Hi there
I am in the process to set up a 12 x 6 x 2.7 listening room and I have
2 concerns
- ceiling height may be too small @2.7 and I am worried about the 1st
reflection which can damage the ETC response - and then the vertical
imaging capabilities of my system
- ceiling have vaults. I am worried about focusing of the sound energy
My plan is to hang some diffuser / abosrber panels to catter ceiling
reflection and get rid of both issues above.
Another point is to shorten the room - e.g. from 12 to 10 - to make the
dimension ration more room-resonaces firendly

The room is also rather wet and I wonder if this is of concern for the
audio system. Any comment on this?

many thanks to who'll reply

Andy,

I am in the process to set up a 12 x 6 x 2.7 listening room

Is that feet or meters? My advice will be very different for each!

My plan is to hang some diffuser / abosrber panels to catter ceiling
reflection and get rid of both issues above.

You'll also need a fair amount of bass trapping if you hope to get any sort
of even low end response.

Let me know about feet or meters, and in the mean time have a look at my
Acoustics FAQ:

www.ethanwiner.com/acoustics.html

--Ethan

On Tue, 6 Sep 2005 12:08:49 -0400, Ethan Winer wrote:

Andy,

I am in the process to set up a 12 x 6 x 2.7 listening room

Is that feet or meters? My advice will be very different for each!

My plan is to hang some diffuser / abosrber panels to catter ceiling
reflection and get rid of both issues above.

You'll also need a fair amount of bass trapping if you hope to get any sort
of even low end response.

Let me know about feet or meters, and in the mean time have a look at my
Acoustics FAQ:

www.ethanwiner.com/acoustics.html

--Ethan

You really think his room may be two and a half feet high? Acoustics would
be the least of his problems.

d

Hello Ethan: dimension are in meter.

Thanks for looking into this a posting your link.
Why do you feel I need heavy trapping to get rid of sufficient low end
bass response?
Since I am dealing with a non-rectangular geometri it is hard for me to
predict modes frequency. I plan to make the longest wall shortr in
order to avoid multiple dimensions

Don is right :-)
I appreciate Don comment as well on my room setup

Thanks in advance!

On 6 Sep 2005 09:15:52 -0700, Andy Luotto wrote:

Hello Ethan: dimension are in meter.

Thanks for looking into this a posting your link.
Why do you feel I need heavy trapping to get rid of sufficient low end
bass response?
Since I am dealing with a non-rectangular geometri it is hard for me to
predict modes frequency. I plan to make the longest wall shortr in
order to avoid multiple dimensions

Don't do that. If you want to avoid standing waves, make the dimensions of
your room as unevan as possble. If you can get all the walls non-parallel,
that is even better. There are no magic dimensions; all that happens if you
change wall lengths is that you get a different set of frequencies with
problems. Far better to have a non-rectangular room and not have any modes
than a tidy room and knowing the exact frequencies at which is is bad.

Once you have a nice, irregular room free of standing waves, you can go
ahead and start tackling the reverberation time. I don't know what you
intend to do with the room, but there are plenty of books on acoustics out
there which wil guide you to a good choice of reverberation time (or rather
times, because it will change with freqeuncy). You can probably use movable
panels of various absorbers to fine tune different frequencies.

d

Hello Don,

Don Pearce wrote in
:
....
Once you have a nice, irregular room free of standing waves, you can
go ahead and start tackling the reverberation time. I don't know what
....

I'm a bit confused. AFAIK even a non rectangular room will suffer from
standing waves. Computing the exact resonant frequencies will be much more
difficult, if not even impossible. Also the resonances will have a lower Q,
so an irregular shape might be of help, but you won't get rid of the
standing waves.
With this respect I have even read of some designer who prefer to
have a rectangular shape because, even if the resonance problems are
bigger, they are easier to identify on paper, and so they also become
easier to fix.

Bye,

--
Denis Sbragion
InfoTecna
Tel: +39 0362 805396, Fax: +39 0362 805404
URL: http://www.infotecna.it

On Tue, 6 Sep 2005 16:47:07 +0000 (UTC), Denis Sbragion wrote:

Hello Don,

Don Pearce wrote in
:
...
Once you have a nice, irregular room free of standing waves, you can
go ahead and start tackling the reverberation time. I don't know what
...

I'm a bit confused. AFAIK even a non rectangular room will suffer from
standing waves. Computing the exact resonant frequencies will be much more
difficult, if not even impossible. Also the resonances will have a lower Q,
so an irregular shape might be of help, but you won't get rid of the
standing waves.
With this respect I have even read of some designer who prefer to
have a rectangular shape because, even if the resonance problems are
bigger, they are easier to identify on paper, and so they also become
easier to fix.

Bye,

There will still be standing waves, but they are hugely attenuated compared
to those created by parallel walls. Essentially the amplitude of the wave
depends on the area of wall producing it - if the walls are non-parallel,
that area is much reduced for each frequency.

The designer who prefers rectangular rooms because they are easier to
calculate is simply lazy. And the way you fix these resonances is to make
the walls diffuse, so who cares how well you can calculate the frequency?

d

"Denis Sbragion" wrote
Don Pearce wrote

...
Once you have a nice, irregular room free of standing waves, you can
go ahead and start tackling the reverberation time. I don't know what
...
I'm a bit confused. AFAIK even a non rectangular room will suffer from
standing waves. Computing the exact resonant frequencies will be much more
difficult, if not even impossible.
[...]

Please have a look at www.cara.de.
This prog may give you more info than you want;-)

Rudi Fischer
--
....and may good music always be with you

Hello Rudi

I purchased CARA few years ago and I am seldomly using it with
satisfaction.

What I do not like is the graphical entry: I would have appreciated the
program can get AutoCAD files - this the most commonly used format for
architecture and in fact I have the room design produced by AUtoCAD.

I asked CARA if there is any plan for making the program able to get
AutoCAD files but I was replied there is no plan for this

I find designing vault with the current CARA graphics is time consuming
so I gave up

Thanks for replying
P.S. I posted weeks ago about the opportunity to upgrade CARA from 2.1
to 2.2 without getting any reply fromt he group. Any hint from you,
which I suppose a user of 2.2?

Hello Don

thanks for your reply! I am always impressed by your competent
contribution to the audio related newsgroups!

BTW, I can try to build a non parlallel wall on the shortest side (see
my ASCII artwork below) to better cope with long wall resonant mode -
this should make them uneven and less strong. Being on the long side,
those mode should deal with the lowest frequency modes

Cheers
_________ _________
| | | \ |
| | =| \ |
|_________| |_ \_______|

On 7 Sep 2005 04:34:14 -0700, Andy Luotto wrote:

Hello Don

thanks for your reply! I am always impressed by your competent
contribution to the audio related newsgroups!


Thank you for that!

BTW, I can try to build a non parlallel wall on the shortest side (see
my ASCII artwork below) to better cope with long wall resonant mode -
this should make them uneven and less strong. Being on the long side,
those mode should deal with the lowest frequency modes

Cheers
_________ _________
| | | \ |
| | =| \ |
|_________| |_ \_______|

That will work. You don't need to modify the actual walls, of course. You
can use free-standing panels of plywood or MDF. They have the advantage
that you can move them out of the way when you don't need them. Treat one
side with some soft absorbent material and you can choose how lively your
room is.

d

Thanks Don: I then argue that vaults bring benefit since they make the
room dimensions VERY uneven, right?

Cheers

"Andy Luotto" wrote

Hello Andy

I purchased CARA few years ago and I am seldomly using it with
satisfaction.
What I do not like is the graphical entry:

Agreed, that's quiet a bit troublesome and time consuming.
But...

I would have appreciated the
program can get AutoCAD files - this the most commonly used format for
architecture and in fact I have the room design produced by AUtoCAD.
I asked CARA if there is any plan for making the program able to get
AutoCAD files but I was replied there is no plan for this

....CARA is definitly not pro, it's only a hifi-hobbyist-oriented-prog (with
pro-like results), so they might think (IMO correctly!) that there are only
very few owners using AutoCAD too.

I find designing vault with the current CARA graphics is time consuming
so I gave up.
P.S. I posted weeks ago about the opportunity to upgrade CARA from 2.1
to 2.2 without getting any reply fromt he group. Any hint from you,
which I suppose a user of 2.2?

Yes, I'm currently running 2.2 plus - it's (new-)function-list at
http://www.cara.de/ENU/cara-raumakustik-simulation.html

If your asking if 2.2 can do vaults by polygone- or Bezier-curves:

Sorry, no, only sloped ceilings, you still have to define separate
3D-objects with different *slopes* and *group* them appropriatly.
But in reality I got measured peaks/nulls that way by about +/-5cm,
so perhaps you might want to give it a new try - still way
better/cheaper than guessing - or waiting for v2.5

BTW: The auralization-part (Plus versions) demos changes in
roomsize, furniture or damping quite successfully (IME, used
headphone Beyerdynamics DT880).

Rudi Fischer
--
....and may good music always be with you

Hello Rudy

my opinion is that enabling an AutoCAD interface may at least imply for
them to pay royalties to Autodesk, which is something may increase the
street price - and the tool popularity

DIsagree that few audiophiles are using AutoCAD: I experienced serious
ones - i.e. people which care about room setup like you and me - very
often have AutoCAD file for their rooms

Kind Regards

Don,

You really think his room may be two and a half feet high?

Of course not, but since the word "vault" is in the subject it seemed
possible it's a knee wall that starts at that height. I've seen enough
misleading NG posts that it was worth at least asking. :-)

--Ethan

Andy,

Why do you feel I need heavy trapping to get rid of sufficient low end
bass response?

Because without bass trapping all small rooms have an unbelievably skewed
low end response. Here's a graph from an article I wrote for EQ magazine
that shows the response in a typical 16 by 10 by 8 foot room:

www.realtraps.com/art_response.gif

Since I am dealing with a non-rectangular geometri it is hard for me to
predict modes frequency.

In a room that's already built you don't really need to calculate modes. All
small rooms have problems at all low frequencies, so the best solution is
always broadband absorption that works to as low a frequency as possible.
However, since you have the opportunity to change the room dimensions you'll
do well to at least consider that.

In my FAQ is a sidebar that describes the ModeCalc program you can download.
If the ceiling is angled severely, ignore that dimension and just go for a
good ratio between the length and width. If you want to angle the walls to
get wider toward the rear, you can use the average width for calculations.
Either way, the room will still have modes that are just as significant as
if it were a plain rectangle. Angling walls does not reduce the effect of
modes. And whatever else you do, DO NOT cut across the corners to make them
angled. All that does is remove the single best place for bass traps.

--Ethan

On 7 Sep 2005 07:34:05 -0700, Andy Luotto wrote:

Thanks Don: I then argue that vaults bring benefit since they make the
room dimensions VERY uneven, right?

Cheers

Yes and no. They do create specific problems at the focal points of the
curves. It may be worth treating these points with an absorbent bar
stretching the length of the vault.

d

On Wed, 7 Sep 2005 13:52:53 -0400, "Ethan Winer" ethanw at ethanwiner
dot com wrote:

Andy,

Why do you feel I need heavy trapping to get rid of sufficient low end
bass response?

Because without bass trapping all small rooms have an unbelievably skewed
low end response.

A 12m x 6m room is "small"?

Hello Ethan,

"Ethan Winer" ethanw at ethanwiner dot com wrote in
:
....
In my FAQ is a sidebar that describes the ModeCalc program you can
download. If the ceiling is angled severely, ignore that dimension and
just go for a good ratio between the length and width. If you want to
angle the walls to get wider toward the rear, you can use the average
width for calculations. Either way, the room will still have modes
that are just as significant as if it were a plain rectangle. Angling
walls does not reduce the effect of modes. And whatever else you do,
DO NOT cut across the corners to make them angled. All that does is
remove the single best place for bass traps.

so do you confirm that having angled walls doesn't remove the modes? And
that using the average size gives a reasonable extimation of the modal
resonant frequencies?
I'm also interested into this because I have a room with a
rectangular shape and a sloped ceiling. I had the option to decide at least
the width of the room while building it, so I optimized it performing some
modal analysis using the average height of the room as one size. I haven't
been able to do any acoustical measure in the new room yet (still
unfinished), but knowing that the assumptions I made while optimizing it
are at least reasonable will make me sleep a bit better. )

Bye,

--
Denis Sbragion
InfoTecna
Tel: +39 0362 805396, Fax: +39 0362 805404
URL: http://www.infotecna.it

Hello Denis

Marco is speaking !! How are you?

Anyway Don asserts that sloped walls or ceiling does not remove the
mode but decrease the acoustic power of the modes, which is a very nice
feature overall.

I will go fo a non parallel wall in my room and maybe, depending on the
costs, slope it a bit.

Ciao

Rudi Fischer wrote:

"Denis Sbragion" wrote
Don Pearce wrote

...
Once you have a nice, irregular room free of standing waves, you can
go ahead and start tackling the reverberation time. I don't know what
...
I'm a bit confused. AFAIK even a non rectangular room will suffer from
standing waves. Computing the exact resonant frequencies will be much more
difficult, if not even impossible.
[...]

Please have a look at www.cara.de.
This prog may give you more info than you want;-)


I've used two versions of CARA. It's got lots of cool functions. But the
problem with it, for me, living in the States, is its limited selection of
speaker models (most of which are European). Not to mention the inability
to render all measurements and display in feet/inches as well as metric.
It's a rather Euro-centric piece of software ;




--

-S

dizzy,

A 12m x 6m room is "small"?

Compared to an auditorium it is. I use "small" to mean a room the size
you'll find in most homes. In rooms like that you're never more than 10 feet
or so from a boundary, so the reflections are strong and the modes are
fairly far apart.

--Ethan

Denis,

so do you confirm that having angled walls doesn't remove the modes?

Yes.

that using the average size gives a reasonable extimation of the modal
resonant frequencies?

I don't know if it gives a "reasonable estimation" but it's about the only
thing you can do. If the height varies by a large amount you could also
ignore it and just optimize the length versus width. The ceiling is often
the limiting factor anyway, especially with basement studios where the
length and width are large but the ceiling is too low to fit any of the
ratios commonly accepted as being "good." So all you can do is add plenty of
bass trapping, which you'd need anyway.

--Ethan

Hello Ethan,

"Ethan Winer" ethanw at ethanwiner dot com wrote in
:

I don't know if it gives a "reasonable estimation" but it's about the
only thing you can do. If the height varies by a large amount you
could also ignore it and just optimize the length versus width. The
ceiling is often the limiting factor anyway, especially with basement
studios where the length and width are large but the ceiling is too
low to fit any of the ratios commonly accepted as being "good." So all
you can do is add plenty of bass trapping, which you'd need anyway.

many thanks. I don't want to stole the thunder to Andy (who lives just
about 10 Km away from me , BTW the room is 7.1 x 3.85 m. The ceiling goes
from 1.8 m to more than 4 m (about 4.3, not sure now), so the height varies
quite a lot. Nevertheless, if average is the only available option, let's
go for the average and cross our fingers... Fortunately I will have the
option to add everything I want afterward (it's a dedicated room), so I
hope to be able to fix any unexpected result afterward.

Bye and thanks again,

--
Denis Sbragion
InfoTecna
Tel: +39 0362 805396, Fax: +39 0362 805404
URL: http://www.infotecna.it

"Steven Sullivan" wrote

I've used two versions of CARA. It's got lots of cool functions. But the
problem with it, for me, living in the States, is its limited selection of
speaker models (most of which are European).

Did you look at
http://www.cara.de/ENU/USERBOX/boxen.php
where you can download user-created speaker-models?
[...]

Rudi Fischer
--
....and may good music always be with you

Rudi Fischer wrote:

"Steven Sullivan" wrote

I've used two versions of CARA. It's got lots of cool functions. But the
problem with it, for me, living in the States, is its limited selection of
speaker models (most of which are European).

Did you look at
http://www.cara.de/ENU/USERBOX/boxen.php
where you can download user-created speaker-models?
[...]

Yes, I check there regularly. The selection is still rather
limited. Nothing by NHT or Velodyne, for example -- the
two brands I currently use.

I understand that reluctance of some manufacturers to
supply the sort of detailed technical info CARA requests, makes
it difficult to make a comprehensive database. One solution
would be to comprehensively search bench-test results of
audio magazines dating back to a decade or more, but this
too seems impracticle.


--

-S