Golden ratios and standing waves - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 17th September 2003, 10:47 AM   #1
Vikash is offline Vikash  United Kingdom
diyAudio Moderator Emeritus
 
Vikash's Avatar
 
Join Date: May 2003
Location: UK
Default 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?
Attached Images
File Type: gif standing-waves.gif (7.9 KB, 755 views)
  Reply With Quote
Old 17th September 2003, 11:15 AM   #2
diyAudio Member
 
Join Date: Sep 2002
Location: Australia
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
  Reply With Quote
Old 17th September 2003, 11:32 AM   #3
ALW is offline ALW  United Kingdom
diyAudio Member
 
Join Date: Jun 2001
Location: UK
Default 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.
  Reply With Quote
Old 17th September 2003, 12:11 PM   #4
diyAudio Member
 
Circlotron's Avatar
 
Join Date: Jun 2002
Location: Melbourne, Australia
Default X^2=X+1. 1/X=X-1 Mmmm....

My opinion is that the golden ratio is of better use for the external dimensions of the box so that it looks "right".

Quote:
but some of the effects ascribed to it by Cardas and others just strike me as voodoo for impressionable audioholics.
Fibonacci numbers are really great but I don't think it applies universally. I'm surprised that the revered *Magic Power Cords* are not in fact 1.6180339.... metres long.
__________________
Best-ever T/S parameter spreadsheet.
http://www.diyaudio.com/forums/multi...tml#post353269
  Reply With Quote
Old 17th September 2003, 12:33 PM   #5
Vikash is offline Vikash  United Kingdom
diyAudio Moderator Emeritus
 
Vikash's Avatar
 
Join Date: May 2003
Location: UK
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 re-inforce each other. I think I may have just justified the reasoning for golden ratios
  Reply With Quote
Old 17th September 2003, 01:18 PM   #6
diyAudio Member
 
Christopher's Avatar
 
Join Date: Apr 2003
Location: Hamilton
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
  Reply With Quote
Old 17th September 2003, 01:32 PM   #7
mcp is offline mcp  United States
diyAudio Member
 
Join Date: Jul 2002
Location: Vacation Land
Quote:
Originally posted by Vikash
I've just realised that you need to avoid enclosure dimensions that are multiples of others, as the harmonics will re-inforce each other.
And it's the internal dimensions that's important.
__________________
Michael Chua
  Reply With Quote
Old 17th September 2003, 01:34 PM   #8
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
Originally posted by sfdoddsy
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.

Steve, you've apparently had my house bugged.


Quote:
Doesn't using non parallel sides in an enclosure pretty much deal completely with this problem?
No. It just means that the eigentones will not follow the same pattern as a rectangular box. A sphere doesn't have parallel sides, but it resonates quite nicely. Boxless is still the best (and can be pulled off easily, since you CAN box drivers which are reproducing wavelengths large compared to box dimensions without fear of standing waves). Second best is a box with adequate damping and designed with minimizing reflections back through the cone(s) in mind.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 17th September 2003, 02:06 PM   #9
Vikash is offline Vikash  United Kingdom
diyAudio Moderator Emeritus
 
Vikash's Avatar
 
Join Date: May 2003
Location: UK
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) re-inforcing 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:
using non parallel sides in an enclosure pretty much deal completely with this problem?
My understanding of non-parallell walls is that you're creating/dispersing the standing waves over a wider frequency range, and in doing so the combined mode is of a lesser amplitude.
Attached Images
File Type: gif standing-waves2.gif (6.3 KB, 661 views)
  Reply With Quote
Old 17th September 2003, 03:11 PM   #10
mcp is offline mcp  United States
diyAudio Member
 
Join Date: Jul 2002
Location: Vacation Land
Quote:
I see issues with (for example) the 3rd harmonic (height) and the fundamental (width) re-inforcing each other. Are these the problems you were seeing?
__________________
Michael Chua
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Minimising standing waves GerhardW Multi-Way 13 2nd September 2008 08:43 PM
Standing waves, anyone willing to experiment ? jay1st Multi-Way 4 10th February 2008 02:33 AM
Low resonance and standing waves? Audist Multi-Way 3 6th November 2005 04:29 AM
standing waves and cancellation & exageration ? lolojr1 Subwoofers 13 19th July 2005 06:24 PM
Standing waves again... Vikash Multi-Way 4 4th June 2004 12:25 AM


New To Site? Need Help?

All times are GMT. The time now is 05:59 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2