TH-18 Flat to 35hz! (Xoc1's design) - Page 102 - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

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 22nd September 2012, 02:38 AM   #1011
diyAudio Member
 
Join Date: Dec 2009
Location: California
Does Hornresp show a more exaggerated dip? Just asking since HR exaggerates peaks & dips and I didn't know if akabak did the same.
(I've been crossing over at ~88Hz - so, no issue for me)

The driver I'm using (18SW100) results in a higher f3, unfortunately. Not sure if a few inches here or there would get a little bit of that extension back without sacrificing output.

Will we have any issues (phasing, cancellations, etc) running a group of cabs that have different cone volume correction methods installed?
  Reply With Quote
Old 22nd September 2012, 03:13 AM   #1012
Djim is offline Djim  Netherlands
diyAudio Member
 
Join Date: Dec 2009
Location: 'Ollanda
Quote:
Originally Posted by Xoc1 View Post
I'm a bit concerned about the 110Hz dip to 96db
Hi Martin,

Try to trade the energy of the 82Hz bumb for the 110Hz dip by using their quarter wavelength to determine their position within the horn. My rough guess is that the vertical board (that is connected with the top-panel) needs to be tilted over (clockwise) and make it parallel to the board on its left.
  Reply With Quote
Old 22nd September 2012, 05:58 AM   #1013
Djim is offline Djim  Netherlands
diyAudio Member
 
Join Date: Dec 2009
Location: 'Ollanda
Lol, that was a huge calculation mistake so forget my earlier panel suggestion... (some progs need dots where we use comma's in Holland)

Anyway, did a Hornresp model based on a total volume 375,88 Litres of your Sketch. So S4 has become smaller to compensate for the correct total volume. Their seems to be a big difference between Akabak and HornResp in the outcome at the First System Resonance.

Click the image to open in full size.
  Reply With Quote
Old 22nd September 2012, 08:21 AM   #1014
Djim is offline Djim  Netherlands
diyAudio Member
 
Join Date: Dec 2009
Location: 'Ollanda
Small update, corrected the system volume to 362,3 because of the two corners and driver plus changed the expansion to expo.

Click the image to open in full size.

Last edited by Djim; 22nd September 2012 at 08:24 AM.
  Reply With Quote
Old 22nd September 2012, 01:51 PM   #1015
Xoc1 is offline Xoc1  United Kingdom
diyAudio Member
 
Xoc1's Avatar
 
Join Date: Nov 2008
Location: Devon UK
Hi All
Hornresp is so useful but there are always compromises that need to be made for the sim model.
Attached is one of my alternative HR sims
Volume of the unfolded horn layout is 345.7 litres not allowing for the bracing.
Volume of sim is 336 so not unrealistic - I do feel uneasy about sims that exaggerate the internal volume of a speaker cab.
Where it gets complicated is having to run 2 sims to try to understand what is happening with the various sections of the horn.
Regards
Martin
Attached Images
File Type: jpg TH18MK1-HR.jpg (153.3 KB, 548 views)
  Reply With Quote
Old 22nd September 2012, 05:36 PM   #1016
tb46 is offline tb46  United States
diyAudio Member
 
Join Date: Jan 2006
Location: Texas
Hi Martin,

Another great piece of work, Posts 1010/1015

I noticed that the S1 duct height dimension 147.4mm x 535 mm internal width result in 788.59 cm^2, the Hornresp Input says 933.04 cm^2 (in the Hornresp simulation this doesn't much matter, but only one should be correct).

I think you are on the right path with using AkAbak for this one, Hornresp just doesn't seem to get us there. I tried a short L23 together with an arbitrarily choosen S4 (to get to your layout volume of 345.7 L). Looks very much like what Djim came up with?

