Production/Mixing Control Room Shed Conversion

[namesakeAR]

Kia ora Everyone!

I'm a Producer, Mix Engineer, and Pro Audio Developer/Technician from Wellington, New Zealand. As the subject line states - I am looking to convert the shed in my backyard to a multi-purpose control room for my musical endeavours! After extensive reading of this awesome forum and abroad, I am starting to come up with some semblance of a plan - and would greatly appreciate any and all advice/feedback/critique.

PURPOSE

The purpose of this control room is to be able to track the likes of vocals/guitar/bass/percussion (tambourine, shakers etc), playback, and mix without external nuisance (or me becoming one to others!). My working hours will be the usual 9am-5pm grind, at which time the suburbia I live in is especially quiet (please read on for actual readings). My current mains are Neumann KH-80 DSP 4" monitors, through which I have set a playback listening level of 75dB.


CURRENT SITUATION

Currently, the shed has bare frames internally and mismatched external cladding comprising of Steel Bevelback Cladding (three walls), and Hardies Fibreboard Cladding (one wall). The roof is pitched and finished with Corrugated Iron. There is a single car garage door installed which I plan on removing and replacing with studs, the door, and more of the Steel Bevelback cladding. The flooring/foundation is thick concrete, I have no idea how deep it goes below ground but above it measures at 35cm. There is already an existing room within the shed that functions as my workshop, and therefore has to remain as is - one of its' walls creates the boundary for the proposed control room (the photos I took were too large to upload, so I have made them available through my google drive).

t.ly/1xe1E (LINK)

The hard boundary dimensions are:
Length: 477.5cm
Width: 346.5cm
Height: 224.5cm (more on this one later)

The internal dimensions (interior side of framing) are:
Length: 458.5cm
Width: 327.5cm
Height: 224.5cm

Room Mockup 1 - current.jpg

Room Mockup 2 - current.jpg

Room Mockup 3 - current.jpg

Room Mockup 6 - current.jpg

I understand that this is quite a small space to operate with, but it's the best I can do currently! This shed sits along the right-side edge of the backyard, with the closest neighbouring house approximately 10metres away. These neighbours have small children, I have measured a current maximum of 60dB SPL with the children playing in the backyard - the average for the duration of time in the day that I plan to use the studio however is around 35-45dB SPL.

I plan on this build being very gradual, and as such, have no set budget - although I would like to stay under $10,000 NZD. My father used to be a carpenter so we will be doing the majority of work ourselves, I have access to trade pricing through my part time job, and plan on outsourcing the electrical to a family friend for a slightly discounted rate!

On to the 'plan'...


PROPOSED PLAN

I have come up with two options for the build, one of which would include resilient channels affixed to the existing studs to maximise room volume, and the other would make use of a 'room within a room' with a sound lock. From an isolation stance, it is evident that the latter would be superior - however, with the limited space I have to play with I wonder if the benefits outweigh the cons? Any sound transmission reduction >= 40dB would be fantastic, but realistic?.. Irrespective of which route taken, the plan is double drywall layers with the electrical surface mounted to the interior of the wall to reduce flanking via holes cut for outlets. The only sizeable hole would be for a patch bay connecting through to the workshop (which is where the amps will stay).

Here are some images of what decoupled walls could look like - this particular model would leave my with an area of 412cm x 303.5cm x 204.5cm (L x W x H):

Room Mockup - Decoupled Walls 1.jpg

Room Mockup - Decoupled Walls 2.jpg

Room Mockup - Decoupled Walls 3.jpg

Room Mockup - D.W Framing 1.jpg

As previously mentioned, the potential height is finicky - the roof itself goes from 253cm to 278.5cm, but there is a load bearing beam at 224.5cm which limits my ceiling from going any higher! I cannot seem to come up a clever way to elevate the ceiling height (considering the likes of Johns' inside-out drywall technique) without this beam being a potential source of leakage. I don't mind the beam itself, and would be happy to have it sticking through the ceiling if that was viable from an isolation point-of-view.

Room Mockup - D.W Framing 2.jpg

In terms of ventilation, I am considering a 150mm inline fan ducting system (not sure whether positive or negative flow would be preferred), deadened by multiple baffle boxes and inline backdraft stoppers. The two external vents (one with the inline fan and the other to afford airflow) would be positioned over the workshop on the farthest side from the control room, with the internal vents on opposing diagonal corners of the control room ceiling. For heating and cooling I am looking at utilising a smart thermometer in the control room, alongside a heater of some description, and the fan speed of the inline fan. After setting temperature thresholds, the thermometer would send data to automatically turn the heater on/off or increase/decrease the fan speed. Has anybody used any smart tech such as what's proposed here to any affect??

Due to the multi-faceted nature of what my work calls for, I am leaning towards the dead-end live-end philosophy. Through all the calculations run through the amroc room mode calculator, it look like the Schroeder frequency of the room would be between 250-300Hz.


QUESTIONS

- Given the information provided so far, what are the groups thoughts on the two proposed options going forward? Should I champion room volume at the cost of isolation, or the
inverse?

