John Sayers' Recording Studio Design Forum Archive

Hello all,

I was making plans to build a studio on here a year ago or so, but we got a deal that was too good to pass up and we moved into a new house, so I'm starting from scratch again.

The new house has an attached two car garage that I'm planning on turning into the studio. Ideally I would like to be able to record a full band with an acoustic drum kit all at once, but I've got a few questions and some considerations.

First of all see the below for the existing floor plan. Note that the garage itself is very oddly shaped with nooks and crannies because it was added on to. The front half (from the South wall back 11' or so) was all brick. The back half was added and is finished in wood siding and is wider than the original garage.
Also it should be known that barely 45 feet from the south wall (the one labeled 15'3") is a major roadway that is fairly heavily trafficked. It is loud in the garage, you can almost tell what type of engine the car driving by has! So therefore, the studio is going to need some serious sound isolation.

The below drawing is my first thought as to how to do this, but it brings up a few questions. Please excuse the rough drawings but I'm not very good with sketchup and don't want to get into a big sketchup project until my design is somewhat finalized.
The small 30" x 10'7" room will be a bathroom/storage/maybe kitchenette?

The main studio will be the 19 x 12 area. The ceiling will be vaulted with probably about 10' high in the center. My questions are as follows:

1. I think I will be better served with one larger room rather than splitting the area into a separate control and tracking space. Am I correct?

2. I also think I will be better served making the room a perfect rectangle instead of trying to follow the nooks and crannies of the garage all the way around. This does make for an extra large gap between the inner and outer leafs in the South wall and part ot the East wall (Approx. a 1'7" gap), but I think that will be good since that is the wall facing the noisy traffic. And how do you insulate in a gap that large? Blown in? Please let me know if I'm wrong.

3. The gap on the north wall is about 1 foot, and the smallest gaps between the studio/bath room and the West wall is about 6". I'm thinking the bathroom itself will help isolate the studio so a 6" gap there isn't too bad. Also the spots with the 6" gap on the West wall have brick on the outside. The drawing looks like that wall has a nook on the outside, but the outside is square and flat with that nook being filled with brick covered by wood siding. See pic.
4. My first inclination was to build it inside out, but I don't think you can do a vaulted ceiling inside out style, and if I don't do vaulted, my ceiling will probably come down to 7' 8" or so all across the room. So my question is, is it ok to do the inside out walls and a traditional ceiling?

5. The two windows, since they will be in the outer leaf, should I just block them up from the outside and be done with them? I don't wan't the expense and trouble of trying to put natural light into the studio. Not to mention a point to break into on the bathroom window.

6. I am not married to this design, so if anyone sees a better way, please let me know!

I'm sure the answers provided will lead to more questions, but if you guys can help me get the ball rolling I would be quite grateful.

Thanks in advance,

Scotty

Scotmcg wrote:Hello all,

I was making plans to build a studio on here a year ago or so, but we got a deal that was too good to pass up and we moved into a new house, so I'm starting from scratch again.

The new house has an attached two car garage that I'm planning on turning into the studio. Ideally I would like to be able to record a full band with an acoustic drum kit all at once, but I've got a few questions and some considerations.

First of all see the below for the existing floor plan. Note that the garage itself is very oddly shaped with nooks and crannies because it was added on to. The front half (from the South wall back 11' or so) was all brick. The back half was added and is finished in wood siding and is wider than the original garage.

Image 9-13-20 at 4.41 PM.jpeg

Also it should be known that barely 45 feet from the south wall (the one labeled 15'3") is a major roadway that is fairly heavily trafficked. It is loud in the garage, you can almost tell what type of engine the car driving by has! So therefore, the studio is going to need some serious sound isolation.

The below drawing is my first thought as to how to do this, but it brings up a few questions. Please excuse the rough drawings but I'm not very good with sketchup and don't want to get into a big sketchup project until my design is somewhat finalized.

Image 9-13-20 at 6.20 PM.jpeg

The small 30" x 10'7" room will be a bathroom/storage/maybe kitchenette?

The main studio will be the 19 x 12 area. The ceiling will be vaulted with probably about 10' high in the center. My questions are as follows:

1. I think I will be better served with one larger room rather than splitting the area into a separate control and tracking space. Am I correct?

