Starting Over - New Small Control Room Design

First I want to say thanks to all that have participated in building this information rich forum. Oververiew: I created a post a few months ago and tried to make sure I followed the outline, but still have had no comments on that post. I am actually glad as I went back to the posting outline and did as suggested and searched for all available topics and spent time working on designs for my very small control room. I built the original control room and vocal booth about 16 years ago with little resources on how to, and not much cash. I have tried to improve the acoustics about three times and the last was the worst. I am in the middle of mixing songs for my son's band and struggling way to hard to get it where i want. I love music and audio equipment and want to improve my skills but need a better tool in the toolbox. I am very excited about this project and hope that I get some responses this time. Goals: I completely scrapped the old control room and I will be building a new slightly large one. I want to create best acoustic space for tracking mixing and occasionally mastering. I want to increase my isolation and flatten the response of the room to improve my craft as a producer/engineer. I have been in the audio industry (not as an engineer) and have turned out some good work in my home studio, even made a few bucks along the way, which of course I spent on gear. Getting my tracks to sound professional has always been a struggle and finally testing the response was a window into how bad the room really was. I plan to increase the time spent in the studio and have many projects already in the works. Previous Post: In my Previous Post I included images of the small control room and vocal booth. The dimensions were L=9'7" W=6'10" H=7'7" the height included the space filled with insulation in the above floor joists. Research since first Post: I have about 100 hours in on this site, several more on a few others, "JS Rules as you know" I read excerpts of Phillip Newels book online and a few others. Followed the history of the control room development and got very interested in Tom Hidley's designs. I think I am most influenced by John's designs and have spent a great deal of time looking at some of his skp's. I work at a design firm that does world class acoustic projects in large venues, CCI Solutions as the e commerce manager. I talked with several designers but none could offer much assistance in such a small space. I also scoured the web looking for cool designs and still come back to some of John's projects and projects listed in this forum as the best building blocks for studio design available at this time. Where I am at in the process: See the images below I need to remove the two walls today but wanted to get them into the image as they show where the room was (see floor for original wall on left side). I moved the water heater and any plumbing that would run over the room. I will be installing the studs for the outside wall in the next couple of weeks if all goes well. How loud: The main untreated live room has the windows heavily closed and insulated for jam sessions and tracking we can't get away with loud stuff past about 10pm. As for the studio I think I mix at about 80db, but I plan to get a DB meter and keep it on from now on. Details about current space: Cement floor, 9" thick basement walls on two sides. Design Concept: I believe that soffit mounting my JBL LSR4328 monitors with Johns method with hard surface on top and hangers below should help in a small space like mine. An affective rear wall design seems like a must in a small room, I have had a few in mind. Using rock wool with cloth covering and slats with 703 to help with reflections and broadband trapping. The angled slat sections will space the slats for broadband. The current design shows hangers on the rear wall with a airgap mounted 703 panel on the inside door. I had designs of splayed walls but there is just not that much space and I found many references to not worry about it in a small space. The new larger footprint of 9'31/2" wide and 11' 101/2" Construction of design. In the design below I plan to create a two leaf room. Unfortunately I need to have the door on the back wall and the side door to the vocal booth. Both leafs will have two layers of sheetrock 1/2 and I may use sheetblock in between them. The outside leaf will have studs and insulation along the basement cement walls and the ceiling will be sealed to the cement wall and the outside stud walls against the above joists. The inner leaf will be completely freestanding. The inside leaf is inside out and supports the ceiling on the walls with about 1" clearance to the outside leaf ceiling. Images: in the images below you will see where the old back wall was and the door made up the rest of that end of the control room. Questions 1: Does the plan make since and what changes would help it acoustically? Question 2: I planned to use slats on the vocal booth door and the same on the other side, is this ok or should it just be broadband absorption? Question 3: Hangers or super chucks for the back wall. Question 4: John has a few designs that would revers my design and enter between the soffit mounted monitors, any thoughts? Question 5: The soffit design, I have seen several soffit designs that have a smaller footprint on the floor than the ceiling and give the speakers a slight angle. Would that help to raise the speakers higher and not conflict with a pair of large computer screens on a small desk I have to plan for?

Hi Ducharme. A couple of comments that might be worth something:

I will be installing the studs for the outside wall in the next couple of weeks if all goes well.

I'm wondering why you need studs on your outer wall? From the diagram, you seem to have a rather thick brick or concrete wall around at least two sides of the room: Or is that large grey "L" shaped block something else? I'm just assuming that it is concrete. If it is, then you don't really need to do anything more to it, probably. Putting studs and drywall up against it won't do much for you, except eat into your budget! (If it isn't concrete, then ignore my remark...)

