John Sayers' Recording Studio Design Forum Archive

Hi, and thanks for this forum. I have read a lot, and have already adjusted my plans a lot because of it.

So here's the deal: We have a rehearsal room that we are considering dividing to make a good control/mixing room.
The total room is 820cm by 490cm, and ceiling height is 238cm.

We do not need to worry about sound escaping the room, as there are no neighbours to consider, therefore we don't feel we need to change any of the existing walls. The wall separating the rooms will be built as separate walls with an airgap in between, and tho layers of plasterboard on each side.

The new control room will be 300cm wide, 490 long and we are thinking of lowering the ceiling (will get back to that i the questions).
on the middle of each short side of the existing room, there is a massive stud wall to ceiling, and also a beam in the roof (20cm thick and goes down 30cm from the ceiling. Outside it we will also build a new vocal booth as the old one is located where the new room will be.

I'm going to flushmount/soffitmount the speakers (Adam A7X), but have not decided which patent to use just yet. From what i gather, I will have about 60cm of baffle on each side of the monitors.
Now, a couple of questions:

1. When chosing speaker height, should I aim the tweeter at my ear, or the middle between the tweeter and the woofer?
2. My ear height when seated is appr. 110-115cm, this might not be the best height for the monitors considering the ceiling height. (50% area) Should I consider raising them and angeling them down, or will it be alright. Another option would be to lower the ceiling a lot, but I don't think thats the best idea.
3. The front baffle in a soffit installation should be rugged and massive, but is plasterboard (several layers) okay, or is it worth opting for MDF?
4. Is the proposed measurements of the room okay? I can probably squeese in some extra width if I gain a lot from it.
5. I read that some recommend treating the wall in the middle of the two baffles for an even more focused stereo image. What is your recommendation on this?

In the drawing the yellow fields are just some proposed wall treatment (sound panels and basstraps), but that will of course be made after testing the room.
I'm sorry for not providing a complete sketchup, but I have never used Sketchit, and I'm used to drawin on paper

Welcome! Glad to see you've dug into the forum!

1. When chosing speaker height, should I aim the tweeter at my ear, or the middle between the tweeter and the woofer?

You actually want to aim the acoustic axis of the speaker at your ear. You can contact Adam support and ask them where this is. Typically, it is somewhere between the tweeter and the woofer, but different speakers will be different.

2. My ear height when seated is appr. 110-115cm, this might not be the best height for the monitors considering the ceiling height. (50% area) Should I consider raising them and angeling them down, or will it be alright. Another option would be to lower the ceiling a lot, but I don't think thats the best idea.

Good question. Ideally, you never want to compromise space for anything short of it being a perfectly cubic room. With proper acoustic treatment and a properly designed control room (wall and ceiling angles to get you an RFZ listening position), your concern isn't an issue.

3. The front baffle in a soffit installation should be rugged and massive, but is plasterboard (several layers) okay, or is it worth opting for MDF?

Several layers would be fine in regards to mass, however the concern with plasterboard is it's structural strength. Having to cut a nice clean hole for your speaker (with precision) would probably yield less than optimal results cosmetically. For the price difference, the ease of altering wood products is probably worth it.

4. Is the proposed measurements of the room okay? I can probably squeese in some extra width if I gain a lot from it.

You can run your dimensions into Bob Gold's or the Amroc room mode calculator and see how the rooms will perform. Basically, you don't want your room to have any dimension that is close to another. Your live room looks almost square to me, and that isn't ideal. You could probably make your control room wider which would make your live room less square. Mess around with the online calcs and see what dimensions yield the best results. Don't get too hung up on it though. Make sure you have room for everything you want to put in your control room (including people playing guitars and keyboards during tracking sessions). One other thing I can see is that your design doesn't allow any visual communication between you and whoever is in the vocal booth. Also, your vocal booth looks almost square. You could probably layout the vocal booth better.

5. I read that some recommend treating the wall in the middle of the two baffles for an even more focused stereo image. What is your recommendation on this?

