Design ideas for space constraints?

giles117 · Post by **giles117** » Mon Jun 23, 2003 4:19 pm

One last Question

On my front side walls should I angle each wall 6 degrees or 12 degrees.

Bryan

Eric_Desart · Post by **Eric_Desart** » Mon Jun 23, 2003 8:03 pm

John Sayers wrote: Bryan- For rooms like this there are two major factors. The angled walls not only stop the standing waves they direct the sound down the room to the rear wall.
cheers
john

John,

You shouldn't say that anymore:
Standing waves are room modes and room modes are standing waves.

The shape of a room can change the shape of a standing wave pattern, but can't get the room modes disappear.
Any room shape, angled walls or not has its own standing wave pattern (modal behavior).

Even an official reverberation room (ca 200 m^3 to more), without having ANY parallel walls/floor/ceiling and additionally lots of large bended diffusers has its modes.
In those lower frequencies up to 12 measurements with 6 different microphone positions and two different source positions must average this soundfield distorted by modal behavior (often substituted by rotating microphones).
This modal behavior is the main cause, that they have a lower cutoff frequency arround 100 Hz.

The only way to get rid of room modes is:

a) Absorb them
b) Not excite them by shifting source to the nodes.

In a room with angled walls the frequency of the modes, will remain about equal than in a rectangular room with ca same floor surface (using averaged x, y, z axis measures). Only the resulting pattern can be more irregular spaced. But they are there as explicit as in a rectangular space.
Exact behavior and pattern can be calculated with FEM software (not with analytic formulae as in rectangular spaces).

Angling wall has mainly effect on geometric acoustics, which is a gradual thing roughly from 2 to 5 times the Schroeder frequency and higher.
See also my message about the rounded corners room somewhere.
http://johnlsayers.com/phpBB2/viewtopic.php?t=339

Look at:
http://ceae.colorado.edu/~muehleis/clas ... waves.html
see comment at heading:
Important Note: Non parallel walls.

See also at:
http://home.tir.com/~ms/roomacoustics/r ... stics.html

Kind regards
Eric

giles117 · Post by **giles117** » Mon Jun 23, 2003 11:00 pm

So Eric,

In Laymens terms..... What does that mean to me?

Bryan

Eric_Desart · Post by **Eric_Desart** » Tue Jun 24, 2003 2:21 am

Bryan,

That you still can do as John suggests, he certainly has the practical experience.

I'm only setting the physics straigth, meaning your room treatment has to take care of the room modes (and speaker position in very specific cases can help out) and it's not the shape of the room.

Also angled wall can disrupt this mode pattern, which depending in the mic position can be positive but also negative.
Go with John's experience.
I'meant the message in fact for him in order to take this into account.

One can do this on experience, or one can simulate such fields in FEM software (Finite Element Method).
The first has proven its value too.

Best regards
Eric

giles117 · Post by **giles117** » Tue Jun 24, 2003 6:13 am

Ok, I understand your indication of the physics. This happens to be a Mix room so microphone placement is not an issue.

Your information gave me pause to inquire as to the effects of the modes which I understand do not disappear, just chnage, with regards to my mixing and not having issues with standing waves smearing the imaging I see when mixing.

If you could comment with relation to those needs that is appreciated however if your physics data has no audible bearing on my Real World Application, please let me know that as well.

This is a very important issue with me at this time as Mixing is my Main source of income.

So once again in Laymens terms what effect does that have on what I am doing.

(I am looking for a simple answer not one That will fly over my head.) I am a mix engineer not an acoustician nor do I desire to become knowledgeable in this area. So in the words of many a great man. KIS (Keep it Simple)

Bryan Giles

Eric_Desart · Post by **Eric_Desart** » Tue Jun 24, 2003 6:45 am

Hello Brian,

I thougth I made that clear by saying:

.....That you still can do as John suggests, he certainly has the practical experience........

and
......Go with John's experience.......

and
..... One can do this on experience ..... The first has proven its value too.

and
..... I'meant the message in fact for him in order to take this into account. ....

I am who I am, and my background is physics specialized towards acoustics.
I did not want to correct any advise John gave, just hint him to take the points I stated into acount.

Best regards
Eric

PS: I don't like your demanding, pushy and disrespectful tone.
What I did/shared is for free to help.
Everybody has rights but duties are the rights of others.

giles117 · Post by **giles117** » Wed Jun 25, 2003 12:10 am

Sorry if I offended you. It was not my intent.

Because of the technical nature of your reply to me it made me hesitant and cautious. As a meticulous Mix Engineer I have an obligation to challenge eveything and test everything.

I was in no wise intending disrespect. I just need concrete answers. Nothing left to the imagination. We live in a society that encourages freedom of speech and freedom of expression of opinions. If that offended you, I again apologize.

Bryan Giles

BTW when I inquired of you I was very specific in requesting, "please put it in laymens terms". Hence why I became very aggressive in my desire to seek an answer.

And remember... Let it roll off like water on a ducks back. Your opinions and knowledge are greatly respected in this forum and I respect them very much as well.

Thanks for reading.

Eric_Desart · Post by **Eric_Desart** » Wed Jun 25, 2003 12:40 am

Hello Brian,

It's Ok let's forget it.

On your original request:
.....please put it in laymens terms....

I responded:
.......Bryan,
That you still can do as John suggests, he certainly has the practical experience.
I'm only setting the physics straigth,........

I hadn't checked the whole thread, since I'm certain that John did and does a perfect John and is very experienced.
Therefore I clearly directed my first response to John. I think it can be important that John should know that he can't count on the angled walls to solve the modal behavior.
Since probably the modal behavior is controlled by absorption anyhow, I left it up to John to judge that. And I'm 10^6% certain if John believes he must redirect his advice a bit that he will.

So I limit my contributions to principle things and basics (also time consuming), which I hope can indirectly be of help.

Anyhow thanks for your nice words.
Best regards
Eric

Post by **John Sayers** » Wed Jun 25, 2003 10:16 am

Hi Eric - I understand exactly what you are saying and you are right - I shouldn't say it....... but I suppose, like Bryan, I'm trying to keep it simple. I am recommending angleing the walls to direct the sound to the rearwall where it should be absorbed and to stop side reflections disturbing the imaging.

cheers
john

Eric_Desart · Post by **Eric_Desart** » Thu Jun 26, 2003 12:50 am

Hello John,

Thanks.

Still, I believe it's important to emphasize for readers, that you can't direct the room mode frequencies (which can be more powerful than traveling waves).
They are there or they aren't. They don't go anywhere. There are as static as can be (therfore called standing waves).

Regards
Eric