Help with Planning & Building of my Recording Studio

Just wanted to post a status update. I've been pretty busy these past few weeks so the studio planning had been put aside for a bit. I'm just getting back into it now and trying to finish the plans on Sketchup. It's taking a bit longer than expected but I'm sure that's not uncommon haha. Trying to finalize the layout of the studio I had a quick question regarding the design of my control room. Looking at the pictures I attached at the beginning of the thread there's a sample plan for the layout of my studio. Note that the attached version is just a sample and I know it needs a lot of work but the location/orientation of the rooms will likely stay the same. Now if you look at the control room, in the outer leaf wall there's a 4'x4' window. I really really want to keep that window and have it be functional as well but I'm wondering if that's possible or not. The goal is to build a floating concrete slab and frame walls for the CR on top of it. Based on previous replies from Stuart, I should be able to use my existing ceiling by decoupling it with Hat Channel and clips. All other walls will be floated on top of the slab. I'm wondering what I should be doing and how to build the wall that will be in front of the outer wall with the window in it. I'm hoping something can be done to keep the window as is. Worst case scenario, I suppose I can just frame the wall without the window?

It's taking a bit longer than expected but I'm sure that's not uncommon haha.

:thu: But it also means you are doing it right. If it were going fast, then you'd almost certainly be doing it WRONG! Take your time, and do it completely, and in detail. That's the only sane way to design a studio!

I really really want to keep that window and have it be functional as well but I'm wondering if that's possible or not.

First question: Why do you want an operable window in a studio? Air movement will be handled by your HVAC system, not by a window that opens. In fact, having just one window that opens is not going to move any air at all! Second question: How much isolation do you need? An operable window is a weak point for isolation, and since isolation is only as good as the weakest point, you would be placing a limit on how much isolation you can get, if you install an operable window. Not to mention the minor detail that as soon s you open the window, you then have ZERO isolation....

The goal is to build a floating concrete slab and frame walls for the CR on top of it

... and that implies that you need a LOT of isolation! That's the only reason why you'd take that approach. It also implies that you have a very decent budget. Which brings us back to the question: Do you really want to trash your major investment in a floating concrete slab, by putting in an operable window?

Based on previous replies from Stuart, I should be able to use my existing ceiling by decoupling it with Hat Channel and clips.

... assuming that you have enough mass up there, and a large enough air gap, and enough damping, to match the isolation that you'll get from your expensive floated slab.... all of which would be negated if you put in an operable window...

I'm hoping something can be done to keep the window as is.

You can have windows in your room, provided that they are not operable, and provided that they are designed properly, and provided that they are not in the way of any point in the room that would need treatment. - Stuart -

But it also means you are doing it right. If it were going fast, then you'd almost certainly be doing it WRONG! Take your time, and do it completely, and in detail. That's the only sane way to design a studio!

I'll admit I was quite shocked at all this information I found about building a studio. I figured a few walls a bit more drywall and we're good! haha Anyways, yes I've just accepted that this will take a lot more time than I had hoped for but that's fine, I don't plan on going anywhere and this will just be better for costs as they don't need to happen at once...it'll be a progressive build! hehe

First question: Why do you want an operable window in a studio? Air movement will be handled by your HVAC system, not by a window that opens. In fact, having just one window that opens is not going to move any air at all!

It's not for air movement and I guess it's not so much about it being operable but a lot about having the natural light. Could I seal it, leave it as is and then put in another "special" one in the inner wall?

Second question: How much isolation do you need? An operable window is a weak point for isolation, and since isolation is only as good as the weakest point, you would be placing a limit on how much isolation you can get, if you install an operable window. Not to mention the minor detail that as soon s you open the window, you then have ZERO isolation....

Well...isolation has to be good 40db+ if possible from the rest of the studio but for the outside world...I couldn't care less. I was thinking if I was to frame my inner leaf window frame as close as possible to my outer leaf frame without touching of course and putting some sort special rubber seal in-between both frames. Gah..I guess i'm dreaming thinking this might work? haha too bad because that wall is facing and outside wall and doesn't face the rest of the studio.

... and that implies that you need a LOT of isolation! That's the only reason why you'd take that approach. It also implies that you have a very decent budget. Which brings us back to the question: Do you really want to trash your major investment in a floating concrete slab, by putting in an operable window?

Yeah I see where you're going with this. I just hope I can just seal it and leave it as is and possibly just put another thick glass in my inner leaf wall. I can build all the custom frames so that's not a problem. Again I only care about isolation in the CR, not the outside world, so I'm hoping I can just build a custom frame/window for the CR.

... assuming that you have enough mass up there, and a large enough air gap, and enough damping, to match the isolation that you'll get from your expensive floated slab.... all of which would be negated if you put in an operable window...

The clips will be fasten to 1x3 furring strips which gives a 3/4" gap + clips + hat channel and then I was going to do 2 layers of 5/8" with GG. I'd say the air gap between the enermax panels (seen in the pics in my first few posts) and the drywall would be around 2" to 2.5".

I'll admit I was quite shocked at all this information I found about building a studio. I figured a few walls a bit more drywall and we're good! haha

Yep! It's an eye-opener, isn't it? It gets your attention, for sure. If only sound would behave the way we expect it too, intuitively, instead of the way it really does!!! Darn those rules of physics... :)

It's not for air movement and I guess it's not so much about it being operable but a lot about having the natural light.

Cool! Then it should not be a problem. As long as you have it all sealed up, 100% air-tight, and also that there's enough mass in the glass (thick enough), then you can do that.