Use every wall in your control room do help acoustically. Just like your rear wall, your front wall can really help deal with your time domain response. In an RFZ style room (which yours looks like it's trying to achieve) the front wall contributes to deflecting the sound and therefore, the upper part of it should be a rigid material (like the soffit walls), but on the upper and lower sections, they can be used to treat bass frequencies. The lower section (like in John's design) can also help deal with sound bouncing off the back side of your desk.

In the drawing the yellow fields are just some proposed wall treatment (sound panels and basstraps), but that will of course be made after testing the room.
I'm sorry for not providing a complete sketchup, but I have never used Sketchit, and I'm used to drawin on paper

You're on the right track. What you are missing is ray tracing (assuming you're going with an RFZ style control room). From there, you can determine your wall angles and have a better idea what you'll need for acoustic treatment. Yes, you will do the acoustic measurements during construction which will help you determine exactly how to build the treatment devices, however, since you're building this from scratch and not just throwing some treatment up in an existing bedroom, you have the ability to angle your walls and ceiling clouds in exact angles determined within your SketchUp design.
Also, no where in your design have you shown your HVAC plan. That is a HUGE part of the design and should not be overlooked. Do the calculations for that and Sketch it Up as well.

Keep working on your design before you start doing any construction. Remember, the design stage is ~80% of the build.

Greg

Oh, and I just realized that even with two walls between your live and control room, you will still have next to no isolation between the rooms. The only way to get isolation in your control room will be to have your control room built as a room in a room. The same goes for your vocal booth. This is all assuming you don't care if outside noise (lawn mowers, dog barking, etc) get into your live room during recording. Personally, I recently recorded drums at a live music venue and the water running through the plumbing pipes alone made me want to scream. It ruined several good takes. Something to consider. But isolation is the majority of the costs in a build. So maybe you could just isolate your control room and vocal booth and have an awesome working space.

Greg

Thanks for jumping in so soon

So in regards to the height of the speakers I need not worry so much. Thats a relief.
The soffit mounting will most likely be using Johns design, at least with regards to lower part serving as bass trap, and the lower front of the baffle treated to tame reflections of the desk.

I've attached another design I did making the control room a bit wider (3.2m wide, 4.90m long. ceiling height 2.38) The Live room will still be close to square, but I can't saccrifice any more space there. For our personal use it's mostly drums being tracked. Both guitarists in our band uses Kempers, so we don't need to record "live" guitars. Same goes for Bass. It's mostly DI recording. Of course this may change somewhat in the future.
The live room is treated quite heavily as it is, and we also have som moveable traps/office walls we can move around during usage.

This design also shows a better design for the vocal booth. (I think).

The idea with the new wall is 100mm stud wall with 100mm insulation covered with two layers of plaster board, then an airgap of 50mm, and a 50mm stud wall with 50mm insulation covered with 2 layers of plaster board. This will not prevent sound travelling in the existing walls, but I think we will have enough dampening. It doesn't show from my current drawings, but that was the general idea.

Outside noise is only an issue in the part where I'm placing the control room, as the house is lowered in the terrain on tha oposite side, and has a storage building behund the wall that the vocal booth is placed. On the entrance side there are a couple of metres to the outside walls that are used for storage, so baiscly there is another wall outside the one you see in the drawing.

I'm going to sit down and learn Sketchup in the near future and do some proper designs. Will post them as soon as I have it down

Visual communication with the vocalbooth is not the best, but the door we use there has a window, so with the window in the control room, it will be possible, but not optimal. But hey, we have talkback for communicating

RFZ seems to be the way to go for this room, so I will read about ray tracing and how to to it in Sketchup.

I've checked the "new" room dimensions in Bob Golds calc, and it doesn't look too shabby. Of course I'm new to this, but have read i bit about it on the forum. From what I can see there are no MAJOR issues. It's close to M. M. Louden: 1971: 6th best ratio" 1 : 1.4 : 2.1, and shows an ok Bonello curve.

I think I will opt for the Plaster board baffles, but probably make the bezel in MDF. MDF is extremely expensive here compared to Plaster board.

Thank you for your input so far
---
Stein_R

Just started sketching, and thought I'd share the Sketchup file. https://www.dropbox.com/sh/q1cho3q4yv3a ... hjG_a?dl=0
It has the correct measures, but as there is a cable-duct running on the outer wall, I think I will add some insulation and new plaster so the wall runs out on the edge of the cable-duct. Have not updated the drawing yet to reflect this.
This will give us a bit extra soundproofing, and less heatloss in the winter (we often se -15-20 degrees celcius outside in the winter).

So, a couple of more questions:

1. Since the existing walls, floor and ceiling will carry some sound between LR and CR, will a dual wall as described in the previous post be overkill?
We could of course build a single 100mm stud wall with insulation and 2 layers of plaster board on each side if the existing walls will prevent us from getting good sound proofing anyways.

2. With regards to HVAC, I think all we need is simple fan (will look at fans for outside mounting) and duct that leads primarily to the live room, and then add a smaller duct and a separate fan between the liveroom and vocal booth (small size computer fan, and of course sound traps on both intake and outlet of the VB.

3. Do you think the shape and ratios of the vocal booth will work in the new plans?

Any other suggestions and/or corrections are appreciated

---
Stein_R

1. Since the existing walls, floor and ceiling will carry some sound between LR and CR, will a dual wall as described in the previous post be overkill?
We could of course build a single 100mm stud wall with insulation and 2 layers of plaster board on each side if the existing walls will prevent us from getting good sound proofing anyways.

If you're not able or willing to do a room in a room design for your control room, then your next best bet would be to build it as you described or as a staggered stud wall. The advantage to doing two separate walls (as you described) is that you can have a larger air gap which will lower the resonant frequency and improve isolation. Don't expect great results no matter what though. These types of wall construction are decent for higher frequencies in condos or duplex homes, not full range instruments or music.

2. With regards to HVAC, I think all we need is simple fan (will look at fans for outside mounting) and duct that leads primarily to the live room, and then add a smaller duct and a separate fan between the liveroom and vocal booth (small size computer fan, and of course sound traps on both intake and outlet of the VB.

I don't full follow your concept, but in short, you can have one main supply and return trunk then Y off of each one for their respective rooms. However, for both rooms you'll need silencers for both their supply and return. That way, they maintain their isolation from one another and the outside world. . . . otherwise you might as well open up a door between the room and to outside.

3. Do you think the shape and ratios of the vocal booth will work in the new plans?

They ratio is certainly better! I don't think you need to have the angled wall on it though. You could leave the corners at 90 degrees and install some super chunks there instead.

Here's a thought. Will you be recording vocals and drums at the same time? If not, then scrap the vocal booth all together and maximize your live room space. Small rooms (like your vocal booth) are never going to sound great. You'll get a way nicer vocal recording if tracked in a larger room. Your live room is a good size for vocal recording. Let that idea marinate for a bit and let's see where your next step is.

PS good work on SketchUp so far! Hint: google SketchUp Inference

Greg

When it comes to the VB, we don't really need it after the wall is up, so we're dropping it and saving some space.
Since we do not need to worry about outside noise levels, we will drop HVAC for now. We'll probably install a simple fresh air fan for the LR in the future, but for now we can always open doors and windows

Building room-in-room might prove somewhat difficult. There is a cable duct running along the outer wall (shown in the Sketchup), and it needs to be accessible all the way (building regulations). I will of course double check. Getting an electrician to convert the system will be expensive

Just to be clear; if we can make room-in-room, then one side of the new (double) dividing wall can be connected to the existing walls, and the other side should be a part of the inner wall? And to do this right we also need/should make a new floating floor inside the CR? (The existing floor is a wooden construction)

Another question. When building a dual wall. What's more important; the thickness of insulation, or size of airgap? I've read the airgap should be above 100mm, ideally 150mm? That steals a lot of space, and ideally it would be great if we could then make due with 50mm insulation in each wall, so the total depth would come in around 200mm (minus the plasterboard).

Since we do not need to worry about outside noise levels, we will drop HVAC for now.

