Ever think of building a Cornu Spiral horn? Now you can! - Page 7 - 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 17th December 2012, 09:01 PM   #61
diyAudio Member
 
Join Date: May 2009
Location: Seattle, WA
OK, I have to build one of these. This project scratches me right where I itch: a conveniently sized rear-loaded horn that will suit my beloved W5-1611s. Luckily for me I'll be spending Christmas with the same mad genius who helped me bang my first speakers together, so I'll just ask him him cut some holes in two pieces of 1/4" plywood and I'll get to gluing. Ooh, I can't WAIT!!!
__________________
Then again, what do I know?
  Reply With Quote
Old 18th December 2012, 12:57 AM   #62
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
Default No luck (yet) with stuffing

I measured the creation last night. Looks about as bad as it sounds. I do not seem to have gotten the stuffing right yet. Below you see the FR and 2nd harmonic distortion with a lightly stuffed box (blue) and very heavily stuffed box (red). More stuffing made it worse.

It's really nice above about 1K, but the horn loading is not yet correct. I'll keep working at it to see what can be done better.
Attached Images
File Type: png mini-stuffing2.png (26.5 KB, 1506 views)
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 18th December 2012, 01:47 AM   #63
diyAudio Member
 
Join Date: May 2009
Location: Seattle, WA
I haven't seen any specifications as to how deep the speaker is. How wide do those strips of foam core board have to be? I'm asking with regard to the 5" speaker version particularly...
__________________
Then again, what do I know?
  Reply With Quote
Old 18th December 2012, 01:50 AM   #64
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
We discussed it in the foam core thread. Basically we have been scaling the depth of the channels such that the throat area (2 of them) equal the driver piston area Sd.
For 5 in driver it will be between 4.5 and 5 inches depth.
  Reply With Quote
Old 18th December 2012, 01:58 AM   #65
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
Quote:
Originally Posted by Pano View Post
I measured the creation last night. Looks about as bad as it sounds. I do not seem to have gotten the stuffing right yet. Below you see the FR and 2nd harmonic distortion with a lightly stuffed box (blue) and very heavily stuffed box (red). More stuffing made it worse.

It's really nice above about 1K, but the horn loading is not yet correct. I'll keep working at it to see what can be done better.
Pano,
Thanks for someone finally doing a real measurement. So, you have not been able to achieve a level of stuffing that sounds good? How far away are you doing the measurement? One thing about the Cornu Is that it really depends on the room integration of the outputs from the horns to smooth out the output form the back horn and combine it with the direct output of the driver. Try the measurement at least at 3 to 4 meters away - which is where I think it starts to sound really nice. Also, how do you have it mounted - on a wall at ear height or just on a bench?
It makes a huge difference. Good luck and keep playing with stuffing. Loose in first few inches of throat and a lot more in chamber is what I have and I used pillow stuffing.
Thanks,
Xrk971
  Reply With Quote
Old 18th December 2012, 02:21 AM   #66
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
The measurements were taken with the speaker flat on the floor, thus plenty of "wall" for the back plane. Mic is 2 feet above the speaker cone, which I figured should be plenty. I may be able to go up another foot.

Will continue to work with stuffing techniques. I also used pillow stuffing. FWIW, spiral depth is 2.5"
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 18th December 2012, 02:32 AM   #67
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
Quote:
Originally Posted by Pano View Post
The measurements were taken with the speaker flat on the floor, thus plenty of "wall" for the back plane. Mic is 2 feet above the speaker cone, which I figured should be plenty. I may be able to go up another foot.

Will continue to work with stuffing techniques. I also used pillow stuffing. FWIW, spiral depth is 2.5"
2 ft not enough for room reflections of horn to blend out.
Try wall mount and back off at least 6 to 8 ft.
  Reply With Quote
Old 18th December 2012, 02:39 AM   #68
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Milliways
Blog Entries: 4
If I do that, then the room comes into play. I know that's important to actual listening, but it gets hard to judge the speaker itself. Am I measuring the room, or the speaker?
As measured, the first reflection (ceiling bounce) comes at 18.75ms, and it's down ~23dB.

I'll do some more tomorrow if I get the chance. Will report back here. It's not a bad sounding speaker, just heavy and somewhat colored. I hope to tune it up.
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 18th December 2012, 08:35 AM   #69
diyAudio Member
 
Join Date: Mar 2011
Quote:
Originally Posted by xrk971 View Post
Switters,
I like how you did it the manly way: triangle, dividers, ruler, pencil, and steady hands! I drew mine by hand using the grid method too. There is just something cool about laying down the spirals into a path that you drew yourself rather than a printout.
Looking forward to hearing your impressions of first sound. I forgot or did not see in your earlier post - what driver are you using?
I'll try two drivers I have at hand: Fountek FE85 (link) and Visaton FRS8M (link).

The "manly way"? I like your interpretation
I believe it was more the... lazy way I had no time/desire to scale, split and print by myself or to go to a reprographic shop.
But it's true, I too believe there is something cool in geometry (maybe the same "coolness" that is deep behind music or architecture?) and in using drawing tools.

PS: maybe unnecessary to told, but english is not my mother tongue, so, please, forgive any incongruity...
  Reply With Quote
Old 18th December 2012, 02:22 PM   #70
gpapag is offline gpapag  Greece
diyAudio Member
 
gpapag's Avatar
 
Join Date: Nov 2002
Location: Athens-Greece
Quote:
Originally Posted by Pano View Post
I measured the creation last night. Looks about as bad as it sounds. I do not seem to have gotten the stuffing right yet. Below you see the FR and 2nd harmonic distortion with a lightly stuffed box (blue) and very heavily stuffed box (red). More stuffing made it worse.

It's really nice above about 1K, but the horn loading is not yet correct. I'll keep working at it to see what can be done better.
Pano
Thanks for sharing.
Is the driver you used the Vifa TC9FD-18-08 3.5" Full Range ?
If this is the one, see the published FR. It slopes at ~12db/oct below 100Hz. Yours slopes at ~24db/oct from there.
This does not indicate a back horn loading.
If you take an impedance sweep, the shape at LF will tell more about what actual loading -if any-the driver is been subjected to.

The deep notch just above 200Hz is for the improper integration btn front and side emitted sound. It has to do with front and rear path lengths and the soundwaves phase relationship at the point they mix (“horn” mouth output).
As it is a phase issue, stuffing can not cure this.

Your distortion plots alone, hints to both inadequate LF loading as well as phase issues at ~ 200Hz.

I do some head scratching these days on the possible operation modes of this design. I hope to type a few words here to see if it makes sense to you.

George
Attached Images
File Type: jpg Pano's.jpg (163.3 KB, 1126 views)
__________________
["Second Law is a bitch." - SY] ["The Road To Heaven:Specify the performance & accept the design. The Road To Hell:Specify the design & accept the performance"-Bruno Putzeys]
  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 11:57 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