Back Loaded Horn (BLH) Full Range Speaker Build - 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 5th June 2011, 06:50 PM   #1
jgray is offline jgray  United States
diyAudio Member
 
Join Date: Sep 2010
Location: Chicago NW suburbs
Talking Back Loaded Horn (BLH) Full Range Speaker Build

I decided to tackle a full range speaker design and build to go with my 10W Class A amp. My goal was to create a floor standing speaker with good efficiency, keep the size reasonable, the cost down , and provide a fairly broad and flat frequency response.
I selected the Fostex Fe126en 4” driver, and decided to go with a BLH design to try and fill in the lower end. I came up with a design that measures approximately 7.5”Wx35”Hx15”D. I selected 19mm Baltic birch as the primary construction material, with a few internal baffles of MDF. This only required one 4’x8’ sheet of plywood, and a 2’x4’ piece of MDF.
I modeled the horn using HornResp, and the physical cabinet using Inventor 3D software.
I am happy with the outcome and think they sound great! It is hard to describe, but they sound really open and clean. Particularly with some piano music and female vocals you could swear they are in the room with you. Chamber music is also terrific with them. I find them to be plenty loud with my 10W amplifier.
Here is a picture of the completed speaker, with and without the grilles.
Attached Images
File Type: jpg IMG_0013 - Copy (600x800).jpg (314.8 KB, 553 views)
File Type: jpg IMG_0018 - Copy (600x800).jpg (284.7 KB, 504 views)
  Reply With Quote
Old 5th June 2011, 06:52 PM   #2
jgray is offline jgray  United States
diyAudio Member
 
Join Date: Sep 2010
Location: Chicago NW suburbs
Talking Measurement and Results

I measured the speakers using a homemade microphone based on the Panasonic WD-61A capsule which is supposed to be very flat.

It is coupled to a homemade preamp and then into the computer through a Behringer UCA202 USB soundcard. I used the Holm Impulse software to take the measurements. What a great tool! Here are the results.

The blue trace was taken right at the horn mouth. The brown trace was taken on axis with the driver at 12”, and the red trace is from 6’ away pointing at the driver, about 10 degrees off axis. I was surprised and pleased with how flat it was overall. The horn seems to fill in the lower frequencies nicely.
Attached Images
File Type: jpg Microphone (800x600).jpg (259.1 KB, 493 views)
File Type: jpg Frequency response.jpg (75.5 KB, 478 views)
  Reply With Quote
Old 5th June 2011, 06:54 PM   #3
jgray is offline jgray  United States
diyAudio Member
 
Join Date: Sep 2010
Location: Chicago NW suburbs
Talking Construction

Here is a side view before finishing or “stuffing.”

It was a challenge to get enough length folded into the fairly small box, considering the choice I made for the compression chamber geometry. I particularly wanted to try the angled piece behind the driver in the compression chamber in an attempt to reduce reflections from coming back through the driver. I wound up lining the compression chamber with a plush felt to further this. I also continued the felt on one side of the first half of the horn length to reduce standing waves across the interior 6” dimension. I used some fiberglass and poly batting in a few other places to further reduce highs through the horn.

Biscuit joining was used for the main structure and most of the baffles, although two of the smaller ones are just glued.
To finish them, I first used a sealer, then a stain, and then several coats of polyurethane.
If anyone wants to try these out, let me know and I will try to help. Be forewarned; all the cutting of the angles is a pain. I can post pdfs of the build plans I came up with in a separate post. They may have a few mistakes in them, but they are pretty close to “as-built”.

Thanks to everyone on this forum. I have learned a lot by lurking and reading what you have done. Hopefully my experience can help someone else.
Attached Images
File Type: jpg IMG_0001 (393x800) (393x800).jpg (180.2 KB, 487 views)
File Type: jpg IMG_0008 (800x600).jpg (324.6 KB, 249 views)
  Reply With Quote
Old 5th June 2011, 08:02 PM   #4
diyAudio Member
 
Join Date: Jan 2007
Fantastic -- congratulations! I would love to hear your further listening impressions as they break in.
  Reply With Quote
Old 5th June 2011, 09:50 PM   #5
diyAudio Member
 
malibujeff's Avatar
 
Join Date: Mar 2010
Location: Georgia
Nice. Thanks for posting the measurements.
  Reply With Quote
Old 5th June 2011, 10:22 PM   #6
diyAudio Member
 
Join Date: Oct 2004
Quote:
Originally Posted by jgray View Post
Here is a side view before finishing or “stuffing.”

It was a challenge to get enough length folded into the fairly small box, considering the choice I made for the compression chamber geometry. I particularly wanted to try the angled piece behind the driver in the compression chamber in an attempt to reduce reflections from coming back through the driver. I wound up lining the compression chamber with a plush felt to further this. I also continued the felt on one side of the first half of the horn length to reduce standing waves across the interior 6” dimension. I used some fiberglass and poly batting in a few other places to further reduce highs through the horn.

Biscuit joining was used for the main structure and most of the baffles, although two of the smaller ones are just glued.
To finish them, I first used a sealer, then a stain, and then several coats of polyurethane.
If anyone wants to try these out, let me know and I will try to help. Be forewarned; all the cutting of the angles is a pain. I can post pdfs of the build plans I came up with in a separate post. They may have a few mistakes in them, but they are pretty close to “as-built”.

Thanks to everyone on this forum. I have learned a lot by lurking and reading what you have done. Hopefully my experience can help someone else.
Great build! Thanks for posting your goal, build process, measurements, and conclusions. I especially liked how you stuck to the purist approach and went with a backloaded horn and no sub or super tweet. Not that easy given the diversity of options. Nothing like having real experience will full range drivers. Added bonus is that you are satisfied and happy with the speaker.
  Reply With Quote
Old 5th June 2011, 10:26 PM   #7
freddi is offline freddi  United States
diyAudio Member
 
freddi's Avatar
 
Join Date: Aug 2005
way KooL ! - nice work and nice measurements
  Reply With Quote
Old 5th June 2011, 10:34 PM   #8
diyAudio Member
 
vacuphile's Avatar
 
Join Date: Apr 2011
Location: Seaside
Great project and excellent measurements. Really surprised to see how flat the curve runs.
  Reply With Quote
Old 5th June 2011, 11:06 PM   #9
jgray is offline jgray  United States
diyAudio Member
 
Join Date: Sep 2010
Location: Chicago NW suburbs
Thanks for your comments everyone. I have to admit I was surprised at how well the curve flattened out. I guess it is good when the theory works out in practice. HornResp took me some time to figure out, but it is a powerful tool for gaining insight into how a speaker might behave. A big thank you to the developer for sharing that with the community!

As I have played around with listening and taking measurements, I have noticed that if I go say 30 or more degrees off axis I lose some of the highs. I have read of others observing this beaming effect, and guess it is pretty typical, but it was interesting to see the effect for myself.

I now find myself listening to every track critically for defects in the sound. Is this disease curable?
  Reply With Quote
Old 6th June 2011, 12:35 AM   #10
diyAudio Member
 
vacuphile's Avatar
 
Join Date: Apr 2011
Location: Seaside
Beaming is physics at work and you can't f*** with mother nature, as the saying goes amongst engineers. When the circumpherence of a sound radiating surface is > than the wavelenght of the frequency it is radiating, beaming sets in. Full range speaker manufacturers such as Fostex came up with solutions such as wizzer cones etc. to minimize the area radiating the high frequencies. but in the end, you can't win from the laws of physics.
  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
Best Full range drivers under £100 for a horn loaded cabinet? Bill poster Full Range 38 28th February 2011 11:42 PM
Help designing a Rear loaded full range horn for KEF sp1014 Naudio Full Range 9 22nd December 2010 09:17 PM
Full range in a front loaded horn Sella Full Range 20 17th October 2010 05:46 AM
Gedlee style speaker w/ back loaded horn, worthwhile? JZatopa Multi-Way 0 1st September 2010 04:21 AM
Front loaded and back loaded horn DrWoofer.com Subwoofers 0 3rd August 2007 06:55 PM


New To Site? Need Help?

All times are GMT. The time now is 04:47 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