# 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


Here is a link to another room mode calculator that htnut12 provided... 

Room Mode Calculator


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## azjimmy

Hey Sonnie,
Quick question.
Is there a general rule of thumb for vaulted ceilings to be used with this calculator? 
TIA
Jim


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## Sonnie

Hmmm... I don't think I know how to calculate it, but surely someone does. Maybe hardman will know and chime in.


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## Guest

Azjimmy raises a good question but unfortunately the formula I used to make the room mode calculator only works on a rectangle room with a flat ceiling. I am sure there is a formula that will address sloped walls, but I don’t know what it is or have access to this information.

Sorry - Chris


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## Guest

yo, yo, yo. I beleive that you need to average the max/min. I could be wrong, but it is an approach that I read for non rectangular roomages.

Lates

T

:wave:


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## Guest

The spreadsheet, good as it is, as supplied only calculates axial modes, which admittedly are the most powerful but tangential modes i.e. those that strike four surfaces as opposed to the two in axial modes, only lag around 3dB below but at very different frequencies due to the varying path lengths.

When I was teaching acoustics in a music college I used to impress on students that calculating modes was interesting in theory, but not much use in practical. There is no short cut to identifying "boom" frequencies but by lenghty actual measurement with a frequency generator/ or test tone CD and a sound level meter. When you have identified the one or sometimes two fundamentals which are causing problems and treated them by trapping you will be on the way to hearing your equipment/system as the manufacturer intended.

I also used to stress that the sound system is the equipment and the room.


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## Guest

room modes in non-rectangular rooms can be tricky. We use a min, max and average analysis when designing spaces that have on set of surfaces that are not parallel. (sloped ceiling, angled side walls). Once you get more complicated than that, then you have to go into a complex simulation....When considering modal distribution we believe that all modes must be considered. The bonello criteria is based on Axial mode distribution but we look at Oblique and Tangential modes as well, as they do help "fill in" the areas above the fundamental for each dimension in small rooms. Hope this makes sense....:nerd:


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## htnut12

I snagged a room mode calculator off a link on the IB Cult which gives a nice graph like this. You can place two speakers and the seat in the room and it calculates the response at the seat. Really nice.


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## frank308

Could you provide the link?

Thanks

Frank


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## htnut12

Room Mode Calculator


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## Ayreonaut

I have tried quite a few of these. 
The one I like best is by Eric Desart. 
His website is gone, but you can find the file at

http://forum.studiotips.com/large_files/RoomModeCalculator.zip


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## Vader

All of these tools just accentuate how much I have to learn - they are all pretty much greek to me. Is there any online "crash course" out there that will allow me to at least make use of the basic functionality? Or would that be like asking for a crash course in graduate quantum mechanics for someone who is just starting to understand classical mechanics....?


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## htnut12

The link I posted gives you an Excel Spreadsheet that runs some Visual Basic Code automatically. First you input the dimensions of your room, length, width and height. You can input your listening position by calculating the position of your head away from the front, left wall and floor. Then you put in the location of your subwoofer, up to two subwoofers. Same way distance from front, left wall and floor. By moving the location of the sub or subs you can see the peaks and valleys that are due to the standing waves generated by reflections in the room. You can change the reflectivity of the surfaces too. So a hard smooth wall of drywall or plaster would be very reflective. A carpeted floor would be less so.


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## Vader

Thanks, Jerry!


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## Vader

When trying to use the room dimensions mode calculator in this thread (post #1), I can get it to come up ok (I have the macro security set to 'medium, so I can use macros fine), and I can enter my room dimentions with no problem. But when I hit the 'Plot' button, I get the following error:



> Run Time Error '1004'
> Application-defined or object-defined error


and hitting the 'Debug' button yields



> Selection.Sort Key1:=Range("b31"), Order1:=xlAscending, Header:=xlGuess, _
> OrderCustom:=1, MatchCase:=False, Orientation:=xlTopToBottom, _
> DataOption1:=xlSortNormal


At first, I thought I merely forgot to install VB with Excel, but that is not the case either. Does this mean anything to anybody? I am using Excel 2000 (I downloaded the calculator version "for all versions _older than_ Excel 2003"), and WindowsXP Home. Thanx!


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## Gizmo

Room calculations, tried some but when i input the height etc etc and it made a calculation, i see 2 rows and then copie them for txt file but its all weird. I included a txt file. Maybe a stupid question but can there be a page made for dummies like the BFD?


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## planet10

Sonnie;2011.xls file: [URL="http://www.hometheatershack.com/roomcalculator.xls" said:


> Room Dimensions Mode Calculator[/URL] (Excel 2003 only)
> 
> .xls file: Room Dimensions Mode Calculator (for older Excel versions)


Neither of those will generate a plot in Excel 2004 giving an error on this line



> Selection.Sort Key1:=Range("b31"), Order1:=xlAscending, Header:=xlGuess, _
> OrderCustom:=1, MatchCase:=False, Orientation:=xlTopToBottom, _
> DataOption1:=xlSortNormal


I did write a rectangular mode calculator in 360 assembler back in the mid 70s... maybe i'll have a look at fixing this ... (but excel is such a kludge...)

dave


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## Guest

Sorry to hear some of you are having difficulties in getting the Excel doc to work correctly. Not sure what is causing the issues (works fine for me…), but Ethan has a similar program on his site that runs without needing Excel. I suggest you all try his application. www.realtraps.com/modecalc.htm 

Also, please note this approach (my Excel doc) to room mode discovery is very basic at best. Its intended purpose was to help assist in determining the best room dimensions for new construction.


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## planet10

hardman said:


> I suggest you all try his application. www.realtraps.com/modecalc.htm


Windows only... so no dice.

dave


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## Seb

I agree not to get too hung up on room modes. Many rooms designed from scratch won't be rectangular. Plus, the rooms we are talking about will usually have lots of absorption. Thirdly, For an existing room, or a room once it is built, the room needs to be fine-tuned anyway, so the modes must be verified by testing.

The theory is nice to have but it also assumes that the room boundaries are hard and rigid. At very low frequencies this is probably not true for non-masonry walls (ie plasterboard or sheetrock or whatever u guys call it stateside). So, again, that means testing.

When I am designing a room I make sure that the room dimensions are not integer multiples of each other, then I check the room mode calcs but I don't get obssessive and check 200 different combinations (ok maybe 10 or 20), and then I allow for tuned absorption treatment.


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## Guest

I hate to say this but I am in the same boat as Vader. I at one time in my career worked with climate control systems balancing out rooms that were held to tight tolerances. I see many things that might be similar but also I see things that would oh so complicate a simple spread sheet such as this. How would a ceiling fan with five rotating hard surfaced blades effect the accoustics of a room? Does moving the furniture in a room have equal ramifications? Does this spread sheet tell where the ideal speaker placement would be? What does it do?


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## brucek

> Does this spread sheet tell where the ideal speaker placement would be? What does it do?


The various calculators available are simply a starting point to show the ideal modes, given three room dimensions. After that it's all about measuring and trial and error...

brucek


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## Doug Plumb

Calculating room modes is a waste of effort because your room is never quite square and never quite the exact measurement that you input. In addition to this the actual response varies with a measurement mic location. Higher order modes are strongly affected by room shape.

The results of these excercises have no practical value. Measurement is the only option when assessing room behaviour. Properly averaged measurements show dominant mode behaviour very clearly.

They can be useful for designing a room but favourable dimension ratios have already been found. The best rule is to build as big as possible, for mid/HF reasons as well as bass response.


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## Blaser

Doug Plumb said:


> Calculating room modes is a waste of effort because your room is never quite square and never quite the exact measurement that you input. In addition to this the actual response varies with a measurement mic location. Higher order modes are strongly affected by room shape.
> 
> The results of these excercises have no practical value. Measurement is the only option when assessing room behaviour. Properly averaged measurements show dominant mode behaviour very clearly.


