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 6th October 2005, 02:01 AM   #1
diyAudio Member
 
Join Date: Apr 2002
Default Horn Mouth Diffraction

Dear all,

It is rather well understood that a finite aperture of a horn/wave-guide causes diffraction effects, [1]. However, neither this reference nor another paper [2], which at least tangentially touches on this issue, gives any insight on computation of a mouth shape that would give an optimal (whatever the criteria) diffraction.

I am also aware of the work of Jean Michel Le Cleac'h [3], but this appears to be concerned with the entire horn contour, and not only the mouth shape. As such, it appears inapplicable to a situations, where a horn contour is pre-determined, e.g., constant directivity.

I would appreciate if anyone, who aware of any theory/papers/software dealing with this issue, could post references.

Thank you,

M

[1] Geddes, E., R.: "Sound Radiation from Acoustic Apertures." JAES., vol. 41, pp. 214-23 (April 1993)
[2] Henwood, D.J.: "The Boundary element method and Horn Design, JAES, vol. 41, pp. 485-496 (June 1993)
[3] http://ndaviden.club.fr/pavillon/lecleach.htm
  Reply With Quote
Old 6th October 2005, 05:17 AM   #2
al2002 is offline al2002  India
diyAudio Member
 
al2002's Avatar
 
Join Date: Dec 2003
Location: USA
The best reference, in fact the only reference I know of, on this topic is Geddes' book, "Audio Transducers". I strongly recommend it.

It can be ordered directly from his site: www.gedlee.com.


A sample calculation may be seen here:

http://gedlee.com/downloads/Appendix_A.pdf

Hope this helps.
  Reply With Quote
Old 6th October 2005, 05:53 AM   #3
diyAudio Member
 
Join Date: Apr 2002
Dear al2002,

thank you for the reference.

However, it seems to me that we are micommunicating because the link that you have posted treats calculation of a wave propagation throug a wave-guide assumed to be conical; therefore, without mouth flare.

The only comment related to my inquiry is on p. 302: ". . . waves reflected . . . can be reduced by radius'd (flared) mouth treatment as we discussed in Sec. 6.6."

Could you tell me if Sec. 6.6. contains any theoretical derivation of the flare or just states to do so?

M
  Reply With Quote
Old 6th October 2005, 06:42 AM   #4
diyAudio Member
 
Cloth Ears's Avatar
 
Join Date: Dec 2001
Location: Melbourne, Australia
Is this (http://www.users.onaustralia.com.au/...phd/thes.ps.gz) along the lines of what you're looking for? I haven't read it yet as I haven't been able to grab the printer for long enough.
__________________
Jont.
"It is impossible to build a fool proof system; because fools are so ingenious."
  Reply With Quote
Old 6th October 2005, 10:07 AM   #5
jomor is online now jomor  Greece
diyAudio Member
 
jomor's Avatar
 
Join Date: Feb 2004
Location: Athens
Default Re: Horn Mouth Diffraction

Quote:
Originally posted by mefistofelez
Dear all,

It is rather well understood that a finite aperture of a horn/wave-guide causes diffraction effects, [1].
.
.
.

I would appreciate if anyone, who aware of any theory/papers/software dealing with this issue, could post references.

http://www.nutshellhifi.com/library/...r-design1.html

Look at the Horn paragraph. In fact, the whole article is a "must read".
  Reply With Quote
Old 6th October 2005, 10:45 AM   #6
pooge is offline pooge  United States
diyAudio Member
 
Join Date: May 2003
Location: Northern Va.
http://db.audioasylum.com/cgi/m.mpl?...pooge&session=
  Reply With Quote
Old 6th October 2005, 03:32 PM   #7
al2002 is offline al2002  India
diyAudio Member
 
al2002's Avatar
 
Join Date: Dec 2003
Location: USA
Quote:
Originally posted by mefistofelez
Dear al2002,

thank you for the reference.

However, it seems to me that we are micommunicating because the link that you have posted treats calculation of a wave propagation throug a wave-guide assumed to be conical; therefore, without mouth flare.
M
No miscommunication. The link was only given to illustrate the standard of the book. It does not, of course, show a diffraction calculation.
Quote:

The only comment related to my inquiry is on p. 302: ". . . waves reflected . . . can be reduced by radius'd (flared) mouth treatment as we discussed in Sec. 6.6."

Could you tell me if Sec. 6.6. contains any theoretical derivation of the flare or just states to do so?

M
Yes, it does.
  Reply With Quote
Old 6th October 2005, 03:38 PM   #8
diyAudio Member
 
Join Date: Jan 2004
Location: Toronto, ON, Canada
Quote:
Originally posted by pooge
http://db.audioasylum.com/cgi/m.mpl?...pooge&session=
Quote:
"Earl, in your waveguide paper you dealt with a radius at the baffle, but didn't specify its curvature. Can you eloborate on this?" The radius should really be as large as a wavelength of the lowest frequency, but a rule of thumb says that it should be no less than 1/4 wavelength at the lowest frequency of waveguide use. This will diffract a lot less energy, but still a significant amount at the lowest frequencies.
  Reply With Quote
Old 6th October 2005, 06:01 PM   #9
pooge is offline pooge  United States
diyAudio Member
 
Join Date: May 2003
Location: Northern Va.
Earl Geddes uses a 2" radius on his waveguides
  Reply With Quote
Old 6th October 2005, 06:07 PM   #10
al2002 is offline al2002  India
diyAudio Member
 
al2002's Avatar
 
Join Date: Dec 2003
Location: USA
Quote:
Originally posted by pooge
Earl Geddes uses a 2" radius on his waveguides

I believe it is the cabinet edge radius which is 2". The waveguide itself has a 4" flare at the mouth.

Also, in response to an earlier post, Geddes' recommends a lambda/2 flare at the mouth.
  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
Horn mouth bubble size MaVo Subwoofers 1 25th February 2009 11:59 AM
Horn mouth venting to the floor Tyimo Full Range 8 22nd February 2008 06:53 PM
rear horn mouth area big_kahunah Full Range 1 16th August 2005 01:35 AM
Screen in horn mouth? Stocker Multi-Way 7 9th March 2005 09:39 AM
Horn speaker w/variable throat & mouth bbaker6212 Multi-Way 1 1st August 2003 07:27 AM


New To Site? Need Help?

All times are GMT. The time now is 06:55 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