New Room Advise

[Gregwor]

Do I really need backer rod in a gap that small and only 5/8 deep?

No, you don't. But it helps for larger gaps, so it always is nice to have some rolls of backer rod ready for when you need it!

Cleats? I don't understand, A quick google of drywall cleats didn't bring up much just drywall repair stuff

DSC03176.JPG

You can use any small scraps of wood you have. Basically just use them to hold the drywall up. You want your drywall firmly held up, but a sort of "floating" effect is what you want. You don't want it firmly anchored via screws.

Is there anything I need to do to the edges of the drywall pieces after I cut them to get the caulk to stick properly?

Once your gap is filled with coat #1, it will probably shrink some. Apply a second coat and be sure to apply it over top of the gap, having it stick to the outside material. Overdoing the caulking is probably a good idea.

Greg

[SunkenCity]

The picture you posted is with engineered I beams and it is a bit easier to do it the way you suggested but what about with standard joists. Seems like it would be a real pita screwing blocks in sideways into the joists all while holding the drywall up. the wood block would be screwed into the joist holding up the drywall but how do I seal the seems with the wood blocks in the way, just seal the edges of the block?

[Gregwor]

The picture you posted is with engineered I beams and it is a bit easier to do it the way you suggested but what about with standard joists. Seems like it would be a real pita screwing blocks in sideways into the joists all while holding the drywall up.

Here is a pic of my friends subfloor beef up that has regular dimensional type joists. I think he used 2x3 dimensional lumber cut into little rectangles for cleats. I personally put some up with him and it wasn't hard. Pre-screw into the cleats before you even take them up there! Of course, 2 people doing the job makes it easy.

Darren Subfloor Beef.jpeg

the wood block would be screwed into the joist holding up the drywall but how do I seal the seems with the wood blocks in the way, just seal the edges of the block?

Go to the edges of the cleats with sealant layer #1. Then, one at at time, move the cleats and apply a second layer of sealant

Greg

[SunkenCity]

Alright that makes sense. Bit more trouble with only 10" between the joists and alot deeper, my drill barely fits between the joists. Might have to screw the blocks in at an angle but if you're sure the benefits out weigh the trouble I'll do it.

So one of my walls is 3/8" drywall , what should I add between the studs to match the other leafs?

It also has more than a few punctures and I don't have access to the other side. Is there a good way to patch them? without making a mess on the other side.

What do you guys do about outlets that penetrate to the outside of the outer leaf?

Thanks

[Gregwor]

Alright that makes sense. Bit more trouble with only 10" between the joists and alot deeper, my drill barely fits between the joists. Might have to screw the blocks in at an angle but if you're sure the benefits out weigh the trouble I'll do it.

Screwing in at a 45 degree angle would be fine.

So one of my walls is 3/8" drywall , what should I add between the studs to match the other leafs?

Did you try my calculator? It's very easy to check what you'd need to add to achieve the same transmission loss as your other walls

It also has more than a few punctures and I don't have access to the other side. Is there a good way to patch them? without making a mess on the other side.

What is on the other side? If it's not another commercial space, you could use the standard drywall repair technique of cutting a square or rectangular hole where the puncture is, take something like a strip of plywood or dimensional lumber and place it across the backside of the hole. Screw through your drywall to hold this reinforcing piece in place. Now, you'll have a solid backing to screw your square or rectangular filler piece of drywall too.

What do you guys do about outlets that penetrate to the outside of the outer leaf?

Box them in with the material of the same surface density as your outer leaf. Seal the heck out of the wire penetration and stuff the box full of insulation around the electrical box.

Greg

[SunkenCity]

I pulled up your calculator on google sheets but wasn't sure how to add another layer to the sandwich.

I bought a table saw and have been ripping all the 5/8s drywall that I pulled off the walls into pieces that fit inbetween the ceiling joists. very dirty job, really have to motivate myself get it done. only 7 more sheets of leftovers to go.

Is this my lucky day? I found a 3' x 6' pane of 3/4" thick glass by the trash at a junk shop I go to. Will this be good for the thicker glass of my control room window? Had to drive it home with one of my car doors wide open so I hope it's just what I need

[Soundman2020]

I bought a table saw and have been ripping all the 5/8s drywall

You are ripping DRYWALL on a TABLE SAW???? WHY????

It is dead easy to cut drywall with a box cutter! Just score along a straight edge slightly into the surface, and snap along the score.... Very fast, very easy. not too messy....

