John Sayers' Recording Studio Design Forum Archive

Hi everyone. These forums are amazing so thanks to everyone involved.

I'm hoping to get some feedback on my plans for a home studio from the ground up. Here are a couple of pics of the site, one looking directly south at the wall of the house that the studio will be adjacent to (the bush, steps and fence will be removed), and the other diagonally across the lawn towards the same wall of the house.
The plan is to build the studio next to the wall of the house in the pictures but dig down a fair way so that the roof of the building is roughly level with the existing lawn. I'm planning a 150mm suspended concrete slab for the roof, covered by 200mm of soil with grass. The outer leaf walls will be 190mm wide core filled concrete blocks, and will be retaining soil on all sides at varying depths, and completely on the east side where the upper lawn is. I have two reasons for planning it this way - one is to extend the lawn area and the other is to help with sound isolation.


Sound isolation requirements

Ideally I'd like to be able to play at 115dB in the live room and have it no louder than 40dB in my son's bedroom which is behind the wall in the pictures. I believe the laws allow up to 48dB in the neighbour's house which is around 10m from the west wall of the studio. Estimating a 9db drop from outside the studio walls to the neighbour's house gives a requirement of 57db maximum leakage from the studio. I'm guessing if I achieve this then there'll be no problem in my son's room as there should be more than 17db transmission loss into a brick veneer house.


Dimensions

The dimensions of the exterior walls will be 8.8m x 6.6m x 2.8m (with the concrete slab on top of the walls, so 2.8m internal height).

I'm planning a 1.9m soil filled gap between the 6.6m concrete block wall and the wall of the house, though the concrete block wall will be completely below the concrete slab of the house. The house is brick veneer and the window that can be seen is into the laundry rather than the bedroom.

I'm not sure if I will need a floating floor in the inner leaf, but I'm hoping not since reading the thread about the merits of the a concrete slab on grade. Also the studio slab will be approx 2m under the bottom of the foundations of the house.

There will be 307mm high steel beams supporting the suspended slab, so unfortunately I'll lose a fair bit of ceiling height with the internal leaf. I'm working on 2.47m internal height (2800mm - 307mm beam - 10mm air gap - 16mm plasterboard).

I'm planning a 1800mm x 600mm window in the north side (away from the house) for natural light, and two sliding doors between the control room and live room (one in each wall).


Room modes

I've chosen one of the 'best' ratios from http://www.acoustics.salford.ac.uk/acou ... om_sizing/ for the control room - 2.47m x 3.87m x 4.56m, and a '2nd best' ratio for the live room - 2.47m x 4.12m x 5.95m.

Here's a picture of the proposed layout:
Ray tracing

I used amray to try to minimise reflections at the listening position, but I'm not really sure of the best approach. See screenshot:
HVAC

I've calculated the volume of the two main rooms at around 100 cubic metres, so aiming to exchange 600 cubic metres per hour, or 10 per minute. If I make 40cm square ducts out of 18mm OSB and 25mm duct liner, that's a cross sectional area of 0.1 square metres, giving a velocity or 100m per minute which is around 328 feet per minute. Hopefully that's close enough!

I have space for big silencer boxes in the entranceway (see the beige boxes in the pictures below), and plan to make the inlet go to the control room, where there will be a split system for temperaure / humidity (the yellow box above the door). Then via silencer boxes in the entranceway to the live room, then via more silencer boxes in the entranceway to the outlet. Pictures:
Questions:
- will 1x 16mm plasterboard on the inner leaves be sufficient for isolation?
- should I adjust the length of the control room in the room mode calculation to account for the soffits and angling the walls at the back corners?
- should I change the angles of the soffits etc?
- is it ok for the air flow to go from the control room to the live room? The alternative is independent ventilation I guess, which would require two split systems and more holes in walls...
- any recommendations for finding good wall angles with amray?

Thanks in advance!

Hello & howdo' RolandMaker?
Your plan is ambitious and you have clearly put a lot of time in to it already. I'm not certain that I have completely understood the proposed design but few initial thoughts occur to me.

