Building a control room - Room mode treatment

[pabloandura]

¡Hello everyone! I’m part of a team trying to build a recording studio in the urban area of Buenos Aires, Argentina. It’s amazing to finally be writing a post after so many years reading on the low.
The studio construction is already underway and it will be located on a second floor . The original use for the structure was a house.
We plan on tracking about anything required, so I would say the loudest thing being drum tracking .
In the first floor below the studio there is no issue with noise transmission.
Our main goal is for about 50 db of transmission loss in the recording room and for a flatter response on the control room.

I have understood that this project will take time to complete. Since we have the ability to do a lot of the handy-work ourselves we will try not to hire carpenters and masons as much.
We have two rooms: a control room sized 4m x 3.46m x 3m tall and a recording room sized 4m x 4.76m x 3m tall. The wall between the rooms is 15 cm thick and it’s made of hollow brick. All the other walls surrounding the structure including the floor are 30 cm thick and are made of common brick.
The floor for both rooms is made of lumber and there is a small space (about 10 cm) to a 20 cm thick floor made of reinforced concrete. An outdoors facing window was covered up in the control room with the same material and the same thickness as the wall it’s on. The same with a door that connected each room with each other (it was covered up with hollow brick).

Sketchup 1.png

We have been investing time into fixing all the building-health concerns we found. We re-plastered one of the inside walls of the recording room and one of the outside walls of the control room. Also putting 3 layers of liquid membrane (paint) on the ceiling since it had asphaltic membrane for about 40+ years in now.

Our first objective is to get the control room finish first, so we can next take care of the recording room.

My initial questions for this thread are regarding room modes.
Since this is a small room I have considered an approach similar to Live End Dead End.

There is a door near a corner I only have three other corners for super chunk bass traps and I will be positioning a super chunk on top of the observation glass.

Questions:

Should the four super chunks be a 1/4 wavelength of my lowest room mode on that surface?
Will all of this porous absorption be enough to calm the low frequency resonances?

In case 2 is a no, I have been experimenting with piezo mics in pieces of wood trying to understand how mechanical resonance works. Which to be honest I still don’t understand how they do their magic.
So please confirm this information:

3) Will 20 mm plywood with a surface density of 3.75 kg m2 resonate as a panel at about 38cm at a frequency of 50.5 hz. (0 1 0 mode).

4) What should I use to bind the plywood to the resonating box for it to resonate easily?

Sketchup .skp
REW Stuart's way

[Soundman2020]

Hola Pablo, y muy bienvenido al foro!

The studio construction is already underway

Hmmm.... that's a problem! It seems that you don't yet have any plan for how to build the studio, so I'm confused about how you can be building it already! Exactly where are you in the process? What have you built already? Where are your plans?

it will be located on a second floor

Since you added a sad face after that comment, I guess you already know that this is not the best place to build a studio, since it places limits on how much isolation you can get...

I would say the loudest thing being drum tracking

So you expect to have a level of around 115 dBC, maybe higher, in your studio? And you are going to build it on the second floor? I do hope your neighbors are a long, long distance away....

In the first floor below the studio there is no issue with noise transmission.

What about the other five sides of the studio? You only mentioned one direction, but there are six...

Our main goal is for about 50 db of transmission loss in the recording room

It is certainly possible to get 50 dB TL in a home studio (here's an example: http://www.johnlsayers.com/phpBB2/viewt ... =2&t=21368 ), but only if you are on the ground floor... or if you have a LOT of money to spend on the complications that will arise from trying to get high isolation for low frequencies on an upper floor.

for a flatter response on the control room.

That is possible, if you build it big enough and treat it suitably. Follow the guidelines in ITU BS.1116-3 specification, and you will be able to do that. If you build it smaller than the recommend minimum size stated there, then you probably won't be able to achieve that... unless you design it very, very carefully, and treat it very, very carefully.

a control room sized 4m x 3.46m x 3m tall

That's not going to help you achieve your goal! That's only a little more than half the size it needs to be to get flat response. BS.1116-3 specifies a minimum floor area of 20m2. You only have 13.8. While it is POSSIBLE to have a room smaller than the ITU specs, it is going to be very complicated to treat that room, and it won't give you flat response even then.

Also, if those are the dimensions of the original room (brick walls), then that's no use: we need to know the dimensions of the final inner-leaf room, after you put complete the isolation system. How big will the final room be, AFTER you have built the inner-leaf, but BEFORE you put any treatment it?

The high ceiling is good: that can help. But the floor area is too small, really. Is there any chance you can make the CR bigger?

The wall between the rooms is 15 cm thick and it’s made of hollow brick. All the other walls surrounding the structure including the floor are 30 cm thick and are made of common brick.

That's useful, but what about the roof?

The floor for both rooms is made of lumber

What dimensions for that lumber? What is hte dead load and live load that it is carrying now? How much extra can it handle? What is the load-bearing capacity of that floor? How do you plan to reinforce it? Unless it is a massively built floor, with way over-sized joists, it likely will not be able to carry the huge load that you will need to place on it, in order to isolate a drum kit in the second floor. Did you get a structural engineer to inspect that floor? Do you have his report? You will need to know the load limits BEFORE you start building, to make sure that you don't overload it and cause it to fail.

The same with a door that connected each room with each other

Why? How come you do not want easy access between the two rooms? What was the reason that lead you to block up the doorway there?

Also putting 3 layers of liquid membrane (paint) on the ceiling since it had asphaltic membrane for about 40+ years in now.

How is hte ceiling built? And the roof? Do you have enough mass on those to ensure that your MSM resonant frequency will be low enough that you will be able to obtain the isolation level you want?

Since this is a small room I have considered an approach similar to Live End Dead End.

That's not a good idea. True LEDE design was a concept back in the 70's and 80's, but it was abandoned as it was found to be uncomfortable and fatiguing for long sessions: it does not sound natural. Nobody builds true LEDE rooms any more. There are extensions to LEDE, and modifications of LEDE, which are far better, and most modern rooms are designed using one of those principles.

There is a door near a corner I only have three other corners for super chunk bass traps and I will be positioning a super chunk on top of the observation glass.

I don't understand: That is NOT LEDE! If you are doing a LEDE room, then why would you have bass traps arranged like that? Your diagram does NOT show a LEDE room, either....

Should the four super chunks be a 1/4 wavelength of my lowest room mode on that surface?

Do the math, and you can answer your own question. Your lowest mode for the dimensions you describe, is 43 Hz. The wavelength of 43 Hz is 8m. So if you want them to be a quate wave deep, then you would have to make your Superchunks 2m thick. So, 2m thick in the front corners, plus 2m thick in the back corners, means your bass traps would be taking up 4m of the room length, and 4m of the room width... which is sort of hard to do, because the room is only 3.46m wide!

There's your answer, I think: it would be physically impossible to have Superchunks that are 1/4 wavelength thick for your lowest mode. And you do NOT need to do that in any case: the "quarter wavelength rule" is a myth: porous absorption of the correct type can be effective down to 3.5% of the wavelength for randomly incident sound, and 7% for normally incident sound. Superchunks are usually about 90cm along the walls, or maybe as little as 60 cm, and there are other forms of bass trapping that can fit in lesser space.

Will all of this porous absorption be enough to calm the low frequency resonances?

No. Damping the room modes is more complex than just putting absorption in a couple of corners. Take a look at the thread I linked you to above, to see what the process is for treating a small room. That room ("the corner control room") is almost complete: just a few small details that we are working on still: Here's a link to another thread, that was completed a couple of years back, so you can see how a properly designed and treated studio can turn out: http://www.johnlsayers.com/phpBB2/viewt ... =2&t=20471

In case 2 is a no, I have been experimenting with piezo mics in pieces of wood trying to understand how mechanical resonance works.

That depends on what you are trying to use it for! There are several ways that wood can be used in room treatment. From your comment, it seems that you are wanting to build membrane traps? Is that it? If so, for what purpose? What frequency are you targeting?

3) Will 20 mm plywood with a surface density of 3.75 kg m2 resonate as a panel at about 38cm at a frequency of 50.5 hz. (0 1 0 mode).

No. You are not understanding the principle of panel traps (membrane traps). The panel by itself is irrelevant. The panel is part of a resonant SYSTEM, that has to be built very carefully, and tuned properly. Even then, it's hard to do right. I seldom use membrane traps in studios I design: I do use them, but not very often, as they are such a pain to get right.