The main untreated live room has the windows heavily closed and insulated for jam sessions and tracking we can't get away with loud stuff past about 10pm.

What kind of instruments are you playing in there? A drum kit will put out 115 dB all by itself without much trouble. Add in a loud bass player, extreme electric guitar, etc., and you could be approaching 120 dB. Or do you play quieter instruments?

As for the studio I think I mix at about 80db, but I plan to get a DB meter and keep it on from now on.

You might be surprised at just how loud you are when you mix! I was, teh first time I measured. Your pair of JBL LSR4328's can put out 115 dB peak between them, and their sensitivity is listed at 96 dB, so you might find that you are mixing at a higher level than you imagine. 80 dB isn't all that loud for a CR. Once you get your meter, you might find that you are closer to 90 dB.

I believe that soffit mounting my JBL LSR4328 monitors with Johns method with hard surface on top and hangers below should help in a small space like mine.

Yep! I'm a fan of soffit mounting. Some others here aren't, but I think it's a great idea. However, you need the "hard surface" all around the speaker, not just "on top" of it. (I think that's what you meant to say, but its a bit ambiguous, so I'm just making sure.) The hard surface (baffle) needs to be rigid and massive (as you already know if you have been getting into Tom Hidley's designs!) and is supposed to simulate an infinite baffle. So it needs to be as large as possible. In John's designs, the hangers normally go BEHIND the lower portion of the baffle, but the baffle is still there, nearly down to the floor. Also, from your diagram it seems that your speakers are not centered in their baffles: they should be. You want roughly the same amount of "hard surface" on each side of your speaker, and it doesn't look like that from your diagram. You can move them a bit further out (towards the walls). That will also help with your stereo image. If that messes up your axis intersection point, then you can angle the soffits and speakers so that the axes still meet in the right place. I didn't measure it, but to me it seems that your ears are a bit further back than the 38% mark, and maybe close to the 50% mark? Or is that just my fading eyesight playing tricks on me again?

I need to have the door on the back wall and the side door to the vocal booth.

I don't see the rear door as being a major issue, except that it takes up the space where you could have nice comfy couch to snooze on! :) And it puts a hard reflective surface right behind the mix position, but that can be treated. However, your door to the booth might be an issue: It seems to be right at the first reflection point for your right speaker. Any chance you can move it rearward a couple of feet?

Both leafs will have two layers of sheetrock 1/2 and I may use sheetblock in between them

Save your money and forget the sheetblock: Go with 2 layers of 5/8" sheetrock instead: Mass is mass, and the sound waves really don't care how much you paid for the mass, so just put the cheapest mass in that you can get (within reason!). It doesn't come much cheaper than plain old sheetrock, and 5/8 beats 1/2.

The outside leaf will have studs and insulation along the basement cement walls

So the walls are cement! Then I don't see why you need those studs. If it is just to keep the 703 in place, then there are other, cheaper ways of doing that... :)

The inside leaf is inside out and supports the ceiling on the walls with about 1" clearance to the outside leaf ceiling.

1 inch isn't much if you need good isolation! Any chance you can get yourself a bigger air gap up there? The normal recommendation is at least 4 inches between facing inner-leaf and outer-leaf surfaces. Reducing the air gap reduces isolation. What is the existing ceiling made of ? Is that just the floor of a room above? How much isolation do you need to that room? When you say 1 inch, do you mean from the top of the sheetrock on your inside-out ceiling, up the the bottom of the joists on the floor above? If so then ignore the above comments: you are OK as your air gap is the joist space in that case, which is going to be much more than 4 inches anyway, I expect.

Question 2: I planned to use slats on the vocal booth door and the same on the other side, is this ok or should it just be broadband absorption?

If it really is at the FRP, then absorption, at least for the guilty section.

Question 3: Hangers or super chucks for the back wall.

Yes! :) John usually recommends hangers, I think. But on the other hand, superchunks are easy to build, and also work well. If you have the time, I'd go with hangers.

Question 5: The soffit design, I have seen several soffit designs that have a smaller footprint on the floor than the ceiling and give the speakers a slight angle. Would that help to raise the speakers higher and not conflict with a pair of large computer screens on a small desk I have to plan for?

Yep! You can raise your speakers if you need to, then tilt them forwards (and the entire baffle along with them), so that the acoustic axes still meet just behind your ears, which should be somewhere around the 38% mark. You can tilt them down by as much as 10 degrees (some say 15) if you need to, but watch out! You might end up creating new reflections on your desk surface if you go too high and tilt too much... Good luck with your build! - Stuart -

Stewart- Thanks so much for the quick reply.

Soundman2020 wrote:

I'm wondering why you need studs on your outer wall? From the diagram, you seem to have a rather thick brick or concrete wall around at least two sides of the room:

The L shaped gray area is the outside cement basement walls. I will save some money and use another way to go.

Soundman2020 wrote:

What kind of instruments are you playing in there?

Drums, guitar, bass for rehears/jams Drums only for tracking. I will be working on the sound and isolation in that room at some point.

Soundman2020 wrote:

Also, from your diagram it seems that your speakers are not centered in their baffles:

I was planning on the infinite baffle concept. I will center the speakers using a slight angle and shoot for the 38% listening point. In this case is the 38% point measurement from the inside leaf or from the center of the soffit wall? Based on your comment my guess is that I should measure from the center of the soffit wall.

Soundman2020 wrote:

However, your door to the booth might be an issue: It seems to be right at the first reflection point for your right speaker. Any chance you can move it rearward a couple of feet?

I am stuck with the door there so these are my choices. (1) leave the door where it is with no slats and only broadband absorption just as it would be on the other side. I had a door that had 3" of 703 cloth covered but it had some area that was not covered because of the depth of the frame attached to the old regular 24" door. If I built a door that had almost no gap and cloth covered 703 (possibly mineral wool would be more absorption) would that work or is the fact that it is a door instead of 2 layers of sheetrock and absorption? (2) Use the adjacent room past the vocal booth currently used as a bedroom but will be available in the not too distant future. This would alleviate the need for the door using a different entrance but I did have in mind using the door to get to that room either with a small booth and a drum room or all one purpose room. All will require a new project to make it work. (3) Build a small booth out in the main area, that proposal may get turned down from the building management team - my beautiful wife. Losing the door simplifies the build but having easy access to a well isolated vocal booth for voice and acoustic instruments has been a major plus. The location of the door always added to the very small size of the room though it will be bigger this time, it may be nice not having people squeezing through that small door so close to the mix position. As you can tell I am very much on the fence here, but the nod will go to the best mix position sound quality and if that means loose the door - it's gone.

Soundman2020 wrote:

Go with 2 layers of 5/8" sheetrock instead:

will do -

Soundman2020 wrote:

1 inch isn't much if you need good isolation! Any chance you can get yourself a bigger air gap up there? The normal recommendation is at least 4 inches between facing inner-leaf and outer-leaf surfaces. Reducing the air gap reduces isolation.

I have a few related questions about this but I will start by explaining what the plan is at the present. Above the studio is the kitchen and it can be a high traffic area in the house. The joists are 12" so there is a lot of room for insulation. I tried the room without the ceiling and full of pink insulation like in Ethan's ultimate basement studio video - remove the ceiling and let the space soak up broadband. I really need more isolation than that gave me. There is also the problem of sealing the large joist areas off on all the cavities above the outer leaf stud wall. Not to mention that even with insulation you only have the outside sheet on the house to keep the traffic noise out. Given all of that I planned on sealing the outside walls and basement cement walls with 2 5/8 sheetrock and packing the outside area above the foundation as tight as possible and caulking the heck out of everything. Then on the inside leaf 2 5/8 sheetrock inside out so technically a 3 leaf system because of the kitchen floor packed insulation 12" double sheetrock 1" space the double sheetrock on the outside of the inside leaf. (see image below) This way has two negatives as I see it. First it is a 3 leaf system and said to be less efficient than t 2 leaf system. Second there is a height problem to begin with, not to mention the 2 leaf ceiling would cut the cost and make the build easier. That said I could seal the joists on the studwall side and pack them with insulation. Use the double 5/8 sheetrock on the inside leaf including 3 or 4" of 703 for added insulation. When I tested it there was no inside leaf at all and the two sheets and inside insulation may do it. See the image below as for the original 3 leaf ceiling - Now I am leaning toward the 2 leaf if the isolation is reasonable. Which of these two plans will work best for isolation?

Soundman2020 wrote:

GIf it really is at the FRP, then absorption, at least for the guilty section.

I will go with side absorption on door (if i have one) and other side as apposed to slats. Sounds good - with or without the door. Kind of fits the Hidley dead scenario - though I was unsure of how some of those principles applied to such a small room.

Soundman2020 wrote:

John usually recommends hangers, I think. But on the other hand, superchunks are easy to build, and also work well. If you have the time, I'd go with hangers.

I am going to go with the hangers - I have an idea on how to encorperate two small sitting benches with hangers underneath increasing the bass trapping of both corners of the rear wall. If I decide to go that way I will include images and skps for anyone interested.

Soundman2020 wrote:

Yep! You can raise your speakers if you need to, then tilt them forwards (and the entire baffle along with them), so that the acoustic axes still meet just behind your ears, which should be somewhere around the 38% mark. You can tilt them down by as much as 10 degrees (some say 15) if you need to, but watch out!

I included a new version of the design with measurements from the inside of the front soffit and to the rear of the side wall not the door and gapped trap on the door at 10'4" long the 38% rule comes in at 3'11" which was a bit farther into the room than I was originally. I did center the speakers and low and behold it lined up perfectly with the the 38% rule so I hope like crazy that the measurement points make since. As for the angled soffits I am going to work on a design for that portion of the build and add that here as soon as I can. All this talk about the ceiling brings up a question I did not ask. In my online education I found several instances where splaying did not help much for walls. Can it help on the ceiling of such a small room? I also saw a build here that used 4" of rockwool for the ceiling of a project that must have been a single leaf basement design, they used hangers on the lower portion of the sidewalls and rear of the studio but the ceiling was rockwool with a light gage plastic over it with interesting splay angles. Is that a possible idea for my room. it would mean going with a single leaf design and a false ceiling. It seemed like a possibility to keep the ceiling modes as minimal as possible by adding larger spaces outside the 4" rockwool ceiling. Hey if this is a dumb side road just say so. I was unable to find that build but I will add the link as soon as I can. Thanks again Stewart and any others willing to lend a hand. Cheers

The L shaped gray area is the outside cement basement walls.

Cool! Then you only need to add an inner leaf!

In this case is the 38% point measurement from the inside leaf or from the center of the soffit wall?

Inner leaf surface (unless the center section of the soffit is going to be reflective, solid and massive). But the 38% "rule" is just a guideline anyway: it's not carved in stone. From what I've read, many engineers prefer a position a bit closer to the front wall. And in any event, just moving your head a bit in a small room will take you across several percentage points! 38% gets you in the ballpark, but then your ears will find the perfect sweet spot. So I wouldn't sweat it too much. Also, don't forget that it is your EARS that are supposed to be at 38%, and NOT the intersection point. For most room / speaker geometry layouts, the intersection of the speaker axes will be at a point about 15 - 20 cm or so behind your ears (unless you have a very unusual shaped head!). But once again, 38% is just a starting point.

If I built a door that had almost no gap and cloth covered 703 (possibly mineral wool would be more absorption) would that work or is the fact that it is a door instead of 2 layers of sheetrock and absorption?

The issue is just the reflective surface, no matter what it is made of. As long as you can get the actual reflection point (and a good margin around it) covered with a few inches deep of something like 703, that shoudl do the trick. I guess you know the "mirror trick" to finding your FRPs?

The joists are 12" so there is a lot of room for insulation.

Cool! That's good news. So basically you'll have an air gap of around 12 inches, which is excellent.

There is also the problem of sealing the large joist areas off on all the cavities above the outer leaf stud wall.

Your best bet there would be to just cut some wood blocking to fit the gaps, nail/screw it in place, and seal it with caulk. You do want to fill the gap with mass, and also get an airtight seal, so that's a good way of doing it. It's a lot of tedious work, sure, but nobody ever said that building a studio would be easy! :)

Not to mention that even with insulation you only have the outside sheet on the house to keep the traffic noise out.

Not sure what you mean by that: You say that the two gray walls are cement? Those are the outer leaf walls you are referring to, right? And the run from floor to ceiling, unbroken, right? Thick cement (concrete / brick / stone) walls are pretty much the best isolation you can get! Lots of mass. So that shouldn't be a problem. Where is the street with the traffic noise, in relation to your diagram? How bad is the traffic noise?

Given all of that I planned on sealing the outside walls and basement cement walls with 2 5/8 sheetrock

Adding layers of sheetrock directly onto an existing concrete wall won't accomplish much. You'd need many, many layers of sheetrock to match the mass in the wall, and even then it would only buy you 6 dB of extra isolation. But one or two layers of drywall up against your existing concrete won't do much. Look at the mass density of drywall vs. concrete, and you'll see what I mean. But what IS important with a bare concrete / cement wall, is to seal it. Cement is porous. porous is not good. Just paint it with something that will seal it well. Or plaster it ("render"), if you really think you need more mass in it.

Then on the inside leaf 2 5/8 sheetrock inside out so technically a 3 leaf system because of the kitchen floor packed insulation 12" double sheetrock 1" space the double sheetrock on the outside of the inside leaf. (see image below)

Not a good idea! 3 leaf raises the resonant frequency of the MSMSM system, and reduces isolation, espceially in the low end of the spectrum (drums, bass). Far better to take off the sheetrock on the underside of the studs, and use it to beef up the bottom of the floor above. So you'd cut the sheetrock into strips almost as wide as the space between the joists, then out it up against the underside of the floor above, hold it in place with cleats, then caulk it all around carefully. That will get you much better isolation, using the exact same mass. You'll have your sub-floor with a couple of layers of sheetrock on it, then a 12 inch air gap filled with insulation, then your inner leaf sheetrock. That should give you pretty good isolation. 3-leaf always loses against 2-leaf, all other factors being equal. This is what I would do if I had that situation:

Now I am leaning toward the 2 leaf if the isolation is reasonable. Which of these two plans will work best for isolation?

Definitely two-leaf! For the same total mass and wall thickness, two leaf wins against three leaf every time, and in a major way. Just moving that sheetrock from the underside of the joists to between the joists will probably gain you something like 10 dB of isolation! Well worth while, I think...

I will go with side absorption on door (if i have one) and other side as apposed to slats.

That's what I'd do too. And don't forget to keep the room as symmetrical as possible, at least as far back as your ears. What ever you do to one side should be done the same way on the other side, to keep your stereo image as tight as possible.

In my online education I found several instances where splaying did not help much for walls.

It seems to be a case of "six of one, or half a dozen of the other". Some designers swear by splayed walls. Others say it's just as good to go with straight walls, and then splay the treatment. Personally, I like the idea of splayed walls: I do think they help somewhat with two things: Keeping first reflections away from your ears, and killing flutter echo. Sure, you can deal with both using treatment, but why not just do it with the walls themselves?

Can it help on the ceiling of such a small room?

If you are going to splay your walls and angle your ceiling, then the walls need to be splayed at least 6 degrees each, and the ceiling 12 degrees. However, you already have severe height limitations in your room, so I don't think you have the luxury of being able to slope your ceiling at a useful angle. I'd just go with a straight ceiling as high as you can get it, and build any treatment you need under that.

I also saw a build here that used 4" of rockwool for the ceiling of a project that must have been a single leaf basement design,

Probably not. It was most likely an inside-out design, which you certainly can do in your case! Just fill your ceiling joist space with rockwool or fiberglass, and cover it with acoustic cloth for aesthetics. Soft ceiling, hard floor, = good acoustics. So just leave your floor as concrete (it is concrete, right?), or maybe lay some laminate flooring on top, if you prefer the look. - Stuart -

... stu's back :) long texts.. whoo

Thanks again Stuart -

Soundman2020 wrote:

Cool! Then you only need to add an inner leaf!

I assume you mean I only need the inside leaf only on the sides next to the cement wall and that I still need the outside leaf on the other two walls.

DUCHARME wrote:

Not to mention that even with insulation you only have the outside sheet on the house to keep the traffic noise out.

Soundman2020 wrote:

Not sure what you mean by that: You say that the two gray walls are cement? Those are the outer leaf walls you are referring to, right? And the run from floor to ceiling, unbroken, right? Thick cement (concrete / brick / stone) walls are pretty much the best isolation you can get! Lots of mass. So that shouldn't be a problem. Where is the street with the traffic noise, in relation to your diagram? How bad is the traffic noise?

[/quote] I was referring to the area on the outside wall above the cement up to the kitchen floor. You addressed that with the two leaf fix of the ceiling. I had not thought of a fix like that, but I did know that I had to do something with it if I did not have the ceiling sealed like in my 3 leaf plan. I will fill with wood and sheetrock layers and calk. Everything else sounds great and makes sense. I will post images of the progress and I may need some more detail help along the way. As for the noise it will be ok, I just have to remember that I am used to it so I don't notice it but in the city there is always traffic noise. I want to get as much isolation as I can without overbuilding/spending. I think your suggestions will accomplish that. I am going to ponder the door/no door booth issue it seems either will work if done properly. Thanks again- Wayne

I assume you mean I only need the inside leaf only on the sides next to the cement wall and that I still need the outside leaf on the other two walls.

Right! Yup., that's what I meant. I wasn't too clear on that. I guess I should have used more words, to keep Ro entertained!!! :) I know how he loves words.... !