golden ratio. I dont get it - Page 5 - diyAudio
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Old 5th December 2012, 01:47 PM   #41
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transcendental would be nice. But then a TARDIS would be nicer.
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Old 5th December 2012, 01:53 PM   #42
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Yes, like C E G sharp. But only if you believe in that new fangled equal temperment thing.

David
ACK! You're right. It would be an augmented chord.
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Old 5th December 2012, 03:04 PM   #43
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yeah. I dont much like sus7 chords either.
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Old 5th December 2012, 04:59 PM   #44
Jmmlc is offline Jmmlc  France
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Hello,

I used to work on Rayleigh's formula. My pruprose was to have the smallest interval between 2 consecutive resonances.

This study produced the attached graph.

The optimal shapes points on that garph form a red line.

Good shapes that spread optimally the resonances frequencies seem to be :

1 : 1.3 : 1.5
1 : 1.5 : 2.0
1 : 1.9 : 2.5
1 : 2.3 : 3.0
1 : 2.5 : 3.5
1 : 3.0 : 4.0

Best regards from Paris, France

Jean-Michel Le Cléac'h
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Old 5th December 2012, 07:27 PM   #45
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But it looks like that approach compares the first dimension to the second and the second to the third, but not the first to the third. As an example 1:1.5:2 would have lots of overlapping modes from the 1 and 2 dimensions.

Isn't the cube root of 2 approach guaranteed to be the most uniform distribution?

(Not that I still think any of this matters when damping is applied.)

David
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Old 5th December 2012, 08:19 PM   #46
tvrgeek is offline tvrgeek  United States
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GL shows up all over as was noted; for some reason it is a pleasing proportion. I have no doubt the ancients had just as good an eye for portion as we do. A concert hall or cathedral is not a speaker box. If you want to read about cathedral acoustics, search on Harris. Yea, over time the did know what they were doing.

My mid cabinets are highly stuffed and if I was worried about overlapping standing waves, I would just angle a wall. I don't find it to be necessary.
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Old 5th December 2012, 08:28 PM   #47
flg is offline flg  United States
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Are we trying to remember Fibinacci? I think it was called a golden mean??? The series of numbers, ie; 2,3,5 (1:1.5:2.5) and each succsesive number is the sum of the previous 2? Where none of these numbers have multiples in common with the others or their multiples???
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Old 5th December 2012, 08:48 PM   #48
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Quote:
Originally Posted by Jmmlc View Post
Hello,

I used to work on Rayleigh's formula. My pruprose was to have the smallest interval between 2 consecutive resonances.

This study produced the attached graph.

The optimal shapes points on that garph form a red line.

Good shapes that spread optimally the resonances frequencies seem to be :

1 : 1.3 : 1.5
1 : 1.5 : 2.0
1 : 1.9 : 2.5
1 : 2.3 : 3.0
1 : 2.5 : 3.5
1 : 3.0 : 4.0

Best regards from Paris, France

Jean-Michel Le Cléac'h
In 1:X:Y, is 1 assumed to be the depth of the cabinet?
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Old 5th December 2012, 08:54 PM   #49
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Quote:
Originally Posted by speakerdoctor View Post
In 1:X:Y, is 1 assumed to be the depth of the cabinet?
Does it matter. As long as the driver fits i'll happily use any face epending on the context of the installation.

dave
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Old 5th December 2012, 08:56 PM   #50
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re. Fibinacci

The concept is to get the most even spacing between the modes (fundamental and harmonics) of the standing waves of the 3 dimensions of a speaker cabinet (or listening room). Since each dimension has multiple modes at integral multiples (1/2 wavelength frequency, 2 x that, 3 times that) the modes actually get closer together as you go up in frequency (at least on a log graph). As such you can only worry about the spacing for the first mode or two. Since even thin wall lining will easily kill upper modes I think worrying about the fundamental and second mode are the only ones that could possibly be justified.

As such, looking at the longest dimension, we should strive to have the 2nd and third modes equally spaced between the long dimension first mode and its second harmonic. The only approach that guarantees that is the cube root of 2 approach. It places the three dimension's fundamental modes 1/3 Octave apart in the first Octave.

And I still don't think it matters if the cabinet is well damped!

David S.

Last edited by speaker dave; 5th December 2012 at 08:58 PM.
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