tiny voice booth/edit/music production/mixing room

Hi everybody, This is my first post on this forum as a long time lurker and dabbler on this and other audio forums. My wife and I have recently decided (after a little arm twisting on my part...) to build out one of the spare rooms in our house to be a space where she can work (read: she can actually make money) and I can get back into making music (read: I can pretend to follow my rockstar dreams...). My wife works in radio and has been picking up work as a voice over for advertising agencies and also edits a few different shows and podcasts. She's getting sick of driving into town for a 30 second voice-over and wants to be able to work from home. I am an ex live audio guy who has previously dabbled in studio building, love to record, produce and mix personal projects and have taken the odd paid project also. We recently bought a 3 bedroom house in a suburban area with sub-tropical jungle mixed in for good measure. The room we're converting was intended as a study. Essentially what we hope to achieve with this studio build is enough isolation so that my wife can record voiceovers without crickets, cicada's and birds as ambience. It is a place that we can personally work in, but would rarely expect clients on premise. As a secondary, but also important goal, I would like to be able to use the room to record acoustic guitars and vocals, mix and comfortably edit in there. I'm not expecting to be able to mix metal at 98dbA past midnight without annoying the neighbours, but I'd like to think I'd get away with 90dbA. We're aiming at a practical and achievable result rather than an ideal one. The space is 2.4m tall x 2.8m long x 2.4m wide so it's comfortably big enough for a vocal booth, but it's going to be a stretch for everything else. Acoustic goals: - good isolation from the outside world - dry enough for voice-overs - bottom end trapped enough for mixing - enough life in the room to enjoy being in there and recording the odd acoustic guitar or electric amp. I recognise that the dry enough for voiceovers and a bit of life in the room are competing goals and I think if the room has issues with reflections for the VO's then I might mitigate using a mic shield. I can foresee facing the back of the room to record voice and vocals and obviously face forward for mixing. This will avoid the obvious reflection from the front soffits. At the moment, the total budget for building out the room (no gear) is maxed at $4k AUD. Ok here's some simple 3D modelling I did pretty close to the measurements for the spousal presentation: Ok - here's how the room currently sits in the world - the wall with the big window in it is to the outside of the house - the wall with a door in it is the only new wall in this project and closes in what was previously an open room into a hallway. - the wall at the back is our ensuite and the wall at the front is our main bathroom. - the floor construction is timber floorboards directly onto floor joists - the ceiling is currently plaster with charlie-fluff (blow-in) insulation on top I'm going to outline my basic plan here in as logical fashion as I can. So far I have only framed the wall that has a door in it and ordered some MLV and that's as far as I've gotten. Floor The current floor is hoop pine floor boards straight onto the floor joists with no insulation so this is a major weak spot for acoustic isolation from the outside world. My current plan is to lay down some 5kg/m2 mass loaded vinyl (3mm thick) over the current floor boards and then layer on that some acoustic underlay and then wooden laminate flooring on top. The plan was to do this before the new wall plaster layers go up so that the new flooring overlaps underneath the wall. flooring questions: - do you think this flooring system on it's own will achieve enough isolation for our goals? - another thought was to add some yellow tongue into the mix (chipboard-like dense flooring material) in between the MLV and underlay for extra mass. It's reasonably cheap, but the floor would gain an extra inch in height. Do you think the extra layer would be worth it? Rear Soffits The rear soffits are essentially just a frame to hold acoustic treatment in place and also to hide some ventilation iso-boxes. In the plans I currently have a large QRD and the rest of the frame is full of knauf earthwool acoustic insulation. On the angled sides of the soffit my current thought was to have timber slats to breath some life back into the room and perhaps higher the Q of the rear absorber, but I haven't put any brainpower into working that out yet so it might yet be just fabric across a frame. rear soffit Q's: - I have read that it's not great to have a QRD within a certain distance of your ears or a microphone, perhaps this is one of the cases where the room is just too small? Maybe a 3D diffuser could be a better option. I have previously experimented in control room with switching out a QRD with absorption and I really appreciate how a QRD smooths out the frequency response and in my experience cleans up the stereo image so I'd love to keep it if I can. Front Soffits: Ok, here the acoustic rubber hits the road so to speak. I would like to try soffit mounted near-fields. This is possibly the most ambitious aspect of the design and this would be the first studio I've set up with soffit mounted mains so there is risk. I do not own any monitors at the moment and I will need to work that out before I construct the front soffits. What I'd really like is passive sealed boxes (no ports), but that seems really hard to find these days especially down the budget end of the market so I'll have to be flexible. The current plan for the front soffits is to build a hardwood timber frame (for weight and stiffness) and then attach 3/4 inch MDF sheet to the front with the cutout for the monitors. The monitor stands will be free-standing and inside the wall. I am planning to put a small vent in the bottom of the soffits to get airflow up to the monitors and I may possibly install 19inch racks at the bottom of the soffit also. There will be a vent into the ceiling space through an iso box perhaps with a small fan for extraction. Any space remaining in the front soffits will be full of earthwool insulation. font soffit Q's: - Am I being too ambitious here? I am confident in my construction abilities and even my practical experience in acoustics, but this is new to me. I hate having to deal with the corresponding bottom end dip from having your monitors off the wall and I don't like ports that are only good at 1 note. - Any thoughts on sealed monitors that are currently on the market or perhaps used? I don't trust active monitors as much because I know the processing that can go into them to overcome the limitations of the ported design. You can't just shove a sock in the port (I may have done this in the past :lol: ) and pretend it's sealed now. Realistically I can't see me being allowed to spend more than $2k on monitors so this is going to be tricky. If I won the lottery tomorrow I'd buy myself some ATC SCM12 Pro's. Ceiling I don't have much height in the room so the last thing I want to do is to drop down a cloud. My plan instead is to knock out the ceiling plaster, build a sealed box out of 3/4inch thick MDF that goes 270mm into the roof space, fill it with more earthwool insulation and face with open weave fabric. This should eliminate early reflections from the ceiling and beef up the low-mid trapping in the room. ceiling Q's: -anyone see any pitfalls with this approach? Perhaps a single layer of MDF won't be enough isolation from the outside world? I was hoping this would be mitigated by all the insulation. Another thought was to line the box with MLV. New Wall and Door The new wall I have framed out with 90x35mm studs like this: You'll notice unlike the CAD design we ended up moving the door frame into the middle of the wall rather than being offset. Other than that it's as per plan. My plan for sealing up the wall is 90mm thick earthwool insulation and on each side a layer of 16mm thick fyrchek plasterboard, green glue and then standard 13mm thick plasterboard. The fyrchek plasterboard is a much more dense plasterboard than the standard stuff you can buy at the local hardware store. The door we have thankfully picked up from an old radio station and it's a professionally built acoustic door which is solid core and probably 100kg. I've put in a double stud with hardwood to hang it from. Some of their studios are still functioning and we were able to go and listen to how well the remaining doors worked. They didn't save the rubber seals for the old studios so I'll need to figure something out there. New wall Q's: - I haven't been able to find a reference for STC value specifically for a 90mm stud wall with 16mm acoustic plasterboard, GG and then 13mm plasterboard so it is hard for me to know just how well this wall is going to do. Anybody have any experience with the 16mm fyrchek? Existing walls This is where things get a little funky for me. None of the existing external or internal walls have any insulation (bloody QLD builders). There are two possible approaches I am considering - 1. Keep the existing 10mm plaster and add green glue, 16mm fyrechek, green glue, 13mm standard plaster (adds up to 39mm of plasterboard with 2 layers of green glue). 2. Rip off the existing 10mm plaster, fill the wall with acoustic insulation and then layer up 16mm fyrechek, green glue and then 13mm plaster. I'm currently leaning towards option 1. The back and front walls will essentially be covered by a soffit filled with insulation anyway so perhaps the gain from ripping off plaster and adding more insulation will be insignificant. The side wall will be mostly covered by soffit except for the window anyway. existing wall Q's: Do you think approach 1 will be enough isolation for us to reach our acoustic goals? Window The side window is existing and it's an aluminium frame window that seals reasonably. In a perfect world that would not be an opening window, but it is. My current thought would be to add another layer of glass on the inside to cover the entire frame. I might even be able to get laminated glass perhaps 5mm thick. We'd not be able to access the opening window again, but it would be well sealed. window Q's: Anyone got any suggestions on how to deal with the existing window? Thanks for reading and also I'm thankful for such a forum as this. Look forward to any criticisms and advise.

