Garden Mix Room and Vocal Booth, Design and Construction

[swfeathers]

Hello all,

I've perused these forums for years learning all sorts about studio design, construction and treatment for various places I've worked. I'm excited now to be in a position where I would like to build my own mix room and vocal booth from the ground up in my garden in South London. I'm here to get some thoughts and advice from the community and am keen to get someone on board professionally to help with the design and eventually the construction.

So having read the forum rules, here goes!

I am a music producer and mix engineer and plan to use the room for writing music and mixing music, but would like the flexibility to record solo vocals and solo instruments when needed.

I have just moved to a mid-terraced house in South London. The garden is rectangular and approximately 5.89m wide x 19.19m long. My current experiments in Sketchup have me building a studio with a footprint of 4.04m x 7.12m in the bottom corner of the garden.

I would like to try to keep within permitted development limits, which would restrict the height of the building to 2.5m. However, I am also keen to maximise internal height and am therefore interested in exploring the possibilities of digging down a bit and having the floor of the studio below ground level. An internal height around 2.55m is what I think I'm aiming for.

Keeping external noise out and my noise in is obviously very important. The neighbours already have a garden office that I don't want to disturb. There is the occasional plane overhead, the occasional bit of noise from a nearby industrial estate and the tube runs underground not too far away. The tube sometimes causes a soft rumble in the house, but isn't noticeable in the garden. I imagine this is somehow connected to the house's foundations and the noise travelling along the terrace of houses. I plan to do some proper noise measurements in the coming days.

I've been looking at the external walls being constructed in dense blockwork, then leaving a 100mm air gap before building the internal studwork walls filled with Rockwool and plasterboarded. I'd also be interested in the possibility of building a concrete roof, both for sound isolation reasons, but also as the base for a "green roof".

Because of potential ground-born noise from the tube, I've explored some floating floor options. I've seen that there are mixed views on the subject around the forum though. I thought this system by Farrat looked interesting. This is potentially the biggest variable in the project as it affects the height of the building and therefore the groundworks required if digging down.

The position of the main RCD in the house means that getting power out to the garden shouldn't be too hard. HVAC is something I know nothing about, so need to do some more research on the options.

Please find attached a basic SketchUp model showing the footprint of the studio in the garden. The large area of land to the rear of the proposed studio is currently an allotment owned by my neighbour. It is overgrown with brambles and is not in use. I'm hoping I might be able to buy it, however I could not construct anything on it due to a covenant in the deeds. It would therefore remain as garden / allotment / shed / greenhouse area! The only consideration for the studio construction is leaving access to this bit of land down the side of it.

At the risk of embarrassing myself, I've also attached a model of a cross section of the studio. I was using this to try to calculate how much groundworks might be required and how the height would be affected by a floating floor and green roof. I might be way off though!

I have currently budgeted around £25,000 for the design and construction. I understand however that there are still some big variables involved.

Any thoughts from the community would be much appreciated. Similarly, if anyone would like to recommend designers and trusted studio builders near-ish South West London then that would be very helpful.

Thank you for you time.

Sam

Link to download SketchUp models

[Gregwor]

Glad to have you! It seems like you've done a lot of research and I'm very impressed with your first post on the forum!

Everything you've written seems great. Looking at your SketchUp drawings, I would suggest having your booth in front of your mixing position so that you can communicate through a window. The window could just be a door which would allow you to still soffit mount your speakers if desired. Also, this would get your door out of the corner which is the worst place for a door.

If you insist on having your booth behind your rear wall like your drawing, I highly suggest moving that door to the middle of the room which would allow you to have nice big important bass traps in the corners. You could still have seating back there but instead of a love seat, you would have to have two single person chairs.

Lastly, you have your speakers sitting on top of a desk. Ditch that big desk for something small and either soffit mount your speakers or put them on heavy stands right against the front wall (with a 100mm slab of insulation between the back of the speaker and the wall).

Keep us posted. This looks like it's going to be an interesting one!

Greg

[swfeathers]

Hi Greg, thanks for your thoughts and sorry for my slow reply.

I'd love to pick you brain further if possible?

I would suggest having your booth in front of your mixing position

I'm certainly not against this, but I don't see how I could make it work with the footprint of the building? If the booth is in front of the desk, wouldn't it be awkward getting round the desk and past speaker stands to get into the booth or am I missing something?

this would get your door out of the corner which is the worst place for a door

Not something I'd thought about, but I can understand how that would be bad for bass-trapping and treatment in general.

either soffit mount your speakers or put them on heavy stands

Don't worry, the drawing of the desk is not what I had planned, just something I dropped in to quickly show orientation of the room. I've never really considered soffit mounting an option though, I think I like the flexibility of heavy duty stands.