Is this my lucky day? I found a 3' x 6' pane of 3/4" thick glass by the trash at a junk shop I go to

Wow! That's pretty cool! You sure are lucky. Do you know if it laminated glass? That thick, it might be, which would be great. But even if it isn't, that's still a nice chunk of glass. But do you need your window to be 3' x 6'? Is that the size you wanted? You can't cut laminated glass, so hopefully that is the size you need.

- Stuart -

[Gregwor]

I pulled up your calculator on google sheets but wasn't sure how to add another layer to the sandwich.

The "sandwich" as you call it is achieved by selecting something in the "MATERIAL 2" column. The calculator can accept up to 4 layers per leaf. Give that a shot and if you're still confused, I'll try to direct you using pictures or something.

Greg

[SunkenCity]

well I figured it would be the best way to get nice square cuts quickly especially having to make all the pieces for between the joists and studs and the table has measuring doohickeys already on it.

How do you tell if its laminated? I've been searching craigslist for control room windows for a while and was just gunna use what I could afford that was already framed but 3' x 6' is pretty much what I was hoping for. I read somewhere you don't wanna go over 3' tall and square is bad..

Would I use this on the control room side or the live room? I think John said you want the thicker side on the control room right?

How thick should the other piece be ( I guess that depends on the above question and the surface density of the 5/8" drywall x2 + 1/2" OSB leaves)

should it be the same dimensions or slightly smaller?

There's a small amount of damage on two of the corners, No cracks but scalloped surface chips. I figured I could fill it with epoxy to make a good surface for the seal and put the damage on the side not facing the live room

[Gregwor]

How do you tell if its laminated? I've been searching craigslist for control room windows for a while and was just gunna use what I could afford that was already framed but 3' x 6' is pretty much what I was hoping for.

You should be able to look at the edge and see the visible interlayer. If you can't, then chances are it's not laminated.

I read somewhere you don't wanna go over 3' tall and square is bad..

Where did you read this. Share a link if you can. I don't see why the size or shape would matter.

Would I use this on the control room side or the live room? I think John said you want the thicker side on the control room right?

It has been suggested by some people to use a thicker glass on the control room side. I've also read some books written by well respected cats that having your glass differ in thickness provides no real improvements. A Mass Spring Mass system works best when both masses are the same thickness. If the different thickness theory provided a major improvement, then why aren't we doing the same thing with our walls?

How thick should the other piece be ( I guess that depends on the above question and the surface density of the 5/8" drywall x2 + 1/2" OSB leaves)

For the third time, I will recommend that you use my MSM TL calculator as it will answer this question (it has glass as one of the leaf materials). Or do the math yourself if you find that route easier.

should it be the same dimensions or slightly smaller?

It depends on your room design. Personally, in my design, my control room window looks into my ISO room. The window in my ISO room is wider so that I can see more of that room from my mix position.

There's a small amount of damage on two of the corners, No cracks but scalloped surface chips. I figured I could fill it with epoxy to make a good surface for the seal and put the damage on the side not facing the live room

That should work fine. Just make sure it makes a good seal. And be careful while you're handling it!

Greg

[Gregwor]

I decided to use the calculator to figure out your glass thickness for you. I just typed in glass thickness (in mm) until it went just over the same TL as your wall leaf.

SunkenCity Glass Thickness.jpg

If you look at the "TL of Leaf 1" you'll see that your wall (with two layers of 5/8" drywall and 1 layer of OSB) will provide a TL of 34.21 dB.

With 12mm of laminated glass, that leaf will provide a TL of 34.44 dB. If the price jump isn't too big, it would be smart to go a size up from 12mm. You don't want your glass to be your weak link.

Greg

[SunkenCity]

The piece I found is 3/4"/ 19mm so thicker than the suggested of 16mm / 5/8".

Pretty sure it's not laminated I don't see layers

Should I try and find another piece just as thick? I was hoping I would only need a thinner/cheaper piece to complete the window.

This is where I read the thing about avoiding a square piece:
http://www.muzines.co.uk/articles/build ... indow/2884

John H. Brandt? mentions the the 3' tall thing here:
https://www.gearslutz.com/board/studio- ... ndows.html

I guess you updated the MSM tl cal, I just pulled up one I had downloaded a while back. I'll have to take another crack at it to figure out what to add to the wall with 3/8" drywall. Be nice to still have it only be two layers added to reduce the amount of GreenGlue needed

I've started sorting out the scraps of drywall I cut and dry fitting them.

