Just Another Garage Studio

[bradvuv]

G'day guys! First post here so please be gentle. I've been reading for some time and finally have had some time to start planning my next studio space. The space will be used for mixng and mainly overdubbing. On occasions drums may be tracked in the small booth space.

I'm amining for an STC of 60+

The garage space in question (image attached) is constructed of mudbrick walls with a tin roof. My plan thus far is to make sure the existing walls are air tight and to build a ceiling with 2 x 16mm plasterboard and 240mm fibreglass insulation between the plasterboard and tin roof. The existing walls and newly built ceiling would be the outer walls.

The inner walls for control room and booth would consist of 90 x 45mm (2x4") timber stud walls with 3 x 16 mm plaster board cladding and insulation. I plan to leave a 75mm gap between outer walls (insulation between outer and inner walls) and the double stud walls between control room and booth. The ceiling, current plan is both spaces to be at a height of 2.5 meters internally these will also be clad with 3 x 16mm plasterboard and fully insulated. One question I do have is the elevation inside the garage is 2.7m to 3.9meters, would it be worth sloping the ceiling 12 degrees to take advantage of extra room volume?

Calculated room volume for Control room space with a flat ceiling is 54.6m2 and the booth space 38.4m2, again with a 2.55m flat ceiling height. My thoughts for predictability particularly in the control room space was to leave the ceiling flat and maybe run with a slope ceiling in the booth space.. thoughts?

Finally I know someone will ask, the door frame in the control room to the outside world can not be relocated with out demolisging the mudbrick wall. The door is a problem, however in my modal modeling the hot spots look to be up higher, so I hope the modleing is somewhat close for that particular corner.

I'd appreciate anyones thoughs and feedback thus far including sugestion on things I may have missed or gotten wrong.

Cheers!

[Soundman2020]

Hi Braduv, and Welcome to the Forum!

A few brief comments:

The space will be used for mixng and mainly overdubbing. On occasions drums may be tracked in the small booth space.
I'm amining for an STC of 60+

60 dB isolation is a tall order. Do-able, but not simple. Also, you shouldn't really be talking STC, but rather overall isolation: STC isn0t really applicable to studios. Here's why:
Why STC is not a good way of measuring studio isolation.

But anyway, assuming around 60 dB isolation is what you meant, that's not so easy to achieve. The good news is that you might only need that for the isolation booth (drum booth). You can probably get away with less isolation for the control room, unless you really like to track and mix with everything turned up to 11... which isn't a good idea anyway, if you value your ears. Assuming you track and mix at more reasonable levels, say around 80-90 dBC, then you don't really need 60 dB to the outside world for that. However, for the isolation room / tracking room / drum room, that might be necessary, depending on what your isolation needs really are. You might find this helpful:
Deciding on isolation for your studio

How much isolation does your studio need? How can you figure that out? Is it even important?

My plan thus far is to make sure the existing walls are air tight and to build a ceiling with 2 x 16mm plasterboard and 240mm fibreglass insulation between the plasterboard and tin roof. The existing walls and newly built ceiling would be the outer walls.

THat sound rather like you might be creating a three-leaf roof. Depending on several factors, that might or might not be a problem. There are ways of dealing with that, but you should first figure out if it is an issue in your case, or not.

The inner walls for control room and booth would consist of 90 x 45mm (2x4") timber stud walls with 3 x 16 mm plaster board cladding and insulation. I plan to leave a 75mm gap between outer walls (insulation between outer and inner walls) and the double stud walls between control room and booth. The ceiling, current plan is both spaces to be at a height of 2.5 meters internally these will also be clad with 3 x 16mm plasterboard and fully insulated.

I'd suggest replacing the first layer (the one on the studs) of drywall (plaster board) with something like 16mm OSB or plywood: that gives you about the same isolation, but also give you the major benefit of having a nailing surface around the entire room, so you can attach any type of acoustic treatment, lights, decorations, etc, any place you like, without having to worry about finding studs through three layers of drywall...

One question I do have is the elevation inside the garage is 2.7m to 3.9meters, would it be worth sloping the ceiling 12 degrees to take advantage of extra room volume?

For the control room: Not necessary. Just make it as high as you can without sloping it. But for the isolation booth: Hell yes! Most instruments and tracking rooms really love height and room volume, so it makes sense there to do whatever it takes to get as much height and volume as you can. But why only 12°? If you can get more height/volume with a different angle, then go for it!

Calculated room volume for Control room space with a flat ceiling is 54.6m2 and the booth space 38.4m2, again with a 2.55m flat ceiling height. My thoughts for predictability particularly in the control room space was to leave the ceiling flat and maybe run with a slope ceiling in the booth space.. thoughts?