I don't follow that argument at all: How will leaving out the HVAV improve the outside noise levels? And how will you be able to stay alive inside the studio, if there is no fresh air coming in? You do realize that studios are totally sealed, completely air-tight? That's very different from the way houses, shops, schools, offices, and suchlike are built: there are always many small air paths for air to get in and out. But that does not happen with a studio that needs high isolation. It is a hermetic box. No air gets in, and no air gets out. Unless you have an HVAC system that supplies the correct amount of fresh air and removes the correct amount of stale air...

but for now we can always open doors and windows

Ummm.... no, you can't! Because it is a studio! You say you need high levels of isolation because you are worried about "outside noise levels". Therefore the windows cannot be operable: they must be fixed, not openable. Even if you could "open the doors and windows", that still is not a feasible solution for a studio, for several reasons. Firstly, you can't use the studio at all if the windows and doors are open! So what would be the point of investing all that money, time and effort to build a place that you can't use half of the time? Secondly, it wouldn't work anyway. Air needs to have a reason to move: there must be a pressure difference between two paths, with a higher pressure in one and a lower pressure in the other. If there is no pressure difference, the air stays exactly where it is. It won't move at all. The normal way of creating a pressure difference, is with a fan in a duct... Third, even if you want to open the doors and windows and also drag out a fan to make the air move, and you are OK with not being able to use the studio for a couple of hours while the fan moves air around... it STILL won't work! The purpose of an HVAC system is not just to move air, but also to control the temperature and humidity, keeping them constant all the time. Instruments, mics, and equipment all need to be kept at the correct humidity and temperature. Opening the doors and windows, dragging out a fan, and shutting down the studio for a few hours does NOT control the temperature and humidity. On the contrary, it causes wild fluctuations in the temperature and humidity, each time you open and close the door.

This is a "solution" that many first-time studio builders come up with all the time: "I'll just open the door". But it isn't a solution at all. It creates far more problems than it solves, and it doesn't even solve anything very much anyway! HVAC is a basic requirement for a studio, just as much as a pair of speakers and a DAW. Without HVAC, you don't have a viable studio. It's not a luxury: its a requirement.

Building room-in-room might prove somewhat difficult.

In that case, isolating your studio might prove somewhat difficult! If you need high levels of isolation then you don't have a lot of choice. You can do a single leaf wall, yes, but the laws of physics say that if you have a single leaf wall, then you will need HUGE amounts of mass to get isolation. Something called "Mass Law" gets in your way. Here's what it says:

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

Where:
M is the surface density of the wall (mass per unit area (kg/m²) ), and
F is the center frequency of the third-octave measurement band.

That tells you exactly how much isolation you will get for any frequency band that you'd like to know about. Plug in a few numbers, and try it. You'll notice that you cannot get good isolation, especially at low frequencies, unless you use enormously large amounts of mass. So if you have plenty of money, and don't mind pouring solid reinforced concrete walls that are half a meter thick, then that's fine! You can, indeed, get very good isolation like that. If that's the case (or if your existing walls are already thick concrete) then you are OK.

On the other hand, if you need high levels of isolation and don't have a big budget, then building the studio as a 2-leaf "room-in-a-room" is the best way to go.

In your case, it seems that you are trying to isolate the control room from the rest of the building, so it seems to me that two-leaf is the best option.

Just to be clear; if we can make room-in-room, then one side of the new (double) dividing wall can be connected to the existing walls, and the other side should be a part of the inner wall?

Right. In other words, you will build a single-leaf wall to divide the existing space in two, then you will build the control room in the smaller part of that divide space. The control room will then be built as a single-leaf: just a stud frame with drywall on only ONE side of it, and insulation in the cavity. You can control the amount of isolation and the lowest frequency where it works, by adjsuting the depth of the air gap between the two leaves, and the mass (weight) of the leaves. There are equations for doing that.

And to do this right we also need/should make a new floating floor inside the CR?

Only if you have a LOT of money! You probably do not need to float your floor. Here's why: http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173 What is under the existing wood floor?

What's more important; the thickness of insulation, or size of airgap?

It's the same thing! The entire air gap must be filled with insulation. (Assuming that you want maximum isolation). The purpose of the insulation is to damp the internal resonance in the cavity. If you only fill part of the cavity then you are still leaving space for resonance to happen. There's a direct relationship between isolation and the amount of insulation inside the cavity. The difference can be as much as 16 dB of isolation, which is HUGE! The insulation actually changes the way sound waves propagate through the air, and also the way the air itself behaves. Putting absorbing material in the cavity changes the process from adiabatic to isothermal and reduces the speed of sound.

I've read the airgap should be above 100mm, ideally 150mm?

The entire cavity should be that deep, yes (and filled with insulation). Assuming you want good isolation down to low frequencies. The equations for MSM resonance depend mostly on three parameters: the surface density (mass) of each of the two leaves, the distance between them (air gap, or cavity depth), and damping (the insulation on the air gap). You can get better islation that works down to lower frequencies by increasing the air gap, increasing the gap, or both. If you have a smaller gap, then you will need more mass to compensate, but once you get below about 100mm cavity depth, then you have gone past the optimum balance, and you start need very large amounts of mass. Not as much as for a single-leaf wall, of course, but still larger than necessary. It gets to the point where the thickness of that mass gets so large that you don't actually save any space at all be reducing the air gap further!

That steals a lot of space, and ideally it would be great if we could then make due with 50mm insulation in each wall, so the total depth would come in around 200mm (minus the plasterboard).

You seem to be confusing the terms here: the ENTIRE air gap is filled with insulation. So if you calculate that you need 100mm air gap in your wall, then that's it! The full distance across the internal cavity, from the inner face of one leaf of the inner face of the other leaf, is 100mm, and ALL of that is filled with insulation. Yes, you can use less insulation of you want, but at the cost of isolation. For example, if your air gap is 100mm deep and you only put 50mm of insulation in there (leaving 50mm empty), then you would be reducing the isolation of your wall by about 6 dB. If you put only 25mm insulation at all in there, then you would reduce the total isolation by about 9 dB.

This is confusing sometimes, since we talk about the "air gap" as though it were only air, but in reality it contains insulation. And when you think about, that makes sense because insulation is mostly air anyway!

- Stuart -

Hi Stuart. Thanks for chiming in.

To clarify some things. I do NOT worry about outside noise levels. There are no neighbours, and we can barely hear anything from the outside as it is. (not at all in the part that will be the LR).
The LR is okay as it is, so the only thing we really need is a good CR that is isolated from the LR

I see your point about HVAC, but for our use it will only need to be a fresh air intake, and outlet. We have heaters in both rooms, and cooling is not really an issue in Norway for the most part This in term means we could have separate ventilation systems for LR and CR since it's just a matter of replacing air in the two rooms.

I see I must have misinterpreted all the drawings and explanations of two leaf walls. In all drawings there has been 2 ply plasterboard, stud wall with insulation, air gap, stud wall with insulation and 2 ply plasterboard. Like to the very right on this image:

If there should be no airgap, we can easily make the wall 200mm filled with insulation. I will look at the calculations first of course.

Disregard the floating floor. I think this was a language-error on my behalf. What I meant was with regards to minimizing sound traveling in the floor construction, but thinking about it now, there really is no good way to build a new floor on top of the existing to decouple it from the existing floor (unless we win the lottery ). I've just been reading a lot of room-in-room posts and articles, and many shows a new floor on top of the existing (with insulation).

Just to be clear; This will not be used as a professional studio. For the most part it will only be for our band, but hopefully in time we will have some other local bands in to do some recording. The MOST important part is getting a good CR for mixing.
Hope this clarifies a bit, and I'm sorry I haven't been more clear in regards of what we're trying to achieve. Also English is not my native language, and technical english even less

Stuart:
From what you now know; should we still go with the room-in-room solution for the control room?

I do NOT worry about outside noise levels. There are no neighbours, and we can barely hear anything from the outside as it is.

Right, but you ARE worried about isolation BETWEEN your rooms... such that the sound in the control room does not "bleed" into the mics in the live room, and also so that you can hear the room mics on the control room speakers without also hearing the same sound "bleeding" through the walls.

not at all in the part that will be the LR

So there is nothing in Norway that could trash your recording sessions? No thunder, rain, jail, or wind? No aircraft or helicopters flying over? No sirens from ambulances / police / fire engines? No trains? No cars arriving / leaving / driving past? Not dogs barking outside? An nothing in the building other, such as water running in pipes, fans, pumps and other motors, people walking on floors, doors closing, people talking, vacuum cleaners, radio, TV, furnace.... There's hundreds of possible sounds that could destroy a good recording, if they get into the mics in your control room. Are you CERTAIN that your control room is isolate well enough that none of that will matter?