The principle is simple: you have a panel arranged over a sealed cavity, with a layer or porous absorption set a short distance behind the panel, inside the cavity, but not filling it. This is a pressure device, so it responds to the pressure component of the wave, not the velocity component (which is what porous absorbers respond to). The pressure changes in front of the panel cause it to move in and out, which compresses and then rarefies the air trapped in the sealed cavity. The air acts as a spring, and the panel acts as mass, so this is a simple one-degree-of-freedom resonant system. It will resonate at one fundamental frequency, and the porous absorber just behind the panel absorbs some of the energy of that resonance: it acts as a damper on the "spring" (air), just like the shock absorber in your car acts as a damper on the suspension springs. If you choose the materials carefully, and tune it properly, and test to make sure that it really is tuned to the correct frequency, then it can be useful... provided that you locate at the position in the room where the pressure peak for that mode is located, and provided that you make it large enough to deal with the magnitude of that specific mode! Even then, if you don't design it correctly, it can make matters worse, not better. A lot of people don't take into account that the membrane trap RESONATES, and the panel has a lot of MASS. Therefore, it takes a few cycles to even start reacting to the mode, and it can carry on resonating after the mode is already gone... which means that it EXTENDS the ringing of the mode, instead of REDUCING it.

at a frequency of 50.5 hz. (0 1 0 mode)

You do not have any modes at 50.5 Hz, based on the dimensions you gave! Your lowest mode is your 1,0,0 mode, not your 0,1,0 mode. Your 1,0,0 is at 43.1 Hz, and your 0,1,0 is at 49.8 Hz.

4) What should I use to bind the plywood to the resonating box for it to resonate easily?

That's part of the problem! In order for a for panel trap to work correctly, the panel must move as one single mass, like piston does in a car engine. If you do what most people do, and simply nail the panel onto a wooden frame, with glue in between to get a good seal, then it does not move like a piston! Instead, it bends in and out: the middle moves, but the edges are fixed. So it does not act as a panel trap! You know have bending waves going in as well, and that messes up everything, since bending waves move across the surface of the panel, not into the cavity, and hey occur at different frequencies for different angles of incidence.... So the device does not resonate at the frequency you designed it for, and it does not work. It will trap other frequencies (which are very complex to calculate), but it won't do a lot for the one you want it to. Room modes are high Q, and need a high Q device to treat. A membrane trap built with the panel rigidly attached is not a high Q device.

So, one way of dealing with that is to use a very flexible, thick, soft rubber seal, between the panel and the frame. That works... but then you have the problem that the rubber will deform due to the weight of the panel, and that de-tunes it. Plus, it still does not completely eliminate the problem with bending waves, because the theory assumes that the panel is totally rigid... but real panels in the real world are not rigid. Even very thick plywood still is not totally rigid, and can still have bending waves running in it... but you can't use such a thick panel in any case, because it would be be too heavy, and you'd run into the problem of the inertia of the panel extending the resonant tail, as I mentioned above.

So panel traps can work, but they are very complex to tune.

Sketchup .skp

I cannot open your SketchUp file, since I am using SketchUp Pro 2017. I will not upgrade until the have a version that makes sense, and 2018 makes no sense: it has the same bugs and limitations as 2017 (they did not fix them) and the only new features in there are of no use to me. So please save your file in SketchUp 2017 format.

REW Stuart's way

What are we seeing in that REW data? It does not seem to match the room dimensions you gave. At least, there's no evidence of the 1,0,0 mode, and the 0,1,0 mode is off by a couple of Hz. Are you sure you measured the room dimensions accurately?

Also, your sound card is screwed!

Pablo-REW--FR--Soundcard-screwed..png

That's not what a soundcard should show. Either you did the loopback test wrong and there is a feedback loop in your system, or you have a terrible soundcard that needs replacing. That's not a valid result.

There's somthing badly wrong with that data: it is showing decay times of 0 for several frequency bands, which is impossible:

Pablo-REW--RT--impossible..png

Even anechoic chambers do not get perfect zero decay times.

So there's something wrong with your calibration procedure, or measurement procedure. Please check it, and repeat the measurements. Also note what speakers and what mic you used (brand, model), and where they were located in the room.


- Stuart -

[pabloandura]

Muchas Gracias Stuart, por tu reveladora revisión.
The first thing I'm doing tomorrow is redoing all my measurements.

It is certainly possible to get 50 dB TL in a home studio but only if you are on the ground floor... or if you have a LOT of money to spend on the complications that will arise from trying to get high isolation for low frequencies on an upper floor.

I will re read that topic!, the isolation for the recording room we were thinking on maybe floating a drum booth.
We are not focusing at the moment on the recording room, but we will pay a structural engineer to assure us I can do whatever necessary.

So you expect to have a level of around 115 dBC, maybe higher, in your studio? And you are going to build it on the second floor? I do hope your neighbors are a long, long distance away....

I was very vague with the outside of the structure.
I assume the wood on both floors is 4 to 5 cm thick. It's a hardwood floor placed in a diagonal pattern. I will confirm this information tomorrow.
The sweet-spot is looking southwards
The north and south corners of the entire second floor have no neighbors. I do have 2 neighbors on each side of the first floor (planta baja).
The street is on the east end.

