Open Baffle natural roll off? - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

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 12th November 2012, 05:56 PM   #1
diyAudio Member
 
Join Date: Jun 2011
Location: Kent
Default Open Baffle natural roll off?

I am currently building a pair of dipole speakers similar in design to the Orion.

I am using a Seas L22RNX/P and 10" XLS woofer in a baffle with a width of 300mm and height 1000mm and a MiniDSP for the EQ and x-overs.

I have simulated my baffle design in EDGE, it is my understanding that dipole speakers exhibit a natural roll-off of 12dB/octave.

After I have notched the dipole peak I am left with the dipole roll off and -6dB at 100hz.

Rather than correct for the dipole roll off, could I just let the midrange roll off naturally and apply low pass LR2 to the woofer at 100hz?
Or am I missing something vital?

Click the image to open in full size.
  Reply With Quote
Old 12th November 2012, 06:03 PM   #2
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

Yes you can. You could low pass lower down to extend the bass,
though your not going to get much SPL with 12" wide baffles.

BTW baffle loss is 6dB/octave not 12dB. Your extra roll-
off (not loss) is caused by using very low Qts drivers.
Your Edge sim only shows the baffle loss, 6dB/octave.

Final bass roll-off low down is 18dB/octave, 6dB due
to baffle loss and 12dB due to the drivers roll-off.

rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

Last edited by sreten; 12th November 2012 at 06:17 PM.
  Reply With Quote
Old 12th November 2012, 06:03 PM   #3
diyAudio Member
 
5th element's Avatar
 
Join Date: Oct 2002
Location: England
Cross posts with Sreten.

In the Orion LW uses a Linkwitz transform to compensate for the low Q woofer, then uses a 6dB/oct shelf to correct for the OB roll off.
__________________
What the hell are you screamin' for? Every five minutes there's a bomb or somethin'! I'm leavin! bzzzz!

Last edited by 5th element; 12th November 2012 at 06:05 PM.
  Reply With Quote
Old 12th November 2012, 06:06 PM   #4
diyAudio Member
 
Join Date: Jun 2011
Location: Kent
Opps, got my self in a muddle then.

The Peerless XLS 830452 woofer has a Q of 0.17, how would this affect it?
  Reply With Quote
Old 12th November 2012, 06:14 PM   #5
diyAudio Member
 
Join Date: Jun 2011
Location: Kent
What would you set as the target Q in a Linkwitz Transform? 0.5?
  Reply With Quote
Old 12th November 2012, 06:40 PM   #6
diyAudio Member
 
5th element's Avatar
 
Join Date: Oct 2002
Location: England
Quote:
Originally Posted by rich31td View Post
What would you set as the target Q in a Linkwitz Transform? 0.5?
It depends on what Q your're happy with, but people usually choose between 0.5-0.7.

Note here that the XLS drivers have a Q of something like 0.18 and a resonance close to 20Hz. These are the numbers you will use when setting the parameters for the LT and you will then pick the desired target fs and Q for it to equalise towards.

If you are wanting the main panels to give you extension down to say 40Hz, then picking a target Q of 0.7 + a target fs of 35Hz would be a good idea. If you combine this with a high pass with a Q of 0.7 and a corner frequency of 35Hz, then you will end up with an overall roll of centred on 35Hz with a Q of 0.5.

Do bare in mind that the XLS' fs and Qts will rise by a small amount when mounted on/in the baffle/frame.
__________________
What the hell are you screamin' for? Every five minutes there's a bomb or somethin'! I'm leavin! bzzzz!
  Reply With Quote
Old 12th November 2012, 06:44 PM   #7
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

Crossed posts.

Rereading your post I've misunderstood your post and no you can't.

You need to model driver responses as well as the baffle loss.

Look at : https://sites.google.com/site/undefi...diy-sunflowers

A Qts of 0.17 sub in a 12" wide open baffle is a disaster area in all respects.
Baffle loss at 50Hz will turn a 10" driver into no better than a boxed 3" SPL.
Huge amounts of boost and power are required to produce piffling SPL.

rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow

Last edited by sreten; 12th November 2012 at 06:59 PM.
  Reply With Quote
Old 12th November 2012, 06:46 PM   #8
Davey is online now Davey  United States
diyAudio Member
 
Join Date: Dec 2001
Location: Bremerton, WA.
Rich,

You can target whatever Q you desire with available EQ tools, like the Linkwitz Transform. 0.5 would probably be an excellent target.

FYI, the Orion system does not use a Linkwitz Transform anywhere in the design. Q correction of the woofers is handled by a simple 6db/octave shelving filter.

Cheers,

Dave.
  Reply With Quote
Old 12th November 2012, 06:55 PM   #9
diyAudio Member
 
5th element's Avatar
 
Join Date: Oct 2002
Location: England
You can't handle Q correction with a simple shelving filter, I am sure I've seen a schematic or block diagram for the Orion that shows an LT on the woofers.
__________________
What the hell are you screamin' for? Every five minutes there's a bomb or somethin'! I'm leavin! bzzzz!
  Reply With Quote
Old 12th November 2012, 07:15 PM   #10
diyAudio Member
 
Join Date: Jun 2011
Location: Kent
I forgot to mention, the 10" woofer will be mounted in an H-frame similar dimensions as the Orion.

I think I need to get outside and measure the responce of the baffle/driver and work out the shelf filter for the midrange and H-frame.

So there is no problem in using LT on the woofer then to achive a target of 35hz, Q=0.5 and a 6db/octave correction?
  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
The reason why open baffle have a bass roll-off aarvin2 Full Range 24 21st May 2013 11:22 PM
Upwards aligned open baffle? ( pop box meets open baffle ) OllBoll Full Range 3 28th March 2011 02:00 AM
FR125s no baffle roll off Foxx510 Full Range 2 3rd February 2008 10:54 PM
Natural roll-off or cross-over: what's best? Klimon Full Range 2 6th February 2006 07:41 PM
Help me find a woofer that has a natural roll-off and may not need a x-over... Greggo Multi-Way 23 2nd April 2004 04:18 PM


New To Site? Need Help?

All times are GMT. The time now is 03:43 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