Could I seal it, leave it as is and then put in another "special" one in the inner wall?

:thu: Exactly. Both panes (the existing outer one, and the new inner one) need to have some decent mass (thickness), so you might need to replace the glass on the existing one with thicker stuff when you seal it up, but apart from that, you have the right idea.

Well...isolation has to be good 40db+ if possible from the rest of the studio but for the outside world...I couldn't care less.

It would be nice if it were possible to separate those two, but in reality they are closely related, not independent. Think of it this way: If you have poor isolation from the CR to the outside world, and poor isolation from the LR to the outside world, then any sound getting OUT of one room through the poor isolation will also be able to get back IN to the other room through the poor isolation.... Ooops! :) In other words, in order to have good isolation between the rooms, you also must necessarily have good isolation to the outside world. 40 dB isn't that much, by the way. A typical house wall (drywall on either side of 2x4 studs) will get you around 30 dB. And 40 dB isolation means that somebody singing or playing a quiet musical instrument (eg, acoustic guitar) would be clearly audible in the other room. An acoustic guitar can hit around 90 dBC fairly easily, so with 40 dB of isolation, that would be heard at around 50 dBC in the other room.... I'd suggest that you need a lot more than 40 dB isolation. Probably over 50 dB, maybe even shoot for 60.

I was thinking if I was to frame my inner leaf window frame as close as possible to my outer leaf frame

That would be a bad idea! You want your inner leaf as far away as possible form the outer leaf, at all points, not as close as possible! That's the only way you can tune the MSM resonance low enough to get good isolation at low frequencies...

and putting some sort special rubber seal in-between both frames.

... which would probably COUPLE the two frames together, instead of decoupling them, which is what you should be trying to do!

Again I only care about isolation in the CR, not the outside world,

Again, they are inseparable. That's sort of like saying: "I only care about how wet my elbow gets when I'm submerged naked in the swimming pool. I don't care about the rest of me." In reality, ALL of you will be wet: you can't get your elbows wet without also getting the rest of you just as wet. It all goes together. . . .

The clips will be fasten to 1x3 furring strips which gives a 3/4" gap + clips + hat channel and then I was going to do 2 layers of 5/8" with GG.

Immmm... you must have misunderstood something I said... Like that, you'd have a very thin air gap and thus a very high MSM resonant frequency, and thus lousy isolation in the low end of the spectrum.... You need a LARGE air gap, at lest 4" (more if you want good isolation). - Stuart -

Exactly. Both panes (the existing outer one, and the new inner one) need to have some decent mass (thickness), so you might need to replace the glass on the existing one with thicker stuff when you seal it up, but apart from that, you have the right idea.

I think the window thickness might okay/decent as is. I noticed it's not a double pane window with an air gap. It seems to be just two windows with a glaze/film in the middle but I would think this would act as a single leaf window?

40 dB isn't that much, by the way. A typical house wall (drywall on either side of 2x4 studs) will get you around 30 dB. And 40 dB isolation means that somebody singing or playing a quiet musical instrument (eg, acoustic guitar) would be clearly audible in the other room. An acoustic guitar can hit around 90 dBC fairly easily, so with 40 dB of isolation, that would be heard at around 50 dBC in the other room.... I'd suggest that you need a lot more than 40 dB isolation. Probably over 50 dB, maybe even shoot for 60.

Right! Sorry, I forgot 40db was what I could achieve with my floor as is....I'm sure it would be a lot better with a floating slab.

Immmm... you must have misunderstood something I said... Like that, you'd have a very thin air gap and thus a very high MSM resonant frequency, and thus lousy isolation in the low end of the spectrum.... You need a LARGE air gap, at lest 4" (more if you want good isolation).

Yep I'm confused again hahaha. First, would the mass I'm proposing be okay for ceiling (2 x 5/8"). Second for the air gap, I'm not sure how would I be able to get 4" gap in between my existing ceiling and drywall, unless I use some special ISO hangers? I'm starting to think a new ceiling on top of my floating walls wouldn't be that big of deal as 2x4 are cheaper than specialty brackets and I believe it would also be best for isolation.. I think I would be going this route instead now that I'm sold on the idea of a floating slab. UPDATED..... Another thing I'm thinking about is knowing what your thoughts are about potentially only floating a concrete slab for the CR. The only reason I ask is simply because if my architects/engineers come back with bad news in that I can't float all individual slabs without some major reinforce work to be done, I'm trying to put together a few other options. A Plan B sort of thing. I think the CR is the most important room for me isolation wise so if I can float just 1 slab for the control room and have 50-60db isolation I'd be content with that. For the other rooms I thought I could do a damped deck style floor and can focus more on having a good layout and acoustic treatment.

Alright, I've got yet again another question relating to floor isolation. I'm still waiting to hear back from my architect/engineer with the right numbers so in the meantime as stated in my previous post, I'm trying to figure out other options. The implicated troubles and associates costs in attempting to float a concrete floor might be too much. I guess this is why they call this the "Planing Stage" haha. Anyways, I've been looking at other options for isolating my floor and I thinking that my worst case scenario is I would be going with a "damped deck" style floor. I believe this could at least give me some extra isolation and would really help with flanking noise. Even with this type of floor the weight will be pretty high. I've estimated that this entire floor would be approx. 5000lbs. This is just the floor alone, I still need to calculate the weight of the walls, window, doors. So looking at the materials required for the suggested damped deck. I know it's asking for OC 703 semi rigid insulation. Unfortunately this type of insulation isn't that available around here and I'm looking at this following product. I was wondering if based on the specs this would be a suitable replacement for the OC 703. http://www.roxul.com/products/comfortboard-110/

I also wanted to mention that I've just donated some funds to this site to show my appreciation for all of the help around here. Cheers!