Regards,
Attached Images
File Type: jpg modified_Input.jpg (35.4 KB, 519 views)
File Type: jpg modified_SPL.jpg (30.3 KB, 499 views)
__________________
Oliver

Last edited by tb46; 22nd September 2012 at 05:39 PM.
  Reply With Quote
Old 23rd September 2012, 01:28 AM   #1017
NEO Dan is offline NEO Dan  United States
diyAudio Member
 
NEO Dan's Avatar
 
Join Date: Jun 2008
Location: N.E. Ohio
I'm really curious as to where fudging S2 via an inflated cone correction became a good idea? The 18SW115 is really not going to make it to 60mm p-p without dammage, in fact it is hard to drive to 40mm p-p, and that's with HUGE amounts of power.
__________________
Regards,
Dan
  Reply With Quote
Old 23rd September 2012, 02:15 AM   #1018
diyAudio Member
 
noSmoking's Avatar
 
Join Date: May 2010
Location: Texas
Howdie,
Made the lower ring change to my box and ran some tests, I see nice smooth plots from you guys ,mine are not anyone care to interpet,
Thanks,
NS
Attached Images
File Type: jpg spl and phase lower rings in.jpg (104.3 KB, 105 views)
File Type: jpg rta swept to 200 rings in.jpg (76.7 KB, 78 views)
  Reply With Quote
Old 23rd September 2012, 02:19 AM   #1019
djk is offline djk
diyAudio Member
 
djk's Avatar
 
Join Date: Feb 2001
Location: USA
Dynamic off-set is what mechanically damages woofers.

The Crown MA5000vz has a double-integrator (U104A, B) to try and help off-set with issues.

Some program material causes problems Power Amplifier Clipping, clipping an amplifier can cause real problems (the ESP note also discusses non-clipped program material issues).

5.2.4 Loudspeaker Offset Integration
Loudspeaker Offset Integration (LOI) circuits use double
integrating filters in the amplifier’s feedback circuitry to
protect loudspeakers in several different ways. First, they
center asymmetrical audio waveforms that cause off-center
woofer cone movement. Off-center cone movement
increases loudspeaker heating and distortion while reducing
the loudspeaker’s power handling ability. Second, LOI
filters unwanted DC and subsonic frequencies using a
third-order Butterworth filter with a 35 Hz corner
frequency. Third, LOI filters unwanted ultrasonic frequencies
(RF) that can cause tweeter burnout using a secondorder
Bessel filter with a 50 kHz corner frequency.
__________________
Candidates for the Darwin Award should not read this author.
  Reply With Quote
Old 23rd September 2012, 03:08 AM   #1020
Djim is offline Djim  Netherlands
diyAudio Member
 
Join Date: Dec 2009
Location: 'Ollanda
Quote:
Originally Posted by NEO Dan View Post
I'm really curious as to where fudging S2 via an inflated cone correction became a good idea? The 18SW115 is really not going to make it to 60mm p-p without dammage, in fact it is hard to drive to 40mm p-p, and that's with HUGE amounts of power.
Hi Dan,

When a driver is pushed to its limits it will start producing asymmetric forces. For the suspension that is usually around the Fs of the driver, for the motor that is usually when the BL drops significant, or when the system increases the induction below the Fs of the driver. Tapped Horns and horns in general have the habit to generate all three factors.

To suppress these asymmetric forces you can do several things, Push-Pull, increasing compression at the cone (as long it is equally distributed from the centre) and using capable amplifiers like Djk already explained.

In my view, the "V" was developed for this reason just like it was used in old horns decades ago. The more capable the driver (like the B&C 18SW115 for instance) the less compensation is needed to deal with asymmetric forces. But the reality is that most people don’t have such driver and still want to be able to get the maximum out of theirs.

The "V" as used in the Xoc1-TH18-MkI is not much different as adding a restricted throat but with the convenience of allowing to increase the horn-path. Cone correction alone does not help in decreasing asymmetric forces.
  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
18 inch labhorn design. mulletdude Subwoofers 23 27th November 2013 09:43 PM
Ciare 18 bass horn design soundhead Subwoofers 5 22nd September 2013 09:33 AM
2 18 bass design simpleacoustic Subwoofers 101 15th May 2011 10:22 AM
I want my Avalanche 18 to go flat to 15hz thadman Subwoofers 10 11th November 2006 03:54 AM
Looking for suggestions on a 1300W Dual 18 sub design. mjcohen Subwoofers 5 21st December 2004 08:38 AM


New To Site? Need Help?

All times are GMT. The time now is 08:57 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