The plan is to build the studio next to the wall of the house in the pictures but dig down a fair way . . .

If this was my project, the first call I would make would be to a structural engineer to make certain that excavating next to the house is practical and safe. I'm sure you have thought of this but it's worth mentioning in case you haven't.

Ideally I'd like to be able to play at 115dB in the live room and have it no louder than 40dB in my son's bedroom which is behind the wall in the pictures. I believe the laws allow up to 48dB in the neighbour's house which is around 10m from the west wall of the studio. Estimating a 9db drop from outside the studio walls to the neighbour's house gives a requirement of 57db maximum leakage from the studio. I'm guessing if I achieve this then there'll be no problem in my son's room as there should be more than 17db transmission loss into a brick veneer house.

If I understand you, you are looking for a transmission loss of 58dB? Have you tried running the numbers on Greg's T/L calculator?
http://www.johnlsayers.com/phpBB2/viewt ... =1&t=21770

I've calculated the volume of the two main rooms at around 100 cubic metres, so aiming to exchange 600 cubic metres per hour, or 10 per minute. If I make 40cm square ducts out of 18mm OSB and 25mm duct liner, that's a cross sectional area of 0.1 square metres, giving a velocity or 100m per minute which is around 328 feet per minute.

I have to be honest and tell you that I have found working out the HVAC requirements for my own plan extremely difficult (and it's seemingly even harder to hire professional help with this aspect of studio design). Conventional wisdom has it that the velocity of the air entering your room should be no more that 300 fpm at the registers (ideally much slower). This is so there is no audible 'woosh' to spoil your recordings and mixes, but the good news is that you can slow the airflow down by increasing the CSA of your silencers (this is, in fact, the only way to do it). You will certainly need a heat exchanger in each room and the silencers should direct the incoming air directly into them (typically the intakes are on the top surface, so placing the inner leaf silencer in the ceiling and the heat exchanger directly below is the easiest way to achieve this). Otherwise you run the risk of having 'hot spots' in your rooms due to inefficient cooling and de-humidification.
I'm afraid I can't help with your other questions, but I wish you good luck and look forward to reading more about your project. John.

Thanks so much for your thoughts John!

John Steel wrote: If this was my project, the first call I would make would be to a structural engineer to make certain that excavating next to the house is practical and safe.

Yes, actually my original design was closer to the house (0.4m) but after speaking with a structural engineer I moved it further away so the top of the new slab is at least as far away from the house as it is beneath the bottom of the house foundations. Otherwise there would have been significant cost involved to underpin the house foundations.

If I understand you, you are looking for a transmission loss of 58dB? Have you tried running the numbers on Greg's T/L calculator?
http://www.johnlsayers.com/phpBB2/viewt ... =1&t=21770

Yes that's right, sorry it wasn't clearer! I hadn't seen the calculator and if I'm understanding it correctly then one layer of gypsum should be fine:

You will certainly need a heat exchanger in each room and the silencers should direct the incoming air directly into them (typically the intakes are on the top surface, so placing the inner leaf silencer in the ceiling and the heat exchanger directly below is the easiest way to achieve this). Otherwise you run the risk of having 'hot spots' in your rooms due to inefficient cooling and de-humidification.

Perhaps I can squeeze inner leaf silencers into the ceiling cavity if I do inside-out ceilings and make the OSB 16mm instead of 25mm. If I do independent ventilation for each room can I split the ducts for the outer leaf penetrations after the silencer box or would I need to have separate inlet and outlet ducts for each room?

Thanks,
Roland.

Perhaps I can squeeze inner leaf silencers into the ceiling cavity if I do inside-out ceilings and make the OSB 16mm instead of 25mm.

Inside out ceilings have numerous other benefits which offset the extra cost and construction time. An important factor in deciding how to build your silencers (inner leaf or outer) is that the materials used match the density of the rest of the leaf. Otherwise you are creating an acoustic 'window' (for want of a better word).

If I do independent ventilation for each room can I split the ducts for the outer leaf penetrations after the silencer box or would I need to have separate inlet and outlet ducts for each room?