I see your point about HVAC, but for our use it will only need to be a fresh air intake, and outlet.

Right. And at each point where one of those ducts goes through a wall leaf, you will need a silencer box...

We have heaters in both rooms, and cooling is not really an issue in Norway for the most part

You seem to be missing the point: You will have several musicians sealed into the live room, which is an air-tight container that is highly insulate with abundant thermal insulation all around, and at least two complete hermetic air seals. You might need heat initially, when you first start a session, but before long you'll need cooling. The equipment and lights put out heat. The human body puts out heat. The rooms are sealed, so the heat has no place to go. But even worse, the human body puts out humidity: with every breath you exhale, the humidity of that breath is 100%. During one day you exhale and sweat somewhere between 1 liter and 4 liters of water, which works out to about 80 ml of water per hour per person, typically, for a musician playing hard. So if you have five people in the room, then the amount of water they emit each hour is about the same as emptying a half liter coke bottle full of water, all over the floor. Every hour. How will your room heater control that? That's the problem. In order for your musical instruments, condenser mics, and some equipment to perform well, the relative humidity inside the room needs to be kept constant at around 40%. That's what musical instruments need, constantly, to stay in good shape (and to stay tuned!). Not to mention that it will get rather stuffy and unpleasant in there after a while.... Heaters do not control humidity. Ventilation alone does not control humidity (imagine if it is raining outside...) Proper HVAC systems do control humidity. An air conditioner (eg, a mini-split system) in cooling mode will FIRST remove excess moisture from the air stream flowing through it, THEN it will cool the air, if needed. These two concepts are referred to as the "latent heat load" and "sensible heat load" of the room. You need to do the math to figure out what that load will be in YOUR rooms, and then you need to dimension the HVAC system accordingly, so it can handle BOTH of those loads.

This in term means we could have separate ventilation systems for LR and CR since it's just a matter of replacing air in the two rooms.

Replacing the air in the room is only part of the issue. Controlling humidity and cooling are the other parts. All good mini-split air conditioners these days can also heat the room, if needed, and they do so far more efficiently than typical electric space heaters.

I see I must have misinterpreted all the drawings and explanations of two leaf walls. In all drawings there has been 2 ply plasterboard, stud wall with insulation, air gap, stud wall with insulation and 2 ply plasterboard. Like to the very right on this image:

Yes, and in EACH of those cases, the "air gap" is the distance across the cavity from one "leaf" to the next "leaf". In some cases, such as between "2" and "3" on the left hand diagrams, the "air gap" is entirely filled with insulation, but it is still considered to be an air gap. I don't know if you have ever taken a close look at the typical insulation used in studios (usually mineral wool or fiberglass), but you'll notice that the insulation itself is mostly air: there's thousands of tiny fibers, yes, but in between those fibers it is all air. So even when the cavity is "filled" with insulation, it is also still "filled" with air. Thus, the name "air gap" is still valid. Of course, that doesn't apply to closed-cell insulation, such as polystyrene ("Styrofoam") insulation, or "foam in a can" insulation, and other similar insulation products, but you would never use those in a studio anyway.

If there should be no airgap,

There is ALWAYS an air gap! It is usually 100% filled with insulation, but it is still an "air gap", since it is still mostly made up of air. It might be filled to less than 100%, in which case it is not isolating to maximum efficiency, but regardless of the percentage fill, it is still "air gap".

If you look at the diagram you posted, the captions even tell you this: The first caption (on the left) mentions that there are two air gaps in that wall: a big one (between "1" and "2") and also a small one (between "2" and "3"). Under the second diagram, it mentions "two big air gaps", and those are the one on the left (between "1" and "2") and the one on the right (between "2" and "3"). The third diagram refers to "one large air gap", meaning between "1" and "2".

there really is no good way to build a new floor on top of the existing to decouple it from the existing floor (unless we win the lottery ).

Let's hop you do win! But yes, you are right: there's no simple, cheap way to float a floor.

I've just been reading a lot of room-in-room posts and articles, and many shows a new floor on top of the existing (with insulation).

One option for your room, is to put down a layer of 1" OC-703 across the entire floor, then two layers of thick OSB, plywood or MDF, screwed and glued together, but without touching the walls (leave a small gap of a few mm, then seal that gap with caulk), then put down laminate flooring on top of that, over a suitable underlay. That's not a floated floor, but it can help to decouple a little, and reduce sound transmission.

The MOST important part is getting a good CR for mixing.

Great! Then make the CR as big as possible, hopefully with a good room ratio, isolate it well from the rest of the building, design it as RFZ, then build it and treat it accordingly. From your diagrams, it seems you are on the right path for that.

Also English is not my native language, and technical english even less

Well, your English is a hell of a lot better than my Norwegian!

From what you now know; should we still go with the room-in-room solution for the control room?

If you want good isolation between the live room and control room, then yes, I would still do that. Even if you only need moderate isolation, that's still the best way to go (you can have a smaller air gap and less mass on the walls). It is far cheaper than trying to get the same level of isolation from a single leaf.

- Stuart -

Alright. So we had to make a choice and went with putting up a simple two-leaf wall dividing the room, to make a simple control room.
The room is finished, and attached is the floor plan and some pictures.

Have made first measurements of the room, and would really like to have someone review them and give some suggestions.
The room is 2.84 by 4.77metres, with a ceiling height of 2.39 meters.

The mdat from REW can be found here: https://www.dropbox.com/sh/q1cho3q4yv3a ... hjG_a?dl=0

Any ideas?

Ooops! Don't know how I missed seeing that and replying! Sorry about that!

Anyway, better late than never...

First problem: You didn't follow the instructions for calibration properly. Maybe you weren't aware of the instructions, so here's the link: http://www.johnlsayers.com/phpBB2/viewt ... =3&t=21122 .

That tells you to do the calibration at 80 dBC for each individual speaker, which automatically implies that when both speakers are playing together, the level will be 86 dBC. Here are you are actual levels:
<As you can see, you did the tests at a level that is about ten times too low: it should have been done with ten times more power. Your level is around 75 dB, but it should be ten times greater, at around 86 dB. Therefore, there's a good chance that you were not triggering all of the modal response in the room, and artifacts like SBIR and comb filtering could appear to be much lower level than they actually are.

So to get a proper result, you'll need to re-calibrate your system to the correct level, and repeat the measurements.

Second problem:

" 2.84 by 4.77metres, with a ceiling height of 2.39" How did you manage to end up with a length that is exactly perfectly spot-on TWICE the height??? Did you not do the math when you designed the room, and check the room ratio?

So right now you have a huge, major, massive modal problem: The math predicts that your 0,0,2 axial mode and your 4,0,0 axial mode, and your 0,2,1 tangential mode, and your 2,2,0tangential mode, and you 3,1,1, oblique mode will ALL fall at exactly the same frequency: about 142 Hz (+/- 2 Hz). Here's the actual prediction, from the calculator that you should have used when designing your room:

141.1 hz (0,2,1 Tangential)
141.1 hz (2,2,0 Tangential)
143.5 hz (3,1,1 Oblique)
144.1 hz (0,0,2 Axial)
144.4 hz (4,0,0 Axial)

And even though you did the REW test at a level that is 100 times too low, the result is clearly, obviously visible: I placed the cursor at 140 Hz, and you can see the modal ringing there. Here's another way of looking at it: the spectrogram: And even in the frequency response graph: And also the RT60 graph: You have similar issues at both the lower and higher harmonics of that: around 70 & 72 Hz (check the waterfall: clearly visible: 1,0,0 tangential, 0,0,1 axial, 2,0,0 axial all at the same frequency), and at around 212-217 Hz (3,3,0 Tangential, 4,1,2 Oblique, 0,0,3 Axial, 6,0,0 Axial, 3,2,2 Oblique, 5,2,0 Tangential). There's also issues related to other modes at around 36 Hz (1,0,0 Axial), 80 Hz (1,0,1 Tangential), 104 Hz (3,0,0 axial), and a few others.