Alright, so it's obvious I knew this was coming but it's been confirmed that my current structure/floor cannot support a floating concrete slab. That being said, I know it's not impossible as I do have options to install a steel support beam with a few posts and that would get me what I need to go the concrete route, BUT....I've decided I'm not going to go down that path after all because there are other things I'd like to spend my money on with this studio build. I'll just accept the situation and move forward. I went back to my architect and asked if I could at least go with a damped deck style floor and will wait until he gets back to me. I don't think it'll be a problem but will make sure. The composition I understand is 2 x layers of 3/4" MDF with GG...on top of OC 703 or equivalent. Other than this Glenn recommended damped deck option...are there any other known decent options that I could compare with?

it's been confirmed that my current structure/floor cannot support a floating concrete slab.

That's unfortunate, but not unexpected.

I do have options to install a steel support beam with a few posts and that would get me what I need to go the concrete route

Expensive, but workable. That's the real solution IF you need very high isolation, which you seem to do.

The composition I understand is 2 x layers of 3/4" MDF with GG...on top of OC 703 or equivalent.

I would suggest one layer of plywood and one of MDF, with GG if you wish. As long as you understand that this is not going to be as good as a proper floated floor, and that there will be some transmission of sound in both directions, then this is a possible alternative. - Stuart -

That's unfortunate, but not unexpected.

Yeah that's for sure but I'm okay with it.

Expensive, but workable. That's the real solution IF you need very high isolation, which you seem to do.

The main reason why I'm not proceeding with a floated slab is simply because I feel as it would be a lot of money invested for too small of an area. That being said, I'm planning to build a big garage in the near future behind my property. I've decided that when that time comes (5-10 years), I will likely just make the building bigger and incorporate/move my studio there. With all of this new knowledge I will just build it perfect from the start with individually floated slab. Then I can set my isolation goals much higher then but for now, I will take what I can get and manage the loudness. I still believe I can build something half-decent isolation wise and great sounding.

I would suggest one layer of plywood and one of MDF, with GG if you wish.

Would laying down an additional 3/4" MDF directly on my sub-floor with GG, under the deck help a little bit?

As long as you understand that this is not going to be as good as a proper floated floor, and that there will be some transmission of sound in both directions, then this is a possible alternative.

Yes, I do understand. From this point on I'm just going to do the best I can to get the max out of my current floor and live with that. Again, I'm not always going to be playing at 120db level so I think isolation of low frequencies can be managed. Alright back to having questions..... :? 1) Going with the damped deck idea, would anyone have any other suggestions with respects to isolating my shitty :cen: floor? Anything else I can add that can help a little. 2) I'm wondering if I should i even bother with trying to build a room within a room now since I know I can't expect high levels of isolation. I should still build double studded partition walls right? I just need to confirm that my original idea for wall and ceiling composition is valid and not a total waste of money haha. I know I've been saying this for a while but I'm AM almost done with my sketchup plans. I may have gotten overboard with the drawing hahaha. it's fun!! Again, thanks for your patience and time! Cheers, Francis

Hey all, just wanted to write a quick little update on my planning. Things have been really really slow with this project but the good part is that at least I'm moving forward a little bit each time I post and plus I figure it's a good thing to document the progress on here. Most of my focus and time has been aimed at planning. I've stopped building things and am reading and researching more. I've read A LOT of threads and I'd say 95% of the people here who have the same structural properties as I do have either given up on their projects or just never bothered to come back to share progress and/or final results. I'm committed to doing things the best I can within the limits/boundaries I've got. I finally got the "official" numbers back from the engineer and my current constructed "timber" floor is able support 33psf dead load. Except for the floating concrete slab, he gave me the green light to build with the composition I had originally planned. Floors - Dampened Deck (1x 3/4" MDF, 1x 3/4 OSB", 2" Rigid Isolation) Walls - Double Stud Walls (2x 5/8" Type-X Drywall, Green Glue) Ceilings - Hat Channel, Sound Clips, 2 x 5/8" Type-X Drywall, Green Glue Now that I have that information confirmed, I'm going work on a floor plan and layout and try my best to come up with a decent draft. That being said I'm trying to find examples of similar builds but no luck. The thing I struggle with the most right now is trying to address the fact that my room is a big triangle and I have yet seen any designs or floor plans for a large "attic type" home studio. I'd like to try and calculate/evaluate modes and figure out the best ratios but how can this be done with a room like mine versus a rectangular room? I'm also trying to determine if I should cancel out the Vocal/Amp Booth and make the CR bigger and just have a Live Room and Control Room. Any ideas or suggestions would be greatly appreciated.

Alrighty! I've finally gotten around to updating my construction plans for the studio. I know it's going to need some adjustments but this will give everyone a better view of what I'm trying to do. I'm going to delete the older ones as they're of no use anymore. As it stands the plans shows the rooms as follows: Live Room is 14' x 20' Control Room is 12' x 8.8' Iso/Vocal Booth is 6' x 8.8' The .skp file was too big so I'm sharing a link to where the file can be downloaded. https://drive.google.com/open?id=1jsJ93 ... mVH5HJj0q1 Let me know if you're having any issues. As you'll see its not a completed plan by any means. After reading more and more I've had to make a lot of changes to it but I think it's getting better each time. Right now I'm dealing with the following issues: 1) Having a hard time trying to figure out how to connect/close off the live room with the entrance of the studio. There's a little storage area to the right of the door that I want to use but doesn't need to be accessible from inside the live room. That's what I'm working on right now. 2) I'm not sure what to do with my ceilings. I originally was planing on using the existing ceiling and install sounds clips and hat channel with 2 x 5/8" drywall but at this point I'm starting to like the idea of building individual ceilings for each room. The biggest drawback I feel is the extra space I'm going to end up taking doing that but I assume the isolation would be much better. 3) Debating if I should shrink or cancel out the Iso/VocalAmp Booth to make the CR bigger. Worst case I'd be happy and fine with having just a Live Room and Control Room. Not shown is the the HVAC closet located on the left side of the door. This area is closed off but is accessible from outside the studio within another storage area Any feedback is appreciated!! In the meantime I'm going to try and add more details such as the HVAC closet and storage area as well as try and finish the area where the entrance/storage area/live room meet up. Cheers! Francis,

Since this is all new construction I'm also curious to know what you guys think of using 16" OC stud spacing for both wall and ceiling framing. I've read that using 16" OC is best for lower frequencies and that 24" OC is best for mid-high frequencies. Is that true? I've also read that in a double stud wall using 16"OC in one wall and 24"OC in the other would help? Is that true? If anyone can clear that up it would be great so that I could update my plans. I've figured out how to close off the entrance and live room. I'll update the plans shortly. Cheers!

Since this is all new construction I'm also curious to know what you guys think of using 16" OC stud spacing for both wall and ceiling framing.

That would work fine.

I've read that using 16" OC is best for lower frequencies and that 24" OC is best for mid-high frequencies. Is that true?

Not really. In general, if an isolation system works well for low frequencies, it works even better for high frequencies. There is a small advantage to using 24" instead of 16" for low frequencies. However, if you go with 24" OC, then your studs are far apart, so it becomes problematic to mount things on the walls that are less than 24" wide.

I've also read that in a double stud wall using 16"OC in one wall and 24"OC in the other would help? Is that true?

No! - Stuart -

Excellent! Thanks Stuart! I kind of figured that if you can build a system that isolates low frequencies well that it would take care of mids and highs. I'll update my plan and finish adding the individual ceilings using 16" OC

I've been reading more and more on studio designs and recommended room dimensions for studios and I'm not sure how to separate the space I have. This is still the planning stage so I guess I've got some time to figure that out. I’m trying to figure out the best ratios for the control and live room. The space I have available is 23′ wide by 26′ long. (the room has slopped ceilings 12/12 pitch...one big triangle?). Within that room I’m trying to fit a live room to track drums and other instruments as well as a control room and maybe even a tiny vocal booth. The sketchup plan I posted has the room separated as follows: - Control room dimensions are 8.8′ width, 12′ length and 12′ high at the highest point in the room. I’m wondering if that’s manageable. - Live room dimensions are 20′ wide, 14′ length and 12′ high at the highest point. - Vocal Booth dimensions are 8.8' width, 6.3ft length and approx 8' at the highest point. I'm pretty sure the Vocal Booth would have to go to give some extra space to the CR but even doing that I'm not sure if that's going to help. Having a triangle shaped room surely limits my options. Taking out the Vocal Booth I could stretch the control room to approx 10/12′ wide by 20′ length if that would be better. That would take away about 1 or 2ft off the length of the live room. Any thoughts? sorry about all the questions :/ Any help/advice would be greatly appreciated!! P.S. I can post pictures if needed. I'm getting to a point where I'd like to maybe pay someone to help me figure this stuff out for me. Any ideas as to how much $$ that would cost roughly? Cheers!

After doing some more reading on CR design I found that a decent Control Room should have a min of 200sq/ft. Is that correct? Regardless this information sort of forced me to accommodate this into my design and so I've adjusted my plan and as mentioned in my last few posts eliminated the vocal booth and stretched out the CR an extra 16". It's now approx. 123" W x 226" L x 12' H(at the peek of the roof). Doing so gives me a bit smaller Live Room 18.8' W x 12.8' x 12' (at the peek of the roof). Now I'm starting to do more and more calculations and I have a few questions: 1) After stretching out my current CR design I still only have approx. 192 sq/ft. Is this still manageable for a decent CR? or should I try to stretch even more? 2) Is having a smaller Live Room a bad thing or still manageable? I can try and stretch the CR a bit more to get me up to 200sq/ft + but I just want to make sure that won't effect the LR in a bad way. I'll post an updated plan later tonight to show the changes. Thanks, Francis, How would I be able to calculate/evaluate modes with a room with slopped ceilings. Most online tools take measurements

After doing some more reading on CR design I found that a decent Control Room should have a min of 200sq/ft. Is that correct?

Well, yes, that's correct. ... Sort of. Yes, the best specs for "critical listening rooms" do specify 200 ft2 as the "minimum", but that does not mean that if you only have 199 ft2 it will be terrible! Nor if you have 190... or 180... or 170... It's a matter of "optimal" and "slightly less than optimal" and "a little worse". A smaller room can still be pretty good... PROVIDED THAT it is designed carefully and treated accordingly. I can design you a 200 ft2 room that sounds terrible, and I can design you a 160 ft2 room that sounds pretty darn good. John has built rooms inside shipping containers! It just gets harder and harder to do as the room gets smaller. Yes, bigger is better, for sure, and yes, above 200 ft2 is best (actually, the number is 215.3, because it is specified as 20 square meters....), but your room won't automatically fail if it is smaller.

so I've adjusted my plan and as mentioned in my last few posts eliminated the vocal booth and stretched out the CR an extra 16". It's now approx. 123" W x 226" L x 12' H(at the peek of the roof).

That's a good size for a room, but did you check the "room ratio" to make sure it is acceptable? Use one of these Room Ratio calculators to figure out the best dimensions for your room: http://www.bobgolds.com/Mode/RoomModes.htm http://amroc.andymel.eu/ Both of those are very good, and will help you to decide how best to build your room. They give you tons of information that is really useful to help figure out the best dimensions. Warning! You do NOT need to go crazy here, adjusting dimensions to get a "perfect" ratio! There is no such thing. As long as your ratio is not close to one of the "bad" ones, and is reasonably close to one of the good ones, then that's fine. It is more important to have as much volume as possible in the room, than it is to hit the "best" ratio.

Doing so gives me a bit smaller Live Room 18.8' W x 12.8' x 12' (at the peek of the roof).

Do be aware that the air volume of the LR should be somewhat larger than the air volume of the CR, if possible. One way of looking at it (not strictly accurate, but it helps to get a mental picture), is that you need to hear the "reverb tails" of the LR when you listen on the speakers in the CR. Reverb tails are the lingering remnants of the sound dying away slowly after the cause has stopped: it's the sound of the room itself, to a certain extent, or the sound of how the music reacts with that room, after the music stops. It's the "life" and "character" of the room, what makes it "sound great" for a musician. But it is low level, and dies away at a rate that is proportional to the room volume. Smaller rooms have faster decay. So here's the thing: the decay in your CR will be "neutral": just right for the room itself. You will tune it that way, because control rooms MUST be neutral: They must not add to nor subtract from the natural direct sound. So if it turns out that the reverb tails in your LR are about the same length as the natural decay time of the CR, you won't hear the reverb tails! When you listen on your control room speakers, you'll hear the natural decay of the CONTROL ROOM, since it will be louder than the reverb tails from the LR in your recording. The tails in the LR need to be substantially longer than the decay time of the CR, so that you can hear those reverb tails in the CR, after the natural decay has already gone by... and you are left hearing the sound of the LR. If your rooms are about the same size, then you'll be challenged to hear what the music really sounds like in the LR, as you listen in the CR.... but the guy listening to your mixes on ear buds, where there is no room at all and zero decay time, will hear everything! Including stuff that you never heard in your mixes... So the ideal is to have the LR larger than the CR, and if you can't do that, then make the LR slightly more "live" (longer tails) and the CR slightly more dead (shorter decay time), by using the correct treatment in both rooms.

1) After stretching out my current CR design I still only have approx. 192 sq/ft. Is this still manageable for a decent CR? or should I try to stretch even more?

That's fine! As I mentioned above, 200 ft2 is not a sharp cut-off point: it's just a rough marker that shows where performance starts to tail off for smaller rooms. Think of it sort of like the "roll off" in bass response for a good speaker: The speaker spec might say that it goes down to 35 Hz, but that doesn't mean that it produces no sound at all at 34 Hz! It just means that at 34 Hz, the sound is a tiny fraction less than it should be, optimally. And at 33 Hz, it's a little less optimal. Even at 30 Hz, and 25 Hz, the speaker is still putting out some sound. The 35 Hz spec just shows the point where things START deteriorating: It's not a sharp line. Ditto for the 200 ft2 "spec": it's just a rough point where things start rolling off.

2) Is having a smaller Live Room a bad thing or still manageable?

See above: As long as it as larger VOLUME of air than the CR, that's fine. And you can also adjust the treatment of both rooms a little, pushing the LR a bit more to the liver / longer tails side, and damping the CR a little more than it should be. In some design concepts for control rooms, there's the concept of the ITDG, or Initial Time Delay Gap. That's the small period of time between the instant where your ears hear the direct sound from the speaker, and then hear the first "echo" of that direct sound, that has bounced off some wall somewhere, and come back to your ears. The specs for control rooms often say that the first "reflected" sound should not arrive until at least 20ms after the direct sound, and that when it DOES arrive at your ears, it should be diffuse (not specular), and during that time, the intensity should be at least 20 dB lower than that direct sound. That "20 ms window" is the ITDG. After than time has passed, some specs call for the level to increase again, above -20 dB, then die away slowly. So if you look at a graph showing how the room responds to an "impulse" (a sudden very loud, very short sound, such as a balloon popping), you'll see a tall spike as you hear the direct sound of the pop itself, then nothing for 20ms (or at least, nothing louder than -20db), then you'll start to see the level rise again as the diffuse sound of the balloon pop that has bounced around the room and been absorber and diffused, starts to get back to your ears, at maybe -15 dB or so, but then it dies away slowly for a few hundred milliseconds, until it is completely gone. That "space" where you hear "nothing" after the initial direct sound, is the ITDG: The Initial Time Delay Gap between the direct sound hitting your ears, and the reverberant field hitting your ears. So, the ITDG has to be long enough to allow you to hear the sound of the LIVE ROOM reverberant field, which hopefully does not have an ITDG, or has a short ITDG, or one that does not go below -20 dB. As long as you have that condition, then you will be able to hear the "sound" of the live room when you listen on the CR speakers. But if your CR has an ITDG that is too short, or too loud (above -20dB), or if the level rises up too high again after the ITDG, then you won't hear those small hints from the LR room sound, in the CR. In that case, it is better to not have a rise above -20 dB after the ITDG: just keep the level low, say -30 dB for the ITDG, don't allow it to rise again above that, then the decay can start after that, at a lower level. That's what I do for small control rooms and small live rooms. It's not easy to get it right, but it does give you a better shot at hearing the subtle delicacies of the LR reverb tail, in the CR. OK, so some people think this is splitting hairs, since LR tails are low level and subtle in any case, so there's no point in caring about them much. They don't think that "tails" are important at all. Maybe if you only ever plan to record shrieking grunge rock, or mind-mashing heavy metal genres, that scream through the entire song at 120 dB without it ever being possible to have the slightest hint of a reverb tail, then that's OK. But if you plan to record music that has a bit of feeling to it, with subtleties, nuance, ambiance, then this is very important. (And if you only ever plan to record screeching, howling, wailing, bellowing heavy metal, then why bother with a studio at all?? You could record that in a subway station, and not even notice the trains roaring past . . .:) ).