Sketchup 1.png

That is possible, if you build it big enough and treat it suitably. Follow the guidelines in ITU BS.1116-3 specification, and you will be able to do that. If you build it smaller than the recommend minimum size stated there, then you probably won't be able to achieve that... unless you design it very, very carefully, and treat it very, very carefully.

Those are wonderful guidelines, they are great to understand what is the international standart.
I will review this new focus.

While it is POSSIBLE to have a room smaller than the ITU specs, it is going to be very complicated to treat that room, and it won't give you flat response even then.

Interesting, we will try to achieve the best we can do with our resources. In my ears many things are better than the living rooms we are used to making music in.
We are not able to expand the Control Room. Unless we took the hollow brick wall and moved it deeper into the recording room.

How big will the final room be, AFTER you have built the inner-leaf, but BEFORE you put any treatment it?

Since reading this review I have not came up with a plan B on those corner bass traps. I understand we have to learn about resonators. I thought that hanging panels may be too space demanding for how much I should yield to bass traps.
We were thinking of slanting the walls but since LEDE is totally out of the picture now, I will redesign the sketchup to come up with the inner leaf dimensions.

Do the math, and you can answer your own question.

Yes, I miss interpreted and mixed my own info.
I was intending to refer to the dimensions of the room. Making bass traps one quarter of the size of each wall. Now I ignorantly assume I would "stack" resonators on top of each other in the corners.

Superchunks are usually about 90cm along the walls, or maybe as little as 60 cm, and there are other forms of bass trapping that can fit in lesser space.

Interesting, we will look into that.

No. Damping the room modes is more complex than just putting absorption in a couple of corners. Take a look at the thread I linked you to above, to see what the process is for treating a small room.

We will thank you for correcting this miss information.

Therefore, it takes a few cycles to even start reacting to the mode, and it can carry on resonating after the mode is already gone... which means that it EXTENDS the ringing of the mode, instead of REDUCING it.

That's very interesting, so how would you stop that ringing? Or is that a reason that treatment for that particular room mode should not be done with a resonator?

You do not have any modes at 50.5 Hz, based on the dimensions you gave! Your lowest mode is your 1,0,0 mode, not your 0,1,0 mode. Your 1,0,0 is at 43.1 Hz, and your 0,1,0 is at 49.8 Hz.

On REW my highest peak is on right is at 50.537hz, 85.731 db and on left the same peak at the same frequency at 86.136 db. That is the method I used to call 50.5 my room mode. Could it be that REW only measured 50.171 hz, 50.537 hz, and 50.903hz and I'm missing the actual room mode in the in between frequencies?

So panel traps can work, but they are very complex to tune.

I would definitely love to learn about it more.

So there's something wrong with your calibration procedure, or measurement procedure. Please check it, and repeat the measurements. Also note what speakers and what mic you used (brand, model), and where they were located in the room.

I will redo all measurements tomorrow! Thank you for your time Stuart.
I used a zoom H5 as a USB interface into my Macbook Pro. The microphone is a Beyerdynamic MM1. The speakers are Dynaudio's LYD-8.
The monitors were 1.2m and 0.98m from the closest corner. The triangle has its sides measuring 1.6m. The microphone was 1.22m forward from the back wall and 2m in between the side walls.
I previously tried to run REW with our Apollo 16 mkII but we were unable to calibrate it. I will also re-attempt to do measurements with it again.

I will upload a more accurate sketchup soon too!

Pablo

[Soundman2020]

the isolation for the recording room we were thinking on maybe floating a drum booth.

It is possible, as I mentioned, but it is very expensive, and not at all easy. This thread might help you understand the issues: http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173 That's about floating the floor of a room, which is what you would need to do if you want to get 50 dB isolation for a drum booth on the second floor.

I assume the wood on both floors is 4 to 5 cm thick. It's a hardwood floor placed in a diagonal pattern.

That's just the finish flooring, and isn't really relevant, for structural issues. We need to know the dimensions of the wood joists that are supporting that floor, underneath. The thickness of the finish flooring is relevant for figuring out your isolation, but not structurally.

The sweet-spot is looking southwards

That's going to be a problem! There's a door into the common room, right where your speakers and front corner treatment need to go. I would suggest that you turn the orientation of your room around, to face north. That would allow you to make the front of your room symmetrical, which is critical. Unfortunately the window would then be at the back of the room, and you'd have to cover it up completely with the necessary rear-wall treatment. The only other option is to move the door, so that it is in the middle of the wall, not one of the corners.