Welcome! For the bad news first: - your room is almost a cube and unfortunately that is the worst possible shape for decent acoustics :cry:

but I'd like to think I'd get away with 90dbA.

C weighting is what we need to worry about here -- simply because lower frequencies are the ones that we struggle to isolate.

The space is 2.4m tall x 2.8m long x 2.4m wide

Go to Bob Golds Room Mode Calculator and type these dimensions in: - 1.1w / h < l / h < ((4.5w / h) - 4): Fail - l < 3h & w < 3h: Pass - no integer multiple within 5%: Fail (ratio2 = ratio1 * 1) You can see that it fails 2 out of the 3 tests. I'll touch on this topic again in a second.

good isolation from the outside world

How good is "good" for you. With typical walls you're going to get around 30dB isolation max. If you beef up the existing walls and such, you aren't going to get that much better due to mass law. That is why it is common for people to go all out and build a room in a room because we aren't limited by mass law. Your budget and limited size kind of takes this option off of the table. If you need more isolation, it might make sense to use iso clips and hat. Your window is a major issue for outside noise getting in though. Is it possible to remove the window or even just block it from the inside so it still looks like a functional window from outside?

- dry enough for voice-overs - bottom end trapped enough for mixing - enough life in the room to enjoy being in there and recording the odd acoustic guitar or electric amp.

Well bass trapping is going to be EVERYTHING in this room. You really should strive to bass trap all 12 corners of the room. Using some variable treatment might be a great option for you if you want a more dead room and be able to flip some treatment and have it more lively.

My current plan is to lay down some 5kg/m2 mass loaded vinyl (3mm thick) over the current floor boards and then layer on that some acoustic underlay and then wooden laminate flooring on top.

Unless you have very very very limited space and still need mass, MLV is a very expensive way to get mass. There are only a few cases where I would suggest using MLV.

do you think this flooring system on it's own will achieve enough isolation for our goals?

Figure out how many dB of isolation you require then punch in the surface density of your floor into the mass law equation to see how it will perform.

another thought was to add some yellow tongue into the mix (chipboard-like dense flooring material) in between the MLV and underlay for extra mass. It's reasonably cheap, but the floor would gain an extra inch in height. Do you think the extra layer would be worth it?

If you need the extra mass, then yes, I would use OSB (that's what we call it here) on the floor. I doubt you're going to need the MLV unless you plan on spending a small fortune putting MLV on every square millimeter of the room. Remember, whatever wall/ceiling/floor has the least amount of surface density will determine your max isolation. There is no point in having a super beefy floor if your ceiling isn't equally as beefy.

The rear soffits are essentially just a frame to hold acoustic treatment in place and also to hide some ventilation iso-boxes.

Your room is already pretty small. Do you have the ability to put the silencer boxes above the room? What is above the room?

I have read that it's not great to have a QRD within a certain distance of your ears or a microphone, perhaps this is one of the cases where the room is just too small?

Correct. If you want diffusion you're going to have to use polys.

I may possibly install 19inch racks at the bottom of the soffit also.

This will eat up very valuable bass trap space. I would custom build a tiny desk and put racks down on the sides of it.

Any thoughts on sealed monitors that are currently on the market or perhaps used?

They receive a lot of love and a ton of hate but with a sub, I LOVE my NS10s. You can buy them used pretty cheap.

-anyone see any pitfalls with this approach? Perhaps a single layer of MDF won't be enough isolation from the outside world? I was hoping this would be mitigated by all the insulation. Another thought was to line the box with MLV.

This takes us back to your small room size with two of your dimensions being identical. If I were you I would rip the plaster off and install inside out ceiling modules (you can see lots of examples of this on the forum). On the modules you can apply whatever sheathing will get you your desired isolation. Also, a ceiling filled with insulation will be great for your room. Fabric over the insulation and it will look beautiful too. This could give you an extra 0.1m of height which still won't get you to pass the tests on Bob Golds site but the fact that isn't not IDENTICAL to the other dimension is a good thing.

1. Keep the existing 10mm plaster and add green glue, 16mm fyrechek, green glue, 13mm standard plaster (adds up to 39mm of plasterboard with 2 layers of green glue).

The biggest issue with this is that you're going to end up with all your walls being plaster which sounds like crap as we all know. So, you'll have to put a bunch of treatment panels up.

Do you think approach 1 will be enough isolation for us to reach our acoustic goals?

You need to figure out how much isolation you need in dB.

Anyone got any suggestions on how to deal with the existing window?

Box it in from inside. Put desiccant in the cavity then cover it using whatever sheathing will offer you the same surface density as the rest of your walls. ---------------- For your walls, I would rip off the plaster, beef up the walls from the inside (green glue, sheathing, cleats). This will allow you to have treatment fixed in the framing which opens up a lot of possibilities. Also, this can give you close to another 0.2m in both directions which is good -- bigger room = better, different dimensions = better! Greg

Hi Greg, Thanks very much for putting so much into your answer, much appreciated! You raised quite a few points so I'll walk through them all and see where we end up. - Cube room - I said I had a 2.4 high x 2.8 long x 2.4 across room, but this was a little misleading because I had planned to do exactly as you said and rip the plaster out and build essentially an MDF box above the ceiling to enclose a bunch of insulation to perform as an absorber. So when I'm finished the floor I'm going to loose around 6cm height and I'd planned to build out the ceiling box to around 26cm tall so we'd end up with real dimensions of around 2.4 x 2.8 x 2.6 which looks nicer in Bob's calculator. Honestly I had just assumed being such a small room that the room modes were going to do their thing and I'd just have to bass trap as much as I can. Isolation - For our isolation goals, I'd love to achieve a drop from outside to inside of around 40db if I can. I'm essentially aiming for a 30db noise floor internally so that we can record clean voiceovers. Initially the primary goal is to have my wife work from home without being hassled by noise coming in. Typically our neighbourhood suffers from an abundance of idyllic wildlife sounds (read: bloody noisy Aussie birds) however when you fire up a spectrum analyser it's mostly all happening up high. There was a crapload of cicada's singing along this morning up around 10k and the meter was reading around 65dbc. That was a pretty bad morning so if I can achieve 40 then the noise inside is a tidy 25. In terms of bottom end issues there is the occasional train coming past from around 400m away, but it's only a few times a day and we can get away with a retake if we cop that. Also the odd car goes down the street in the earlier morning, but for the most part it's a pretty chill neighbourhood. On saying all of this, my plan was super dense acoustic drywall (16mm) on top of the existing rubbish 10mm and then another 13mm standard layer on top all with green glue in between. Perhaps I really need to go two layers of the 16mm acoustic drywall. I haven't used iso clips in a build before so I will look into the cost of it. I was being a little lazy in just wanting to throw up multiple layers of drywall with green glue. Do you know if it's typically expensive? I will do some more research and see if the drywall brand published any test specs of their dense acoustic drywall. If so, I can make a proper comparison between a few layers with GG and the iso clips. Floor - I think for the existing structure, this is currently the biggest weak spot in the room. I managed to get enough MLV for the entire floor for $240 (one nice thing about a tiny room) so I think I'll lay it because I now own it. Out of the 4 walls only one of them is to the outside world so there is already is already a degree of transmission loss from the outside world except for the one wall. Out of the 3 remaining walls, 2 are to bathrooms that have an airtight waterproofing layer in them already and also tiled from floor to ceiling for free extra mass :lol: Window - this might have to be a work in progress. I may eventually be able to get a double studio window in, but initially the budget will be super tight to do it properly. My wife really thrives off the natural light so I'm afraid she'd be only too happy to sacrifice proper isolation for some daylight and not to feel caged. Bass trapping and vents - The entire ceiling will be 26cm deep of insulation trapping behind some fabric and trim so I'm feeling good about that. The back of the room will all be trapping behind the timber frame. You're right in that I struggle to fit any ventilation into those rear traps. My plan for ventilation was to use a small fan to push in air from the hallway outside the studio in through a silencer out of a vent at the bottom of the rear trap. I'd rather take air from lower in the wall than the ceiling just because it gets a lot hotter at the ceiling than at the floor and QLD is typically way too hot. I need to size out how big I'll need the vents. It's not going to be perfect, we may just have to open the door and air out the room from time to time. We have aircon in the house, but only single wall units, not a ducted system. Was planning to take advantage of the already cooled air. To get air out of the studio I was planning to put vents into the bottom of the front soffits and then have air go up through the soffits past the monitors and then into an iso box into the ceiling. Plaster sounding like crap - Couldn't agree more, the rooms that i've really enjoyed have always had loads of timber around. Even just that cheap pine vj lining seems to do so much for the tone of a room. In this particular room, I'm not sure how it will effect everything because most of the plaster will be behind all the bass trapping. There's not that much plaster on the walls that is even exposed. Do you think that plasterboard will effect the tone detrimentally even behind the treatment? Front soffits were to be thick MDF and rear traps I was thinking of lining with timber slats. Also there'll not be any plaster on the ceiling either. Thanks again for your feedback.

