The Golden Ratio of 1.618

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Do the internal dimensions of 13.335cm, 18.429cm, and 29.818cm follow the Golden Ratio of 1.618? One website calculator says yes, another says no.

13.335cm is my smallest allowable dimension so I started from that number.

I am seeking to construct a dimensionally non-resonant sealed box for a driver.

Thanks.
 
frugal-phile™
Joined 2001
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13.335 x phi = 21.576

21.576 x phi = 34.910

A box a hair over 10 litres.

What do you need an on-line calculator for? One of the ones you used is out-to-lunch.

Robert's algorithm for working from a required volume is bang on

Using the golden ratio will not create a non-resonant sealed box. The use of irrational numbers (phi or not) to determine a boxes dimensions just helps keep them from piling on top of one another (be careful with the squareroot of 2)

dave
 
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A non-resonant box is the sphere. B&W Nautilus makes use of long distances behind the driver. For the bass driver they serve as a closed transmission line or a kind of or maybe labyrinth/aperiodic/infinite baffle.

You could install it in a pipe, just make sure the length is one quarter of the lowest reproduced wavelength and fill it with fiberglass or stone wool or a mix of all known wadding.

After all with midranges, your aim is not the LF alignment and as long as you are in the flat area of the response, the enclosure is demanded to do just one thing. Actually it is required not to do anything and specifically not to send reflected waves through the cone.

I remember a discussion between me and one of the reputable members here, we agreed that a good choice for midrange is well stuffed chamber with open back. Slight dipole effect (eliminates the environment due to the side null) and nothing is returned through the cone due to the non-interacting character of the enclosure.
A note of caution is to stuff the chamber well, because otherwise it will act as an U-frame and those always exhibit the so called U-H-frame peak which is not manageable in a bandpass such as the midrange, only low pass or in exotic examples highpass if it occurs low enough which in turn is governed by dimensions.

Best regards!
 
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frugal-phile™
Joined 2001
Paid Member
Thanx for the article.

The trap to avoid when using root-2 is that root-2 x root-2 is a very undesirable ratio.

Toole's work shows that there are no magix ratios for rooms... partly due to the fact that windows, doors, and the construction of the walls, more often than not give resonances that do not correspond to the physical dimension.

A huge step in solving room issues is to cant one of the surfaces (ie vaulted ceiling). If the cant can be in 2 directions you are even further ahead.

This also applies to speaker boxes, but at higher frequencies and the consideration that it is easier to achive a "stiff room" so the actual dimensions have greater coorespondence to functional dimensions.

dave
 
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Joined 2008
There is no such thing as a non-resonant box.

The only thing achieved by using different dimensions for height, length and width is to spread the resonances so they coincidence less. Which dimensions that actually work depends, and should be calculated for each case. And one should look at both axial, tangential and oblique resonant modes.
 
I like golden ratio encolsures for strength. It makes for a very stiff box without adding bracing/panels. It also helps that no single dimension is too small/large, but with all the great "tower" designs out there, I'm not sure golden ratio has any advantage... internal dampening may be more important.
 
The golden ration seems to be pleasing to the eye. Other than that, not much use. It is 3-5-7 actually. The best way to distribute reflections is a non regular shape. I find proper stuffing works just fine and I spend my extra time worrying about the crossover.

The best acoustic room I ever had was in a mobile home. The ceiling was vaulted (double wide) and the walls were just about transparent to bass, so no bass cancellations. I loved it. I doubt the neighborhood did.
 
It is 3-5-7 actually.

Hi,

No its not, actually .....

It is (1+ squareroot5)/2 = 1.62, 1/1.62 = 0.62,
1/0.62 = 1.62, commonly rounded to 0.6:1:1.6.
which equals 3:5:8 as round number estimates.
5/8's:1:8/5's is the same as 0.6:1:1.6.

Triangular rooms or boxes don't stop resonances they move
them to where the symmetry of the triangle creates a box.

For width and depth its a fair way to dimension a box but
for height lots of other things come into it for convenience.

rgds, sreten.
 
The golden ration seems to be pleasing to the eye. Other than that, not much use. It is 3-5-7 actually. The best way to distribute reflections is a non regular shape. I find proper stuffing works just fine and I spend my extra time worrying about the crossover.

The best acoustic room I ever had was in a mobile home. The ceiling was vaulted (double wide) and the walls were just about transparent to bass, so no bass cancellations. I loved it. I doubt the neighborhood did.

I agree with you and 1.618 is actually visually ideal for doorframes and picture frames. In my books I state that the crossover is probably the most important part of the system. Incidentally i use 1.4142 in my ducted phase inverter designs as well as dimensioning my sound room. It's amazing when the room and speakers work together.

Mac

Build your own loudspeakers - The Lost Art of Loudspeaker Design - The Book Worm
 
frugal-phile™
Joined 2001
Paid Member
If you use phi to generate internal dimensions, the outside ends up not being golden ratio because of the wood thickness... and in my CGRs the vent slot.

CGR-Mar-Ken12-comp.jpg


Me, i just avoid crossovers for the most part, avoiding the evil they bring.

dave
 
Hi,

No its not, actually .....

It is (1+ squareroot5)/2 = 1.62, 1/1.62 = 0.62,
1/0.62 = 1.62, commonly rounded to 0.6:1:1.6.
which equals 3:5:8 as round number estimates.
5/8's:1:8/5's is the same as 0.6:1:1.6.

Triangular rooms or boxes don't stop resonances they move
them to where the symmetry of the triangle creates a box.

For width and depth its a fair way to dimension a box but
for height lots of other things come into it for convenience.

rgds, sreten.

Quite correct. I guess I was instructed wrong 50 or so years ago.
 
Dave,
Do you also dislike any passive network? BSC, any bit of shaping? I guess I have not figured out what is so wrong with passive networks. Incorrectly designed ones, yes. Crossovers placed within our most sensitive hearing bands, yes. I don't know what is basically evil about them.
 
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