Overall the decay times for your room are reasonable (roughly 210 ms: about right for that room), except for that issue at 140 Hz. However, it is slightly skewed in the entire high end: there's a definite rise between about 2k and 8k, which you can see on the RT60 graph, but also on even on the full-spectrum waterfall:

Another VERY big issue, is the major imbalance between your left and right channels. Here's the graph that shows just the DIFFERENCE in level between the two speakers: Look on the left edge, and note the location of the "0" reading, as well as the scale: Everything above the "0" line means that the left speaker is louder for that frequency, and everything BELOW the 0 line means the right speaker is louder. You have absolutely huge swings there, covering a range of more than 35 dB! For example, at roughly 300 Hz, your right speaker is 16 dB louder, but at about 1800 Hz your left speaker is 20 dB louder. Going down lower, to the all-important bass end of the spectrum: at 100 Hz your right speaker is 12 dB louder, but at 75 Hz your left speaker is 6 dB louder.

This is a big, big problem. Your stereo imaging is shot, and the sound stage is highly inaccurate.

In the above graph, I did not apply much smoothing, so that's higher resolution than your ears are capable of resolving. Here's the same graph smoothe to 1/6 octave, which is a more reasonable representation of how you would actually perceive that:
Still VERY major swings, but you can also see that your left speaker is about 3 dB too loud: turn it down 3 dB, but don't touch the right speaker.

Even so, even at this resolution, the differences are major. Here's what it SHOULD look, like, for a properly done room:

The corner control room (not yet complete: currently in the final tuning process ... details here: http://www.johnlsayers.com/phpBB2/viewt ... =2&t=21368 )
Gareth's room (thread: http://www.johnlsayers.com/phpBB2/viewt ... =1&t=20895 ): Studio Three Productions room (thread: http://www.johnlsayers.com/phpBB2/viewt ... =2&t=20471 ): (In that one, it's not the purple curve at the top, but rather the green curve near the bottom: the green curve shows the difference between speakers for that room. The purple curve is the overall frequency response, which is what you should be aiming for in your case too, but the green curve is the speaker difference curve.)

Control room specifications call for a difference of no more than +/- 1dB between your left and right channels.

So to summarize: symmetry is a major issue that you will need to solve, along with your modal issues, and your high-end issues. If you get all of those under control, then the room will be a lot more usable. Right now, I can't imagine that you can mix well in there. That would be very hard to do, I think. Mix translation is probably a big issue for you, right now.


- Stuart -

Thank you for the in-depth analysis, and no worries on missing my post

When it comes to the room ratios; I knew they would cause issues, but it was a matter of preserving usable space for the liveroom (which also serves as a rehearsal room for my band). But I must say I regret the decision somewhat after these results, and yes; as it is now mixing is almost impossible.

I have just ordered a good SPL-meter, as the one I used is not of good quality. I will calibrate my setup and do new measurements when I get it.
I have also gotten an Adam Sub 8 to fill out the low-end, and will do the meassurements following your procedure for that.

But where to go from here;

1. Could the difference left/right come from the desk and some equipment being mounted on one side. If so, I can consider mounting the interface etc under the desk. Or I could make a backplate for the desk with some trapping?

2. Do the meassurements suggest where in the room I should try more trapping/panels? I have more of the panels I already used on the side and as cloud.
I could also remove the cloud and do meassurements without it if that would be of any help.

3. What would be a good starting point for subwoofer-placement, and would you recommend using the 85Hz crossover on the sub? (You actually have/had a similar setup right?)

I really appreciate any help I could get, and although this is not a professional studio, I want the room to sound as good as possible.
Most of my mixes are of our own band (and a lot of competitions on puremix etc), but as I get better at mixing it would be great to offer entry-level recording for local bands wanting to make demos etc.

-Stein_R

Alright; I haven't heard back but went ahead with som new measurements after all.
I also discovered i had a faulty XLR going to the right speaker, so it dropped in sound from time to time. This is now replaced.

I also added a couple of soundpanels more to the room, but please do answer the questions from my previous post when you have the time.

I followed the instructions to calibrate REW before the new measurements.

The new measurements can be found here: https://www.dropbox.com/s/jgtzuc16iwyx9 ... .mdat?dl=0


-Stein_R