1st Option.jpg
Soulshaker wrote:
Thank you so much Paul.
I understand what your saying. I did a good job on the whole addition (live room) of having everything correct but I really screwed up the transition. Anyway I'm willing to do either of the options you presented because its certainly is worth it. I included a pic of the layers with a tape measure on it. It looks like if I remove everything and did a true 2 leaf that my air gap would be 10 3/4". If I did the 2nd option of an inside out the air gap would be 2 1/8". Please let me know your thoughts, once again I'm very grateful for yours and others expertise,
-Jason-
Hi Jason,
Cool, so actually your air gap for the 2nd option would be
about 6.25" as you need to
include the depth of the 2x4 - remember you always measure the air gap panel to panel, not from the edge of the stud. That's actually fairly decent.
Using Greg's incredibly handy MSM TL Calculator (which he so generously provided for us all to use here, thanks Greg!) I've run the two simulations to give you an estimate of your potential transmission loss with each assembly. Keep in mind this is just an estimation and I haven't included the green glue in the data as there's no option to include it in the calculator and it's difficult to predict since it has a damping effect, but it just means your actual transmission loss should be even higher than predicted here:
Here's option 1:
1st Option.jpg
Here's option 2 (with the inside out wall):
2nd Option.jpg
The insulated cavity resonance is really important. Ideally you need it to be half of the lowest frequency of your monitors, so if your monitors go down to 40hz then the cavity resonance should be 20hz or more, this will ensure excellent isolation. That's one of the reasons why a larger cavity is much more effective than a smaller cavity. But nothing is ever normally ideal when building a studio, so you have to compromise.
So, obviously option 1 will provide the best isolation, but since this is a wall between live room and control room
the isolation doesn't actually need to be incredibly high due to the fact that you'll generally be monitoring what's coming out of the live room anyway.
If you went with option 1 you'd also have the tedious process of trying to neatly cut out the drywall AND the OSB and remove it, while trying not to damage it in order to reuse... that would be a bit of a nightmare.
If it were me I would just compromise and make that wall an inside out wall (option 2) - so you remove the most inner layer of drywall and then re-apply it between the studs, inside the stud bays, leaving the studs revealed.
You would do this by cutting the drywall to fit in the stud bays, then fasten it by using wooden cleats or battens around the perimeter pressed up against the drywall and fastening the timber cleats or battens through the sides into the studs. This is what people round here call "beef up". Once you have it fastened you can caulk around the perimeter to seal the edges to the studs so there are no air gaps. You want this beef up drywall layer to be pressed up tight against the existing drywall layer, you could use green glue here if you wish but not vital.
Where the inside out wall transitions into your non-inside out walls, you need to make sure that the studs are connected and that there are no gaps on the corners, obviously the drywall layers won't meet, but as long as the studs meet (put more studs there if you need to fill a gap) and it's all sealed completely air tight then you're good. All of your inner and outer shells need to be completely air tight, don't forget about the ceilings/roof.
Once you've done that you'll have a nice load of framing into which you can put your insulation as part of your acoustic treatment for your control room.
3 other points:
1. I noticed in your air gap between the two walls there is a literal air gap. The insulation you have in the framing is good, it's also the right type, but it should also fill the entire cavity. I'm not sure if you'll be able to put any more insulation in there the whole way across the wall now since you can't access it, but if you can find a way to do it such as push it in with a pole or something?! that would be good.
2. You mentioned that your live room walls are constructed like a proper double leaf assembly. Does the outer leaf of that assembly extend all the way round the perimeter of your control room/other areas as well? If so, does the wall that you're going to modify connect to that same wall in anyway? If it does, you need to break the connection. Hope that makes sense?
3. That wall that you're going to modify between the control room and live room - right now it extends the entire width of your space, if your control room is only going to be a portion of that width and you're going to have other rooms around the control room, then you need to break the wall so that there is separation between the control room and the other areas outside of the control room. Here's an example of what I mean:
Screenshot 2020-03-30 at 11.20.07.jpg
You see how there is a cavity all the way round and in between the rooms? There is no hard connection between any of the inner and outer walls of the actual studio. That is what you need through out your studio.
Hope this all helps,
Paul