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17th September 2003, 09:47 AM  #1 
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Golden ratios and standing waves
Based on the consensus that: enclosures dimensions should optimally be derived using golden ratios to reduce standing wave effects, I have a question...
My enclosure volume is approx. 98l which I'm building into 244x418x962mm enclosure. Using W=v/f, I caluclate standing waves at: 1393 Hz 813 Hz 353 Hz If a golden ratio is used to derive box size: 280x467x747mm, then standing waves exist at: 1214 Hz 728 Hz 455 Hz The offending frequencies are very close and I see no reason to closely adhere to the golden ratios? ( or have I missed something ) I was going to asymmetrically fill three walls with fiberglass to compensate. Any comments? 
17th September 2003, 10:15 AM  #2 
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Sorry to be a cynic, but what consensus? I find the Golden Ratio/Fibonacci etc interesting as an example of coincidental math, but some of the effects ascribed to it by Cardas and others just strike me as voodoo for impressionable audioholics.
Still, it can't hurt. Cheers Steve
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17th September 2003, 10:32 AM  #3 
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This may be useful
http://www.acoustica.org.uk
Click on 'speaker positioning' and locate the Excel Spreadsheet, it may help analyse the issues. Andy. 
17th September 2003, 11:11 AM  #4  
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X^2=X+1. 1/X=X1 Mmmm....
My opinion is that the golden ratio is of better use for the external dimensions of the box so that it looks "right".
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17th September 2003, 11:33 AM  #5 
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Just had a look at that spreadsheet. Looks like what I caluclated are actually second order harmonics, the fundamental freq's being half my calculations. How does each harmonic affect the sound  to what degree in amplitude?
At the moment, I think that all rectangular enclosures suffer more or less equally (irrespective of whether the dimensions are golden ratiofied) and that the important thing is to make sure each dimension is (assuming all parallel walls) different  to avoid adding to another standing wave. Agree? Edit: By looking at the harmonics (occuring at each doubling of the fundamental) I've just realised that you need to avoid enclosure dimensions that are multiples of others, as the harmonics will reinforce each other. I think I may have just justified the reasoning for golden ratios 
17th September 2003, 12:18 PM  #6 
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Excuse my ignorance, I'm still in the early stages of learning this stuff, but I've been wondering for a while; Doesn't using non parallel sides in an enclosure pretty much deal completely with this problem? I'm sure it's just not that simple, or else you would see no rectangular boxes and yet they abound.
Chris 
17th September 2003, 12:32 PM  #7  
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17th September 2003, 12:34 PM  #8  
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Steve, you've apparently had my house bugged. Quote:
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17th September 2003, 01:06 PM  #9  
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mcp, here's are the standing wave modes for my current design. I see issues with (for example) the 3rd harmonic (height) and the fundamental (width) reinforcing each other. Are these the problems you were seeing?
It seems clear to me now that using the golden ratios in my design would have resulted in much less overlap of standing waves harmonics. I'm convined of this reasoning now, though I have no idea how much affect this has Quote:


17th September 2003, 02:11 PM  #10  
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