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Author Topic: Room ratio X15  (Read 5207 times)

janek

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Room ratio X15
« on: March 16, 2009, 04:47:40 pm »

Hey Hallo,

Newbie question: i'm building a small control room.
After x-tensive research i settled with one off the Louden room modes ; X15.
Meaning Max height in my case is 215 cm, width 258 cm, length 322,5
cm. Yeah, i know it's small, but hey, i'm just a small guy, and maybe,just maybe my daughters rabbit will enter during a mix session, but that 'll be all. If the door is open of course.
But seriously, is it so that by choosing these room modes you will NOT be having all sorts of peaks and dips in the spectrum, and you'll probably only will need a "taste tailored" absorption/diffusion of the achieved room?
I'd really like your professional opinion on this case.

best regards, the midget.
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Sigert

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Re: Room ratio X15
« Reply #1 on: March 16, 2009, 09:53:05 pm »

janek wrote on Mon, 16 March 2009 21:47

...is it so that by choosing these room modes you will NOT be having all sorts of peaks and dips in the spectrum,...


No, modal nodes and peaks will still be present. The only thing room ratio theory tries to accomplish is to determine room dimensions in which these modes are spread in such a way that their negative effect is mittigated. Though helpfull and interesting to look into, the concept is no wonder cure and all theories disagree on the 'correct' approach. Even the most fundamental things are often disagreed on, like what it means for modes to be "spread out equally".
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janek

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Re: Room ratio X15
« Reply #2 on: March 17, 2009, 06:15:12 am »


Howdie Sigert, thanx for your reply.
Let me get this straight; the chanches are better in getting a more even spread of freq. rsponse across a room if you build it according to room ratio's by Louden /seppmeier(!?)

Now as i am already building this room, perhaps any suggestions?
I think i just build the shell and start on from that.
By the way i was not correct; it is X05: Height:1 X1.2 Y1.5
according to Louden but his associate claims: Height:1 X1.14 Y 1.39
I start big and shrink if i have problems?
Should i bother in getting an angle in the ceiling ?

Any suggestions would be wildly appreciated.

best regards, Help out the dwrf!
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Sigert

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Re: Room ratio X15
« Reply #3 on: March 17, 2009, 07:58:20 am »

Quote:

the chanches are better in getting a more even spread of freq. rsponse across a room if you build it according to room ratio's

Yes, but only in the frequency region controlled by mode behaviour. Which is supposedly anything below 250Hz, or atleast not much higher.
Also, because theory supposes infinitely rigid and massive walls, and real life DIY walls/floors/ceilings arn't, don't expect wonders from building with ratio's. Assuming you're building your room inside an existing room: Is the outer shell made of stone, or is it gypsum aswell?

Are you floating your floor? Don't forget to fill up the cavities with absorptive material.
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janek

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Re: Room ratio X15
« Reply #4 on: March 17, 2009, 11:12:09 am »

Thanx for your reply, The outer shell is solid concrete,
floor, walls and ceiling.
If you look at the picture provided with former post; floor detail, you'd see: Yes,flooting floor, double decoupled, vilt and cell-isolation decoupling rulers, stuffed inbetween with homatherm flex.

Again, any considerations with respect to angels of ceiling ?
I'm not expecting any miracles, just want to exclude major low frequency problems on initial build, since they use up so much roomspace if you'd have to build bass traps, and the room is small to begin with, but tha's just a limitation i'll have to cope with.
Please, all the input is much appreciated; i have a degree in audio engineering, not in acoustics.
best regards, janek
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Sigert

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Re: Room ratio X15
« Reply #5 on: March 17, 2009, 11:32:00 am »

Depending on how rigid and massive your inner shell boundaries are, your outer shell dimensions (being concrete) might at some point start controlling your low frequency modal behaviour. This is nothing to worry about. The thought just grabbed me and got me asking some more info out of personal interest.
Could you tell us what your inner shell walls are made of?
Could you tell us the outer shell dimensions?

What are you trying to achieve with angling your ceiling? Is it flutter you're worried about? Or something else?
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Ethan Winer

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Re: Room ratio X15
« Reply #6 on: March 17, 2009, 03:13:43 pm »

janek wrote on Tue, 17 March 2009 06:15

Should i bother in getting an angle in the ceiling ?


I don't think so. All that will do is make your small room even smaller. You can get the same benefit with absorption on the ceiling.

--Ethan

janek

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Re: Room ratio X15
« Reply #7 on: March 17, 2009, 04:21:32 pm »

Hi there, thanx for your comment.
I think i was not clear enough or misunderstood the outer shell concept.
I'm just building a small controll room in an existing L shaped room.
The control room will sit on a floating decoupled floor and will be made of drywall 2 layers inside ,woodstander,homatherm 6 cm and drywall 2 layers outside.
Take a look at my "drawing"
All i just want to know is if i'm on the right track here,
i mean if the basic structure or it's dimensions are terribly off,
it will take such a load of work to repair the error, but besides that , i'm limited to the outer room dimensions, so..

Thanks, for your conciderations.
best regards, janek
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Sigert

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Re: Room ratio X15
« Reply #8 on: March 17, 2009, 06:51:19 pm »

You're actually bang on track to make the most out of your resources Janek. Like Ethan said, angling a ceiling will cost you precious space. And it's nothing you can't fix with basic absorptive measure, which you'll probably be doing anyway I presume.

The reason I asked about your wall construction details is because I had a mad idea floating through the backwaters of my mind. From what I see on your drawing, there's still some space between your inner and outer shell. If that's the case, maybe you could do half of your basstrapping in the outer shell corners. Again, it's a wild idea, but if it is thought to be viable, it could save you some space inside your inner shell.
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jimmyjazz

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Re: Room ratio X15
« Reply #9 on: March 18, 2009, 08:01:15 pm »

Food for thought that won't really help Janek . . . while "ideal" (or at least recommended) room ratios are independent of room size, it's also true that bigger is in general better.  One reason is because a larger room of a given proportionality will experience response "lumpiness" lower in the spectrum than a smaller room will; i.e., the response will be "smooth" in a bigger percentage of the audio spectrum.  But I have also read research on room design (Trevor Cox, perhaps?) that suggests the most ideal ratios vary with room volume.  I need to dig that paper up . . .
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Steve Hudson

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Re: Room ratio X15
« Reply #10 on: March 19, 2009, 11:50:21 am »

jimmyjazz wrote on Wed, 18 March 2009 19:01

Food for thought that won't really help Janek . . . while "ideal" (or at least recommended) room ratios are independent of room size, it's also true that bigger is in general better.  One reason is because a larger room of a given proportionality will experience response "lumpiness" lower in the spectrum than a smaller room will; i.e., the response will be "smooth" in a bigger percentage of the audio spectrum.  But I have also read research on room design (Trevor Cox, perhaps?) that suggests the most ideal ratios vary with room volume.  I need to dig that paper up . . .


I just read a similar study last week which provided different ratios for three different room volumes.
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jimmyjazz

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Re: Room ratio X15
« Reply #11 on: March 19, 2009, 05:29:49 pm »

That was probably the same study.  I'm pretty sure Trevor Cox was involved.  I can't find my copy, though.
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Steve Hudson

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Re: Room ratio X15
« Reply #12 on: March 19, 2009, 05:51:24 pm »

Yup, it was one of Trevor Cox's papers. There's a link to three room ratio tables for a small room, medium room and large room. It was by luck that our control room is almost exactly 100 cubic meters, the reference volume for a medium room in this paper.

http://www.acoustics.salford.ac.uk/acoustics_info/room_sizin g/?content=best

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janek

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Re: Room ratio X15
« Reply #13 on: March 19, 2009, 05:59:09 pm »

Hi there,
thanx to all you people for replying.
Bit by bit it settles in.
I've also read a study done at the university of Salford wich claims that certain room ratios ONLY apply at a certain volume,
therefore even if you'd take all considerations at hand you'll
probably never nail down axactly what's going to happen.
For instance if you've calculated that at 3 spaced freq. a null or peak will occur, this could get frustrated by the fact that cause you havent fairly examined the wall behind wich will re-emit caused due tot different building materials.
And i can think of a lot more scenarios.
Actually cause now i'm building a little home studio al-of-a-sudden this became important, a sort of fixation that it has to be good.
To be frank, the few studios i've worked in the last 12 year wich really had a good controll room are 2 out of twelve max; so.
Although it would be nice to have a neat little room wich has good specs. i'm used to sort of go inbetween; after a few times in a room wheater it's good or really bad, you know how good or bad it is, atleast that's my experience.
thanx for tuning in,
cheers; the midget.
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Sigert

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Re: Room ratio X15
« Reply #14 on: March 20, 2009, 02:58:02 am »

Hey Janek,

the fact that you're aware of the ratio theory will save you from the really bad scenarios. If you do your interior acoustics right, you'll have yourself a room which is far from bad, and probably even near good.

Feed us more pictures.  Cool


Sigert
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franman

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Re: Room ratio X15
« Reply #15 on: March 20, 2009, 05:40:37 pm »

This is an important point to make on this forum. The reveared "golden" ratios and magical proportions DO NOT work at all rooms sizes. We run independant modal simulations on every set of dimensions we look at. I don't even pay that much attention to the proportions these days, as the 'design' usually dictates the proportions. Of course I'm not going to do 1:2:2.. but my point is, that you HAVE TO run the calculations to sort out the modes and see how you're sitting with regards to Bonello.. Then you need to look at the less signficant (tangential and oblique) modes which are not considered in Bonello and use some experience to determine if the working set of dimensions (and their associated proportions) work well...