I believe you can split the ducts in this way or you may decide to build more than one silencer. I think either approach would work. My design is a single room within a room so I haven't had to work out the specifics of this kind of construction. There are many design and build threads on the forum that are searchable and I would encourage you to read as many of them as possible, then apply the concepts and techniques to your own design.

- should I adjust the length of the control room in the room mode calculation to account for the soffits and angling the walls at the back corners?

No. Your modes are going to be calculated using your inner leaf sheathing, not the acoustic devices (such as soffits). Also, you shouldn't be angling your actual inner leaf back corners. The angles you see in studio pictures is actually acoustic treatment such as bass traps. Speaking of your rear wall, you should aim to have about 2 ft worth of insulation or hangers on it. I would never go less than 6" thick of insulation on that wall.

- should I change the angles of the soffits etc?

Only if your RFZ ray tracing indicates that you should.

- is it ok for the air flow to go from the control room to the live room? The alternative is independent ventilation I guess, which would require two split systems and more holes in walls...

It is not okay. You'll need two mini split heads, one for each room. Then ventilation for each room as well.

- any recommendations for finding good wall angles with amray?

Personally I've always just manually ray traced in SketchUp.

Yes that's right, sorry it wasn't clearer! I hadn't seen the calculator and if I'm understanding it correctly then one layer of gypsum should be fine:

I would use two layers of gypsum. The MSM equations are tailored to each leaves sheathing being similar in surface density. Imagine this extreme example: Concrete wall as your outer leaf and an inner leaf being thin paper. The paper technically is in fact sheathing. It just has next to no surface density. Is your isolation going to improve much with the paper sheathing? No. The second layer of gypsum would increase your isolation at super low frequencies as well and those are the ones that are going to bother your family and neighbors.

Perhaps I can squeeze inner leaf silencers into the ceiling cavity if I do inside-out ceilings and make the OSB 16mm instead of 25mm.

I wouldn't do that simply because you would be compromising your MSM gap size. Also, working overhead is always a pain in the ass. If I were you, I would shift my control room back which would leave a space in front of your control room. I would put my return silencers there. I would put my supply silencers at the back of the room where you have them drawn now. The supply sleeve could penetrate up high on the wall which would supply nice fresh air for the mini split head.

If I do independent ventilation for each room can I split the ducts for the outer leaf penetrations after the silencer box or would I need to have separate inlet and outlet ducts for each room?

You could get away with having a total of 6 silencer boxes. 2 outer leaf boxes that would serve both rooms. Then, each room would have their own inner leaf boxes. So, your outer leaf boxes would split off and feed both rooms inner leaf boxes. Just remember, EACH silencer's purpose is to maintain the isolation of any leaf that has an HVAC hole cut in it's sheathing. So, any sheathing that has a ventilation hole cut in it NEEDS a silencer box.

Greg

Thanks Greg I really appreciate your input. And your additional words as well John. I've updated the design based on the feedback.

With the idea in mind to make the materials used for the outer leaf silencers have similar density to the walls themselves, I'm now thinking to build the silencers externally out of bricks. I haven't read about anyone doing this, but other than the complexity of waterproofing I can't think of a reason not to and it will save space too.

I realised if I have completely independent ventilation for each room I can make the control room registers smaller, and keep the live room registers the same size and get well under the 300 fpm. I guess the downside is multiple fans and extra holes but it seems a good trade-off.

Also with the smaller ductwork for the control room I can get the fresh air register above the mini split.

Please see the screenshots and let me know if you spot any problems.

Gregwor wrote:Also, you shouldn't be angling your actual inner leaf back corners. The angles you see in studio pictures is actually acoustic treatment such as bass traps. Speaking of your rear wall, you should aim to have about 2 ft worth of insulation or hangers on it. I would never go less than 6" thick of insulation on that wall.

I've now made the back wall around 16 inches thick. Not sure I can do 2ft without moving the sliding doors too close to the front of the room and getting bad reflections from them. I'll have to look into this further.

If I were you, I would shift my control room back which would leave a space in front of your control room. I would put my return silencers there.

I can't do this very easily as that side of the building will be almost completely underground. Hopefully the exterior silencers solve the problem.

