38 x 61.5 x 99.5 is golden ratio. If 18 mm ply, gross volume would be 191 litres,
If we start with 110 litre add 5 litre for bracing and back of driver then:
115 litre = 115,000 cm^3. Take the cube root = 48.6
48.6 x 1.618 = 78.7
48.6 / 1.618 = 30
So interior dimensions of 30 x 48.6 x 78.7 cm
dave
If we start with 110 litre add 5 litre for bracing and back of driver then:
115 litre = 115,000 cm^3. Take the cube root = 48.6
48.6 x 1.618 = 78.7
48.6 / 1.618 = 30
So interior dimensions of 30 x 48.6 x 78.7 cm
dave
Thanks, Dave. I did not start this thread, but find the info very useful. That method is so simple I wish I had thought about it.
Deon
I agree, it's for looks only, just another myth. I use Square root of 2 to propertion my bass reflex boxes. Also remember when you calculate a boxes volume it is the ideal volume and therefor everything that goes inside the box takes away from this ideal volume and you have to compensate for this by making the box larger, my free software does this for you.
Sample - The Book Worm
I've wondered about this, too. If you're just modeling a flat baffle for diffraction purposes (say for an OB), seems like the "golden ratio" doesn't produce an optimal response in sim. Might be fine to start there though.
Wasn't it for concert halls? Unlike Victorian structures, such as the Albert Hall.
I always thought it was observed in ancient egyptian design, adopted by the greeks, and used visually to proportion windows, paintings etc. Ive never tested if it really works in acoustics. My favourite adaptation of GL is to halve the longest length, calculating for twice the volume. Its a nice way to get a more cube-like shape. Of course standing waves would be more bunched up, but i never heard a problem. GL is better than guesswork, or breaking the 'rules' i.e. W equally a third H for example.
Another skeptic, here.
As Mark said, the theory is, the standing wave harmonics will be evenly distributed, but this merely means they will retain the maximum possible energy. I think a more sophisticated cabinet design would cause the standing waves to cancel each other.
I think there's nothing special about 1.6180339..... I think any irrational number will do.
I also think if you were to try to design a box where the standing waves reinforced each other, you would find it quite difficult, and due to braces and battens, etc., you would not end up with 1' x 2' x 4'.
As Mark said, the theory is, the standing wave harmonics will be evenly distributed, but this merely means they will retain the maximum possible energy. I think a more sophisticated cabinet design would cause the standing waves to cancel each other.
I think there's nothing special about 1.6180339..... I think any irrational number will do.
I also think if you were to try to design a box where the standing waves reinforced each other, you would find it quite difficult, and due to braces and battens, etc., you would not end up with 1' x 2' x 4'.
Just don't use it twice or you end up with the long dimension twice the smallest one.
I don't hold fast to the golden ratio, but do use irrational numbers to determine aspect ratios of rectangular boes.
dave
Here is a neat calculator. Just give a desired mid-value and you'll get the smaller and bigger numbers
Golden Ratio Calculator
Golden Ratio Calculator
GR is so much more...
...than just visually appealing. It's defined as
GR:=[1 +/- (5)^-3]/2
Our bodies are formed using this ratio, as well as most everything in nature. Strictly speaking, it is the one "perfect ratio". The Fibanicci series becomes this at the limit as x--->0 (IIRC).
P10's statement regarding the use of irrational numbers as ratios is for all practical purposes suitable.
...than just visually appealing. It's defined as
GR:=[1 +/- (5)^-3]/2
Our bodies are formed using this ratio, as well as most everything in nature. Strictly speaking, it is the one "perfect ratio". The Fibanicci series becomes this at the limit as x--->0 (IIRC).
P10's statement regarding the use of irrational numbers as ratios is for all practical purposes suitable.
Royal Albert Hall is a large ellipse, so I don't know how you would apply it. A lot of Architects seem to lean on the Golden ratio but I don't know that there is any magic to it. I certainly don't know of anything in Architectural Acoustics that relates to it.
Again, with enclosures, it only makes sense to worry about the distribution of resonances if you plan to do nothing about them. Since internal stuffing can do a good job of damping I wouldn't worry about exact dimension ratios.
David S.
In any BR where one is only putting damping on the walls, you will never have sufficient damping to kill a standing wave so it does not hurt to cover all the bases.
dave
It doesn't hurt in a "belt and suspenders" sort of way (braces for the Brits). Still, the only time I've seen standing waves that defied treatment was with very tall towers, i.e. with extreme aspect ratios. With cabinets close to the usual 2 cubes high ratios I find good absorptive material (FG and Rock Wool) do a pretty good job, even as linings.
David S.
David S.
Theres no advantage in using irrational numbers. You can use normal numbers like 3,5 and 7.
In the sense that your belt doesn't have enuff holes in it to tighten them up. I have always used the rule of thimb that to completely kill a standing wave you need to pass it thru at least a 1/4 wl of damping.
And if you have a tower with an extreme aspect ratio you need to treat it as an ML-TL not a BR, and you usually want to take advantage of the 1/4 wave resonance to get more/lower bass extension.
dave
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