John Sayers' Recording Studio Design Forum Archive

so ive come to find out glass is incredibly expensive. what if i bought 3 peices of lexan plastic, expoxy/welded 2 of them together, to make one sheet, then used the third one 4 inches away tilted slightly,

would that be fine for CR window instead of glass?


Ian

freakk guitarist wrote:so ive come to find out glass is incredibly expensive. what if i bought 3 peices of lexan plastic, expoxy/welded 2 of them together, to make one sheet, then used the third one 4 inches away tilted slightly,

would that be fine for CR window instead of glass?


Ian

To be honest I'm not sure. However, from what I've read here and elsewhere, Lexan is just not heavy enough to be effective.

I looked for quite a while several months back trying to find info on plexi/lexan, not much out there. Gluing can cause transparency problems, the mass isn't there for very good TL, and with that narrow a gap you don't want to tilt. You need all the air gap you can get.

I've heard of a couple people finding those heavy, glass-topped coffee tables at garage sales and using that glass with pretty good results - you'd want different mass in each of the two glasses, but some of the older "modern" styled tables just used a heavy (maybe 3/4" glass resting on padded steel frames - might be worth looking around a bit... Steve

darn, i was really hoping it would work good, i heard that when you weld two peice of lexan together, its totally transparent too, cuz the liquid you put on the plastic just melts it a little. so you dont think one side thats almost an inch thick, then another one thats a few inches out and 1/4 inch, i really cant afford glass, and i need to make 2 windows, so finding a bunch of tables would be tough. do i have any other options, besides totally sealing my rooms, and using security cameras ha ha.

freakk guitarist wrote:darn, i was really hoping it would work good, i heard that when you weld two peice of lexan together, its totally transparent too, cuz the liquid you put on the plastic just melts it a little. so you dont think one side thats almost an inch thick, then another one thats a few inches out and 1/4 inch, i really cant afford glass, and i need to make 2 windows, so finding a bunch of tables would be tough. do i have any other options, besides totally sealing my rooms, and using security cameras ha ha.

I actually know someone that uses security cameras and it works suprisingly well. What are you recording? Is it just vocals? If you don't plan on tracking drums are loud guitar perhaps you can give the ole college try. If you really have no other option than it is what it is.

freak,

There really is no cheap way around this issue. As has been said, Lexan, etc., hasn't got the mass to do a satisfactory job..........you would need fairly thick sheets to come anywhere near the properties of glass.

Ideally the glass should be (at least) 10mm (3/8") and 6mm (1/4") with the thicker sheet on the side were the sound originates or as has been said, on the side where the sound is loudest. Having dis-similar thicknesses means the chance of the sympathetic resonance between the sheets is greatly reduced. Also, laminated glass is more suitable than toughened glass due to the synthetic membrane which bonds the two thin sheets together. The membrane helps reduce the tendency for the glass to resonate........some manufacturers produce a specific laminate for acoustic reduction, it has a thicker membrane than standard laminated glass, but of course costs somewhat more.

Tests carried out to determine the best methods for acoustical insulation in windows have virtually proven that angling the sheets does little to reduce the amount of sound transfer..........what is achieved by angling the sheets in studio windows is that visible reflections between the two sheets are minimised, thereby keeping visibility at a premium. Obviously, if the construction of the framework and installation of the glass is not correct you will probably be fighting a losing battle.



Steve, I took this from my post at "that" other site.........maybe your follow up there would be useful here.

ChrisO

Chris, site's busy ATM - the only thing I'd change in your comments is the location of the heavier glass - walls/windows aren't diodes, so either direction works the same; what does make a diff, is having the mass of the glass match the mass of the wall. This means that the heavier glass should go on the side of the wall with the heavier leaf, and since glass is about 3x the weight of gypsum using just over 1/3 the thickness of the total wallboard thickness for each side of the wall is optimum. As in walls, more air = better... Steve

As for the person who suggested old glass topped coffee tables most of those are tempered glass and cannot be recut to a new size.

It is true that the membrane in laminated glass should provide some viscoelastic benefit.

That person was me, and that's a good point - a person would need to find two identical sized coffee tables only with different thickness of the tops, then design the window frame around the size glass you have. Still, if you're a good scrounger you might save several hundred $$ with some perseverance.

Yes, the laminated glass (as opposed to tempered or float plate) can improve STC by as much as 6-8 dB from what I've read... Steve