Thanks,
Roland.

The cavity resonance in your double leaf system is far too high for decent low frequency transmission loss...

I may have missed it, but what is the lowest frequency at which you'll need a TL of 58db? Because right now your cavity resonance is 43.86hz, which means you can only expect decent isolation down to only about 80hz in reality. (we want the cavity resonance to be half of the desired lowest frequency requiring decent isolation) If that's all you need then ignore me and carry on... but I thought I'd point it out just in case.

Paul

Paulus87 wrote: I may have missed it, but what is the lowest frequency at which you'll need a TL of 58db?

Thanks Paul. I didn't specify, but I think I'd be fairly happy with 58db at 80hz. 60hz would be nice though... Looks like if I increase the gap to 180mm that would be achieved. With double layer of gypsum as well the calculator looks like this:

I don't fully follow your drawings but from what I can see, your silencer boxes only have what might be equivalent to 2 baffles worth of direction changes. You should have at least 3. Heck, if you're going for that much isolation at those low frequencies, and you don't want your silencer boxes to be the weakest link, you should consider making them out of some heavy material (like brick as you've mentioned) but also, you have to realize how these work --- to achieve insertion loss (this is how many dB they are going to attenuate), you need big cross sectional area changes. You should be aiming for 4 times the CSA in my opinion to match your MSM isolation. Also, I would recommend at LEAST 4 baffles. That means these things are going to be massive. But that's what it's going to take in my opinion. Most people around here are building rooms that are achieving like 50db of isolation and that means regular silencer boxes (1" MDF, 3 baffles and twice the CSA for the silencer box path). You're going for at least 10dB more than that. I think you realize how much more difficult it is to get that extra 10dB of isolation. Insertion loss is even harder.

Greg

Gregwor wrote:...to achieve insertion loss (this is how many dB they are going to attenuate), you need big cross sectional area changes. You should be aiming for 4 times the CSA in my opinion to match your MSM isolation. Also, I would recommend at LEAST 4 baffles.
Greg

Thanks again Greg. Sorry my descriptions aren't clear - please let me know what's not making sense and I'll try to explain it better.

So for CSA, if my duct size is 40cm x 40cm, that's 0.4x0.4 = 0.16sqm. I need 4x so 0.64sqm. Is it correct if I make the baffles about 1.2m high and 0.55m deep similar to the screenshot below?
Thanks,
Roland.

That makes more sense! As long as the inside air path (take duct liner into consideration) is the correct size, that's what matters.

I can see that you're handy with whatever program you're using, but it seems to lack necessary detail so I'd recommend drawing things up in more detail before you build it in real life. For example, when building a silencer box out of MDF, having the exact dimensions of every piece of MDF allows you to easily make cut sheets so that you minimize waste and buy the exact amount of material that you need. I feel that this is important at every stage of the build.

Cheers!

Greg

Thanks again Greg!

I'm using Blender. It's a very powerful program and I know some parts of it fairly well and others not at all. One part I am quite familiar with is the scripting system, and I've been vaguely wondering about using it to model reflections in 3D though that would require a lot more learning and time I expect!

I'll definitely take your advice to draw it in more detail and will update this thread when I've done that.

Thanks,
Roland.

Roland,

I spent about a month getting good at Blender about 1 year ago. I was very disappointed after I went to actually draw up some studio stuff and not just random objects that I had created following tutorials. Maybe I just didn't know what the hell I was doing, or the problem does exist (I know they do a lot of updates just like Reaper which I'm a massive fan of). The problem is that after a ton of fighting and research, I found no way to change the ruler/grid to be standard construction measurements such as feet and fractions of inches. Blender is amazing, but again, totally unusable unless there is an easy way to use something other than their proprietary unit of measurement. Thoughts?

Greg

I've always used the default units, but I found a page that shows how to make it use Imperial units in the latest version of Blender. See https://www.katsbits.com/codex/units/ They've changed the UI quite extensively with version 2.8 and I think it's an improvement, so best to get the latest version.

+1 for Reaper too

Regards,
Roland.