I do have 2 neighbors on each side of the first floor

How far away? Low frequency sound (such as drums) travels equally in all directions, so any sound that gets out of your second floor studio will certainly get into your neighbor's first floor rooms.

Those are wonderful guidelines, they are great to understand what is the international standart.

Chapters 7 and 8 are what you need to read mostly. Your room is too small to be able to achieve those specifications, but you can get close.

We are not able to expand the Control Room.

OK. It is what it is, then. As long as you are ware of the limitations that the room size places on your acoustic response, that's fine.

Since reading this review I have not came up with a plan B on those corner bass traps.

I think you didn't understand what I was saying, about the inner-leaf of your studio... The "inner-leaf" is NOT the treatment. Those are two different things. The inner-leaf is what you need in order to isolate the studio...

Right now you have brick walls around you on all sides. That is your "outer-leaf". It is PART of the isolation, but you cannot get 50 dB of isolation from just 15cm of hollow brick. The density of brick is around 2300 kg/m3, so 15cm thick means the surface density is around 345 kg/m2, IF it was solid, but yours are hollow! The web of a hollow brick is usually 25mm, so twice that is 50mm. Surface density is around 115 kg/m2. According to mass law, the isolation from that is about 40 dB. That's way short of your goal of 50 dB: in fact is only half of what you need, subjectively. Therefore, you need to build a SECOND wall, a few cm away from that, to get the extra isolation. That is your inner-leaf. You do that by building a wood frame that does NOT touch the existing walls or ceiling, and putting two layers of 15mm drywall on only ONE side of that frame, and putting insulation in the cavity between the two leaves. That is your inner-leaf. It consists of those four walls around the room, AND ALSO a ceiling that rests on top of the walls. The ceiling does NOT touch the existing outer leaf walls or the existing outer-leaf ceiling: it rests ONLY on the inner leaf walls. So you basically create a "room inside a room" like this. It also means that you have to have a second door as part of that inner-leaf to line up with the existing door in the outer leaf, and you also have to have a second window as part of that inner-leaf to line up with the existing window in the outer leaf.

That's how you isolate a studio to the high levels that you are looking for.

That's why I was asking about the final dimensions of your inner-leaf: Those walls will take up some space, so you need to allow for that when calculating your modal response. The modal response is with reference to your final inner leaf, not the outer leaf.

All of the above has nothing at all to do with the TREATMENT of the room: that comes AFTER you isolate it. Isolation and treatment are two different things.

I understand we have to learn about resonators.

There are different types of resonators: The ones you were talking about are panel resonators, or membrane resonators, where the resonating mass is a solid object. There are also several types of Helmholtz resonator, where the resonating mass is just air. Some of the variations of Helmholtz resonators are "slot resonators" and "perforated panel". In the thread I linked you to yesterday, you can see how I used slot resonators in the rear corner of the corner control room to deal with some of the room modes. Those are the large things in three places up the rear corner of the room. With those, the air trapped in the slot between each two pieces of wood is the resonant mass, and the air trapped in the cavity behind it is the spring.

I thought that hanging panels may be too space demanding for how much I should yield to bass traps.

Using acoustic hangers is yet another method for bass trapping. You can also see hangers in the corner control room: I used some on the rear corner of the room, between the slot resonator at the top and bottom, and I also used them in the areas above and below the speaker soffits. They work very well, but they are quite large.

We were thinking of slanting the walls

Your room is very small: slanting the walls would make it even smaller.

but since LEDE is totally out of the picture now,

I would suggest that you take a look at RFZ. RFZ is the best extension of LEDE. It's what I use for almost all of the studios that I design these days, and it works very well. The corner control room is a variation of RFZ design.

That's very interesting, so how would you stop that ringing?

You need to keep the mass of the panel as low as possible, but that implies that the air cavity has to be deeper, to still get the right frequency... Or you can increase the amount of damping inside the cavity, but that de-tunes the device, and lowers the Q, so it is less effective.... There are always trade-offs, and many things to take into account when designing room treatment!

Or is that a reason that treatment for that particular room mode should not be done with a resonator?

The advantage of panel traps and membrane traps is that they can be relatively thin and still treat low frequencies... but they are hard to tune, and you need one for each mode.... The advantage of purely porous absorption (including hangers) is that one device covers all of the modes at the same time... but they take up a lot of space... more trade-offs!

On REW my highest peak is on right is at 50.537hz,

Correct, but that does NOT match the predicted mode: According to the dimensions of your room, it should be at 49.8 Hz., not 50.6. So you probably measured the dimensions wrong. Either that, or your room is not air conditioned yet, so the temperature was wrong when you did the REW test. Or maybe your computer clock is not accurate, so REW did not have an accurate reference to estimate the frequency.

I would definitely love to learn about it more.

There's a book with the title "Acoustic Absorbers and Diffusers", by Cox and D'Antonio, that talks about many different types of acoustic treatment, and gives you the equations for calculating each type. It also talks about the problems with each type, and what you can do about it.

The microphone is a Beyerdynamic MM1.

That's fine. Good mic.

I used a zoom H5 as a USB interface

I'm not so sure about that. That's not what the H5 is meant for, and I have no idea what the latency or signal processing through that would be. That might be the source of all the strange things happening in your MDAT file. I would suggest that you get a proper dedicated interface.

The speakers are Dynaudio's LYD-8

How do you have the controls set on our speakers? For the initial REW tests, set all the controls for totally flat response.

The monitors were 1.2m and 0.98m from the closest corner.

How can that be??? The speakers and the mix position must be set up totally symmetrically in the room. The room is 3.46m wide, so your speakers should be about 93cm from the side walls (so they will be about 160 cm apart), and tight up against the front wall of the room, with only a 10cm gap between the rear corner of the speaker and the front wall.

The microphone was 1.22m forward from the back wall

That is way too close to the rear wall. The room is 4m long, so the mic should be about 145 cm from the front wall (where the speakers are), and therefore about 255cm from the rear wall. That's still not fare enough form the rear wall, but it's about as far as you can get in that size room.

The triangle has its sides measuring 1.6m.

Forget the famous "equilateral triangle". It's a myth that you MUST do that to get a good setup. Yes, it works, but no, it is NOT the only way, nor even the best way, of setting up speakers. Especially in a small room like yours, with non-optimal dimensions. It is important that the speakers are the same distance from your head, but there's no reason for them to also be that distance apart from each other. In your case, they will be about 160 apart, and a lot less than that from your ears. The room is too small to have them any other way.

The tip of the triangle is also NOT inside the middle of your head, the way it is shown in many diagrams. the tip of the triangle is at a point about 30cm to 40cm BEHIND your head. Rotate your speakers so they are both pointing at that spot, not at the middle of your head. If you do that, then the speakers are aimed at your ears, which is logical and correct, not at your eyes....

and 2m in between the side walls.

Once again, I don't understand. The room is 346 cm wide, and the mix position MUST be exactly half way across the room, so your mic should be set up 173 cm from each side wall.

In other words, the tip of the mic will be 145 cm from the front wall, 255 cm from the rear wall, 173 cm from the left wall, 173 cm from the right wall, and 120 cm above the floor. The speakers will be 93 cm from the side wall, 160 cm apart from each other, and 124 cm above the floor (all of those are relative to the ACOUSTIC AXIS of the speaker), and 10cm from the front wall (distance between the rear corner of the speaker, and the wall itself).

That's the correct geometry for your room.

I will also re-attempt to do measurements with it again.

OK...

However, you are doing all of this inside the UNFINISHED ROOM, so it doesn't really make much sense! You first have to build your inner-leaf, to get the isolation that you need, and THEN do the REW tests, inside the actual room. You will have to update all of the above measurements as well, to get the correct dimensions for the inner-leaf room, not the outer-leaf.



- Stuart -

[pabloandura]

Hello Stuart,
I know this is heading us into the right direction.
I understand that before any treatment we have to have a plan to finish the isolation first.

Captura de pantalla 2018-11-01 a la(s) 18.42.31.jpg

The inner leaf could be a double layer of drywall on each side wall.
For the front wall I don't think we will add a layer because the recording room will have a double layer too. (Making it a 3 layer wall, which I understand is undesirable)

The new inner leaf would put the observation window in the center of the room.
If the thickness of the wall is two layers of 15mm drywall then that's a total wall thickness of 3cm
The distance air gap in between the east wall is 7cm and the gap between the west wall is 3cm.
The interior distance would be 3.84m x 3.48m x 3m.
The speakers are at a 10cm distance from the wall (rear corner) and a 89cm distance from the side walls (to the side corner of the speaker).
The triangle forms a distance of 1.6m even though i understand now, it does not represent my mixing position. The mixing position is at the middle of the room.
I believe that would be enough isolation for the control room.
We will be reading all this new information that you provided us Stuart.

However, you are doing all of this inside the UNFINISHED ROOM, so it doesn't really make much sense! You first have to build your inner-leaf, to get the isolation that you need, and THEN do the REW tests, inside the actual room. You will have to update all of the above measurements as well, to get the correct dimensions for the inner-leaf room, not the outer-leaf.

After we finish the inner leaf, I now understand, we will measuring the room again.

Pablo

[Gregwor]

The inner leaf could be a double layer of drywall on each side wall.
For the front wall I don't think we will add a layer because the recording room will have a double layer too. (Making it a 3 layer wall, which I understand is undesirable)

The wall separating your rooms is going to be a problem with your isolation.

So either you tear it down and build two separate rooms (the inner leaves) like this: (note, this is 3 rooms, not just two!)

MSM-two-leaf-WallChunk-conventional-NOT-inside-out--three-room--with-corridor--S04.png

OR

One of your rooms has to remain as is and will only have the level of isolation it current has. The other room can have an inner leaf room built in it.

OR

You have a three leaf system which isn't cool.

Greg

[pabloandura]

Gregwor, thanks for those alternatives.
In the future we will consider revisiting the studio's structure and take down the window wall.
But because of the demand of an improved audio environment for our work we will keep the isolation as is for the control room. We will only isolate the recording room.

Thanks Stuart and Gregwor for holding our hand through these first steps, I might have picked the wrong sub-forum.
For the mode treatment I will be looking over the information that Stuart provided us, revisiting the corner control room thread and those guidelines.
I will soon re-update this post as we continue, considering I still haven't "treated the room modes".

Pablo

[pabloandura]

Hello again!

I hope this time I came in more prepared.
I thought of the use of acoustic hangers to treat the room modes on the back wall of the control room and the addition of material to the west wall to put the observation window in center with the room. (103 cm from the left and 99 cm from the right)
Here is a draft picture of what I was thinking about.

subir.png

I understand in this forum we describe acoustical hangers as the ones made with Homasote.
I was planning on making them with cork board 10mm thick, with glass fiber insulation on the sides of them.

From the previous plans I was thinking to add in splayed walls. But after Stuart pointed out that would only make the small room smaller, I discarded that idea.
Instead I will continue to do my research on applying treatment directly to the concrete walls. Since Isolation is not an issue in the control room.

Our monitor speakers are Dynaudio's LYD 8's and the back of them is ported.
Can I still soffit mount them? Or how would I instead prevent the inmediate reflections from the speaker to the back wall and then back to the listening position?
What could you guys advise me to use to add that thickness (4cm) to the west wall to center the observation window to the room?
Would this room treatment be worth the try?

Pablo.

[Gregwor]

I thought of the use of acoustic hangers to treat the room modes on the back wall of the control room

Your hangers are oriented strangely. I'm not entirely convinced that is the best orientation for them.

Also, what treatment are you doing on the rear wall face?

I was planning on making them with cork board 10mm thick, with glass fiber insulation on the sides of them.

If you can't find authentic Homasote, then the cork board will work.

Our monitor speakers are Dynaudio's LYD 8's and the back of them is ported.
Can I still soffit mount them?

Yes.

Or how would I instead prevent the inmediate reflections from the speaker to the back wall and then back to the listening position?

4" of insulation on the wall directly behind the speakers. Push your speakers right up against that insulation.

What could you guys advise me to use to add that thickness (4cm) to the west wall to center the observation window to the room?

I personally wouldn't bother trying to center the window that 4cm. I would just shift my mix position over so that I was centered to the room.

Would this room treatment be worth the try?

This plan seems to only be concerned with bass trapping which is only a part of the process. What about a cloud idea? What about your rear wall (this is a very important part of the process)? Also, you should figure out where you're putting your speakers and how you're mounting them before your try any treatment! Great work on your research and SketchUp drawing!

Greg

[pabloandura]

Hello Gregwor we meet again,

Also, you should figure out where you're putting your speakers and how you're mounting them before your try any treatment! Great work on your research and SketchUp drawing!

Great, my first step should be to have a solid spot for my monitors.
Following what Stuart and you have been instructing us, I would:

• put the speakers 10 cm away from the back wall with 10 cm of insulation behind them to prevent SBIR.
• center them to the room and not the window.
• separate the speakers at an equal distance to the side walls. but like Stuart mentioned, not necessarily the distance between the speakers should be the distance to my head, since my room dimensions are not optimal.

I built some speaker stands that weight out approximately 86 kilos each they are made of OSB and filled with sand. An anti-vibratory rubber pad (the kind used for small engines) to "decouple" the speakers. Considering the observation window is 2m long, should we soffit mount them 1m away from each side wall? Or have them in front of the glass and applying some movable absorber with a 4" inch insulation panel behind it (to apply when mixing and using monitors).