I can try and stretch the CR a bit more to get me up to 200sq/ft + but I just want to make sure that won't effect the LR in a bad way.

Not necessary. At 190 ft2, you are within the ball park for having a decent control room. Yes, bigger would theoretically allow slightly better, but the difference is not huge, and 190 is still good.

How would I be able to calculate/evaluate modes with a room with slopped ceilings.

Simple answer: you can't! Room mode calculators only work for perfectly rectangular rooms. More complete answer: You can still use the calculators to get a good idea of how the room will behave, as long as the angle is not too great, and as long as you understand what you are looking at. For example, if it is JUST the ceiling that is off, and your walls are still parallel and perpendicular, then the predictions for axial modes in the length and width directions will still be perfectly correct, and so will the predictions for tangential modes that only involve the four walls. But axial mode predictions related to the ceiling will NOT be correct, and neither will predictions for tangential modes that involve the ceiling, or any oblique modes. However, if only part of the ceiling is sloped (eg, the front half rises, but the rear half is flat), then the predictions will still be valid for the part of the room where the ceiling is not sloped. And it the angle of slope is not huge, then the predictions will not be far off, and you can still use them, as long as you realize that they won't be entirely accurate. The big issue happens when you have a room that has more than six sides, or when the splay angles on the walls and ceiling are large. The more complex the room is, and the further it is from being a pure rectangle, the less accurate the prediction will be. Having said all that, you do NOT need to go crazy trying to find the perfect ratio for your room! There is no such thing anyway, and it doesn't really matter all that much, as long as you stay away from the bad ratios. So for example, if you have to reduce the length of your room by 6" to get a good ratio, then don't do it! It's better to have that extra six inches to increase the room volume. The only time I'd do that is if the room was a perfect cube, and the only way I could fix it was by reducing the length or width a bit. And even then, if it was a very small room, I would be very hesitant to take off those 6". For a large room, it would not be a problem to lose 6"... but then again, for a large room there would be no need to lose 6" anyway, since large rooms already have better acoustics than small rooms! :) - Stuart -

As always thanks for your prompt response Stuart! Hope you had a great xmas!!

That's a good size for a room, but did you check the "room ratio" to make sure it is acceptable? Use one of these Room Ratio calculators to figure out the best dimensions for your room.

This is good news for sure because I was starting to have doubts. I certainly want to try to design the CR as best as possible. About the room ratio calculator, I just want to confirm based on the information you provided. I've attached a sample picture of the sketchup plan and as you can see the ceilings are slopped at 45 degrees (12/12 pitch) but there are no additional angles. I suppose you can say that there are a total of 6 sides. So to recap: 1) In my case the room mode calculator will only work and predict axial modes in length and width directions as well as tangential modes for the four walls. Correct? 2) Based on the attached picture it doesn't seem like the tool would work because of the small amount of the front and rear wall will be flat. Correct?

The big issue happens when you have a room that has more than six sides, or when the splay angles on the walls and ceiling are large.

