Tweeter CD wave guide - 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 26th December 2012, 12:14 PM   #1
diyAudio Member
 
Join Date: Nov 2005
Location: Norway
Default Tweeter CD wave guide

Robert C White / Rod Elliot have a DIY wave guide design instruction here:

Practical DIY Waveguides - Part 1

(part 2 and 3 of the guide is linked at the bottom)

I have tried to work the formulas into an Excel-spread sheet using the 1500 Hz example in part three, but cannot get the formulas/numbers right: I do not get the same numbers as White / Elliot:

Quote:
If we make angle α = 90 ...

c = ( 720 + 90 ) / 5 = 162

b = 360 - 324 + 90 = 126

W = 1 / 3 * (( 25,306 (126 * 162 + 90 * 162 + 90 * 126 )) / ( 1500 * 90 * 126 * 162) = 142mm
The horn radius is...

R = ( W - t / 2 ) / sin ( α / 2 )
... where t is throat diameter and α is the radiation angle. Throat diameter is determined by the tweeter used, and must be measured carefully. The overall depth is ...

d = R - (Tan a / 2) ( w - t / 2 )
The radius at points x is ...

r ( x ) = ( t / 2 + ( w - t ) / 2 ) - ( R - ( m + d - x ) )
... where m = Tan α / 2 ( 0.5w - 0.5t ) and t = throat diameter. x is the centreline distance along the waveguide from the throat in millimetres.


x R x R x R x R
0 18.5 6 25.2 12 34 18 47
1 19.5 7 26.5 13 35.7 19 50
2 20.6 8 27.8 14 37.6 20 54
3 21.7 9 29.2 15 39.7 21 59
4 22.8 10 30.7 16 42 22 71
5 23.9 11 32.3 17 44
Table 1 - Offset (x) for various values of R
Are the formulas above incorrect, or do I just have to look more into my excel-formulas? I get the numbers corret to "w" (expect I get 0,1418 istead of 142), but after that White / Elliot do not sum the formulas for R, d and r(x), so I do not know in which formula (R, d og r(x)) my mistake(s) are.

Have anyone made a spread-sheet for designing CD wave guide / Cd horn?

Best regards

Gisle
  Reply With Quote
Old 26th December 2012, 01:08 PM   #2
...truth seeker...
diyAudio Member
 
Ed LaFontaine's Avatar
 
Join Date: Feb 2004
Location: where the Appalachians rise from the Blue Grass
I can provide you with one of a variety of waveguide worksheets that are available. Can you open an excel spreadsheet?
If yes, pm your e-mail address to me and I'll forward it to you.
This one is based upon Geddes' oblate spheroid profile.

Last edited by Ed LaFontaine; 26th December 2012 at 01:10 PM.
  Reply With Quote
Old 26th December 2012, 10:00 PM   #3
DogStar is offline DogStar  Europe
diyAudio Member
 
Join Date: Mar 2011
I think your "mistake" is the number 25,306. In your spreadsheet you should use the number 25306. Notice that in the US they don't use the comma the same way as we do in Scandinavia (or many other European countries). Apart from this detail, your computation looks ok. The following formula (in Excel) gives you the number directly in mm:

= 1000*(1/3)*((25306*(126*162+90*162+90*126))/(1500*90*126*162))

Good luck with the number crunching.

Cheers David

Last edited by DogStar; 26th December 2012 at 10:06 PM.
  Reply With Quote
Old 27th December 2012, 09:22 AM   #4
diyAudio Member
 
Join Date: Nov 2005
Location: Norway
Quote:
Originally Posted by DogStar View Post
I think your "mistake" is the number 25,306. In your spreadsheet you should use the number 25306. Notice that in the US they don't use the comma the same way as we do in Scandinavia (or many other European countries). Apart from this detail, your computation looks ok. The following formula (in Excel) gives you the number directly in mm:

= 1000*(1/3)*((25306*(126*162+90*162+90*126))/(1500*90*126*162))

Good luck with the number crunching.

Cheers David

Aha! Suddenly I blushed... Thanks!

And also thanks to Ed for email.

  Reply With Quote
Old 27th December 2012, 11:54 AM   #5
...truth seeker...
diyAudio Member
 
Ed LaFontaine's Avatar
 
Join Date: Feb 2004
Location: where the Appalachians rise from the Blue Grass
In case you are not aware of his work, Dave Pellegrene is thermo-forming waveguides.

acoustic waveguides

http://techtalk.parts-express.com/sh...ght=pellegrene

Last edited by Ed LaFontaine; 27th December 2012 at 12:00 PM.
  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
Ribbon Tweeter Wave Guide removal? deanxxx Multi-Way 5 4th April 2012 05:14 PM
Ribbon Tweeter Wave Guide removal? deanxxx Parts 0 4th April 2012 03:40 PM
Short Tractrix tweeter wave guide domtw Multi-Way 3 3rd May 2009 04:05 AM


New To Site? Need Help?

All times are GMT. The time now is 02:12 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