Spreadsheet for Folded Horn Layouts... - Page 2 - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

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 12th August 2010, 07:33 PM   #11
diyAudio Member
 
BP1Fanatic's Avatar
 
Join Date: Jan 2009
Location: Columbus, Ohio
How about an IF/THEN Statement:
Blue = [{Vol (1) = Vol (2)} + balance = 0.00]?

Click the image to open in full size.

Click the image to open in full size.
  Reply With Quote
Old 12th August 2010, 07:46 PM   #12
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by soho54 View Post
When you say "centerline" do you mean right angles through the corners? If so, this will always be a little long, and the horn will play shorter.
I used that approach.

I also measured using arcs around the corners, and present that in the spreadsheet as L'.

I've also included the srqt method in the spreadsheet. Interestingly enough, the answer it gives is usually within a few mm of the centerline method.
  Reply With Quote
Old 12th August 2010, 08:18 PM   #13
soho54 is offline soho54  United States
diyAudio Member
 
Join Date: Nov 2005
Location: Georgia
Quote:
Originally Posted by Brian Steele View Post
I've also included the srqt method in the spreadsheet. Interestingly enough, the answer it gives is usually within a few mm of the centerline method.
Hmm... something seems off. EDIT: I read this wrong.

Here is a picture with a bend made up of three 25cm squares, and the lengths derived from the most popular methods, and my own in the middle.

Click the image to open in full size.
The Square-root method comes in at 70.71.

Try running this through your program to see what it comes up with.

Last edited by soho54; 12th August 2010 at 08:22 PM.
  Reply With Quote
Old 12th August 2010, 08:22 PM   #14
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by BP1Fanatic View Post
How about an IF/THEN Statement:
Blue = [{Vol (1) = Vol (2)} + balance = 0.00]?

Click the image to open in full size.

Click the image to open in full size.
Vol (1) is calculated using S1, S4 and L, and it's not dependent on any of the measurements of the box, so it's somewhat misleading at this point.

I'll adjust the spreadsheet to reflect the correct net volume of the box.

"balance" is the difference in height between the front and back of the box, using the calculated values for the folded horn's dimensions in the box. For the box to actually be a box, it should be zero. This is where Excel's "Goal Seek" function comes in handy .
  Reply With Quote
Old 12th August 2010, 08:23 PM   #15
Mark Kravchenko --- www.kravchenko-audio.com
diyAudio Member
 
mwmkravchenko's Avatar
 
Join Date: Jan 2002
Location: Perth Canada
Hi Brian

Home early from work with a tummy ache. But a whole lot oh gingerale and I'm getting better.

Been playing with the spreadsheet. Boy am I stupid. It finally dawned on me that the thickness of the material is in cm not mm. Now the folds make sense.

Still have not quite figured out the goal seek function. I found it but hell if I know how to make it work. But fiddle with the box sizes enough and I get pretty close to the desired sizes.

I have to say cool.

And I have to agree that from a viewpoint of your math skills the descrepancy you described earlier is significant. A real life box rarely measures as modeled. It is always close. But I'm guessing you want to get as close as is posible.

Mark
__________________
Mark
  Reply With Quote
Old 12th August 2010, 08:27 PM   #16
soho54 is offline soho54  United States
diyAudio Member
 
Join Date: Nov 2005
Location: Georgia
Did you ever throw your TH model into AkAback to see if the p or c constants used in HR were the reason for your 3Hz measurement difference?
  Reply With Quote
Old 12th August 2010, 08:36 PM   #17
Mark Kravchenko --- www.kravchenko-audio.com
diyAudio Member
 
mwmkravchenko's Avatar
 
Join Date: Jan 2002
Location: Perth Canada
I have been reading the thread. As Brian pointed out the method of measureing down the middle of the bends is one of the most accurate means of determining horn path length when it is folded. That is what I have used for years.

I tried a front loaded horn that is obviously tappered. I can't get the crazy thing to behave. My deviation from error is small but it don't look like a horn to me! I even used the as built sizes. I'll check what I did again and see if there are any obvious mistakes.

I have a couple of ideas for labeling the cells so it is a bit easier to

Mark

Mark
__________________
Mark
  Reply With Quote
Old 12th August 2010, 08:45 PM   #18
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by soho54 View Post
Did you ever throw your TH model into AkAback to see if the p or c constants used in HR were the reason for your 3Hz measurement difference?
No, not yet. I'm an absolute noob wrt Akabak.
  Reply With Quote
Old 12th August 2010, 08:48 PM   #19
Mark Kravchenko --- www.kravchenko-audio.com
diyAudio Member
 
mwmkravchenko's Avatar
 
Join Date: Jan 2002
Location: Perth Canada
From David McBean he is actually gone past AkaBak in computaional accuracy. His programis just a bit more limited. I can attest to it's acuracy as can Brian. It is really close to what you will measure in the real world if you actually make the box well.

Mark
__________________
Mark
  Reply With Quote
Old 12th August 2010, 08:55 PM   #20
diyAudio Member
 
Join Date: Nov 2007
Quote:
Originally Posted by mwmkravchenko View Post
I tried a front loaded horn that is obviously tappered. I can't get the crazy thing to behave.
LOL - that probably wouldn't work. The spreadsheet can only model the layout of the folded TH as illustrated in the graph, as that's the only one I can mathematically describe at the moment (I really have to spend some time and show the position of the driver in the TH!).

Once I can work out other foldings, I'll include them in the spreadsheet.
  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
Folded horn length Don Snyder Subwoofers 3 1st May 2009 11:14 PM
how to go from horn response to a folded bass horn design? paulspencer Subwoofers 8 4th November 2005 10:44 PM
Looking For Folded Horn Sub Plans nniwelt Subwoofers 16 29th August 2005 04:43 AM
Folded horn for Tannoy? panos29 Multi-Way 12 17th October 2003 08:59 AM


New To Site? Need Help?

All times are GMT. The time now is 06:27 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