more "hard back" in Studio 3 than is really necessary... but we did go all-out there, to get it as good as it could be.

Also, the drop-ceiling you see in the rear half of the room there is only part of the story: there's more above that, that isn't visible in the photos...

Yes, that really is an insane amount of insulation up there! Those really are full rolls of pink fluffy insulation up there... many! We lost count, in the end. But it was a simple and relatively inexpensive way to do it, because the studio owner is also involved in the construction business, and could get good prices for that. And as you can see from the results: it works!

Great! That will be then. What materials can we get here in Latin America in order to replace Homasote for the hangers?

There's a very similar product called "Sundeala", that you might be able to get there. Not sure, but here's their website in the UK: https://sundeala.co.uk/ There's also a product by Knauf called "Heradesign" that should work. What you are looking for is the type of material used to make bulletin boards, also called message boards, pin boards: the things you used to see in schools, offices, malls, clubs, and places like that where you could pin up papers with messages, exam results, posters, advertising, etc. using thumb tacks. Also used as a backing for dart boards, and other similar applications. It is soft, not very rigid, and lower density than MDF, OSB, pywood, etc..

And about de Leanfuser, I like it very much. I was reading about it in Tim's website and wanted to download the instructions for building it, but I couldn't. It seems to be a mailing list problem, or something like that. Anyway, I figure out how to make them reading a post in GS that Tim made some time ago, so it's already designed and waiting to be make.

Great! There's some improvements I made to Tim's original design, and I created a SketchUp tool that can generate the entire device automatically, based o a few parameters, so there's an alternative for you, if you are interested!

What do you think about a limp membrane trap in the front wall, under the window? There is some room there, but I think I will make one only after measurements and if it's really necessary for taming the axial length mode.

You could do that too, yes. You normally get the best results from rear wall treatment, but basically any place you have for bass trapping is a good place!

By now, our idea was running some pink noise and music program inside the studio, at 100db@1 m. and then take measurements outside, in some locations, and in different hours with variations of background noise. Also taking some background noise samples, to figure out how quiet or noisy is inside and outside.

Pink noise is great for testing and tuning rooms and treatment, but not so great for testing isolation: For two main reasons: 1) The spectrum of pink noise is very similar to the spectrum of plain old ambient noise, so it's hard to tell the difference between them in measurements. 2) Pink noise is constant, and does not vary: it has no percussive sounds, nor transients: in other words, it is too smooth and doesn't represent typical music. The best way of testing isolation for music is with music! In other words, set up a good full-range speaker in the room, and play typical contemporary rock music through it, choosing songs that has a lot of percussive sounds (drums), intermittence (brief pauses in the song), transients, etc. That's a lot easier to detect at low levels outside. In fact, if you think of it, those are the sounds that transmit well: when you walk past a night club, disco, or party, what you hear most loudly is the kick, snare and bass, not so mucyh the guitars, keyboards and singers. As you walk away, you can hear the kick and snare still going strong log after the rest is no longer audible. Those are the annoying sounds that neighbors will complain about, because they travel so well, so that's what you should test with.

That's for testing "How loud", but you also, you need to test for "How quiet". You need some measurements of ordinary ambient background sound in the neighborhood, at all times of day, so you can see what the typical levels are, especially at night. That's how quiet you need to be. And you also need to do some measurements INSIDE the building, as it is right now, to see what the typical ambient levels are like in there.

Basically, measure in many places inside and out, under all scenarios, to get a good picture of the current isolation levels, and also of the background levels. Based on that, you can figure out how much more isolation you need.

I have to do the math, in order to see if is there enough cavity depth for a low resonant frequency, and probably not... So there will be a frequency (or a range) were sound will pass trough like hot knife in butter, right?

Right! That's the point of MSM isolation systems: At the resonant frequency, there is very little isolation at all, and in fact there can be amplification of those sounds. But starting at 1.414 times the resonant frequency, you get isolation, and for all higher frequencies, rising at a rate of around 15 dB/octave (18 db/octave in theory: more like 15 in real life), as opposed to just 6 dB / octave for single-leaf wall. That's the beauty of MSM... which is why studios are normally built using two-leaf MSM isolation. You get MUCH better isolation than for single-leaf. But you do have to design it so that the resonant frequency is at least an octave lower than the lowest frequency you need to isolate. Preferably 2 octaves lower.

Do I have this issue with a single leaf too? Is there a resonant frequency if there is not MSM?

