Irrational ratios/enclosure dimensions

[Andy G]

Next thing to do...

There are an infinite no. of irrational numbers between 1 and 2, have fun searching ;-)

Another method of designing is to use 3 numbers that are relative primes. Again, can be fun !!

Go for it !!

 

[simon5]

Using Andy Graddon method with prime numbers, I managed to get a perfect result ie no highlighted red results.

307 mm
479 mm
631 mm

Vikash, as a suggestion, you could add a logarithmic highlighter instead of a linear one.

I mean 1.00 kHz and 1.02 kHz are not higlighted but if you have 24 Hz and 34 Hz it will be highlighted. IMHO 1.00 kHz and 1.02 kHz are worse I think? Maybe you could make the highlighting threshold customizable too!!!

Nice calculator, to be able to customize everything is perfect.

 

[planet10]

307 mm
479 mm
631 mm

0.641:1:1.317

dave

 

[johngalt47]

Doesn't all this presuppose that you can cut wood to that accuracy? (assuming you use wood)

I can see where it might work with a CNC machine....

 

[Vikash]

The idea is to play with the dimensions to make sure there aren't any fundamental flaws. Cutting to mm perfection is certainly not realistic. The ratios are added just to suggest some basic ideas. The intention was to work with the suggested numbers by rounding to your requirements and having a quick check that you're not making any major mistakes from the offset.

As Ron has said, it more complicated then this. But I think it is a good starting point.

 

[Ron E]

Here's a little pascal program I wrote back in ~1992 and never finished - as you can see from the descriptively named commented out procedure calls at the end. I wrote this for room dimensions, but it could be modified for box dimensions.

In my old fortran days I had a program that calculated all modes, sorted them and did a bunch of statistics and rated the rooms based on mode spacing. I only wrote teh good rooms to a file and I came up with a list of room sizes that worked best for room acoustics. This type of analysis is often interesting to young engineers who are trained that everything is sort of deterministic in nature.

You could likewise generate effective ratios for box design. You should remember that foam or fiberfill are very nearly perfect absorbers of more than 1-2kHz or so, so those frequencies wouldn't matter much.

Have fun.

----------------------------------------------------
program modes;
var length, width, height : real;

procedure getroomsize;
begin
writeln('Enter the room dimensions in inches');
writeln;
write('Length of room ?');
readln (length);
write('Width of room ?');
readln (width);
write('Height of room ?');
readln (height);
end;

procedure modestofile;
type freqarray = array[0..10,0..10,0..10] of real;
filenametype = string[255];
var i, j, k, lmax, wmax, hmax : integer;
f : freqarray;
f1 : text;
filename : filenametype;
begin
filename := 'output.dat';
assign(f1, filename);
rewrite(f1);
lmax := trunc(300*length/6786);
if (lmax>10)then lmax:=10;
wmax := trunc(300*width/6786);
if(wmax>10)then wmax:=10;
hmax := trunc(300*height/6786);
if(hmax>10)then hmax:=10;
for i := 0 to lmax do
for j := 0 to wmax do
for k := 0 to hmax do
begin
f[i,j,k] := 6786*sqrt((i*i/(length*length))+(j*j/(width*width))+(k*k/(height*height)));
if ((f[i,j,k]<300.0) and ((i+j+k)>0))then
begin
writeln(f1, i:3, j:3, k:3, f[i,j,k]:8:2);
end;
end;
close(f1);
end;

begin

getroomsize;
modestofile;
{plotmodes;}
(*sortmodes;*)
(*printaxial;*)
end.

 

[planet10]

Here's a little pascal program I wrote back in ~1992

I had one i wrote in System/360 assembler (late 70s), and later one i wrote in Forth... not quite as elaborate as yours thou...

dave