Double glass window (maximum) spacing?

Hi, we're about to install glass windows between the control room and recording room with a typical double-wall construction. From reading this forum and other places, I have always gotten the impression that the more air between the window panes (leafs), the better the transmission loss, but my glass supplier tells me we should not space them more than 9cm (3.54 inches) apart because of resonance issues. Is this true? I'd like to space them as far apart as possible, around 20cm (7.8 inches). Will this pose a problem? The two glass panes are one 10mm laminated and one 8mm solid glass. Thanks for your help :) ed

edb wrote:

From reading this forum and other places, I have always gotten the impression that the more air between the window panes (leafs), the better the transmission loss, but my glass supplier tells me we should not space them more than 9cm (3.54 inches) apart because of resonance issues. Is this true? I'd like to space them as far apart as possible, around 20cm (7.8 inches). Will this pose a problem?

:) Tell your glass supplier he's a fun guy. And no your 20 cm will not cause problems. Maybe a bit background. In fact there are 2 influencing parameters. 1) enlarging the cavity lower the msm resonance which can only be good and enhances your transmission loss. Here the air act as a spring. 2) A second thing that influences TL (transmission loss) are the cavity resonances. They are a bit comparable with axial modes between the panes. It is this phenomenon that causes this downward bend (not referring to the coincidence or critical frequency but an area starting before) in the TL curve. It's based on this that the idea aroze to angles panes versus one another. Indeed this phenomenon lowers in frequency by increasing cavity width. However this phenomenon is less important in the overal picture. Hence: Your idea to maximize space is very, very OK.

greetings, from the way i understand it, I think your safe from resonant issues since your using laminate glass AND your glass panes are two different thicknesses. (both help independantly from each other, and the laminate is even more resistant to resonant issues) (again, at their own frequency issues) but it was nice of the glass guy to mention it! btw.. i remember reading that isolation values are greatest with greater distance, however, they begin to lessen after 12"... (most bang for yer buck) haha... eric just responded as i was typing this.. so follow his response! good luck sandled

Thank you very much guys! I'll let you know how it turns out :) ed

This is not the first time that a glass company representative has given bad advice on studio construction, nor will it be the last. ;-) I don't mean to slam those guys -- studio construction is very unique... but it's bad when they state such things in certain terms. --Keith :mrgreen: