John Sayers' Recording Studio Design Forum

Well that would be exciting! So aside from the beauty if you're doing inside-out construction, and the 15% savings in cost, I guess lumber has no advantages over steel for studio construction. Then there's also the fact that lumber "settles" as it ages and dries, which I hear can lead to problems down the road...

Anyway, happy I'm going with Steel.

Thanks guys!

R.

Meanwhile, I think I understand your suggestion of the "faux float" floor decoupling idea, Stuart. I've found some similar designs elsewhere. If this is correct:

4" 703 directly on concrete floor
3/4" plywood, grain width-wise
Green Glue
3/4" plywood, grain length-wise.

My real question is: does anyone have a number for the TL of this floor construction? I want to make sure it can keep up with my wall and ceiling design.

Thanks everyone!

R.

Yup! That's about it.

Well, it decouples more than isolates. It is more intended for impact noise, rather than as a true isolation floor. That said, it will isolate to a certain extent, but not easy to predict how much, since the "spring" here is partly air and partly 703. I don't have any resilience figures for 703 used as a spring. But at a very rough "guesstimate", I would suspect that the combination of a 4" concrete slab plus the above would give you a TL of maybe 50-something. That assumes that the deck is carefully sealed all around the edges, of course, so that it is airtight underneath. In other words, leave a small gap all around the edges and fill it with very flexible expansion compound, or backer rod and caulk, or something that will keep a good seal even with movement of the deck.

- Stuart -

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

Hi all,

Work continues on the design. I am still wrestling with what to do about the neighbor's duct chase in the middle of the outer shell's ceiling, and the great amount of height that rises on either side of it. Duck it like in this architectural drawing? Or simply make a flat ceiling to the lower height that the duct chase defines? And if so, what do I do within that huge airgap? -- I wonder what thoughts people have.

Below is an architectural rendition of the Control Room elevation from the east (side view), as the design stands.

I am striving for a 1 : 1.3 : 1.9 room dimension ratio (one of the ratios recommended by F. Alton Everest). The width of the Control Room's inner dimension is 148.5" maximum. That would make an inner shell length of 216", and an inner shell height of 114". The actual height of the bottom of the duct's outer shell is 119.5". The full height of the outer-shell space to either side of the duct chase is 147" -- a difference of 27.5"!!!

If I simply design to the ratio's limit of 114", what do I do with all that extra space above the ceiling? My current plan leaves a great deal of empty space between the inner shell of the ceiling and the inside of the outer shell, for the rest of the room NOT underneath the duct chase. I have planned to just fill that interstitial space with standard R13 fiberglass batting.

Is there a more efficient use of that space? Would a hanger system ABOVE the inner shell work, or does that only work if it's INSIDE the inner shell (behind a false ceiling)? I consulted with Rod Gervais about his hidden bass trapping design, ambitiously creating an OC 703/R13 bass trap above the space, but of course that too needs to be within the proper limits of the inner shell (http://recording.org/studio-construction-and-acoustics-forum/53153-question-rod-about-hidden-bass-traps.html). OR: Should I just raise the inner ceiling, even though it takes us out of spec with my chosen ratio, in order to take best advantage of the space we have?

P.S.: Due to New York City's building codes, we cannot make a two-leaf system by stripping the inner layer of drywall on the ceiling and still maintain the required tenant fire separation. So after some consultations off-line with members, I've been advised to go with a three-leaf system and add 3 layers of ⅝" Type X drywall to the existing outer shell as a super-massy middle leaf.

Thought anyone?

Thanks as always —

Reed

Wow, things are suddenly moving along at a rapid pace, so let me ask another question that's come up.

My architect would like to put a slanted glass window in the south part (rear-ish) of the west wall of my inner shell to show off the brickwork on the outer shell, which would then be lit. I'll angle it backwards and add an equal and opposite slanted member on the east wall. Fine. But can I simply make a rectangular tunnel of 703 from the outside of the glass window to the inner edge of the brick wall, cover it in black felt, and expect the same degree of isolation as if it were the equivelant mass of drywall? Or do I need to somehow make that cavity airtight???

I am trying to understand the principles behind studio glazing to figure this out. Specifically, how does laminated glass differ from its equivalent mass of drywall? My reference for proper double-glazing construction is Rod Gervais' phenomenal book, "Home Recording Studio".

When we build studio windows, we are creating a two-leaf mass-spring-mass system. This I understand. 

But why does the glass have to be decoupled from the frame and drywall using neoprene setting blocks? How does it differ from any other part of the wall, which is of course mechanically connected to the rest of the wall structure?

Furthermore, when we line the gap/tunnel between the two window frames with 703 (then cover with black felt to make it purty ), doesn't that allow the air to pass into the rest of the interstitial cavity, thereby reducing it's "stiffness?" Is that not a liability?

Inquiring minds want to know

-Reed

Not sure I understand the plan completely: Maybe you could do a diagram of what you have in mind?

But anyway, in the specific questions:

Glass is about 3 to 4 times as dense as drywall, depending on the type of drywall and type of glass. "Three" is a good rule of thumb. The idea is to keep the surface density uniform. so if you have (for example) two layers of 5/8 drywall, that makes about 1-1/4" inches thickness. One third of that would be roughly 3/8", so you'd need 3/8" glass or thicker to maintain the same surface density.

It doesn't! The neoprene and etc. is for sealing and protection, not decoupling. If you just put the glass up against the wood, with nothing in between, you aren't supporting the edge of the glass very well, and you have no seal. Good seals are critical to isolation.

If I understand you right, you are talking about putting 703 in the cavity between the two leaves of the wall, as normal, but obviously where the glass is you cannot have any 703 there, since you do want to see through to the other side. So you leave a hole there, through the 703, and cover the exposed edges of 703 with cloth for aesthetics? Is that it? If so, then I'm not sure I understand what you are concerned about: the air in the cavity is just air in the cavity. It is your "spring" in the Mass-Spring-Mass system. The difference where the glass is, is that you don't have any DAMPING in that area (the 703 is damping, not spring). So in that area you have decreased isolation due to the lack of damping, yes. Which is why it pays to have slightly more mass in the glass, and/or slightly bigger air gap in the cavity in that area, to compensate for the lack of damping.

Not sure if I answered your question, though!


- Stuart -

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

Hi Stuart -- thanks for trying! I'm afraid I did not explain it well enough.

Here is a screenshot of the idea that may "frame" the question better (sorry--I couldn't resist!). Is this more clear? The window idea would be an aesthetic addition, which would be a variation on the theme of two-leaf studio glass where the outside leaf of glass is replaced by the wall behind it -- so the glass is not there to facilitate communication between rooms, but rather to be an aesthetic addition.

And yes, I now see that the 703 is damping for the chamber as much as it is a "structural element" to keep all the pink fluff beyond its boundaries from falling in.



Sorry for being difficult to understand!!! I did not make it easy. But you answered the most important part of my question--the interstitial space between two windows does NOT need to be sealed from the space surrounding it LATERALLY -- that was my misunderstanding of the principle. The air between the two windows, as I now understand it, is mechanically connected (through the 703 and felt) with the rest of the air gap between the inner and outer leaves. Stiffness is achieved in the air simply by making sure all construction is sealed -- both at the window-framing junctions, and at every other element of the two leaves -- it's all one (or two). Boy, now I think I'm really confusing everyone...

And finally, thanks--that is immensely helpful to know that the glass does not have to be isolated from the window frame, but simply sealed to air-tightness. Got it!!! I thought that we wanted the glass to be free-floating so that it would resonate well at its critical frequency which we would then damp in order to... oh, nevermind! Dumb ideas come in much more variety than smart ones.

Thank you Stuart! Your student is learning... slowly...

Reed

Great! That's kind of what I imagined. Makes more sense in your detailed model. Nice SketchUp work, by the way! The glass issue is a lot more "clear" like that... (hey, two can play at the corny pun game! )

But I'm just curious about the angle to the glass: Why do you need to angle it? Is that for aesthetics, or light glare? Not needed for isolation. In fact, angling the glass is detrimental to isolation.


- Stuart -

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

Hi Stuart, thanks!!! Glad this will work -- I think it'll be really cool.

The reason for angling the glass is to prevent flutter echo with the opposing wall -- since I can't add treatment over the glass. Think that makes sense? I lose 5 inches of airgap at the closest end, but that leaves a full 10.5" of airgap, so I'm hoping it still leaves me in pretty good shape.

Thanks Stuart!

Reed

So: As I mentionned earlier, I posted over on the amazing studio construction forum at Recording.org that Rod Gervais moderates (http://recording.org/studio-construction-and-acoustics-forum/53153-question-rod-about-hidden-bass-traps.html). I asked Rod about the same issue I brought up above: What are the possibilities for any sort of bass trapping BETWEEN the inner & outer shell, e.g. Above the hard ceiling boundary. His answer was very interesting to me, and I thought I'd quote it for everyone here:



What I found most interesting (aside from how I learned I should stick with fluff) was the side-point that the more impedance you present to sound as "sound-isolation" will elevate the relative level within the room.

Obvious once you hear Rod say it.

Reed

Build is imminent. One last question.

Is it possible/necessary/possible to put fire blocking in the interstitial cavity between the outside of the inner stud frame and the outer shell???

One last major "Thing to make you Hmmm..."

Thanks! Next time, I'll see you over in the construction forum!

Reed

If I'm understanding this right, you would not want any hollow cavities, and some fiberglass batt would be in order.

_________________
Ted

Soundproofing Company

Yes, fill the interstitial cavity between the inner wall and the outer-shells with pink fluffy fiberglass--but no additional hard fireblocking to prevent a fire from fully engulfing all sides and ceiling of inner shell?

What does your local building code say about that? Follow the building code, and if necessary try to adapt your design to fit both the code and also your acoustic requirements.


- Stuart -

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