Organic Enclosure Shapes: We need to talk. - Page 2 - 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 11th August 2004, 12:46 PM   #11
diyAudio Member
 
Josephjcole's Avatar
 
Join Date: Jun 2004
Location: Wisconsin
I would just like to point you to the 1951 JAES article by Harry Olsen, which is sited in 'the LoudSpeaker Design Cookbook'. In that article the author tested different shapes and found the cube to have what is discribed as 'constantly undulating [FR] with 5dB variations' as opposed to the sphere which was only +/-.5dB. I don't know the exact detail, such as the construction of the box, or the method of measurement I just thought that you might find that interesting.
Joe
  Reply With Quote
Old 11th August 2004, 12:49 PM   #12
tiroth is offline tiroth  United States
diyAudio Member
 
Join Date: Dec 2001
Location: Pittsburgh, PA, USA
Joseph, that is a diffraction effect. It does bring up an interesting point; the shape of the inside of the box need not match the shape of the exterior.
  Reply With Quote
Old 12th August 2004, 02:19 AM   #13
diyAudio Member
 
Josephjcole's Avatar
 
Join Date: Jun 2004
Location: Wisconsin
tiroth,
You'll have to forgive my ignorance and explain to me how you can measure diffraction as opposed to standing waves inside the cabinet when you measure far field in an anechoic chamber? maybe I misread somewhere, but I believe both were measured far field.
Joe
  Reply With Quote
Old 12th August 2004, 05:28 AM   #14
navin is offline navin  India
diyAudio Member
 
navin's Avatar
 
Join Date: Jan 2002
Location: Mumbai (Bombay), India
Send a message via MSN to navin Send a message via Yahoo to navin
Quote:
Originally posted by tiroth
Joseph, that is a diffraction effect. It does bring up an interesting point; the shape of the inside of the box need not match the shape of the exterior.
Now this is getting intersting. i know some guys wo built a box that was square on the ouside and parabolic on the inside. this might be the WORST of both worlds.

Maybe we shoudl look at this the other way - curved on the ooutside, cube inside.

What say mark?
__________________
...still looking for the holy grail.
  Reply With Quote
Old 12th August 2004, 07:32 AM   #15
diyAudio Member
 
Hybrid fourdoor's Avatar
 
Join Date: May 2003
Location: Ft. Worth, TX
That would certainly create some large voids within the enclosure.....Could have alot of dampening material in there
__________________
I enjoy my organic shapes.....
  Reply With Quote
Old 12th August 2004, 09:20 AM   #16
diyAudio Member
 
Join Date: May 2002
Location: Switzerland
There are four things we have to care about, regarding enclosures (I am not talking about any sort of waveguides, in order to not make it even more complicated):

1.) Diffraction
2.) Internal standing waves
3.) Vibrations (i.e. wall-flexing)
4.) Ease of manufacture (i.e. price)

A square box only wins in category 4 !!!!!!!

Unfortunately that is the reason why my boxes so far were of this type as well !

Regards

Charles
  Reply With Quote
Old 12th August 2004, 10:01 AM   #17
diyAudio Member
 
Artmaster's Avatar
 
Join Date: May 2004
Location: Kiev
Blog Entries: 1
Send a message via ICQ to Artmaster Send a message via MSN to Artmaster
Quote:
Originally posted by phase_accurate
1.) Diffraction
2.) Internal standing waves
4.) Ease of manufacture (i.e. price)
hello!
I think we're talking about low fr. part of sound waves.
this frequency have to be commensurable quantities about wave-length.
it means ..... metres. so,
1.) Diffraction
2.) Internal standing waves - problem for middle range of waves.
about 3.) Vibrations (i.e. wall-flexing) - we have to make box using strong materials.
__________________
Artmaster live in www.artmaydan.org.ua
  Reply With Quote
Old 12th August 2004, 11:10 AM   #18
tiroth is offline tiroth  United States
diyAudio Member
 
Join Date: Dec 2001
Location: Pittsburgh, PA, USA
Quote:
Originally posted by Josephjcole
tiroth,
You'll have to forgive my ignorance and explain to me how you can measure diffraction as opposed to standing waves inside the cabinet when you measure far field in an anechoic chamber?
Joe
We can't, looking only at the FR measurement of a system, deduce what part of the FR variance is diffraction versus standing waves. But my response was directed at your comment about square baffle shape causing up to 5dB response variations. Here, the variable under test was only the baffle shape, and 100% of the variation was due to diffraction. That wasn't what Mark was looking at--his argument was more like "given an 'ideal' enclosure shape, do the negative effects of the internal shape swamp the positives of the external?"

Now, if you do a test like Mark did, you can take a look at the comparison between enclosures. Rather than smoothing out any humps the output is increased across a broad portion of the spectrum in the 'egg' case. This indicates to me that 'standing wave' effects are swamping diffraction effects in terms of the difference between these enclosures. Having access to more data would improve our ability to analyze it.
  Reply With Quote
Old 12th August 2004, 02:00 PM   #19
Volenti is offline Volenti  Australia
diyAudio Member
 
Join Date: Aug 2003
Location: Australia
Quote:
Originally posted by phase_accurate


1.) Diffraction
2.) Internal standing waves
3.) Vibrations (i.e. wall-flexing)
4.) Ease of manufacture (i.e. price)

Charles

This sounds fair enough, it's of particular interest to me since I'm currently agonising over the cabnet design of my 3 way main speakers.

1.) Diffraction;

So what does everyone consider to be a "good" external shape? , I'm personally leaning towards either a cylinder or truncated cone (with drivers suitably flush mounted)

2.) Internal standing waves;

This area I'm mainly only worried about the midrange, I make bass enclosures for a living so I have that area taken care of to my satisfaction, but the critical midrange (5'' peerless mid) area is still giving me concerns.

3.) Vibrations (i.e. wall-flexing);

I plan to use a spaced out fibreglass skin (external shape) over a heavily braced timber internal enclosure, with sand filling the cavity, once a suitable midrange enclosure shape is found this is pretty straight forward.


4.) Ease of manufacture (i.e. price);

hea, its diy afterall

opinions, ideas, more than welcome.
  Reply With Quote
Old 12th August 2004, 05:50 PM   #20
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
from page 23 of Olson's Acoustical Engineering:

Click the image to open in full size.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  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
visio shapes desmondmonster Tubes / Valves 4 13th January 2009 07:30 PM
Organic Transistors in Hi-Fi ? patch Parts 1 6th December 2007 04:49 PM
Graph shapes Danielb Multi-Way 9 3rd November 2004 12:26 AM
Kemet A700 ALuminum Organic SMT caps? BrianL Parts 3 4th August 2004 08:16 AM
Are you looking for suggestions for enclosure shapes? kneadle Multi-Way 4 2nd March 2003 02:42 PM


New To Site? Need Help?

All times are GMT. The time now is 07:24 PM.


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