front loaded horn for the fostex fe 168 sigma? - 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 20th January 2006, 03:50 AM   #1
diyAudio Member
 
Join Date: Aug 2005
Default front loaded horn for the fostex fe 168 sigma?

Has anyone here tried this driver with a front horn loading? I'm looking for something to start off with rather simply, to play around with some profiles. Thought the Oris horns were rather nice when I heard them last, and wa thinking this might be a nice driver to try my hand with for not too much dough. I'm open to other drivers as well, especially if I'm looking at cheaper drivers Just getting my horn feet wet now, and I figure the best way to do that is with an inexpensive project. That, and I want to try out some ideas for fabrication.
  Reply With Quote
Old 20th January 2006, 08:01 AM   #2
diyAudio Member
 
Scottmoose's Avatar
 
Join Date: Mar 2005
Location: UK
Can't see any reason why not. Don't forget the standard Fostex FE206E or FE207E either though. First stop if you haven't been there already: http://www.quarter-wave.com/Horns/Front_Horn.pdf for background reading, then get Martin's worksheet.

Cheers
Scott
__________________
Community site www.frugal-horn.com
  Reply With Quote
Old 20th January 2006, 07:36 PM   #3
robertG is offline robertG  Canada
diyAudio Member
 
Join Date: May 2005
Location: Montreal
Works very well!

I don't know why people don't seem to use it in Oris-type of front horn, cause the driver's drawbacks (HF harshness) makes it ideal for such a use, as the front horn will bump up mids a lot more than the HF peaks, thus balancing the sound a bit. You probably will want a ST as well.

I tried the 168 in a 250Hz horn and was amazed by the results. I also made a baby oris for a FE108 with really good results too!

Now I'M trying to find a platic shop who can make the horns for the DIY market.

All in all, it's a nice way to use these drivers and you get awesome SPL as a bonus (down side, you need a bass cabinet that will match SPL...)

Good luck with your project.

Robert

By the way, you will need a small enclosure behind the driver, and it's a good idea to make it reflex, tuned at (or just below) the horn's LF cut-off to restrict cone movement.

I fried a 108 while running it full-range, so it also needs to be high-passed.

www.gemmeaudio.com
  Reply With Quote
Old 21st January 2006, 01:56 AM   #4
diyAudio Member
 
Join Date: Aug 2005
I'm rather computer un-savvy, so I've been unable to run any of the spreadsheet horn calculation applets. I don't have Excel, as I use Macintosh, and the MSOffice suite is hugely expensive. I can't seem to find it for sale by itself. I'm wondering if someone might be able to model this horn for me. I'm building a machine to fabricate the hard bits, as thats my specialty. I just need something better than my intuition to guide me in laying out the curves.
  Reply With Quote
Old 21st January 2006, 09:53 AM   #5
diyAudio Member
 
Scottmoose's Avatar
 
Join Date: Mar 2005
Location: UK
I'm no expert on front loaded horns -I've never had cause to model one before. However, after playing around in MathCad for a few minutes,this doesn't seem to be too bad, as far as FLHs go, for a first quick pass. It uses some of the dimensions Martin refers to in his FLH article, with modifications to the size of the rear chamber. Data entered is shown below, frequency response in the next post:
Attached Images
File Type: gif fe168esigma flh.gif (9.8 KB, 1049 views)
__________________
Community site www.frugal-horn.com
  Reply With Quote
Old 21st January 2006, 09:55 AM   #6
diyAudio Member
 
Scottmoose's Avatar
 
Join Date: Mar 2005
Location: UK
And here's the predicted response. Remember in these models, the driver is mounted with the rear venting into a sealed box, in this case with a front and rear area equal to 4 times the driver surface area, and 4" deep. It fires forward into a much smaller front chamber, with front and rear areas equal to 1.5 times the driver's surface area, and 2" deep. The horn is attached to the front of this. It's throat area is equal to the surface area of the driver. It is 21.5" long, and its mouth is equal to 20.2 times the surface area of the driver.

Well, it's a start anyway!

Best
Scott
Attached Images
File Type: gif fe168esigma flh resp.gif (15.1 KB, 988 views)
__________________
Community site www.frugal-horn.com
  Reply With Quote
Old 21st January 2006, 12:43 PM   #7
diyAudio Member
 
Join Date: Aug 2005
Thanks for running that for me, Scottmoose. Looks pretty good, actually, but it looks like you used the data for the 208. The top (phase) plot is interesting, though. Now, assuming the 208, how do I go about creating the physical profile? Do I simply plug in the distance from the throat, etc. to the exponential formulae? My intent is to plot a template for a cutting tool to follow, so these can be turned from a suitable material, or to make a multi sectioned bowl, with the profile bent or cut into the sections. Ultimately, I'd like my large CNC router to do this automatically.
  Reply With Quote
Old 21st January 2006, 01:40 PM   #8
diyAudio Member
 
Scottmoose's Avatar
 
Join Date: Mar 2005
Location: UK
It is the data for the 168 -don't worry. The reference to the 208 is due to that driver being the default that's loaded into the worksheet. I changed the parameters, but I didn't re-name the driver in the title part up-top. Sorry for any confusion!

The get the physical profile, you'll simply need to plug the throat, mouth and length shown into the exponential formulae, as you mentioned above. The rear and front chambers are easy enough of course. I've no idea how you'd go about building one, apart from with great difficulty, but your above suggestions sound about right!

Best
Scott
__________________
Community site www.frugal-horn.com
  Reply With Quote
Old 22nd January 2006, 02:09 PM   #9
diyAudio Member
 
Join Date: Aug 2005
What did you set for the flare frequency? I was going to try running either 250 or 150hz. Also, I cant get the Sd in your example to jibe with the published specs: Moving piston is given as 60mm. The Sd listed in the factory specs states .0113m3, and I can acheive that result using the published number for "a", which I'm assuming is the piston radius. Is the factory Sd spec the one I should be using when creating the physical model?
  Reply With Quote
Old 22nd January 2006, 03:12 PM   #10
diyAudio Member
 
Scottmoose's Avatar
 
Join Date: Mar 2005
Location: UK
Sd in Martin King's back-loaded or front loaded horn models is irrelevant. Hense the fact that there isn't anything entered by myself in that parameter; it's a bit confusing to begin with I know, but if you go to www.quarter-wave.com and read his articles on the design of horns, it will become clearer.

Here's a quote from the conclusions of his article on the design of a front loaded exponential horn:

"When sizing the front exponential horn sub-system, it is interesting to note that the driverís size and Thiele / Small parameter do not enter into the calculations. The lower cut-off frequency fc determines the mouth cross-sectional area. The throat area and horn length are determined by the desired SPL boost above the lower cut-off frequency fc. Given two similar drivers that vary only in diameter, the same size horn
mouth would result for the same low cut-off frequency fc. The same exponential front horn could be used for similar eight inch and six inch diameter drivers."

Hope that's a help.

Best
Scott
__________________
Community site www.frugal-horn.com
  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
Front loaded and back loaded horn DrWoofer.com Subwoofers 0 3rd August 2007 06:55 PM
Front loaded horn concepts rabw Full Range 62 25th May 2006 12:17 AM
Recomended back loaded horn FE108E Sigma Alexandertol Full Range 2 22nd February 2005 06:04 PM
help with front loaded horn designs -please juddr Multi-Way 8 15th November 2004 09:02 PM


New To Site? Need Help?

All times are GMT. The time now is 09:25 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