I'd love to achieve a drop from outside to inside of around 40db if I can.

With two layers of 15mm fire rated drywall, in a perfect build mass law says you could expect 32.93dB of isolation. You can see how unfriendly mass law is by figuring out how many more dB of isolation we can achieve by DOUBLING that amount of drywall. So, with 4 layers, mass law says we will expect only 37.29dB of isolation. I doubt you want to fork over the money for 4 layers of drywall. Plus that is a LOT more work. I haven't done the math for it, but since you'd be beefing up the mass from the inside, a few things to consider: - is the drywall that you'd be beefing up heavy fire rated stuff or is it the cheap ultralight drywall that everyone seems to be using these days? - the framing material cannot be beefed up. So where there is a stud, you're going to be relying on the surface density of that wood.

I haven't used iso clips in a build before so I will look into the cost of it. I was being a little lazy in just wanting to throw up multiple layers of drywall with green glue. Do you know if it's typically expensive?

Iso clips are pretty expensive and it does need to be installed with a lot of precision. My friend has a room where he used clips in a duplex and he can play his acoustic drums during the day without complaints. Granted he plays light jazz music. If high frequencies are your biggest concern, clips might work great for you! I'm just not sure how you would use clips on an inside out ceiling.

If so, I can make a proper comparison between a few layers with GG and the iso clips.

I'm confident that there is a way to calculate the transmission loss provided by clips, but it's not something I'm up to tackling just yet :|

The entire ceiling will be 26cm deep of insulation trapping behind some fabric and trim so I'm feeling good about that.

The corners of your room are where you're going to get your bass trapping from. But yes, the ceiling filled with insulation will help for your room no doubt.

Was planning to take advantage of the already cooled air. To get air out of the studio I was planning to put vents into the bottom of the front soffits and then have air go up through the soffits past the monitors and then into an iso box into the ceiling.

This should work.

Do you think that plasterboard will effect the tone detrimentally even behind the treatment?

Not at all. Plasterboard actually has some absorption characteristics to it and in some situations it's great to have some exposed plasterboard. Greg

Hi Greg, drywall - yes it's the 16mm heavy fire rated stuff, not the cheap stuff. Are there any easy-ish to use mass law calculators kicking round the web? I couldn't find any, but I haven't spent much time searching yet. I may have to brush up on my maths. When you say I could expext 33ish db of isolation using 15mm heavy drywall - were you calculating just for the drywall? Or a wall system with insulation and plaster on the other side? corner traps - the ceiling trapping runs all the way out to the walls so that covers all the ceiling corners reasonably deep and the front and back soffits cover the vertical corners so the only weak spots are the floor to wall corners. Hopefully we can live with that. To keep the acoustic goals in perspective, this build makes money out of being a voice over and edit booth for my wife and I get to have fun writing music and mixing in here as a bit of a bonus haha. Not to say I want to compromise on being able to properly hear in there for mixing, just that I wouldn't be able to justify doubling the budget or making the space cramped for only my own purposes. Thanks again for your time, I do appreciate it!

Ok my Math is a little rusty, but let me just work through it here and maybe someone will point me right: TL = 20 log10 (ms f) - 48 Ok for 100hz and 2 layers of 16mm fyrchek with a combined mass of 25kg per square meter 20 * (3.39794000867) - 48 = 19.9588001734 db Sound about right? for 200hz 20 * (3.69897000434) - 48 = 25.9794000868 db Is this right?

TL(dB)= 20log(M) + 20log(f) -47.2 Where: M is the surface density of the panel (mass per unit area (kg/m²) ), and F is the center frequency of any one-third-octave measurement band OR The empirical version of Mass Law that give you the isolation for the entire spectrum, instead of just one frequency: TL = 14.5 log (M * 0.205) + 23 dB Where: M = Surface density in kg/m2

were you calculating just for the drywall? Or a wall system with insulation and plaster on the other side?

Just the drywall. Greg

Thanks Greg, that helps clarify.

Finally got the acoustic door fully hung tonight and it was not an easy task. I'm guesstimating it weighs somewhere between 120-150kg. I have a double stud on the hinge side with one from hardwood. Wall is 90mm wide. No door stops installed yet as I will first buy the rubber seals that the door will close against and that will give me an idea on how much clearance to give between the doorstops and the the door. Things may slow down for a little while now while the budget catches up with spending so I'll likely take care of some of the cheap details like pre-wire for the mains and lighting as there's currently no room or hallway lighting which is getting old. Next step after this is to rip the existing ceiling and wall plaster out. Acoustic design-wise I'm still trying to get a handle on how much the modal response of the room will shift with a fair percentage of the front wall being soffited. The reason this matters to me now is because I'll be installing a false ceiling and depending on the roof line I may have some flexibility as to how high I can push the actual ceiling boundary. I'm still doing a lot of research on acoustic treatment options and approaches to take.

Got a bit of demo done on the weekend - pulled out all the old drywall except for the ceiling. Sorry for the terrible photos, there's not a great angle in such a tiny space without a wide lens haha. Will have to crack out the real camera. This week in my spare after work time I am planning to seal up a bunch of the air gaps and clean up all the old studs ready for new drywall. Then on the weekend it's time to rip out the ceiling and try and work out how much space I have above the ceiling line to build my cloud structure. My current plan is to frame up some supports in the roof and then lift pre-built inside out ceiling panels on top of the frame and secure. In between all of this I also need to get all the electrical run.

Pulled out the existing ceiling last night. Now that I can see the existing ceiling structure I can now figure out how to work around it.

That's awesome! If you remove those furring strips, you have a lot of access to the attic. Greg

Hi Greg, That's exactly what I've done and I'm now raising the walls past the old ceiling line to gain space for bass trapping. These boxes will provide part of the support for the ceiling panels to sit on top of. These boxes will have another layer of OSB inserted into them with a layer of green glue in between and plenty of sealant around the outside. The drywall for the walls will extend all the way up to this hidden ceiling. Once the new ceiling is up I will re-install the old ceiling battens and then fill the space with insulation batts and then face with fabric and then varnished wooden slats for the purposes of better bass trapping and more HF energy staying in the room. Unfortunately this use to be the corner of the house before it was extended so there is a lot of extra roof structure to work around which requires some "interesting" carpentry work. This has got me thinking about how inevitable the flanking noise will be for this build. I can't see much way around it aside from upping the mass. Over the weekend before deciding on the false ceiling height, I recalculated and check the room dimensions based on layers of drywall and flooring. Length - 2635 Width - 2180 According to bob gold's calculator, a 2900 ceiling height has a nice modal spread and passes the BBC tests. Unfortunately, Because of the roof sloping downwards towards the side of the room, I can only achieve 2900 for half of the room. So that's what I've ended up with. Unfortunately the reduction in ceiling height goes across from left to right, not front to back. Please correct me if I'm wrong, but as a compromise I made the assumption that having a ton of trapping is going to work out better for me than having a symmetrical ceiling boundary. Averaged out, I think the ceiling boundary will end up being at around the 2725 mark which isn't great. Ceiling trapping for half the room is 480mm and on the lower side will go from 180 all the way up to 480. Thanks!

