Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Folded Back Loaded Horn Design
Folded Back Loaded Horn Design
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 8th May 2018, 05:34 AM   #1
prolow is offline prolow  United States
diyAudio Member
 
Join Date: Apr 2018
Default Folded Back Loaded Horn Design

Based on the info on Folded horn speaker design - explanation and calculator I modeled a folded back loaded horn box for two 3.5" full range drivers.
I initially modeled one targeting 100hz as the low-frequency resonance, but it was inconveniently large(70"h, 16"w, 24"deep) so I then targeted 200hz which resulted in a more reasonable size box(42.5"h, 9.5"w,16"deep).
The horn unfolded is 4"wide the full length, 54.6" long, 8" tall at the throat, 33.5" tall at the mouth.

I've never done this before, so am interested in feedback, like if there's something obviously wrong with the design.
Attached Images
File Type: jpg BLH_200hz_01.JPG (29.3 KB, 333 views)
File Type: jpg BLH_200hz_02.JPG (27.7 KB, 333 views)
File Type: jpg BLH_200hz_03.JPG (25.3 KB, 332 views)
File Type: jpg BLH_200hz_04.JPG (22.0 KB, 334 views)
File Type: jpg BLH_200hz_05.JPG (37.0 KB, 325 views)

Last edited by prolow; 9th May 2018 at 05:04 AM.
  Reply With Quote
Old 8th May 2018, 08:24 AM   #2
perceval is offline perceval  Taiwan
diyAudio Member
 
perceval's Avatar
 
Join Date: Feb 2014
Location: Taiwan
That looks intense! And all that just to reach 200 Hz.

Unless this is considered to be an exercise of style, there are a lot of designs out there that can reach 50Hz...

Did you mean 20Hz, and not 200? ... which would then be much more interesting!
  Reply With Quote
Old 8th May 2018, 02:43 PM   #3
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Really need driver specs and frequency response, so will just say that normally one wants a BLH's HF response to peter out by ~125-250 Hz depending on the app, ergo a 200 Hz cutoff implies it will horn load way too high up in the mids, causing too much out of phase comb filtering with the driver's forward output if not heavily damped, negating most of the horn's high efficiency output.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  Reply With Quote
Old 9th May 2018, 02:06 AM   #4
prolow is offline prolow  United States
diyAudio Member
 
Join Date: Apr 2018
The drivers are nothing special;
Boss BRS35 3.5" dual cone, 50watt, 4ohm, 100hz-18khz.

I wouldn't call it an exercise in style.
Just trying to get the most out of what I have and learn something along the way.
  Reply With Quote
Old 9th May 2018, 05:05 PM   #5
chrisb is offline chrisb
diyAudio Member
 
Join Date: Aug 2002
Location: victoria BC
Well, to repeat Greg's post above, the first thing to learn is that you need driver's T/S parameters for any type of enclosure modeling to be meaningful, and that not all drivers performance is necessarily enhanced by use of a BLH.

OK, that's two things
__________________
Retired from active DIY
  Reply With Quote
Old 9th May 2018, 05:26 PM   #6
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Right, but that said, these type drivers tend to be high Q, so short of the necessary specs....... go 'old school' DIY and do an inverted BIB pipe horn designed based on a 140 Hz Fs, Vas, Qts juggled to get a 70 Hz BIB with a ~96"^2 Sm will probably work well enough and constructing it out of a fairly rigid cardboard box material with hot glue will help to damp it without the need for excessive stuffing.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  Reply With Quote
Old 9th May 2018, 06:27 PM   #7
planet10 is offline planet10  Canada
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Folded Back Loaded Horn Design
I have modified the gamma on your images to make them easier to see.

There is a lot of wasted space in this design. As well one does not need to keep smooth curves. That will allow more unwanted high frequencies to get to the mouth where combing with the direct response will cause combing.

And as GM points out with a BLH one wants to keep the HF response of the horn part to be limited… 250-300 Hz is as high as practical, doing a 200 Hz makes no sense.

WHile the article you point to may be a reasonable primer, it is not all that good a tool for designing horns. There are some good software tools that allow good estimates of what real world response will be.

It is certainly possible to get decent LF from a small “horn”. FH-Lite is an example. Wall/floor, or corner loading can be used to multiply the effective size of the mouth and the modeler will take TL action into account.

Click the image to open in full size.

The Frugel-Horn

dave
Attached Images
File Type: png BLH_200hz.png (196.7 KB, 62 views)
__________________
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 9th May 2018, 06:58 PM   #8
chrisb is offline chrisb
diyAudio Member
 
Join Date: Aug 2002
Location: victoria BC
As the design sketch Dave posted above should by now quite familiar to frequenters of these fora, it should be noted that the FHL(ite) is designed for the approx 3" size range. While "scaling" a design to fit your individual requirement is not always successful this particular folding topology has proven to be very effective in two larger sizes, and for a wide range of drivers in each respective iteration.

While they appear deceptively simple, there was more than a little math involved on the part of Dr Scott.
__________________
Retired from active DIY
  Reply With Quote
Old 10th May 2018, 03:28 AM   #9
prolow is offline prolow  United States
diyAudio Member
 
Join Date: Apr 2018
Thanks for the response guys.
There's clearly a lot I don't understand here(particularly the comment about how smooth curves might be undesirable in this use case, implying that sharp angles dampen the HF output from the horn), and/or that article is way off on the math.
For instance, if I apply the function from here to the Frugel-Horn I get a LF resonance of ~352.33 hz, and the length should be 150cm vs the ~98.46cm that results in the illustration above.
Attached Images
File Type: jpg FurgalHorn.jpg (30.3 KB, 66 views)

Last edited by prolow; 10th May 2018 at 03:31 AM.
  Reply With Quote
Old 10th May 2018, 03:37 AM   #10
planet10 is offline planet10  Canada
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Folded Back Loaded Horn Design
The FH-Lite is good to about 60 Hz or so.

Indeed the math in that article is only rudimentary. And there is theory and real-world. Real world is more complex. The decent modelers do much more complicated math, and have been adjusted/tweaked to match real-world builds.

Do note that the Frugel-Horn has at least a 4x multiplication of the mouth size because of the proximity to a wall/floor junction. And if the green line is supposed to represent the horn length how come it doesn’t wrap around th efold and reach to the end of th point?

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

Reply


Folded Back Loaded Horn DesignHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
back loaded horn design soundnovice Full Range 33 14th January 2018 02:16 AM
Looking for a medium footprint ~6" driver back loaded horn design hugz Full Range 7 18th August 2016 04:42 PM
Front loaded and back loaded horn DrWoofer.com Subwoofers 14 12th April 2016 08:32 PM
Combination of Back-loaded Horn and Fron loaded horn?! ARIYAHOOR Full Range 26 1st June 2012 09:20 PM
Back loaded horn design (help please) Puggie Full Range 3 23rd February 2006 01:08 PM


New To Site? Need Help?

All times are GMT. The time now is 07:25 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki