Control Room, Iso Booth and Bathroom in a 26'x 20 Garage

Hi, I had another thread on the design of this, but I figured since it's been a while, and the designs have changed, I'd make a new thread. The main purpose of this room is going to be doing overdubs and mixing. The build is taking place in Los Angeles, and it's taken close to 8 months to get the permits just for the garage. Once the garage is built, I'm going to beef up the garage outer leaf with a few more layers of drywall which will be on of the two leaves for the 2 leaf system. I'm planning on doing 3 layers of 5/8" drywall and green glue for the iso booth. and 2 possibly 3 layers for the control room. Here is a link to my sketchup file if anyone would like to tinker with it or give any input on the design. https://www.dropbox.com/s/xzrlv16b1f2kp ... studio.skp Here are the basics of what I am working with. 20' x 26' garage. 10' plate heights A frame ceiling with 8/12 rise. I'm wondering about the wall angles for the control room. I've read that there should be a minimum of 6 degree splay both left and right walls for a frz listening position, but its hard to find info on when to do other angles. I'm planning on building a rectangle shaped room and then building treatment walls inside of that to control and shape the room. I would also like to flush mount my tannoy dmt 215's and possibly atc scm25a's. Can someone direct me to information on the advantages and disadvantages of monitors being higher or lower? just thinking if i have 2 sets of nearfields on the meter bridge, the mains would have to be above or outside of those. the console is a harrison 3232c and is to scale with the model. the air handler is above the bathroom and it shows the sends going counter clockwise from the bathroom, to iso booth then to the control room, and the returns running on the other tubes. The compressor would live on a pad outside of the garage. Can anyone see any obvious problems so far? Any input is appreciated. Beau

... and it's taken close to 8 months to get the permits just for the garage.

Wow! That sounds frustrating. But that implies that the garage does not exist right now, and you going to build it from the ground up? If so, great! Gives you lots more options to do it right.

I'm going to beef up the garage outer leaf with a few more layers of drywall which will be on of the two leaves for the 2 leaf system.

How about doing that as part of the actual construction? In other words, put two or three layers of 5/8 OSB directly on the outside of the studs, maybe withe Green Glue in between, before putting the final siding on? Make it much easier, faster and probably cheaper in the long run.

I'm planning on doing 3 layers of 5/8" drywall and green glue for the iso booth. and 2 possibly 3 layers for the control room.

So clearly you need a lot of isolation: What are your numbers? How much isolation are you shooting for, in terms of dB TL?

I'm wondering about the wall angles for the control room. I've read that there should be a minimum of 6 degree splay both left and right walls for a frz listening position, but its hard to find info on when to do other angles.

The 6° angle is not for RFZ: It's for flutter echo, mainly, and also helps with some other issues. But you'll generally need a much larger angle for RFZ. The smaller the room width, the larger that angle will be, but the only way to determine what the angle should be, is by ray-tracing.

I'm planning on building a rectangle shaped room and then building treatment walls inside of that to control and shape the room.

Unfortunately, that would lead to a three-leaf system in some parts of your design. If you are going with RFZ, then the room walls themselves should be splayed. If you do room walls then also add additional walls inside the room, you have added a third leaf, thus potentially reducing your isolation. In order to not waste to much space with the splayed walls of the room, you really only need to splay the front section, between the front wall and your head. From that point on backwards, the walls can remain parallel, or be angled at a lesser angle (maybe even 6°, if you suspect flutter echo will be an issue).

I would also like to flush mount my tannoy dmt 215's

I'm not familiar with those, and couldn't find much information about them on-line, but I did find a couple of photos that seem to suggest they are rear-ported. Is that the case? If so, then it might not be possible to soffit-mount them.

... and possibly atc scm25a's.

I found more info on those, and they seem to be side-ported, so those would also not be good for soffit mounting. The only real option for soffit-mounting is speakers that are front ported, or not ported at all. Soffit mounting is highly recommended, and an excellent way of improving the overall sound of the studio, but only if you have suitable speakers. So if you really want to soffit mount, then you would probably need to change your speakers for something that can be mounted easily.

Can someone direct me to information on the advantages and disadvantages of monitors being higher or lower?

You can mount them higher than the "standard" 1.2m if you want, but then you need to angle them (and the entire soffit too, if they are soffit-mounted), so that they are still aimed at your ears. The acoustic axis of the speaker should always be aimed directly at your ears, and the axes should intersect at a point a few inches behind your head. So yes, you can mount them higher and tilt them, but you should never mount them so high that you'd have to tilt them more than 10° down, and preferably no more than 7°. - Stuart -

How about doing that as part of the actual construction? In other words, put two or three layers of 5/8 OSB directly on the outside of the studs, maybe withe Green Glue in between, before putting the final siding on? Make it much easier, faster and probably cheaper in the long run.

That's exactly the advice I'm looking for! Thank you! I will do that.

So clearly you need a lot of isolation: What are your numbers? How much isolation are you shooting for, in terms of dB TL?

I'm hoping to be able to track a marshall stack full tilt with very, very little bleed into the control room. I'm also wanting to be able to mix at any hour of the night.

The 6° angle is not for RFZ: It's for flutter echo, mainly, and also helps with some other issues. But you'll generally need a much larger angle for RFZ. The smaller the room width, the larger that angle will be, but the only way to determine what the angle should be, is by ray-tracing.

can i do ray tracing within sketchup just by drawing lines from the speaker cones to the walls? Or is there a better application for that?

Unfortunately, that would lead to a three-leaf system in some parts of your design. If you are going with RFZ, then the room walls themselves should be splayed. If you do room walls then also add additional walls inside the room, you have added a third leaf, thus potentially reducing your isolation.

even if the walls are just treatment walls?.... as in just framing, owens corning, absorbers, resonators, traps, etc.? In order to not waste to much space with the splayed walls of the room, you really only need to splay the front section, between the front wall and your head. From that point on backwards, the walls can remain parallel, or be angled at a lesser angle (maybe even 6°, if you suspect flutter echo will be an issue).

I'm not familiar with those, and couldn't find much information about them on-line, but I did find a couple of photos that seem to suggest they are rear-ported. Is that the case? If so, then it might not be possible to soffit-mount them.

here is a link to the tannoys. they are front ported dual 215 mains that are normally flush mounted. http://www.primalgear.com/tannoymon007.html

I found more info on those, and they seem to be side-ported, so those would also not be good for soffit mounting. The only real option for soffit-mounting is speakers that are front ported, or not ported at all.

they are side ported, however they have the option to run ported or non ported which I run them in... But after thinking about it, I'd like to keep them on the meter bridge next to a set of ns10s.

You can mount them higher than the "standard" 1.2m if you want, but then you need to angle them (and the entire soffit too, if they are soffit-mounted), so that they are still aimed at your ears. The acoustic axis of the speaker should always be aimed directly at your ears, and the axes should intersect at a point a few inches behind your head. So yes, you can mount them higher and tilt them, but you should never mount them so high that you'd have to tilt them more than 10° down, and preferably no more than 7°.

Thanks Stuart! I'm going to work on this... Beau

they are front ported dual 215 mains that are normally flush mounted.

Cool! so you can soffit mount them with no problems. Do you know if there is some place to download the manual? There's a couple of things I'd like to check. One of those is the baffle step compensation issue, and see if it has bass roll-off controls. I imagine it does, but it would be good to check.

I'm hoping to be able to track a marshall stack full tilt with very, very little bleed into the control room. I'm also wanting to be able to mix at any hour of the night.

It would be good to put some objective numbers on those, by measuring the actual level with a good sound level meter, and also measuring what you consider "acceptable" bleed. What I consider "very little" you might consider "nothing at all" or "huge". Also "mix at any hour of the night" depends on what your family/neighbors consider to be acceptable levels at night. What one neighbor considers "accerptable" another might consider to be "I'm calling the cops and suing your butt off!". :) Those are subjective terms, but it's better to have an objective number to work with, so you can then look at alternative building methods and materials that will get you the numbers you need.

can i do ray tracing within sketchup just by drawing lines from the speaker cones to the walls? Or is there a better application for that?

That's the way I do it, yes. It's a pain, and time consuming, since you have to check a large number of rays at different angles from each speaker and carefully measure the incidence and reflection angles on each bounce, but it's the only way I know of to do it for free. There might be add-ons for SketchUp that will do that for you, but if so I haven't found one yet.

even if the walls are just treatment walls?.... as in just framing, owens corning, absorbers, resonators, traps, etc.?

If they are treatment walls, then they aren't room walls, so therefore splaying them makes no difference! :) The acoustic boundary of the room is the hard, solid, massive surfaces that define the room itself: walls, floor and ceiling. Anything you put inside that is treatment, not room. So putting angled absorbers on the sidewalls is good, from the treatment point of view, but the sound waves still see the surface behind the absorber as the room boundary, not the surface of the absorber. Absorbers are pretty invisible for most sound waves. That's a strange thing to say, for sure, but true nonetheless. Let's say you have an absorber on your wall that is rated with a coefficient of absorption of 0.50 at 100 Hz, for example. You think "Wonderful! It absorbers 50% of the energy at 100 Hz!". Yes it does, but that isn't much: that's just a 3 dB drop in sound power. Hardly worth writing home about. So if your sound wave was coming in at 100 dB, for example, then 97 dB of that still hits the wall behind the absorber and bounces back. The absorber just doesn't do much, and the wave "sees" the wall much, much more than the absorber. In other words, if you are going for RFZ, then what you splay has to be the room walls themselves, since those are what the sound will bounce off. Splaying the treatment wont have any appreciable effect.

But after thinking about it, I'd like to keep them on the meter bridge next to a set of ns10s.

It would be better to put them on stands just behind the desk, rather than on the bridge itself. Yeah, lots of people just put them on the bridge, but that doesn't make it right! If they are on the bridge, then there's a really food chance that they are making the bridge vibrate, and therefor the entire console. Plus, sitting on the bridge puts them in the perfect location for send reflections at you from the console surface itself, with the resulting comb filtering, phasing, and other SBIR artifacts. A good stand is a much better idea, provided that it is massive enough. So I'd suggest soffit-mounting the Tannoys, and putting the others on large, heavy, massive stands just behind the bridge, with a layer of Sorbothane under them, to decouple. - Stuart -

Attached is a screen shot of the control room after applying the suggestions here. I have angled the side walls 6 degrees... the flush mounted speakers are at 30 degrees. It seems I will have to toe in the flush mounted speakers a bit more in order to hit a listening position closer to the console and by the looks of the ray tracing, should i have a more severe angle to get rid of that first reflection coming back to the listening position right? Just trying to make sure I am understanding the concepts... Thanks again for all of your help. I plan on documenting the whole process in the construction forum as soon as demolition begins on the existing garage. Beau

Jay Mari wrote:

To avoid any problems that will occur in your project try to hire a contractor that can help you with your project.

Why do you think he needs a contractor? What makes you think he cannot do this himself? Please explain. - Stuart -

It seems I will have to toe in the flush mounted speakers a bit more in order to hit a listening position closer to the console

Yes, you could do that, or you could also move the speakers a bit closer to each other. Or do a bit of both.

and by the looks of the ray tracing, should i have a more severe angle to get rid of that first reflection coming back to the listening position right?

Exactly: You'll need to angle the side walls a lot more to keep those first reflections away. But since they will be angled more, you don't need to extend the angle so far back into the room. In other words, you can probably end the splayed section just a bit past the console. As long as the splayed section is big enough to keep all reflections away from your ears, that's all you need.

Just trying to make sure I am understanding the concepts...

Yup! you seem to be on the right track for sure. But one thing: don't forget the ceiling. If you want a complete RFZ, then don't forget that sound works in 3D, not just 2D, so there are major reflections coming of the ceiling from both speakers to your ears. That needs to be dealt with too. - Stuart -

Thanks Stuart! I will re-upload with changes in a bit. Thanks again, Beau

Here is where I am at. It seems the reflection in blue, (right behind the listening position) is really hard to get rid of... without making the room wider. Any suggestions?? Beau

It seems the reflection in blue, (right behind the listening position) is really hard to get rid of... without making the room wider. Any suggestions??