From looking at the attached image, would you consider this a "complex" room? It will have a total of 6 sides but obviously the angle of the ceilings is pretty big. 3) On the bright side I suppose I can use the wasted space in the back of the CR for bass-trapping even though it wouldn't go all the way up to the ceiling? Because of the slopped ceiling if I was to walk to the back of the room until my head would hit the ceiling/wall I'd have about 5-6 feet of wasted space I can't use other than for storage or most probably some sort of absorption/treatment. 4) I'll be honest and say that I haven't done enough research to fully understand the data I'm looking at when using the Room Mode Calculators but from what I understand, it seems I shouldn't waste too much time trying to get that perfect ratio since it can most likely be treated afterwards. Correct? Regardless I will read through Rod's book again and try to make sense of Modes and what to watch out for. For the most part I think the current size/layout will be okay. With the dimensions I've currently designed this is information that was returned from the tool: ------------------------------------------------------------------------------------- Room Dimensions: Length=18.82 ft, Width=10.25 ft, Height=12 ft Room Ratio: 1 : 1.17 : 1.83 R. Walker BBC 1996: - 1.1w / h < l / h < ((4.5w / h) - 4): Fail - l < 3h & w < 3h: Pass - no integer multiple within 5%: Pass Nearest Known Ratio: - "24) A worst case scenario calculated by RPG" 1 : 1.075 : 1.868 RT60 (IEC/AEC N 12-A standard): 234 ms - ±50ms from 200Hz to 3.5kHz = 184 to 284ms - ±100ms above 3.5kHz = 134 to 334ms - <+300ms at 63hz = 534ms - 300<RT60<600ms RT60 (ITU/EBU Control Room Recommended): 217 ms - ±50ms from 200Hz to 4kHz = 167 to 267ms - <+300ms at 63hz = 517ms - 200<RT60<400ms Absorbtion to achieve ITU RT60: 522 sabins Volume: 2316 ft^3 Surface Area Total: 1082 ft^2 Surface Area Floor: 193 ft^2 Surface Area Ceiling+Floor: 386 ft^2 Surface Area Front Wall: 123 ft^2 Surface Area Front and Rear Wall: 246 ft^2 Surface Area Left Wall: 225 ft^2 Surface Area Left and Right Wall: 450 ft^2 Surface Area 4 Walls: 696 ft^2 Surface Area 4 Walls + floor: 889 ft^2 (sabins - front wall - carpet) / Left+Right+Rear wall: 35 % (sabins - front wall) / Left+Right+Rear wall: 69 % Schroeder Fc: 108hz Frequency Regions: - No modal boost: 1hz to 30hz - Room Modes dominate: 30hz to 108hz - Diffraction and Diffusion dominate: 108hz to 432hz - Specular reflections and ray accoustics prevail: 432hz to 20000hz Count (30-193hz) : Axials=13, Tangentials=54, Obliques=72 Count (30-100hz) : Axials=6, Tangentials=6, Obliques=2 Critical Distance (direct = reverberant field): 14.60ft ---------------------------------------------------------------------------------------------------------------------- Back to reading Rod's Book! Once I get some sort of confirmation on my dimensions and layout I'll update my plan and start looking at HVAC silencer boxes, supply and return locations. Again, thanks for all your help! And please let me know if you'd like to see additional angles or screenshots of the plan. Happy New Years everyone! :) Cheers!!

About the room ratio calculator, I just want to confirm based on the information you provided. I've attached a sample picture of the sketchup plan and as you can see the ceilings are slopped at 45 degrees (12/12 pitch) but there are no additional angles. I suppose you can say that there are a total of 6 sides

Ooops! Room mode calculators are not applicable here, except for the length axial mode, and perhaps slightly for the width.

1) In my case the room mode calculator will only work and predict axial modes in length and width directions as well as tangential modes for the four walls. Correct?

Length yes, width... not so much. Only to a limited extent, since most of the side "walls" is steeply angled. There's only a small part that is vertical.

From looking at the attached image, would you consider this a "complex" room?

Yep! :)

3) On the bright side I suppose I can use the wasted space in the back of the CR for bass-trapping even though it wouldn't go all the way up to the ceiling?

I think we are talking about "front / back" and "sides" in different senses here! For me, the best way to lay out a control room in that space, would be to face the window. So the "front" would be the window, the "back" would be the door, and the "sides" would be the deeply sloped ceiling.

4) I'll be honest and say that I haven't done enough research to fully understand the data I'm looking at when using the Room Mode Calculators but from what I understand, it seems I shouldn't waste too much time trying to get that perfect ratio since it can most likely be treated afterwards. Correct?

Right! Especially with that shaped room, where the calculator isn't going to help too much anyway. - Stuart -

Ooops! Room mode calculators are not applicable here, except for the length axial mode, and perhaps slightly for the width.

Ok! Understood!

Length yes, width... not so much. Only to a limited extent, since most of the side "walls" is steeply angled. There's only a small part that is vertical.

Ok!

Yep! :)

Ok that's too bad but I guess I expected that. lol

I think we are talking about "front / back" and "sides" in different senses here! For me, the best way to lay out a control room in that space, would be to face the window. So the "front" would be the window, the "back" would be the door, and the "sides" would be the deeply sloped ceiling.

Oh! Ok..this changes things a bit haha. This is great feedback! Curious to know based on your answer, if it's better to have more width then length for listening position? I was hoping to be able to look in the Live Room while working in Control Room but if you're saying it would best to face the window for the mixing/listening position I won't question it and I will switch it up. If that's the case I think I will swap the door and window within the wall facing the live room so that the window would be more in the center of the room and have the door at one of the ends. I would like to add some more details to the HVAC design and wanted to confirm if I can possibly put the silencer boxes in between walls. Looking at the last CR picture I posted, you can see (left) there's some space in between in the inner and outer leaf walls. I would like to put the supply boxes there and have the return boxes in between the CR and the LR. I don't see why not as long as the boxes don't interconnect the two walls in any way correct? I'm also wondering since I have approx 12-16" of space between the outer and inner wall, if I could/should soffit mount my monitors in there(TBD). There's alot of room in there can would be wasted otherwise so anything I can do to use up that space would be nice. I was originally thinking of building a recessed space for an effect rack in the wall. I can't say enough how much I appreciate your help. Stuart! Thanks again for dealing with all our questions!

Curious to know based on your answer, if it's better to have more width then length for listening position?

Usually it is, indeed, better to have the speakers facing the long way down the room, to have as much distance as possible between the front and back walls. But in your case, it's a very different situation. It makes more sense to have flat walls at the front and rear, with the angles on the sides. This means that you'll need a ton of treatment on the rear wall, but that's a given anyway: you'll need some extra, and it will be more complex to do it, due to the ceiling angles, but it's the best compromise. acoustically.

I was hoping to be able to look in the Live Room while working in Control Room

You could do that too: flip it 180°, put the doors in the center of that wall, and make them sliding glass doors, or swing doors with lots of glass, so you can see into the other room. That would be fine.

If that's the case I think I will swap the door and window within the wall facing the live room so that the window would be more in the center of the room and have the door at one of the ends.

As I mentioned in the paragraph above, I would do that as a single combined "door-window" Either a large hinged door with plenty of glass in it, or a sliding glass door.

I would like to add some more details to the HVAC design and wanted to confirm if I can possibly put the silencer boxes in between walls.

You can, provided that you have enough space there! Silencer boxes are large: The "thinnest" one I've ever designed was still 11 inches thick, so you'd need a wall caity at least that big, plus some extra space on each side...

since I have approx 12-16" of space between the outer and inner wall, if I could/should soffit mount my monitors in there(TBD).

Not really. Your speakers are still located within the inner-leaf of the room, even though you then add the baffle in front. You cannot have the rear end of the speaker inside the wall cavity, as it would not be isolated at all.

I was originally thinking of building a recessed space for an effect rack in the wall.

If you do flip the room so that you are facing the CR directly, then that would be your rear wall, so you could use that extra space for bass trapping. You'd need to do some fancy framing for that, for your inner-leaf, with a "kink" near the floor, but 16" is too good to waste! That would be excellent for bass trapping. - Stuart -

Usually it is, indeed, better to have the speakers facing the long way down the room, to have as much distance as possible between the front and back walls. But in your case, it's a very different situation. It makes more sense to have flat walls at the front and rear, with the angles on the sides. This means that you'll need a ton of treatment on the rear wall, but that's a given anyway: you'll need some extra, and it will be more complex to do it, due to the ceiling angles, but it's the best compromise. acoustically.

Right, of course, I had forgotten about the fact that the speakers need to be angled towards to the listening position and in my case flipping the layout as you mentioned makes much more sense. As for the "tons of treatment" required on the back wall, if I do rotate 180 degrees, I'll make sure to use the 12-14" worth of space in between the outer and inner wall for that. I'm just curious now, what if I don't flip and just go with your original proposal, I would probably need to build another frame in front of my back wall for all that extra treatment and absorption correct? And the thicker the better? I'm just thinking I might be best to flip and make use of that space. I'm running the main supply trunc of my air handler in that space. You can see it in my previous picture. It's wrapped in 4" of green mineral insulation.

You could do that too: flip it 180°, put the doors in the center of that wall, and make them sliding glass doors, or swing doors with lots of glass, so you can see into the other room. That would be fine.

This would be great for sure! Question thought, I'm just wondering doesn't my listening position need to be in the middle of the room? I suppose having my desk a little offset from the middle is not a big deal?

I would do that as a single combined "door-window" Either a large hinged door with plenty of glass in it, or a sliding glass door.

As for the doors, I was going to go for two separate solid core doors instead of just one massive one. I guess based on what you're saying I'd get better isolation by not having two separate openings and combining the two together correct? I was hoping to have the window in front and above my mixing position but if it's best to just combine the door and window I'll just accept and live with it.

You can, provided that you have enough space there! Silencer boxes are large: The "thinnest" one I've ever designed was still 11 inches thick, so you'd need a wall cavity at least that big, plus some extra space on each side...

11" inches is doable. I have 12" on the plan right now but can space it a little more to accommodate. I was planning on having approx 16" in between the CR and LR walls so there would be plenty of space there I think. Could I not just fasten the boxes on my outer or inner leaf wall? Another quick question about Supply and Return vents. I've read that it's best to have the supply at the top of the walls or in the ceilings, what about the returns? Would the same apply there? Trying to figure it all out. I'll run mostly flex insulated 6" duct from the main truncs in between the walls.Worst case I might even be able to run the flex above the ceilings hanging from the outer leaf.

Not really. Your speakers are still located within the inner-leaf of the room, even though you then add the baffle in front. You cannot have the rear end of the speaker inside the wall cavity, as it would not be isolated at all.

Alright so I guess that means I'm stuck with having my monitors on stands correct?

If you do flip the room so that you are facing the CR directly, then that would be your rear wall, so you could use that extra space for bass trapping. You'd need to do some fancy framing for that, for your inner-leaf, with a "kink" near the floor, but 16" is too good to waste! That would be excellent for bass trapping.

I'm pretty sure this is what I will be doing. I get what you're saying with the kink near the floor for bass trapping. I'm just wondering if having my HVAC supply trunc running on the floor is an issue. The trunc is approx 10" high and sitting on 4" of insulation so it's approx. 14" off the floor. Can I still do bass trapping at that height with some fancy framing or doe the bass trapping need to be done right off the floor? Cheers!!

When do you think you'll start construction?

Long story short, I had previously started framing walls but after having a few replies from Stuart, I realized I really wasn't doing things right so I took a big step back and started doing more and more research and decided I was going to hold off on the build until I was 100% sure of the design. I'm really hoping to to start construction within the next couple of months but before that happens I'm going to make sure I get the thumbs up from Stuart. I'm still trying to finalize my Sketchup plan and I think I'm getting there but there are still some details I need to address. Honestly, Stuart has been the key contributor for my design. I cannot say enough about much I appreciate his help and most of all his patience dealing with all my questions. Baby steps :) I'll make sure to post all progress pictures once I get started