That rough Sketchup of mine shows roughly how I'd envisioned the walls constructed: a leaf of dense concrete block-work, an air gap and then stud-work filled with rockwool and plasterboarded. What's the process after that for calculating a good amount of treatment in the room? Front wall, rear wall and 1st reflection areas being most important, right?

Thanks again for your time.

[Gregwor]

I'm certainly not against this, but I don't see how I could make it work with the footprint of the building?

Since you're going to be building from scratch, you can place your door wherever it needs to be to make it work. The location of the door right now is not too far off of where it would need to be. I'd recommend putting it almost in the middle of the control room -- slightly towards the back of the room so that is isn't in the way of your first reflection points or bass trapping.

If the booth is in front of the desk, wouldn't it be awkward getting round the desk and past speaker stands to get into the booth or am I missing something?

The speakers would not be in the way because they will be right up against the wall, or soffit mounted. Since you're building from scratch, I'd recommend running conduit through your slab to the speaker locations (from your desk location of course) and into your booth. This will eliminate any cables being run across the floor and ultimately prevent any chance of people tripping over cables.

Don't worry, the drawing of the desk is not what I had planned, just something I dropped in to quickly show orientation of the room. I've never really considered soffit mounting an option though, I think I like the flexibility of heavy duty stands.

The ease of stands is tempting for sure. Designing and building soffits is tough. But acoustic benefits of soffit mounting is enough for me to recommend it though. What I would suggest is drawing up your room with and without soffit mounted speakers. That way you can easily add them later on if you want. I don't think you need to fully design the soffits in your drawing, but make sure you get the angles and depth (to accommodate a speaker module in the soffit) sorted out. Getting your cloud designed to work with both speaker layouts will be critical as well.

What's the process after that for calculating a good amount of treatment in the room? Front wall, rear wall and 1st reflection areas being most important, right?

There are different approaches to this for sure. You need to decide the style of your control room. The most common design these days is RFZ, but with that comes soffit mounting. If you just want your speakers on stands, then yes, getting your 1st reflection points, bass traps, and your rear wall under control. Once you get your room built and empty, take acoustic measurements and then go from there. For your booth, John Sayers has a calculator on his website to help you figure out what material to put in the room to achieve your desired RT60. But since the booth won't be massive, you're going to have to do your best to put as much bass trapping in there as possible.

Greg

[swfeathers]

Thanks again Greg for taking the time to reply. Your thoughts on soffit mounting, doors and treatment have all been noted.

I finally had some time to take some SPL readings out in my garden to get a better idea of the ambient noise I might be dealing with. The average SPL across 10 mins on two separate days was roughly 61dbC with peaks up to 73 dbC.

Pair this with the knowledge that loudest thing I might be looking to record is a big, belty vocalist or a fairly cranked guitar amp and hopefully that will give you a better idea of the isolation that I require. I should also point out that I would like to be able to record voiceovers too, which often require a pretty quiet room so as to keep a sensible noise floor.

My initial thinking was | 100mm Dense Concrete Blockwork | ~100mm Airgap | 75mm Insulated Studwork | 15mm Plasterboard. Or reverse those last two for the inside-out wall approach.

Is that close to achieving the TL I need? Is it overkill, should I be thinking about two leafs of timber studwork instead of the concrete blockwork?

Once again, thank you for your input.

Sam

[Gregwor]

I should also point out that I would like to be able to record voiceovers too, which often require a pretty quiet room so as to keep a sensible noise floor.

The amount of isolation you need for this is going to be up to you. You could aim for 60dB of isolation. Much more than that is going to go into a different realm of build and money though.

| 100mm Dense Concrete Blockwork | ~100mm Airgap | 75mm Insulated Studwork | 15mm Plasterboard.

The way the MSM design works is to have a similar surface density on both leaves. Right now, your inner leaf is very light and thin in comparison to the concrete. Imagine this extreme example: An outer leaf made out of lead. An inner leaf made out of a thin piece of paper. Would the paper even help? Probably not. Now, imagine both leaves made out of lead. That would be awesome. If you're using concrete as your outer leaf, I would suggest using at least 2 layers of 15mm plasterboard. Maybe even a layer of 3/4" OSB as well.

Is that close to achieving the TL I need? Is it overkill, should I be thinking about two leafs of timber studwork instead of the concrete blockwork?

Use this calculator to determine the estimated amount of isolation you will achieve with different building materials and distance between them.
Gregwor & audiomutt’s MSM Transmission Loss Calculator Version 2.03

As a side note, remember that as you raise up your isolation level, you will also need your insertion loss to match that. This means large silencer boxes that have several baffles. These will have to be made out of materials matching the surface density of your inner leaf sheathing.

Greg