65+ STC Control Room window possible?

Hi all, after lots of reading around and before start building my first recording studio, this is my first post. Is it possible to have an 65+ STC control room window in any way? I've read on the Master Handbook of Acoustics that a carefully contructed double window may reach an 50 STC. Adding a third glass plate adds little. However, someone suggested to me that a 68-70 STC window is possible by using the following design with 4 glass plates: First glass plate of 8mm > air gap of 24mm > Second glass plate of 10mm > main air gap between the gypsum boards (yet unspecified) > third glass plate of 8mm > air gap of 24mm > and finally a glass plate of 6mm. So basically, is something like two double windows? The window structure will be attached on gypsum boards.

Nope- sorry - can't see it. Ask the person who suggested this to you - just how they calculated it - and then bring us back something to look at. Personally I can't see it. If it was just that easy - with glass that thin - I can see companies like Overly building these to replace their existing window lines - which ALL utilize 2 leaf construction (there really is a reason we keep saying this - I am surprised to get so many questions regarding this - it doesn't seem to ever end). Thin for a moment - if it was that easy - to obtain those sort of numbers - (remember that STC really only has to do with frequency ranges of the human vice - so LF transmissions aren't even visited - which is where you'll have your biggest problemwith this design) BUT - if it really was - why isn't there a window manufacturer in the world building these units for studios? Do you suppose they're just too stupid to figure it out? Nope - they've tried and tested every configuration they could think of - and settled in on what provides the best bang for the buck...... Which is why the 3,000 us dollar windows companies like Overly build can only acheive STC ratings of 55 max......... Sorry - but you can't make it to "A" from here........ Sincerely, Rod

Thanks Rod, I was almost sure myself it wasn't possible, but I though to check it out with you guys here. Regards dB

dB, by the way - understand that I was not saying that you can't make an STC 65 window - just that you cannot do it in the manner you were suggesting. You'll never get there with a 4 leaf system - nor with using glass with as little mass as you suggested. Given the right frame assembly- as lot (and I do mean a LOT) of detail to attention - and some extremely thick glass (probably a laminate) it can be done - but not like you suggest. Sincerely, Rod

Rod, On the subject of Glass between Control Rooms and Tracking Rooms, and based on your book, I went to the local glass store to check prices. Your book states that from the different glass you have listed, that lamenient glass is the best for sound isolation. Based off that, I went and priced this glass. They have Lamenient but only I believe either 1/8" or 1/4" thickness only. For a 2ft x 4t piece would cost me $59.00. But, my question is, they also have float glass that is 1/2" thick ($12.00/sq ft). Just looking at the two, it seems the 1/2" would work so much better being as thick as it is (but again, its not laminent). Which would actually work better, the thicker 1/2" float, or the 1/8" or 1/4" laminent glass?? Thanks AJ

Truth is, I've got it wrong in the first place.. Are you aware of any information related to such a window design on the Internet, so I can get an idea? Probably off-topic, but do you think is worth it to go for such a window in order to match the STC ratings of my gypsum boards? Regards dB

newtones wrote:

Truth is, I've got it wrong in the first place.. Are you aware of any information related to such a window design on the Internet, so I can get an idea? Probably off-topic, but do you think is worth it to go for such a window in order to match the STC ratings of my gypsum boards? Regards dB

This is the rule of thumb - if you equal the mass on your wall face - and then increase a glass size to deal with coincidence - you will equal your walls values........ so if the mass of your wall equals 10 psf - then make the least glass mass the same 10psf minimum BTW - you get better isolation dealing with laminate glass - next would be tempered - and last would be simple plate (also known as float). Rod

studio911 wrote:

Rod, On the subject of Glass between Control Rooms and Tracking Rooms, and based on your book, I went to the local glass store to check prices. Your book states that from the different glass you have listed, that lamenient glass is the best for sound isolation. Based off that, I went and priced this glass. They have Lamenient but only I believe either 1/8" or 1/4" thickness only. For a 2ft x 4t piece would cost me $59.00. But, my question is, they also have float glass that is 1/2" thick ($12.00/sq ft). Just looking at the two, it seems the 1/2" would work so much better being as thick as it is (but again, its not laminent). Which would actually work better, the thicker 1/2" float, or the 1/8" or 1/4" laminent glass?? Thanks AJ

AJ - back to basic - just as i explained in the book - You're dealing with mass......... so look at chapter 5 where I go through the exercise for you..... I said:

Remember the basics—it’s all about mass. That doesn’t change just because the material changes. For example, if you have two layers of 5/8" drywall on each side of your wall, then the mass = 2×2.625 psf (per layer) or 5.25 psf of mass (on each side of the wall) for the drywall. Standard plate glass (annealed) weighs 1.64 psf for glass 1/8" thick. Thus, a 3/8" piece of annealed weighs 4.92 psf (a little light), so you need a piece of 1/2" for one side and 3/4" for the other. Thus, the glass weights will be 6.56 psf and 9.84 psf, respectively. Don’t worry about the fact that the glass weighs more than the wall—remember the added benefi t you get from thicker glass with the lower coincidence effect. That, plus the fact that the coincidence level for each piece of glazing is different, will help you to increase isolation. Because of this, the wall assembly surrounding the window will be your weakest point, and the effective isolation will be as if you had never penetrated the wall at all.

Now- those numbers are using simple plate (float glass) , so this now turns to you with the question of - what is your mass on each wall face? To answer your other question - I would not even consider (for that same wall ) less than one 3/8" and one 1/2" leaf of laminated glass - 1/4" and1/8" will be useless. I also have to let you know that although the numbers might indicate STC ratings for your walls that high - in the real world you probably won't get there when you take into account what may exist with flanking as well as construction defects that might have crept in along the way......... I hope that helped. Rod

Hi Rod, Been thinking about replacing one side of glass in my studio. I have a double wall (two seperate frames), one layer 13mm plaster board on one side and two layers 13mm plasterboard on the other side. 150mm air gap. The current window is one pane of 8mm laminated glass on each side. I was thinking of replacing one side but not sure what thickness to go to and what added benefit verse cost ($200) I will acheive. Any pointers appreciated. JohnG

Johnrg wrote:

Hi Rod, Been thinking about replacing one side of glass in my studio. I have a double wall (two seperate frames), one layer 13mm plaster board on one side and two layers 13mm plasterboard on the other side. 150mm air gap. The current window is one pane of 8mm laminated glass on each side. I was thinking of replacing one side but not sure what thickness to go to and what added benefit verse cost ($200) I will acheive. Any pointers appreciated. JohnG

RAL-TL95-301A 1/4" Lam. - 4" AS** - 1/4" Lam TL Freq. 24 100 37 125 39 160 38 200 41 250 44 315 47 400 49 500 51 630 53 800 54 1000 54 1250 54 1600 53 2000 57 2500 60 3150 63 4000 62 5000 52 STC 38 OITC 51 Rw (UNSEALED) Figuring that you have a simple 2x6 wall with only one layer of 1/2" one side - 2 layers the other - yoiu'd be throwing your money away to increase the window values -= they already pretty much match or exceed the wall. Rod