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 28th May 2006, 07:07 PM   #1
rdf is offline rdf  Canada
diyAudio Member
 
rdf's Avatar
 
Join Date: Jun 2004
Location: big smoke
Default JX92S MLTL Alignment Sanity Check Request

I'm finally getting around to moving my drivers from an early prototype/break-in box to something permanent. The attached result is from a Mathcad run for a 48" JX92s MLTL using MJK's older ported-box sheet. It also uses the manufacturers driver parameters. The results look very good, maybe too good. The main concern is the short port is moving problems beyond the high frequency limit of the sim, though I recall MJK once mentioned the sims aren't accurate beyond a few octaves above resonance anyway. Opinions from experienced eyes would be greatly appreciated.
Attached Files
File Type: pdf jx25s 48 inch line v2.pdf (72.4 KB, 116 views)
__________________
Ears aren't microphones.
  Reply With Quote
Old 28th May 2006, 08:26 PM   #2
Dumbass is offline Dumbass  British Antarctic Territory
diyAudio Member
 
Join Date: Mar 2003
Location: British Antarctic Territory
That cross-sectional area seems small to me.

Have you looked at Greg's MLTL designs from the Jordan website? Both the 31" and 48" lines have been built with good results.
http://www.ejjordan.co.uk/diy/
  Reply With Quote
Old 28th May 2006, 08:56 PM   #3
rdf is offline rdf  Canada
diyAudio Member
 
rdf's Avatar
 
Join Date: Jun 2004
Location: big smoke
Thanks Dumbass (that feels so wrong!) You might be thinking of the MLTL sheet, this sim was done with ported-box sheet. As I recall it's essentially identical with the added ability to alter port location. In the port-box version cross sectional area is expressed as the product of two values. A long winded way of saying, it's 8 x 8, not 8.8. The x-sectional area is actually much larger than the GM designs on Jordan's site.
__________________
Ears aren't microphones.
  Reply With Quote
Old 28th May 2006, 09:05 PM   #4
diyAudio Member
 
Bob Brines's Avatar
 
Join Date: Jan 2003
Location: Hot Spring Village AR
Now that's a bazaar alignment! Try something more conventional like this MathCAD sim.

Bob
  Reply With Quote
Old 28th May 2006, 09:12 PM   #5
Dumbass is offline Dumbass  British Antarctic Territory
diyAudio Member
 
Join Date: Mar 2003
Location: British Antarctic Territory
Quote:
Originally posted by rdf
A long winded way of saying, it's 8 x 8, not 8.8.
Oops, my bad. Makes more sense now.
  Reply With Quote
Old 28th May 2006, 09:36 PM   #6
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Quote:
Originally posted by Bob Brines
Now that's a bazaar alignment! Try something more conventional like this MathCAD sim.

Bob
Greets!

Interesting the difference between the original WS Vs the latest one. Yours looks no less bazaar than rdf's done with it:

GM
Attached Images
File Type: jpg jx92s in bb's pipe.jpg (25.4 KB, 228 views)
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  Reply With Quote
Old 28th May 2006, 10:22 PM   #7
rdf is offline rdf  Canada
diyAudio Member
 
rdf's Avatar
 
Join Date: Jun 2004
Location: big smoke
Thanks all. It probably would help to explain some of the reasoning behind those numbers. Regarding the low frequency point, the old sheets (you already know) don't model floor reinforcement. I felt it was safe to assume enough room gain to make up the dB or two. It helped to keep displacement a bit lower around 32 Hz, the common notion of where common source material ends. I also wanted a big baffle to lower baffle step as far as possible, at the expense of more difficult (and expensive) construction for low cabinet talk for sure.

Regarding the driver near-centre placement, through hundreds of runs it consistently yielded the smoothest port response above fundamental resonance. Compare the port output at ~100 Hz between the 48" and 36" lines to see what I targeted.
__________________
Ears aren't microphones.
  Reply With Quote
Old 28th May 2006, 10:55 PM   #8
rdf is offline rdf  Canada
diyAudio Member
 
rdf's Avatar
 
Join Date: Jun 2004
Location: big smoke
Quote:
Originally posted by GM
Interesting the difference between the original WS Vs the latest one.
Ooops, I just caught the implication here. I was under the impression the basic physical models hadn't changed between the old sheets and the new. That's incorrect?
__________________
Ears aren't microphones.
  Reply With Quote
Old 29th May 2006, 01:03 AM   #9
diyAudio Member
 
Bob Brines's Avatar
 
Join Date: Jan 2003
Location: Hot Spring Village AR
Quote:
Originally posted by GM


Greets!

Interesting the difference between the original WS Vs the latest one. Yours looks no less bazaar than rdf's done with it:

GM
I wasn't talking about the final FR plot. The reason mine flattens out at the bottom is that I damped the port. Leave that port damping out and my model looks pretty much like yours. I was talking about the physical layout with the driver in the middle of the pipe and the port fully a foot up from the bottom.

Bob
  Reply With Quote
Old 29th May 2006, 01:44 AM   #10
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Greets!

OK, good to know. Still, I don't see the point in having so much Vb in a MLTL that you have to damp the port to flatten it. If you want vent harmonics to decay rapidly, use a positive (horn) taper of at least 10 deg.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  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
Time alignment sanity check quickshift Multi-Way 108 10th December 2008 11:56 AM


New To Site? Need Help?

All times are GMT. The time now is 03:59 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