Symmetry is important for a good mixing room so I'm skeptical about that, but having a higher ceiling is always great. You seem to have a good grasp on things. You've clearly thought about the consequences and decided to go forward with the design. All we can do is advise and bounce options off of ya! I'm sure the room will end up working great for you! Thanks for the picture updates! You're making great progress. Greg

Thanks Greg, Yes would have been nice to have a symmetric structure, but happy to work with the cards I've been dealt. Thankfully it should really only effect the low end which won't hurt my imaging too much I hope. Feels great to be making decent progress of late. Thanks for all the advice, I do appreciate it.

I managed to get the first couple of ceiling panels installed over the weekend. Also built a silencer box on the outside of the extended wall. Many more to build, but it feels good getting a start on it.

Been slow progress, but things are moving forward. I am about 99% finished boxing up the ceiling, I just have a couple of panels that still need doubling with green glue in between: I've done a first round of sealing up tiny gaps with sikaflex so the ceiling would be close to airtight, but I plan on doing another round to make sure absolutely everything is airtight. Starting installing sealed boxes to go behind the switches and outlets and have started the pre-wire: These boxes will also be filled with insulation, closed on the front and sealed to the gyprok when it's installed. And yellowtongue flooring on top of mass loaded rubber is now in place: I will also fill up the gap around the outside with sikaflex. I tried to leave a couple of mm tolerance around the flooring for movement and weather changes. I figured flooring first and gyprock over the top of the flooring again with maybe a 1-2mm gap filling with sikaflex to keep things airtight but mildly flexible.

Wow. That's a lot of hard work and it looks great! Excited to see more progress pics. I think showing your build in more detail (pictures) would help people in the future. Again, good work! Greg

A little more progress over the weekend, but still a bit of tidying up details before plaster can go up. This is the front wall behind where the monitor soffits will be. timber in the middle is for screens to be mounted to the wall. The electrical going horizontally is power being fed into a switch and then to outlets for the audio monitors. The same switch also powers another socket at the back of the room that will supply a ventilation fan pushing air into the room through a silencer duct. The idea is that if you power up the monitors then you've also powered up the ventilation fan. There is ventilation ducts that will go up into the soffits and then past the rear of the monitors into outlets in the ceiling that also push through another silencer duct each. Also completed another silencer to go in the ceiling before we hang the drywall. It's heavy and has been designed to fit through the manhole so I might have to enlist some help to get it up there. This is an in progress shot, I didn't get one of the closed up box I put my iphone in one end, sealed it up and played music through it. Not very scientific but gives me an idea on how effective or not my silencer is. Works really well on the top end, but I can still hear a fair bit below 250hz through it. Could have been the phone actually vibrating the structure itself as it was sitting inside but I guess I'll find out! Worst comes to worst I can build an extension to it at some point. The whole thing makes a great low pass filter.

This is the front wall behind where the monitor soffits will be. timber in the middle is for screens to be mounted to the wall.

What type of material is that? It looks like particle board. I recommend OSB. You don't want your screen pulling out of it!

This is an in progress shot, I didn't get one of the closed up box

I don't see any caulk in the joints. I assume you applied a bunch around the outside at least?

Works really well on the top end, but I can still hear a fair bit below 250hz through it.

The low end attenuation is mostly obtained through impedance mismatch. That is when the cross sectional area doubles (or more) in size. Your inlet/outlet look to be roughly the same size as the path throughout your box. Care to share your measurements? Greg

The particleboard looking stuff is yellowtongue flooring material. Very dense and pretty dang strong. I’ve using it a bunch because of its density although I’m just using it because it’s strong and I have some left haha. I haven’t built silencer boxes before and I didn’t realize that impedence mismatch was what attenuated the low end. Aaaah always something to learn! I can’t remember the measurements off hand and that thing is sitting in the ceiling now. I’ll have to climb up with a tape measure. I have the space in the ceiling so I could potentially add another section if I need to. There will effectively be an impedence mismatch where the ventilation opens up into the front monitor soffit. Can you recommend any reading on the impedence mismatch? Thanks again.

There will effectively be an impedence mismatch where the ventilation opens up into the front monitor soffit. Can you recommend any reading on the impedence mismatch?

For sure there is one as it enters the room. Basically, the inside path of the box should be at least twice the size of the duct feeding the box. You can see in the image below that like any broadband acoustic panel or a bass trap, the deeper the insulation (in this case, duct liner) is, the better it is at attenuating low frequencies: And you can see here how the insertion loss is directly proportional to the cross sectional delta: Greg

Thanks Greg, that's so helpful!

Despite work being very busy at the moment, I'm still managing to get quite a bit done in the studio. I really can't get this done fast enough. My wife is getting plenty of voice work doing reads for government ads around the coronavirus outbreak and I knocked up a makeshift cupboard booth in about 10 minutes with zero isolation. Currently running an SM7 as it is pretty decent at being direct into some JLM baby animal pres into a zoom recorder. So just outside the studio I put a downlight into the hallway as now there's a new wall blocking the window it was getting pretty dark. As you can see, the first layer of drywall is up. I need to confess that I'm an absolute rookie at doing drywall so it's all trial and error for me. Figuring that I want the most rigid wall I can get for acoustic reasons, I used both screws and drywall glue. The mud around the joints and edges is there purely to seal up the wall and make everything airtight as there's another layer with green glue to go over all of this. Also it gave me an opportunity to get a feel for mudding to give me the best opportunity to get the final drywall layer right. Something tells me i'm going to be doing a lot of sanding! :shock: The product is 16mm Knauf FireShield with a weight of 13kg per sq meter. Because it's a fire product, it has fibreglass in it which makes it slightly more annoying to handle than standard gypsum as it can make you a little itchy if you rub cut edges on your skin. This is my nightmare window that you face as you walk in I haven't even finished the first plaster layer yet and I can hear the isolation ramping up with each sheet and as a consequence my ears keep coming back to the window. I will definitely have to invest in a proper window. Front wall with wiring for soffit mounted monitors and desk. Back corner up to the ceiling modules Everything from the roof truss up will be above the ceiling line and filled with insulation. I am not planning to plaster in the ceiling modules as I need the trapping space, any stray noise would need to make it through a foot of batts and also it'd be a real pain of a job hahaha. I still need to penetrate my new silencer box into the space about the right hand side soffit and then plaster around that so lots of work to go before I can start on the second layer of drywall. Never ending!

You're working fast! I'm impressed! I'm no expert with drywall but I'll share what I know. For mudding the drywall, the key is to use the right stuff and to apply thin layers and trowel is as close to a finished product as you can. For your first layer, use a joint compound that is designed to glue tape down. Again, this can be a very thin coat. Lightly sand it to get rid of any huge bumps but you don't have to worry too much at this stage. For the second, third, fourth, etc stages, use a "light sanding" type of mud. This stuff isn't as strong so it's very easy to sand smooth. Using your trowel, apply a thin layer of mud and take your time to make it as smooth, clean and awesome as you can. If there are voids, try to fill them but don't worry if it's not happening. The less mud you have on means the less sanding you have to do. Literally, you should only have to sand a handful of swipes with some 220 grit. This is evident when you watch a pro mudder just swipe their way across the wall a few times and it's done. Add as many thin layers as you need to get the finish you're after. Typically a total of 3 layers should yield an awesome look. Sorry in advance if my advice is not great. Greg