2. I also think I will be better served making the room a perfect rectangle instead of trying to follow the nooks and crannies of the garage all the way around. This does make for an extra large gap between the inner and outer leafs in the South wall and part ot the East wall (Approx. a 1'7" gap), but I think that will be good since that is the wall facing the noisy traffic. And how do you insulate in a gap that large? Blown in? Please let me know if I'm wrong.

3. The gap on the north wall is about 1 foot, and the smallest gaps between the studio/bath room and the West wall is about 6". I'm thinking the bathroom itself will help isolate the studio so a 6" gap there isn't too bad. Also the spots with the 6" gap on the West wall have brick on the outside. The drawing looks like that wall has a nook on the outside, but the outside is square and flat with that nook being filled with brick covered by wood siding. See pic.

Image 9-13-20 at 6.58 PM.jpeg

4. My first inclination was to build it inside out, but I don't think you can do a vaulted ceiling inside out style, and if I don't do vaulted, my ceiling will probably come down to 7' 8" or so all across the room. So my question is, is it ok to do the inside out walls and a traditional ceiling?

5. The two windows, since they will be in the outer leaf, should I just block them up from the outside and be done with them? I don't wan't the expense and trouble of trying to put natural light into the studio. Not to mention a point to break into on the bathroom window.

6. I am not married to this design, so if anyone sees a better way, please let me know!

I'm sure the answers provided will lead to more questions, but if you guys can help me get the ball rolling I would be quite grateful.

Thanks in advance,

Scotty

Hi,

The current layout of the unnamed space really lends itself neatly to a separate control room and tracking room like this:
the two rooms are a fairly decent size, but I can understand the temptation to build one large room, it depends on your needs: tracking and mixing? mainly mixing?

Sorry if I haven't read your thread properly, I only have time to skim through it and come up with this for now.

Paul

Thanks for the reply Paul. My needs are going to be tracking and mixing. It's going to be a lot of performance recording. There will be mixing, but it's not going to be a dedicated mix only studio. I sketched out the two rooms, and one would be about 138 sq ft (15' 7" x 8' 10")and the other is about 133 sq ft (13' 3" x 10'). That just feels like they both will be less than optimal. The tracking room will be too small to get a good drum sound, and the mixing room will need a crap ton of treatment to tame reflections and modes. Also most of the time, I will be performing as well as engineering, so the one room design I think is the way for me. (Not to mention I also lose my bathroom with a 2 room design.)

Scotmcg wrote:Thanks for the reply Paul. My needs are going to be tracking and mixing. It's going to be a lot of performance recording. There will be mixing, but it's not going to be a dedicated mix only studio. I sketched out the two rooms, and one would be about 138 sq ft (15' 7" x 8' 10")and the other is about 133 sq ft (13' 3" x 10'). That just feels like they both will be less than optimal. The tracking room will be too small to get a good drum sound, and the mixing room will need a crap ton of treatment to tame reflections and modes. Also most of the time, I will be performing as well as engineering, so the one room design I think is the way for me. (Not to mention I also lose my bathroom with a 2 room design.)

That makes sense, in that case you'll have a very nice amount of room volume for your hybrid room which (should) be easier to treat and still have ample space to move around.

You can do a vaulted ceiling inside out in theory, although it is a little more tricky in practice. Just one thing to remember with inside out construction - you need to make sure the air gap between your inner and outer leaves will still be sufficient for your isolation needs otherwise it is a truly compromised approach. You can use greg's TL calculator to help you with that.

I think I would set the listening position up so that it faces the bottom short wall in your plan, have the speakers fire into the longest dimension and use the rear of the room (the top of your pic where the double door are) as your tracking area. It's also a good idea to try and keep the double doors if you can do it without trashing your isolation, or at least one extra big door so that you can load in and out easily.

Those are my thoughts for now,
Paul

I still have a few questions. Mainly what to do about the air gap in the walls where it measures about 1' 7". That's going to be impossible to completely fill with insulation unless I do blown-in. Is that ok? Or just stuff the biggest bats of insulation in each wall and just have an open air gap for the rest of the space?

Also, does having an extra large gap on some walls but not all, do anything for my isolation? Or do the smaller gaps negate the benefits of the larger ones?


Thanks,

Scotty

For sound isolation the bigger the air gap the better. However, this air gap will gain say 10dB of Transmission Loss if the airgap is fully damped.
Fully damped means entirely filled with the fibre gently pressing on the enclosing surfaces. Light cheap insulation is the best choice. One would typically need to insert wires or such to prevent it from sagging. Perhaps you could find a way to drop in wired 'packages' Or drop it in contained in bags?
Sound isolation is undermined by the weakest spot, but that does not mean it is a waste of time going for the best everywhere else. Area matters.

Are you measuring your air gap from mass to mass or frame to frame? e.g. outer leaf drywall to inner leaf drywall or the gap between the two sole plates?

Just in case - you need to measure mass to mass.

So then I would ask, do you really need an air gap of 1' 7" ? That is huge. It will provide excellent isolation if constructed properly, but there comes a point of diminishing returns with MSM assemblies, you could save a bit of space and still get almost the same isolation by doing 3 layers of drywall on each leaf and ~13" between them.

MSM assemblies are essentially membranes - The bigger the air gap the lower the cavity resonance, the more mass the more reflective = the better the isolation at LF.

Filling the cavity will lower the resonance even more, but I would not be concerned with filling the entire 1' 7" or not, the air gap is so large that it could almost be a corridor. You could fill it with as much insulation as you can but don't sweat over a small air gap. If you wanted to fill it completely this can easily be done by throwing a load of attic roll, I don't know why you thin it would be impossible to fill?

Having varying air gaps is not a problem, makes it harder to predict the outcome but as long as the smallest air gap provides adequate isolation for your needs then you can assume the places where you have larger air gaps will only improve things further.

Paul

After some more consideration, I've come up with what I think is a final basic design. Of course that leads me to a new set of questions that I'm hoping you guys can help me with.

This is the one room design I came up with. I did narrow the air gaps some, and may play with them some more, but this is the general idea. The rectangle at the bottom is the mixing desk, and the small square room is a storage closet that may do double duty as an amp iso booth, or maybe even a vocal iso.

Again, I apologize for the bad 2D drawings, I just don't want to get involved in Sketchup until I'm sure things won't drastically change.
My questions are as follows:

1. I made the bath room within the inner leaf so as not to need double doors, but it just hit me that I need to bring the pipes into the bathroom from the outer leaf wall behind it. The toilet is going to be a self contained unit with a grinder pump like this so it doesn't go down thru the slab, it only needs a 1" PVC pipe to pump out, so I've got to bring in a 1" pipe for the drain and 2 - 1/2" pipes for the hot and cold water. Am I going to trash my isolation by doing that? I could bring them through the outer leaf and turn 90 degrees and the bring it through the inner leaf a few stud bays down so it's not a straight shot and caulk the hell out of the penetrations, but would the isolation loss not be worth it? Should I move the bathroom to be part of the outer leaf? The problem with that is now I need double doors and there's really not enough room to swing a second door into the bathroom (the doors in the drawing are 24", about as small as you can go). See drawing below:
I suppose I could do a pocket door on the inside bathroom, but that will have almost no sound isolation. Which is my best bet?

2. HVAC - I plan on using a mini split ductless system mounted on the back wall (opposite the desk). What do I do about the bathroom and the closet? Should I put a grill in the door of each to let some air in? Will they get enough just being opened and closed? If I don't use the bottom door closer will the gap at the bottom of the door be enough?I could possibly run a small duct from the main house's ac handler into them, but again I think that would trash my isolation, as it would have to penetrate from the outer leaf through the inner (unless I put the bathroom on the outer).

Also on HVAC, I know I will need to cycle out the old air and draw in new fresh air, I understand the concepts and the silencer boxes. My question is, Is just one register for intake and just one register for discharge good enough? I see many systems designed with these dual register silencer boxes. Is that better? My room volume is only 236 CFM and for fresh air only the 30% volume is 71 CFM. So a 7" round duct is properly sized. So I'm thinking a 10x10 register for each ought to cover me.

I believe that's it for now. As always, the help is much appreciated!

-Scotty

Scotmcg wrote:After some more consideration, I've come up with what I think is a final basic design. Of course that leads me to a new set of questions that I'm hoping you guys can help me with.

This is the one room design I came up with. I did narrow the air gaps some, and may play with them some more, but this is the general idea. The rectangle at the bottom is the mixing desk, and the small square room is a storage closet that may do double duty as an amp iso booth, or maybe even a vocal iso.

Again, I apologize for the bad 2D drawings, I just don't want to get involved in Sketchup until I'm sure things won't drastically change.

snapshot-Sat, 10 Oct 2020 02 03 51 GMT.png

My questions are as follows:

1. I made the bath room within the inner leaf so as not to need double doors, but it just hit me that I need to bring the pipes into the bathroom from the outer leaf wall behind it. The toilet is going to be a self contained unit with a grinder pump like this

ascentII.jpg

so it doesn't go down thru the slab, it only needs a 1" PVC pipe to pump out, so I've got to bring in a 1" pipe for the drain and 2 - 1/2" pipes for the hot and cold water. Am I going to trash my isolation by doing that? I could bring them through the outer leaf and turn 90 degrees and the bring it through the inner leaf a few stud bays down so it's not a straight shot and caulk the hell out of the penetrations, but would the isolation loss not be worth it? Should I move the bathroom to be part of the outer leaf? The problem with that is now I need double doors and there's really not enough room to swing a second door into the bathroom (the doors in the drawing are 24", about as small as you can go). See drawing below:

snapshot-Sat, 10 Oct 2020 02 30 31 GMT.png

I suppose I could do a pocket door on the inside bathroom, but that will have almost no sound isolation. Which is my best bet?

2. HVAC - I plan on using a mini split ductless system mounted on the back wall (opposite the desk). What do I do about the bathroom and the closet? Should I put a grill in the door of each to let some air in? Will they get enough just being opened and closed? If I don't use the bottom door closer will the gap at the bottom of the door be enough?I could possibly run a small duct from the main house's ac handler into them, but again I think that would trash my isolation, as it would have to penetrate from the outer leaf through the inner (unless I put the bathroom on the outer).

Also on HVAC, I know I will need to cycle out the old air and draw in new fresh air, I understand the concepts and the silencer boxes. My question is, Is just one register for intake and just one register for discharge good enough? I see many systems designed with these dual register silencer boxes. Is that better? My room volume is only 236 CFM and for fresh air only the 30% volume is 71 CFM. So a 7" round duct is properly sized. So I'm thinking a 10x10 register for each ought to cover me.

I believe that's it for now. As always, the help is much appreciated!

-Scotty

Do you definitely need a toilet in your studio? I am just asking because having a bathroom with a toilet opening directly out into a control room is usually avoided due to privacy/unpleasant odours. If it's only ever going to be yourself that uses your studio then it's not such a big issue as long as you are okay with it.

Bringing the 1" pipe in from the outside is not a massive concern, think about it - the studio wall which the bathroom is behind and the door to the bathroom are going to be the continuation of your inner leaf, as long as the door is tight with the appropriate seals then whatever happens behind that door should not majorly effect your studio isolation. Yes, if you can offset the penetrations between the leaves and a 90 degree turn in the pipe and sealing all the penetrations with backer rod and caulk then that will also help.

You will also need to make a penetration for your mini split pipework, so you'll need to do the same there.

You will definitely need an extractor fan in your bathroom that extracts directly outside, and I think I would also have a separate fresh air supply just for the bathroom. It only needs to be small since there will only ever be one person in that room, so basically a hole that is big enough to provide 15cfm of air with 6 changes per hour should be enough, the air will naturally get drawn in due to the exhaust fan drawing the air out.

If you decide to make the cupboard a vocal booth then you would also need fresh air ventilation in there, I might be tempted to just put a vent in the door but that might not be code compliant. The vent would work fine to exhaust hot air from amps etc, but might not be good enough to keep a person alive. If it's just going to stay as a cupboard with nothing that gets hot then it won't need any ventilation.

Have you looked into getting a HRV/ERV? If you can build a little room for the main unit itself then you can duct fresh air and exhaust stale air in multiple rooms from the same unit and they are very energy efficient. They would be the best solution for you if you need to properly ventilate 3 rooms.

1 fresh air supply register and 1 exhaust will be enough for your space, but by using multiple you can lower the velocity which reduces the noise caused by the air flowing out of the ducts. If you can get your velocity low enough (at least below 300ft/min, ideally below 100ft/min) then you only need one.

Paul

OK, advice taken and analyzed. I think this really is the final design... (No really!)

I re-examined the previous idea and realized that a 30" x 30" closet was completely useless. I also decided that the bathroom was nice but unnecessary. So I have created a large, useful closet, and removed the bathroom. The closet will not hold people or anything but stuff, so no ventilation is required. One mini split and fresh air return on the rear wall, one stale air exhaust on the front wall. Keeping everything simple as possible. See below:
So, moving on to HVAC, I have a few questions:

I calculate my room to be 2800 cubic feet. At 6 air changes an hour= 2800 * 6 = 16800 cu ft/60 minutes = 280 CFM

280 CFM * 30% = 84 CFM - Volume of air my ventilation system must move.

So, shooting for about 200 ft/min at the register (silencer boxes end up too big going for 100 ft/min) we get 84/200 = .42 sq ft

convert to sq in = .42 * 144 = 60.48 sq in - cross sectional area of silencer boxes.

And I would connect the boxes with 6" round duct from the below chart.
So using Gregwor's box sizing equations, my 4 silencer boxes would be 23" x 43.5" x 8". X would be 8" as would Z, so the CSA would be 64 sq in.

Is that how it's done? or did I screw up the math somewhere?

The questions that arise now are:

1. How do you attached the baffle boxes? Can you just attach them to the studs in each leaf with some kind of brackets? I'm figuring I will make the gap between my inner and outer leaf large enough to fit them. That would only add about 2-3 inches to the existing gap. The ceiling is going to be a no-go for anything like that.

2. The inline fan, according to the calculations on the Fantech website, needs to be the 5" model. But my ducting is 6". Can I reduce down on the way out? I'm planning on putting the fan on the exhaust side. And I assume the fan is going to need to be accessible for service? That might be an issue...

3. The registers in the room, should at least be equal to the cross sectional area, correct? So they would need to be about 12x12 to account for about 40-50% closed area on a standard register (shooting for 64" open area)?

I think I understand all the concepts and have this correct, but It's quite a lot to digest, so I'm all ears if anyone sees an error.

Thank you all,

-Scotty

Scotmcg wrote:OK, advice taken and analyzed. I think this really is the final design... (No really!)

I re-examined the previous idea and realized that a 30" x 30" closet was completely useless. I also decided that the bathroom was nice but unnecessary. So I have created a large, useful closet, and removed the bathroom. The closet will not hold people or anything but stuff, so no ventilation is required. One mini split and fresh air return on the rear wall, one stale air exhaust on the front wall. Keeping everything simple as possible. See below:

snapshot-Mon, 12 Oct 2020 21 41 03 GMT.png

So, moving on to HVAC, I have a few questions:

I calculate my room to be 2800 cubic feet. At 6 air changes an hour= 2800 * 6 = 16800 cu ft/60 minutes = 280 CFM

280 CFM * 30% = 84 CFM - Volume of air my ventilation system must move.

So, shooting for about 200 ft/min at the register (silencer boxes end up too big going for 100 ft/min) we get 84/200 = .42 sq ft

convert to sq in = .42 * 144 = 60.48 sq in - cross sectional area of silencer boxes.

And I would connect the boxes with 6" round duct from the below chart.

Residential%20Duct%20Sizing%20Guide.png

So using Gregwor's box sizing equations, my 4 silencer boxes would be 23" x 43.5" x 8". X would be 8" as would Z, so the CSA would be 64 sq in.

Is that how it's done? or did I screw up the math somewhere?

The questions that arise now are:

1. How do you attached the baffle boxes? Can you just attach them to the studs in each leaf with some kind of brackets? I'm figuring I will make the gap between my inner and outer leaf large enough to fit them. That would only add about 2-3 inches to the existing gap. The ceiling is going to be a no-go for anything like that.

2. The inline fan, according to the calculations on the Fantech website, needs to be the 5" model. But my ducting is 6". Can I reduce down on the way out? I'm planning on putting the fan on the exhaust side. And I assume the fan is going to need to be accessible for service? That might be an issue...

3. The registers in the room, should at least be equal to the cross sectional area, correct? So they would need to be about 12x12 to account for about 40-50% closed area on a standard register (shooting for 64" open area)?

I think I understand all the concepts and have this correct, but It's quite a lot to digest, so I'm all ears if anyone sees an error.

Thank you all,

-Scotty

It looks pretty good so far.

I would consider blowing fresh air into your space rather than exhausting it, otherwise your room will be in negative pressure which could bring dust in. There's also several advantages to having a positive pressurised room; It will increase your transmission loss due to the sound fighting against the air being forced in. It will help keep your doors tight up against the seals. It will keep dust out. You can filter the air before it hits the silencers, which means you'll have clean air coming in.

The ductwork feeding the first silencer will have a smaller CSA than the silencer itself, then the silencer will at least double in CSA so that when the air passes through it has a sudden change in impedance which reduces velocity. So, on the first silencer box (your outer leaf supply box) where the duct enters the silencer that hole will be sized smaller than the exit hole and then every other hole of all the proceeding silencer boxes. Hope that makes sense?

If you did want to reduce velocity further once inside your room you could have a Y splitter attached to the exit hole of the silencer, then attach some duct work to both ends of the splitter which then attaches to two registers. This would divide the CFM in to 2, which means less velocity per register. If designed right, this is a way to not only reduce velocity but also duct size and register size. But, of course it means you would need twice as many of each. Looks like you've got your velocity down nice and low anyway, so probably no need.

In fact, if you can avoid duct work altogether then that's even better. You can simple use your silencers as the only ducts by positioning them correctly. Then either attach a register directly to the silencer sleeve, or simply just leave it as a hole.

I even think you might not need such high air flow to begin with. If you only need 15cfm per person and the majority of the time it's only going to be yourself in the space then you could get a lower CFM fan and have an even quieter system.

Either way, looks like you have grasped the concepts well enough and you are able to size your silencer boxes correctly, so that's good.

The boxes will need to be attached to the studs in your case since you can't put them in the ceiling. One thing to consider is making the boxes taller than wider, so that they can be supported by the floor rather than just the wall. Along as the CSA that you need stays the same you can make them any shape. Just caulk the whole side which connects directly to the wall, and screw it into place. You can use some rubber between that face and the wall if you want to make it a tighter seal. You could do it from the other side if it's accessible, or use cleats or brackets. However you want to do it. Then seal all the way round the perimeter.

You need to make sure that your silencer boxes have sleeves which maintain the surface density of the rest of your build. These sleeves penetrate through the walls so that the mass layers are continuous.

Regarding the layout of your space, the closet is fine but why not extend it all the way along the alcove? That small little squarish area of space next to your closet seems like a waste unless you have plans for it?

I would either keep the closet and make the room completely rectangular, or get rid of the closet and use the extra space in the room. I think I would at least make the whole room symmetrical, it will be easier to treat.

Paul

Thanks for the quick reply Paul! Some answers and some more questions:

I would consider blowing fresh air into your space rather than exhausting it,

Will do, but to ask again, I will need to be able to access the fan, correct? That's going to be tough I think.

I even think you might not need such high air flow to begin with. If you only need 15cfm per person and the majority of the time it's only going to be yourself in the space then you could get a lower CFM fan and have an even quieter system.

I will have a five-piece band in there sometimes rehearsing and recording so I better account for that.

Regarding the layout of your space, the closet is fine but why not extend it all the way along the alcove? That small little squarish area of space next to your closet seems like a waste unless you have plans for it?

Yes I do, Thats going to hold a dorm fridge and a small bar sink in a built-in cabinet with a coffee pot on the counter and a microwave hanging on the wall. And it will be covered by a heavy acoustic blanket on a ceiling track that hangs in front of it when recording and mixing. See render below:

The boxes will need to be attached to the studs in your case since you can't put them in the ceiling. One thing to consider is making the boxes taller than wider, so that they can be supported by the floor rather than just the wall. Along as the CSA that you need stays the same you can make them any shape.

I like the idea of putting them on the floor, but I don't understand how to size them if I deviate from Gregwor's calculations (see below). Isn't the CSA the X dimension multiplied by the Z dimension? So if X gets smaller, Z has to get bigger to maintain the CSA. How does making it longer (the 4X+11.5 dimension in the photo) affect the CSA ?

Just caulk the whole side which connects directly to the wall, and screw it into place. You can use some rubber between that face and the wall if you want to make it a tighter seal. You could do it from the other side if it's accessible, or use cleats or brackets. However you want to do it. Then seal all the way round the perimeter.

But they won't be directly against the wall (leaf), at least the outer leaf box won't . They are (were) going to be larger than the 16" OC stud spacing so they would fit against the studs with space between the box and the leaf. I understand caulking the sleeve where it penetrates the leaf but what about the perimeter on the outer leaf box? Quick drawing below:
The grey are wall studs, the white are the leafs, the boxes are labeled and the yellow would be the insulation in the wall. I can caulk and seal the inner box directly to the sheeting because I'm building the inner leaf inside out, but what about the outer leaf? I hope this makes sense.

Thanks again,

-Scotty

Scotmcg wrote:Thanks for the quick reply Paul! Some answers and some more questions:

I would consider blowing fresh air into your space rather than exhausting it,

Will do, but to ask again, I will need to be able to access the fan, correct? That's going to be tough I think.

I even think you might not need such high air flow to begin with. If you only need 15cfm per person and the majority of the time it's only going to be yourself in the space then you could get a lower CFM fan and have an even quieter system.

I will have a five-piece band in there sometimes rehearsing and recording so I better account for that.

Regarding the layout of your space, the closet is fine but why not extend it all the way along the alcove? That small little squarish area of space next to your closet seems like a waste unless you have plans for it?

Yes I do, Thats going to hold a dorm fridge and a small bar sink in a built-in cabinet with a coffee pot on the counter and a microwave hanging on the wall. And it will be covered by a heavy acoustic blanket on a ceiling track that hangs in front of it when recording and mixing. See render below:

snapshot-Tue, 13 Oct 2020 20_21_02 GMT.png

The boxes will need to be attached to the studs in your case since you can't put them in the ceiling. One thing to consider is making the boxes taller than wider, so that they can be supported by the floor rather than just the wall. Along as the CSA that you need stays the same you can make them any shape.

I like the idea of putting them on the floor, but I don't understand how to size them if I deviate from Gregwor's calculations (see below). Isn't the CSA the X dimension multiplied by the Z dimension? So if X gets smaller, Z has to get bigger to maintain the CSA. How does making it longer (the 4X+11.5 dimension in the photo) affect the CSA ?

Gregwor%27s%20Silencer%20Box.png

Just caulk the whole side which connects directly to the wall, and screw it into place. You can use some rubber between that face and the wall if you want to make it a tighter seal. You could do it from the other side if it's accessible, or use cleats or brackets. However you want to do it. Then seal all the way round the perimeter.

But they won't be directly against the wall (leaf), at least the outer leaf box won't . They are (were) going to be larger than the 16" OC stud spacing so they would fit against the studs with space between the box and the leaf. I understand caulking the sleeve where it penetrates the leaf but what about the perimeter on the outer leaf box? Quick drawing below:

Wall.jpg

The grey are wall studs, the white are the leafs, the boxes are labeled and the yellow would be the insulation in the wall. I can caulk and seal the inner box directly to the sheeting because I'm building the inner leaf inside out, but what about the outer leaf? I hope this makes sense.

Thanks again,

-Scotty

If the boxes get longer then it doesn't affect the CSA, it's the same as using a short duct or long duct... the CSA of the duct stays the same no matter the length. Imagine cutting a slice through the box and measuring the height and width, that's your CSA. If anything making the boxes longer will improve their effectiveness as it means there will be more baffles and a longer path length that the sound needs to try and pass through.

I don't see a problem with the boxes not resting directly up against the wall panels as long as the sleeve that penetrates the wall is completely sealed and constructed from the same surface density as the wall materials. You could even build a funny shaped box where a portion of it does in fact fit between the studs and then gets wider for the part in the cavity.

You could also have your outer leaf box outside, instead of inside the cavity. Build it into your soffits at the eaves.

Yes the fan needs to be accessible, why is that a problem? Again you can install in an external cupboard.

Paul

Paul, I can't tell you how grateful I am for you to take the time to respond to my questions. It is much appreciated!

