John Sayers' Recording Studio Design Forum

Great, Thanks Stuart!
Fair question
The front soffit, the slot resonator on the right and the rear bass traps are all closed at the top with two layers of 15mm plasterboard (given the small void between outer and inner ceilings, it was much easier to build the frame that way).
On my previous post I exported the 2D graphic from SketchUp with their level hidden, just to be able to show better the fresh air plan

ciao
Simo

OK, that makes sense. Smart idea!

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Right..bad news…the budget is drained !
As it stands now I won't be able to do the air con at this moment . If i did, I'd be left with just stud walls and a beautiful HVAC system BUT nothing else

… so now the plan is:

I AM going to do the fresh/stale air in/out system as I understand that step can't be skipped !

Then, after the studio is finished and hopefully bringing some money in, install the two mini-split systems at a later stage.
Also, as the fresh air system is the only part of the HVAC that needs to be in the void between the two ceilings (as the two mini-splits will be mounted on the walls), I will finally be able to close the ceiling frame with the plasterboard layers and crack on with the rest of the build !

When the time comes (I hope very soon), I will position the wall-mounted part of one system on the back of the control room.
Then another one will be mounted on the live room (on the wall opposite side of the window).
Luckily both these walls are built inside out (i.e. two plasterboard layers attached to the stud frame, insulation between studs and a cloth stretched over it)…. so it should be fairly easy to remove the cloth and insulation, and drill the holes to pass through the piping from the inside unit to the condenser outside.
I will make those parts easy to remove with a drill driver, to make this step as painless as possible.

So the fresh air WILL BE there, and the conditioning will be temporarily provided by a portable electrical heater (if cold) and by opening the door from time to time (if warm).

I know that it's by no means ideal (and I'm indeed disappointed ) BUT there's nothing else I can do as the money is simply not there at the moment and I have to think of alternatives to get me going and make all this effort worthwhile!

I read many times the HVAC chapter of Rod's book, and I'm particularly aware of his introduction "Re-work is always a lot more expensive than doing it right the first time. So save your money, keep your sanity, and plan for this now". But by doing it this way, I hope that I'm minimizing any rework in planning for the air con to eventually be placed.

… but what are your thoughts? Would that work? Any thoughts much appreciated as usual !

Simo

Bummer!

Yup! People have this silly habit: we like to breathe... If we could get over that, then we wouldn't need to ventilate our studios!

As you say, it's not ideal, but if that's the only option you have, then that's what you'll have to do. It will work, but bare in mind that without A/C you won't have any de-humidification going on, so there's the associated risk of problems related to high humidity in your room. Especially considering where you live: London isn't exactly known for its extreme dry weather, and desert-like climate! So maybe consider putting a portable dehumidifier in there, if you notice humidity issues.

Also bare in mind that when you do put the mini-splits in eventually, that will necessarily involve some destruction of your isolation walls: The installers will have to cut holes in them to pass the pipes through (normally two copper pipes for the coolant, plus a condensate drain pipe, plus an electrical cable), all grouped together. That's going to need a lot of attention when they do that, since that bunch of lines is a potential flanking path, and the holes are potential major weak points. So that part will need to be done with care, in order to get you back to the same level of isolation.

You cannot just do what the HVAC installers will want to do, and are used to doing: Cut two holes through the two leaves directly opposite each other, and run the group of pies straight through! Bad idea, on all counts. The holes cannot be opposite each other: the must be separated by as large a distance as you can figure out.

Since your walls are going to be inside-out, that presents a problem as to how you are going to isolate and decouple all of that! The electrical cable and condensate line are not too much of an issue for flanking, since they are usually light and flexible: you can loop the cable inside the wall and hang it from above, and you can route the condensate line carefully (making sure to keep it always sloping down, never up), but the coolant lines are a problem. They are probably copper, and usually at least the return line is wrapped in a thick thermal insulation cover. There needs to be enough space inside your wall to deal with all that, and stop them from creating a major flanking path between the two leaves.

One way of dealing with that is to curve the pipes as soon as they get through the inner leaf, then route them over a long distance (up, down, sideways, maybe even in a loop or spiral), before curving them again to go through the outer leaf. And of course, do not let the copper contact the drywall directly: seal the holes really well with acoustic caulk. etc.

It's much easier to do all that with the walls open, before you put the drywall on: doing it afterwards is a pain. Like Rod said: it's a pain to retro-fit!

So all of that is going to need some careful planning in advance: How are you going to replace that section of drywall that you need to remove in order to do all of the above? That should be considered now, in advance, before you even start building the wall. It will be too late to do that once the wall is built. (Or rather, it can still be done, but there will be compromises, and it won't be easy, or cheap.)