It's going way behind your head, so it's fine: As long as the reflections are well clear of your ears, directed either in front or behind of you, and they then travel off towards the back of the room and into something absorbent, then you are fine. However, something happened to your speaker soffits: they disappeared! :!: :shock: There is no front baffle on them any more! The speakers themselves are now butting up against the front panel and side panel, with no surface at all extending to either side. So you don't have soffits any more. The soffit front panel (the baffle itself) should be at least twice as wide as the speaker cabinet, and more if you can fit it in. The speaker should be offset a bit to one side (centered at 2/5 of the width of the panel is said to be the acoustical ideal, but you can go a bit less if you have to) rather than centered on the panel. The idea is to make that soffit baffle as wide as you can possibly fit in. Technically, it is called an "infinite baffle", since it is supposed to be "infinitely large" as compared to the wavelengths that it must deal with. In practice that just isn't possible in any realistically sized room, of course, but that's the theory: make it as wide and tall as the room allows. - Stuart -

Ok, I feel like I am finally starting to make some progress... How is this looking? I was able to get the reflections farther back behind the listening position... what do you think? Beau

Looking good! :) - Stuart -

mmm ... Tannoy DMT 215 ... spent alot of time with those guys! Just a question, though, on your ray traces ... !AND, I'm not sure if this would be an issue ... so, the correct answer may very well be generic to all monitors. First ... these are BIG monitors .... dual 15". But only one of them contains the dual concentric horn driver. The question ... you are doing ray traces from the center of the monitor, yet, the hi freq driver is located only on one half [side]. [IF you are mounting them horizontally]. So ... would the traces be accurate?? Primarily thinking of hi freq trajectory. Offhand, I do not recall what the dispersion angles are. Just a general question to be sure all things considered :wink: By the way ... what are you driving them with?

No the ray traces wouldn't be perfectly accurate. I'll have to redo them now that I'm getting the hang of the the angles. My console is in storage at the moment, so I am going to set up my 2 sets of nearfields on stands, to see how wide i will need to have the tannoys... I am guessing the HF and MF driver will be on the outside... but since the speaker should be slightly off center of the soffit, I think sliding the tannoys in towards the center along the soffit a bit should work fine. Right now, the plan is to tri-amp them with hypex n-core amps with a DEQX active crossover.

I have a couple more questions... 1. Regarding the speaker being centered at 2/5 the soffit. If i extend the walls to roughly 7.5' that puts my speakers centered at 2/5 of the wall..(roughly). would that be ok for the 2 soffits to come together and meet in the center as shown below in the first diagram? 2. If that is ok, then would it be helpful to use that yellow or yellow and green area (see below) as a large superchunk absorber in order to help absorb any reflections coming from the backs of my near field monitors? I'm basing this off my (hopefully correct) theory that since it wont be a solid wall, it won't affect the soffit/ infinite baffle performance. Thank in advance, Beau

So after quite a while of being dragged through the permit process, I'm almost there... but now i have a question about inside out walls and how they will effect low end transmission loss due to the decreased spring size. in the picture below, is a screen shot of the corner of my iso booth plan. Since I am building the garage from the ground up, I am taking the advice and doing two layers of osb on the outside instead of the usual one, and making sure to seal / caulk any way I can. then, insulation, one inch gap between studs, then 2 or possibly 3 layers drywall for the inside out wall. But my question lies with the inside out vs. regular wall. i like the idea of the inside out wall saving interior space for the iso booth, but going from a 10" spring to a 7" spring, how would that effect the low end transmission loss? I plan on tracking heavy metal guitars / marshall 4x12 cabs with 100 watt heads dimed in this room. Thanks again for all of your help, B

Theoretically, with 2 x 3/4" OSB plus 3 layers of 5/8" drywall on a 7" air gap filled with insulation: MSM Resonant frequency: 27 Hz. Does not isolate below: 37 Hz. isolates reasonably above: 53 Hz. isolates well, above: 78 Hz. For the same wall but with a 10" air gap: MSM Resonant frequency: 23 Hz. Does not isolate below: 32 Hz. isolates reasonably above: 45 Hz. isolates well, above: 67 Hz. That's just theory, of course. Your millage may vary... - Stuart -

Thanks Stuart! a difference of about 5 Hz doesn't seem to be much of a downside, considering I'll be saving almost 5 inches on the interior per inside out wall. With the possibly limited information that I have given, would you recommend any other methods to help with the isolation? One other question regarding the exterior. I live in Los Angeles, California. There isn't a ton of humidity or rain here. However, I do realize that most new construction incorporates roof venting and things like that for heat release, etc. Those are going to definitely be weak spots. Once I seal up all of those holes, what kind of moisture problems can I expect, if any? Or, would the ridge vent at the very peak/ridge of the roof not be an area of concern? Thanks again, Beau