- Is the importance of ratio's overemphasised? Given my limited footprint, should I aim for as much volume as possible if it is decided to build decoupled walls within the existing
structure? I have found a ratio of 1.9 : 1.4 : 1 (LxWxH) could work well and scores well with the bolt-area and bonello graph.

- Do any bright sparks have suggestions about the cursed low beam??

- With the foundation being thick concrete, a floating floor is not needed if it is decided to build decoupled walls within the existing
structure?

Many thanks in advance to you experts who dedicate your time to helping everybody on this forum, easily one of the best resources I have found! If there is any more information needed, or if I have inadvertently not followed the posting rules - please let me know.

Cheers!

[Gregwor]

Welcome!

Currently, the shed has bare frames internally and mismatched external cladding comprising of Steel Bevelback Cladding (three walls), and Hardies Fibreboard Cladding (one wall). The roof is pitched and finished with Corrugated Iron. There is a single car garage door installed which I plan on removing and replacing with studs, the door, and more of the Steel Bevelback cladding.

So, your cladding worries me. How do you plan to beef that up and seal it? I'd suggest removing it all, put 2 layers of thick OSB all around the building and then use whatever cladding you want. over that. This will provide you with a nice air tight outer leaf that has the surface density you need to achieve your desired isolation!

I understand that this is quite a small space to operate with, but it's the best I can do currently!

A closet is better than NO room! You're in a great position!

The only sizeable hole would be for a patch bay connecting through to the workshop (which is where the amps will stay).

First off, this hole can be addressed by using an S shaped piece of flexible conduit to run through the sheathing. After your lines are run through the conduit, stuff in a bunch of insulation and then squirt in like an inch or two thick of caulk. Seal up your 1 hole where your electrical goes in. For HVAC, you will probably need a drain too!

Given the information provided so far, what are the groups thoughts on the two proposed options going forward? Should I champion room volume at the cost of isolation, or the inverse?

For a few reasons, I personally would build the inner leaf entirely inside out. Specifically for acoustic treatment reasons. Clips and hat have a weight restriction which means you're going to be very limited for treating your ceiling.

- Is the importance of ratio's overemphasised? Given my limited footprint, should I aim for as much volume as possible if it is decided to build decoupled walls within the existing structure? I have found a ratio of 1.9 : 1.4 : 1 (LxWxH) could work well and scores well with the bolt-area and bonello graph.

Yes and no. If you have a very small space, I would recommend just using all of it even though the room ratio is not great. If you have a little wiggle room, I would move a wall a few inches here and there in order to get a better ratio. A better ratio means better modal distribution and ultimately better sound!

- Do any bright sparks have suggestions about the cursed low beam??

Frame around it. What I mean is, make your inside out ceiling high where it can be high and have it drop down around the beam. Your inside out ceiling doesn't need to be inside out right there. It could just have drywall or whatever mounted to the bottom side of the joists. Just make sure you have an appropriate gap between the bottom side of that beam and your sheathing. Also, fill the cavity with loosely filled insulation!

- With the foundation being thick concrete, a floating floor is not needed if it is decided to build decoupled walls within the existing structure?

Correct.

Has anybody used any smart tech such as what's proposed here to any affect??

HVAC is typically the most confusing and difficult part of designing a studio. You mentioned a heater. What about air conditioning for warmer seasons or when you have gear running in there heating things up?

So, typically you have one of two HVAC designs:

One being a ducted system where the air handler is moving your required CFM of air in and out of your room (being about 6 or 8 air changes per hour). Then, on the return air side of the system, there is a tap (these days often done through an HRV or ERV) and it gives you ~30% fresh air into your room. These designs are great but require large duct work and ultimately massive silencer boxes.

The other being a ductless system. A ductless mini split requires a "wall unit" that can also come in a conspicuous ceiling mount unit. These units will require a drain in or near your room. The cool, no pun intended, characteristic of this system is that the duct work to and from your room only has to move in/out the fresh air you require. That means that your duct work will move only ~30% of CFM compared to a ducted system. That means smaller silencer boxes! The wall units can easily do heating and cooling! Your ventilation (the 30% CFM mentioned before) can be done through an HRV or ERV provided the fans in the units can handle the static pressure of your silencer boxes.

Basically, what I'm saying is that your ventilation should either be on 100% of the time that you're in the room, giving you fresh air. Or, in the case of an ERV or HRV, they often have settings where they run for say 20 min per hour. With the timer setting, you'd have to ensure that it could give you the correct amount of fresh air per hour.

Great to have you here!

Greg

[namesakeAR]

Hi Greqwor!

Thank you for such a kind, detailed, and quick reply (and sorry for the delay in mine, we're in the last week of a nationwide lockdown and things are busy!).

So, your cladding worries me. How do you plan to beef that up and seal it? I'd suggest removing it all, put 2 layers of thick OSB all around the building and then use whatever cladding you want. over that. This will provide you with a nice air tight outer leaf that has the surface density you need to achieve your desired isolation!