The issue with single leaf, is "Mass Law". You only get an increase of 6 dB per octave (in theory: more like 5 in real life), vs. the 18 (or 15) of a two-leaf wall. Thus, you need huge amounts of mass to get good isolation with only a singe leaf. You can do that with thick concrete or brick, sure, but that only applies to walls.... trying to make a door or window massive enough, is a major challenge... and major expense!

I'll give that a serious thought. That's absolutely right. My fear is making all the inner shell, caulking and that, and end up with similar results as we had before doing all that.

That would only happen if you did a really, REALLY terrible job of building the inner leaf!

The math doesn't lie. 18 db/octave is way, way better than 6 db/octave. And also, you get similar huge increase in isolation each tie you double the mass of an MSM wall... but only a 6 dB increase in mass in the case of a single-leaf wall, for each mass doubling. Hence, you need insanely thing glass and insanely massive doors for a single-leaf studio with high isolation.

- Stuart -

[ericwisgikl]

Hello folks!

It's been some time since last posts. We're about to start the inner leaf construction as the original plan was, because, based on some noise measurements and calculations, and following Stuart advices, I realized it would be a very good improvement in isolation and it is worth.

Based on that, we made a list of isolation devices the studio owner already has, and we realized that they were calculated for an early version of the studio, which would be a little bit smaller, so now we have to get some more WICs and ceiling hangers.

So, having to order more hangers, I thought it was a good chance to understand how they're calculated, and since the ones in the center of the room are different from the ones in the perimeter, and the corners ones, how to determinate that difference between them.

Do anybody here know which is the criteria into the calculation of these ceiling hangers? These go spaced by about 1.2 meters between them.

Here is the detailed data about both rooms: control room and live room:

Control room: 5.28 meters length, by 4.26 meters width, and the ceiling weights about 770 kg. (34 kg/m2)

Hangers available for control room: "30CSCH 130" for center area, "30CSCH 113" for perimeter and "30CSCH 76" for corners.

Mason 30CSCH datasheet:

30CSCH.pdf

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30CSCH.pdf

(1.72 MiB) Downloaded 1491 times

note: when I say "30CSCH 130", I mean model 30CSCH, size 130, as it says in the ratings table on datasheet.


Live room: 7.07 meters length, by 5.21 meters width, and the ceiling weights about 1220 kg. (33 kg/m2)

Hangers available for live room: "W30 130" for center area, "W30 113" for perimeter and "W30 76" for corners.

Mason W30 datasheet:

W30_a.pdf

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W30_a.pdf

(681 KiB) Downloaded 2022 times

Also there will be some acoustic devices hanging from the ceiling once the inner shell is ready. So I'll attach some rough sketches estimating these devices position and weight, in order to take them into account at calculating hangers type and specs.

My doubts around are because I can't understand why people from Mason sold us these hangers, with these specs, since I think they are oversized for the ceilings weight, and these devices only work well around a sweet spot of load. But I hope I'm wrong and it's all about me being not able to understand the right ways of calculating the loads.

I hope anybody could take these doubts out. Meanwhile, I'm waiting Mason's email replies.

Best regards.

Eric

[Soundman2020]

Source of the post Meanwhile, I'm waiting Mason's email replies.

Did you ever get a response from them, Eric? IT does seem a bit odd...


- Stuart -

[ericwisgikl]

Hi Stuart,

I got some poor answers, with wrong dimensions from what I gave them. I'm a bit disappointed about that, but there's no rush yet, since the studio owner is solving some moisture issues before starting with inner leaf.

Anyway, I hope they answer soon, since we'll need some supplies, and import them in my country isn't easy, neither fast, nor cheap.

Cheers,

Eric

[Soundman2020]

I got some poor answers, with wrong dimensions from what I gave them.

That's unfortunate, and unusual with Mason. They are usually pretty good.

In the worst case, if you don't get answers from them, then you could do some simple tests on the hangers they sent you, to determine the basic characteristics, then use that to figure out the arrangement that you would need to get the ceiling to float correctly. It's not that hard to do; just tedious and boring, with many iterations to get it right. Once you have the basic spring data, you can do it yourself. Not ideal, but possible, at least.

- Stuart -

[ericwisgikl]

Yes! That's the idea: learn which criteria is the salesman applying in order to get the results he (doesn't) send me. For instance, I can see from a logical point of view that corners hangers deal with less load than center ones. But I can't say how less load it is.

Meanwhile, I'll try to get some doubts clear from a friend who is civil engineer. I assume he knows how to predict some springs behavior and how much they could be loaded.

Best regards,

Eric