If the boxes get longer then it doesn't affect the CSA, it's the same as using a short duct or long duct... the CSA of the duct stays the same no matter the length. Imagine cutting a slice through the box and measuring the height and width, that's your CSA. If anything making the boxes longer will improve their effectiveness as it means there will be more baffles and a longer path length that the sound needs to try and pass through.

So I really just need to keep them at 23" wide by 8" deep. If I make them skinnier, I'll need to make them deeper. making them 7' tall would just let them rest on the floor and be more efficient due to more baffles.

So a few more questions...

My original plan was to put the mini split at the rear of the room with the fresh air duct right by it and put the stale air exhaust in the front above the mixing desk. Due to the position of the main house and a few other factors, it would be much easier to put the split unit at the front by the desk and have the exhaust at the rear. Would that be an issue? Too cold at the desk and too warm at the rear where the drummer would be? Not to mention all the bass trapping on that rear wall.

The main house AC compressor is right outside the rear right wall. I assume any vent, fresh or stale should not be right above it?

Would there be an issue of putting the exhaust vent and split unit on the opposing side walls?

And sizing the Mini Split itself. According to the calculations in Rod's book, I only need a 9,000 BTU/hr unit (my heat load only adds up to 7,985 BTU), but that unit on high only has a CFM of 268 and I need 280. Should I upsize to the 12,000 BTU unit with a CFM of 282?

Yes the fan needs to be accessible, why is that a problem? Again you can install in an external cupboard.

Good to know. That's exactly what I'm going to have to do, unless I can somehow put it in the inside closet.

Thanks again,

-Scotty

Scotmcg wrote:Paul, I can't tell you how grateful I am for you to take the time to respond to my questions. It is much appreciated!

If the boxes get longer then it doesn't affect the CSA, it's the same as using a short duct or long duct... the CSA of the duct stays the same no matter the length. Imagine cutting a slice through the box and measuring the height and width, that's your CSA. If anything making the boxes longer will improve their effectiveness as it means there will be more baffles and a longer path length that the sound needs to try and pass through.

So I really just need to keep them at 23" wide by 8" deep. If I make them skinnier, I'll need to make them deeper. making them 7' tall would just let them rest on the floor and be more efficient due to more baffles.

So a few more questions...

My original plan was to put the mini split at the rear of the room with the fresh air duct right by it and put the stale air exhaust in the front above the mixing desk. Due to the position of the main house and a few other factors, it would be much easier to put the split unit at the front by the desk and have the exhaust at the rear. Would that be an issue? Too cold at the desk and too warm at the rear where the drummer would be? Not to mention all the bass trapping on that rear wall.

The main house AC compressor is right outside the rear right wall. I assume any vent, fresh or stale should not be right above it?

Would there be an issue of putting the exhaust vent and split unit on the opposing side walls?

And sizing the Mini Split itself. According to the calculations in Rod's book, I only need a 9,000 BTU/hr unit (my heat load only adds up to 7,985 BTU), but that unit on high only has a CFM of 268 and I need 280. Should I upsize to the 12,000 BTU unit with a CFM of 282?

Yes the fan needs to be accessible, why is that a problem? Again you can install in an external cupboard.

Good to know. That's exactly what I'm going to have to do, unless I can somehow put it in the inside closet.

Thanks again,

-Scotty

You could have the mini split at the front and the exhaust at the back, but there's a couple of things to consider. The mini split will make a little bit of noise when it is on which is likely to be more obvious at the front since you'll be closer and facing it. The sound from the loudspeakers will likely drown it out so it's not a huge deal. The air being forced out of the unit can also have a very subtle effect on the sound waves as they leave the loudspeakers, Again, it's subtle but if you're being particularly fussy then it's something to be aware of. You can always turn it off when doing crucial mixing.

Yes, try to position vents etc away from the compressor, but if your silencers are working properly then it shouldn't make too much difference. But, every little helps for sure.

Regarding sizing the AC unit, and this is my opinion only, the unit itself is not providing any fresh air so it's not a huge deal, you can upsize if you want or just stay with the smaller one. You might find that the smaller one on full power is more noisy than the bigger one on less power. Look at the noise ratings or even better try to demo them in person and measure it.

Paul