Ever think of building a Cornu Spiral horn? Now you can! - Page 20 - diyAudio
Go Back   Home > Forums > Loudspeakers > Full Range

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 29th December 2012, 03:59 PM   #191
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
Default Cornu as MLTL?

I am testing different horn designs in HornResp and going off-design from original Cornu now. I started with a clean slate and tried various horn profiles that will produce deeper bass extension while having relatively even levels of peaks in the mid-bass region that are equivalent to the main low bass peak. The thinking is if they are even they can be attenuated and smoothed out with stuffing to match the characteristic SPL curve of the driver. The constraint is that it must be rolled up in a spiral and start from a driver chamber. What I ended up with is a linear conical horn with a restricted terminus to both reduce the bass gain, and to pull the bass extension lower - essentially a mass loaded transmission line. This design can be made without curves, and in fact I think use of straight sections only will provide excellent filtering of the HF resonances that the horn produces. My fear is that due to the abrupt terminus with a restriction, the way the sound exits the edges of the cornu and fills the room may be compromised - it may not have the magical wide image as a result.

The simulation assumed a 4.5 x 4.5 in x 4 in deep driver chamber with 4 paths leading out starting with a 0.4 in throat (each) to a 6.34 in mouth that has a restrictor plate capping it to allow only a 0.5 in wide x 4 in deep exit vent (each). The overall size of the horn rolled up is about 31 in x 31 in x 4 in deep. Quite a bit bigger than the original cornu, and this is only for a smallish 4 in driver (Daytion RS100).

Attached are the schematic diagram of the HR design and SPL simulation. Please let me know your thoughts on this approach. All wrong and ruins magic of the curved bell mouths?
Attached Images
File Type: png Cornu-31x4-MLTL-RS100-SPL.png (57.2 KB, 566 views)
File Type: png Cornu-31x4-MLTL-RS100-Schematic.png (8.9 KB, 557 views)

Last edited by xrk971; 29th December 2012 at 04:04 PM.
  Reply With Quote
Old 29th December 2012, 04:16 PM   #192
diyAudio Member
 
Join Date: Jan 2012
Location: Leersum
wauw...i didn't had any plans on building something but there where plans to build a Cornu spiral and i wanted to build with the Visaton FRS8-8! and possibly with a different material them wood..

So it comes together now.

I wonder if and how it went at Switters with the FRS8 and what dimensions do you have. I don't know why but i had these measurements on a piece of paper:
42*42*6 centimeters that is...
  Reply With Quote
Old 29th December 2012, 05:10 PM   #193
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
Xerxes,
If you have the FRS8 already, then use them. I have used the smaller FRS5 in a 35.5 cm x 35.5 cm x 5 cm deep cornu and it works great. I think the 42 cm size is a bit small, try 48 to 60 cm. Adjust the depth to have throat area (both from driver chamber) to equal Sd of driver. If you haven't bought thr FRS8's yet, I would highly recommend getting the Vifa TC9FD, it is about same size, costs $2 more but is probably superior in performance for Cornu. If going with Vifa make it from 50 cm to 61 cm and about 9 cm deep. It can work as shallow as 6 cm deep but you will have better bass with 9 cm.
Good luck and welcome on board. There is a lot of how to build info on foam core thread.
  Reply With Quote
Old 29th December 2012, 05:13 PM   #194
Speakerholic
diyAudio Moderator
 
Cal Weldon's Avatar
 
Join Date: Jan 2004
Location: Near Vancouver
I just asked this question over in the other thread. So for the 50 cm box, you recommend the Vifa TC9FD with an inside horn depth of 9 cm. What shape? Is the original good or what about the true spiral that you showed earlier?
__________________
Next stop: Margaritaville
Some of Cal's stuff | Cal Weldon Consulting
  Reply With Quote
Old 29th December 2012, 05:32 PM   #195
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
Cal,
9 cm should work well, if not opposed to thicker, go as high as 11 cm to match Sd if using Planet10 plan. The more rounded spiral works too, I think Endia has a plan posted somewhere. If you want to make an exact copy of mine, I can photograph the plan as straight as possible and post image. It has sharp corners inside and curves on outside with a 1.1 in wide throat for 2.38 in deep channel.
  Reply With Quote
Old 29th December 2012, 05:45 PM   #196
diyAudio Member
 
Join Date: Jan 2012
Location: Leersum
Ah thanks. I already have the frs8 lying around so I will go with them. You say adjust the depth etc. I must admit I understand anything about these measurements (I really tried..)

My question would be , if I go with 50 x 50 cm what would the depth of the speaker?
  Reply With Quote
Old 29th December 2012, 05:55 PM   #197
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
Xerxes,
I can't find published Sd for this driver but from photograph, it appears that apex of the surround is same dia as magnet which is 6 cm. Based on this assumption, a speaker depth anywhere from 8.5 to 9 cm should work for a 50 cm x 50 cm cabinet.
  Reply With Quote
Old 29th December 2012, 06:04 PM   #198
diyAudio Member
 
Join Date: Jan 2012
Location: Leersum
Ah thanks, I will go with 9cm I like round numbers....I like it already! Tomorrow I will sort out where to score my board, I can't wait.
  Reply With Quote
Old 29th December 2012, 06:28 PM   #199
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Quote:
Originally Posted by xrk971 View Post
essentially a mass loaded transmission line
Mass-Loaded Voigt. You can reduce the ripple by tapping the driver in part way down the line (Hoe you would do that phyisically is a different challenge.

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
Old 29th December 2012, 06:40 PM   #200
Speakerholic
diyAudio Moderator
 
Cal Weldon's Avatar
 
Join Date: Jan 2004
Location: Near Vancouver
Dave, you happen to have some small drivers you might want to send my way for my brother's project? Contact me email or PM and we can discuss.

Ta.
__________________
Next stop: Margaritaville
Some of Cal's stuff | Cal Weldon Consulting
  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
Line array cornu spiral? jaylgordon Full Range 7 15th December 2013 07:43 PM
Cornu Spiral Copy Horn hersh Full Range 24 7th April 2009 07:20 PM
Cornu spiral horns Cal Weldon Multi-Way 3 14th July 2004 02:51 PM


New To Site? Need Help?

All times are GMT. The time now is 11:19 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