# Sticky  Room Mode Calculator and Converter



## Sonnie

*hardman* has been kind enough to furnish us with a couple of nice downloadable progams that might come in handy all along. Thank you hardman!

The first program is a Room Dimensions Mode Calculator. This is a Microsoft Excel Worksheet that allows the user to enter their room dimensions and then see how close/far apart the modes are for their space (program works for 0 to 300 Hz). To use the worksheet you will have to enable macros. Just enter your room dimensions (red) and then click the clear button and last the plot button.

.xls file: Room Dimensions Mode Calculator (Excel 2003 only)

.xls file: Room Dimensions Mode Calculator (for older Excel versions)

Remember: you must enable macros when it loads the program.


The second program is a very complete converter tool. This is not your ordinary converter... it has 22 different conversion categories and converts about anything that could possibly be converted.

.zip file with .exe program: Converter


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## Ethan Winer

Sonnie said:


> *hardman* has been kind enough to furnish us with a couple of nice downloadable progams that might come in handy all along. Thank you hardman!


Agreed.

And for anyone who doesn't have Excel but uses Windows, here's a Mode Calculator program I wrote that has a few unique features:

www.realtraps.com/modecalc.htm

--Ethan


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## ludwignew

How should I use this if my room has asymetric dimensions?


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## willy-be

ludwignew said:


> How should I use this if my room has asymetric dimensions?


The only program I know of that will acoustically model asymmetric rooms is CARA 2.2 

Know in advance it's an extremely user hostile program with no support from the maker.
http://www.cara.de/ENU/index.php?load=cara-powerpack.html


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## savior sound

I am converting an already finished out basement that measures 26' x 12.5' x 7.8' ceiling. The 12.5' width and the ceiling cannot be changed but I did plan on creating a 4' deep closet to house the AVR & equipment and store movies/games etc. So the 26' length will change to something like 22' (or whatever would work best). I plugged in the room deminsions (see attached .xls) Now what do I do? Sorry for my ignorance!

Thanks

Steve

EDIT: sorry I couldn't attach file - too big.


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## thewire

savior sound said:


> I am converting an already finished out basement that measures 26' x 12.5' x 7.8' ceiling. The 12.5' width and the ceiling cannot be changed but I did plan on creating a 4' deep closet to house the AVR & equipment and store movies/games etc. So the 26' length will change to something like 22' (or whatever would work best). I plugged in the room deminsions (see attached .xls) Now what do I do? Sorry for my ignorance!
> 
> Thanks
> 
> Steve
> 
> EDIT: sorry I couldn't attach file - too big.


Start to calculate sabins needed to tame room resonances.


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## savior sound

And how do I do that?


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## thewire

Here is a link to Sabine's Reverberation Formula with a calculator. If you are going to design a listening room, which I think you may be, this will help determine how live or dead the room sounds. There are different ways to go about it, and not all rooms are alike. Simply tell it what you intend to have on your walls, floor, and ceiling, and it gives you an aprox idea. Listening to the room will also help, and measuring the actual changes would be best, but this does give an idea what you will have to deal with. There are other calculators which allow you to also manually enter the absorption coefficients, but this may be easier.

http://www.sengpielaudio.com/calculator-RT60.htm


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## savior sound

OK, I'm starting to understand - thanks to the help section of your app Ethan. So to give you a little background, I am constructing a HT (music listening) room in my existing basement. As I stated earlier the constants are the 12'6" width and the 7' 9 1/4" high ceiling. The variable is the length which is 26' now but I plan to construct a wall approximately 4' from the existing back wall for a closet. Before I construct this wall, I am trying to figure out where would be most beneficial place (acoustically) to put it. Can someone make a suggestion as to what I should do? Bascially 12'6"x7'9.25"x? what (26' or less) would be the best room demension for movie/music listening. I understand that I will still have some treatments (bass traps, absorption, diffussion, etc.) to help but I want the best possible starting point. Does that make sense? Can anyone help me?

Thanks in advance,

Steve

EDIT: I also plugged in my projected room demensions (22' as the length) in the Sabine's Reverberation Formula calculator and got 0.45 @ 125 Hz, 0.71 @ 250 Hz, 0.81 @500 Hz, 0.68 @ 1 KHz, 0.45 @ 2 KHz and 0.41 @ 4 KHz. What does this mean?


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## thewire

savior sound said:


> OK, I'm starting to understand - thanks to the help section of your app Ethan. So to give you a little background, I am constructing a HT (music listening) room in my existing basement. As I stated earlier the constants are the 12'6" width and the 7' 9 1/4" high ceiling. The variable is the length which is 26' now but I plan to construct a wall approximately 4' from the existing back wall for a closet. Before I construct this wall, I am trying to figure out where would be most beneficial place (acoustically) to put it. Can someone make a suggestion as to what I should do? Bascially 12'6"x7'9.25"x? what (26' or less) would be the best room demension for movie/music listening. I understand that I will still have some treatments (bass traps, absorption, diffussion, etc.) to help but I want the best possible starting point. Does that make sense? Can anyone help me?
> 
> Thanks in advance,
> 
> Steve
> 
> EDIT: I also plugged in my projected room demensions (22' as the length) in the Sabine's Reverberation Formula calculator and got 0.45 @ 125 Hz, 0.71 @ 250 Hz, 0.81 @500 Hz, 0.68 @ 1 KHz, 0.45 @ 2 KHz and 0.41 @ 4 KHz. What does this mean?


I think you will want to maximize the space while keeping things symetrical, room for seating and treatments. I stuck my wall where it was symetrical to sit between the support beams without obstructing the screen and speakers for example. I made my wall splayed (not straight) by a foot or so. I checked with the room mode caluclator and did minor changes to the inches. I started with a 14 foot wall and then moved to 13.5 foot one. I stuck it right before a null in my room that I could hear and so that the right corner sounded the same. I walked from the right corner over to the left and stopped when it sounded different. These nulls are in the same place now that I have walls.


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## savior sound

I still don't understand what the RT60 results mean.


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## bpape

RT60 should be taken with a grain of salt and used as a comparative reference. RT60 is really more for larger spaces. Basically what it's telling you is that you have .45 seconds from the time that a 125hz tone stops until it decays by 60 db. .71 seconds at 250hz, etc.


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## Nic_swe

yho, just a wee question regarding the excel file :mooooh: , I'm assuming that the height/width/length is in the unit feet rather than meter correct? Does the calculation work as a ratio, therefore allowing both units or do I need to convert my measurements from meters to feet?

cheers!:nerd:


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## bpape

It's is feet. It needs to be converted. The issue is that if you have meters, the portion of the formula relating to the speed of sound would also need to change to metric parameters.

Bryan


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## sandbag

My attempt to use this calculator with Excel for Mac produced garbaggio. Since my room is the size it is, and according to Floyd Toole, knowing the modes is not that valuable in a small room multiple speaker environment, is there any reason to calculate the modes? I plan on treating the room until it sounds right to me, anyway.


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## bpape

The one thing modal calculations are useful for up front (if the room is existing) is to know WHERE physically in the room they'll be so you can set up seating properly. It's also helpful to be able to play with speaker positioning and sub positioning to potentially introduce opposing characteristics to help smooth the response.

Bryan


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## Dennis Erskine

Caveats on room mode calculators ...
1. They are not accurate. They assume a rectangular room with perfect walls that reflect 100% of the energy that strikes them;
2. They cannot express the magnitude of the mode (you may be down in the weeds trying to fix a problem that won't exist once the room is built);
3. In smaller rooms, 6" can take you from "good" to "not good". I don't think you're going to sit that still;
4. At best they can perhaps tell you what you might run into so you have plan A, B, and C;
5. In rooms with soffits, indents, bump outs (any departure from rectangular), you'll find your (calculated, and real)) modal response will vary in different areas of the room.


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## Macattack

So Dennis, you seem to be implying a build it and then fix it approach based on what it sounds like. Like the OP, I am almost at the same stage in planning as he is with a similar shaped room. About 12' wide, 24' long and 7.5' high. As I play with the room mode calculators, I have gotten down in the weeds and don't even have the room yet! Meaning, I see how a few inches on these dimensions can change the mode and in one calculator, take me from shaded (good) to non-shaded (bad) ratios. I know I do not want 12' and 24'... reducing either by 6" would be good. 

While the scientist in me would dearly love to have THE plan with calculations, room modes, reflection points, etc all mapped out and 'fixed' before hand, my plan is to decide on the 'oddest' ratios build it with isolation techniques to keep the sound in then use a locate and treat strategy to optimize the sound and staging. Locate the speakers and my ears then treat for primary reflections and add base traps as funds allow. The only thing I am still considering is to make one or both sidewall(s) move from 12' to 11.5 ' over the 20 to 24' length. Not sure that is worth the extra carpentry however...
Craig


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## bpape

My point was not so much to tell you what TO DO, but more what NOT to do. Certainly the calculators are not 100% accurate unless you're in a perfectly rectangular, 6 foot thick concrete bunker. That said, they can show you some things to avoid.


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## Macattack

So I am getting ready to launch and still wondering about making the sidewalls (long walls) non- parallel. Is it worth moving them 6" over 24'?


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## bpape

I wouldn't. If you do splay them, you'd want 1" per foot per wall so you'd be 48" narrower at one end than the other. That assumes you want them non-parallel enough to be effective down into the bass also.


Bryan


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## Macattack

bpape said:


> I wouldn't. If you do splay them, you'd want 1" per foot per wall so you'd be 48" narrower at one end than the other. That assumes you want them non-parallel enough to be effective down into the bass also. Bryan


Thank you, I can't afford to lose that much real estate. I am worried now the room may feel small with my infinities and especially small if I land some Betas .

Treatment will be inevitable. Stay tuned!


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## NBPk402

bpape said:


> RT60 should be taken with a grain of salt and used as a comparative reference. RT60 is really more for larger spaces. Basically what it's telling you is that you have .45 seconds from the time that a 125hz tone stops until it decays by 60 db. .71 seconds at 250hz, etc.


So what kind of number should you shoot for with a HT? I ran the calculator on my room and I got 1.58 @125hz, 3.23 @250hz, 3.94 @500hz, 4.58 @1000hz, 3.79 @2000hz, and 3.5 @4000hz (it might vary a bit on my dimensions as we still have to finish up the ceiling and 2 walls) with only gypsum board, and carpet with pad selected.


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## bpape

It's based on the volume of the room. Generally for smaller spaces, we look at what it's doing in the first 300ms and in general like it to be down about 40db in that timeframe.


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