Slanted or straigt window?

Hello, I'm sorry if this allready has been covered. What is most preferable, straight or slanted windows between control room and studio room? Seems like there are different opinions on this one... keep it comming.

Since you want optimum isolation between the two rooms you want as much space between the sheets of glass as possible. Putting them straight will do just that. So it'll perform slightly better than slanted concerning isolation. Visibility on slanted windows is a bit better (less reflection/mirror-effect). When slanting windows upwards waves might be reflected a bit towards your cloud (absorption). Tho, the effect is minimal. I'd go with straight mounted windows, but it's up to you. :)

Ro wrote:

Since you want optimum isolation between the two rooms you want as much space between the sheets of glass as possible. Putting them straight will do just that. So it'll perform slightly better than slanted concerning isolation. Visibility on slanted windows is a bit better (less reflection/mirror-effect). When slanting windows upwards waves might be reflected a bit towards your cloud (absorption). Tho, the effect is minimal. I'd go with straight mounted windows, but it's up to you. :)

Then I'll do that. Thank you.

put them up temporarily and check the reflections before deciding - with straight you can get reflections off into the distance which can be annoying.

put them up temporarily and check the reflections before deciding

You mean visual reflections, John? As in lights and things being reflected by the glass, making it hard to see through? Or are you talking about acoustic reflections off the glass? - Stuart -

yeah - where you work you could look in the window and see yourself, over and over distracting you from who you are trying to see, the artist, especially when the ilights are down in the studio for moooood :)

In most of the higher-end commercial post-production studios in London, they go for slanted two or three leaf windows, with different thickness for each leaf - in the case of the three leaf design the middle one is vertical, and the slanted ones are facing toward the floor like in my window design here: http://www.johnlsayers.com/phpBB2/viewtopic.php?f=2&t=13149&p=90381#p90381. I don't know much about acoustics (I'm only a voiceover guy after all :mrgreen: ) and I always thought and was told few time that the glass sheet not being parallel was a good thing acoustically-wise as the sound would be dissipated easier between the two sheets that way, and the slanting toward floor being that way to avoid visual reflections toward the engineer or the voiceover talent - I've been in few studios where the glass was slanted toward the ceiling and being blinded by the reflections of the halogen lights while reading your script is not that fun... But is the acoustic theory a myth, is it simply because of visual reflection? And if so, why do some studios slant it toward the frigging ceiling, making it even worse that having the glass vertical? Would anyone be able to shed the light on that once and for all?

French - John told you the right of it....... as did RO. Parallel glass is maximum isolation - but you stand the risk of having (visual) reflections affect the comfortable use of the window. Give exactly the same mass - a 2 leaf system will out-perform a 3 leaf system. There is NO truth to the claim that you increase isolation between glazing leafs by splaying the windows. The fact is just the opposite - you loose some isolation because of the loss in the spring system that is created within the free air space....... Rod

I'm paraphrasing what Rod Gervais says about slanting glass: basically, it has no acoustical benefits, is detrimental to isolation, and only has visual benefits (the ones John mentioned). To get maximum isolation, you need maximum air gap between the panes. If you angle the glass, then you no longer have maximum isolation, since the two panes of glass will be closer together on one side. Regarding acoustic reflections off the glass, EG a singer's voice reflecting back off the glass into the mic: if you angle the glass then all that you accomplish is that the reflection comes back from a different point on the glass, but it still comes back (unless you set the glass at a really huge angle). Rod makes other very convincing arguments too, but those are the ones I recall off-hand. So like John said: the only reason you need to angle glass is to avoid those annoying visual reflections. Intelligent placing of lights helps a lot with that, too! If the positions of people, lights and windows are figured carefully beforehand, then those reflections can be minimized such that the glass only needs to be angled as little as possible. Like André always says: building a studio right is 90% about designing it right, and only 10% about actual construction. I'm curious about those studios you mentioned with three leaves of glass: They would have to use pretty thick glass in all three panes to counteract the loss of low-end isolation from the three-leaf effect. I wonder why they do that? - Stuart -

Thanks guys what yo usay does make sense, the spring effect Rod mentions is a very convincing argument indeed that even a phillistine would understand (ie. me for instance), and Stuart's point are not less convincing... So as it's now established that it's purely for preventing reflections from blinding the engineer/talent, then why oh why do some slant the glass toward the ceiling blinding us even more in the process! Stuart, yes the glass used in those studios is very, very thick - we're talking about very 'money no object when building' type high-end facilites, charging the price of a small mortgage per hour... As to why they do that, I'm only the guy talking in the mic!

then why oh why do some slant the glass toward the ceiling blinding us even more in the process!

Because they thought it would look kewl- and never bothered to think it all the way through...... They probably said (somewhere along the way) "everyone always slants their windows in at the bottom - why not slant them in at the top - set ourselves apart from the rest - wouldn't that just look too cool?" Oh well - go figure....... Rod

And you know what Rod? Chances are, you're right.

I had a conversation with Bob Hodas a well known room/speaker tuner, who informed me that unless the window is tilted at more than 10 degrees he often has to puts a curtain in front of it to clean up stereo imaging problems caused by sound bouncing off the glass. Anyone have experience with such a situation.

Anyone have experience with such a situation.

No.

bluesbaz wrote:

I had a conversation with Bob Hodas a well known room/speaker tuner, who informed me that unless the window is tilted at more than 10 degrees he often has to puts a curtain in front of it to clean up stereo imaging problems caused by sound bouncing off the glass. Anyone have experience with such a situation.

funny, so he tunes it with curtains closed. When removing the curtains, hell you wanna see through the window, not?, the stereo image is altered... :blah:

"I'm paraphrasing what Rod Gervais says about slanting glass: basically, it has no acoustical benefits, is detrimental to isolation, and only has visual benefits (the ones John mentioned). To get maximum isolation, you need maximum air gap between the panes. If you angle the glass, then you no longer have maximum isolation, since the two panes of glass will be closer together on one side." Does the parallel, better isolation theory apply in this situation? I have a 14" gap between walls. Still trying to figure out what to use to fill the cavity.

John Sayers wrote:

Anyone have experience with such a situation.

No.

Neither have I....... but that is a stange statement on the face of it - and Bob is a pretty sharp fellow. The reception area (for a reflected sound) based on the angle of reflection from the window back to the listeners position is a 3 part function - part 1 being the location of the speakers, part 2 being the distance of the listeners ears to the window(along with their height in relation to the speakers) - the 3rd (then) being the angle required for the window to deflect the sound below the listeners ears (preferably into the back of the board so as to not have reflections from the board screw things up). So what would work 5' from the window would not work if your board was tight up to the wall........ likewise - you would require less angle the greater the distance you are from the window....... It is not as clear cut as less than 10 degrees doesn't work....... 10 degrees works real well in a whole lot of situations......... Rod

BTW - you can easily deal with the lost spring (in splayed windows) by just slightly increasing the mass of the glass.....

That's good to know Rod - I personally plan to put 20mm lamin glass on CR side and 15mm lamin glass on VO booth sid so I guess that'll be alright. BTW who's that man behind the curtain? Does he pay rent?