Room Mode calculator - HTML only version

[Bob]

Eric:

Also add a title section were you retake all relevant data, which is than copied with it.
Measures room,
Floorspace
Total boundary surface
Volume.

I like that.

[Bob]

Dan:

Bob the new parts added with the colors does not work on all browsers.  I have only seen it work in IE on XP so far.  It does not work on firefox on xp, or any of the mac browsers that I checked before I left to work.  I would test it on  Firefox and then IE if works on both of those chances are it works on most browsers and OS's.  If want to use a mac for testing I could set up something to allow you to access one remotely.

Jeepers. Multi browser support?
I might try firefox.
It should work on any version of IE on any Windows OS, especially Windows 2000 and Windows XP.

The red lines on the piano should work on the following browsers:
Linux: Browsers with Gecko-Engine (Mozilla, Netscape 6+, Galeon), Konqueror, Netscape 4, Opera 5, 6 and 7.
Windows: Gecko-Browsers, IE 4, 5 and 6, Netscape 4, Opera 5, 6 and 7.
Mac: Safari, Gecko-Browsers, Opera, Netscape 4, partially IE.

[Dan Nelson]

The red piano lines work fine it is the other stuff that doesn't show up see the screen shot below the parts i circled only show up in IE.

Firefox = Mozilla
Konqueror might still equal Safari
In the old days IE broke and fixed things from one minor version to the next, so till this day I still don't trust it.

Dan.

[Dan Nelson]

Dan:
And Jeff said that they could be more powerful or less or equal or whatever.  Leo Beranek has an example where the tangentals and obliques are stronger than the axials.

Bob you are the master of tracking information,  I have talked to ethan a few times about there are rooms out there where tangental and obliques caused problems and at some point he will run into them. I have run into myself  and i'm sure Jeff has as well, but I no idea if I have any record of the rooms since they where must likely  done by hand on paper.  I will look for Beraneks example tonight

Dan:

My position is that it doesn't matter who's right. What is irrelevent is which is the stronger mode group: axial, tangential, oblique.
Because for example if you believe Everest and have a strong axial and a weak tangential that are within 1hz of each other, they're going to add to make something stronger than the axial alone (at some spots in the room?). So the fact that the tangental exists is still important, even if at half the strength. So it's important to know the frequency of all modes. A post-build measured resulting mode's strength will be determined by other things.

You are correct, I think both and Jeff are saying the same but they emphasize different parts of the concept.  Now if you can figure out a way to display that in an intutive manner.  Give each mode type a  different height value and stack them in bandwidth groupings?


Dan

[Bob]

FYI

This is the list of enhancements I'm considering at the moment

a) count the axial, tangental, oblique. (i.e. how many are tangental, how many are oblique)
b) references section (piano, Eric's room sizes post, StudioTips and RO thread, MHoA and it's references, especially Lord Rahley's equasion, HAA)
c) Bonello chart and Bonello weighted chart a la Eric and Everest (axial vs sqrt(2) * tangental vs sqrt(2) * oblique).
d) Walker 5%?, Gilbert, Bob flags (interpretation of Eric's "Bad is poorly spread, isolated, or stacked and isolated" )
e) PowerResponseCurve divide sound pressure by sqrt(2) (Morse & Bolt twice the power axial vs tantental)
f) a room ratio calc (even for tall narrow rooms)
g) rotating the piano 90 degrees so that it could be used underneith an ETF5 plot (i.e. to match modes to measured)
h) an automatic room sizing algorithm that'll try a range of room dimensions and chug for a day to find the best 3. To answer the question: what if I made this wall a foot or two or more smaller.
i) axial only chart in addition to the combined chart -- for HAA style and Gilbert calc
j) textarea of data in axial/tangental/oblique chart, I can make it a tab separated list, so it should paste into excel just fine. Or a comma separated list which can be imported into excel just fine
l) Total boundary surface, wall surface, floorspace/ceiling surface (metric and imperial)
m) Volume  (metric and imperial)
n) ITU Control Room RT60
o) Harmon's Axial placement chart with a chat about modes are only problems if they are energized and this is where to place speakers, and a similar chat about damping the modes (absorbtion).
p) large room warning (lots of modes)

What I'm kind of stuck with at the moment is (d).