This plan seems to only be concerned with bass trapping which is only a part of the process.

The bass trapping is the aspect that challenged me the most. Now I understand that the hangers should be slightly edge-on to the speaker direction with a maximum tilt of 30 degrees.
According to:

I like to have them angled a bit "off" from being edge-on to the wave front, but certainly not straight across it: no more than about 30° or so, to ensure that the waves are actually "guided" into the thick insulation at the rear and sides of the hanger area.

I will be installing some drywall hangers this upcoming tuesday (or wednesday maybe in australia time). Each drywall panel is 12.5mm thick, and 1.2m by 2.4m.
I was thinking of initially purchasing 2 panels, to make 4 hangers of 0.6m by 2.4m and covering them with 2.5 thick insulation (21.6m2 dense).
See how that changes the low end response. If they work I would build four more hangers to a total of four in each rear corner.

What about your rear wall (this is a very important part of the process)?

For the back wall I'm still unsure, I would imagine I would want a diffusive back wall so that first reflections are less strong than the front sound coming from the speakers. Should I measure the frequency and ray trace the position for the diffusors after I have dealt with the bass trapping?

What about a cloud idea?

For the cloud I understand we would want a main cloud in between the speakers and the listening position (over the desk) and it should be an angled hard top to prevent flutter with a flat ceiling. I imagine it should be as big as the distance between the speakers.
Could I make the cloud out of 5cm insulation on the bottom side and a drywall panel on the hard top side? Or should it be a harder material like 20 mm plywood?
Should I angle it about 12 degrees to the front?

I guess I'm only dealing with the acoustics of the room with baby steps. After the hanging traps, the cloud and the insulation behind the speakers the remaining main topics should be (but please correct me if im off here):

To ray trace the reflections against the listening position with the side walls and such. And
To achieve a good RT60, which my Excel (courtesy of JH Brandt) tells me it should be below 0.26

If you congratulate me on my research and sketchup drawing, then I congratulate you on the hard work that you have already put into your own build!

Thanks for the time spent here,
Pablo

[pabloandura]

I guess I'm only dealing with the acoustics of the room with baby steps. After the hanging traps, the cloud and the insulation behind the speakers the remaining main topics should be (but please correct me if im off here):

To ray trace the reflections against the listening position with the side walls and such. And
To achieve a good RT60, which my Excel (courtesy of JH Brandt) tells me it should be below 0.26

Hello!! I'm back after sometime building which took a long time, we built the bass traps in the back corners of the room and put two clouds up on top of the desk and the listening area. After this we are awaiting more guidance.
I have also made new measurements with the Apollo 16 this time, instead of the Zoom H5 which Stuart mentioned may not be built for that purpose at all .
The measurements still look awful to my ignorant eye, but at least the room is finally air conditioned, therefore I can guarantee that we were at 25 C.

R baseline 2019.jpg

L baseline 2019.mdat.jpg

LR baseline 2019.jpg

And here is the .mdat

The basstraps were built like previously described. In the corners separated by air and glass fiber. They do not touch eachother or the walls on the corner.

trampa 1.jpg

trampa 2.jpg

I doubt the bass traps solved my low-frequency problem, I just expect them to muffle the corner resonance.

The clouds were made of a lightweight mdf sheet and a reinforcing fiberboard skeleton to hang from.

We would like to ask about

• the cloud, and how could I "tune" their height and tilt appropriately?
• How should we go about ray tracing to place the panels and flattening out the middle and higher frequencies of the room?
• Should we do any more bass-trapping?
• I understand we may also be needing diffusion in the back, how could I tell which frequency range needs to be diffused and how much of it should the surface be allocated to it?

Thanks again for your time, and I hope we don't make y'all yell at us too hard.
Happy new year,
Pablo.

[Gregwor]

I downloaded the .mdat and REW says that even though it's got the right file extension, it is not an .mdat!

Greg

[Soundman2020]

I downloaded the .mdat and REW says that even though it's got the right file extension, it is not an .mdat!

Same here.

- Stuart -

[pabloandura]

Well, that wasted your time.
I'm using the 5.2 beta 3 REW. I will download the 5.2 version and measure again.

Pablo

[Soundman2020]

I'm using the 5.2 beta 3 REW.

Me too.... and I have no problem exchanging MDAT files between myself and my clients, most of whom are also using 5.20-beta-3...


- Stuart -