Hornresp - Page 219 - 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 27th August 2011, 07:58 AM   #2181
diyAudio Member
 
Join Date: Jun 2007
Quote:
Originally Posted by dirkwright View Post
Is that because he made a mistake in the spreadsheet? The mouth areas are the same, the throat areas are close, but only the length is different. I used the system designer tool in Hornresp to build the horn there.
Hi dirkwright,

It seems that there may be an error in the spreadsheet methodology.

For Placement = 4, the mouth area is divided by 4 as expected, but the new length is calculated assuming that the truncated mouth is fully formed, which is not really the case. This questionable assumption means that the profile cutoff frequency becomes 120 hertz rather than the required 60 hertz - which explains why the spreadsheet horn is shorter than it should be.

Spreadsheet:

Fc = 60 Hz
Placement = 4
At = 178.8 sq cm
Am = 6539.5 sq cm
Length = 68.43 cm

Hornresp:

S1 = 178.80 sq cm
S2 = 6539.49 sq cm
L12 = 68.42 cm
F12 = 120 hertz

Note that when Fc is changed to 120 hertz in Hornresp, the results become the same - allowing for the slight differences in mouth area and length due to rounding, as mentioned previously.

Kind regards,

David
__________________
www.hornresp.net
  Reply With Quote
Old 27th August 2011, 02:16 PM   #2182
diyAudio Member
 
dirkwright's Avatar
 
Join Date: May 2011
Location: Virginia
Quote:
Originally Posted by David McBean View Post
Hi dirkwright,

Have a look at the formula in the spreadsheet used to calculate Rm (mouth radius). The velocity of sound value used here is 340 m/sec. Change this to 344 m/sec and you will now get effectively the same results as those calculated by Hornresp - allowing for the very slight differences in mouth area and length due to rounding.

Spreadsheet:

Fc = 60 Hz
Placement = 1
At = 178.8 sq cm
Am = 26158.0 sq cm
Length = 199.63 cm

Hornresp:

S1 = 178.80 sq cm
S2 = 26157.99 sq cm
L12 = 199.62 cm
F12 = 60 hertz

Kind regards,

David
Holy Crap!!!!! Thank you thank you thank you!!!!

Erik made a mistake !!!!
  Reply With Quote
Old 27th August 2011, 02:21 PM   #2183
Mark Kravchenko --- www.kravchenko-audio.com
diyAudio Member
 
mwmkravchenko's Avatar
 
Join Date: Jan 2002
Location: Perth Canada
Quote:
Erik made a mistake !!!!
THem who make no things make no mistakes!
__________________
Mark
  Reply With Quote
Old 28th August 2011, 12:28 AM   #2184
diyAudio Member
 
dirkwright's Avatar
 
Join Date: May 2011
Location: Virginia
Quote:
Originally Posted by David McBean View Post
Hi dirkwright,

It seems that there may be an error in the spreadsheet methodology.

For Placement = 4, the mouth area is divided by 4 as expected, but the new length is calculated assuming that the truncated mouth is fully formed, which is not really the case. This questionable assumption means that the profile cutoff frequency becomes 120 hertz rather than the required 60 hertz - which explains why the spreadsheet horn is shorter than it should be.

Spreadsheet:

Fc = 60 Hz
Placement = 4
At = 178.8 sq cm
Am = 6539.5 sq cm
Length = 68.43 cm

Hornresp:

S1 = 178.80 sq cm
S2 = 6539.49 sq cm
L12 = 68.42 cm
F12 = 120 hertz

Note that when Fc is changed to 120 hertz in Hornresp, the results become the same - allowing for the slight differences in mouth area and length due to rounding, as mentioned previously.

Kind regards,

David
Thanks again David! You've been very helpful. I still can't believe this software is free!
  Reply With Quote
Old 28th August 2011, 06:56 AM   #2185
diyAudio Member
 
Join Date: Jun 2007
Quote:
Originally Posted by dirkwright View Post
Thanks again David! You've been very helpful.
Hi dirkwright,

You're welcome :-).

It is interesting how the (corrected) spreadsheet assumes that a tractrix horn having S1 = 178.80, S2 = 6539.49 and L12 = 68.42 radiating into 1Pi space will have a performance comparable to a tractrix horn having S1 = 178.80, S2 = 26157.99 and L12 = 199.62 radiating into 4Pi space.

As can be seen from the attachment, a quick check in Hornresp shows that this is clearly not the case - the black trace shows the response for the 1Pi horn and the gray trace shows the response for the 4Pi horn.

Kind regards,

David
Attached Images
File Type: png Compare.png (25.5 KB, 115 views)
__________________
www.hornresp.net
  Reply With Quote
Old 28th August 2011, 02:34 PM   #2186
diyAudio Member
 
dirkwright's Avatar
 
Join Date: May 2011
Location: Virginia
Thanks again for your analysis David. I'm very impressed with your enthusiasm. I just have one question about your program. Why is it not possible to increase the window size? I assume this is intentional, but don't know why.

Once I get some other projects out of the way, I'll be building a 1/2 size 100Hz hyp-ex straight horn using data from your program. You've made a huge contribution to horn loudspeaker design. You should be very proud of your accomplishment.
  Reply With Quote
Old 28th August 2011, 02:39 PM   #2187
diyAudio Member
 
dirkwright's Avatar
 
Join Date: May 2011
Location: Virginia
Does anyone know what causes this ringing in the impulse response? How do I get rid of it? Suppressing rear chamber resonance doesn't take it away. Thanks.
Attached Images
File Type: jpg 12PE32 100Hz impulse.JPG (32.0 KB, 97 views)

Last edited by dirkwright; 28th August 2011 at 02:47 PM.
  Reply With Quote
Old 28th August 2011, 08:49 PM   #2188
diyAudio Member
 
Join Date: Jun 2004
Location: Indiana
I was modeling a TL enclosure and wanted to mess around with multiple drivers so I changed the number of drivers but nothing changed. In the same size line I got the same response and the same max SPL. Increasing the size of the line (cross section) changed the response in the same way as for a single driver. What am I neglecting? I wanted to model 8 10" drivers connected in series (there is a reason for this).

I would think "n" drivers would require a cross section "n" times that of a single driver no?
__________________
If We The People refuse to hear the truth we will be ruled by liars.
  Reply With Quote
Old 28th August 2011, 09:38 PM   #2189
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Hmm, when I double up drivers it dramatically changes the response, turning a highly under-damped TL to over-damped and increasing its Xmax limited BW +6 dB at its minimum frequency just as it should.

Correct, to maintain the same response the cab's net Vb must increase by however many drivers there are, so if one driver requires 100 cm^2, then eight require 800 cm^2, though you have to manually change the values in the appropriate fields as it won't auto add like some programs.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  Reply With Quote
Old 28th August 2011, 10:27 PM   #2190
diyAudio Member
 
Join Date: Jun 2004
Location: Indiana
Yes, that is how I expected it to act however in my case the only thing that changes is the grey 8s shows up in the ND field. No change in the results when I run the sim though. Maybe I should try with just two drivers and see what happens. Maybe I am just exceeding some internal limit.
__________________
If We The People refuse to hear the truth we will be ruled by liars.
  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
Hornresp Class FlipC Subwoofers 8 3rd November 2008 06:23 PM
Some questions about hornresp brsanko Full Range 4 18th October 2008 09:36 PM
Hornresp help / JX150 316a Multi-Way 0 11th February 2004 03:56 PM


New To Site? Need Help?

All times are GMT. The time now is 08:08 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