1: 1.67: 2.67 isn't enough... It depends on the the dimensions for all the reasons that JimmyJazz lists... good one JJ

Steve Hudson wrote on Thu, 19 March 2009 11:50

jimmyjazz wrote on Wed, 18 March 2009 19:01

Food for thought that won't really help Janek . . . while "ideal" (or at least recommended) room ratios are independent of room size, it's also true that bigger is in general better.  One reason is because a larger room of a given proportionality will experience response "lumpiness" lower in the spectrum than a smaller room will; i.e., the response will be "smooth" in a bigger percentage of the audio spectrum.  But I have also read research on room design (Trevor Cox, perhaps?) that suggests the most ideal ratios vary with room volume.  I need to dig that paper up . . .


I just read a similar study last week which provided different ratios for three different room volumes.

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jimmyjazz

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Re: Room ratio X15
« Reply #16 on: March 20, 2009, 08:12:16 pm »

fran, is Bonello your de facto standard?  Do you use any other "goodness" estimators for a given response?
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Thomas Jouanjean

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Re: Room ratio X15
« Reply #17 on: March 21, 2009, 03:53:50 am »

Same same here... with the type of rooms we build, while I keep the basic ratio theory in mind (no squares or multiples etc) I must say that the geometry of all the rooms I work on are complex and that we work on the modal response in different ways. It's a lot more about how and where we want the energy to spread and how it decays (% on 1st reflections, % on 2nd reflections for ex)

Of course YMMV Smile

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Thomas Jouanjean
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franman

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Re: Room ratio X15
« Reply #18 on: March 22, 2009, 12:20:39 am »

Bonello is a standard, but we look at the distribution of axial, tangential and oblique for the rectangular dimensions, as well as deviations and density graphs that are proprietary. There is some very easy to use software from RPG (Room Sizer, Room Optimizer) that are also quite helpful once you spend some time with them. I've had amazingly accurate results from existing rooms plugged in Optimizer...

Trouble with most of these techniques is they don't allow for absorption beyond the possibility of inputting Absorption Coefficients for overall surfaces..

Of course, as Thomas points out with complex geometry it becomes a whole new ball game and experience has to rule. This is one of the main reasons we preach about rectangular rooms for DIY projects. It keeps the simulations manageable and at least you have a reasonable idea of what to expect.
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Bruno Gouveia

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Re: Room ratio X15
« Reply #19 on: March 22, 2009, 12:48:59 am »


According to the guys at RPG,  1:2,19:3 is one of the best for an optimized low frequency response, which gives a room looking like this, for 125m

franman

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Re: Room ratio X15
« Reply #20 on: March 22, 2009, 03:55:06 pm »

Bruno Gouveia wrote on Sun, 22 March 2009 00:48


According to the guys at RPG,  1:2,19:3 is one of the best for an optimized low frequency response, which gives a room looking like this, for 125m
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jimmyjazz

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Re: Room ratio X15
« Reply #21 on: March 22, 2009, 04:45:27 pm »

I think that layout would make a nice control room.
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Steve Hudson

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Re: Room ratio X15
« Reply #22 on: March 22, 2009, 07:40:27 pm »

jimmyjazz wrote on Sun, 22 March 2009 15:45

I think that layout would make a nice control room.


[never mind]
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Bruno Gouveia

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Re: Room ratio X15
« Reply #23 on: March 23, 2009, 06:49:06 pm »

http://www.aes.org/e-lib/browse.cfm?elib=13011

Authors:   Cox, Trevor J.; D'Antonio, Peter; Avis, Mark R.

I've the pdf of the article, if anyone wants it I don't mind to forward.

http://damping.tumblr.com/post/51371077/according-to-an-aes- article-of-some-important

franman

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Re: Room ratio X15
« Reply #24 on: March 25, 2009, 10:24:42 pm »

I believe you Bruno.. It's just interesting that this isn't the proportions they use for their test room at the factory... anyway... looks like strange proportions architecturally, to me... nuf said.. Cool
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jimmyjazz

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Re: Room ratio X15
« Reply #25 on: March 27, 2009, 06:31:15 pm »

The ceiling height is low, to be sure, but does the footprint bother you?
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franman

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Re: Room ratio X15
« Reply #26 on: April 02, 2009, 10:12:59 am »

No Jimmy, it's not the footprint, it's the ratio and the way it feels architecturally. I think it would feel like a room where the ceiling is too low.. just not good design mojo.. that's all.

FM
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jimmyjazz

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Re: Room ratio X15
« Reply #27 on: April 03, 2009, 01:12:19 pm »

I routinely mix in a room with a 9 foot ceiling and very good proportions.  It hasn't bothered me in the least.  I guess it's all about where you're coming from!
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franman

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Re: Room ratio X15
« Reply #28 on: April 06, 2009, 11:42:04 am »

nd we routinely design mix rooms with 9' or lower ceilings (have to in NY a lot)... but we still try to have proportions that work acoustically and architecturally... At the end of the day, this room (from this thread) probably isn't that big of a deal (or a problem)... nuf said??

FM
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