This is a great point, and one that I had not given too much thought to previously! I was thinking of adding mass internally to avoid having to de/re-clad by cutting drywall or plywood to size in between the studs and fixing it in place - It sounds fiddly however. Are there other downsides to this that I haven't anticipated? it would decrease my outer leaf dimensions and give me less distance between the outer and inner leaf...
My father had an idea for the roof to use cellulose insulation between the corrugate and drywall (/plywood/whatever is decided to use) to mitigate any air gap between the corrugates ridges and added mass, thoughts?

First off, this hole can be addressed by using an S shaped piece of flexible conduit to run through the sheathing. After your lines are run through the conduit, stuff in a bunch of insulation and then squirt in like an inch or two thick of caulk. Seal up your 1 hole where your electrical goes in. For HVAC, you will probably need a drain too!

This sounds like a plan. The current plan, no pun intended, for electrical is to run lighting and misc outlets seperate from audio outlets - and to have all power come from the front wall to mitigate ground looping. I suppose the if I put the patch bay at the front wall and had the cabling run alongside the misc outlets cabling for that side wall before going into the adjacent room, there would be no problem?

For a few reasons, I personally would build the inner leaf entirely inside out. Specifically for acoustic treatment reasons. Clips and hat have a weight restriction which means you're going to be very limited for treating your ceiling.

Yes and no. If you have a very small space, I would recommend just using all of it even though the room ratio is not great. If you have a little wiggle room, I would move a wall a few inches here and there in order to get a better ratio. A better ratio means better modal distribution and ultimately better sound!

I have done some further calculations and readjusted the plan to work with this suggestion. The new inner leaf dimensions are:
Length - 4210mm
Width - 3209mm
Height - 2360mm

Volume - 31.88m2

All the mass will be inside-out as suggested (except that one cursed beam)!

I started with one of Loudens ratios, then proceeded to fudge it using prime numbers to maximise the space available and balance modal distribution as much as possible. It works well with Bonellos' thirds rule I think (1,1,1,3,5,7,15,26,51) and sits within the Bolt-Area.
It looks like 80ish Hz, 98ish Hz, and 134ish Hz could be problematic...

Given these new inner leaf dimensions, the side and front walls will have an air gap of 100mm, and back wall 400mm (I have off-centred the inner leaf so there is a bigger gap between the back wall and outer leaf to put in a sound-lock double door).

HVAC is typically the most confusing and difficult part of designing a studio. You mentioned a heater. What about air conditioning for warmer seasons or when you have gear running in there heating things up?

You got that right! My initial thoughts were a ducted system with an inline fan (the likes of which you find at those hydroponic grow shops), which could work as both a fresh air intake and cooling? Or would the fan not provide sufficient cooling? I do like the idea of a suspended ceiling heat pump such as this:

https://www.mitsubishi-electric.co.nz/h ... heat-pump

This particular example seems to have an air intake as well which could tick all the boxes! The range seems to be weighted more towards larger rooms however, so I wonder if it might be overkill...


Further Questions

- As the internal leaf is refined, I have found myself looking more and more at acoustic treatment options. Should my bass traps frames for example, be built into the inner leaf structure, or standalone in front?

- From what i've read, dimension calculations and whatnot can get you close, but will never be truly accurate in terms of modal distribution etc. Given this, how much acoustic treatment should be pre-planned vs. reactive after measuring room response? I imagine a degree of both?

Once again, thank you! This has invaluable information!

[Gregwor]

My father had an idea for the roof to use cellulose insulation between the corrugate and drywall (/plywood/whatever is decided to use) to mitigate any air gap between the corrugates ridges and added mass, thoughts?

Cellulose has very little mass. You need to use material that has a lot of mass and also suitable for location.

for electrical is to run lighting and misc outlets seperate from audio outlets - and to have all power come from the front wall to mitigate ground looping.

Research isolated grounds. That's the best way to have a worry free electrical system.

I suppose the if I put the patch bay at the front wall and had the cabling run alongside the misc outlets cabling for that side wall before going into the adjacent room, there would be no problem?

With balanced cables, I personally wouldn't worry about that aspect much.

- As the internal leaf is refined, I have found myself looking more and more at acoustic treatment options. Should my bass traps frames for example, be built into the inner leaf structure, or standalone in front?

That is the cool thing about inside out construction -- it really opens up possibilities for acoustic treatment. You can totally build it into the exposed frame work and then finish the walls/ceiling with fabric where there isn't any protruding treatment. It also allows you to have nice recessed looking light switches and outlets.

- From what i've read, dimension calculations and whatnot can get you close, but will never be truly accurate in terms of modal distribution etc. Given this, how much acoustic treatment should be pre-planned vs. reactive after measuring room response? I imagine a degree of both?

A degree of both for sure. The cool thing about having a nice rectangular room is that using modal estimations, we know roughly what to expect and what frequencies are going to be a problem. However, in these sort of builds, we can still simply follow basic rules for treatment.

Greg