Angled walls or not ?

DeadPoet

DeadPoet

carpe diem
hi,

this is from another thread which I hijacked....


Originally posted by Michael Jones
Parallel walls create standing waves. That is, the sound waves bounce directly off of one wall, and then interefere with sound waves comming from the source as the reflected wave heads directly back to the source. When this happens, some frequencies are cancelled out and others are boosted. This doesn't give an accurate representation of the music or sound being recorded. Angled walls, because reflected sound doesn't bounce directly back, eliminates this phenomena.
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Yup, I know this stuff.

As far as the math goes, I have to disagree. Its just as easy to measure and cut a 12 degree angle as it is to measure and cut a 90 degree angle. Likewise its as easy to measure and cut a dimension of 6'-5 11/16" as it is to measure and cut a dimension of 6'-6".
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I know this too. My referral too 'the maths are more difficult' meant: calculating the modes for a non-rectangular room is far more difficult to do right than it is for a rectangular room.

That's like the statement that studio windows HAVE to be angled..that's just for reflection convenience, not for acoustic purpouse.

A good site is : exposing acoustical myths

Maybe John can help us here ?? Are non-rectangular rooms easier to get right ??



Herwig
 
Yeah I had the same question a couple of months ago but the answers were kinda fuzzy. Would love to hear more about that subject. Thanks.
 
Myth No 1.

In control room design you splay the walls to stop standing waves.

You splay the walls to control the reflections from the speakers. The aim is to avoid getting a reflection of the right speaker in the left ear.
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You splay the walls in studios to stop standing waves. Go and clap your hands in a square room and you will hear the standing waves and the pinging sound it produces. You can easily stop it in the high frequencies with some absorption material but the low end is another story. - splaying the walls is just damn easier.

Myth No 2.

you angle the glass in windows to stop standing waves.[i/]

Well - its not a myth. Parallel glass will resonate as will parallel doors, or walls. Do you really believe that major studio designers angle the glass windows and doors for some mythical reason??

OK Their myths:
Myth No. 1: Absorption improves transmission loss

Yes it does. When a wave hits a wall it can do one of three things.
1 - it can be reflected.
2 - it can be absorbed
3 - it can be transmitted through the wall.

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If the incident wave travels through 10 feet of absorption before it hits the wall the amount of signal transmitted will be less.

so absorption can improve transmission loss.

cheers
john
 
I believe that the Auralex guy prefers square rooms so we can buy more stuff from them?
All sarcasm aside, it makes better sense now. Is there a precise angle for the walls to be at (at least in the CR)? Well I kind of get it, since we want to deflect the signal from the speakers. Glad I can still remember my geometry classes! Thanks John and Michael.
 
BTW does it make a difference by not having the speakers "in-walled" (sorry can't find the correct term)?
 
Thanks again! I've been to the SAE site but did not memorize all of it (so much good stuff over there!). I'll make sure to dig thru it before posting any dumb question next time ;)
 
Originally posted by John Sayers
[Myth No 2.
you angle the glass in windows to stop standing waves.

Well - its not a myth. Parallel glass will resonate as will parallel doors, or walls. Do you really believe that major studio designers angle the glass windows and doors for some mythical reason??
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John,

I think the problem for this is not that the parallel glass won't resonate. I think the author was trying to say that any benefit of angling (to reduce the standing waves) will be negated by moving the bottom of the both glass panes inward --> reducing the overall air space --> reducing Sound Transmission Loss.

I guess in an ideal situation the air gap between the glass panes is large enough that moving the bottom of the panes inward is not factor.

I also read this exact same thing in Mike Shea's book. Budget Studio Recording (which is me,:D:D, very low budget,:D :D )

BUT, then again I have NO real world practical knowledge on the subject therefore, I am not sure. I'm kind of like a fresh engineer out of school, I can tell you what the book says, But don't know how it really works. This is why we have people like you to help us.

larry
 
Sure - but if you mount your window jam correctly the bottom is at the wall width and the top is even wider, increasing STC.

cheers
john
 
John,

That makes complete sense, So for a 4 inch wall put the bottom space at about 3.5" and build the top to about 6". Angling the sides coming out of the wall.

Damn, I didn't think about that!:( . Its too late for me. Well like I said John, NO practical experience.

Build the top out, man why didn't I think of that. That's even better. Oh the pains of being a newbie.:eek:

larry
 
OK John,

I read your reply again, and I am absolutely in amazement. I am dumb founded to the nth degree!

Why, oh why didn't I build my windows like that,

WWAAAAAAAAAAAHHHHHHH, sob, sob, sob. curse, curse. @#$%$@$$!!!!!!.

:( :( :( :mad: :mad: :mad: :( :( :( :eek: :eek: :eek: :confused: :confused: :confused: :confused: :o :o :o


larry
 
WHAT and replace $367 worth of glass,

hmmmmmm..............

I think i'll just wipe my tears and suck it up.:) :)

larry
 
:confused:


Thanks for the reply John. I'm reading too much to be good. Read 5 opinions on studio design and you get five different studios. This is so confusing. Will resume to playing Freecell for the rest of my days.



Herwig
 
Read 5 opinions on studio design and you get five different studios
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Yeah it was easier when I first started posting acoustics and studio design stuff, no one knew what a RC was or what STC meant, now every tom dick and harry has an acoustics page ;);)

cheers
john
 
charoo do like i'm gonna do:
lock yourself in, unplug the phone, get food and supplies for at least 2 weeks, send your wife/girlfriend to her mom (or on a Paris shopping spree!). Then log on the AES website and DIG! :) When you don't understand something allow yourself 2 days of heavy pondering and thinking and if it still does not make sense then post it here.

:D

(Resilient Channel?)
 
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