GREEN -- no problem
YELLOW -- minor issue, try absorbtion
RED -- bad. Move the speakers to not energize this.

For 'Bob's Flags' I'm thinking of
a) looping through the sorted frequencies looking for groups. A group is defined as a bandwidth (start frequency to end frequency range) such that there is no frequency within 5% of that frequency under the start frequency and no frequency within 5% of that frequency over the end frequency.
b) If that group is larger than 5% wide (i.e. start frequency is less than end frequency *.95) then it's not a problem -- GREEN.
c) If that group is narrow, less than 1% wide, then it's -- RED
d) otherwise (1% to 5% wide) then it's -- YELLOW

I was considering a weighting system where I'd add to a counter for each group, and the final value of the counter indicated the color
a) -0.5 for each mode in the group
b) +2 for each coincidenct frequency in the group (same frequency more than once)
c) +1 if the isloation lower is wider than 10% (i.e. the next mode down from this group is more than 10% away). Similar for upper.
And then if the resulting number is > 3 then it's RED, otherwise YELLOW.

[Brian Dayton]

hey bob,

you have the warning colors for close modes

close modes are good, yes?  as in when modal density gets high at, say, 250hz, and they are all over each other, this is good?

[Bob]

Hello:

I've made some improvements to my room modes calculator. Still more to do (e.g. References, Bonello, copy textarea, floor area alone).
Well, I hope they are improvements. Please let me know. I kind of made up the weighting to match what I think people have said.

http://www.bobgolds.com/Mode/RoomModes.htm

If you want to give it a try, I recommend trying: 10 x 10 x 10 ft, and 10 x 10 x 9 ft.

Improvements:
a) 5% groups are shown
b) uses .GIFs for colour, so it might work in FireFox
c) Warns on large rooms
d) weighting system for modes
e) a Computed Information section

Computed Information:
Room Dimensions: Length=12.46 ft, Width=11.42 ft, Height=7.9 ft
Room Ratio: 1 : 1.44 : 1.57
RT60 (ITU Control Room Recommended): 0.17 ms
Absorbtion to achieve RT60: 323 sabins
Volume: 1124 ft^3
Surface Area Ceiling+Floor: 284 ft^2
Surface Area Walls: 376 ft^2
Surface Area Total: 660 ft^2
Lowest Modal Frequency (Axial): 45.3 hz
Count: Axials=16, Tangentials=84, Obliques=144
Max Frequency for computation (cutoff): 300

[Eric.Desart]

Waaaauuuuuw,

Congratulations.

[avare]

Sorry, no negatives, it just looks great!

Admiringly:
Andre

[Bob]

Thanks guys.

I was in my shower thinking about this line
"RT60 (ITU Control Room Recommended): 0.17 ms "
and it struck me that I'm out by a thousand again....
I'll have to fix that.

[Howler]

Killer. It works om Mac 9.2.1 Netscape 6

[Bob]

[humor, but true]
Who made this a sticky? Do you have any idea how long it took me to find this thread?  :bang
[end humor]

http://www.bobgolds.com/Mode/RoomModes.htm

I made some more improvements:
a) inches calculator
b) shows % of difference in frequency, wavelength
c) R. Walker BBC 1996 test
d) Nearest Known Ratio (based on Eric's ACCEPTABLE ROOM RATIOS page)
e) more Surface Area computations

I think the wavelength bit will be helpful in positioning speakers and things.

More to come...



BTW, is Walker's 1996 BBC rule: 1.1w/h <= l/h <= 4.5w/h - 4
the same as EBU R22-1998 below ( from Eric's ACCEPTABLE ROOM RATIOS ) ?

[Eric.Desart]

Dan did it, until it's referred in the FAQ or something (no long term).

For the formulas, I should have to check to be sure, but you can do it yourself.
In the RPG papers about the room sizer and room optimizer those formulas are clear mentioned.
If you download them, you also have clear references at the end of the docs.

Walker is the base for EBU and IEC (+ UK standards).
I think only IEC deviates a minor bit (but still based on Walker).

[David French]

cool!  :8

Works in Fireforx 1.0.2 except that the compute buttons appear between and behind the column headings and the first axial mode line.  They also cannot be depressed.

[Bob]

Eric:

I couldn't initially find the reference in the RPG PDFs at the website, nor in the papers on Optimizer/Sizer in the back of Master Handbook Of Acoustics.

I did find this reference
 [16] Walker, R. “Optimum Dimension Ratios For Small Rooms”. 100th AES Convention.
 Preprint 4191 (Copenhagen, Denmark, 5/1996).
in http://www.harman.com/wp/pdf/HarmanWhit ... ingLab.pdf
which refers to the same forumla on page 4.

The same formula again is here, with a few more details:
http://www.acoustics.salford.ac.uk/acou ... izing2.htm

Eventually I did find it referenced here http://www.rpginc.com/news/library/roomsizer.pdf , which is probably where you were thinking of. It has this interesting quote "Walker states that the aim of the regulations appears to be to avoid the worse cases, rather than to provide proscriptive optimum ratios."

It's available here for $20 http://www.aes.org/publications/preprin ... search.cfm (look for preprint 4191)

But it didn't really answer my question: are the graph and the formula the same.

So I went at it from the other side looking for EBU R22-1998
I found this "R22-1998 Listening conditions for the assessment of sound programme material " but the PDF isn't available for that.
Then I found this http://www.ebu.ch/CMSimages/en/tec_text ... 6-4659.pdf which is also called "Listening conditions for the assessment of sound programme material" but it's R22-1999 (ends in a 9).

But I haven't found anything yet that has both the graph and the formula on it.

I might just have to work out the graph myself, based on the formula.

[Eric.Desart]

What graph are you missing?

This EBU graph is something I made. That does not exist.
This is calculated and drawn in Excel for me.
I've been busy quiet a while to find how to handle this graph.
I've searched for a solution how to visualize those EBU/Walker formulas.
I never saw something like it.

In my Excel I can redraw it by setting an arbitrary safety to substitute the 5% rule.

 So if you mean THAT graph that's my design.

And the one in the center isn't easy to find.  I redraw that once. That's from Bolt and Beranek.
I believe Jeff once entered a ref to his side where a copy of the original article resided.

Yes that was the RPG doc I meant.
I know and have the Walker papers.

[Bob]

Eric:

So if you mean THAT graph that's my design

I was beginning to come to that conclusion.
The Bolt portion I recognized. I've seen that kidney shaped thing in several places.
The rest looked like lines in Excel -- and you're the King of Excel.

And yes, I was looking for those green lines in a paper by Walker.

Thank you for answering my question - the graph and the formula are the same.

[Bob]

Hello

A few more improvements to  http://www.bobgolds.com/Mode/RoomModes.htm

Still more to do though...

1) A bonello graph (bottom right)
2) % side wall coverage calc
3) More Walker BBC lines

Bonello Graph looks like this:


% side wall coverage calc
The idea here is that if 1 sabin is 1 ft^2 (absorbtion coefficient 1.0), then if the entire front wall is covered in 703 and the floor has carpet, what percentage of the remaining three walls should have connected (not checkerboard) treatment?
So the line that is shown is:
 (sabins - front wall - carpet) / Left+Right+Rear wall: 31 %

More Walker BBC lines
R. Walker BBC 1996:
   1.1w / h < l / h < 4.5w / (h - 4): Pass
   l < 3h & w < 3h: Pass
   no integer multiple within 5%: Pass

I have a question about Walker. I've seen these two formulas on the www
   1.1w / h < l / h < 4.5w / (h - 4)
   1.1w / h < l / h < (4.5w / h) - 4
Which one is right?

[J.F.Oros]

I have a question about Walker. I've seen these two formulas on the www
   1.1w / h < l / h < 4.5w / (h - 4)
   1.1w / h < l / h < (4.5w / h) - 4
Which one is right?

Hi Bob,

I don't know exactly which one is the right one, but it seems that the first doesn't have the same "measurement units" on all the terms (the term "h-4" is correct only if "4" means "4 distance units").


Excelent work Bob, by the way !
Flaviu.

[Eric.Desart]

Hello

I have a question about Walker. I've seen these two formulas on the www
   1.1w / h < l / h < 4.5w / (h - 4)
   1.1w / h < l / h < (4.5w / h) - 4
Which one is right?

Bob,

Sorry I missed this post for some reason.

The second one is right.
1.1w / h < l / h < (4.5w / h) - 4