IMG_0610.JPG

Also cut a bunch of triangle bits to hold the drywall up. How often should I space them to make sure the piece is getting the proper amount of compression for the GG but still "floating" ?

[Soundman2020]

This is where I read the thing about avoiding a square piece

I would not base my studio window design on ANYTHING said in that article! It is full of incorrect, misleading, and only half-true statements and claims.

For example, it tells you to angle your window glass, when in fact doing so DECREASES isolation, instead of increasing it. Here's why angling the glass is not necessary from the point of view of mic reflections (an often cited "reason" for angling it):

angled-windows-dont-work-mic.gif

And here's why it reduces isolation:

angled-windows-dont-work-isol.gif

That article also wants you to believe that a tripe-leaf window is better than a double leaf window (!!! )! Here's the REAL issue with double-pane and triple-pane glass:

This is the typical isolation you'd get from ordinary double-pane windows:

glass-2-leaf-240f03e.gif

And here's what you get from a triple-pane window:

glass-3-leaf-240f04e.gif

glass-3-leaf-240f04e.gif

See the difference? Note the HUGE dip at around 150 Hz, and the general lack of low end isolation? Not nice. Yes, you get better isolation in the high end, but who cares? It's the LOW end that matters for studios (drums, bass, guitars, keyboards...), and the high end is still plenty good. Especially considering that those diagrams are for rather thin glass over rather thin air spaces (3mm glass, 6mm air gaps). Also note that the isolation hardly changed at all! It went from STC-30 with the 2-leaf to STC-31 with 3-leaf: so no change at all, basically. Even considering that the STC rating system does not consider the low end of the spectrum! If it did, the isolation for the 3-leaf would be worse than two-leaf.

As you can see, the article is totally wrong on all of those issues. Whoever wrote it does not have a clue about acoustic theory, or acoustic reality.

Pure garbage. That article even wants you to float your entire window on rubber, twice over, thus creating yet another three-leaf situation! Sigh! Ignore it. There is nothing usable in there, and there's no acoustic reason I'm aware of why you "must avoid square windows". The author seems to be very confused: perhaps he doesn't know the difference between square rooms and square windows?

I'm not quite sure what Rod was trying to get at in the Gearslutz thread, when he mentioned knocking on the glass: he seems to be talking either about the coincidence dip, or maybe it was panel resonance... not very clear. The coincidence dip is always present, for any material, of any size, but with laminated glass it is greatly reduced because of the PVB interlayer. If the glass is acoustic laminated glass (with the thicker acoustic PVB interlayer), then the effect is even smaller:

laminated-glass--coincidence-dip--acoustic-pvb-vs-normal-NAMELESS.jpg

So I'm pretty sure he wasn't talking about that. He was probably talking about panel resonance, which can be a problem with large sheets of "anything", not just glass. However, if you follow his very correct advice of using two different thicknesses of glass for the two sides of the window, then that problem is also minimized.

The reasons why I would be careful with very large panes of glass, are:

1) Cost: Thick laminated glass is expensive!

2) Structural: Building a wall that has a very large pane of glass in it requires a more complex structure, firstly to support the weight of the glass, and secondly to support the weight of the ceiling above it, since you have to take out several studs for wide windows. So very large structural members for the window sill, and also for the window header, with multiple king studs, jack studs, and cripple studs. It can be done, sure, but it's extra complexity and extra cost.

3) Acoustics: Having a big window taking up a large section of one wall means that you cannot place any acoustic treatment at that location of the wall, so you can potentially run into problems with flutter echo, specular reflections, or even SBIR. If you design carefully, keeping those issues in mind, then you can avoid the problems, but once again, it adds complexity to the design.

How do I know that the article is pure garbage and that big windows are fine, if you do them right? Take a look at this studio ( http://www.johnlsayers.com/phpBB2/viewt ... =2&t=21368 ) I designed the control room with large windows on three sides of the room! Look closely: the front window, into the Live Room is 44" wide and 35" high (so early four feet wide by three feet high), and BOTH of the side walls have sliding glass doors on them, that are 61" wide by 76" high! (over five feet wide, and over six feet high). In fact, those side walls are about TWO THIRDS glass, (about 65% of the entire surface area of those side walls is sliding glass door...). Now read through the thread, until you get to the most recent acoustic tests that we have been doing for the final room tuning, and you'll see that the place is working out excellently well.

In other words, there is no need to avoid large glass panels, if you can afford it, and if you do it correctly, taking into account the issues that it could create.

Ignore advice from unknown sources that make unsupported, incorrect statements.

- Stuart -

[SunkenCity]

It was written by Paul Gilby Co-Founder of Sound On Sound but I guess it's out of date info. Yeah the triple leaf thing made me question it a bit but I figured maybe some of the info was still relevant.

What about the mention of using hardwood for the frame?

I haven't read anything about angling the glass for sound reflection, more so to reduce the resonance between the two panes and glare/light reflection.

" It's also common practice to angle the piece of glass on the studio side downwards slightly, which stops the view through the window from being obscured by reflections from studio lights and helps to prevent the build-up of standing waves between the sheets of glass. "

Here It shows rubber or cork under the glass pane(not floating the frame tho) and angling the glass:

" Angles. The two sheets of glass must be at an angle to each other else the two sheets will interact in a resonate sympathy and the sound reduction properties will be reduced. You can angle the glass as in the following drawing but don't forget that the glass can also be angled in the horizontal plane as well as the vertical plane." http://johnlsayers.com/Recmanual/Pages/Windows.htm

This is what I was referencing from Gearslutz:

"Also, I almost never have any studio windows taller than 36" or 90 cm. WAY too much glass and unnecessary for line-of-sight and communication. If budget is a concern, you ARE often much better off with CCTV and monitors.

I every time I see huge expanses of glass in a control room because they are sacrificing the acoustical accuracy of the space for visual impact. I'll repeat: "Form Follows Function". " - John H. Brandt

Now I getting conflicting info from You and Greg about using two panes of glass of different thickness?

[Waka]

I'm sure Stuart will give you some answers to your points when he's free, but I'll try and clarify some things for you.

I haven't read anything about angling the glass for sound reflection, more so to reduce the resonance between the two panes and glare/light reflection.

" It's also common practice to angle the piece of glass on the studio side downwards slightly, which stops the view through the window from being obscured by reflections from studio lights and helps to prevent the build-up of standing waves between the sheets of glass. "

Angling glass for sound reflection is common when designing RFZ based rooms. Stuart and John Sayers both use sliding glass doors extensively from what I've seen. As an example, imagine you are designing your RFZ based room and you want to treat a wall first reflection; you would usually place an angled wall/panel to direct the sound behind the mix position. Does this panel need to be plasterboard/brick? ... No. Glass reflects sounds just as well as an mdf panel right? You could place a sliding door at this point at whatever angle you need, leading to an adjacent room just fine. This would similarly reduce glare. I don't really, understand the standing wave point they mention... why would you care about a null/peak within a window? We care about the mix position... unless I'm missing something.

This is what I was referencing from Gearslutz:

"Also, I almost never have any studio windows taller than 36" or 90 cm. WAY too much glass and unnecessary for line-of-sight and communication. If budget is a concern, you ARE often much better off with CCTV and monitors.

I every time I see huge expanses of glass in a control room because they are sacrificing the acoustical accuracy of the space for visual impact. I'll repeat: "Form Follows Function". " - John H. Brandt

I've noticed John H Brandt in arguments at GearSlutz before, due to him saying that other designs are bad based on pictures, without seeing under the surface.

He seems to be mistaken about the design goals of some of the rooms he's seen with lots of glass. Stuart and John have had world class (literally) "acoustical accuracy" on their designs using big glass doors. True RFZ based rooms (RFZ by reflection not absorption) don't shape the direct sound in any way between the speakers and the mix position. Treatments to the sound field are applied to the sound after it has passed the mix position. There is sometimes treatment behind the speakers to reduce SBIR and reflections, but flush mounted designs are generally better.

In these designs heavy use of glass is perfectly fine, as long as you direct the energy correctly.

Glass doors give excellent line of sight, whilst doubling as doors (two birds with 1 stone). Many mixing engineers LOVE how these huge windows aid their ability to communicate so naturally with the clients.

If John H Brandt's claim that using lots of glass is "form over function" is always true, then how are the worldclass results being achieved in Stuart's and John Sayers rooms? (Check the measurements, they're very real)

Now I getting conflicting info from You and Greg about using two panes of glass of different thickness?

In this case I believe there are two schools of thought. Angling does reduce panel resonance, but if they weren't angled then the cavity would have greater depth on average, so would improve the spring... potato, potato.

In the end design your room on real acoustic principles and logic. Not sweeping statements, that may be out of context. (I didnt read the gearslutz forum that the JH Brandt comment came from).
If you want a big window/door, design your room and see if you can fit it in. If you want it to go where you need a hunk of absorption then DON'T PUT IT THERE
Simples.
Dan