Yup! You got it totally right!

Finally I know someone will ask, the door frame in the control room to the outside world can not be relocated with out demolisging the mudbrick wall. The door is a problem, however in my modal modeling the hot spots look to be up higher, so I hope the modleing is somewhat close for that particular corner.

That's a corner. The very best spot you can every hope for, for placing acoustic treatment is in the room corners, because you get a triple-boost there. All modes terminate in corners. Technically, corners are part of all three surfaces (two walls and the ceiling, or two walls and the floor), so they participate in treatment for all three room dimensions at once. Acoustic absorption in a corner is three times more effective than the same absorption mounted as a panel on a wall. And the rear wall of your studio (the one behind your head when seated at the mix position) is the wall that is going to give you the most trouble in any control room. Always the toughest one to treat. Those four rear corners are gold.

That said, if you really can't move the door, then you'll just have to work around that issue with more treatment in other places. It's not the end of the world, but it does make things tougher for you...

I'd appreciate anyones thoughs and feedback thus far including sugestion on things I may have missed or gotten wrong.

I'm guessing that's just a rough sketch, but your speaker placement looks a little off. This will explain why that's not the correct way to do it:
Speaker setup, and the equilateral triangle

Also, have you considered soffit-mounting your speakers (more correctly called "flush mounting", but everybody still calls it "soffit mounting", so I guess we are stuck with that): Soffit mounting is the single best things you can do to improve control room sound and acoustics, in pretty much every way.

You also didn't mention HVAC, and that's critical for all studios, so you should take a look at this:
Why your studio needs proper HVAC.

Studio HVAC: All about mini-split systems, HRV's and ERV's

All of that should get you on the right track!

- Stuart -

[bradvuv]

Hey Stuart, Thanks so much for your advice. Many things to ponder here. Yes, you are correct the diagrams posted are first rough revisions. The monitoring positions were thrown in last minute so readers could get an idea of the planned orientation of the control room.

HVAC design has been started. I plan for a dual head mini split system. One head in each room and a baffled exhaust system with capacity to move 800cfm/h which is 6 air cycles per hour.

OSB/ply for the initial layer on internal walls/ceiling makes complete sense and I'll implement that for sure. OSB is not used often here in Australia and can be harder to come by. 6mm or 12mm is where it's at for OSB. Would 12mm be okay considering 2 x 16mm layers plasterboard would be out over the top of it? Plywood is an option but, super expensive here in large sheets. Common thicknesses are 15mm and 17mm. I'm assuming 17mm would be the better option if using plywood?

In regard to three leaf ceiling does the tin roof count as 1 leaf? My thoughts around this are there's no isolation properties due to lack of mass in a tin roof. The fact also sealing a tin roof to create and air tight space would be very difficult. Tin can expand up to 25mm in length during hot days. My fear is any attempts in sealing the tin roof would fail over time. In your opinion would the single roof consisting of three layers dry wall or one OSB and two plasterboard layers for the ceiling be ample on its own assuming the tin roof is counted as the outer leaf?

Finally, the 12 degrees for ceiling slope was taken from literature I read many years ago by Mr Sayer. The Iso Booth I have room for a slopped ceiling from 2.55m to 3.7 meters. Is that too much?

[Soundman2020]

Source of the post Hey Stuart, Thanks so much for your advice. Many things to ponder here. Yes, you are correct the diagrams posted are first rough revisions. The monitoring positions were thrown in last minute so readers could get an idea of the planned orientation of the control room.

Cool! Makes total sense. I kind of figured that was the situation. Are you planning to soffit-mount your speakers, or just have them on stands? Also: What speakers are you planning to use?

HVAC design has been started. I plan for a dual head mini split system. One head in each room and a baffled exhaust system with capacity to move 800cfm/h which is 6 air cycles per hour.

Great! I guess that 800 cfm figure is for circulation through the rooms, but what about fresh air/stale air? That can be considerably less, to save you money on your electricity bill. The less conditioned air you have to dump overboard the better. It costs money to cool and dehumidify that air, so keeping your stale air dump to a minimum makes sense. Did you do the math on that yet?

Also on HVAC: DId you do the math on how much cooling capacity you need? 800 cfm is just the movement of air around the rooms, but it's also important that the AHU has enough cooling capacity to deal with both the sensible heat load and the latent heat load. It's not hard to work through that, but very important. You don't want to end up with a studio where the HVAC is moving enough air around the rooms, and also bringing in enough fresh air, but doesn't have enough power to cool that air sufficiently.

OSB is not used often here in Australia and can be harder to come by. 6mm or 12mm is where it's at for OSB. Would 12mm be okay considering 2 x 16mm layers plasterboard would be out over the top of it?

Probably OK from the point of view of isolation, but maybe not tough enough from the structural point of view, both as a sheer member but also to be usable as a nailing/screwing surface for heavy objects.

In regard to three leaf ceiling does the tin roof count as 1 leaf?

It might, to one extent or another, depending on several factors. Most important is the distance from that surface to the "middle-leaf" ceiling you are planning to build. You refer to that as your outer leaf, but just for clarity I'll call it the middle leaf, since it is in between your tin roof and your actual inner leaf. If that distance is fairly large, say like 30cm or more, then the resonant frequency should be low enough as to not be an issue. But if it's just a few cm, then it could very well cause you grief.

Also, metal does have a lot of mass! Steel, for example, is over ten times the density of drywall, so a thin layer of sheet metal just 1mm thick has about the same surface density as 10mm drywall.

That "leaf" doesn¿t need to be sealed to resonate: Sealing greatly improves that, of course, but even if it isn't sealed, there can still be substantial resonance going on. Think of a kick drum with a hole in the head: it still resonantes, despite the huge hole.

Your best bet here is to make that distance large enough that any three-leaf effect will be too low in frequency to be an issue, and put plenty of insulation in that air space between the tien and the middle leaf. You can also increase the mass on the middle leaf to help compensate. For example, using Green Glue on that, or an extra layer of drywall, would likely do the job. You are going to have drums in there, which is arguably the toughest instrument to isolate, so that roof issue likely needs some careful thought and calculation, to make sure in advance that it's going to do the job.

In your opinion would the single roof consisting of three layers dry wall or one OSB and two plasterboard layers for the ceiling be ample on its own assuming the tin roof is counted as the outer leaf?

You still need the "middle leaf" up there, as you already figured out. No argument with that. So you are going to have a 3-leaf system. My concern is if that's going to be a problem, and what types of measures you'll need to compensate for that. As you mentioned, I doubt it would be possible to seal that successfully, and leaving it unsealed is a good thing, so I wouldn't try to use it as the "real" outer leaf. But it will still be part of the equation! The question is: how big a part, and what can you do about that? A 3-leaf system is not the end of the world: sometimes you have no choice. It just makes your life a but harder...

Finally, the 12 degrees for ceiling slope was taken from literature I read many years ago by Mr Sayer. The Iso Booth I have room for a slopped ceiling from 2.55m to 3.7 meters. Is that too much?

12° is the minimum difference in surface angle that will supposedly stop some forms of low-frequency resonance, and flutter echo, and other unpleasant issues. John came up with that number empirically, but we never did find any science to back it up. We talked about it a few times. I'm totally sure he was right about that number! But there's no research that I'm aware of to show why 12° works, while 10° doesn't. Or to maybe show that 13° or 17° (or whatever) would be better. It would be nice if there was some theory to go with that, but we never found anything. That was his recommendation for splaying walls in small vocal booths, to minimize the "boxy" sound, as well as flutter, and some modal issues. In your case, it's not really applicable as the room is quite a bit bigger than a typical vocal booth, and in any case more air volume in the room trumps those other things. Air volume is king. Get as much air volume as you can inside the room, and if you can do that by raising the ceiling, then that's even better. Drums, especially, like high ceilings. One reason for that is the overhead mics. If you have those at a height of, for example, 2m above the floor, then they are only 50cm from the ceiling, which will likely give you comb filtering problems. even if you lower the mics to just 180 cm, they are still relatively close to the ceiling. And if you take it to extremes, putting them way down at 125cm, then you have them exactly in the first order null for the vertical axis... 125cm to the floor, and 125 to the ceiling... However, if you can get your ceiling up to 3.7 m over the drum kit, that's excellent! Even at 2m height, they are still far, far away from the ceiling, so you can get a nice clean, smooth sound out of them, with no ceiling artifacts. The drums will just also plain sound better, just using your ears. Drums like height. So do some other instruments. A high ceiling in a tracking room is almost always a good thing.

In any case, John's 12° number was the MINIMUM angle he found to be effective, and in your case the slope would be more than that, so you'd be meeting his suggestion with a greater angle.

The only issue with a heavily sloped ceiling might be aesthetics. It might look strange. But it should be possible to reduce the visual effect with good placement of acoustic treatment up there, lighting, paint schemes, etc. to disguise the steep slope. Or you could just "own it" and make it part of the character of your room! Highlight the slope, instead of trying to hide it!

- Stuart -