Angled walls or not ?

[ebeam]

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.

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.

To go back to the original question a bit...

John, I understand that with a control room when you are trying to create a reflection-free zone, its a good idea to angle the walls. However, in a tracking space, what you're generally trying to do (dimensionally) is create a room with a nice distribution of modes so the room resonates equally (or pleasingly at least) at all frequencies, right?

If that's the case, its a lot easier to calculate good dimensions for a square room and that's what DeadPoet is getting at. Otherwise you'd end up guessing to a large extent. As I understand it, the main effect of splaying a wall is creating some diffusion, which helps control flutter echo, etc. Seems like a pretty elaborate way to get diffusion. I suppose what I'm getting at is wouldn't it generally be easier and more successful overall to a) design a room with 'golden' dimensions, b) add diffusors to break up surfaces to treat flutter and c) add some absorbers where necessary?

I'm sure you've been in a lot of great sounding rooms, so have they always had splayed walls? Have you been in any great rooms with parallel walls?

Thanks.

 

[John Sayers]

ebeam - I can see where you are coming from but show me a diffusor that operates in the low frequencies. They are fine for mid - high frequencies but in the low end they have to be huge.

cheers
john

 

[ebeam]

Right, but ins't flutter echo more of a mid/high frequency problem?

 

[John Sayers]

Yes but I'm refering to low frequency standing waves, you know, that experience you get when you walk around a room and you can hear the low end changing as you move in and out of additions and subtractions caused by standing waves.

cheers
john

 

[chippyd]

by how much do we need to move the wall so its not a Parallel wall anymore?

are we talking moving the wall one inch inwards at one end or one foot ?

are there any computer programs to show what would happen when moving a wall non-Parallel?

 

[John Sayers]

No computer programs I know of but from my experience it has to be around 12 degrees.

cheers
john

 

[ebeam]

Thanks John.

OK, standing waves can be a problem, but you still have them with angled walls. The intensity of the peaks and valleys may be somewhat diminished due to diffusion effects, but they are still there - just not as uniformly distributed throughout the room. There is a series of illustrations in the Everest book showing the effect of splaying walls on standing waves at different frequencies that shows this pretty well.

I obviously don't know this stuff from personal experience like you do, but in what I've read (Everest in particular) they say that the benefits of splaying walls are outweighed by the reduction in room size and difficulty in determining good room dimensions to get a good modal distribution.

Anyway, thanks for the input. It seems everyone does have their own opinion on acoustic design, but I guess everyone has different tastes when it comes to how a room sounds. I like trying to understand things from theoretical standpoint, but maybe that approach breaks down here....

 

[DeadPoet]

thanks ebeam, you say the things I meant to say, but words, time and knowledge of English failed me.
Everest was indeed my main source of inspiration on the start of this thread, but interestingly a similar discussion is being conducted in the yahoo acoustics group.


John, all of your comments make sense, but so do all of Everest and ebeams..


Herwig