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

30 Hz easy to build re-entrant horn
30 Hz easy to build re-entrant horn
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 14th January 2019, 05:18 PM   #1
cspieker is online now cspieker  United States
diyAudio Member
 
Join Date: Jul 2018
Location: South Dakota
Default 30 Hz easy to build re-entrant horn

I was hesitant to share this until I had a chance to hear and measure it, but I got it hooked up last night and all seems quiet and buzz free. Which surprises me.

I wanted to build a horn sub, but I'm obsessed with finding easier construction methods. I stumbled across a plastic footing form that flares from 10 inches to 22 with 1/8" wall thickness. So I got to work in hornresp modeling every possible configuration. Came up with a decent Sim for an 8" pvc, the flare, and a 30 concrete form. Nested reentrant style, with pipe and screws to reinforce it all. It's light and easy to build. I'll share the Sim and the measurements when I get home tonight. Hopefully you guys can help me perfect mk2. I know it's massive, but it goes low and is quite sensitive. Craig
Attached Images
File Type: jpg 20181215_084344.jpg (885.6 KB, 657 views)
  Reply With Quote
Old 14th January 2019, 06:22 PM   #2
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Cool! Looks like you're on to something since just tubes within tubes makes for a pretty good low tuned TL/high tuned horn.

Wasn't aware of tapered forms even though I've been involved peripherally with concrete plants, construction, etc., most of my life, yet in belated hindsight it seems reasonable they would exist.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  Reply With Quote
Old 14th January 2019, 10:34 PM   #3
cspieker is online now cspieker  United States
diyAudio Member
 
Join Date: Jul 2018
Location: South Dakota
Here is the 2 pi sim and the measured on ground plane at 2m. it was not calibrated spl.

Can anyone tell me why there is so much ripple in the response? I had read that it is caused by refelection back to the cone from the impedence mismatch between the horn mouth and free air, but why is this one affected so badly? I can easily eq it out, but I'd like to understand why it's there. Thanks!
Attached Images
File Type: jpg sub rew.jpg (63.8 KB, 622 views)
File Type: jpg horn sim 2 pi.jpg (53.5 KB, 578 views)
  Reply With Quote
Old 14th January 2019, 10:38 PM   #4
cspieker is online now cspieker  United States
diyAudio Member
 
Join Date: Jul 2018
Location: South Dakota
picture of it complete, although not cosmetically
Attached Images
File Type: jpg sub horn done.jpg (450.4 KB, 572 views)

Last edited by cspieker; 14th January 2019 at 10:42 PM. Reason: rotate pic
  Reply With Quote
Old 15th January 2019, 12:13 AM   #5
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Quote:
Originally Posted by cspieker View Post
Can anyone tell me why there is so much ripple in the response? I had read that it is caused by refelection back to the cone from the impedence mismatch between the horn mouth and free air, but why is this one affected so badly? I can easily eq it out, but I'd like to understand why it's there. Thanks!
Because there's an impedance mismatch at every [poor] termination back to the throat, modulating the driver plus the straight section of pipe adds extra set of harmonic reflections.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  Reply With Quote
Old 15th January 2019, 01:01 AM   #6
cspieker is online now cspieker  United States
diyAudio Member
 
Join Date: Jul 2018
Location: South Dakota
Thanks. Would this amount of ripple normally exclude a design as unfavorable? It seems like such a light easy to assemble horn would be a desirable design for certain circumstances.
  Reply With Quote
Old 15th January 2019, 06:34 AM   #7
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
You're welcome! Depends on room acoustics, etc., plus EQ is the norm in the < 80 Hz BW THX specs, though normally one uses damping at these joints to smooth a lot of this out, ditto around the mouth.

FWIW, the best woofer horn I've auditioned was a '50s era built in mono system 35 Hz BLH where they measured the room, then designed the horn to have peaks where the room dipped and vice versa. Really impressive even in the '60s before digital EQ, delay.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  Reply With Quote
Old 19th January 2019, 03:28 AM   #8
cspieker is online now cspieker  United States
diyAudio Member
 
Join Date: Jul 2018
Location: South Dakota
Anyone have any critiques of the design? I added below the input parameters, as well as the 2pi sim and 2pi measurements, also the 1pi sim and the 1pi max output and impulse. Is there anything that could be improved? Seems to me that if you put a couple of wheels on the bottom and a handle on the top, you have a very capable light pa setup. disadvantage is size, but for the max spl capable with only 500W, you'd be less likely to need multiples and huge amps. Any thoughts?
Attached Images
File Type: jpg horn sim 1 pi input.jpg (70.4 KB, 459 views)
File Type: jpg horn sim 1 pi.jpg (51.1 KB, 68 views)
File Type: jpg horn sim 1 pi max spl.jpg (54.8 KB, 62 views)
File Type: jpg horn sim 2 pi.jpg (53.5 KB, 39 views)
File Type: jpg sub rew.jpg (63.8 KB, 60 views)
File Type: jpg sub horn done.jpg (450.4 KB, 73 views)
  Reply With Quote
Old 19th January 2019, 04:30 AM   #9
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Which brand/model driver?

The sim's +/- ~3 dB is normally fine down low, but measures +/- ~ 5 dB, though measured is usually flatter than HR sims, so makes me wonder what I'm missing.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  Reply With Quote
Old 19th January 2019, 04:43 AM   #10
cspieker is online now cspieker  United States
diyAudio Member
 
Join Date: Jul 2018
Location: South Dakota
It's the dayton 15“ hf sub driver. I plugged it probably 6 or 8 drivers and it seemed the best fit. My ground plane measurements were only 50 feet from my house. Perhaps that affected the measurements?
  Reply With Quote

Reply


30 Hz easy to build re-entrant hornHide 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
Mid-bass horn (easy to build) carpenter Multi-Way 227 25th June 2017 04:13 AM
25-30hz tapped horn recommendation please... TB w8-740?? david45 Subwoofers 21 11th August 2014 05:29 PM
Horn With Extension To Under 30Hz McFinkle Subwoofers 22 12th November 2013 08:53 PM
An easy to build classic horn? dabbler Multi-Way 22 1st September 2011 08:01 AM
easy-to-build 3D-folded horn el`Ol Multi-Way 0 24th January 2009 09:57 AM


New To Site? Need Help?

All times are GMT. The time now is 02:10 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki