two double windows equals bad idea?

Hi. I'm building a rom within a room in my tracking room. In order to let some daylight in I naturally want a window. The window on the excisting wall is a double layer (thermal) window. So is the one I've been offered to buy dirt cheap. The question is...does a double window act as a single og double leaf...and will two double layer windows be allright or should I go for a single layer glass and build the window myself instead...there will be a 10 cm air gap between the main wall and the new wall. Cheers, Lasso.

Sorry, but yes - this WILL act as a 4-leaf partition. If you were only interested in blocking some specific midrange, it might work better than a 2-leaf; but for music, you want two panes of glass as far apart as your frames allow, and at least the same mass as your wall material. for gypsum, each glass should be slightly less than 1/3 the thickness of gypsum on each side of the wall... Steve

It's time for you to realize, like many others before you, that sunlight is bad. We don't need to stinkin' sun. It really is so over rated. In all seriousnous, I actually really like that I can't tell what time of day it is when I'm down here. That way if I'm recording a band we set our own pace and everyone isn't getting tired when they realize it's getting dark outside. Down here it's always the same brightness. There's no sunlight glaring on my monitor making it hard to work.

Thanks for the rapid response!!!...hmm...I have no option of altering the existing windows...it's a rented facility...so I'd be better off with no window on the new structure at all....or would a single layer glass be ok? I'm ofcourse not interested in biulding a completely new structure and floating floor only to discover that the windows are useless sound proofing wise. Better without the daylight then?

Windows will always be a weak point in soundproofing. The reason we live with that fact with control room windows is because we're sacrificing some isolation for the convenience of communication. There are some ways to cover a window without altering the structure. I've seen some drawings around here that I never paid attention to because I didn't need to. You might be able to find them somewhere.

on the same what about the case where I am building the inner wall (2 gypsumboards + sheetrock on metal frame) as an addition to an existing wall with windows (which are old and will be repalced anyhow) ? Will a triple pane window with different distanced between each glass be sufficient? Should this be framed on the new inner wall or on the outer one? thanks

Guys, first off you CAN equal a wall's performance with glass; if you use at least 1/3 of the gypsum thickness on each half of a 2-leaf wall for your glass thickness, and you VENT the window area into the wall area where there is insulation to help absorb pressure variations, and you make good SEALS all around for both glasses, it can be done. It works a bit better if you can afford laminated safety glass instead of float plate or tempered glass, because the laminations act similar to Green Glue, as a Constrained Layer Damping material. Second, there is NO case where using ANYTHING other than TWO panes of glass separated by as much space as your wall allows, will work well for music isolation. Mass-air-mass is the only practical way to get decent isolation at all frequencies. Period. The minute you add any more layers or air gaps, you LOSE. Lasso, if you have ENOUGH space between the existing double pane and your desired add-on, and you can find a HEAVY glass for the add-on, it may give a bit better results than just the double pane that's already there; I have no sane way of calculating multi-leaf walls so I can't give you a band-specific TL for such a window; I only know that it won't be very good at low frequencies, and that at one point in the midrange it will be BETTER than a 2-leaf by maybe a couple of dB. whatalob, a triple-paned window will NOT keep up with a double paned one - your inner mass leaf and your inner glass should line up, as should your outer ones. Also, what are you referring to as "sheet rock" - gypsum and sheet rock are the same thing... Steve

Yeah I guess I kind of forgot that glass can be just as effective at stopping sound as the wall if you make it thick enough glass, the right kind of glass, and seperate the two pieces by enough dead air. I stand corrected. But if you use cheaper glass it more than likely will not be as effective.

Steve - thx for the reply apologies btw. I meant rockwool but I hadn't realised sheetrock is the same as gypsumboard (i might take the opportunity here to stress the fact that for non-native english speakers the construction lingo and material terminology can be harder to grasp than the actual acoustics. Not that there is something that can be done about that) Anyway, I have a couple of relevant questions: In the case of windows to the outside world and in the two pane window scenario is it best to angle the panes, like in the control to live room scenario? I have read the 'acoustical myths' document where it denies the need for that, as well as numerous ones that still disagree, but am still unclear on the issue. Also will the presence of two fairly large windows (1,90 x 1,30 m) act as a reflective surface to totally mess up the acoustics? thanks again tas

The main reason for angling the two panes of glass is visual reflections. I've had temporary plexy glass in my control room window for over a year now and for about half that time I had the two "panes" horizontal and if the lights were off in the live room, you'd see yourself 4 times in the reflections. If you angle each peice even slightly it removes the hall of mirrors effect. Now I've got my temporary plexy glass angled and it's much better.

Yeah, this is another of those situations where acoustics, ergonomics and aesthetics are at odds with each other. Visual reflections can be very distracting, acoustic reflections can cause you to have to build portable absorbers to put in place while mixing, and sound isolation needs maximum air gap and mass. It's like a lot of life; compromises are necessary. It's just good to know what you're giving up when you DO compromise - and what other effects will result when you change something. IIRC, the main point in the "acoustic myths" article was the one that says splayed glass improves isolation by reducing flutter between the glasses; this has very little if anything to do with it. But if you get too carried away tilting glasses, you WILL notice a reduction of isolation; it's caused by the narrower air gap... Steve

Unless you've got a 2 foot thick wall like me and you've got a little room to spare. :) Most people only have 7 inches to play with or so, I literally have 22 inches. It's because the support beam for my house just happened to run between the two walls for my control room to live room wall, so I used that to my advantage.

guys, regarding the window to the outside worls issue again ... it just occured to me: If I was to construct the special two fat single pane windows aligned to the frames as mentioned above, would I have sufficient thermal insulation?

Better than with any commercial "insulated" glass; the wider air space (vented into the insulation-filled cavity between inner and outer wall leaves) will work for thermal insulation as well as sound insulation... Steve