It seems that we are all obsessed with the inner leafs and sealing them properly, yet I see maybe 10% of design threads even mention sealing the outer leaf properly!
BOTH leaves must be sealed very well. This is a basic requirement for good isolation. I try to emphasize that as much as possible. Even a tiny crack or gap can have drastic consequences. The basic rule: if air can get through, then so can sound.
but I can't imagine everyone already had a nice sealed up outer leaf.
Sealing up the outer-leaf is critical. I push that concept on every thread where isolation is an issue. Sometimes I get tired of typing the same thing over and over....
I then sealed the crap out of every possible gap.
Now, I'm even thinking about adding a layer of drywall to the side of the I-joust tomorrow because that will now be my weakest link in the outerleaf because there is barely any mass compared to the rest of the concrete outer leaf!
That would be good, yes, but instead of guessing how much mass you need on that part of the wall, you should do the math to make sure. As you say, it's the weakest link, so that's where you need to concentrate your efforts the most. So it's worth spending the time to work through the math, and double.check that that the amount you are putting on there, combined with the depth of the air gap, and the insulation fill, will produce the MSM frequency and isolation characteristics that you are aiming for.
The wall towards the top will now be using John's inside out wall method which I'm assuming needs to be rigid OC703 like insulation instead of standard fluffy pink stuff to get the proper absorption.
Either type of insinuation will work, provided that it is the correct density for the task. OC703 is easier to work with, and performs very well, but it's also a bit more expensive.
I plan to use some black burlap over the insulation and hopefully some wood slats.
Why?
Not meant to be a trick question, but rather a question to get you thinking about WHY you might want slats on there. Not just because you saw it in a few other rooms that you liked, but because you NEED them there....
Did you check what acoustic conditions you will have on that wall, at that location, and figure out that the best way to deal with that was using slats? Is that going to be a tuned or un-tuned device? If tuned, what frequency range will you tune it to? If untuned what size slats will you use, and why? What size gaps will you leave between them, and why? With studio design, everything matters. Nothing can be done by guesswork, or just because "I saw that in Franks' thread, and thought it looked cool, so I'll do it too...."!
1. Should I design the wood slats over the inside out wall now or wait to do a REW analysis once the room is completed?
I'll repeat the same question as above: Why do you think you need slats on that wall anyway? If you can't answer that question honestly, with a valid acoustic reason for putting them there, then you need to do some more research.
I've seen number designs ranging from the 534 pattern, to using 468 slats with the same slot, to Rod's recommendation of using 1x6 with a 0.75" slot.
Once again, Why? Just because you saw it in a book, and Rod did it that way in some of his rooms? Or because you did the acoustic analysis of your room yourself, and it showed that you would need a binary array diffuser done with slats at that location?
I'm not trying to be denigrating here: just pointing out that rooms should be DESIGNED for their purpose, with the right treatment in the right location for the right reasons. The reason "I saw it in a book", is not valid, unless your room is identical to the one in the book, and is going to be used for the exact same purpose. If Rod was using that devices in a control room or vocal booth, and you have a drum room, then likely it is the wrong treatment. Even if Rod's room was also a drum room, it it still possibly the wrong treatment, unless your room is the same shape and size as his.
2. I've researched multiple designs, but still haven't gotten a solid answer on the air lock. I've been getting feedback from a few venues outside of this forum and no one seems to have agreement on the airlock and if it will be a triple or quad leaf affect when there is a 46" gap between leafs.
If nobody has given you a straight answer then nobody has done the math!
It's that simple. There are equations for figuring this out. All you have to do is to plug in the numbers, do the math, and see what comes out.
But my question would be even more basic: Why are you wasting space with a sound-lock, when you don't need one! ?
Who told you that you need a "sound lock" like that on a home studio?
In reality, you do NOT need a sound lock: A simple pair of doors, back to back, with one door in the onner leaf and one door in the outer leaf, is all that you need. Anything beyond that is wasted, or at best, over-kill.
In an earlier post, you said "I didn't really see a point because i'm not doing back to back doors.", and my answer to that would be, once again, "Why?" Why are you not doing back-to-back doors? How do you plan to get high isolation if you don't terminate the leaves correctly?
I also have to add: I don't even see where the door into your "Drum Room" is! I see doors into the hallway outside, and into the bathroom, and into the bedroom, but none into the drum room.... Is your access into the room through the double windows on the left? Are those actually sliding glass doors? IF that is the access path into your drum room, then why do you have a sound-lock on the bathroom and bedroom?
I guess I'm just not understanding what you are trying to achieve here... I don't see the reason for the sound lock to start with, and I don't understand the implementation either: it is not going to work with the way you are showing it so far.
There are three options really:
But you only show two of them, neither of which is correct!
c. Add a double wall around EVERY wall because this system will react as one system so using a quad leaf will ensure better isolation even though it's not the ideal 2 leaf system
That would be a mistake too.
If you really do have your heart set on a sound lock (even though you do not need it), then the correct way to implement it is the same as any other pat of a studio: two-leaf walls on all sides, with back-to-back doors in each leaf. So you would need at least six doors there....
I also forgot to mention that i'm officially going with mini splits now in each room.
It is usually cheaper to go with a single ducted AHU that can handle both rooms. You can do individual units in each room if you want, but they are not 100% silent. That might or might not be a problem.
I'll be adding a SHR150 HRV for fresh air for each room as well
My favorite question again: Why? For what purpose do you need TWO HRV's when you already have two mini-split systems? And why did you choose HRV's, instead of ERV's? Did you do the math, and prove that you will get the savings you expect, to offset the investment? Over how many years?
Also, where will your fresh air intake be for each room? And where will your stale air exhaust go? And what portion of make-up air will you be adding to the flow? How will you vary that for different room occupancy loads?
Just pointing out things that you might have missed.
Silencer boxes have not changed and will remain one on the intake and one on the outtake ducts for the HRV.
Well, that's not going to accomplish much, is it?
For a studio, you need one silencer box on EACH leaf penetration for EACH duct. So for one room, you need four silencer boxes. For two rooms it would be eight silencer boxes, although you could bring that down to six if you design carefully.
Did you do the math to determine how big the silencer boxes must be? What flow rate are you considering for each room? And what flow velocity? Did you calculate the static pressure of the system for each room, and is your HRV able to handle that static pressure by itself, or will it need booster fans? What is the latent heat load and sensible heat load that each mini-split must deal with, for both maximum and minimum occupancy, and on climate extreme days (hottest day in summer with full occupancy / coldest day in winter with minimum occupancy)?
There's a LOT of math that goes into designing an HVAC system. When I'm designing a full studio, I usually spend about as much time just on the HVAC system as I do on all of the rest of the studio put together, including structure, isolation, layout, geometry, acoustics, etc. It's a huge subject and often overlooked by first time studio builders. Which is why I'm drawing your attention to it.
- Stuart -