Doug, I have to disagree with you....sorry:nono:
Waste of effort??? No, it is quite the contrary. Normally, what is in my opinion a correct and, what is an effort and time saving procedure is to simulate room response at LP first with one of the great programs like Room Respose Calculator by Yavuz Aksan. Then tweeking or slight subs position change is made through measurements.
When you're having small subs it is OK not to give such a theoretical response any importance..but when you're having 200 Lb+ subs, that's another story.
In my case, my room is almost a perfect rectangle, but if it weren't, it would be harder but still not a waist of effort though as one can know at least some of the modes.

Look at my room theoretical subs response graph vs practical measurements....Can you see any similaritires?


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## Ayreonaut

blaser said:


> Can you see any similaritires?


Yup. :clap: Cool! :T


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## Doug Plumb

It depends on what you mean by similarities - you always have to verify a simulation with a measurement. Those two are many dB off - the dip is predicted but not exactly in frequency.


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## brucek

blaser says:


> Look at my room theoretical subs response graph vs practical measurements....Can you see any similaritires?


Yeah, interesting. The peaks and dips appear to line up, and if the vertical scale was the same they'd be quite close. It's nice that the measurement verified the simulation. 

There are always lots of influences in a room that will change the actual meaurement, but if you've got a rectangular room, there's a good chance the resonance calculators will give some decent indications where the modes are and whether they'll line up or not. Certainly useful in finding the optimum room shape for home theatres or listening rooms if you happen to be building one.

brucek


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## Blaser

You're correct Doug. A similation will not tell you everything very accurately, but it gives only an idea. BTW, I am sure I could get closer to practical measurements by increasing the no. of reflection (as my room has brick walls) that I have quite ignored.

Here is another SIMULATION which made me decide not to chose the nearfield arrangement in the same room because I like a steep house curve.
I know there will be a dip around 30 Hz, but measurements might show that dip propably more or less enphasised with a propable slight change in frequency. But the concept is still the same...There will be a Dip with this configuration at a frequency low enough to be unpractical for a house curve without overstressing amps/drivers...

This is what I beleive to be the real intention of such room calculator programs.


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## Blaser

brucek said:


> Certainly useful in finding the optimum room shape for home theatres or listening rooms if you happen to be building one.
> brucek


DEFINITELY! I wish I knew this before constructing my House:sarcastic:


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## Eric Desart

franman said:


> The bonello criteria is based on Axial mode distribution but we look at Oblique and Tangential modes as well, as they do help "fill in" the areas above the fundamental for each dimension in small rooms. Hope this makes sense....:nerd:


Just a small comment, since I accidentally stumbled upon this post by Googling.
My idea is not to discuss this but to correct something.
The Bonello criteria are based on all modes not on the Axials alone. Hence taking the tangential and oblique modes into account is integrated in Bonello's approach/calculation method.

Just info.

Best regards
Eric


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## Blaser

Welcome to the shack Eric,

Hope to see you intervene more !!


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## kentowl

Thanks to both Doug Plumb and Ahmed for educational discussion of room response analysis. My intro to room acoustics predates personal computers, but we learned some basic lessons that the programs confirm. One was that the structure of rooms can be altered to good effect, using common decorating elements. These need to be considered in room analysis.

My HT room started as almost a perfect 22' square, with a 50% high ceiling. We pulled a large portion of the screen/front center wall in 2 feet with a granite fireplace surround and overmantle (holding the widescreen), the back wall in 1' with a built-in bookshelf (diffuser) where the wall wasn't open to the rest of the house, and dropped/vaulted the ceiling to 8.6' average. That got rid of the worst geometric issues, and "by ear" the results are more than decent already. I've made provisions for a second SW, and look forward to doing REW checks when equipment permits.


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## bclare

Hi 

Does anyone have a link (or can post a link) to the room response calculator program that works. 

The present link only contains a sing .frd file and not the actual calculator


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## laser188139

Brad, a google search for "room response calculator yavuz aksan" finds a copy of Yavuz Aksan's Room Response Calculator v0.6d at a Russian university here.


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## bclare

Thanks for that. Tried google, but obviously didn't use all the terms above.


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