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Thanks for your input Stuart, all good points as usual !

I had a sort of idea of how to minimize the destruction and replacement of my isolation walls, but that actually involved cutting a hole through the two leaves directly opposite each other.
…what you say (curving the pipes as soon as they pass through a leaf in order to have the two penetrations as far away as possible) makes a lot of sense, and I now understand why it is not a good idea doing it the way I was planning.
Thanks for pointing that out !

I guess my only option now is to see if I can securely plan it taking that into consideration, or otherwise wait and stop the build for some funds to do the installation before the access to the gap between the leaves is totally obstructed.

ciao
Simo

One option that comes to mind, is to do one single stud bay "conventionally" instead of "inside-out". In other words, the two studs right next to where the A/C unit will go could have their drywall on the room side, instead of the cavity side. You could then use that location to do all the "pipe mangling", have good access for sealing everything carefully and making sure it doesn't touch structures, plus you'll have an extra 3-1/2" of depth to work with, and the final drywall can be attached easily from inside the room. If you run your pipes almost vertically in the wall, that should give you plenty of room to keep the inner-leaf and outer-leaf penetrations far apart. The only drawback is how you fit that single "conventional" stud bay into the overall acoustic plan for the rest of the "inside-out" wall. But I reckon that should be easier than the alternative! If you plan things carefully, there should be no acoustic problems from having just that one small section of wall the "other" way around.

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Great idea Stuart !!

and fitting that "conventional" section into the rest of the build shouldn't be too difficult… I think it's just a matter of having one additional stud on the left and one on the right (screwed and caulked to the ones already there) (pic 2) and then attach the drywall to those from the inside of the room (pic 3)


Simo

That's what you're paying me so much for!

You could do that, but you don't really need to, unless you were planning on more than two layers of drywall for your room. The goal is to retain the same surface density throughout the wall: Drywall and wood are roughly the same density (around 700 kg/m3), so as long as you have the same thickness all the way around, you are fine. Two layers of drywall (32mm) is actually thinner than one stud (38mm), so you are fine with just one stud. Of course, adding the extra one certainly won't do any harm! It's always nice to have a safety factor in there, and ensure a better seal too. But in theory you could get away with just the single stud that's already there.

Your diagram looks exactly like what I had in mind!

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Thanks a lot for your steady assistance - much appreciated - really!!

I'll be the first buyer of your book though

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Hi

While planning a strategy for my HVAC, I'm trying to get on with other things (no time to loose!), so now I'm about to start building the speaker boxes.

Here is a sketch of my plan:

- frame with a 18mm OSB plate attached to the back of the front studs

- 18mm plywood plane (with vent)

- speaker box (lined with a 5mm sorbothane sheet)

- vents on the speaker box at the top and the bottom

- opening for the cables (on the back of the speaker box)

- 18mm baffle plate (plywood or OSB), levelled with the speaker box.

The speaker is 12mm out in order to be levelled with (BUT not touching) the next "finishing:" layer, which is a 12mm timber plate (see next pics)

- 12mm timber finish


- 2mm gap between the speaker and the timber finish plate (filled with acoustic caulk or soft rubber), in order to decouple them

Is this ok? or there's something I'm missing or that could be improved / changed?

Also (I know I already asked this , but …), I'd like to have a packing strap or heavy string around the speakers (in order to be able to pull them out if needed), but how would you hide their ends for a neat finish (so they don't hang out from the 2 mm gap between the speakers and the timber finish) ?

Thanks!

ciao
Simo

…or another option would be:

- the speaker front is flush with the case

- which is 12mm out from the baffle plate

- the 12mm timber finish will end against the speaker box edges

- a 2mm wood trim will cover the remaining visible part of the speaker box

It's a slight variation from my previous sketch (everything else remains as posted on the post above).

This one seems to hold the speaker more securely (and perhaps it'd be easier to build too with less margin of error).
Don't know whether the 2mm wood trims would compromise the soffit effectiveness, even being just 2mm thick?
Which one would you recommend?

Thanks !

ciao
Simo

the 2mm trim should not be an issue and you can tuck the packing strap ends under it to hide them. you might increase the depth of the padding around the speaker to at least 12mm.

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Glenn

Here's an off-the-wall idea: Maybe attach the trim with Velcro strips behind it, so you can get take it off easily to get access to the packing straps?

Not sure if that would work: It just came to mind when I saw Glenn's post.

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Thanks Glenn for your clarification and Thanks Stuart for the Velcro strips idea !
Much appreciated

ciao
Simo